Pleurotus geesteranus protein yoghourt and preparation method thereof

Abstract

The invention belongs to the technical field of dairy product processing, and particularly relates to pleurotus geesteranus protein yoghourt and a preparation method thereof. The method comprises the following steps: dissolving skim milk powder and white granulated sugar in water, independently dissolving pleurotus geesteranus protein in water, uniformly mixing the two solutions, and controlling the mass ratio of the skim milk powder to the pleurotus geesteranus protein to be (0: 100)-(99: 1); and then adding lactobacillus bulgaricus for fermentation to obtain the pleurotus geesteranus protein yoghourt. The pleurotus geesteranus protein is adopted to replace skim milk powder, so that the intake of animal protein can be reduced, the nutritional value of food can be improved, the inherent texture problems of high hardness and high viscosity of high-protein yoghourt can be solved, the requirements of people for nutrition, environmental protection and safety are met, and the pleurotus geesteranus protein yoghourt has potential application value in the field of dairy product processing.

Description

Technical Field

[0001] The invention belongs to the technical field of dairy product processing, and particularly relates to a Pleurotus geesteranus protein yogurt and a preparation method thereof. Background Art

[0002] Traditional yogurt refers to a dairy product made from cow's milk through heat-fermentation with lactic acid bacteria such as Lactobacillus bulgaricus and Streptococcus thermophilus. Regular yogurt has a protein content of 2% to 4%, while high-protein yogurt has a protein content of 7% to 12%. However, the dairy industry's environmental burden is increasingly significant, primarily in terms of land and water resource consumption, as well as environmental pollution. Furthermore, traditional yogurt relies on a single protein source, and some consumers are lactose intolerant or allergic to milk protein, making it difficult to meet consumers' demand for diverse nutrition. This unsustainable production model has prompted research into the use of protein resources in yogurt production, offering new avenues for developing more sustainable yogurt products.

[0003] As consumer demand for sustainable, environmentally friendly, and nutritious foods grows, more and more people are turning their attention to non-animal protein yogurt. While many environmentally friendly and nutritious non-animal protein yogurts are currently available on the market, using plant proteins like soy protein, peanut protein, and pea protein as alternatives, the inherent high gelling properties of plant proteins often lead to defects such as high hardness and viscosity when added directly to the yogurt. Therefore, further development of more sustainable and environmentally friendly yogurts that address the texture issues of high-protein yogurt is essential.

[0004] As a sustainable source of edible fungal protein, Pleurotus geesteranus boasts high protein, low fat, and a short production cycle. Rich in essential amino acids, it fully meets human needs, boasts high nutritional value, and possesses diverse biological activities. Furthermore, Pleurotus geesteranus does not contain lactose, cholesterol, or other substances found in milk protein, meeting the needs of those with lactose intolerance and offering a high-quality alternative to animal protein. Therefore, developing new yogurt products using Pleurotus geesteranus protein as a raw material would not only enhance the value of yogurt but also expand its application scenarios. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention proposes a method for preparing Pleurotus geesteranus protein yogurt, which uses Pleurotus geesteranus protein to replace animal protein to prepare a yogurt with high protein, high dietary fiber, low viscosity and low hardness.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a method for preparing Pleurotus geesteranus protein yogurt, the method comprising the following steps:

[0008] S1. Dissolve skimmed milk powder and white sugar in water;

[0009] S2, dissolving Pleurotus geesteranus protein in water;

[0010] S3, mix the two solutions of S1 and S2 and sterilize them in a water bath;

[0011] S4. After cooling, adding lactic acid bacteria for fermentation, and then performing post-ripening treatment to obtain Pleurotus geesteranus protein yogurt.

[0012] Preferably, while maintaining the solid content of the yogurt at 10-12%, the mass ratio of skimmed milk powder to Pleurotus geesteranus protein is controlled to be 0:100 to 99:1.

[0013] Preferably, while maintaining the protein content of the yogurt at 10-12%, the mass ratio of skimmed milk powder to Pleurotus geesteranus protein is controlled to be 0:100 to 99:1.

[0014] Preferably, the lactic acid bacteria include at least one of Lactobacillus bulgaricus, Streptococcus thermophilus, and Bifidobacterium, and the inoculation amount of the lactic acid bacteria is 1%-5%.

