CN111449130B - Green preservative for fresh-cut Nanguo pear - Google Patents

Green preservative for fresh-cut Nanguo pear Download PDF

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CN111449130B
CN111449130B CN202010338910.6A CN202010338910A CN111449130B CN 111449130 B CN111449130 B CN 111449130B CN 202010338910 A CN202010338910 A CN 202010338910A CN 111449130 B CN111449130 B CN 111449130B
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parts
solution
fresh
chitosan
preservative
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CN111449130A (en
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吕静祎
丁思杨
葛永红
徐冬乐
励建荣
李灿婴
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Bohai University
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    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/153—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of liquids or solids
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/153—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of liquids or solids
    • A23B7/154—Organic compounds; Microorganisms; Enzymes
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/153—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of liquids or solids
    • A23B7/157—Inorganic compounds
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/16—Coating with a protective layer; Compositions or apparatus therefor
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
    • A23V2002/00—Food compositions, function of food ingredients or processes for food or foodstuffs
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
    • Y02A40/90—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in food processing or handling, e.g. food conservation

Abstract

The invention relates to a fruit storage and preservation technology, and discloses a fresh-cut Nanguo pear green preservative aiming at the problem that the components of the preservative and the optimal preservation hardness of Nanguo pears are not disclosed in the prior art, wherein the preservative comprises a preservative solution and a film-forming agent, and the preservative solution comprises the following components in parts by mass (100 parts by mass): 0.4-0.6 part of watermelon peel extract, 1-1.2 parts of mangosteen peel extract, 0.8-1.2 parts of pomegranate peel extract, 3.8-4.2 parts of chrysanthemum extract, 0.5-0.8 part of resveratrol, 1.4-1.6 parts of citric acid, 1.8-2 parts of calcium chloride and the balance of water; the film forming agent comprises the following components in parts by mass 100: 30-40 parts of modified whey protein, 10-12 parts of chitosan, 0.2-0.5 part of alanine and the balance of water. The green preservative can maintain the contents of titratable acid, vc and soluble solid matters in the Nanguo pear slices, slow down the weight loss rate, effectively delay the occurrence of browning of the Nanguo pears and maintain the storage quality of the fresh-cut Nanguo pears.

Description

Green preservative for fresh-cut Nanguo pear
Technical Field
The invention relates to a fruit storage and preservation technology, in particular to a green preservative for fresh-cut Nanguo pears.
Background
The Nanguo pear belongs to the autumn pear in the pear genus of the subfamily of the Rosaceae, is produced in the Liaodong and other places in the northeast of China, and belongs to a special pear variety in China. The Nanguo pear has high nutritive value, and calcium, iron, zinc and other elements in the Nanguo pear are higher than those in other fruits, so that the Nanguo pear can supplement nutrition and water required by human bodies. The ripe Nanguo pear is fragrant, sweet and delicious, has special wine aroma and is popular with people, so that the Nanguo pear is called as the king of pear. However, the Nanguo pear has short storage time and is easy to soften, and browning is easy to occur after the Nanguo pear is cut, so that the economic value of the Nanguo pear is influenced, and the industrial development of the Nanguo pear is restricted.
Fresh-cut fruits serve as a new industry, and are rapidly developed in China in recent years, so that the fresh-cut fruits have wide market prospects. However, the tissue structure of the fresh-cut fruits and vegetables is damaged, so that browning and microbial infection are easy to occur, nutrient loss is caused, the quality of the fruits and vegetables is difficult to maintain, and the shelf life of the fruits and vegetables is greatly shortened. The south fruit pears picked in the commercial picking period are hard in texture and sour and astringent in taste, the special bouquet of the south fruit pears is not shown, the optimal edible maturity can be achieved only through storage for a period of time, at the moment, the south fruit pears are extremely good in flavor, moderate in hardness and suitable for fresh cutting, and then the south fruit pears are aged and softened quickly and are easy to rot and deteriorate. The hardness is an important index for reflecting the storage stability of the picked fruits, directly reflects the softening degree of the fruits, has a close correlation between the reduction rate and the storage life, can know the quality change characteristics of the fruits by measuring the hardness of the picked fruits, and is also an important basis for judging whether the fruits can be fresh cut or not. Therefore, the optimal maturity (hardness) range suitable for fresh cutting of the Nanguo pears is found, and the effective preservation of the Nanguo pears is of great significance.
The patent number CN200610045906.0 with the patent name of Nanguo pear storage fresh-keeping anti-browning technology discloses a Nanguo pear storage fresh-keeping anti-browning technology, belonging to the fruit storage fresh-keeping technology. The technology comprises the steps of harvest of the Nanguo pears at the right time, pre-ripening before storage, preservative treatment before storage of the Nanguo pears and storage period management. The invention is beneficial to the fruit ripening because the Nanguo pear is harvested at the right time, and prevents physiological diseases and pericarp browning in the later storage period. The Nanguo pears are pre-ripened before storage and then put in storage, and the storage effect is good. The preservative treatment before storage can inhibit browning of the afterskins of the south fruit pears in the later storage period and after the south fruit pears are delivered out of the warehouse. The storage period management can provide a temperature, humidity and ventilation environment suitable for storing the Nanguo pears.
The patent mainly describes the storage process and storage conditions of the Nanguo pears, the used preservative is stored for the Nanguo pears, the synthesis components and the method of the preservative are not described in detail, and the optimal preservation hardness range of the Nanguo pears is not disclosed.
Disclosure of Invention
The invention discloses a fresh-cut Nanguo pear green preservative, aiming at overcoming the problems of synthetic components of the undisclosed preservative and the optimal preservation hardness of Nanguo pears in the prior art, and the hardness of the Nanguo pears obtained by the invention is 3-7kg/cm 2 The range of Nanguo pears has better quality and better flavor and mouthfeel; meanwhile, the green preservative synthesized by the invention can well maintain the contents of titratable acid, VC and soluble solid matters in the Nanguo pear slices, slow down the rate of weight loss, effectively delay the occurrence of browning of the Nanguo pears, maintain the storage quality of the fresh-cut Nanguo pears, prolong the storage time of the fresh-cut Nanguo pears and greatly improve the commercial value of the Nanguo pears.
In order to achieve the purpose, the invention adopts the following technical scheme:
the fresh-cut south fruit pear green preservative comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.4-0.6 part of watermelon peel extract, 1-1.2 parts of mangosteen peel extract, 0.8-1.2 parts of pomegranate peel extract, 3.8-4.2 parts of chrysanthemum extract, 0.5-0.8 part of resveratrol, 1.4-1.6 parts of citric acid, 1.8-2 parts of calcium chloride and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 30-40 parts of modified whey protein, 10-12 parts of chitosan, 0.2-0.5 part of alanine and the balance of water.
