Method for treating long-term bread by utilizing pediococcus pentosaceus JS35 as well as product and application of pediococcus pentosaceus JS35

Abstract

The invention discloses a method for treating long-term bread by utilizing pediococcus pentosaceus JS35 as well as a product and application of the pediococcus pentosaceus JS35. Mixing the pediococcus pentosaceus JS35 fermentation liquor and the saccharomycetes fermentation liquor to obtain mixed liquor; heating and acidifying the long-term bread, preserving heat and moisture, cooling, adding the mixed bacterial liquid, and standing to obtain aged yeast; fermented flour products such as bread and steamed buns are produced through fermentation. The pediococcus pentosaceus JS35 adopted in the method has the advantages of being high in safety, good in acid resistance and high in exopolysaccharide yield, in addition, in-time bread added with sugar, oil and salt can be used as a fermentation substrate for making aged yeast, and finally the bread which is good in flavor, safe and reliable can be produced; the citric acid adopted in the invention is a common raw material in the food industry, and the pediococcus pentosaceus and the saccharomyces cerevisiae adopted in the invention are both food fermentation strains, so that the safety is high, and the method is environment-friendly; the method is mild in production condition, simple in operation process and easy for industrial expanded production.

Description

Technical Field

[0001] The invention relates to a method for treating near-expiry bread by utilizing Pediococcus pentosaceus JS35, a product thereof and an application thereof, and belongs to the fields of microbial application and food processing. Background Art

[0002] Nearly expiring food refers to food that is about to reach its shelf life but is still within its shelf life. This part of food still belongs to the category of safe food. At present, my country's bread market has exceeded 100 billion yuan. For bakeries and supermarkets, a large number of near-expiring bread are produced every day, some of which will be sold at a discount, and some will be discarded because they have exceeded their shelf life. According to the China Baking Association's online disclosure, in 2023, the scrap volume of bakeries will reach 500,000 tons.

[0003] Lactic acid bacteria fermentation is a method to improve the quality of bread and is also a traditional bread fermentation method. The traditional "old yeast" (or "starter") is a dough formed by fermenting the lactic acid bacteria and yeast in wheat flour. Today's food biotechnology has developed to the point where lactic acid bacteria with different characteristics and functions are screened, and then inoculated into the dough after pure cultivation to make "old yeast" that can ferment bread, steamed buns or other rice and flour products. This kind of "old yeast" with pure strains is not easily contaminated by miscellaneous bacteria because of its high strain purity, and because of the different lactic acid bacteria inoculated, the bread made with "old yeast" has a soft taste, or has the function of delaying aging, or has the function of extending the shelf life. The "old yeast" made by pure strain fermentation is based on wheat flour as the main matrix, or other grain raw materials such as rice and rye are added.

[0004] Since the presence of sugar, salt, butter, additives, and possible bacteria in expiring bread will affect the growth of pure lactic acid bacteria, there has been no report on the use of expiring bread as a matrix for "old yeast". The current technical bottleneck lies in finding a suitable lactic acid bacteria strain that can grow by fermenting expiring bread. In turn, expiring bread can be converted into "old yeast" to produce bread or other fermented grain products with good flavor, safety and reliability. Summary of the invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for treating near-expiry bread using Pediococcus pentosaceus JS35, and its products and applications. The treatment method is easy to operate, highly safe and has good application effect.

[0006] Technical solution: To solve the above technical problems, the present invention provides a method for treating expiring bread using Pediococcus pentosaceus JS35, comprising the following steps:

[0007] (1) mixing a fermentation liquid of Pediococcus pentosaceus JS35 and a fermentation liquid of yeast (Saccharomyces cerevisiae) to obtain a mixed liquid;

[0008] (2) Heat the expiring bread to acidify it, keep it warm and moisturize it, and after cooling, add the mixed bacterial solution described in step (1) to ensure that the number of Pediococcus pentosaceus reaches 10 6 cfu / g bread or more, let it stand to obtain old yeast.

