Production method of yogurt resistant to amylase pollution

Abstract

The invention relates to the technical field of food, in particular to a production method of amylase pollution resistant yoghourt. The invention provides a production method of yogurt resistant to amylase pollution. The production method comprises the following steps: pretreating milk, mixing the pretreated milk with hydroxy propyl distarch phosphate and an additive, carrying out first heat preservation and second heat preservation on a mixture obtained by mixing, cooling, and fermenting to obtain the yogurt, amylase exists in the additive; the temperature of the first heat preservation is 50-55 DEG C, and the time of the first heat preservation is 25-30 min; the temperature of the second heat preservation is 90-95 DEG C, and the time of the second heat preservation is 5-5 minutes and 20 seconds. When the additive is polluted by amylase and the amylase exists in the yoghourt production process, the influence of the amylase existing in the yoghourt production process on the viscosity of the produced yoghourt product can be avoided through the process and the condition, the viscosity of the prepared normal-temperature yoghourt can be kept stable for more than 180 days, and the worry of quality deterioration is avoided.

Description

Technical Field

[0001] The present application relates to the field of food technology, and in particular to a method for producing yogurt that is resistant to amylase contamination. Background Art

[0002] In 2020, the total sales volume of yogurt in China was about 4.37 million tons, with total sales of 97.5 billion yuan, of which the total sales of ambient temperature yogurt was 49.7 billion yuan. Common additives in the production of ambient temperature yogurt include white sugar, hydroxypropyl distarch phosphate, agar, sodium alginate, pectin, etc.

[0003] Hydroxypropyl distarch phosphate (E1442) is a modified starch widely used in the food industry. It has the functions of thickening, stabilization, and anti-freeze-thaw cycle. It is often used in dairy products such as yogurt, ice cream, cream and other dairy products. Hydroxypropyl distarch phosphate can improve the texture of the product, maintain the viscosity of the dairy product, make it smoother, and improve the taste. At the same time, it can also enhance acid resistance and freeze-thaw resistance, and extend the shelf life of the product.

[0004] However, in the process of preparing room temperature yogurt, it is easy to be contaminated by amylase. For example, trace amounts of starch hydrolyzing enzymes may exist in the additives added in the preparation process of room temperature yogurt, which may hydrolyze the stabilizer starch in the room temperature yogurt product, thereby reducing the viscosity of the room temperature yogurt when it is stored for a long time. Each additive has the possibility of containing various starch hydrolyzing enzymes. Therefore, in order to ensure the quality of room temperature yogurt, in the production process of room temperature yogurt, the influence of the accidental presence of amylase on the viscosity of room temperature yogurt caused by amylase contamination should be avoided as much as possible.

[0005] During the production of ambient temperature yogurt, trace amounts of amylases are present due to amylase contamination, mainly including Aspergillus oryzae α-amylase (ASa) from Aspergillus oryzae. Since it can break down starch into smaller sugars (such as maltose and glucose), it is difficult to completely inactivate it after being used in sucrose production. Therefore, when hydroxypropyl distarch phosphate (HPDSP) is used in ambient temperature yogurt, it is crucial to control the activity and effect of amylases when they are accidentally present due to amylase contamination during the production process. Summary of the invention

[0006] In order to solve the defects of the above-mentioned prior art, the present application studies the effects of different additives, heating processes, and amylase concentrations on the hydrolysis of starch by amylase, thereby developing a yogurt production method that can tolerate amylase contamination. When the yogurt is contaminated by amylase during the production process and the presence of amylase is caused, the process and conditions can still be used to ensure that the prepared ambient temperature yogurt can be stored at room temperature for more than 180 days and maintain stable viscosity, which is beneficial to avoid the impact of amylase contamination on product quality during the production of ambient temperature yogurt and maintain the good quality of ambient temperature yogurt products.

[0007] The first aspect of the present application provides a method for producing yogurt that is resistant to amylase contamination, comprising pretreating milk, mixing the pretreated milk with hydroxypropyl distarch phosphate and an additive, subjecting the mixture to a first heat preservation and a second heat preservation, cooling and then fermenting to obtain the yogurt; amylase is present in the additive, the first heat preservation temperature is 50-55°C, and the first heat preservation time is 25-30 minutes; the second heat preservation temperature is 90-95°C, and the second heat preservation time is 5min-5min20s.

