CN115176840A - Processing method and application of freeze-dried mulberry - Google Patents
Processing method and application of freeze-dried mulberry Download PDFInfo
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- CN115176840A CN115176840A CN202210842586.0A CN202210842586A CN115176840A CN 115176840 A CN115176840 A CN 115176840A CN 202210842586 A CN202210842586 A CN 202210842586A CN 115176840 A CN115176840 A CN 115176840A
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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
- A23B7/02—Dehydrating; Subsequent reconstitution
- A23B7/024—Freeze-drying, i.e. cryodessication or lyophilisation
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L19/00—Products from fruits or vegetables; Preparation or treatment thereof
- A23L19/01—Instant products; Powders; Flakes; Granules
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L19/00—Products from fruits or vegetables; Preparation or treatment thereof
- A23L19/03—Products from fruits or vegetables; Preparation or treatment thereof consisting of whole pieces or fragments without mashing the original pieces
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- 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
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
- Y02P60/80—Food processing, e.g. use of renewable energies or variable speed drives in handling, conveying or stacking
- Y02P60/85—Food storage or conservation, e.g. cooling or drying
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
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Abstract
The invention discloses a mulberry vacuum freeze-drying processing technology, which comprises the steps of raw material selection, pretreatment, prefreezing, sublimation drying and desorption drying. Wherein the pre-freezing process comprises the steps of firstly cooling to minus 5 ℃ to minus 20 ℃ within 10min to 30min, carrying out super-cooling and heat preservation, and preserving the heat for 10min to 40min; then cooling to-30 to-35 ℃ within 5 to 20min, and keeping the temperature for 10 to 40min; then annealing treatment is carried out, namely the temperature is raised to minus 18 ℃ to minus 24 ℃ within 8min to 25min, and the temperature is kept for 20min to 40min; finally, the temperature is reduced to minus 30 ℃ to minus 35 ℃ within 5min to 25min, and the temperature is preserved for 10min to 30min. The mulberry vacuum freeze drying processing technology of the invention does not need to add any additive, pigment and sweetener, can effectively maintain the integrity and plumpness of the dried mulberry, the water content of the product is controlled to be 3-5%, and the anthocyanin content is maintained to be more than 92%. The method has strong stability, the yield is 86-97%, and the total time of pre-freezing and drying is 720-1200 min.
Description
Technical Field
The invention relates to a mulberry vacuum freeze-drying processing technology and application, in particular to a vacuum freeze-drying processing technology capable of keeping original color, original taste and original shape of mulberry.
Background
The Mori fructus is dry fruit ear of Morus alba L. The mulberry is harvested after 4-6 months of maturity every year, is rich in anthocyanin (anthocyanin), has an antioxidation effect, is beneficial to the growth of hematopoietic cells, and has the effects of antioxidation, blood fat reduction, blood sugar reduction, liver protection, cancer resistance and the like. The mulberry is distributed in most parts of the country, such as the mulberry with salt black, the planting area has good environment and no pollution; the special subtropical dry valley climate has elevation above 900 m, great day and night temperature difference, sufficient sugar and sweet taste. However, morous alba is very apt to deteriorate its fruit after picking due to mechanical damage and contamination by microorganisms. Drying is one of the most common methods for processing and keeping fresh of mulberry at present, and for example, the traditional methods of drying in the sun or by baking, air drying by blowing and the like are used. However, the traditional drying method has the defects that the contained anthocyanin is easy to oxidize and decompose due to long drying time or high temperature, and sugar nutrition is lost, so that the texture and the taste of a dry product are changed, and the taste effect of a fresh product cannot be achieved. In recent years, vacuum freeze-drying, or "freeze-drying", has received increasing attention, which is a drying method by which moisture is directly sublimated from a solid state to a gaseous state at a high vacuum degree. The method can reduce nutrition loss of the product to the maximum extent and maintain the appearance shape of the product. The freeze-drying process is generally divided into pretreatment, pre-freezing, sublimation, desorption drying and other processes, and the process parameters in each process are related to the quality of the freeze-dried product.
At present, the main technical problems of the freeze-drying technology aiming at the whole mulberry are as follows: 1) Irregular ice crystals formed in the freezing process of freeze-drying and pressure changes easily cause adverse effects such as mulberry cell shrinkage, damage, sugar liquor extravasation and the like, and phenomena such as pulp explosion, disc sticking and the like often occur in the production process, so that the selling phase of dried mulberry products and the loss of nutritional value are influenced, the quality of the dried mulberry products is reduced, the yield of the dried mulberry products is low, the taste is also influenced, and meanwhile, dust is generated in the drying process to influence the working efficiency of drying matching equipment. 2) Unlike freeze-dried apple slices, banana slices, lemon slices, hawthorn and other products in the market, mulberry is a berry with high sugar content and high water content, is formed by a small fruit capsule, has a long fruit shape, needs long drying time and has high production cost.
Chinese patent CN104095029A discloses a preparation process of vacuum freeze-dried mulberry products. The patent relates to a mulberry dried product which is prepared by taking mulberry fruits as raw materials, and performing the process technologies of raw material pretreatment, pre-freezing, sublimation, resolution drying, packaging and the like to obtain the mulberry dried product which is purple black, microcosmically is in a porous sponge shape and has the water content of less than 5 percent. The prefreezing process of the method adopts a two-stage gradual cooling mode, the sublimation and analysis processes do not involve the step-by-step regulation and control of temperature and vacuum degree, the prefreezing and drying time needs to spend 27-35 h in total time, and the production cost is high.
At present, in order to overcome the disadvantages of the above processes for preparing freeze-dried morus alba, additives, color protecting agents, sweeteners, etc. can be added during the freeze-drying process. For example, in CN104095029A, fresh mulberry fruits are soaked in sucrose solution with a mass fraction of 25% -35%, which can increase sweet taste of the product by 1-2 times and reduce the process time to 23-26 h, but still cannot effectively reduce the time cost, and does not meet the health requirement of "zero addition" of fruits. Therefore, the method aims at the defects, and the existing freeze-drying process is optimized and adjusted to a certain extent, so that the quality of freeze-dried mulberry is further improved.