[0009] Wherein, the concentration of Pediococcus pentosaceus JS35 in the Pediococcus pentosaceus JS35 fermentation broth in step (1) is 10 8 cfu / mL or more; the concentration of yeast in the yeast (Saccharomyces cerevisiae) fermentation broth is 10 6 cfu / mL or above.

[0010] The preparation method of the fermentation liquid of Pediococcus pentosaceus JS35 is as follows: Pediococcus pentosaceus JS35 is first inoculated in MRS solid culture medium for activation, then inoculated in MRS liquid culture medium to obtain a primary seed liquid, and then inoculated in any liquid culture medium suitable for lactic acid bacteria culture for fermentation, the fermentation temperature is 28-40°C, the fermentation time is 12-30h, and then the liquid culture medium containing the bacteria is centrifuged at low temperature and the supernatant is discarded to obtain enriched bacteria, and then the bacteria are rinsed with sterile water and resuspended to adjust the bacterial concentration to 10 8 cfu / mL, the resuspension containing bacteria is the lactic acid bacteria fermentation solution for subsequent work;

[0011] The preparation method of yeast (Saccharomyces cerevisiae) fermentation liquid is as follows: brewer's yeast is inoculated into YPD solid medium for culture and activation, then inoculated into YPD liquid medium to obtain a primary seed liquid, and then inoculated into any liquid medium suitable for yeast culture for fermentation, the fermentation temperature is 25-30°C, the fermentation time is 24-48h, and then the liquid medium containing the bacteria is centrifuged at low temperature and the supernatant is discarded to obtain enriched bacteria, and then the bacteria are rinsed with sterile water and resuspended to adjust the bacterial concentration to 10 6 cfu / mL, and the resuspension containing the bacteria is the yeast fermentation broth for subsequent work.

[0012] The acidification method of the expiring bread in step (2) is as follows: adjusting the expiring bread to be acidic by using an acidity adjuster, so that the expiring bread becomes a soft, loose and moist dough;

[0013] The acidity adjuster includes citric acid, vinegar or malic acid, preferably citric acid.

[0014] Among them, the mass ratio of bread to acidity adjustment is 100:35~45.

[0015] Wherein, the pH value of the acidity adjuster is 4.5-5.0.

[0016] Wherein, the temperature of heat preservation and moisture retention in step (2) is 65° C., and the time is 30 to 40 minutes.

[0017] Wherein, the mass ratio of the near-expiry bread to the mixed bacterial liquid in step (2) is 100:15-25.

[0018] The static temperature is 26 to 32°C and the static time is 16 to 30 hours.

[0019] The invention also provides an old yeast product prepared by the treatment method.

[0020] The present invention also provides application of the product of the processing method in preparing fermented cereal products.

[0021] Wherein, the fermented cereal products include bread, steamed buns or noodles.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] 1. The Pediococcus pentosaceus JS35 (a member of the lactic acid bacteria family) used in the present invention has the characteristics of high safety, good acid resistance, and production of extracellular polysaccharides. In addition, the expiring bread to which sugar, oil, and salt have been added can be used as a fermentation matrix to make "old yeast", and finally a fermented cereal product with good flavor, safety, and reliability can be produced;

[0024] 2. The present invention processes near-expiry bread into "old yeast" and applies it to fermented rice, flour and grain foods. Its content complies with the "Anti-Food Waste Law of the People's Republic of China" and the "Food Safety Law of the People's Republic of China". It relies on science and technology to implement the "big food concept" policy in the country's No. 1 document and promote green and sustainable economic development;

[0025] 3. The citric acid used in the present invention is a common raw material in the food industry, and the Pediococcus pentosaceus and Saccharomyces cerevisiae used are both food fermentation strains, which are highly safe and environmentally friendly;

[0026] 4. The production conditions of the present invention are mild, the operation process is simple, and it is easy to expand the production industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The slices (A) and texture images (B) of the breads of each group are as follows: from left to right: control group, positive control group 1, positive control group 2, example 1, example 2, example 3, example 4;

