CN117243256A

CN117243256A - Passiflora edulis pericarp polysaccharide low-fat yoghourt and preparation method thereof

Info

Publication number: CN117243256A
Application number: CN202311190296.3A
Authority: CN
Inventors: 闫景坤; 吴珞帮; 李琳; 李垄清; 刘丰源
Original assignee: Dongguan University of Technology
Current assignee: Dongguan University of Technology
Priority date: 2023-09-15
Filing date: 2023-09-15
Publication date: 2023-12-19
Anticipated expiration: 2043-09-15

Abstract

The invention discloses passion fruit peel polysaccharide low-fat yoghourt and a preparation method thereof, wherein raw materials including 0.05-1.0% of passion fruit peel polysaccharide, 0.005-0.05% of a starter, 85-95% of low-fat milk and the balance of water are mixed and fermented to prepare yoghourt; the preparation of passion fruit peel polysaccharide comprises the following steps: weighing passion fruit peel, adding ammonium sulfate solution, mixing, crushing, intermittently ultrasonic treating to obtain passion fruit peel slurry, microwave treating, and centrifuging to obtain supernatant; regulating the pH value of the supernatant, mixing with tertiary butanol, stirring, centrifuging to form three phases, and collecting ammonium sulfate phase solution; dialyzing the ammonium sulfate phase solution with a dialysis bag with molecular cutoff of 3kDa, and drying to obtain passion fruit peel polysaccharide. The yoghourt prepared by the method can effectively solve the problems of poor mouthfeel, poor texture, whey precipitation and insufficient flavor of the low-fat yoghourt, and has the advantages of simple preparation method, low cost and short production period.

Description

Passiflora edulis pericarp polysaccharide low-fat yoghourt and preparation method thereof

Technical Field

The invention relates to the technical field of dairy product processing, and mainly relates to passion fruit peel polysaccharide low-fat yoghourt and a preparation method thereof.

Background

Along with the rapid development of the economy and society in China, people put forward higher requirements on healthy life. The healthy and healthy diet concept has become a new trend in modern life. Under the brand new consumer upgrade current, the updating iteration of the natural ingredient, low-fat, high-quality and good-taste diet product is promoted.

Yoghurt is a fermented drink which is known for its unique flavor and rich nutrition. In the fermentation process of the yoghourt, the cross-linking effect of the fat globules and the proteins ensures that the whole yoghourt has good hardness and rheological property, and endows the yoghourt with smooth and rich taste, thus being favored by consumers. The whole yoghurt contains higher milk fat, and excessive intake can cause fat accumulation, increased blood consistency and blocked blood circulation, thereby causing the health problems of obesity, hypertension, coronary heart disease and the like and seriously affecting the health of people. However, the reduction of milk fat content in low fat yogurt can lead to texture defects, which make the tissue structure of low fat yogurt thin and whey separate out, affect the desire of consumers to purchase, and the product is not accepted by the market.

Passion flower, also known as passion fruit, passion fruit and Brazil fruit, is a perennial evergreen vine plant which is widely planted in tropical and subtropical areas of China. The passion fruit can be processed to produce a large amount of pericarps, and if the passion fruit can be comprehensively utilized, the industrial chain of the passion fruit can be prolonged. The passion fruit peel is rich in functional compounds such as flavonoids, polyphenols, polysaccharides and the like, and is helpful for resisting damage caused by free radicals, promoting intestinal health, preventing constipation and reducing cholesterol level. The passion fruit peel soluble polysaccharide is a natural food additive, and is added into food media, so that the passion fruit peel soluble polysaccharide not only can provide rich dietary fibers, delay the emptying time of gastrointestinal tracts, enhance satiety, reduce food intake and control weight, but also has the characteristics of low fat, thickening, emulsifying and the like, and is a potential fat substitute.