[0015] Preferably, the fermentation is carried out at 40-50° C. until the pH value of the mixed solution reaches 4-5.

[0016] Preferably, the water bath sterilization treatment is performed in a water bath at 80-120° C. for 10-30 minutes.

[0017] Preferably, the post-ripening treatment is refrigeration in a 4°C refrigerator for 10-12 hours.

[0018] Preferably, the cooling is cooling to 40-45° C., and then adding lactic acid bacteria for fermentation.

[0019] Preferably, the Pleurotus geesteranus protein is a protein prepared from Pleurotus geesteranus fruiting bodies by a mild wet extraction process, and the specific preparation method comprises the following steps:

[0020] S11, drying and crushing: drying the fresh Pleurotus geesteranus until crisp, and grinding into powder;

[0021] S12, defatting: mixing the Pleurotus geesteranus powder with n-hexane, stirring at room temperature, filtering and ventilating to evaporate the n-hexane, to obtain defatted powder;

[0022] S13. Protein extraction: Disperse the defatted powder in water, adjust the pH to 7.5-8.5, stir at room temperature, collect the clarified protein solution by centrifugation, and then dialyze and dry to obtain Pleurotus geesteranus protein.

[0023] More preferably, in S12, the Pleurotus geesteranus powder and n-hexane are mixed at a material-liquid ratio of 1 g:4 mL; the stirring speed is 300-600 r / min at room temperature for 1-4 h.

[0024] More preferably, in S13, the concentration of the defatted powder in water is 7-13 g / 100 mL; the stirring speed at room temperature is 300-600 r / min for 1-4 h; the centrifugation is (8000-15000 r / min for 20-60 min; and the dialysis is performed at a molecular weight cutoff of 2.5-3.5 kDa at 4° C. for 40-60 h.

[0025] More preferably, in S11, the powder is ground into powder and then passed through a 60-90 mesh sieve.

[0026] The second aspect of the present invention provides Pleurotus geesteranus protein yogurt prepared by the preparation method described in the first aspect.

[0027] The third aspect of the present invention provides application of the preparation method described in the first aspect in dairy product processing.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention discloses a Pleurotus geesteranus protein yogurt and a preparation method thereof. First, skim milk powder and white sugar are dissolved in water, and Pleurotus geesteranus protein is also dissolved in water. The two solutions are then mixed evenly, and the mass ratio of skim milk powder to Pleurotus geesteranus protein is controlled to be 0:100 to 99:1. Lactobacillus bulgaricus is then added for fermentation to obtain Pleurotus geesteranus protein yogurt. Specifically, the present invention has the following advantages:

[0030] (1) The Pleurotus geesteranus protein used in the present invention has a simple processing technology and is rich in essential amino acids, dietary fiber, vitamins, etc. The ratio of essential amino acids contained in it meets the needs of children and adults, and can well supplement appropriate nutrients for the human body.

[0031] (2) The present invention uses Pleurotus geesteranus protein to replace animal protein, which not only reduces the burden of animal protein on the environment, but also improves the nutritional value of the protein, is beneficial to human absorption, and meets people's needs for nutrition, environmental protection, and safety.

[0032] (3) The present invention utilizes the property of acid-induced weakening of the gel strength of Pleurotus geesteranus protein to prepare a yogurt with high protein, high dietary fiber, low viscosity and low hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the appearance of ordinary protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1.

[0034] Figure 2This is a microscopic structure diagram of ordinary protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1.

[0035] Figure 3 This is a graph showing the pH changes during fermentation of ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 1.

[0036] Figure 4 This is a graph showing the acidity values ​​of ordinary protein yogurts prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 1.

[0037] Figure 5 This is a water retention diagram of ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1.

[0038] Figure 6 This is a graph showing the number of viable bacteria in ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skim milk powder in Example 1.

[0039] Figure 7 This is a graph showing the rheological properties of ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 1.

[0040] Figure 8 This is the appearance of high-protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2.

[0041] Figure 9 This is a microscopic structure diagram of high-protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2.

[0042] Figure 10 This is a graph showing the pH changes during fermentation of high-protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2.

[0043] Figure 11 This is a graph showing the acidity values ​​of high-protein yogurts made with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2.