The preservative has good antioxidant and anti-browning effects, the film-forming agent has water-retaining and antibacterial effects, and the quality of the fresh-cut pear blocks can be more effectively maintained by the double-coating mode.
Preferably, the fresh-keeping film forming agent is a trans-lactoalbumin-oligochitosan membrane blending solution.
Preferably, the fresh-keeping film forming agent comprises the following preparation steps:
1) Transferring whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:10-12, magnetically stirring for 30-35min, then carrying out water bath for 30-40min at 85-90 ℃ and continuously stirring, cooling, adding 60-65% by mass of glycerol, stirring for 30-35min, then adding transglutaminase to enable the enzyme-substrate concentration ratio to be 0.04-0.06, carrying out water bath culture, taking out, heating in water bath at 80-85 ℃ for 5-8min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 10-15min, and keeping for later use;
2) Preparing chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.1-0.12mol/L acetic acid solution, mechanically stirring for 1-1.2h until the chitosan is completely dissolved to obtain chitosan solution, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:10-12, reacting for 8-10h at 50-55 deg.C and pH 5-5.2 to obtain oligomeric chitosan, boiling the obtained reaction solution in boiling water bath for 5-8min to inactivate enzyme, vacuum filtering to remove enzyme, adjusting pH to neutral with NaOH solution, and reserving;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (3) mixing the transformed whey protein and the chitosan oligosaccharide according to the mass ratio of 3-4:1, adding alanine, stirring for 25-30min at 30-45 ℃, adjusting the pH to be neutral by using 1.0-1.2mol/L HCl and 1.0-1.2mol/L NaOH, cooling to room temperature, adding water to constant volume, stirring for 30-40min again, and vacuumizing and degassing to obtain the finished product.
The whey protein solution can form heat-denatured irreversible gel, and the whey protein has good film-forming property due to good gel-forming property. The functional characteristics of the whey protein are not perfect, such as sensitization, structural defects of beta-lactoglobulin and the like, the functional characteristics of the whey protein can be further improved or improved by moderate modification, and the whey protein is hydrolyzed by enzyme, so that the intramolecular or intermolecular crosslinking effect of the whey protein can be enhanced, and the functional characteristics of the whey protein are improved. Such as partial hydrolysis of whey protein, can reduce the viscosity of the solution and thereby increase its solubility.
Due to the hydrogen bonding force in chitosan molecules and the crystal structure thereof, the water solubility of the chitosan is poor. The degraded chitosan molecules have a large amount of strong polar group light groups and amino groups, so that hydrogen bonds are easily formed, the water solubility is greatly improved, the moisture absorption and retention performance is greatly improved, and meanwhile, the chitosan oligosaccharide has better antibacterial and bacteriostatic effects; based on the catalytic property of transglutaminase and the glycosylation of chitosan oligosaccharide, the whey protein is modified by an enzyme method by utilizing the advantage of a large amount of active amino groups of the chitosan oligosaccharide, so that the functional property of the whey protein is improved, and the rheological property, the thermal stability, the emulsibility, the solubility, the fluorescence and other whey protein-chitosan covalent complexes improve the emulsification stability of the whey protein and the solubility thereof near the isoelectric point.
The composite film forms a layer of 'polymer protective film' with certain barrier property on the surface of fruits and vegetables, reduces various physiological activities of the fruits, and even if the fruits are temporarily in a dormant state, the respiration intensity of the fruits can be reduced by storing the fruits under the condition, and CO generated by respiration can be slowed down 2 The outward diffusion rate plays a role in modified atmosphere preservation, the rotting and deterioration degree of the pulp is reduced to a certain degree, the surface hardness and luster of the fruits are improved, and meanwhile, the loss of various nutritional ingredients in the fruits is reduced, so that a good preservation effect is achieved.
Preferably, the water bath culture conditions in the step 1) are that the pH value is adjusted to 7.4-7.6, and the water bath shaking culture is carried out for 70-75min at the temperature of 60-65 ℃.
The pH value has great influence on the surface charge of the protein, influences the interaction of the protein and the performance of a membrane, and researches show that the optimal pH value of the transglutaminase is 6.0-8.0. A single-factor experiment shows that the oxygen transmission rate and the water vapor transmission rate of the composite membrane are optimized when the pH value is 7.4-7.6. Heat treatment also has some effect on the structure of whey protein and studies have shown that the effect on the solubility and foamability of whey protein is reversible at a treatment temperature of 60 ℃. Therefore, the experimental design is that the hydrolysis degree of the lactalbumin is highest and the comprehensive performance of the composite membrane is best when the whey protein is cultured in a water bath oscillation mode at the pH value of 7.4-7.6 and the temperature of 60-65 ℃.
Preferably, the molecular weight of the chitosan oligosaccharide obtained in step 2) is 3000-3200.
Due to the hydrogen bonding force in chitosan molecules and the crystal structure thereof, the water solubility of the chitosan is poor. A large number of strong polar groups of hydroxyl and amino exist in degraded chitosan molecules, hydrogen bonds are easily formed, water solubility is greatly improved, moisture absorption and retention performances are greatly improved, and the pH value stability in an aqueous solution is enhanced. Along with the reduction of the molecular weight, the bacteriostatic activity of the chitosan is enhanced, the diameter of a bacteriostatic circle is increased, and the minimum bacteriostatic concentration is reduced. Research shows that when the molecular weight is 3000-3200, the chitosan oligosaccharide has the best moisture absorption and retention capacity, when the molecular weight is 5000, each index only reaches half of that when the molecular weight is 3000, and the molecular weight is lower than 3000, so that the experiment difficulty is increased.
Preferably, the concentration of the NaOH solution in the step 2) is 1-1.2mol/L.
If the concentration is too high, the addition amount is small, the pH value is still easy to exceed a fixed pH value, and if the concentration is too low, the volume of the NaOH solution to be added is too large.
Preferably, the vacuum degree of the vacuum degassing in the step 3) is 90-95Pa.
The vacuum degree is too high, which is not beneficial to the escape of gas, and the vacuum degree is too low, which is easy to destroy the effective components in the preservative.