At present, in the domestic technology for producing low-fat yoghourt, fruit and vegetable powder is mainly added as a fat substitute to stabilize the low-fat yoghourt. Tang Zhenxing et al, U.S. patent application Ser. No. 08/30, entitled "Linseed reduced fat acid milk nutritional meal and method for making same" (publication No. CN 110178896A); zhang Yinghua et al, 04/10 th 2020, filed under the name of "low-fat yoghourt prepared by combining asparagus whole powder with akebia trifoliate pectin and preparation method thereof" (publication number: CN 201911269417.7); zhao Xinhuai et al, 10/16/2020, filed under the name "a processing method of defatted yogurt of high hardness yam" (publication No. CN 111771973A). The grape seeds, the flaxseeds, the asparagus powder, the Chinese yam and the like are added into the low-fat yoghourt, and the additives are poor in water solubility, coarse in fiber, poor in taste, weak in functionality and low in content of soluble dietary fiber. In addition, the existing yogurt production has the problems that the dosage of the leavening agent is generally high and the production cost is greatly increased. For example, chinese patent CN102524396A discloses a stirred pleurotus eryngii nutritional yoghurt drink and a preparation method thereof, wherein pleurotus eryngii polysaccharide is taken as a main yoghurt variety, a starter is a mixture of two strains of streptococcus thermophilus and lactobacillus delbrueckii, and the addition amount of the starter is 3-8%.

Disclosure of Invention

Aiming at the problems in the preparation of the low-fat yoghourt, the invention provides a preparation method of passion fruit peel polysaccharide low-fat yoghourt, which is characterized in that passion fruit peel polysaccharide is added into the low-fat yoghourt for fermentation, so that the mouthfeel, the tissue state, the sensory flavor and the storage stability of the low-fat yoghourt are improved.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

the preparation method of the passion fruit peel polysaccharide low-fat yoghourt is characterized by comprising the following raw materials in percentage by weight: 0.05-1.0% of passion fruit peel polysaccharide, 0.005-0.05% of starter, 85-95% of low-fat milk and the balance of water; the raw materials are mixed and fermented to prepare the passion fruit peel polysaccharide low-fat yoghourt;

the passion fruit peel polysaccharide is prepared by the following method:

(1) Weighing passion fruit peel, adding ammonium sulfate solution, mixing, and crushing to obtain passion fruit peel slurry;

(2) Intermittently ultrasonic treating the passion fruit peel slurry, then carrying out microwave treatment, and centrifuging the treated slurry to obtain a supernatant;

(3) Regulating the pH value of the supernatant to 5.4+/-0.4, mixing with tertiary butanol, stirring, centrifuging to form three phases, and collecting ammonium sulfate phase solution;

(4) Dialyzing the ammonium sulfate phase solution with a dialysis bag with molecular cutoff of 3kDa, and drying to obtain passion fruit peel polysaccharide.

Preferably, the passion fruit peel in the step (1) is mixed with an ammonium sulfate solution according to a material-liquid ratio of 1 (1-5) g/mL, and the mass concentration of the ammonium sulfate solution is 10-30%.

Preferably, the batch sonication conditions of step (2) are: the ultrasonic frequency is 20+/-10 kHz, the ultrasonic power is 400+/-100W, the ultrasonic time is 30+/-10 min, the working mode is 1-5 s on, and the working mode is 1-5 s off; the microwave treatment conditions are as follows: the microwave frequency is 2450+/-100 MHz, the microwave power is 600+/-100W, and the microwave time is 10+/-5 min.

Preferably, the centrifugation conditions of step (2) are: centrifuging at 4000+ -1000 r/min for 10+ -5 min; the centrifugation conditions in the step (3) are as follows: centrifuging at 4000+ -1000 r/min for 20+ -10 min; the volume ratio of the supernatant fluid to the tertiary butanol in the step (3) is 1 (0.5-5.0).

Preferably, the raw materials include: 0.20+/-0.1% of passion fruit peel polysaccharide, 0.02+/-0.01% of starter, 90+/-3% of low-fat milk and the balance of water; the fat content of the low-fat milk is not more than 1.3%.

Preferably, the starter is lactobacillus bulgaricus (Lactobacillus bulgaricus), streptococcus thermophilus (Streptococcus thermophilus) or a combination of both.