The invention content is as follows:
in order to overcome the defects of the prior art, one of the purposes of the invention is to provide a mulberry vacuum freeze-drying processing technology, and the freeze-drying technology provided by the invention can effectively keep the integrity and the plumpness of dried mulberries without adding any additive, color protection pigment and sweetening agent, can furthest keep and optimize the taste of the product, controls the water content of the product to be 3-5% and keeps the anthocyanin content to be more than 92%. The process method has strong stability, the yield is 86-97%, and the pre-freezing and drying time is 720-1200 min (12-20 h). In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a mulberry vacuum freeze-drying processing technology, which comprises the following steps:
(1) Selecting raw materials: selecting and picking black mulberry with fruit stalks in the new and middle period of production, no damage and no plant diseases and insect pests;
(2) Pretreatment: putting the selected fresh mulberry fruit into ozone water with the concentration of 0.5-3.0 mg/L for blowing, cleaning and soaking for 2-5 min, and taking out clear water for cleaning for 1-3 times.
(3) Pre-freezing: draining the cleaned Mori fructus to remove surface water, and dishing in an amount of 12kg/m 2 ～15kg/m 2 Placing the mixture into a freeze dryer, cooling the mixture to minus 5 ℃ to minus 20 ℃ for 10min to 30min, and carrying out super-cooling and heat preservation for 10min to 40min; then cooling to-30 to-35 ℃ within 5 to 20min, and keeping for 10 to 40min; then annealing treatment is carried out, namely the temperature is raised to minus 18 ℃ to minus 24 ℃ within 8min to 25min, and the temperature is kept for 20min to 40min; finally, the temperature is reduced to minus 30 ℃ to minus 35 ℃ for 5min to 25min and is kept for 10min to 30min.
(4) Sublimation drying: starting a cold trap system, keeping the vacuum degree at 30-40 Pa when the temperature of the cold trap is lower than-48 ℃, and heating to 25-33 ℃ by a heating plate for 20-50 min; preserving the heat for 50-100 min; the heating plate is heated to 44-56 ℃ within 5-20 min, the vacuum degree is controlled to be 60-90 Pa, and the temperature is kept for 300-400 min.
(5) And (3) resolving and drying: heating the heating plate to 60-68 ℃ within 12-26 min, controlling the vacuum degree to 10-30 Pa, and keeping the temperature for 160-240 min; the temperature of the heating plate is reduced to 44-54 ℃ within 25-45 min, the vacuum degree is controlled to be 20-50 Pa, and the temperature is kept for 45-70 min.
If not specifically indicated, all temperatures during the process of the present invention refer to temperatures displayed on the meter, and it will be understood by those skilled in the art that due to error, the temperature displayed on the meter may differ by ± 2 ℃ from the actual heater plate temperature. In the process of the pre-freezing and drying technology, the time for cooling and heating refers to the time taken for cooling/heating to the end temperature by taking a certain specific temperature as the starting temperature, and if not specifically mentioned, the speed of cooling or heating in the process is constant.
The pre-freezing method is one of the key steps for realizing the technical effect of the invention. The pre-freezing temperature is lower than the eutectic temperature of the materials by 5-10 ℃, and the prior research shows that the eutectic point of the mulberry is about-21 ℃. From the aspects of saving energy and improving the freeze-drying efficiency, the pre-freezing temperature is selected to be-30 ℃ to-35 ℃. During the pre-freezing process, water in the fruit cells will gradually form ice crystals. The larger the pre-freezing cooling rate is, the faster the ice crystal nucleation speed is, fine crystals with smaller sizes are easy to form, smaller pores are easy to form after sublimation, and the drying rate is low and the energy consumption is high. On the contrary, the smaller the pre-freezing temperature reduction rate is, the larger pores are formed easily, which is beneficial to improving the drying rate, but the rehydration is poor. The inventor finds that the direct and rapid cooling means is adopted, namely the temperature is directly reduced to minus 30 ℃ to minus 35 ℃ within 10min to 25min to ensure that the materials are completely frozen, the pre-frozen mulberry is frozen for 180min, the surface of the obtained pre-frozen mulberry is cracked, sugar juice seeps out, dried fruits are shriveled, the dried fruits are bonded with mulberry fruits in different degrees, the number of damaged fruits is increased, and the finished product rate is only 60-75%. When a slow cooling means is adopted, namely the temperature is directly reduced to minus 30 ℃ to minus 35 ℃ within 90min to 150min, the freezing can be ensured to be finished only by keeping the temperature for 180min to 240min, and the time is longer. The prefreezing process of the invention adopts a non-direct rapid or slow cooling means, and is carried out in three stages: in the first stage, the temperature is firstly reduced to minus 5 ℃ to minus 20 ℃ for supercooling and heat preservation for 10min to 40min, and then the temperature is reduced to minus 30 ℃ to minus 35 ℃ for heat preservation for 10min to 40min. Annealing treatment is carried out in the second stage, namely, the temperature is raised back to minus 18 ℃ to minus 24 ℃ and is kept for 20min to 40min; in the third stage, the temperature is reduced to minus 30 ℃ to minus 35 ℃ again, and the temperature is kept for 10min to 30min. Because the supercooling heat preservation step is added in the first stage for transition, the temperature gradient change of the material is small, and the material is heated uniformly; then quickly cooling, and because the integral temperature of the material is closer to the crystallization temperature, the growth speed of the sample ice crystal is higher, and small ice crystals are easy to form. The annealing treatment is adopted in the second stage, so that the speed of forming ice crystals by the material can be improved, and the continuous formation of a large amount of small ice crystals is avoided. In the third stage, the temperature is reduced to-30 ℃ to-35 ℃ again, thereby ensuring the mulberry to be completely frozen. The freezing temperature and the freezing time are regulated and controlled in stages in the pre-freezing process, so that the phenomena of easy breakage and shrinkage of mulberry surfaces, sugar solution seepage and the like can be reduced, and the high requirements of the pre-freezing stage on equipment and operation due to the need of keeping a long-time low-temperature state are reduced, thereby reducing the energy consumption. In order to ensure good freezing state of the morous fruits, it is preferable that the prefreezing process comprises the steps of: firstly, cooling to-8-18 ℃ for 15-25 min, and carrying out supercooling and heat preservation for 20-30 min; then cooling to-32 to-34 ℃ within 10 to 15min, and keeping for 20 to 30min; then heating to-20 to-22 ℃ within 12 to 18min and keeping the temperature for 25 to 35min; finally, the temperature is reduced to minus 32 ℃ to minus 34 ℃ for 10min to 20min and is kept for 15min to 25min.