Preferably, the green preservative solution comprises the following preparation steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-80 deg.C to-75 deg.C for 22-24h, freeze drying for 20-24h, grinding, weighing watermelon peel powder, adding 70-72% ethanol solution, and mixing at a solid-liquid mass ratio of 1:18-20, extracting under reflux for 48-50min, centrifuging, recovering ethanol, and concentrating to obtain soft extract;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 5-6h, reflux extracting for 2-3 times, each time for 1-1.2h, adding water 16-20 times of flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.03-1.05, adding ethanol to reach alcohol concentration of 63-65%, stirring, standing for 10-12h, filtering, recovering ethanol, and concentrating flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with aseptic prop, cutting into small pieces, placing in a refrigerator at-80 deg.C to-75 deg.C for 22-24h, freeze drying for 23-25h, grinding, weighing mangosteen bark powder, placing in a beaker, adding 80-82% ethanol solution, water bathing for 30-40min, adding 78-80% ethanol solution, water bathing for 30-35min, recovering ethanol, and concentrating to obtain thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-80 deg.C to-75 deg.C for 20-24h, freeze drying for 20-24h, grinding, weighing pericarpium Granati powder, placing in a container, adding 60-62% ethanol solution, and mixing at a solid-to-liquid ratio of 1:38-40, ultrasonic extracting for 35-40min, recovering ethanol, and concentrating to obtain soft extract;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.4-0.5ul/L, adding citric acid and calcium chloride, mixing, and controlling solid-to-liquid ratio at 1:10-12, putting into water bath at 55-60 ℃, stirring for 30-35min, ultrasonically dispersing for 20-30min, homogenizing for 10-15min, decompressing and defoaming for 4-5h, and refrigerating and storing at 4-6 ℃.
People pay more and more attention to greenness and nature, the food raw materials and ingredients are expected to come from natural plants, and the watermelon peel extract, the pomegranate peel extract and the mangosteen peel extract contain phenols and flavonoid substances and have good antioxidant and anti-browning effects; the wild chrysanthemum extract has good antibacterial effect; resveratrol is a plant endogenous phenolic substance and also has strong antioxidant effect. The food additives, namely citric acid and calcium chloride, can effectively prevent browning and keep slice hardness, and the content of food additive components in the composite liquid is lower than the national standard and lower than that of other patents; the extracts are mixed, and resveratrol, citric acid solution and calcium chloride solution are added to have good and obvious inhibiting effect on the browning of the cut south fruit pears, and the composite preservative solution prepared according to the concentration is used for coating, so that the original flavor of the south fruit pears is not influenced after treatment, the browning phenomenon of the fresh-cut south fruit pears can be effectively delayed, and the storage period is prolonged.
Preferably, the mass contents of citric acid and calcium chloride in the step (5) are 1.2-1.5% and 1.8-2%, respectively.
The application of the green preservative for the fresh-cut south fruit pears comprises the following use steps:
(A) Finding the optimal flavor hardness range: comprehensive evaluation of sense organ and taste is carried out on the Nanguo pear, and the hardness range of the good flavor is 3-7kg/cm 2 ；
(B) Slicing and preserving: removing core of Nanguo pear, and cutting into 6 × 4 × 2cm 3 The wedge-shaped pear blocks are placed into the green preservative solution to be soaked for 2-5min, then taken out, aired for 1-2min, and excess water is wiped off by absorbent gauze; soaking the pear blocks in the fresh-keeping film-forming agent for 1-3min, and drying;
(C) And (3) storage: wiping off water with absorbent gauze, packaging into PE self-sealing bag, and storing in 3-5 deg.C thermostat.
The south fruit pears picked in the commercial picking period are hard in texture and sour and astringent in taste, the special bouquet of the south fruit pears is not shown, the optimal edible maturity can be achieved only through storage for a period of time, at the moment, the south fruit pears are extremely good in flavor, moderate in hardness and suitable for fresh cutting, and then the south fruit pears are aged and softened quickly and are easy to rot and deteriorate. The hardness is an important index for reflecting the storage stability of the picked fruits, directly reflects the softening degree of the fruits, has a close correlation between the reduction rate and the storage life, can know the quality change characteristics of the fruits by measuring the hardness of the picked fruits, and is also an important basis for judging whether the fruits can be fresh cut or not. Therefore, the optimal maturity (hardness) range suitable for fresh cutting of the south fruit pears is found, the south fruit pears are cut into blocks within the hardness range, and the green preservative solution and the preservative film-forming agent are coated on the south fruit pears, so that the storage quality of the fresh-cut south fruit pears is maintained, and the shelf life of the fresh-cut south fruit pears is prolonged. The formula of the fresh-keeping liquid is food-grade raw materials, the fresh-cut fruits and vegetables can be directly eaten after being soaked in the fresh-keeping liquid, the taste of the fresh-cut fruits and vegetables cannot be adversely affected, the storage and fresh-keeping period of the south fruit pears is greatly prolonged, the sale way of the south fruit pears can be increased, and the industrial economic development is promoted.
Therefore, the invention has the following beneficial effects:
(1) The hardness of the Nanguo pear is 3-7kg/cm 2 The range of the Nanguo pears has good quality and good flavor and taste, the cut Nanguo pears can be directly used in the processing fields of fruit particle yoghourt, fruit particle jelly, cans and the like without seasoning, the storage quality of the fresh-cut Nanguo pears is ensured, and the shelf life of the fresh-cut Nanguo pears is prolonged;
(2) The green preservative for the fresh-cut south fruit pears is provided, and comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution is prepared from natural plants, is green and environment-friendly, contains phenols and flavonoids, and has a good antioxidant effect; the fresh-keeping film-forming agent can well delay the water loss of the fresh-cut Nanguo pear and reduce the combination chance of the fresh-cut Nanguo pear and oxygen in the air, and the fresh-keeping film-forming agent and the fresh-keeping agent have a synergistic effect, so that a better fresh-keeping effect can be achieved;
(3) The green preservative synthesized by the invention can well maintain the contents of titratable acid, VC and soluble solid matters in the Nanguo pear slices, slow down the weight loss rate, effectively delay the occurrence of browning of the Nanguo pears, maintain the storage quality of the fresh-cut Nanguo pears, prolong the storage time of the fresh-cut Nanguo pears and greatly improve the commercial value of the Nanguo pears.
Drawings
FIG. 1 is a graph showing the change of performance index of Nanguo pear
Detailed Description
The invention is further described with reference to specific embodiments.