Preferably, the raw material mixed fermentation comprises the following steps:

a. dissolving passion fruit peel polysaccharide in water to obtain passion fruit peel polysaccharide solution with mass concentration of 0.05-0.5%;

b. mixing passion fruit peel polysaccharide solution with low-fat milk, homogenizing, dispersing, sterilizing, and cooling to obtain raw material liquid;

c. and adding the starter into the raw material liquid, uniformly stirring, and fermenting to obtain the passion fruit peel polysaccharide low-fat yoghourt.

Preferably, the homogenizing and dispersing condition in the step b is that the rotating speed is 10000+/-2000 r/min, and the homogenizing and dispersing time is 5+/-2 min; the sterilization mode is high-temperature water bath sterilization, the sterilization temperature is 95+/-5 ℃, and the sterilization time is 5+/-2 min; after high temperature sterilization, the cooling temperature is 42+/-5 ℃.

Preferably, the stirring in the step c is magnetic stirring, the stirring time is 30+/-10 min, and the stirring temperature is 25+/-5 ℃; the fermentation temperature is 38+/-2 ℃, and the fermentation time is 6+/-2 hours; the starter is a mixture of lactobacillus bulgaricus and streptococcus thermophilus in a mass ratio of 1:1.

Preferably, the fermentation end point pH value of step c is 4.6+ -0.4, and the acidity is 80+ -5 DEG T.

Preferably, the mass concentration of the passion fruit peel polysaccharide solution in the step a is 0.20%.

Compared with the prior art, the invention has the following beneficial effects:

(1) The starter is a mixed strain starter compounded by lactobacillus bulgaricus, streptococcus thermophilus and the like in mass ratio, and is purchased from Hubei Angel biosystems, inc. The mixed strain starter can refine nutrient substances in milk, so that the yoghourt can be fermented more fully, the fermentation time of the yoghourt can be shortened effectively, and special flavor is given to the yoghourt. In addition, the mixed strain starter can promote secretion of extracellular polysaccharide of lactobacillus, effectively improve the texture characteristic of the yoghurt, endow the yoghurt with fine and smooth mouthfeel, improve the stability and water retention of the yoghurt, reduce the use amount of the stabilizer in production of the yoghurt, and make the yoghurt more thick and fragrant.

(2) The passion fruit peel polysaccharide is extracted from fresh passion fruit peel by a system consisting of tertiary butanol and ammonium sulfate after ultrasonic-microwave sequential treatment, wherein the tertiary butanol can play the roles of alcohol precipitation, protein stabilization and nonpolar pigment dissolution, and the ammonium sulfate plays the roles of dissolving and enriching water-soluble polysaccharide. On the one hand, the passion fruit peel polysaccharide and the mixed strain starter have a synergistic effect, so that the fermentation speed can be further improved, the addition amount of the mixed strain starter can be reduced to below 0.05%, the fermentation time is only required to be 6 hours, and the production cost of the yoghurt is greatly reduced. On the other hand, the passion fruit peel polysaccharide has high yield and purity, and the yoghourt prepared by fermenting the passion fruit peel polysaccharide has good rheological property, texture property and water retention property, and an in-vitro digestion and glycolysis simulation experiment shows that the passion fruit peel polysaccharide has remarkable prebiotic activity.

(3) The passion fruit peel polysaccharide low-fat yoghourt is rich in soluble dietary fibers, and can effectively improve the hardness, cohesiveness and rheological property of low-fat yoghourt. Meanwhile, the passion fruit peel polysaccharide low-fat yogurt has low fat content and low calorie value, has a fat-like thick mouthfeel, has the advantages of promoting lactobacillus proliferation, improving the flavor and taste of the low-fat yogurt and effectively inhibiting whey precipitation in the low-fat yogurt, and is suitable for young people with body building, light eating and weight losing, and is also suitable for people with obesity, hyperlipidemia, hypertension and the like to eat.

Drawings

Fig. 1 is a graph showing pH changes during fermentation of yogurt of example 1 and comparative example 1.

Fig. 2 shows the soluble solids content changes during the fermentation of the yogurt of example 1 and comparative example 1.

FIG. 3 is an infrared spectrum of yogurt prepared in example 1 (A) and comparative example 1 (B).

Figure 4 shows the water retention of yoghurt during fermentation of example 1 and comparative example 1.