The regulation and control of the vacuum degree and the temperature in the drying process are one of the key steps for realizing the technical effect of the invention. The inventor finds that excessive heating exceeds the mulberry eutectic point or excessive heating speed and high vacuum degree easily causes pulp explosion in the sublimation drying process, so that mulberry local melting, volume reduction and foaming are caused, and the yield is low. For example, in the sublimation drying stage, the vacuum degree is maintained at 40Pa, and the obtained dried Mori fructus product has severe shrinkage and poor appearance. When the heating speed is too slow, on one hand, the drying time needs to be prolonged, and on the other hand, sublimed water vapor possibly accumulates in mulberry cells to soften the cell structure, so that the taste of the finished product is slightly soft. In the invention, sublimation drying is carried out in two stages, wherein in the first stage, firstly, the sublimation speed of ice crystals in the outer surface layer of the pre-frozen mulberry can be accelerated by vacuum pumping operation and adopting the vacuum degree with relatively low pressure (30-40 Pa), so that pores are formed on the surface layer, and sublimation drying is carried out by gradually pushing inwards. Meanwhile, the temperature is slowly raised to 25-33 ℃ through a heating plate so as to meet the heat required by sublimation of ice crystals in the mulberry. In the second stage, the heating plate is slowly heated to 44-56 ℃, the vacuum degree is controlled to be relatively high pressure (60-90 Pa), so that the sublimation speed of solid water in the mulberry is reduced, and the phenomenon that the internal pressure of the fruit is increased to cause the melting of the ice crystals due to the obstruction of the escape of water vapor generated after the sublimation of the ice crystals inside the fruit is avoided, thereby causing 'popping', softening and collapsing of the fruit. Specifically, the sublimation drying is carried out in sequence according to the following steps by adopting the following parameters: starting a cold trap system, controlling the vacuum degree to be 30-40 Pa when the temperature of the cold trap is lower than-48 ℃, heating a heating plate to 25-33 ℃ within 20-50 min, and keeping the temperature for 50-100 min; heating the heating plate to 46-56 ℃ within 5-20 min, controlling the vacuum degree to 60-90 Pa, and keeping the temperature for 300-400 min. In the above for further controlling the stability of water removal in morous alba, it is preferable that the sublimation drying comprises the steps of: when the temperature of the cold trap is lower than minus 48 ℃, keeping the vacuum degree at 32Pa to 38Pa, heating the heating plate to 28 ℃ to 32 ℃ within 30min to 40min, and preserving the heat for 65min to 75min; the heating plate is heated to 46-52 ℃ within 10-15 min, the vacuum degree is controlled to 65-75 Pa, and the temperature is kept for 320-380 min.
Further, after sublimation drying, there is moisture adsorbed on the surface of morous alba, and the difficulty of removing the water is increased compared to free water, and in order to achieve the removal effect as fast as possible and to secure the porous property inside morous alba cells, it is necessary to remove the moisture by desorption drying, i.e., further heating to supply energy. Specifically, the desorption drying in the invention comprises the following steps: heating the heating plate to 60-68 ℃ within 12-26 min, controlling the vacuum degree to 10-30 Pa, and keeping the temperature for 160-240 min; the temperature of the heating plate is reduced to 44-54 ℃ within 25-45 min, the vacuum degree is controlled to be 20-50 Pa, and the temperature is kept for 45-70 min. At the moment, the freeze-drying dehydration production of the water in the mulberry is finished, the water content of the freeze-dried mulberry is 3-5%, and the product has bright color, integrity, stiffness and appearance quality. In the analysis drying process, under the vacuum environment with lower pressure, the temperature is further raised to 60-68 ℃ on the basis of the temperature maintained by sublimation drying, and the temperature is kept for a long time, so that the adsorbed water is slowly analyzed, and the aim of thoroughly removing the water adsorbed on the surface of the mulberry as far as possible is fulfilled. In order to further enhance the degree of removing moisture adsorbed on the surface of morous alba, it is preferable that the desorption drying step comprises: heating the heating plate to 62-66 ℃ within 14-22 min, controlling the vacuum degree to 15-25 Pa, and keeping the temperature for 180-220 min; the temperature of the heating plate is reduced to 46-52 ℃ within 30-40 min, the vacuum degree is controlled to be 30-40 Pa, and the temperature is kept for 50-65 min.
In the present invention, the fresh morous alba may be a fresh morous alba harvested at a mature period conventionally selected in the art, preferably black morous alba in the midnatal period. Specifically, the growth of mulberry comprises a green fruit period, a color transition period and a mature period (black fruit period), wherein the mature period lasts for 6-14 days, 8 days before the mature period can be attributed to the early stage of black fruit, and 6 days after the mature period can be attributed to the later stage of black fruit, and the black mulberry refers to fresh mulberry in the black fruit period. Generally, the stem of morous alba in the early stage of black fruit is green, and the stem becomes black or brown in the late stage of black fruit. The inventor finds that the mulberry in the later period of the black fruit has weaker epidermis although the sweetness is higher by adopting the prior freeze-drying process method, the pulp bursting phenomenon in the freeze-drying process is very serious, if the freeze-drying process is not specially controlled, the yield of the dried mulberry is lower, usually only 30-50%, so that the requirements of the prior art method on the raw materials are relatively more severe, and the mulberry raw materials in the later period of the black fruit cannot be effectively applied. The inventor surprisingly finds that the mulberry yield in the later period of black fruits can be improved to 70-89% by adopting the process. Further, the black mulberry is preferably a mulberry in the early stage of the black mulberry; more preferably black mulberry with the length of 2.5 cm-3.2 cm and the width of 1.2 cm-1.6 cm. The length of the mulberry does not include the length of the stalk.