[0044] Figure 12 This is a water retention diagram of high-protein yogurt made with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2.

[0045] Figure 13 This is a graph showing the number of viable bacteria in high-protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2.

[0046] Figure 14 This is a graph showing the rheological properties of high-protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2.

[0047] Figure 15 This is the appearance of ordinary protein yogurt made with different ratios of soy protein and skim milk powder in the comparative example.

[0048] Figure 16 This is the appearance of ordinary protein yogurt made with different ratios of pea protein and skim milk powder in the comparative example.

[0049] Figure 17 This is the rheological properties diagram of high-protein yogurt made with different ratios of soy protein to skim milk powder in the comparative example.

[0050] Figure 18 This is the rheological properties diagram of high-protein yogurt made with different ratios of pea protein to skim milk powder in the comparative example. DETAILED DESCRIPTION

[0051] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0052] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0053] Example 1: A method for preparing oyster mushroom protein yogurt

[0054] (1) Fresh Pleurotus geesteranus was purchased from the local market at South China Agricultural University. The fruiting bodies of Pleurotus geesteranus were dried in a food oven at 60°C for 6 h (food dehydrator FGJ-16, Demasch, Germany) until brittle, then ground into powder in a pulverizer (high-speed grinder ML-800Y, MOLING, China) and sieved through a 70-mesh sieve. The powder was mixed with n-hexane (Tianjin Fuyu Chemical, China) at a solid-liquid ratio of 1:4 (g:mL), stirred at room temperature (400 rpm) for 2 h, filtered, and left in a fume hood overnight to evaporate the n-hexane. The defatted powder (100 g) was dispersed in deionized water (1000 mL). The pH of the dispersion was adjusted to 8.0 with 2 M NaOH solution and stirred at room temperature (400 rpm) for 2 h. The mixture was then centrifuged at 10,000 rpm for 30 min at room temperature (Eppendorf 5804R, Germany), and the collected clarified protein solution was dialyzed for 48 h (4°C refrigerator, molecular weight cutoff of 3 kDa). Finally, the Pleurotus geesteranus protein was obtained by freeze-drying (Lyophilizer FD-10-50, Biocool, China).

[0055] (2) While keeping the solid content at 11%, different amounts of Pleurotus geesteranus protein (1%, 25%, 50%, 75%, 100%) were used to replace skimmed milk powder to prepare Pleurotus geesteranus protein yogurt. The final ratios of Pleurotus geesteranus protein to skimmed milk powder were 1:99, 25:75, 50:50, 75:25, and 100:0 (for example, to prepare 100g of yogurt, the amounts of Pleurotus geesteranus protein and skimmed milk powder were 0.11g:10.89g, 2.75g:8.25g, 5.5g:5.5g, 8.25g:2.75g, and 11g:0g, respectively).

[0056] (3) Weigh a certain amount of skim milk powder and 6% (w / w; based on the total mass of yogurt) white sugar and disperse them in distilled water until fully dissolved.

[0057] (4) Fully dissolve the Pleurotus geesteranus protein in distilled water, then mix the protein solution with the dispersion obtained in step (3) and place in a 100° C. water bath for 30 min.

[0058] (5) When the mixed solution was cooled to 40-45°C, 3% (w / w; based on the total mass of the yogurt) of Lactobacillus bulgaricus powder (Xi'an Mixianer Biotechnology Co., Ltd., batch number: MXR20240521) was inoculated and cultured at 42°C until the pH of the sample reached 4.5 / 4.6. The sample was then taken out and placed in a 4°C refrigerator for post-ripening for 12 hours to obtain Pleurotus geesteranus regular protein yogurt (PRPY).