[0008] The amylase is selected from ASa or Hea.

[0009] Preferably, based on the volume of the mixture, the concentration of ASa is ≤1 mU / mL, and the concentration of HEa is ≤0.001 mU / mL.

[0010] A second aspect of the present application provides a room temperature yogurt, which is prepared by the yogurt production method of the first aspect.

[0011] The third aspect of the present application provides use of the yogurt production method of the first aspect in yogurt production to tolerate amylase contamination.

[0012] The beneficial effects of this application are:

[0013] The steps of the additive and heating process in the yogurt production process of the present application are optimized. When the additive is contaminated by amylase and amylase is present during the yogurt production process, the process and conditions of the present application can avoid the influence of the amylase present in the yogurt production process on the viscosity of the produced yogurt product. When the yogurt is contaminated by amylase ASa during the production process and the amylase ASa concentration is ≤1mU / mL, or when the yogurt is contaminated by amylase HEa during the production process and the amylase HEa concentration is ≤0.001mU / mL, the process and conditions of the present application can avoid the influence of amylase contamination on the quality of the produced yogurt to the greatest extent. The present application can prepare room temperature yogurt at a lower temperature, and the produced room temperature yogurt can maintain a stable viscosity for more than 180 days without worrying about quality deterioration.

[0014] In traditional processing and production, starch and sucrose (white sugar) need to be UHT inactivated enzymes in advance before mixing raw materials and auxiliary materials to avoid amylase contamination, but this increases the energy consumption of production. The preparation method of the present application can accurately control the amylase content through process and conditions, removes the UHT inactivation procedure, can inactivate enzymes at a lower temperature, directly mix raw materials and auxiliary materials and sterilize enzymes at 95°C with low energy consumption, thereby reducing the excessive sterilization and inactivation of raw materials and auxiliary materials, with low energy consumption, short preparation cycle, simple method and low cost.

[0015] The method of the present application can be expanded to kilogram-level and ton-level reactions for industrial production, providing a new solution for the production of room-temperature yogurt that requires long-term room-temperature storage, and for avoiding the impact of amylase contamination on the quality of room-temperature yogurt products during the yogurt production process. DETAILED DESCRIPTION

[0016] The following describes the implementation of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application.

[0017] Before further describing the specific implementation methods of the present application, it should be understood that the scope of protection of the present application is not limited to the specific specific implementation methods described below; it should also be understood that the terms used in the examples of the present application are for describing specific specific implementation methods rather than for limiting the scope of protection of the present application; in the specification and claims of the present application, unless otherwise expressly stated herein, the singular forms "a", "an" and "the" include plural forms.

[0018] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present application, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present application, any method, equipment, and material of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present application can also be used to realize the present application.

[0019] The present application first provides a method for producing yogurt that is resistant to amylase contamination, comprising pretreating milk, mixing the pretreated milk with hydroxypropyl distarch phosphate and an additive, subjecting the mixture to a first heat preservation and a second heat preservation, cooling and then fermenting to obtain the yogurt; amylase is present in the additive; the temperature of the first heat preservation is 50-55°C, and the time of the first heat preservation is 25-30 minutes; the temperature of the second heat preservation is 90-95°C, and the time of the second heat preservation is 5 minutes to 5 minutes 20 seconds.

[0020] In a specific embodiment of the present application, the milk can be any milk suitable for fermenting yogurt, and the present application does not impose any restriction on it. For example, it can be raw cow's milk. The preparation method of ambient temperature yogurt provided in the present application can be expanded from an experimental system to industrial production conditions. There is no restriction on the amount of the milk used, and for example, it can be in grams, kilograms, or tons.

[0021] In a specific embodiment of the present application, the yogurt is room temperature yogurt, which generally refers to yogurt stored at room temperature.

[0022] In a specific embodiment of the present application, the pretreatment is heated to 55-58°C, maintained for 20-25min, and stirred at a speed of 1000-1200rpm. For example, it can be heated to 55-56°C, 56-57°C, 57-58°C; for example, it can be maintained for 20-21min, 21-22min, 22-23min, 23-24min, 24-25min; for example, the stirring speed can be 1000-1100rpm, 1100-1200rpm.