In the invention, ozone water soaking is adopted in the pretreatment stage to remove substances such as residual microorganisms, impurities, dust, pesticides and the like on the surfaces of fresh mulberries, and finally clear water is used to prevent residual pesticides or microorganisms in water from entering the fruits to cause mulberry circulating pollution in the soaking process. The total colony content of the fresh mulberry fruits obtained after cleaning is 90-100 CFU/g. On the other hand, the cleaning by ozone water and clear water can reduce a small amount of sugar adhered to the surface of the mulberry and reduce the possibility of forming bonding in the pre-freezing process.
And after drying, discharging, detecting the water content of the material, removing unformed bad fruits, dyed fruits and severely shrunken fruits, calculating the finished product ratio of the dried fruits, filling nitrogen, and packaging and sealing by adopting special pure aluminum. And (3) calculating the yield: the freeze-dried mulberry yield (dry fruit yield)/% = (mass of freeze-dried mulberry meeting the standard/mass of total freeze-dried mulberry) × 100%. The standard meeting is freeze-dried mulberry fruits after removing unformed bad fruits, dyed fruits and severely shrunken fruits.
Further, the mulberry vacuum freeze-drying processing technology provided by the invention can also comprise the steps of discharging and packaging, and particularly, after freeze-drying is finished, discharging is carried out in a nitrogen environment at the temperature of 15-20 ℃ so as to prevent mulberry products from absorbing water and becoming damp due to temperature gradient difference. The packaging step is to adopt pure aluminum packaging material, fill nitrogen and hermetically seal and package.
The invention also aims to provide the application of the processing technology in preparing the whole mulberry freeze-dried product.
Further, in one embodiment, the mulberry vacuum freeze-drying process of the present invention comprises the following steps:
(1) Selecting mulberry raw materials: selecting black mulberries which are picked in the early stage of black fruits in the new middle period of production, have fruit stalks and are free of damage and diseases and insect pests.
(2) Pretreatment: putting the selected fresh mulberry fruits into ozone water with the concentration of 2.0mg/L, blowing, cleaning and soaking for 3min, and taking out clear water for cleaning for 2 times.
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 13kg/m 2 Placing into a freeze dryer, cooling to-15 deg.C for 20minPerforming supercooling and heat preservation for 25min; cooling to-33 deg.C within 12min, and maintaining for 25min; then annealing treatment is carried out, the temperature is raised to-21 ℃ within 15min, and the temperature is kept for 30min; finally, the temperature is reduced to minus 33 ℃ within 15min and the temperature is preserved for 20min.
(3) The sublimation drying is as follows: starting a cold trap system, keeping the vacuum degree at 35Pa when the temperature of the cold trap is lower than-48 ℃, heating the plate to 30 ℃ within 30min, and keeping the temperature for 75min; heating the heating plate to 48 deg.C within 12min, controlling vacuum degree at 70Pa, and maintaining the temperature for 350min.
(4) The analysis and drying are as follows: heating the heating plate to 65 ℃ within 18min, controlling the vacuum degree to be 20Pa, and keeping the temperature for 200min; the temperature of the heating plate is reduced to 48 ℃ within 35min, the vacuum degree is controlled to be 35Pa, and the temperature is kept for 60min.
Compared with the prior art, the processing method of the freeze-dried mulberry has the beneficial effects that:
(1) The process scheme of the invention adopts staged variable temperature control in the pre-freezing stage, firstly cools to carry out supercooling and heat preservation, then slowly cools, and adds the steps of annealing and slow heating, thereby reducing the high requirements of the pre-freezing stage of the freeze-drying process on equipment and operation, and leading the industrial mass production of the mulberry to be easier to realize.
(2) According to the process scheme, sublimation and desorption drying are carried out, through the research on the vacuum degree, the temperature range, the temperature rising and reducing speed and the heat preservation time, the vacuum degree with relatively high pressure intensity is adopted in the second stage of sublimation and drying, the sublimation speed of water is slowed down, so that the phenomenon that the fruit is cracked due to the fact that steam escapes too fast is avoided, and the loss caused by mulberry sticking to the plate is overcome; in the desorption drying stage, the vacuum degree with relatively low pressure is adopted, the escape speed of water vapor is increased, the integrity of the cell structure is increased by utilizing the pressure difference effect, and the integrity and the plumpness of the dried mulberry cells are maintained.
(3) The process scheme of the invention keeps and optimizes the flavor of the product to the greatest extent by temperature control and pressure-variable protection without adding any additive, pigment and sweetener, avoids souring and scrap loss, has relatively lower requirements on raw materials, and is suitable for mulberries in the early stage of black fruit and mulberries in the later stage of black fruit with fragile epidermis; the yield can reach 86-97%, the total time of pre-freezing and drying is 720-1200 min (12-20 h), the production cost of the product is effectively reduced, the energy consumption is greatly reduced, and the method has beneficial effects.
Description of the drawings:
FIG. 1 shows the appearance of fresh Mori fructus at the early stage and late stage of black fruit.
Figure 2 is the appearance of the product obtained using the process scheme of example 1.
Figure 3 is the appearance of the product obtained using the process scheme of example 3.
Figure 4 is the appearance of the product obtained using the process scheme of comparative example 3.
Figure 5 is the appearance of the product obtained using the process scheme of comparative example 9.
Fig. 6 is the appearance of the product obtained by the drying process of drying in the sun.
The specific implementation mode is as follows:
it should be noted that the fresh mulberry fruit used in the examples of the present invention was obtained from cooperative planting sites of Guangdong Ming Sheng pharmaceutical industry GmbH in Yanbian county, panzhihua city, sichuan province. The saline county is in a unique subtropical dry valley climate, the altitude is more than 900 meters, the temperature difference between day and night is large, the fresh mulberry fruits obtained by planting are pollution-free, the sugar content is sufficient, the taste is extra sweet, the fruits are large and full, the pulp is thick and solid, the color is black and bright, and the ecological original taste is kept. The present invention will be described in further detail with reference to the following examples with reference to the accompanying drawings, but the embodiments of the invention are not limited thereto.
Test 1: selection of fresh Mulberry fruit
The new period of mulberry production is from 4 to 6 months of each year. The fruits obtained from early 4 to early 5 months (early prenatal period) and from early 6 to late 6 months (late prenatal period) are generally thin and small, low in sweetness and sour and hard. And the fruits obtained from early 5 months to late 5 months (midnew birth period) are generally full and have high sweetness. As the maturity increases, the mulberry color changes from cyan to red and purplish black in sequence. The mulberry fruits at the red fruit stage, the early stage and the later stage of the black fruit are collected and evaluated in the new production middle stage of the mulberry. The results are shown in Table 1.
