CN110915920A - Method for improving stability of set yogurt - Google Patents
Method for improving stability of set yogurt Download PDFInfo
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- CN110915920A CN110915920A CN201911165432.7A CN201911165432A CN110915920A CN 110915920 A CN110915920 A CN 110915920A CN 201911165432 A CN201911165432 A CN 201911165432A CN 110915920 A CN110915920 A CN 110915920A
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23C—DAIRY PRODUCTS, e.g. MILK, BUTTER OR CHEESE; MILK OR CHEESE SUBSTITUTES; MAKING THEREOF
- A23C9/00—Milk preparations; Milk powder or milk powder preparations
- A23C9/12—Fermented milk preparations; Treatment using microorganisms or enzymes
- A23C9/13—Fermented milk preparations; Treatment using microorganisms or enzymes using additives
- A23C9/137—Thickening substances
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Abstract
The invention discloses a method for improving the stability of set yogurt. The method comprises the steps of firstly pretreating thermal gel by an alkali dissolution method to obtain a gel solution, then adding the gel solution into raw milk, and sequentially mixing, thermally treating, inoculating zymophyte, standing and fermenting to obtain the set yoghurt. The method is simple and convenient to operate, the added thermal gel does not influence the fermentation activity of the thalli and the quality of the yogurt, and after the thermal gel is added, the stability of the set yogurt is obviously improved, the whey separation phenomenon disappears, the gel strength is improved, and the method has a good application prospect.
Description
Technical Field
The invention belongs to the technical field of polysaccharide application, and relates to a method for improving the stability of set yogurt.
Background
The dairy product plays an important role in optimizing the dietary structure of residents, reducing the risks of various diseases and the like. Because the proportion of people with lactose indigestion/intolerance in China is higher than that in European and American countries, fermented milk and prepared milk are more and more favored by domestic consumers. Wherein, the fermented yoghourt accounts for a larger proportion in production and eating. However, whey separation, deterioration of rheological properties, and the like often occur in milk products during fermentation.
The study finds that the casein gel system stability deterioration in the fermentation acidification process is the main reason for the whey separation. The electrostatic repulsion force between casein colloidal particles in a natural state maintains the colloidal particles to be relatively stable. In the acidification process, the colloidal calcium phosphate in the colloidal particles is gradually dissolved out, and the net negative charge of the colloidal particles is reduced, so that the structure is gradually destabilized. The reduction of the gaps among the colloidal particles produces an emptying effect, so that the hydration degree is reduced, part of protein molecules, fat particles and the like are extruded, and the whey separation phenomenon is generated. This phenomenon is particularly evident in set yoghurts. Therefore, it is usually necessary to add stabilizers (such as gelatin, agar, etc. in common) to improve the stability and taste of the product.
Thermal gel (curdlan gum), also known as curdlan gum, curdlan, etc.) is extracellular linear β -1, 3-glucan secreted by alcaligenes faecalis, contains no or a small amount of glucose side chain, is insoluble in water and soluble in a higher concentration of alkali liquor.
Disclosure of Invention
The invention aims to provide a method for improving the stability of set yogurt. According to the method, the thermal gel is added into the raw milk and is subjected to heat treatment, and an additional network structure formed by the thermal gel can strengthen the stability of casein colloidal particles in the milk, reduce the whey separation phenomenon in the fermentation and acidification processes, improve the stability of set yogurt and improve the quality of yogurt.
The technical scheme for realizing the purpose of the invention is as follows:
a method for improving the stability of set yogurt comprises the following steps:
step 1, dissolving thermal gel in alkali liquor to prepare storage liquid;
step 2, fully mixing the storage liquid with raw milk, and adjusting the pH value to 6.0-7.0;
step 3, heating the mixed solution obtained in the step 2 at 75-90 ℃ for 5-60 min, and then cooling to a proper growth temperature of the zymocyte;
and 4, inoculating zymophyte into the treatment liquid obtained in the step 3 for fermentation to obtain the set yogurt.
Preferably, in step 1, the thermal gel is a linear β -1, 3-glucan having a branch content (in terms of mole ratio of branches to repeating sugar units) of not greater than 1/6 and a weight average molecular weight greater than 3000 Da.
Preferably, in the step 1, the concentration of the thermal gel in the storage solution is 20-50 g/L.
Preferably, in the step 1, the alkali solution is a mixed aqueous solution of sodium hydroxide or sodium hydroxide and potassium hydroxide, the total concentration is 0.05-0.5 mol/L, and the sodium hydroxide aqueous solution is more preferred.