[0023] In a specific embodiment of the present application, the dosage of the hydroxypropyl distarch phosphate can be 1.5-3.0wt%, for example, it can be 1.5-1.6wt%, 1.6-1.7wt%, 1.7-1.8wt%, 1.8-1.9wt%, 1.9-2.0wt%, 2.0-2.1wt%, 2.1-2.2wt%, 2.2-2.3wt%, 2.3-2.4wt%, 2.4-2.5wt%, 2.5-2.6wt%, 2.6-2.7wt%, 2.7-2.8wt%, 2.9-3.0wt%.

[0024] In a specific embodiment of the present application, the amount of the additive can be 0.1 to 10 wt%, for example, 0.1 to 1 wt%, 1 to 2 wt%, 2 to 3 wt%, 3 to 4 wt%, 4 to 5 wt%, 5 to 6 wt%, 6 to 7 wt%, 7 to 8 wt%, 8 to 9 wt%, 9 to 10 wt%.

[0025] The present application does not limit the types of additives, which may be additives conventionally used in the production process of yogurt, such as sodium alginate, pectin, whey powder, apple jam, and white sugar.

[0026] In one embodiment of the present application, the additive is white sugar. When the additive is white sugar, the yogurt production process of the present application can avoid the influence of amylase contamination additive on the viscosity of the produced yogurt to the greatest extent, and the starch content in the yogurt is retained at the highest level.

[0027] In a specific embodiment of the present application, the presence of amylase in the additive means that the additive is contaminated with amylase, resulting in the accidental presence of unwanted amylase in the additive.

[0028] In a specific embodiment of the present application, the amylase is selected from ASa or HEa, that is, the amylase contaminated in the additive and present in the additive may be amylase ASa or amylase Hea.

[0029] When the additive is contaminated with amylase ASa and amylase Asa is present in the additive, the concentration of ASa is ≤1mU / mL based on the volume of the mixture before insulation. The yogurt production method of the present application can maintain the starch content in the prepared yogurt product and keep the viscosity of the prepared yogurt product stable during the shelf life.

[0030] The ASa concentration of ≤1mU / mL means that when the additive is contaminated with amylase or amylase is accidentally present in the additive, the final concentration of amylase Asa in the mixture of ingredients added before insulation is ≤1mU / mL, for example, it can be 0.1mU / mL, 0.01mU / mL, 0.001mU / mL, 0.0001mU / mL.

[0031] When the additive is contaminated with amylase HEa and amylase HEa is present in the additive, the concentration of HEa is ≤0.001 mU / mL based on the volume of the mixture before insulation. The yogurt production method of the present application can maintain the starch content in the prepared yogurt product and keep the viscosity of the prepared yogurt product stable during the shelf life.

[0032] The HEa concentration of ≤0.001mU / mL means that when the additive is contaminated by amylase or amylase is accidentally present in the additive, the final concentration of amylase HEa in the mixture of ingredients added before insulation is ≤0.001mU / mL, for example, it can be 0.0001mU / mL, 0.00001mU / mL, 0.000001mU / mL.

[0033] In a specific embodiment of the present application, the temperature of the first insulation can be 50-55°C, for example, 50-51°C, 51-52°C, 52-53°C, 53-54°C, 54-55°C.

[0034] In a specific embodiment of the present application, the first insulation time can be 25 to 30 minutes, for example, 25 to 26 minutes, 26 to 27 minutes, 27 to 28 minutes, 28 to 29 minutes, or 29 to 30 minutes.

[0035] In a specific embodiment of the present application, the temperature of the second insulation can be 90-95°C, for example, 90-91°C, 91-92°C, 92-93°C, 93-94°C, 94-95°C.

[0036] In a specific embodiment of the present application, the second insulation time can be 5min to 5min20s, for example, it can be 5min to 5min2s, 5min2s to 5min4s, 5min4s to 5min6s, 5min6s to 5min8s, 5min8s to 5min10s, 5min10s to 5min12s, 5min12s to 5min14s, 5min14s to 5min16s, 5min16s to 5min18s, 5min18s to 5min20s.