TABLE 1 characteristics of Mori fructus at different stages of new and middle stages of production
From the results in table 1, it can be found that the best harvest time of fresh morous alba is black fruit (early and late), the fruit is bigger and the sweetness is high. Compared with the early stage of black fruits, the mulberry fruits at the later stage of the black fruits are extremely easy to break and seep due to high maturity in the picking and post-processing processes. Specifically, as shown in fig. 1, the fresh fruit images at the early and late stages of black fruit are not much different in shape, size and color, but the skin of the mulberry fruit at the late stage is very thin, and juice exudation (white paper staining) can be seen when the mulberry fruit is placed on white paper. After mulberry fruits at the black fruit stage of the new-producing middle stage are picked, the mulberry fruits are immediately stored at the low temperature of-5 ℃ to 5 ℃ and are freeze-dried for no more than 15 hours.
Example 1
A mulberry vacuum freeze-drying processing technology specifically comprises the following steps:
(1) Selecting mulberry raw materials: selecting black mulberry fruits which are picked in the early stage of black fruits in the new and middle producing period, have fruit stalks, are not damaged and have no diseases and insect pests.
(2) Pretreatment: placing the selected fresh mulberry fruit into ozone water with the concentration of 2.0mg/L, blowing, cleaning and soaking for 3min, and taking out clear water to clean for 2 times.
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 13kg/m 2 Placing into a freeze dryer, cooling to-15 deg.C for 20min, and keeping the temperature for 25min; cooling to-33 deg.C within 12min, and maintaining for 25min; then annealing treatment is carried out, the temperature is raised to-21 ℃ within 15min, and the temperature is kept for 30min; finally, the temperature is reduced to minus 33 ℃ within 15min and the temperature is preserved for 20min.
(4) The sublimation drying is as follows: starting a cold trap system, keeping the vacuum degree at 35Pa when the temperature of a cold trap is lower than-48 ℃, heating the plate to 30 ℃ in 30min, and keeping the temperature for 75min; heating the plate to 48 deg.C in 12min, controlling the vacuum degree at 70Pa, and maintaining the temperature for 350min.
(5) The analysis and drying are as follows: heating the heating plate to 65 ℃ within 18min, controlling the vacuum degree to be 20Pa, and keeping the temperature for 200min; the temperature of the heating plate is reduced to 48 ℃ within 35min, the vacuum degree is controlled to be 35Pa, and the temperature is kept for 60min.
And after drying, discharging, detecting that the water content of the material is 3.8%, the finished product rate of the dried fruit is 94.6%, and the total time spent on pre-freezing and drying is 942min, wherein the obtained finished product is shown in figure 2.
Example 2
A vacuum freeze-drying processing technology for mulberry comprises the following steps:
(1) Selecting mulberry raw materials: selecting black mulberries which are picked in the early stage of black fruits in the new production middle period, have no damage and no plant diseases and insect pests, and have the length of 2.5 cm-3.2 cm and the width of 1.2 cm-1.6 cm. The rest of the procedure was the same as in example 1.
And after drying, discharging, and detecting that the water content of the material is 4.3% and the yield of the dried fruits is 96.2%.
Example 3
A vacuum freeze-drying processing technology for mulberry comprises the following steps:
(1) Selecting mulberry raw materials: selecting black mulberry fruits which are picked at the later stage of black fruits in the new and middle producing period, have fruit stalks, are not damaged, and have no diseases and insect pests.
(2) Pretreatment: placing the selected fresh mulberry fruit into ozone water with the concentration of 1.0mg/L, blowing, cleaning and soaking for 2min, and taking out clear water to clean for 2 times.
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 12kg/m 2 Placing into a freeze dryer, cooling to-18 deg.C for 25min, and keeping the temperature for 30min; cooling to-34 deg.C within 15min, and maintaining for 30min; then annealing treatment is carried out, the temperature is raised to-22 ℃ within 18min, and the temperature is kept for 35min; finally, the temperature is reduced to minus 34 ℃ within 20min and the temperature is kept for 25min.
(3) The sublimation drying comprises the following steps: starting a cold trap system, keeping the vacuum degree at 40Pa when the temperature of the cold trap is lower than-48 ℃, heating the plate to 28 ℃ in 40min, and keeping the temperature for 70min; heating the plate to 48 deg.C in 10min, controlling the vacuum degree at 75Pa, and maintaining the temperature for 340min.
(4) The analysis and drying are as follows: heating the heating plate to 62 ℃ within 20min, controlling the vacuum degree to be 20Pa, and keeping the temperature for 220min; the heating plate is cooled to 48 ℃ within 30min, the vacuum degree is controlled to be 40Pa, and the temperature is kept for 65min.
And after drying is finished, discharging, and detecting that the water content of the material is 4.0% and the finished product rate of dried fruits is 87.5%. The total time spent for pre-freezing and drying was 993min, and the final product was shown in FIG. 3.
Example 4
A vacuum freeze-drying processing technology for mulberry comprises the following steps:
(1) Selecting mulberry raw materials: selecting black mulberries which are picked at the later stage of black fruits in the new and middle producing period, have fruit stalks, are not damaged, have no plant diseases and insect pests, and have the length of 2.5 cm-3.2 cm and the width of 1.2 cm-1.6 cm. The rest of the procedure was the same as in example 3.
And after drying, discharging, and detecting that the water content of the material is 4.8% and the yield of dried fruits is 88.3%.
From the results of examples 1-4, it can be seen that the process of the present invention is suitable for the processing of black fruit in the early and late stages, and can ensure a high yield.
Comparative example 1 (whether ozone water cleaning is adopted)
A mulberry vacuum freeze-drying processing technology comprises the following steps:
(2) Pretreatment: and (3) putting the selected fresh mulberry fruits into clear water, blowing, cleaning and soaking for 5min, and taking out the clear water and cleaning for 2 times. The rest of the procedure was the same as in example 1.
And after drying, discharging, and detecting that the water content of the material is 4.7% and the finished product rate of dried fruits is 80.1%.