Example 1
The fresh-cut Nanguo pear green preservative comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.4 part of watermelon peel extract, 1 part of mangosteen peel extract, 0.8 part of pomegranate peel extract, 3.8 parts of chrysanthemum extract, 0.5 part of resveratrol, 1.4 parts of citric acid, 1.8 parts of calcium chloride and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 30 parts of modified whey protein, 10 parts of chitosan, 0.2 part of alanine and the balance of water.
The fresh-keeping film forming agent is a transfer whey protein-oligochitosan blended film liquid, and the preparation steps of the fresh-keeping film forming agent are as follows:
1) Transferring whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:10, magnetically stirring for 30min, then carrying out water bath at 85 ℃ for 30min and continuously stirring, cooling, adding 60% glycerol by mass, stirring for 30min, then adding transglutaminase to enable the enzyme-substrate concentration ratio to be 0.04, adjusting the pH value to be 7.4, carrying out water bath oscillation culture at 60 ℃ for 70min, taking out, heating in water bath at 80 ℃ for 5min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 10min, and keeping for later use;
2) Preparing the chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.1mol/L acetic acid solution, mechanically stirring for 1h until the chitosan is completely dissolved to obtain low chitosan solution with the molecular weight of 3000-3200, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:10, reacting for 8 hours at 50 ℃ and under the condition of pH value of 5 to obtain oligomeric chitosan, boiling the obtained reaction liquid in boiling water bath for 5 minutes to inactivate enzyme, carrying out vacuum filtration to remove the enzyme, adjusting the pH value to be neutral by using NaOH solution with the concentration of 2mol/L, and reserving for later use;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (2) mixing the converted whey protein and the chitosan oligomer according to the mass ratio of 3:1, adding alanine, stirring for 25min at 30 ℃, adjusting the pH to be neutral by using 1.0mol/L HCl and 1.0mol/L NaOH, cooling to room temperature, adding water to constant volume, stirring for 30min again, vacuumizing and degassing to obtain a finished product with the vacuum degree of 90 Pa.
The preparation method of the green preservative solution comprises the following steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a-80 deg.C refrigerator for 22h, freeze-drying for 20h, grinding, weighing watermelon peel powder, adding 70% ethanol solution, and mixing solid and liquid at a solid-liquid mass ratio of 1:18, refluxing and extracting for 48min, centrifuging, recovering ethanol, and concentrating to obtain a thick paste;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 5 hr, reflux extracting for 2 times, each time for 1 hr, adding water 16 times of flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.03, adding ethanol to reach ethanol concentration of 63%, stirring, standing for 10 hr, filtering, recovering ethanol, and concentrating flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with sterile prop, cutting into small pieces, placing in a refrigerator at-80 deg.C for 22h, freeze-drying for 23h, grinding, weighing mangosteen bark powder in a beaker, adding 80% ethanol solution 250mL, water-bathing for 30min, adding 78% ethanol solution 250mL, recovering ethanol after water-bathing for 30min, and concentrating into thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp by using a sterile prop, cutting into small pieces, placing in a refrigerator at the temperature of minus 80 ℃ for 20h, freeze-drying for 20h, grinding again, weighing pomegranate peel powder in a container, adding a 60% ethanol solution, and mixing the solid and the liquid according to the solid-to-liquid ratio of 1:38, ultrasonically extracting for 35min, recovering ethanol, and concentrating to obtain a thick paste;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.4ul/L, adding citric acid and calcium chloride with mass content of 1.2% and 1.8%, respectively, mixing well, and controlling solid-to-liquid ratio at 1:10, stirring in 55 ℃ water bath for 30min, ultrasonically dispersing for 20min, homogenizing for 10min, decompressing and defoaming for 4h, and refrigerating and storing at 4 ℃.
The application of the green preservative for the fresh-cut south fruit pears comprises the following steps:
(A) Finding the optimal flavor hardness range: comprehensive evaluation of sense organ and taste is carried out on the Nanguo pear, and the hardness range of the good flavor is 3-7kg/cm 2 ；
Method for searching optimal hardness of Nanguo pear and its result
The method is characterized by searching the optimum maturity (hardness range, within the range, the Nanguo pear can be cut into blocks and has good taste, the cut Nanguo pear can be directly used in the processing fields of fruit grain yoghourt, fruit grain jelly, cans and the like without seasoning), picking the Nanguo pear with commercial maturity, selecting the Nanguo pear without insect and disease damage, and storing the Nanguo pear without mechanical damage at the room temperature of 23 ℃. From day 0 after harvest, 6 fruits were randomly selected each day for testing hardness, soluble solids, and subjected to sensory and flavor evaluation as shown in table 1:
TABLE 1 evaluation table of Nanguo pear performance index
Figure BDA0002467693450000071
Grading:
and (3) excellent: 23-27; good: 17-23; the method comprises the following steps: 12-17; difference: 0-12.
Figure BDA0002467693450000072
Figure BDA0002467693450000081
FIG. 1 is a graph showing the change of performance index of Nanguo pear
The experimental results are as follows: as shown in FIG. 1, in the hardness range of 3-7kg/cm 2 Within the range, the quality is better. The Nanguo pear in the range has better flavor, and can be directly used for fresh cutting and subsequent processing. The pear with the hardness close to 7 is moderate in hardness, sour, sweet and delicious, accords with the preference of consumers who like crisp pears, and the pear with the hardness close to 3 is soft, sweet and thick in alcohol taste, accords with the preference of consumers who like flour pears and have heavy taste.
(B) Slicing and preserving: removing core of Nanguo pear, and cutting into 6 × 4 × 2cm 3 The wedge-shaped pear blocks are put into the green preservative solution to be soaked for 3min and then taken out, aired for 1min and wiped off with absorbent gauze to remove redundant moisture; then, putting the pear blocks into a fresh-keeping film-forming agent, soaking for 2min, and airing;
(C) And (3) storage: wiping off water with absorbent gauze, packaging into PE self-sealing bag, and storing in 3-5 deg.C thermostat.
Example 2
The difference from example 1 is that (B) is sliced and kept fresh: removing core of Nanguo pear, cutting into 6 × 4 × 2cm 3 The wedge-shaped pear blocks are put into the green preservative solution to be soaked for 3min and then taken out, aired for 1.5min and wiped off with absorbent gauze to remove excessive moisture; then, putting the pear blocks into a fresh-keeping film-forming agent, soaking for 1.5min, and airing;
(C) And (3) storage: wiping off water with absorbent gauze, packaging into PE self-sealing bag, and storing in 3-5 deg.C thermostat.