[0037] In the present application, a two-stage heating treatment is adopted, specifically, insulation at 50-55°C for 25 to 30 minutes and insulation at 90-95°C for 5min to 5min20s. In the first insulation, insulation at 50-55°C is conducive to the dissolution of raw materials and auxiliary materials. In the second insulation, insulation at 90-95°C for 5min to 5min20s can inactivate bacteria at a lower temperature and control the content of amylase, which is conducive to the smooth fermentation and maintaining the viscosity of yogurt. It is speculated that the above conditions change the physical and chemical properties of starch (such as gelatinization, degree of gelatinization, etc.), thereby affecting the efficiency of amylase hydrolyzing starch.

[0038] In a specific embodiment of the present application, the second insulation also includes stirring, and the stirring speed can be 200-300rpm, for example, 200-210rpm, 210-220rpm, 220-230rpm, 230-240rpm, 240-250rpm, 250-260rpm, 260-270rpm, 270-280rpm, 280-290rpm, 290-300rpm.

[0039] In a specific embodiment of the present application, the cooling is cooling to 40-44°C, for example, 40-41°C, 41-42°C, 42-43°C, 43-44°C.

[0040] In a specific embodiment of the present application, the fermentation includes adding a starter culture, and the starter culture includes Streptococcus thermophilus and Lactobacillus bulgaricus. Specifically, the starter culture is YO-MIX 883LYO 500DCU, for example, it can be a product of Danisco (DuPont Nutrition & Biosciences).

[0041] In a specific embodiment of the present application, the addition amount of the leavening agent is 0.3-0.5wt%, for example, it can be 0.3-0.35wt%, 0.35-0.4wt%, 0.4-0.45wt%, 0.45-0.5wt%.

[0042] In a specific embodiment of the present application, the fermentation time can be 5 to 6 hours, for example, 5 to 5.2 hours, 5.2 to 5.4 hours, 5.4 to 5.6 hours, 5.6 to 5.8 hours, or 5.8 to 6 hours.

[0043] In a specific embodiment of the present application, the fermentation temperature is 42-45°C, for example, 42-43°C, 43-44°C, or 44-45°C.

[0044] In a specific embodiment of the present application, the method further comprises sterilizing the weaned milk after fermentation, and the sterilization can be carried out according to routine methods in the art.

[0045] In the method of the present application, by screening and selecting, controlling the heating steps and time, the type and amount of additives, the effect of amylase hydrolyzing starch brought in by contamination during the production process can be accurately controlled to ensure the starch content in the prepared yogurt, thereby allowing the starch content in the prepared yogurt to remain stable for more than 180 days.

[0046] The present application also provides a room temperature yogurt, which is prepared by the above-mentioned yogurt production method, wherein the starch content in the room temperature yogurt can remain stable for more than 180 days, and the viscosity of the room temperature yogurt can remain stable for more than 180 days.

[0047] The present application also provides the use of the above-mentioned yogurt production method in yogurt production to tolerate amylase contamination. Through the above-mentioned production method, the effect of amylase hydrolyzing starch introduced due to the contamination of additives by amylase during the production process can be accurately controlled, thereby controlling the starch content in the produced yogurt product, so that the produced yogurt product maintains stable viscosity during the shelf life.

[0048] In a specific embodiment of the present application, the amylase contamination refers to the accidental introduction of amylase into the additive, and the amylase is selected from Asa or Hea. Based on the volume of the mixture to which each raw material and auxiliary material is added, the concentration of ASa is ≤1mU / mL, and the concentration of HEa is ≤0.001mU / mL.

[0049] The present application is further described below by specific examples. When the examples give numerical ranges, it should be understood that, unless otherwise specified in the present application, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as those commonly understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the examples, according to the technical staff of the present art's grasp of the prior art and the records of the present application, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the examples of the present application can also be used to implement the present application. Unless otherwise specified, the instruments, reagents, and materials used in the examples can be obtained by conventional means.

[0050] Materials, reagents and methods used in the examples:

[0051] Hydroxypropyl distarch phosphate: Modified starch hydroxypropyl distarch phosphate (HPDSP) is a modified starch (hydroxypropyl distarch phosphate) made from corn starch milk. This product complies with the relevant provisions of national standards GB29931 and GB 2760. It was purchased from Ingredion Food Ingredients Co., Ltd.