In step 2 of the invention, the raw milk is the conventional raw milk used in the preparation of fermented yogurt, and may be one or a mixture of several of fresh milk, skimmed or partially skimmed milk, whole milk powder, skimmed or partially skimmed milk powder.
Preferably, in the step 2, the final concentration of the thermal gel in the mixed solution is 0.5-10 g/L, and more preferably 0.5-5 g/L.
Preferably, in step 2, the stock solution is mixed with the raw milk, and the mixing can be realized by stirring, high-speed homogenization or high-pressure homogenization.
Preferably, in the step 2, the pH is adjusted to 6.5-6.9.
Preferably, in the step 3, the heating time is 20-35 min.
Preferably, in the step 3, the suitable growth temperature of the zymophyte is 30-45 ℃, and more preferably 42 ℃.
Preferably, in step 4, the fermentation bacteria are lactobacillus and streptococcus thermophilus.
Preferably, in the step 4, the fermentation time is 6-8 h.
When the thermal gel-water system is heated to 55-60 ℃, thermally reversible gel (LSG) is formed, and when the thermal gel-water system is continuously heated to about 80 ℃, thermally irreversible gel (HSG) is formed. LSG has properties similar to agar, and gels melt when heated and reform when cooled. And HSG forms a stable intermolecular network structure through hydrogen bonds, and the structure is not influenced by repeated heating and has good structural strength. The invention utilizes the property of thermal gel to fully disperse the thermal gel in the raw milk, and finally the set yoghurt with obviously enhanced stability is obtained.
Compared with the prior art, the invention has the following advantages:
(1) the thermal gel after heat treatment can form a good gel network structure, can endure subsequent repeated heating treatment, and has good compatibility with the heat treatment process before fermentation of the yoghourt;
(2) after the thermal gel is added, the stability of the set yogurt is obviously improved, the whey separation phenomenon disappears, and the gel strength is improved;
(3) the method is simple and convenient to operate, the thermal gel can be formed into gel only by heat treatment, inorganic ions do not need to be added additionally, only one-step mixing operation needs to be added in the conventional pretreatment process, and the product has stable quality, good repeatability and good application value.
Drawings
FIG. 1 is a graph comparing the viability of strains in yogurt with added heat gel to control yogurt in a flow cytometry analysis.
FIG. 2 is a scanning electron microscope image of a thermogelling yogurt with control yogurt.
Detailed Description
The invention is further illustrated by the following specific examples and the accompanying drawings.
Thermal gels were purchased from Shandong, Zhongke Biotech, Inc., model ZKC-3.
Example 1
First, the thermal gel was dissolved in 0.5mol/L sodium hydroxide solution to prepare a stock solution having a concentration of 40 g/L. Then, the whole milk powder was dissolved in water to prepare reconstituted milk containing 35g/L protein. The thermal gel stock solution was mixed with reconstituted milk to give a final concentration of thermal gel of 2 g/L. The two were mixed thoroughly by high speed homogenization and the pH was adjusted to 6.5. Then, heat to 75 ℃ and hold for 35 min. Cooling to 45 deg.C, inoculating fermenting bacteria selected from Lactobacillus and Streptococcus thermophilus, standing, and fermenting. After 8h, the fermentation was completed, the viability of the cells after the fermentation was analyzed by flow cytometry, using set yoghurt without addition of thermal gel as a control.
1g of fermented yogurt is taken, 49mL of phosphate buffer (pH7.0) is added, the mixture is sufficiently shaken, and then the cells are collected by centrifugation. The cells were resuspended in 50mL of phosphate buffer (pH7.0) and dispersed by sonication, then stained with SYBR Green I and Propidium Iodide (PI) fluorochrome (room temperature in the dark for 15min), followed by detection of cell activity by flow cytometry. The results are shown in FIG. 1, where SYBR Green I/PI double positive (S +, P +) indicates a broken cell membrane, labeled as dead; SYBR Green I positive/PI negative (S +, P-) indicates cells with normal permeability of the cell membrane and are labeled as viable cells. The results show that the proportion of living cells is slightly increased after the hot gel is added, which indicates that the method does not influence the normal fermentation of the yoghourt.