The fresh-cut south fruit pear green preservative comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.45 part of watermelon peel extract, 1.05 parts of mangosteen peel extract, 0.85 part of pomegranate peel extract, 3.9 parts of chrysanthemum extract, 0.6 part of resveratrol, 1.45 parts of citric acid, 1.85 parts of calcium chloride and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 32 parts of modified whey protein, 10.5 parts of chitosan, 0.3 part of alanine and the balance of water.
The fresh-keeping film forming agent is a trans-lactoalbumin-oligomeric chitosan membrane blending solution, and the fresh-keeping film forming agent comprises the following preparation steps:
1) Transferring whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:10.5, magnetically stirring for 31min, then carrying out water bath for 32min at 86 ℃, continuously stirring, cooling, adding glycerol with the mass content of 61%, stirring for 31min, then adding transglutaminase to ensure that the enzyme-substrate concentration ratio is 0.04, adjusting the pH value to 7.45, carrying out water bath oscillation culture at 61 ℃ for 71min, taking out, heating in the water bath at 82 ℃ for 6min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 11min, and keeping for later use;
2) Preparing the chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.11mol/L acetic acid solution, mechanically stirring for 1.05h until the chitosan is completely dissolved to obtain low chitosan solution with the molecular weight of 3000-3200, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:10.5, reacting for 8.5h at 52 ℃ and pH value of 5.05 to obtain oligomeric chitosan, boiling the obtained reaction solution in boiling water bath for 5.5min to inactivate enzyme, carrying out vacuum filtration to remove enzyme, adjusting the pH value to be neutral by using NaOH solution with the concentration of 2.05mol/L, and keeping for later use;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (2) mixing the converted whey protein and the chitosan oligosaccharide according to the mass ratio of 3.2:1, adding alanine, stirring for 27min at 35 ℃, adjusting the pH to be neutral by using 1.05mol/L HCl and 1.05mol/L NaOH, cooling to room temperature, adding water to fix the volume, stirring for 32min again, vacuumizing and degassing, wherein the vacuum degree is 91Pa, and obtaining a finished product.
The green preservative solution comprises the following preparation steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-78 deg.C for 22.5h, freeze-drying for 21h, grinding, weighing watermelon peel powder, adding 70.5% ethanol solution, and mixing solid and liquid at a solid-liquid mass ratio of 1:18.5, extracting under reflux for 49min, centrifuging, recovering ethanol, and concentrating to obtain soft extract;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 5.2h, reflux-extracting for 2 times (1.05 h each time), adding 17 times of water based on flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.04, adding ethanol to make ethanol concentration reach 63.5%, stirring, standing for 10.5h, filtering, recovering ethanol, and concentrating flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with sterile prop, cutting into small pieces, placing in a refrigerator at-79 deg.C for 22.5h, freeze drying for 23.5h, grinding, weighing mangosteen bark powder in a beaker, adding 80.5% ethanol solution, water bathing for 32min, adding 78.5% ethanol solution, water bathing for 31min, recovering ethanol, and concentrating to obtain a thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-80 deg.C to-75 deg.C for 21h, freeze drying for 21h, grinding, weighing pericarpium Granati powder, adding 60.05% ethanol solution, and mixing the solid and liquid ratios of 1:38.5, recovering ethanol after ultrasonic extraction for 36min, and concentrating to obtain a thick paste;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.45ul/L, adding citric acid and calcium chloride with mass content of 1.3% and 1.85%, mixing well, and controlling solid-to-liquid ratio at 1:10.5, stirring in 56 deg.C water bath for 31min, ultrasonic dispersing for 22min, homogenizing for 11min, vacuum defoaming for 4.2h, and cold preserving at 4.5 deg.C.
Example 3
The difference from example 1 is that (B) is sliced and kept fresh: removing core of Nanguo pear, cutting into 6 × 4 × 2cm 3 The wedge-shaped pear blocks are put into the green preservative solution to be soaked for 3min and then taken out, aired for 1.5min and wiped off with absorbent gauze to remove excessive moisture; then, putting the pear blocks into a fresh-keeping film-forming agent, soaking for 2min, and airing;
(C) And (3) storage: wiping off water by absorbent gauze, filling into a PE self-sealing bag, and storing in a constant temperature box at 4 ℃.
The fresh-cut south fruit pear green preservative comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.5 part of watermelon peel extract, 1.1 parts of mangosteen peel extract, 1 part of pomegranate peel extract, 1 part of chrysanthemum extract, 0.6 part of resveratrol, 1.5 parts of citric acid, 1.9 parts of calcium chloride, and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 35 parts of modified whey protein, 11 parts of chitosan, 0.4 part of alanine and the balance of water.
The fresh-keeping film forming agent is a transfer whey protein-oligochitosan blended film liquid, and the fresh-keeping film forming agent comprises the following preparation steps:
1) Transferring whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:11, magnetically stirring for 32min, then carrying out water bath for 35min at 87 ℃ and continuously stirring, cooling, adding 63% glycerol by mass, stirring for 33min, then adding transglutaminase to enable the enzyme-substrate concentration ratio to be 0.05, adjusting the pH value to be 7.5, carrying out water bath oscillation culture at 63 ℃ for 73min, taking out, heating in water bath at 83 ℃ for 6min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 13min, and keeping for later use;
2) Preparing chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.11mol/L acetic acid solution, mechanically stirring for 1.1h until the chitosan is completely dissolved to obtain low chitosan solution with molecular weight of 3000-200, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:11, reacting for 9 hours at the temperature of 53 ℃ and the pH value of 5.1 to obtain the oligomeric chitosan, putting the obtained reaction liquid into a boiling water bath to boil for 6 minutes to inactivate the enzyme, carrying out suction filtration under reduced pressure to remove the enzyme, adjusting the pH value of the solution to be neutral by using a NaOH solution with the concentration of 2.1mol/L, and reserving the solution for later use;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (2) mixing the converted whey protein and the chitosan oligosaccharide according to the mass ratio of 3.5:1, adding alanine, stirring for 28min at 38 ℃, adjusting the pH to be neutral by using 1.1mol/L HCl and 1.1mol/L NaOH, cooling to room temperature, adding water to fix the volume, stirring for 35min again, vacuumizing and degassing, wherein the vacuum degree is 92Pa, and obtaining a finished product.