[0028] Figure 2 Steamed buns made with different recipes: from left to right are steamed buns made with recipes ①, ②, ③, ④, ⑤, and ⑥. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0030] Example 1

[0031] 1) Preparation of fermented bacterial liquid of lactic acid bacteria: Pediococcus pentosaceus JS35 (Chinese patent publication number of the bacteria: CN117757658A) was first inoculated into MRS solid medium for culture activation, then inoculated into MRS liquid medium to obtain primary seed liquid, and then inoculated into MRS liquid medium for fermentation at a temperature of 37° C. for 24 h, and then the liquid medium containing the bacterial cells was centrifuged at 4° C. and the supernatant was discarded to obtain enriched bacterial cells, and then the bacterial cells were rinsed and resuspended with sterile water and the bacterial cell concentration was adjusted to 10 8 cfu / mL, and the resuspension containing the bacteria is the lactic acid bacteria fermentation solution in the subsequent work;

[0032] 2) Preparation of yeast fermentation broth: Saccharomyces cerevisiae (Saccharomyces cerevisiae, deposit number CGMCC 2842, the paper disclosing the strain: Isolation and screening of haploid strains of Saccharomyces cerevisiae and preliminary study on its production of adenosylmethionine, published in Industrial Microbiology in 2015, DOI: 10.3969 / j.issn.1001-6678.2015.03.006) was inoculated into YPD solid medium for activation, then inoculated into YPD liquid medium to obtain primary seed solution, then inoculated into YPD liquid medium for fermentation, the fermentation temperature was 28°C, the fermentation time was 32h, then the liquid medium containing the cells was centrifuged at 4°C and the supernatant was discarded to obtain enriched cells, then the cells were rinsed with sterile water and resuspended to adjust the cell concentration to 10 6 cfu / mL, the resuspension containing the bacteria is the yeast fermentation broth in the subsequent work;

[0033] 3) mixing the lactic acid bacteria fermentation liquid and the yeast fermentation liquid in equal volume ratios and setting aside;

[0034] 4) Put the expiring toast bread (shelf life 4 days, 0.5 day near expiration) into a dough mixer, and then add a citric acid solution with a pH value of 5.0 at a ratio of 40g citric acid per 100g bread to knead the dough, so that the expiring bread becomes a soft, loose and moist dough;

[0035] 5) Heat the dough to 65°C and keep it warm and moist for 35 minutes;

[0036] 6) Cool the heated dough to 30°C, then spray the mixed fermentation liquid from step 3) while kneading the dough. The addition ratio is 20g of liquid per 100g of bread, and ensure that the number of Pediococcus pentosaceus reaches 10 7 cfu / g bread or more;

[0037] 7) The dough sprayed with the mixed bacterial solution is placed in an environment of 28°C and cultured for 24 hours to prepare an "old yeast" containing live bacteria.

[0038] 8) Bread was produced according to the formula of 100 g wheat flour, 15 g of the above-mentioned "old yeast", 5 g butter, 1.5 g salt, 8 g sugar, 0.5 g Angel Yeast, 60 g water and 1 g red date powder.

[0039] Example 2

[0040] 1) Preparation of fermented bacterial liquid of lactic acid bacteria: Pediococcus pentosaceus JS35 was first inoculated into MRS solid medium for culture activation, then inoculated into MRS liquid medium to obtain primary seed liquid, and then inoculated into NRS liquid medium for fermentation at a temperature of 40°C for 12 hours, and then the liquid medium containing the bacterial cells was centrifuged at 4°C and the supernatant was discarded to obtain enriched bacterial cells, and then the bacterial cells were rinsed and resuspended with sterile water and the bacterial cell concentration was adjusted to 10 8 cfu / mL, and the resuspension containing the bacteria is the lactic acid bacteria fermentation solution in the subsequent work;