Fig. 5 is a graph showing apparent viscosity (a), storage modulus and loss modulus change (B) of yogurt produced in example 1 and comparative example 1.

FIG. 6 is a scanning electron micrograph (X200) of yogurt prepared in example 1 (A) and comparative example 1 (B).

FIG. 7 is a thermal graph showing the relative amounts of flavor compounds in the yogurt prepared in example 1 and comparative example 1.

Fig. 8 is an electronic tongue radar chart of the yogurt prepared in example 1 and comparative example 1.

Fig. 9 shows the change in whey precipitation during 21 days of cold storage at 4c of the yogurt prepared in example 1 and comparative example 1.

Detailed Description

The principles and features of the present invention are described below in connection with the following examples, which are set forth to illustrate, but are not to be construed as limiting the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1: preparation of passion fruit peel polysaccharide low-fat yoghourt

1. The preparation of passion fruit peel polysaccharide is carried out according to the following steps:

(1) Washing passion fruit peel, slicing, inactivating enzyme in boiling water for 3min, and cooling to 25 ℃ for standby;

(2) Mixing passion fruit peel with ammonium sulfate solution with the mass concentration of 20% according to the feed-liquid ratio of 1:3g/mL, and breaking the wall for 2 times at 5 min/time by using a wall breaking machine to obtain passion fruit peel slurry;

(3) Performing ultrasonic treatment on passion fruit peel slurry at 25 ℃ under the conditions of ultrasonic frequency of 20kHz, ultrasonic power of 400W, ultrasonic time of 30min and working mode of 2s on/2s off to obtain ultrasonic treated passion fruit peel slurry;

(4) Performing microwave treatment on the ultrasonic-treated passion fruit peel slurry under the conditions of 600W of microwave power and 9min of microwave time to obtain microwave-treated passion fruit slurry;

(5) Centrifuging the passion fruit pulp subjected to microwave treatment at 4000r/min for 10min, collecting supernatant, and regulating the pH value of the supernatant to 5.4;

(6) Mixing the supernatant with pH value of 5.4 with tert-butanol according to the volume ratio of 1:1.5v/v, magnetically stirring for 30min, centrifuging for 20min at 4000r/min to form three phases, and collecting ammonium sulfate phase solution;

(7) Dialyzing the ammonium sulfate phase solution with distilled water with molecular cutoff of 3kDa for 48h, and freeze-drying for 48h to obtain passion fruit peel polysaccharide, wherein the passion fruit peel polysaccharide has total sugar content of 75%, uronic acid content of 68%, methoxy content of 11%, and weight average molecular weight of 363kDa, and is soluble pectin polysaccharide.

2. The preparation method of the passion fruit peel polysaccharide low-fat yoghourt comprises the following steps:

(1) And weighing passion fruit peel polysaccharide, dissolving in deionized water, and magnetically stirring at 25 ℃ to obtain passion fruit peel polysaccharide solution with the mass concentration of 0.20%.

(2) Adding herba Passiflorae Caeruleae pericarp polysaccharide solution into low-fat milk, homogenizing and dispersing in high-speed disperser at 10000r/min for 5min in water bath at 95deg.C for 5min, cooling to 42deg.C to obtain sample solution A, and sealing.

(3) Adding 0.02% fermenting agent into sample solution A, magnetically stirring at 25deg.C for 30min to obtain passion fruit peel polysaccharide sample solution B, and sealing and storing.

(4) And (3) placing the sample liquid B in a constant temperature incubator at 38 ℃ for fermentation for 6 hours, magnetically stirring for 5 minutes after the yoghurt is fermented to the end pH of 4.6, cooling to 25 ℃, sealing, and refrigerating and storing at 4 ℃.

Comparative example 1

Comparative example 1 is substantially the same as example 1 except that: no passion fruit peel polysaccharide was added in comparative example 1.