The green preservative solution comprises the following preparation steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-77 deg.C for 23h, freeze-drying for 22h, grinding, weighing watermelon peel powder, adding 71% ethanol solution, and mixing the solid and liquid at a solid-liquid mass ratio of 1:19, refluxing and extracting for 49min, centrifuging, recovering ethanol, and concentrating to obtain a thick paste;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 5.5h, reflux extracting for 3 times, each time for 1.1h, adding water in an amount 18 times of the mass of flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.04, adding ethanol to reach alcohol concentration of 64%, stirring uniformly, standing for 11h, filtering, recovering ethanol, and concentrating flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with sterile prop, cutting into small pieces, placing in a refrigerator at-78 deg.C for 23h, freeze drying for 24h, grinding, weighing mangosteen bark powder in a beaker, adding 81% ethanol solution, water-bathing for 35min, adding 79% ethanol solution, water-bathing for 33min, recovering ethanol, and concentrating to obtain thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-78 deg.C for 22h, freeze drying for 22h, grinding, weighing pericarpium Granati powder, adding 61% ethanol solution, and making into tablet, capsule, or tablet, wherein the solid-to-liquid ratio is 1:39, recovering ethanol after ultrasonic extraction for 37min, and concentrating to obtain a thick paste;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.45ul/L, adding citric acid and calcium chloride with mass content of 1.35% and 1.9%, respectively, mixing well, and controlling solid-to-liquid ratio at 1:11, placing the mixture into a water bath with the temperature of 58 ℃ for stirring for 33min, performing ultrasonic dispersion for 25min, homogenizing for 13min, performing vacuum defoamation for 4.5h, and performing cold storage at the temperature of 5 ℃.
Example 4
The difference from example 1 is that (B) is sliced and kept fresh: removing core of Nanguo pear, cutting into 6 × 4 × 2cm 3 The wedge-shaped pear blocks are placed into the green preservative solution to be soaked for 4min and then taken out, aired for 1.8min, and excess water is wiped off by absorbent gauze; then putting the pear blocks into the fresh-keeping film-forming agent, soaking for 2.5min, and airing;
(C) And (3) storage: wiping off water with absorbent gauze, packaging into PE self-sealing bag, and storing in 4.5 deg.C thermostat.
The fresh-cut south fruit pear green preservative comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.55 part of watermelon peel extract, 1.15 parts of mangosteen peel extract, 1.1 parts of pomegranate peel extract, 4.1 parts of chrysanthemum extract, 0.7 part of resveratrol, 1.55 parts of citric acid, 1.95 parts of calcium chloride and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 38 parts of modified whey protein, 11.5 parts of chitosan, 0.45 part of alanine and the balance of water.
The fresh-keeping film forming agent is a transfer whey protein-oligochitosan blended film liquid, and the fresh-keeping film forming agent comprises the following preparation steps:
1) Transferring whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:11.5, magnetically stirring for 34min, then carrying out water bath for 38min at 89 ℃, continuously stirring, cooling, adding glycerol with the mass content of 64%, stirring for 34min, then adding transglutaminase to enable the enzyme-substrate concentration ratio to be 0.05, adjusting the pH value to be 7.55, carrying out water bath oscillation culture at 64 ℃ for 74min, taking out, heating in water bath at 84 ℃ for 7min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 14min, and keeping for later use;
2) Preparing chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.11mol/L acetic acid solution, mechanically stirring for 1.15h until the chitosan is completely dissolved to obtain low chitosan solution with molecular weight of 23000-3200, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:11.5, reacting for 9.5h at 54 ℃ and pH value of 5.15 to obtain oligomeric chitosan, boiling the obtained reaction solution in boiling water bath for 7.5min to inactivate enzyme, carrying out vacuum filtration to remove enzyme, adjusting the pH value to be neutral by using NaOH solution with the concentration of 2.15mol/L, and reserving for later use;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (3) mixing the converted whey protein and the chitosan oligosaccharide according to the mass ratio of 3.8:1, adding alanine, stirring for 29min at 42 ℃, adjusting the pH to be neutral by using 1.15mol/L HCl and 1.15mol/L NaOH, cooling to room temperature, adding water to constant volume, stirring for 38min again, vacuumizing and degassing to reach the vacuum degree of 93Pa, and obtaining the finished product.
The green preservative solution comprises the following preparation steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-77 deg.C for 23.5h, freeze-drying for 23h, grinding, weighing watermelon peel powder, adding 71.5% ethanol solution, and mixing solid and liquid at a solid-liquid mass ratio of 1:19.5, performing reflux extraction for 49.5min, centrifuging, recovering ethanol, and concentrating to obtain a thick paste;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 5.8h, reflux extracting for 3 times, each time for 1.15h, adding water amount 19 times of flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.04, adding ethanol to make alcohol concentration reach 64%, stirring well, standing for 11h, filtering, recovering ethanol, and concentrating flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with sterile prop, cutting into small pieces, placing in a refrigerator at-76 deg.C for 23.5h, freeze drying for 24h, grinding, weighing mangosteen bark powder in a beaker, adding 81% ethanol solution, water-bathing for 38min, adding 79% ethanol solution, water-bathing for 33min, recovering ethanol, and concentrating to obtain thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp by using a sterile prop, cutting into small pieces, placing in a refrigerator at the temperature of-77 ℃ for 23.5h, freeze-drying for 23h, grinding again, weighing pomegranate peel powder into a container, adding 61.5% ethanol solution, and mixing the solid-liquid ratio of 1:39.5, recovering ethanol after ultrasonic extraction for 39min, and concentrating to obtain a thick paste;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.48ul/L, adding citric acid and calcium chloride with mass content of 1.4% and 1.9%, respectively, mixing well, and controlling solid-to-liquid ratio at 1:11.5, stirring in a water bath at 58 ℃ for 34min, ultrasonically dispersing for 28min, homogenizing for 14min, defoaming under reduced pressure for 4.8h, and refrigerating at 5.5 ℃ for storage.
Example 5
The difference from example 1 is that (B) is sliced and kept fresh: removing core of Nanguo pear, and cutting into 6 × 4 × 2cm 3 The wedge-shaped pear blocks are placed into the green preservative solution to be soaked for 5min and then taken out, aired for 2min, and excess water is wiped off by absorbent gauze; then putting the pear blocks into a fresh-keeping film-forming agent, soaking for 3min, and airing;
(C) And (3) storage: wiping off water with absorbent gauze, packaging into PE self-sealing bag, and storing in 5 deg.C incubator.
The fresh-cut south fruit pear green preservative comprises a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.6 part of watermelon peel extract, 1.2 parts of mangosteen peel extract, 1.2 parts of pomegranate peel extract, 4.2 parts of chrysanthemum extract, 0.8 part of resveratrol, 1.6 parts of citric acid, 2 parts of calcium chloride and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 40 parts of modified whey protein, 12 parts of chitosan, 0.5 part of alanine and the balance of water.