[0059] The prepared Pleurotus geesteranus ordinary protein yogurt was subjected to characterization tests. The total solids, ash, and fat contents of conventional yogurt were determined according to the method described in GB 5009-2016. The protein content of the yogurt was determined using a Kjeldahl nitrogen analyzer (KjeltecTM 8100, Denmark). The lactose content of the yogurt was determined according to the acid hydrolysis-Rhein-Eynon method described in GB 5009.8-2023. The microstructure of the yogurt was observed using a laser confocal microscope at an excitation wavelength of 633 nm. The pH change during the yogurt fermentation process was measured using a pH meter. The titratable acidity of the yogurt was determined using the phenolphthalein indicator method. A certain amount of yogurt was placed in a centrifuge tube and centrifuged at 5000 g for 10 min to determine the water holding capacity of the yogurt. The viable cell count of the yogurt was measured according to the lactobacillus count method described in GB 4789.35-2023. The apparent viscosity of the yogurt was determined using an Anton Paar MCR502 modular intelligent advanced rheometer, and frequency and stress sweeps were performed with a gap of 1.0 mm, a temperature of 25°C, a strain of 0.1%, and a frequency of 0.1 Hz.

[0060] Figure 1This is the appearance of ordinary protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1. Figure 1 It can be seen that when the ratio of Pleurotus geesteranus protein to skimmed milk powder is 0:100, the yogurt forms an inverted and non-flowing state, and as the amount of Pleurotus geesteranus protein replacement increases, the color of the yogurt gradually becomes darker and duller, and there is an unpleasant taste. The texture becomes smooth and delicate, showing a liquid with strong fluidity.

[0061] In this example, the protein in yogurt was stained with Nile blue and then observed using a laser confocal microscope to obtain the microstructure of the yogurt. Figure 2 The microstructure of ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1 is shown. Figure 2 It can be seen that with the increase of the amount of Pleurotus geesteranus protein replacement, the protein aggregates in yogurt were significantly reduced, the distribution became more uneven, and a looser gel network structure was formed.

[0062] Table 1 shows the chemical composition of standard protein yogurts prepared at varying ratios of Pleurotus geesteranus protein to skim milk powder. As shown in Table 1, the protein content of the yogurt increases as the amount of Pleurotus geesteranus protein added increases, reaching a maximum of 6.79% when the Pleurotus geesteranus protein completely replaces the skim milk powder. This is likely due to the increased protein content of the yogurt. The ash, fat, total carbohydrate, and lactose contents of the yogurt all show a decreasing trend with increasing Pleurotus geesteranus protein addition, which may be related to the low protein purity and high lactose content of skim milk powder.

[0063] Figure 3 The graph shows the change of pH value over time during fermentation of ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 1. Figure 3 The pH of yogurt prepared with pure skim milk powder began to decline after 3 hours of fermentation, while after adding Pleurotus geesteranus protein, the pH of the yogurt only began to slowly decline after 6 hours. As the amount of Pleurotus geesteranus protein replacement increased, the rate of pH decline gradually slowed, resulting in a weakening of the yogurt's acid production capacity and a longer fermentation time.

[0064] Figure 4 The figure shows the acidity value of ordinary protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1. Figure 4 It can be seen that as the amount of Pleurotus geesteranus protein replacement increases, the acidity of ordinary protein yogurt decreases significantly. This may be because the addition of Pleurotus geesteranus protein weakens the pH buffering capacity of the yogurt system, leading to a decrease in acidity.

[0065] Figure 5The water-holding capacity of conventional protein yogurt prepared at different ratios of Pleurotus geesteranus protein to skim milk powder in Example 1 is shown. The water-holding capacity of yogurt without Pleurotus geesteranus protein is 78.56%. As the amount of Pleurotus geesteranus protein replacement increases, the water-holding capacity of the yogurt decreases first and then increases, reaching a minimum of 33.00% at a 25% Pleurotus geesteranus protein replacement.

[0066] Figure 6 This graph shows the viable bacterial counts of conventional protein yogurts prepared with different ratios of Pleurotus geesteranus protein to skim milk powder in Example 1. As the amount of Pleurotus geesteranus protein replacement increased, the total number of viable Lactobacillus bulgaricus in the yogurt decreased from 9.58 lg CFU / mL to 7.60 lg CFU / mL. All yogurts met the lactic acid bacteria count requirements of GB 19302-2010.