Experimental example 1

The yogurt obtained in example 1 and comparative example 1 was monitored for pH and soluble solids content during fermentation using a pH meter (S210-S of Metretretolitheli technologies, inc. of Switzerland) and a hand-held refractometer (LB 20T of Ming Rui electronics, inc. of China), respectively, and the results are shown in FIGS. 1 and 2. As is evident from fig. 1, the pH during fermentation of the yoghurt of example 1 was lower than that of comparative example 1, indicating a faster fermentation rate. This has a positive significance for improving the acid production capacity of the microorganisms in the acidification process of the low-fat yogurt. Furthermore, as can be seen from fig. 2, the soluble solids content of the yoghurt of example 1 was lower than that of comparative example 1 after 2 hours of fermentation. This shows that example 1 is able to accelerate the use of nutrients in low fat acid milk by microorganisms.

In summary, the pH and the soluble solids content of the yogurt prepared in example 1 decrease rapidly, which indicates that example 1 can accelerate the use of nutrients in the yogurt by microorganisms, and simultaneously increase the acidification rate of the yogurt and the acid production capacity of the microorganisms.

Experimental example 2

The titratable acidity of the yoghurt prepared in example 1 and comparative example 1 was determined by an indicator titration method, specifically, an absolute ethanol solution of 0.5% phenolphthalein was used as an indicator, and when the titration was to the end point (ph=8.2, the indicator appeared red), the titratable acidity of the yoghurt sample was calculated from the standard lye volume consumed. Measurement of total lactic acid bacteria in yoghurt is carried out according to the method of GB4789.35 national Standard food microbiology test for food safety, 25g of sample is weighed and added into 225mL of sterile physiological saline, 1mL of mixed solution is taken for stepwise dilution, 1mL of each of 2-3 proper continuous dilutions is selected and added into sterile MRS and MC agar plates, and plate counting is carried out after culturing for 72 hours at 36 ℃. The results show that the acidophilus milk prepared in the embodiment 1 of the invention has the acidity of 85.25 ℃ T and the viable count of lactobacillus of 4.91 x 10 ⁸ CFU/g, acidity of yogurt prepared in comparative example 1 was 85.12℃T, viable count of lactic acid bacteria was 3.75×10 ⁸ CFU/g. From the acidity and viable count of lactic acid bacteria in example 1 and comparative example 1, the yogurt prepared in example 1 has high probiotic activity and viable count of lactic acid bacteria>10 ⁶ Acidity requirement>70 DEG T meets the standards of national food safety standard beverage and milk sanitary standard (GB 19302-2010) in China.

Experimental example 3

The yogurt obtained in example 1 and comparative example 1 was subjected to infrared spectroscopy (Nicolet iS50, siemens Feiere Co., U.S.A.) to determine the infrared absorption spectrum of the yogurt, respectively, and 3mg of lyophilized yogurt powder was taken and placed in an infrared spectrometer for ATR scanning, and background subtraction was performed with air as background, with a scanning range of 500cm ^-1 ～4000cm ^-1 Resolution of 4cm ^-1 The number of scans was 32, and the result is shown in fig. 3. As can be seen from FIG. 4, it is located at 3665cm ^-1 Vicinity (CH) ₂ And CH (CH) ₃ ) The absorption peak is shifted and represents 1742cm of protein characteristic region ^-1 (c=o), fatty acid characteristic region 2928cm ^-1 (CH ₂ And CH (CH) ₃ ) Absorption peak vibration was reduced by 1,570cm ^-1 And 1,399 cm ^-1 The vibration of the mixing region containing the fatty acid, protein and polysaccharide vibration bands was reduced, which indicates that in example 1, there was a significant interaction between passion fruit peel polysaccharide and yogurt casein, affecting the structural and functional properties of the yogurt, and further affecting the mouthfeel, stability and organoleptic characteristics of the yogurt.

Experimental example 4

After the yogurt prepared in example 1 and comparative example 1 was refrigerated at 4±1 ℃ for 24 hours, the water retention was measured by a centrifugal weighing method. 2mL of the yoghurt sample is put into a centrifuge tube, and the weight W of the sample is measured ₀ Centrifuging at 3000r/min for 10min, taking out the centrifuge tube, standing for 10min, removing supernatant, and measuring residue weight W ₁ The water holding ratio of the yoghurt is calculated according to the formula: water retention (%) = (W) ₁ /W ₀ ) X 100, the results are shown in fig. 4. As can be seen from fig. 4, the water holding rate of the yogurt prepared in example 1 is significantly higher than that of comparative example 1, and is improved by approximately 13%, the water holding capacity of the low-fat yogurt is enhanced, and whey precipitation is suppressed.