And (3) knotting: the pretreatment does not use ozone water for cleaning, and the yield is obviously reduced. This indicates that the residual impurities on the surface of fresh mulberry can be effectively removed by soaking with ozone water, and the small amount of sugar adhered on the surface of mulberry can be reduced, and the bonding of mulberry in the pre-freezing process can be reduced.
Comparative example 2 (Pre-freezing process direct rapid cooling)
A mulberry vacuum freeze-drying processing technology comprises the following steps:
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 13kg/m 2 The mixture is put into a freeze dryer, the temperature is reduced to-35 ℃ within 20min, and the temperature is kept for 180min (the temperature is kept for ensuring that the materials are completely frozen.) the other steps are the same as the example 1.
And after drying is finished, discharging, detecting that the water content of the material is 6.4%, wherein the total time spent on pre-freezing and drying is 980min, and the finished product rate of the dried fruits is 72.4%.
Comparative example 3 (Pre-freezing process direct slow cooling)
A mulberry vacuum freeze-drying processing technology specifically comprises the following steps:
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 13kg/m 2 And putting into a freeze dryer, cooling to-35 deg.C within 100min, and keeping the temperature for 200min. (the incubation time was such that the material was completely frozen.) the procedure was the same as in example 1.
After drying, discharging, detecting the water content of the material to be 7.1%, wherein the total time of pre-freezing and drying is 1080min, the yield of the dried fruits is 70.9%, and the appearance of the obtained finished product is shown in figure 4.
And (4) summarizing: from comparative examples 2 and 3, it can be seen that in the pre-freezing process, the moisture content of the finished product is higher than that of the invention by adopting a direct rapid cooling means (comparative example 3) and a slow cooling means (comparative example 4), and the yield is obviously reduced.
Comparative example 4 (vacuum degree of sublimation process without step control)
A vacuum freeze-drying processing technology for mulberry comprises the following steps:
(4) The sublimation drying is as follows: starting a cold trap system, keeping the vacuum degree at 40Pa when the temperature of the cold trap is lower than-48 ℃, heating the plate to 30 ℃ within 30min, and keeping the temperature for 75min; the heating plate is heated to 48 ℃ in 12min, and the temperature is kept for 350min. The vacuum was maintained at 40Pa during this period. The rest of the procedure was the same as in example 1.
And after drying, discharging, and detecting that the water content of the material is 8.1% and the yield of the dried fruits is 82.1%.
Comparative example 5 (vacuum degree step-by-step control in analytical process)
A vacuum freeze-drying processing technology for mulberry comprises the following steps:
(5) The analysis and drying are as follows: heating to 65 deg.C in 18min with a heating plate, and maintaining for 200min; the heating plate is cooled to 48 ℃ in 35min, and the temperature is kept for 60min. The vacuum was maintained at 70Pa at this stage. The rest of the procedure was the same as in example 1.
And after drying, discharging, and detecting that the water content of the material is 8.8% and the finished product rate of the dried fruits is 80.5%.
Comparative example 6 (sublimation process step-less insulation)
A vacuum freeze-drying processing technology for mulberry comprises the following steps:
(4) The sublimation drying is as follows: and starting a cold trap system, keeping the vacuum degree at 35Pa when the temperature of the cold trap is lower than-48 ℃, heating the heating plate to 35 ℃ in 35min, and keeping the temperature for 600min (the heat preservation time is based on that the water content of the material reaches 10-15%). Heating the heating plate to 48 deg.C within 12min, maintaining the vacuum degree at 70Pa, and maintaining the temperature for 0min. The rest of the procedure was the same as in example 1.
And after drying, discharging, detecting that the water content of the material is 4.4%, the yield of the dried fruits is 68.5%, and the total time spent on pre-freezing and drying is 1122min.
Comparative example 7 (resolution process insulation step by step)
A mulberry vacuum freeze-drying processing technology comprises the following steps:
(5) The analysis and drying are as follows: heating the heating plate to 65 ℃ within 18min, controlling the vacuum degree to be 20Pa, and keeping the temperature for 280min (the heat preservation time is based on the water content of the material being less than 5%). The temperature of the heating plate is reduced to 48 ℃ within 35min, the vacuum degree is controlled to be 35Pa, and the temperature is kept for 0min. The rest of the procedure was the same as in example 1.
And after drying, discharging, detecting that the water content of the material is 4.7%, the finished product rate of the dried fruits is 62.7%, and the total time spent on pre-freezing and drying is 962min.
And (3) knotting: from comparative examples 4 to 7, it can be seen that the quality of the mulberry product can be affected by controlling the vacuum degree during the drying process. Specifically, the vacuum degree in the sublimation (comparative 4) and desorption drying (comparative 5) processes is not regulated in stages, the yield is respectively reduced to 82.1% and 80.5%, and in addition, the moisture removal condition is poor, and the moisture content is 8.1% and 8.8%. When heating is not carried out step-by-step heat preservation in the processes of sublimation (comparison 6) and desorption drying (comparison 7), although the moisture of the finished product can reach less than 5%, the yield is obviously reduced and only reaches 68.5% and 62.7%, and the loss of raw materials is large.
COMPARATIVE EXAMPLE 8 (REFERENCE TO EXAMPLE 1 in CN 104095029A)
A mulberry vacuum freeze-drying processing technology refers to the prefreezing and drying process conditions in example 1 in CN104095029A, and comprises the following steps:
(3) Pre-freezing: draining the cleaned Mori fructus to remove surface water, and dishing in an amount of 13kg/m 2 Placing into a freeze dryer, cooling to-25 deg.C for 30min, freezing for 120min, and further cooling to-30 deg.C for 120min for 4 min. (complete freezing of the Material)
(4) Sublimation drying: starting a cold trap system, keeping the vacuum degree at 10Pa when the temperature of the cold trap is lower than-48 ℃, heating a heating plate to 30 ℃ within 30min, and keeping the temperature for 1200min (20 h).
(5) And (3) resolving and drying: heating the heating plate to 50 deg.C for 35min, controlling vacuum degree at 50Pa, and maintaining the temperature for 480min. The rest of the procedure was the same as in example 1.
And after drying, discharging, and detecting that the water content of the material is 5.2% and the yield of dried fruits is 85.4%. The total time spent prefreezing and drying was 2019min.