[0067] Figure 7 The rheological properties of ordinary protein yogurt prepared with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 1 are shown in FIG. Figure 7 As shown in A, when the shear rate is low, all yogurt samples have a high apparent viscosity. As the shear rate increases, the apparent viscosity of the yogurt samples decreases rapidly. All samples are pseudoplastic fluids and exhibit shear thinning. At the same shear rate, as the amount of Pleurotus geesteranus protein replacement increases, the apparent viscosity of ordinary protein yogurt shows a trend of first decreasing and then increasing. Figure 7 B shows that within the frequency range of 0.01 to 100 rad / s, the storage modulus (G') and loss modulus (G") of all yogurt samples increase with increasing frequency, and the G' value is always higher than the G" value, indicating that elasticity is dominant in all samples, showing solid-like characteristics. In addition, with the increase of the amount of Pleurotus geesteranus protein substitution, the G' value of ordinary protein yogurt shows a trend of first decreasing and then increasing. When the amount of Pleurotus geesteranus protein substitution is 0, the yogurt shows the highest G' value. Figure 7 C shows that within the linear viscoelastic region, G′ and G″ of yogurt are independent of stress and do not change with stress. As the stress continues to increase, the G′ of yogurt decreases. Under the same stress, the G′ value of ordinary protein yogurt decreases with the increase of the amount of Pleurotus geesteranus protein replacement.

[0068] From the appearance, microstructure, physicochemical properties and rheological characteristics analysis of the ordinary Pleurotus geesteranus protein yogurt in Example 1, it can be seen that the use of Pleurotus geesteranus protein to partially or completely replace skimmed milk powder in the present invention can improve the bioavailability of Pleurotus geesteranus protein and the protein content of yogurt, making the yogurt easier to be absorbed by the human body. Therefore, Pleurotus geesteranus protein has the potential to replace animal protein and has great application prospects in dairy product processing.

[0069] Table 1 Effect of the ratio of Pleurotus geesteranus protein to skimmed milk powder on the chemical composition of Pleurotus geesteranus protein yogurt (g / 100g)

[0070]

[0071] Example 2: A method for preparing oyster mushroom protein yogurt

[0072] (1) While keeping the protein content at 11%, different amounts of Pleurotus geesteranus protein (1%, 25%, 50%, 75%, 100%) were used to replace skimmed milk powder to prepare Pleurotus geesteranus high-protein yogurt. The final ratios of Pleurotus geesteranus protein to skimmed milk powder were 1:99, 25:75, 50:50, 75:25, and 100:0, respectively. Among them, the Pleurotus geesteranus protein content was 76%, and the skimmed milk powder protein content was 25% (for example, to prepare 100g of yogurt, the amounts of Pleurotus geesteranus protein and skimmed milk powder were 0.43g:42.69g, 7.29g:21.86g, 10.89g:10.89g, 13.04g:4.35g, and 14.47g:0g, respectively).

[0073] (2) Weigh a certain amount of skim milk powder and 6% (w / w; based on the total mass of yogurt) white sugar and disperse them in distilled water until fully dissolved.

[0074] (3) Fully dissolve the Pleurotus geesteranus protein in distilled water, then mix the protein solution with the dispersion obtained in step (2) and place in a 100° C. water bath for 30 min.

[0075] (4) When the mixed solution is cooled to 40-45°C, 3% (w / w; based on the total mass of the yogurt) of Lactobacillus bulgaricus powder is inoculated and cultured at 42°C until the pH of the sample reaches 4.5 / 4.6. The sample is then taken out and placed in a 4°C refrigerator for post-ripening treatment to obtain Pleurotus geesteranus high protein yogurt (PHPY).

[0076] The prepared Pleurotus geesteranus high-protein yogurt was characterized. The total solids, ash, and fat contents of the yogurt were determined according to the method described in GB 5009-2016. The protein content was determined using a Kjeldahl nitrogen analyzer. The lactose content was determined according to the acid hydrolysis-Rhine-Eynon method described in GB 5009.8-2023. The microstructure of the yogurt was observed using a laser confocal microscope at an excitation wavelength of 633 nm. The pH change during the fermentation process was measured using a pH meter. The titratable acidity of the yogurt was determined using the phenolphthalein indicator method. A certain amount of yogurt was placed in a centrifuge tube and centrifuged at 5000 g for 10 minutes to determine the water holding capacity of the yogurt. The viable bacterial count of the yogurt was measured according to the lactobacillus count method described in GB 4789.35-2023. The apparent viscosity of the yogurt was measured using an Anton Paar MCR502 modular intelligent advanced rheometer, and frequency and stress sweeps were performed.