Experimental example 5

The rheological properties of the yoghurt obtained in example 1 and comparative example 1 were determined by means of a bench rheometer (MCR 301, austria An Dongpa Co., ltd.), the yoghurt was added dropwise to a sample bench and filled with PP-40 plates (40 mm diameter, 0.50mm gap) for 0-300s ^-1 Measuring the apparent viscosity change curve at the shear rate; the change curves of storage modulus (G ') and loss modulus (G') at scan frequencies of 0.03-10rad/s were determined using a PP-40 plate over the linear viscoelastic region (scan frequency 1Hz, strain 0.3%) and are shown in FIG. 5. The results show that the yogurt of example 1 has a higher apparent viscosity and storage modulus (G') than comparative example 1, indicating that example 1 can promote the viscosity and gel strength of the low-fat yogurt, forming a stiffer, stronger gel network, which is beneficial for increasing the yogurt stability.

Experimental example 6

The apparent morphology of the yogurt prepared in example 1 and comparative example 1 was measured by a table-type scanning electron microscope (COXEM EM-30plus, korean seum limited), and the lyophilized yogurt was fixed on a sample table and sprayed with gold for 1min, and subjected to scanning electron microscope analysis under vacuum conditions, and the result is shown in fig. 6. The results show that the three-dimensional network of the yoghurt of example 1 is more complete, the network is more tightly connected, the tighter network is better able to fix and retain moisture, the disadvantages of breakage, deformation and dehydration are reduced, and the more complete and stable structure enables the yoghurt to retain its original quality and mouthfeel during transportation and storage, as compared to comparative example 1.

Experimental example 7

The color change in the yogurt prepared in example 1 and comparative example 1 was measured by a color difference meter (CM-5, konikoku Meidad Co., ltd., japan). The yogurt prepared in example 1 and comparative example 1 was refrigerated at 4.+ -. 1 ℃ for 24 hours, taken out from the refrigerator at 4 ℃ and stirred well and then left for 30 minutes. Accurately weighing 20.0g of yoghourt sample in a clean disposable glass plate, and slightly shaking to uniformly spread the yoghourt. After the colorimeter is started and preheated for 5min, the colorimeter is respectively calibrated by a standard white board and a blackboard, an emission mode is selected to carry out chromaticity detection on a yoghurt sample, the detection is repeated three times at different positions of a plate, and chromaticity data are expressed as L (brightness), a (red-green intensity) and b (yellow-blue intensity), and delta E= [ (delta L) is used ² +(Δa) ² +(Δb) ² ] ^1/2 The degree of difference in color between example 1 and comparative example 1 was quantified, and the results are shown in table 1. The results show that the brightness is slightly reduced in experimental example 1, the red-green intensity and the yellow-blue intensity are not greatly changed, and the deltae is 3.11 compared with comparative example 1, which shows that there is only a slight difference between comparative example 1 and experimental example 1, experimental example 1 retains the unique hue, saturation and brightness of yogurt, and is visually matched with the color characteristics of the conventional yogurt, so that consumers are more likely to accept the yogurt.

TABLE 1 yogurt color difference Table

Experimental example 8

The yogurt produced in example 1 and comparative example 1 was processed using a laser particle sizer (LS 13320, beckmann coulter Inc. of USA) and a Markov particle sizer (Zethe particle size and Zeta potential of the yogurt were measured by a tasizer Nano ZS, malvern instruments, uk, respectively, to determine the volume-average weighted diameter (D) of the yogurt prepared in example 1 of the present invention _[4,3] ) D of yogurt prepared in comparative example 1 at 24.15 μm and potential of-13.71 mV _[4,3] 13.03 μm and a potential of +2.82mV. From the particle sizes and potentials of the example 1 and the comparative example 1, the yogurt prepared in the example 1 has higher stability.