Example 2
First, the thermal gel was dissolved in 0.01mol/L sodium hydroxide solution to prepare a stock solution having a concentration of 10 g/L. Then, the whole milk powder is dissolved by water to prepare reconstituted milk containing 100g/L of protein, and fresh milk and the reconstituted milk are compounded to prepare raw milk with 40g/L of protein content. Mixing the thermal gel stock solution and reconstituted milk according to different volume ratios so that the final concentration of the thermal gel is 0.5g/L, 2g/L and 5g/L respectively, fully mixing the two by using high-speed homogenate, and adjusting the pH value to 6.9. Then, it was heated to 90 ℃ and kept for 20 min. Cooling to 35 deg.C, inoculating zymocyte, standing, and fermenting. And after 8h of fermentation, measuring the water holding capacity of the yogurt, and taking the set yogurt without adding the thermal gel as a control. The results are shown in Table 1, and it is understood that the water holding capacity of the yogurt is significantly increased by adding the thermogel.
TABLE 1 set-style yogurt Water holding Capacity
Example 3
First, the thermal gel was dissolved in 0.1mol/L sodium hydroxide solution to prepare a stock solution having a concentration of 30 g/L. Then, the hot gel stock solution and fresh milk were mixed in a volume ratio of 1:9, and the two were thoroughly mixed using high pressure homogenization, and the pH was adjusted to 6.7. Then, it was heated to 80 ℃ and kept for 30 min. Cooling to 30 deg.C, inoculating zymocyte, standing, and fermenting. And after 8h, fermenting, observing the microstructure of the yoghourt by adopting a scanning electron microscope, and taking the set yoghourt without adding thermal gel as a reference. The results are shown in fig. 2, from which it can be seen that the yoghurt has a typical layered lattice structure, which is a protein gel network formed by casein micelles. After the thermal gel is added, the filamentous network formed by the sugar is obviously increased in the middle of the network, which shows that the thermal gel has strengthening effect on the protein network.
Example 4
In this example, the sample texture TPA data was measured after fermentation was completed in exactly the same way as the yogurt fermentation process of example 1, and set yogurt without addition of hot gel was used as a control. Measuring yogurt with FTC TES-TOUCH texture analyzer, and measuring yogurt with cylindrical probe with flat end diameter of 50 mm; probe descent speed before test: 1.0 mm/s; testing speed: 1.0 mm/s; the return speed of the probe after the test is as follows: 1.0 mm/s; deformation amount: 30 percent; trigger force: 5g of the total weight. The results are shown in Table 2. The results show that the indexes of the yoghourt sample added with the thermal gel compound are obviously improved, and the yoghourt sample shows good structural stability. Indicating that the thermal gel can enhance the structural stability of the yoghurt.
The texture parameters used in this experiment were: (1) hardness, refers to the pressure peak in the first punch sample. (2) Cohesion, which simulates the internal adhesion of the sample, is the relative resistance of the sample to the second compression exhibited after the first compression set. (3) Elasticity is the ratio of the height of the sample before it returns to its original shape after removal of the pressure. (4) The tackiness, which is used to simulate the energy required to break a semi-solid sample into a stable state for swallowing.
TABLE 2 comparison of texture results for conventional yogurt and thermal gel fortified yogurt
| hardness/N | Cohesion property | Elasticity/mm | tackiness/N | |
| Control yogurt | 0.52 | 0.4 | 3.49 | 0.21 |
| Hot gel yoghurt | 1.79 | 0.4 | 4.87 | 0.69 |
Comparative example 1
Hot gel fortified yoghurt was prepared by fermentation according to the method of example 1 and then by the same method yoghurt containing the same concentration of gelatin and agar, respectively, was prepared as a control. The TPA data was then tested for 3 samples as in example 4 and the results are shown in table 3. It can be seen that the three polymers all enhance the stability of the set yoghurt, and simultaneously, the hardness and adhesiveness of the set yoghurt added with the thermal gel are superior to those of the common gelatin and agar yoghurt. The result shows that the thermal gel added according to the method can play a role in improving the stability of the set yoghurt.
TABLE 3 TPA data comparison of three Polymer fortified yoghurts
| hardness/N | Cohesion property | Elasticity/mm | tackiness/N | |
| Gelatin yoghourt | 1.12 | 0.4 | 5.18 | 0.4 |
| Agar yoghurt | 1.16 | 0.4 | 4.22 | 0.48 |
| Hot gel yoghurt | 1.79 | 0.4 | 4.87 | 0.69 |
Claims (10)
1. A method for improving the stability of set yogurt is characterized by comprising the following steps:
step 1, dissolving thermal gel in alkali liquor to prepare storage liquid;
step 2, fully mixing the storage liquid with raw milk, and adjusting the pH value to 6.0-7.0;
step 3, heating the mixed solution obtained in the step 2 at 75-90 ℃ for 5-60 min, and then cooling to a proper growth temperature of the zymocyte;
and 4, inoculating zymophyte into the treatment liquid obtained in the step 3 for fermentation to obtain the set yogurt.