The fresh-keeping film forming agent is a trans-lactoalbumin-oligomeric chitosan membrane blending solution, and the fresh-keeping film forming agent comprises the following preparation steps:
1) Transferring whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:12, magnetically stirring for 35min, then performing water bath for 40min at 90 ℃ and continuously stirring, cooling, adding 65% glycerol by mass, stirring for 35min, then adding transglutaminase to enable the enzyme-substrate concentration ratio to be 0.06, adjusting the pH value to be 7.6, performing water bath oscillation culture at 65 ℃ for 75min, taking out, heating in water bath at 85 ℃ for 5-8min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 15min, and keeping for later use;
2) Preparing chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.12mol/L acetic acid solution, mechanically stirring for 1.2h until the chitosan is completely dissolved to obtain low chitosan solution with the molecular weight of 3000-3200, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:12, reacting for 10 hours at 55 ℃ and under the condition of pH value of 5.2 to obtain oligomeric chitosan, placing the obtained reaction liquid in boiling water bath for boiling for 5-8min to inactivate enzyme, carrying out vacuum filtration to remove enzyme, adjusting the pH value to be neutral by using NaOH solution with the concentration of 2.2mol/L, and reserving for later use;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (3) mixing the converted whey protein and the chitosan oligosaccharide according to a mass ratio of 4:1, adding alanine, stirring for 30min at 45 ℃, adjusting the pH to be neutral by using 1.2mol/L HCl and 1.2mol/L NaOH, cooling to room temperature, adding water to constant volume, stirring for 40min again, vacuumizing and degassing to obtain a finished product with the vacuum degree of 95Pa.
The green preservative solution comprises the following preparation steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-75 deg.C for 24h, freeze-drying for 24h, grinding, weighing watermelon peel powder, adding 72% ethanol solution, and mixing the solid and liquid at a solid-liquid mass ratio of 1:20, refluxing and extracting for 50min, centrifuging, recovering ethanol, and concentrating to obtain a thick paste;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 6h, reflux extracting for 3 times, each time for 1.2h, adding water in an amount of 20 times of the mass of flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.05, adding ethanol to reach alcohol concentration of 65%, stirring well, standing for 12h, filtering, recovering ethanol, and concentrating the flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with sterile prop, cutting into small pieces, placing in a refrigerator at-75 deg.C for 24 hr, freeze drying for 25 hr, grinding, weighing mangosteen bark powder in a beaker, adding 82% ethanol solution, water bathing for 40min, adding 80% ethanol solution, water bathing for 35min, recovering ethanol, and concentrating to obtain thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-75 deg.C for 24h, freeze drying for 24h, grinding, weighing pericarpium Granati powder, adding 62% ethanol solution, and making into tablet, capsule, or tablet, wherein the solid-to-liquid ratio is 1:40, recovering ethanol after ultrasonic extraction is carried out for 40min, and concentrating the ethanol into thick paste;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.5ul/L, adding citric acid and calcium chloride with mass content of 1.5% and 2%, respectively, mixing well, and controlling solid-to-liquid ratio at 1:12, stirring in a water bath at 60 ℃ for 35min, ultrasonically dispersing for 30min, homogenizing for 15min, decompressing and defoaming for 5h, and refrigerating and storing at 6 ℃.
Comparative example 1
The difference from example 1 is that the Nanguo pears were denucleated and cut into 6X 4X 2cm 3 The wedge-shaped pear blocks are not soaked in the green preservation solution.
Comparative example 2
The difference from example 1 is that the Nanguo pears were denucleated and cut into 6X 4X 2cm 3 The wedge-shaped pear blocks are soaked in the green preservative solution, and the pear blocks are not soaked in the film-forming agent.
Comparative example 3
The difference from example 1 is that the Nanguo pears were denucleated and cut into 6X 4X 2cm 3 The wedge-shaped pear blocks are soaked in a green fresh-keeping solution and then soaked in a chitosan solution with the same concentration.
Comparative example 4
The difference from the embodiment 1 is that the mass parts of the components except the water in the fresh-keeping liquid are 50% of the embodiment, and the mass part of the water is between 95 and 96%.
Comparative example 5
The difference from the embodiment 1 is that the ratio of each component of the film forming agent is the trans-whey protein: and (3) chitosan oligosaccharide: the water content is 15:5:80.
TABLE 2 optimized parameter indexes of Nanguo pear slices
Figure BDA0002467693450000141
Figure BDA0002467693450000151
Note: the data in the table all contain three biological replicates.
And (4) conclusion:
as can be seen from the data in table 2. The green preservative solution and the preservative film-forming agent prepared in the embodiments 1-5 have good preservation effect after relevant operation procedures, remarkably improve the storage quality of the fresh-cut south fruit pears, and prolong the shelf life of the fresh-cut south fruit pears. The formula of the fresh-keeping liquid is food-grade raw materials, and the fresh-cut fruits and vegetables can be directly eaten after being soaked in the fresh-keeping liquid, so that the taste of the fresh-cut fruits and vegetables cannot be adversely affected, and the storage and fresh-keeping period of the Nanguo pears is greatly prolonged.
The coating process of the comparative example 1 lacks the soaking of the compound preservative, so that the pear blocks are not effectively subjected to oxidation resistance and browning resistance, the preservation effect is poor, and the pear blocks are quickly browned, rotted and flavor lost;
the fresh-keeping film-forming agent is lacked in the 02 coating process, so that the oxygen permeability and the water permeability of the surface of the pear blocks are low, and the fresh-keeping liquid only can keep good color and flavor of the pear blocks but cannot well delay the rotting speed of the pear blocks;
the film forming agent of the comparative example 3 is chitosan, the molecular weight is not reduced, and the converted whey protein is not added, so that the chitosan solubility is low, the moisture retention of the film liquid is too low, the pear blocks are dehydrated quickly, and the commercial value is lost;
the embodiment of the mass part of the effective components in the preservative solution of the comparative example 4 is few, the corresponding antioxidation and anti-browning effects cannot be achieved, and the browning degree of the pear blocks is relatively high;
comparative example 5 the ratio of whey protein to chitosan oligosaccharide was reduced, resulting in thin film solution, not easy to attach to the surface of pear block, and resulting in uneven browning and rotting degree of the same pear block.