Experimental example 9

The yogurt produced in example 1 and comparative example 1 was measured for texture characteristics (hardness, consistency, cohesiveness) using a physical property measuring instrument (TA-XTplus, british SMS Co., ltd.) and the yogurt produced in comparative example 1 was measured for hardness of 22.01g, consistency of 151.05g.sec, cohesiveness of 13.54g.sec, hardness of 13.53g, consistency of 103.69g.sec, cohesiveness of 7.46g.sec, and hardness of the yogurt produced in comparative example 1 was measured for 1, with a diameter of a disc probe of 45mm, a probe speed of 1.0mm/s, a test speed of 2.0mm/s, a penetration depth of 20mm, and a surface trigger force of 5g, and the probe was returned to the original position at a speed of 10.0 mm/s. From the hardness, consistency and cohesiveness of example 1 and comparative example 1, the yogurt prepared in example 1 has higher texture characteristics. The hardness is the maximum force in the positive area of the measurement curve, the consistency is the positive area of the measurement curve, and the cohesiveness is the maximum force in the negative area of the measurement curve, all expressed by absolute values.

Experimental example 10

Ion mobility chromatography (GC-IMS, INNO_Concept, german Ann's Utility Co., ltd.) was carried out on the flavor substances of the yogurt obtained in example 1 and comparative example 1, 2.0g of the yogurt sample was placed in a 20mL headspace sample bottle, incubated at 500r/min and 65℃for 20min, 500. Mu.L of the headspace was injected, the sample injection needle temperature was 85℃and analysis was carried out by a gas chromatograph equipped with a chromatographic column FS-SE-54-CB-1 (15 m. Times.0.53 mm), the incubation temperature was 60℃and the carrier gas was N ₂ (purity 99.999%), flow rate: 0-2min, 2mL/min;2-10min, 2-10mL/min;10-20min, 10-100mL/min;20-30min 100-150mL/min, drift tube at N ₂ The temperature was kept at 45℃as a drift gas, and the flow rate was 150mL/min. The relative flavor content thermogram measured by GC-IMS is shown in fig. 7. As can be seen from the figure, the ketone compounds are volatile compounds with the largest proportion in the yoghurt, are important material sources of cheese flavor and milk flavor in the yoghurt, and the 3-hydroxy-2-butanone, 2, 3-pentanedione, 2-butanone, 2-heptanone, cyclohexanone, 2-pentanone, sec-octanone, 6-methyl-5-hepten-2-one and other compounds are all ketone compounds contributing to the yoghurt flavor, wherein compared with comparative example 1, the yoghurt prepared in example 1 contains higher 3-hydroxy-2-butanone (13.85%) and 2, 3-pentanedione (9.36%), and is beneficial to generating mild cream flavor and vanilla flavor; ethyl acetate is the most important volatile ester compound from the esterification reaction of free acid and alcohol, and the yoghurt prepared in example 1 has higher ethyl acetate content and has pleasant sweet taste and fruit flavor; compared with comparative example 1, the relative content of acetaldehyde in the yoghourt prepared in example 1 is increased by 337.86 percent, so that the yoghourt has better fruit fragrance and faint scent; butyric acid is used as a main acid compound, the butyric acid relative content of the yoghurt prepared in the example 1 is increased by 39.60%, and the fruit taste and cheese flavor of the yoghurt are improved. From this, it can be seen that the yogurt prepared in example 1 has a good fruit flavor (acetaldehyde) and milk flavor (butyric acid, 3-hydroxy-2-butanone and 2, 3-pentanedione).

Experimental example 11

The taste of the yogurt prepared in example 1 and comparative example 1 was measured by an electronic tongue system (astm ee II, alpha m.o.s. company), and the sensor array consisted of acid, salty, fresh, bitter, astringent, bitter aftertaste, an electrochemical sensor and 2 Ag/AgCl reference electrodes, and the electronic tongue was activated, calibrated and diagnosed prior to detection, and each sample was determined to collect 5 parallel data. The yogurt was diluted 10 times with distilled water and placed in a sample cup for detection at 25deg.C, and taste intensity data was collected using data processing software carried on the electronic tongue, the results are shown in FIG. 8. As can be seen from the figure, compared with comparative example 1, the yogurt prepared in example 1 has a higher richness and taste value, a lower bitterness value, and lower sour taste, astringency and higher salty taste, and can improve bad mouthfeel, and is more popular.