[0052] Enzyme reagent: Aspergillus oryzae α-amylase (ASa), α-amylase from Aspergillus oryzae was purchased from Sigma-Aldrich. Powder, ~30U / mg, 1 enzyme activity unit (U) is equivalent to the amount of enzyme required to release 1μmol maltose per minute at pH 6.0 and 25°C. Alias: 1,4-α-D-glucan-glucose hydrolase. Molecular weight: Mr ~ 51000. Microbial amylases are extracellular enzymes that can be used in a variety of industrial applications, such as bread and maltose syrup production, soy sauce and miso fermentation. The molecular weight of α-amylase isolated from Aspergillus oryzae is 51kDa (sedimentation and diffusion) and 49kDa (gel filtration).

[0053] α-Amylase, Heat Stable (HEa), from Bacillus licheniformis, 1,4-α-D-Glucan-glucohydrolase. 20000-60000U / mL, one unit will hydrolyze 1.0 mg maltose from starch at pH 6.9 in 3 minutes at 20°C. α-Amylase is an extracellular enzyme that is widely found in many natural sources such as animals and plants, and is particularly abundant in microorganisms, such as various Bacillus species. α-Amylase is a well-known thermostable alkaline enzyme. α-Amylase (1,4-α-d-glucohydrolase) is an endoglucanase and a member of glycoside hydrolase family 13 (GH13). α-Amylase (from Bacillus licheniformis NCIB 6346) retains >98% activity after 60 minutes at pH 6.2 and 85°C.

[0054] Preparation of 50mM lactic acid buffer: Weigh 5.0g of 90% lactic acid and dissolve it in 1L of water to make a 50mM lactic acid solution. Weigh 9.3g of 60% sodium lactate and dissolve it in 1L of water to make a 50mM sodium lactate solution. Take 500mL of sodium lactate solution and adjust the pH to 4.2 with lactic acid solution. Store at 4℃.

[0055] Preparation of HPDSP: 12 g of HPDSP was dissolved in 1 L of pH 4.2 lactic acid buffer.

[0056] Preparation of iodine working solution: 44 mg iodine and 20 g potassium iodide, dilute to 500 mL with pure water. Prepare before use.

[0057] Starter culture YO-MIX 883LYO 500DCU, source Danisco, DuPont Nutrition & Biosciences, Denmark.

[0058] Starch residue assessment method:

[0059] Use iodine solution to dye starch and make a standard curve. Calculate the HPDSP content based on the absorbance value. Prepare 0-12mg / mL HPDSP solution, take 1mL, and add 10mL iodine working solution. Use a quartz cuvette to measure the absorbance value at a wavelength of 660nm. The relationship between starch content (x) and absorbance value (y) is obtained: y=0.1741x-0.069. Therefore, the starch content in the sample can be obtained based on the absorbance value.

[0060] Example 1 Preparation of amylase solution

[0061] 1.1 Preparation of ASa amylase

[0062] Solution A (5U / mL): weigh 50 mg of amylase ASa, add 1 mL of water and mix well. Prepare 1 tube.

[0063] Solution B (1U / mL): Take 200uL of solution A, add 800uL of water and mix well. Prepare 1 tube.

[0064] Solution C (0.1U / mL): Take 100uL of solution B, add 900uL of water and mix well. Prepare 4 tubes, namely C1, C2, C3, and C4.

[0065] Solution D (0.01U / mL): Take 100uL of solution C4, add 900uL of water and mix well. Prepare 4 tubes, namely D1, D2, D3, and D4.

[0066] Solution E (0.001U / mL): Take 100uL of D4 solution, add 900uL of water and mix well. Prepare 3 tubes, namely E1, E2, and E3.

[0067] 1.2 Preparation of HEa amylase

[0068] Solution F (6U / mL): Take 100uL of the original solution, add 900uL of water and mix well. Prepare 1 tube.

[0069] G solution (0.1U / mL): Take 17uL of F solution and add 983uL of water and mix well. Prepare 1 tube

[0070] H solution (0.01U / mL): Take 100uL of G solution and add 900uL of water to mix.