COMPARATIVE EXAMPLE 9 (CN 104095029A, EXAMPLE 1)
A mulberry vacuum freeze-drying processing technology refers to the prefreezing and drying process conditions in example 1 in CN104095029A, and comprises the following steps:
(3) Pre-freezing: draining the cleaned Mori fructus to remove surface water, and dishing in an amount of 13kg/m 2 Placing into a freeze dryer, cooling to-25 deg.C within 30min, freezing for 120min, and further cooling to-30 deg.C within 4min, and freezing for 140min. (subject to complete freezing of the material)
(4) Sublimation drying: starting a cold trap system, keeping the vacuum degree at 10Pa when the temperature of the cold trap is lower than-48 ℃, heating a heating plate to 30 ℃ within 30min, and keeping the temperature for 1200min (20 h).
(5) And (3) resolving and drying: heating the heating plate to 50 deg.C for 35min, controlling vacuum degree at 50Pa, and maintaining the temperature for 480min. The rest of the procedure was the same as in example 3.
And after drying, discharging, and detecting that the water content of the material is 4.8% and the yield of dried fruits is 45.4%. The total time spent for prefreezing and drying was 2039min, and the final product was obtained as shown in FIG. 5.
And (3) knotting: the inventor finds that the process method in the prior art (CN 104095029A) has relatively good effect on the mulberry in the early stage of the black fruit (comparative example 8), and the yield is 85.4%, but still lower than that of example 1 (94.6%) of the invention. The yield of the mulberry at the later stage of the black fruit is low, and is only 45.4% (for example 9). In addition, the drying process of the prior art takes longer than the process of the present invention.
Test 2:
the products obtained in the above examples and comparative examples were subjected to the performance test, and the results are shown in Table 2. Wherein, the detection of the anthocyanin content refers to a high performance liquid chromatography for determining the anthocyanin in plant-derived food of agricultural industry standard NY/T2640-2014 of the people's republic of China; the vitamin C content detection refers to the determination of ascorbic acid in food products of national food safety standards GB 5009.86-2016 of the people's republic of China.
Table 2 the products obtained in the examples and comparative examples were subjected to performance evaluation
From the results in table 2, it can be seen that the freeze-dried mulberries obtained by the process optimization in experimental groups 1-4 have good color, basically no brown stain in appearance, strong fragrance and no obvious difference compared with fresh mulberries, and the obtained dried mulberries have the original color and original taste effects compared with the original fresh mulberries. The anthocyanidin and vitamin C in dried Mori fructus are reduced compared with fresh Mori fructus. The reason for the reduced vitamin C content may be on the one hand the loss due to reaction with oxygen in the environment; on the other hand, it may be due to an enzymatic reaction. The reason for the decrease in the anthocyanin content may be that mulberry suffers from oxidative denaturation of anthocyanin under the influence of air that contacts during the lyophilization process. It has been shown that anthocyanins are water-soluble substances, known as flavonoids, which are chemically unstable. The content of the anthocyanin is closely related to the stability of the structure of the substance, the temperature, the air pressure and other conditions of the freeze-drying process. Mulberry anthocyanins are degraded to varying degrees when heated at high temperatures and are reduced. Therefore, the process parameters during the lyophilization process have an important influence on the content change of the anthocyanin and the vitamin C. Test results show that the optimized freeze-drying process is adopted, and compared with fresh fruits, the content loss of anthocyanin and vitamin C is minimum.
Test 3: mulberry character analysis by different drying modes
Selecting Mori fructus as raw material according to the method of example 1, draining surface water from cleaned Mori fructus, and dishing at amount of 15kg/m 2 . The treatment was then carried out according to the drying conditions in Table 3.
Table 3: drying method of different mulberries
As can be seen from the results in table 3, the dried morous alba obtained by the conventional drying method has a low yield, a large difference between the color and the fresh fruit, incomplete morphology, and severe shrinkage. The product obtained by the freeze-drying process of the embodiment 1 in the invention has low water content, smooth fruit surface and small shrinkage degree, and the color of the product is close to that of fresh mulberry.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A mulberry vacuum freeze-drying processing technology is characterized by comprising the following steps:
(1) Selecting raw materials: selecting and picking black mulberry with fruit stalks in the new and middle period of production, no damage and no plant diseases and insect pests;
(2) Pretreatment: putting the selected fresh mulberry fruits into ozone water with the concentration of 0.5-3 mg/L for blowing, cleaning and soaking for 2-5 min, and taking out clear water for cleaning for 1-3 times;
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 12kg/m 2 ～15kg/m 2 Putting the mixture into a freeze dryer, cooling the mixture to minus 5 ℃ to minus 20 ℃ within 10min to 30min, and carrying out super-cooling and heat preservation for 10min to 40min; then cooling to minus 30 ℃ to minus 35 ℃ within 5min to 20min, and keeping for 10min to 40min; then annealing treatment is carried out, namely the temperature is raised to minus 18 ℃ to minus 24 ℃ within 8min to 25min, and the temperature is kept for 20min to 40min; finally, the temperature is reduced to minus 30 ℃ to minus 35 ℃ within 5min to 25min, and the temperature is preserved for 10min to 30min;
(4) Sublimation drying: starting a cold trap system, keeping the vacuum degree at 30-40 Pa when the temperature of the cold trap is lower than-48 ℃, heating the plate to 25-33 ℃ within 20-50 min, and keeping the temperature for 50-100 min; then controlling the vacuum degree to be 60 Pa-90 Pa, heating the heating plate to 44-56 ℃ within 5-20 min, and preserving the heat for 300-400 min;
(5) And (3) resolving and drying: heating the heating plate to 60-68 ℃ within 12-26 min, controlling the vacuum degree to 10-30 Pa, and keeping the temperature for 160-240 min; then the heating plate is cooled to 44-54 ℃ within 25-45 min, the vacuum degree is controlled to be 20-50 Pa, and the temperature is kept for 45-70 min.
2. The vacuum freeze-drying process of mulberry according to claim 1, wherein the pre-freezing step is: firstly, cooling to-8 to-18 ℃ within 15 to 25min, and carrying out supercooling and heat preservation for 20 to 30min; then cooling to-32 to-34 ℃ within 10min to 15min, and keeping the temperature for 20min to 30min; then heating to-20 to-22 ℃ within 12 to 18min and keeping the temperature for 25 to 35min; finally, the temperature is reduced to minus 32 ℃ to minus 34 ℃ within 10min to 20min, and the temperature is preserved for 15min to 25min.