[0077] Figure 8 This is the appearance of high-protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2. Figure 8 It can be seen that when the amount of Pleurotus geesteranus protein replacement is 0, the high-protein yogurt is difficult to spread, and the texture is thick and hard, very firm, and has a noticeable graininess. As the amount of Pleurotus geesteranus protein replacement increases, the characteristic thick and thick texture of high-protein yogurt is improved, and the noticeable graininess is eliminated. It is more delicate and smooth, showing a more watery and fluid state.

[0078] Figure 9 The microstructure of high-protein yogurt prepared with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2. Figure 9 It can be seen that when the amount of Pleurotus geesteranus protein replacement was zero, yogurt fermented with pure skim milk powder exhibited a uniform and dense gel network structure with protein particles of similar size and uniform distribution. As the amount of Pleurotus geesteranus protein replacement increased, the gaps in the gel network structure of the yogurt samples increased, the distribution became more uneven, and the number of large protein particles gradually increased.

[0079] Table 2 shows the chemical composition of high-protein yogurt made with different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2. As can be seen from Table 2, as the amount of Pleurotus geesteranus protein replaced increases, the total solid content of the high-protein yogurt shows a trend of gradually decreasing. The protein content of all high-protein yogurt samples remained at around 11%, which is in line with the protein content of high-protein yogurt (>7%). The ash, fat, total carbohydrate, and lactose contents of the high-protein yogurt gradually decreased with the increase in the amount of Pleurotus geesteranus protein replaced, all meeting the requirements of the national standard.

[0080] Figure 10 The pH value changes of high-protein yogurt prepared with different ratios of Pleurotus geesteranus protein to skimmed milk powder during the fermentation process in Example 2 are shown in FIG. Figure 10The results show that when the ratio of Pleurotus geesteranus protein to skim milk powder was 1:99, 25:75, 50:50, 75:25, and 100:0, the fermentation time required for yogurt was 12 hours, 15 hours, 15 hours, 16 hours, and 20 hours, respectively. Compared with yogurt with skim milk powder, the fermentation time of all yogurts with Pleurotus geesteranus protein increased significantly, and the fermentation rate decreased.

[0081] Figure 11 The figure shows the acidity value of high-protein yogurt made from different ratios of Pleurotus geesteranus protein to skimmed milk powder in Example 2. Figure 11 It can be seen that with the increase of the amount of Pleurotus geesteranus protein replacement, the acidity value of high-protein yogurt continues to decrease, which may be related to the low lactose content, which inhibits the reproduction and growth of lactic acid bacteria.

[0082] Figure 12 The water holding capacity diagram of high protein yogurt prepared with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2. Figure 12 As the amount of Pleurotus geesteranus protein replacement increased, the water-holding capacity of high-protein yogurt decreased from 92.68% to 62.23%. This may be because the addition of Pleurotus geesteranus protein reduced protein aggregation, resulting in a looser protein network structure, which ultimately reduced the yogurt gel's ability to capture and retain water.

[0083] Figure 13 The figure shows the number of viable bacteria in high-protein yogurt made with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2. Figure 13 It can be seen that the survival count of Lactobacillus bulgaricus in high-protein yogurt without Pleurotus geesteranus protein is 10.40lgCFU / mL. When the amount of Pleurotus geesteranus protein is increased, the number of viable bacteria in high-protein yogurt decreases continuously until the yogurt reaches the lowest viable count of 7.59lgCFU / mL when the amount of Pleurotus geesteranus protein is 100%. 6 CFU / mL and above, which meets the standard requirements of GB 19302-2010 for the count of live lactic acid bacteria in yogurt.