[0071] K solution (0.001U / mL): Take 100uL H solution, add 900uL water and mix well. Prepare 4 tubes, namely K1, K2, K3, K4

[0072] L solution (0.0001U / mL): Take 100uL K4 solution, add 900uL water and mix well. Prepare 4 tubes, namely L1, L2, L3, L4

[0073] M solution (0.00001U / mL): Take 100uL L4 solution, add 900uL water and mix well. Prepare 4 tubes, namely M1, M2, M3

[0074] Example 2 Production method when yogurt is contaminated by amylase ASa

[0075] 1. Pretreatment: Take 2 or 11 kg of milk, heat it to 55°C, keep it warm in a water bath, and stir it with a rotor for 20 minutes at a stirring speed of 1000 rpm.

[0076] 2. Adding materials and keeping warm for the first time: After the milk temperature reaches 55°C, the weighed ingredients (1.5% hydroxypropyl distarch phosphate, 10% white sugar) are immediately added. In order to simulate the contamination of the additives, the amylase ASa solution prepared in Example 1 is added to obtain a mixture. The final concentration of the amylase ASa solution in the mixture after addition is 0.0001-50 mU / mL. The mixture is added slowly and kept warm at 55°C for 25 min until it is completely dissolved.

[0077] 3. Second heat preservation and fermentation: 90-95°C (200rpm), heating for 5min20s. Immediately cool to 44°C. Add YO-MIX 883LYO 500DCU fermentation agent (including thermophilic Streptococcus and bulgaricus 0.3% w / w). Ferment at 43°C for 5-6h.

[0078] 4. After fermentation, sterilize with the pilot plant sterilization equipment at 75℃ for 20s. Take out and store at 25℃.

[0079] Subsequent acidity and viscosity determinations were performed.

[0080] Viscosity test method: Use the ProRheo R180 rotational viscometer to measure the viscosity of yogurt, select rotor No. 2 and set the speed to 64rpm / s and the temperature to 25℃. Pour the evenly mixed yogurt sample into the sample cup, making sure that the liquid surface covers the rotor calibration line to avoid bubbles. After starting the equipment, record the viscosity value (in mPa·s) when the reading is stable. After the measurement is completed, clean the rotor and sample cup in time and make sure they are dry for next use.

[0081] Acidity detection method: GB 5413.34-2010 "National Food Safety Standard Determination of Acidity of Milk and Dairy Products".

[0082] The acidity and viscosity results are shown in Table 1 below.

[0083] Table 1 Acidity and viscosity of yogurt

[0084]

[0085] The acidity indicates that all yogurts have reached the fermentation degree. The viscosity greater than 0.5ηPas indicates that the yogurt maintains a high viscosity. When the yogurt is contaminated by amylase ASa during the production process, when the concentration of amylase ASa in the mixture of ingredients is ≤1mU / mL, under the conditions of the yogurt production method of this application, the starch content in the yogurt remains stable, and the yogurt can maintain a stable viscosity for more than 180 days at room temperature, without worrying about the deterioration of the yogurt quality.

[0086] Example 3 Production method when yogurt is contaminated by amylase HEa

[0087] 1. Pretreatment: Take 2 or 11 kg of milk, heat it to 55°C, keep it warm in a water bath, and stir it with a rotor while heating for 20 minutes at a stirring speed of 1000 rpm.

[0088] 2. Adding materials and keeping warm for the first time: After the temperature reaches 55°C, the weighed ingredients (1.5% hydroxypropyl distarch phosphate, 10% white sugar) are added to simulate the contamination of the additives. The amylase HEa solution prepared in Example 1 is added to obtain a mixture. The final concentration of the amylase HEa solution in the mixture after addition is 0.000001-60 mU / mL. Add slowly and keep warm at 50°C for 25 min until it is completely dissolved.

[0089] 3. Second heat preservation and fermentation: 90-95°C (200rpm), heating for 5min20s. Immediately cool to 44°C. Add bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus 0.3% w / w). Ferment at 43°C for 5-6h.

[0090] 4. After fermentation, sterilize with the pilot plant sterilization equipment at 75℃ for 20s. Take out and store at 25℃.

[0091] The acidity and viscosity of yogurt were measured according to the method of Example 2.

[0092] The acidity and viscosity results are shown in Table 2 below.