[0041] 2) Preparation of yeast fermentation broth: Saccharomyces cerevisiae was inoculated into YPD solid medium for activation, then inoculated into YPD liquid medium to obtain primary seed solution, and then inoculated into YPD liquid medium for fermentation at a temperature of 30°C for 24 hours. The liquid medium containing the cells was then centrifuged at 4°C and the supernatant was discarded to obtain enriched cells. The cells were then rinsed with sterile water and resuspended to adjust the cell concentration to 10 6 cfu / mL, the resuspension containing the bacteria is the yeast fermentation broth in the subsequent work;

[0042] 3) mixing the lactic acid bacteria fermentation liquid and the yeast fermentation liquid in equal volume ratios and setting aside;

[0043] 4) Put the expiring super-alcohol toast bread (shelf life 3 days, 0.5 day near expiration) into a dough mixer, and then add a citric acid solution with a pH value of 4.5 at a ratio of 35g citric acid per 100g bread to knead the dough, so that the expiring bread becomes a soft, loose and moist dough;

[0044] 5) Heat the dough to 65°C and keep it warm and moist for 30 minutes;

[0045] 6) Cool the heated dough to 30°C, then spray the mixed fermentation liquid from step 3) while kneading the dough. The addition ratio is 15g of liquid per 100g of bread, and ensure that the number of Pediococcus pentosaceus reaches 10 6 cfu / g bread or more;

[0046] 7) The dough sprayed with the mixed bacterial solution is placed in an environment of 26°C and cultured for 30 hours to prepare an "old yeast" containing live bacteria.

[0047] 8) Bread was produced according to the formula of 100 g wheat flour, 25 g of the above-mentioned "old yeast", 5 g butter, 1.5 g salt, 8 g sugar, 60 g water and 1 g red date powder.

[0048] Example 3

[0049] 1) Preparation of fermented bacterial liquid of lactic acid bacteria: Pediococcus pentosaceus JS35 was first inoculated into MRS solid medium for culture activation, then inoculated into MRS liquid medium to obtain primary seed liquid, and then inoculated into MRS liquid medium for fermentation at a temperature of 28° C. for 30 h, and then the liquid medium containing bacterial cells was centrifuged at 4° C. and the supernatant was discarded to obtain enriched bacterial cells, and then the bacterial cells were rinsed and resuspended with sterile water and the bacterial cell concentration was adjusted to 10 8 cfu / mL, and the resuspension containing the bacteria is the lactic acid bacteria fermentation solution in the subsequent work;

[0050] 2) Preparation of yeast fermentation broth: Saccharomyces cerevisiae was inoculated into YPD solid medium for activation, then inoculated into YPD liquid medium to obtain primary seed solution, and then inoculated into YPD liquid medium for fermentation at a temperature of 25°C for 48 hours. The liquid medium containing the cells was then centrifuged at 4°C and the supernatant was discarded to obtain enriched cells. The cells were then rinsed with sterile water and resuspended to adjust the cell concentration to 10 6 cfu / mL, the resuspension containing the bacteria is the yeast fermentation broth in the subsequent work;

[0051] 3) mixing the lactic acid bacteria fermentation liquid and the yeast fermentation liquid in equal volume ratios and setting aside;

[0052] 4) Put the whole wheat toast bread (shelf life 3 days, 0.5 day near expiration) into a dough mixer, and then add a citric acid solution with a pH value of 4.5 at a ratio of 45g citric acid per 100g bread to knead the dough, so that the expiring bread becomes a soft, loose and moist dough;

[0053] 5) Heat the dough to 65°C and keep it warm and moist for 40 minutes;

[0054] 6) Cool the heated dough to 30°C, then spray the mixed fermentation liquid from step 3) while kneading the dough. The addition ratio is 25g of liquid per 100g of bread, and ensure that the number of Pediococcus pentosaceus reaches 10 7 cfu / g bread or more;

[0055] 7) The dough sprayed with the mixed bacterial solution is placed in an environment of 32°C and cultured for 16 hours to prepare "old yeast" containing live bacteria.