3. The vacuum freeze-drying process for mulberry according to claim 1, wherein the sublimation drying step is: when the temperature of the cold trap is lower than minus 48 ℃, keeping the vacuum degree at 32Pa to 38Pa, heating the heating plate to 28 ℃ to 32 ℃ within 30min to 40min, and preserving the heat for 65min to 75min; then the heating plate is heated to 46-52 ℃ within 10-15 min, the vacuum degree is controlled to 65-75 Pa, and the temperature is kept for 320-380 min.
4. The vacuum freeze-drying process for mulberry according to claim 1, wherein the analytical drying step is: heating the heating plate to 62-66 ℃ within 14-22 min, controlling the vacuum degree to 15-25 Pa, and keeping the temperature for 180-220 min; the temperature of the heating plate is reduced to 46-52 ℃ within 30-40 min, the vacuum degree is controlled to be 30-40 Pa, and the temperature is kept for 50-65 min.
5. The vacuum freeze-drying process of mulberry according to claim 1, wherein the black mulberry is fresh mulberry in black stage, preferably mulberry in early stage of black stage.
6. The vacuum freeze-drying process of mulberry according to claim 1 or 5, wherein said black mulberry is preferably black mulberry having length of 2.5cm to 3.2cm and width of 1.2cm to 1.6 cm.
7. The vacuum freeze-drying process of mulberry according to claim 1, further comprising the steps of discharging and packaging: after the freeze-drying is finished, discharging in a nitrogen environment at the temperature of 15-20 ℃, and filling nitrogen to hermetically seal and package by adopting a pure aluminum packaging material.
8. A mulberry vacuum freeze-drying processing technology is characterized by comprising the following steps:
(1) Selecting mulberry raw materials: selecting black mulberry fruits which are picked in the early stage of black fruits in the new and middle producing period, have fruit stalks, are not damaged and have no diseases and insect pests;
(2) Pretreatment: placing the selected fresh mulberry fruit into ozone water with the concentration of 2.0mg/L, blowing, cleaning and soaking for 3min, taking out clear water, and cleaning for 2 times;
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 13kg/m 2 Placing into a freeze dryer, cooling to-15 deg.C within 20min, and keeping the temperature for 25min; cooling to-33 deg.C within 12min, and maintaining for 25min; then annealing treatment is carried out, the temperature is raised to-21 ℃ within 15min, and the temperature is kept for 30min; finally, cooling to-33 ℃ within 15min and preserving the temperature for 20min;
(4) Sublimation drying: starting a cold trap system, keeping the vacuum degree at 35Pa when the temperature of the cold trap is lower than-48 ℃, heating the plate to 30 ℃ within 30min, and keeping the temperature for 75min; heating the heating plate to 48 ℃ within 12min, controlling the vacuum degree to 70Pa, and keeping the temperature for 350min;
(5) And (3) resolving and drying: heating the heating plate to 65 ℃ within 18min, controlling the vacuum degree to be 20Pa, and keeping the temperature for 200min; then the heating plate is cooled to 48 ℃ within 35min, the vacuum degree is controlled to be 35Pa, and the temperature is kept for 60min.
9. A mulberry vacuum freeze-drying processing technology is characterized by comprising the following steps:
(1) Selecting mulberry raw materials: selecting black mulberry which is picked in the early stage of black fruit in the new and middle producing period, has no damage and insect pest, and has mulberry stems, no damage, no disease and insect pest, the length of the mulberry is 2.5 cm-3.2 cm, and the width of the mulberry is 1.2 cm-1.6 cm;
(2) Pretreatment: putting the selected fresh mulberry fruits into ozone water with the concentration of 2.0mg/L, blowing, cleaning and soaking for 3min, taking out clear water, and cleaning for 2 times;
(3) Pre-freezing: draining the surface water of the washed mulberry and loading the mulberry into a tray, wherein the loading amount is 13kg/m 2 Placing into a freeze dryer, cooling to-15 deg.C within 20min, and performing supercooling and heat preservation for 25min; cooling to-33 deg.C within 12min, and maintaining for 25min; then annealing treatment is carried out, the temperature is raised to-21 ℃ within 15min, and the temperature is kept for 30min; finally, cooling to-33 ℃ within 15min and preserving the temperature for 20min;
(4) Sublimation drying: starting a cold trap system, keeping the vacuum degree at 35Pa when the temperature of the cold trap is lower than-48 ℃, heating the plate to 30 ℃ within 30min, and keeping the temperature for 75min; heating the heating plate to 48 ℃ within 12min, controlling the vacuum degree to 70Pa, and keeping the temperature for 350min;
(5) And (3) resolving and drying: heating the heating plate to 65 ℃ within 18min, controlling the vacuum degree to be 20Pa, and keeping the temperature for 200min; then the heating plate is cooled to 48 ℃ within 35min, the vacuum degree is controlled to be 35Pa, and the temperature is kept for 60min.
10. Use of the vacuum freeze-drying process of mulberry according to any one of claims 1 to 9 for preparing freeze-dried products of whole mulberry.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102613283A (en) * | 2011-01-26 | 2012-08-01 | 深圳职业技术学院 | Fruit vacuum freeze drying method |
| CN104095029A (en) * | 2014-07-10 | 2014-10-15 | 青岛大学 | Vacuum frozen and dried mulberry product and preparation technology thereof |
| CN105192051A (en) * | 2015-09-30 | 2015-12-30 | 安徽韵沣农业发展有限公司 | Low-temperature mulberry drying treatment process |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102613283A (en) * | 2011-01-26 | 2012-08-01 | 深圳职业技术学院 | Fruit vacuum freeze drying method |
| CN104095029A (en) * | 2014-07-10 | 2014-10-15 | 青岛大学 | Vacuum frozen and dried mulberry product and preparation technology thereof |
| CN105192051A (en) * | 2015-09-30 | 2015-12-30 | 安徽韵沣农业发展有限公司 | Low-temperature mulberry drying treatment process |
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