[0084] Figure 14 The rheological properties of high-protein yogurt prepared with different ratios of Pleurotus geesteranus protein and skimmed milk powder in Example 2 are shown in FIG. Figure 14 As shown in Figure 1, the apparent viscosity of all yogurt samples gradually decreased with increasing shear rate, indicating that the samples exhibited typical shear-thinning properties of non-Newtonian fluids. Furthermore, the apparent viscosity of high-protein yogurt was negatively correlated with the amount of Pleurotus geesteranus protein replacement. As the amount of Pleurotus geesteranus protein replacement increased, the G′ and G″ of high-protein yogurt continued to decrease, indicating that a higher addition of Pleurotus geesteranus protein was not conducive to the formation of a dense gel network structure, thereby improving the fluidity of the yogurt and reducing its apparent viscosity. Figure 14B shows that the high-protein yogurt fermented with pure skim milk powder has the highest G' value. The G' value of high-protein yogurt decreases with the increase of the amount of Pleurotus geesteranus protein replacement, and the gel strength of the yogurt also decreases, thereby improving the fluidity of the yogurt. Figure 14 C shows that the G' value of high-protein yogurt maintains a constant value within the linear viscoelastic region. When it exceeds the region, the G' value decreases as the stress increases, and the gel structure of the yogurt is destroyed. Under a certain stress, when the amount of Pleurotus geesteranus protein replacement increases, the G' value of high-protein yogurt gradually decreases, indicating that the addition of Pleurotus geesteranus protein can improve the heavy and dry texture of high-protein yogurt, reduce its gel strength, and thus enhance the fluidity of yogurt. From the appearance diagram, microstructure, physicochemical properties and rheological properties analysis of Pleurotus geesteranus high-protein yogurt in Example 2, it can be seen that using Pleurotus geesteranus protein as a substitute for skimmed milk powder, a yogurt with high protein, high dietary fiber, low hardness and low viscosity can be prepared, which has great application prospects in the field of high-protein foods such as dairy products.

[0085] Table 2 Effect of the ratio of Pleurotus geesteranus protein to skimmed milk powder on the chemical composition of Pleurotus geesteranus high-protein yogurt (g / 100g)

[0086]

[0087] Comparative Example: Preparation Method of Plant High-Protein Yogurt

[0088] (1) While keeping the protein content at 11%, different amounts of soy protein (purchased from Xi'an Youlanda Biotechnology Co., Ltd., prepared by alkali dissolution and acid precipitation method, batch number: YT1-25040803) and pea protein (purchased from Xi'an Youlanda Biotechnology Co., Ltd., prepared by alkali dissolution and acid precipitation method, batch number: YT1-25040501) (1%, 25%, 50%, 75%, 100%) were used to replace skimmed milk powder to prepare ordinary protein yogurt of Pleurotus geesteranus. The final ratios of protein to skimmed milk powder were 1:99, 25:75, 50:50, 75:25, and 100:0, respectively.

[0089] (2) Weigh a certain amount of skim milk powder and 6% (w / w; based on the total mass of yogurt) white sugar and disperse them in distilled water until fully dissolved.

[0090] (3) The protein was fully dissolved in distilled water, and then the protein solution was mixed evenly with the dispersion obtained in step (2), and placed in a 100°C water bath for 30 minutes.

[0091] (4) When the mixed solution is cooled to 40-45°C, 3% (w / w; based on the total mass of the yogurt) of Lactobacillus bulgaricus powder is inoculated and cultured at 42°C until the pH of the sample reaches 4.5 / 4.6. The sample is then taken out and placed in a 4°C refrigerator for post-ripening treatment to obtain plant high-protein yogurt.

[0092] The plant-based high-protein yogurt prepared above was subjected to characterization tests. The apparent viscosity of the yogurt was measured using an Anton Paar MCR502 modular intelligent advanced rheometer, and a frequency sweep was performed.

[0093] Figure 15 and Figure 16 This is the appearance of high-protein yogurt made from different plant proteins and skimmed milk powder in the comparative example. Figure 15 It can be seen that as the amount of soy protein replacement increases, the color of the yogurt gradually becomes darker and duller, the texture is relatively rough, and there is a clear sense of graininess, all showing a solid with strong gel properties. Figure 16 As can be seen, when the pea protein replacement level is 1, the high-protein yogurt is difficult to spread, with a thick, hard texture, very firm, and a noticeable graininess. As the pea protein replacement level increases, the characteristic thick and thick texture of high-protein yogurt improves, and the noticeable graininess disappears, becoming more delicate and smooth, with a more watery and fluid appearance. However, as the pea protein replacement level continues to increase, the yogurt exhibits a gel-like solid state, with a rough and grainy texture.