[0056] 8) Bread was produced according to the formula of 100 g wheat flour, 20 g of the above-mentioned "old yeast", 6 g butter, 1 g salt, 10 g sugar, 0.5 g Angel Yeast, 55 g water, and 1 g red date powder.

[0057] Example 4

[0058] 1) Preparation of fermented bacterial liquid of lactic acid bacteria: Pediococcus pentosaceus JS35 was first inoculated into MRS solid medium for activation, then inoculated into MRS liquid medium to obtain primary seed liquid, and then inoculated into MRS liquid medium for fermentation at 37°C for 30h, and then the liquid medium containing bacterial cells was centrifuged at 4°C and the supernatant was discarded to obtain enriched bacterial cells, and then the bacterial cells were rinsed and resuspended with sterile water and the bacterial cell concentration was adjusted to 10 8 cfu / mL, and the resuspension containing the bacteria is the lactic acid bacteria fermentation solution in the subsequent work;

[0059] 2) Preparation of yeast fermentation broth: Saccharomyces cerevisiae was inoculated into YPD solid medium for activation, then inoculated into YPD liquid medium to obtain primary seed solution, and then inoculated into YPD liquid medium for fermentation at a temperature of 25°C for 48 hours. The liquid medium containing the cells was then centrifuged at 4°C and the supernatant was discarded to obtain enriched cells. The cells were then rinsed with sterile water and resuspended to adjust the cell concentration to 10 6 cfu / mL, the resuspension containing the bacteria is the yeast fermentation broth in the subsequent work;

[0060] 3) mixing the lactic acid bacteria fermentation liquid and the yeast fermentation liquid in equal volume ratios and setting aside;

[0061] 4) Put the soft European bread (shelf life 2 days, near expiration 0.5 day) into a dough mixer, and then add a citric acid solution with a pH value of 4.5 at a ratio of 40g citric acid per 100g bread to knead the dough, so that the near expiration bread becomes a soft, loose and moist dough;

[0062] 5) Heat the dough to 65°C and keep it warm and moist for 40 minutes;

[0063] 6) Cool the heated dough to 30°C, then spray the mixed fermentation liquid from step 3) while kneading the dough. The addition ratio is 20g of liquid per 100g of bread, and ensure that the number of Pediococcus pentosaceus reaches 10 6 cfu / g bread or more;

[0064] 7) The dough sprayed with the mixed bacterial solution is placed in an environment of 30°C and cultured for 24 hours to prepare "old yeast" containing live bacteria.

[0065] 8) Bread was produced according to the formula of 100 g bread flour, 30 g of the above-mentioned "old yeast", 4 g butter, 1 g salt, 6 g sugar, 55 g water and 1 g red date powder.

[0066] While making the bread of Examples 1 to 4, bread was made with bread flour (purchased from the market) as the main ingredient and Angel yeast (purchased from the market) as the leavening agent as a control group. The formula of the control group is as follows: 100g bread flour, 2g Angel yeast, 5g butter, 1g salt, 8g sugar, 60g water, and 1g red date powder.

[0067] Two groups of positive controls were prepared. Positive control group 1: Lactobacillus plantarum is a strain commonly used in the industry to make "old yeast". This positive control uses Lactobacillus plantarum HH-LP56 (patent publication number is CN115428908A) to replace Pediococcus pentosaceus JS35 in Example 1 to carry out the experiment, and other experimental parameters are consistent with Example 1. Positive control group 2: Another strain of Pediococcus pentosaceus (Pediococcus pentosaceus, purchased from Shaanxi Zhenghe Pharmaceutical Bioengineering Co., Ltd., patent publication number CN117757658A) is used to replace Pediococcus pentosaceus JS35 in Example 1 to carry out the experiment, and other experimental parameters are consistent with Example 1.

[0068] The specific implementation effects of the control group, positive control group 1, positive control group 2, and embodiments 1 to 4 are as follows Figure 1 shown.