As can be seen from the data of examples 1 to 5 and comparative examples 1 to 5, only the scheme within the scope of the claims of the present invention can satisfy the above requirements in all aspects, and an optimized scheme can be obtained, so that an optimal green preservative can be obtained. While the change of the mixture ratio, the replacement/addition/subtraction of the raw materials or the change of the feeding sequence can bring corresponding negative effects.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modifications, alterations and equivalent changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (5)

1. The green preservative for the fresh-cut nanguo pears is characterized by comprising a green preservative solution and a preservative film-forming agent, wherein the green preservative solution comprises the following components in 100 parts by mass: 0.4-0.6 part of watermelon peel extract, 1-1.2 parts of mangosteen peel extract, 0.8-1.2 parts of pomegranate peel extract, 3.8-4.2 parts of wild chrysanthemum extract, 0.5-0.8 part of resveratrol, 1.4-1.6 parts of citric acid, 1.8-2 parts of calcium chloride and the balance of water; the fresh-keeping film-forming agent comprises the following components in 100 parts by mass: 30-40 parts of modified whey protein, 10-12 parts of chitosan, 0.2-0.5 part of alanine and the balance of water; the fresh-keeping film forming agent comprises the following preparation steps:
1) Modified whey protein: weighing whey protein isolate powder, adding distilled water to dissolve the whey protein isolate powder, wherein the solid-to-liquid ratio is 1:10-12, magnetically stirring for 30-35min, then carrying out water bath for 30-40min at 85-90 ℃ and continuously stirring, cooling, adding 60-65% by mass of glycerol, stirring for 30-35min, then adding transglutaminase to enable the enzyme-substrate concentration ratio to be 0.04-0.06, carrying out water bath culture under the conditions that the pH value is adjusted to be 7.4-7.6, carrying out water bath shaking culture at 60-65 ℃ for 70-75min, taking out, heating in water bath at 80-85 ℃ for 5-8min to inactivate enzyme, cooling to room temperature, placing in a vacuum drying oven, degassing for 10-15min, and keeping for later use;
2) Preparing chitosan oligosaccharide: weighing dry chitosan, dissolving the chitosan in 0.1-0.12mol/L acetic acid solution, mechanically stirring for 1-1.2h until the chitosan is completely dissolved to obtain chitosan solution, adding cellulase enzyme solution into the chitosan solution for degradation reaction, wherein the solid-to-liquid ratio of the chitosan to the cellulase enzyme solution is 1:10-12, reacting for 8-10h at 50-55 deg.C and pH 5-5.2 to obtain oligomeric chitosan with molecular weight of 3000-3200, boiling the obtained reaction solution in boiling water bath for 5-8min to inactivate enzyme, vacuum filtering to remove enzyme, adjusting pH to neutral with sodium hydroxide solution, and reserving;
3) Transferring whey protein-chitosan oligomer membrane blending liquid: and (3) mixing the transformed whey protein and the chitosan oligosaccharide according to the mass ratio of 3-4:1, adding alanine, stirring at 30-45 ℃ for 25-30min, adjusting the pH to be neutral by using 1.0-1.2mol/L HCl and 1.0-1.2mol/L NaOH, cooling to room temperature, adding water to constant volume, stirring for 30-40min again, vacuumizing and degassing to obtain the finished product.
2. The fresh-cut Nanguo pear green preservative according to claim 1, wherein the concentration of the sodium hydroxide solution in the step 2) is 2-2.2 mol/L.
3. The green preservative for fresh-cut south fruit pears as claimed in claim 1, wherein the degree of vacuum of the vacuum degassing in the step 3) is 90-95Pa.
4. The fresh-cut south fruit pear green preservative according to claim 1, wherein the green preservative solution comprises the following preparation steps:
(1) Preparing a watermelon peel extract: cleaning watermelon, removing outer skin and red pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-80- -75 deg.C for 22-24h, freeze drying for 20-24h, grinding, weighing watermelon peel powder, placing in a container, adding 70-72% ethanol solution, and mixing at a solid-liquid mass ratio of 1:18-20, extracting under reflux for 48-50min, centrifuging, recovering ethanol, and concentrating to obtain soft extract;
(2) Preparing a wild chrysanthemum extract: soaking flos Chrysanthemi Indici in water for 5-6h, reflux extracting for 2-3 times, each time for 1-1.2h, adding water 16-20 times of flos Chrysanthemi Indici, mixing decoctions, concentrating to relative density of 1.03-1.05, adding ethanol to reach alcohol concentration of 63-65%, stirring, standing for 10-12h, filtering, recovering ethanol, and concentrating flos Chrysanthemi Indici extractive solution to obtain soft extract;
(3) Preparing a mangosteen bark extract: cleaning mangosteen, removing flesh with aseptic prop, cutting into small pieces, placing in a refrigerator at-80- -75 deg.C for 22-24 hr, freeze drying for 23-25 hr, grinding, weighing mangosteen bark powder, placing in a beaker, adding 80-82% ethanol solution, water bathing for 30-40min, adding 78-80% ethanol solution, water bathing for 30-35min, recovering ethanol, and concentrating to obtain thick paste;
(4) Preparing a pomegranate peel extract: cleaning pomegranate, removing pulp with sterile prop, cutting into small pieces, placing in a refrigerator at-80- -75 deg.C for 20-24h, freeze drying for 20-24h, grinding, weighing pericarpium Granati powder, adding 60-62% ethanol solution, and mixing at a solid-to-liquid ratio of 1:38-40, ultrasonic extracting for 35-40min, recovering ethanol, and concentrating to obtain soft extract;
(5) Mixing the above four extracts in a container, adding resveratrol with concentration of 0.4-0.5ul/L, adding citric acid and calcium chloride, mixing, and controlling solid-to-liquid ratio at 1:10-12, stirring in water bath at 55-60 deg.C for 30-35min, ultrasonic dispersing for 20-30min, homogenizing for 10-15min, vacuum defoaming for 4-5h, and refrigerating at 4-6 deg.C for storage.
5. The application of the green preservative for fresh-cut south fruit pears as claimed in claim 1, which is characterized by comprising the following steps:
(A) Finding the optimal flavor hardness range: comprehensively evaluating the sense and taste of the Nanguo pear to obtain the optimal flavor hardness range;
(B) Cutting into blocks and preserving: removing core of Nanguo pear, cutting into pieces, soaking in the green preservative solution, air drying, soaking in preservative film-forming agent, and air drying;
(C) And (3) storage: packaging, and storing in a constant temperature box at 3-5 deg.C.
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