2. The method of claim 1, wherein in step 1, the thermal gel is a linear β -1, 3-glucan having a branched chain content of not greater than 1/6 and a weight average molecular weight of greater than 3000 Da.
3. The method of claim 1, wherein in step 1, the concentration of the thermal gel in the storage solution is 20-50 g/L.
4. The method according to claim 1, wherein in the step 1, the alkali liquor is sodium hydroxide or a mixed aqueous solution of sodium hydroxide and potassium hydroxide, the total concentration is 0.05-0.5 mol/L, and the sodium hydroxide aqueous solution is more preferable.
5. The method of claim 1, wherein in step 2, the raw milk is one or more of fresh milk, skimmed or partially skimmed milk, whole milk powder, skimmed or partially skimmed milk powder.
6. The method according to claim 1, wherein in step 2, the final concentration of the thermal gel in the mixed solution is 0.5-10 g/L, and more preferably 0.5-5 g/L.
7. The method of claim 1, wherein in step 2, the stock solution is mixed with the raw milk by stirring, high speed homogenization, or high pressure homogenization.
8. The method according to claim 1, wherein in the step 2, the pH is adjusted to 6.5-6.9; in the step 3, the heating time is 20-35 min.
9. The method according to claim 1, wherein the suitable growth temperature of the zymophyte in step 3 is 30-45 ℃, more preferably 42 ℃.
10. The method according to claim 1, wherein in the step 4, the fermentation bacteria are lactobacillus and streptococcus thermophilus, and the fermentation time is 6-8 h.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04158752A (en) * | 1990-10-23 | 1992-06-01 | Snow Brand Milk Prod Co Ltd | Method for preparing curdlan thermally coagulated gel product |
| JPH09191837A (en) * | 1996-01-19 | 1997-07-29 | Meiji Milk Prod Co Ltd | Fermented milk product desert and its production |
| US5688775A (en) * | 1991-10-15 | 1997-11-18 | Fmc Corporation | β-1,3-glucan polysaccharides, compositions, and their preparation and uses |
| JP2005013212A (en) * | 2003-06-05 | 2005-01-20 | Sanei Gen Ffi Inc | Stabilizer for yoghurt and yoghurt containing the same |
| CN106070622A (en) * | 2016-07-06 | 2016-11-09 | 泰兴市东圣食品科技有限公司 | Yoghourt containing microbial source polyglucose and preparation method thereof |
| JP2019187270A (en) * | 2018-04-23 | 2019-10-31 | オルガノフードテック株式会社 | Curdlan-containing composition, product comprising curdlan-containing composition and method for producing product comprising curdlan-containing composition |
-
2019
- 2019-11-25 CN CN201911165432.7A patent/CN110915920A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04158752A (en) * | 1990-10-23 | 1992-06-01 | Snow Brand Milk Prod Co Ltd | Method for preparing curdlan thermally coagulated gel product |
| US5688775A (en) * | 1991-10-15 | 1997-11-18 | Fmc Corporation | β-1,3-glucan polysaccharides, compositions, and their preparation and uses |
| JPH09191837A (en) * | 1996-01-19 | 1997-07-29 | Meiji Milk Prod Co Ltd | Fermented milk product desert and its production |
| JP2005013212A (en) * | 2003-06-05 | 2005-01-20 | Sanei Gen Ffi Inc | Stabilizer for yoghurt and yoghurt containing the same |
| CN106070622A (en) * | 2016-07-06 | 2016-11-09 | 泰兴市东圣食品科技有限公司 | Yoghourt containing microbial source polyglucose and preparation method thereof |
| JP2019187270A (en) * | 2018-04-23 | 2019-10-31 | オルガノフードテック株式会社 | Curdlan-containing composition, product comprising curdlan-containing composition and method for producing product comprising curdlan-containing composition |
Non-Patent Citations (3)
| Title |
|---|
| CAMILA SAMPAIO MANGOLIM ET.AL: ""Description of recovery method used for curdlan produced by Agrobacterium sp. IFO 13140 and its relation to the morphology and physicochemical and technological properties of the polysaccharide"", 《PLOS ONE》 * |
| 吉武科等: "Curdlan凝胶机理研究进展", 《中国食品添加剂》 * |
| 陈艳燕等: "新型食品添加剂增稠剂―可得然胶在食品工业中的应用", 《中国食品添加剂》 * |
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Application publication date: 20200327 |