[0069] from Figure 1It can be seen that the shapes of the breads in each group are good. Among them, the gaps in the control group and Example 1 are smaller. The gaps in Examples 3 and 4 are larger and appear fluffy. Organize 6 people in the food industry to conduct sensory evaluation. The overall acceptance of the bread is scored from the appearance, internal structure, taste, flavor, and color, with a score range of 1 to 9. The smaller the score, the lower the acceptance, and the higher the score, the higher the acceptance. The specific effects are shown in Table 1.

[0070] Table 1 Effects of each embodiment and control

[0071]

[0072] Note: a~d in the table are symbols of significant difference, and different letters in the vertical column indicate that the data are statistically different (P<0.05).

[0073] The sensory scores of the control group and each embodiment group are not much different, but the score of the positive control group is lower. The specific volume in the table refers to: volume (mL) / mass (g) of bread. The larger the specific volume, the better the fluffy effect of the bread. From the data in the table, it can be seen that the specific volume of each embodiment group is above 3, which means that the fluffy effect of the bread is good, which is consistent with the effect of commercial yeast fermentation and better than the bread made by Lactobacillus plantarum fermentation. In particular, compared with the positive control, the bread specific volume of Example 1 made with the same formula has a significant difference (P<0.05).

[0074] Among them, the aging rate in the table refers to: Bsd = (B 5d -B 1d ) / B 1d ×100%, B 5d is the hardness of the bread slice after refrigeration at 4℃ for 5 days, B 1d It is the hardness of the bread slice on the first day. The hardness is measured by a texture analyzer and represents the maximum force felt when the probe of the texture analyzer is pressed down. The larger the value of the aging rate, the more likely the bread is to age, indicating that the taste of the bread is more likely to deteriorate after being placed. The aging rate of each embodiment group is significantly lower than that of the control group. Compared with the positive control group, the aging rate of Example 1 made with the same formula is significantly reduced (P<0.05).

[0075] Each group of bread was placed in a food sealing bag and stored at room temperature for 48 hours. Then, microbiological tests were performed according to the national standard GB7099-2015. The mold counts of each group met the national standard (<150 cfu / g).

[0076] The time of mold appearance refers to: placing the bread slices of each group at room temperature and away from light, observing them every 6 hours, and observing the time when mold plaques appear with the naked eye and recording them.

[0077] Example 5

[0078] 1) Preparation of lactic acid bacteria fermentation liquid: Pediococcus pentosaceus JS35 was first inoculated into MRS solid medium for culture activation, then inoculated into MRS liquid medium to obtain primary seed liquid, and then inoculated into MRS liquid medium for fermentation at a temperature of 37° C. for 24 h, and then the liquid medium containing the bacteria was centrifuged at 4° C. and the supernatant was discarded to obtain enriched bacteria, and then the bacteria were rinsed with sterile water and resuspended to adjust the concentration of the bacteria to 10 8 cfu / mL, and the resuspension containing the bacteria is the lactic acid bacteria fermentation solution in the subsequent work;

[0079] 2) Preparation of yeast fermentation broth: Saccharomyces cerevisiae was inoculated into YPD solid medium for activation, then inoculated into YPD liquid medium to obtain primary seed solution, and then inoculated into YPD liquid medium for fermentation at 28°C for 48h. The liquid medium containing the cells was then centrifuged at 4°C and the supernatant was discarded to obtain enriched cells. The cells were then rinsed with sterile water and resuspended to adjust the cell concentration to 10 6 cfu / mL, the resuspension containing the bacteria is the yeast fermentation broth in the subsequent work;

[0080] 3) mixing the lactic acid bacteria fermentation liquid and the yeast fermentation liquid in equal volume ratios and setting aside;

[0081] 4) Put the expiring toast bread (with one day beyond the shelf life) into a dough mixer, and then add a citric acid solution with a pH value of 4.5 at a ratio of 40 g citric acid per 100 g bread to knead the dough, so that the expiring bread becomes a soft, loose and moist dough;

[0082] 4) Heat the dough to 65°C and keep it warm and moist for 30 minutes;

[0083] 5) Cool the heated dough to 30°C, then spray the mixed fermentation liquid from step 3) while kneading the dough. The addition ratio is 20g of liquid per 100g of bread, and ensure that the number of Pediococcus pentosaceus reaches 10 6 cfu / g bread or more;

[0084] 6) The dough sprayed with the mixed bacterial solution is placed in an environment of 30°C and cultured for 24 hours to prepare an "old yeast" containing live bacteria.