Experimental example 12

Reference to national food safety standards: the yogurt prepared in example 1 and comparative example 1 was subjected to sensory evaluation under storage conditions of 4 ℃ for 21 days using the standard method of fermented milk (GB 19302-2010), and the sensory evaluation criteria are shown in table 2.

TABLE 2 yogurt sensory evaluation criteria

The organoleptic evaluation and appearance of the yogurt prepared in example 1 and comparative example 1 under refrigeration at 4 ℃ are shown in table 3 and fig. 9. As can be seen from table 3 and fig. 9, the yogurt prepared in example 1 has a better texture, a more uniform distribution, finer curd and better mouthfeel.

Table 3 organoleptic evaluation of yogurt

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, and yet fall within the scope of the invention.

Claims

1. The preparation method of the passion fruit peel polysaccharide low-fat yoghourt is characterized by comprising the following raw materials in percentage by weight: 0.05-1.0% of passion fruit peel polysaccharide, 0.005-0.05% of starter, 85-95% of low-fat milk and the balance of water; the raw materials are mixed and fermented to prepare the passion fruit peel polysaccharide low-fat yoghourt;

the passion fruit peel polysaccharide is prepared by the following method:

2. The preparation method according to claim 1, wherein the passion fruit peel in the step (1) is mixed with an ammonium sulfate solution according to a feed liquid ratio of 1 (1-5) g/mL, and the mass concentration of the ammonium sulfate solution is 10-30%.

3. The method of claim 2, wherein the batch sonication conditions of step (2) are: the ultrasonic frequency is 20+/-10 kHz, the ultrasonic power is 400+/-100W, the ultrasonic time is 30+/-10 min, the working mode is 1-5 s on, and the working mode is 1-5 s off; the microwave treatment conditions are as follows: the microwave frequency is 2450+/-100 MHz, the microwave power is 600+/-100W, and the microwave time is 10+/-5 min.

4. A method according to claim 3, wherein the centrifugation conditions in step (2) are: centrifuging at 4000+ -1000 r/min for 10+ -5 min; the centrifugation conditions in the step (3) are as follows: centrifuging at 4000+ -1000 r/min for 20+ -10 min; the volume ratio of the supernatant fluid to the tertiary butanol in the step (3) is 1 (0.5-5.0).

5. The method according to any one of claims 1 to 4, wherein the raw materials comprise: 0.20+/-0.1% of passion fruit peel polysaccharide, 0.02+/-0.01% of starter, 90+/-3% of low-fat milk and the balance of water; the fat content of the low-fat milk is not more than 1.3%; the starter is lactobacillus bulgaricus (Lactobacillus bulgaricus), streptococcus thermophilus (Streptococcus thermophilus) or a combination of the lactobacillus bulgaricus and the streptococcus thermophilus.

6. The method according to claim 5, wherein the raw material mixed fermentation comprises the steps of:

7. The preparation method according to claim 6, wherein the homogeneous dispersion condition in the step b is a rotation speed of 10000+ -2000 r/min, and a homogeneous dispersion time of 5+ -2 min; the sterilization mode is high-temperature water bath sterilization, the sterilization temperature is 95+/-5 ℃, and the sterilization time is 5+/-2 min; after high temperature sterilization, the cooling temperature is 42+/-5 ℃.

8. The method according to claim 7, wherein the stirring time in step c is 30.+ -. 10min and the stirring temperature is 25.+ -. 5 ℃; the fermentation temperature is 38+/-2 ℃, and the fermentation time is 6+/-2 hours; the starter is a mixture of lactobacillus bulgaricus and streptococcus thermophilus in a mass ratio of 1:1.

9. The process of claim 8, wherein the fermentation in step c is terminated at a pH of 4.6.+ -. 0.4 and an acidity of 80.+ -. 5 ℃.

10. The passion fruit peel polysaccharide low-fat yogurt produced by the method of any one of claims 1 to 9.