[0094] Figure 17 and Figure 18 The following is a graph showing the rheological properties of high-protein yogurt made with different ratios of vegetable protein to skimmed milk powder in the comparative example. Figure 17 It can be seen that when the amount of soy protein replacement is increased, the G' and G" of high-protein yogurt continue to increase, and G" is always greater than G', indicating that a higher amount of soy protein added promotes the formation of a dense gel network structure, forming a stronger three-dimensional network structure, and making the sample exhibit elastic properties. Figure 18 As shown, with increasing amounts of pea protein replacement, the G' value of pea high-protein yogurt shows a trend of first decreasing and then increasing. Pea high-protein yogurt with a pea protein to skim milk powder ratio of 100:0 exhibits the highest gel strength. The appearance and rheological properties of the plant-based high-protein yogurts in the comparative examples show that yogurt prepared using plant protein obtained by alkali dissolution and acid precipitation as a skim milk powder replacement exhibits high hardness and viscosity, and exhibits excellent gel properties. Substituting high-protein oyster mushrooms for skim milk powder can produce a yogurt that is high in protein, high in dietary fiber, low in hardness, and low in viscosity. This not only addresses the inherent hardness and viscosity issues of this type of high-protein yogurt, but also better meets people's nutritional and safety needs.

[0095] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for preparing Pleurotus geesteranus protein yogurt, characterized in that: The following steps are involved: S1. Dissolve skimmed milk powder and white sugar in water; S2, dissolving Pleurotus geesteranus protein in water; S3, mix the two solutions of S1 and S2 and sterilize them in a water bath; S4. After cooling, adding lactic acid bacteria for fermentation, and then performing post-ripening treatment to obtain Pleurotus geesteranus protein yogurt.

2. The method for preparing a Pleurotus geesteranus protein yogurt according to claim 1, wherein: While maintaining the solid content of the yogurt at 10-12%, the mass ratio of skimmed milk powder to Pleurotus geesteranus protein is controlled to be 0:100-99:

1.

3. The method for preparing a Pleurotus geesteranus protein yogurt according to claim 1, wherein: Under the condition of maintaining the protein content of yogurt at 10-12%, the mass ratio of skimmed milk powder to Pleurotus geesteranus protein is controlled to be 0:100-99:

1.

4. The method for preparing a Pleurotus geesteranus protein yogurt according to claim 1, wherein: The lactic acid bacteria include at least one of Lactobacillus bulgaricus, Streptococcus thermophilus and Bifidobacterium, and the inoculation amount of the lactic acid bacteria is 1%-5%.

5. The method for preparing a Pleurotus geesteranus protein yogurt according to claim 1, wherein: The fermentation is carried out at 40-50° C. until the pH value of the mixed liquid is 4-5.

6. The method for preparing a Pleurotus geesteranus protein yogurt according to claim 1, wherein: The water bath sterilization treatment is carried out in a water bath at 80-120° C. for 10-30 minutes.

7. The method for preparing Pleurotus geesteranus protein yogurt according to claim 1, wherein: The preparation method of the Pleurotus geesteranus protein comprises the following steps: S11, drying and crushing: drying the fresh Pleurotus geesteranus until crisp, and grinding into powder; S12, defatting: mixing the Pleurotus geesteranus powder with n-hexane, stirring at room temperature, filtering and ventilating to evaporate the n-hexane, to obtain defatted powder; S13. Protein extraction: Disperse the defatted powder in water, adjust the pH to 7.5-8.5, stir at room temperature, collect the clarified protein solution by centrifugation, and then dialyze and dry to obtain Pleurotus geesteranus protein.

8. The method for preparing Pleurotus geesteranus protein yogurt according to claim 7, wherein: In S12, the Pleurotus geesteranus powder and n-hexane are mixed at a material-liquid ratio of 1 g:4 mL; the stirring speed is 300-600 r / min at room temperature for 1-4 h.

9. The method for preparing Pleurotus geesteranus protein yogurt according to claim 7, wherein: In S13, the concentration of the defatted powder in water is 7-13 g / 100 mL; the stirring speed at room temperature is 300-600 r / min for 1-4 h; the centrifugation is (8000-15000 r / min for 20-60 min; and the dialysis is performed at a molecular weight cutoff of 2.5-3.5 kDa at 4° C. for 40-60 h.

10. Pleurotus geesteranus protein yogurt prepared by the preparation method according to any one of claims 1 to 9.

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