[0085] 7) Steamed bread was produced according to the formula of ① 105g whole wheat flour, 85g high-gluten flour, 2g Angel Yeast, and 95g water; ② 99g whole wheat flour, 81g high-gluten flour, 20g Pediococcus JS35 "old yeast", and 85g water; ③ 88g whole wheat flour, 72g high-gluten flour, 40g Pediococcus JS35 "old yeast", 4g purple potato powder, and 70g water; ④ 77g whole wheat flour, 63g high-gluten flour, 60g Pediococcus JS35 "old yeast", 6g purple potato powder, and 50g water. ⑤ 77g whole wheat flour, 63g high-gluten flour, 60g Lactobacillus plantarum "old yeast" (the "old yeast" was made by using Lactobacillus plantarum instead of Pediococcus JS35), 6g purple potato powder, and 50g water. ⑥ Steamed bread is produced with a formula of 77g whole wheat flour, 63g high-gluten flour, 60g "old yeast" of Pediococcus pentosaceus (the "old yeast" is made by using Pediococcus pentosaceus purchased from Shaanxi Zhenghe Pharmaceutical Bioengineering Co., Ltd. to replace Pediococcus pentosaceus JS35), 6g purple sweet potato powder, and 50g water. Among them, ① is a control group of steamed bread fermented with commercial yeast instead of "old yeast". ② is steamed bread that uses Pediococcus pentosaceus JS35 "old yeast" to replace most of the commercial yeast. ③ and ④ completely replace the commercial yeast by adding a larger proportion of "old yeast", and purple sweet potato powder is added to increase the color and flavor of the product. ⑤ and ⑥ are used as positive controls to investigate the application differences caused by the strains. The specific effects are as follows.

[0086] Table 2 Steamed bread made with different recipes

[0087]

[0088] Note: a~e in the table are symbols of significant difference, and different letters in the vertical column indicate that the data are statistically different (P<0.05).

[0089] from Figure 2 As can be seen from the data in Table 2, the steamed bread in each group was well fermented and had good appearance and texture. The specific volume of each group exceeded the national standard of 1.7, among which the specific volume of group ③ was the highest, while that of group ⑥ was the lowest. The "old yeast" steamed bread in group ② had a slightly lower specific volume than the control group (group ①) due to the addition of less "old yeast", but the difference was not significant (P>0.05); and as can be seen from the picture, the pores were slightly smaller than those in the control group. In group ③, the amount of "old yeast" added was large, so the steamed bread produced by fermentation had a large specific volume and uniform pores. In terms of aging speed, groups ②, ③, and ④ using "old yeast" were better than the control group, and the aging speed was significantly reduced. The specific volume of group ④ was significantly higher than that of groups ⑤ and ⑥ (positive control group), and the aging speed was significantly lower than that of groups ⑤ and ⑥ (positive control group). This is because Pediococcus pentosaceus JS35 can better utilize expired bread as a fermentation substrate and metabolize more polysaccharides.

[0090] DPPH free radical scavenging rate is an important indicator of antioxidant activity. From the perspective of DPPH free radical scavenging rate, the scavenging rates of groups ②, ③, ④, and ⑤ were significantly higher than those of the commercial yeast control group (group ①). This may be due to the production of more active antioxidant substances such as peptides, amino acids, and polysaccharides during the fermentation of "old yeast". In addition, the DPPH scavenging rates of groups ③ and ④ were significantly higher than those of group ②, which may be due to the addition of more "old yeast" and the presence of purple sweet potato powder. The DPPH scavenging rate of group ④ was significantly higher than that of groups ⑤ and ⑥. This is because more active antioxidant substances such as peptides and polysaccharides were produced during the metabolism of Pediococcus pentosaceus JS35.

[0091] The coliform bacteria and mold counts in the table are all carried out in accordance with the national standard "Food Hygiene Microbiology Inspection". The objects tested are steamed buns that have been naturally cooled in the steamer, then transferred to a clean food preservation bag, sealed and placed at room temperature for 24 hours. It can be seen that the above steamed buns meet the national hygiene standards.

[0092] The specific volume in the table refers to: volume (mL) / mass (g) of the steamed bun. The larger the specific volume, the better the steamed bun will be in a fluffy state.

[0093] The aging rate in the table refers to: BSd = (B 3d -B 1d ) / B 1d ×100%, B 3d is the hardness of the steamed bread slices after being refrigerated at 4℃ for 3 days, B 1d It is the hardness of the steamed bread slices on the first day. The hardness is measured by a texture analyzer and represents the maximum force felt when the probe of the texture analyzer is pressed down. The larger the value of the aging speed, the easier it is for the steamed bread to age, and the worse the taste will be after being placed for the same time.

[0094] The measurement method of DPPH free radical scavenging rate in the table is as follows: accurately weigh DPPH powder and prepare a 100μmol / L DPPH solution with methanol, and store it in the dark. Take 0.2mL of sample extract (methanol extract of steamed bread freeze-dried powder: steamed bread and 80% methanol are shaken and extracted for 2h at a mass volume ratio of 1g:10mL, and then centrifuged to take the supernatant; extract twice and combine the supernatants to obtain the sample extract), add 0.8mL of methanol, mix well, then add 1mL of DPPH solution, mix well, react at room temperature in the dark for 30min, and measure the absorbance at 517nm as the sample group (A 517 ); 1 mL DPPH solution was added with 1 mL methanol as the control group (A max ); 0.2 mL of the sample with the same mass concentration and 1.8 mL of methanol were used as the blank group (A0). The calculation formula is as follows: DPPH free radical scavenging rate % = (1-(A517 -A0) / A max )×100%. The DPPH free radical scavenging rate is an indicator of the antioxidant properties of the material. The larger the value, the better the antioxidant property of the sample.

Claims

1. A method for treating expiring bread using Pediococcus pentosaceus JS35, characterized in that: The following steps are involved: (1) mixing a fermentation liquid of Pediococcus pentosaceus JS35 and a fermentation liquid of Saccharomyces cerevisiae to obtain a mixed liquid; (2) Heat the expiring bread to acidify it, keep it warm and moisturize it, add the mixed bacterial solution described in step (1) after cooling, let it stand, and obtain old yeast.

2. The method according to claim 1, characterized in that: The concentration of Pediococcus pentosaceus JS35 in the Pediococcus pentosaceus JS35 fermentation broth in step (1) is 10 8 cfu / mL or more; the concentration of yeast in the yeast (Saccharomyces cerevisiae) fermentation broth is 10 6 cfu / mL or above.

3. The method according to claim 1, characterized in that: The method for acidifying the expiring bread in step (2) is as follows: the expiring bread is adjusted to be acidic by using an acidity adjuster; the acidity adjuster includes citric acid, vinegar or malic acid.

4. The method according to claim 3, characterized in that: The mass ratio of bread to acidity adjustment is 100:35-45.

5. The method according to claim 3, characterized in that: The pH value of the acidity adjuster is 4.5-5.

0.

6. The method according to claim 1, characterized in that: The time of heat preservation and moisture retention in step (2) is 30 to 40 minutes.

7. The method according to claim 1, characterized in that: The mass ratio of the expiring bread to the mixed bacterial liquid in step (2) is 100:15-25.

8. The method according to claim 1, characterized in that: The standing temperature is 26-32°C and the time is 16-30 hours.

9. An old ferment prepared by the method according to any one of claims 1 to 8.

10. The old yeast according to claim 9 is used to prepare fermented cereal products, characterized in that: The fermented cereal products include bread, steamed bread or noodles.

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