[0093] Table 2 Acidity and viscosity of yogurt

[0094]

[0095] The acidity indicates that all yogurts have reached the fermentation degree. The viscosity greater than 0.5ηPas indicates that the yogurt maintains a high viscosity. When the yogurt is contaminated by amylase HEa during the production process, when the concentration of amylase HEa in the mixture of ingredients is ≤0.001mU / mL, under the conditions of the yogurt production method of this application, the starch content in the yogurt remains stable, and the yogurt can maintain a stable viscosity for more than 180 days at room temperature, without worrying about the deterioration of the yogurt quality.

[0096] Example 4 Effects of different concentrations of amylase ASa and specific heating steps on their starch hydrolysis

[0097] 4.1 Heat first and then add amylase

[0098] Weigh 1.5g HPDSP and 8g white sugar, add purified water to a total mass of 100g. Keep at 50-55℃ for 25 minutes, then keep at 90-95℃ for 5min. Add 0.01mU amylase ASa. Use the "amylase residue evaluation method" to determine the HPDSP residue. After 15 days, the starch HPDSP residue is 60%.

[0099] Weigh 1.5g HPDSP and 8g white sugar, add purified water to a total mass of 100g. Keep at 50-55℃ for 25 minutes, then keep at 90-95℃ for 5min. Add 0.001mU amylase ASa. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days, the starch HPDSP residue is 100%.

[0100] Weigh 1.5g HPDSP and 8g white sugar, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes, then keep warm at 90-95℃ for 5min. Add 0.0001mU amylase ASa. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days, the starch HPDSP residue is 100%.

[0101] 4.2 Add amylase first and then heat

[0102] Weigh 1.5g HPDSP, 8g white sugar, 100mU amylase ASa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days of warming, the starch residue is 99%.

[0103] Weigh 1.5g HPDSP, 8g white sugar, 10mU amylase ASa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days of warming, the starch residue is 99%.

[0104] Weigh 1.5g HPDSP, 8g white sugar, 1mU amylase ASa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. Keep warm at 15 days and the starch residue is 100%.

[0105] In the process of optimizing the yogurt preparation process to maintain stable viscosity, this example explores the effects of two processes on viscosity when using ASa amylase: heating first and then adding amylase ASa and adding amylase ASa first and then heating. Heating first is to gelatinize starch ASa. At this time, amylase ASa has not been heated, and a lower content of amylase ASa will cause starch hydrolysis.

[0106] In the present application, the step of adding amylase ASa first and then heating can allow the amylase ASa to undergo certain treatment to avoid premature inactivation. Even if there is a high concentration of amylase ASa in the raw materials, this process can effectively stabilize the starch content in the yogurt, thereby maintaining stable viscosity.

[0107] Example 5 Effects of different concentrations of amylase HEa and specific heating steps on their starch hydrolysis

[0108] 5.1 Heat first and then add amylase

[0109] Weigh 1.5g HPDSP and 8g white sugar, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes, then keep warm at 90-95℃ for 5min. Add 0.0024mU amylase HEa. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days, the starch HPDSP residue is 10%.

[0110] Weigh 1.5g HPDSP and 8g white sugar, add purified water to a total mass of 100g. Keep at 50-55℃ for 25 minutes, then keep at 90-95℃ for 5min. Add 0.0012mU amylase HEa. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days, the starch HPDSP residue is 50%.

[0111] Weigh 1.5g HPDSP and 8g white sugar, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes, then keep warm at 90-95℃ for 5min. Add 0.00012mU amylase HEa. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue. After 15 days, the starch HPDSP residue is 100%.

[0112] 5.2 Add amylase first and then heat

[0113] Weigh 1.5g HPDSP, 8g white sugar, 100mU amylase HEa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue, and the starch residue after 15 days is 14%.

[0114] Weigh 1.5g HPDSP, 8g white sugar, 10mU amylase HEa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue, and the starch residue after 15 days is 23%.

[0115] Weigh 1.5g HPDSP, 8g white sugar, 1mU amylase HEa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue, and the starch residue after 15 days is 100%.

[0116] Weigh 1.5g HPDSP, 8g white sugar, 0.1mU amylase HEa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue, and the starch residue after 15 days is 100%.

[0117] Weigh 1.5g HPDSP, 8g white sugar, 0.01mU amylase HEa, add purified water to a total mass of 100g. Keep warm at 50-55℃ for 25 minutes. Then keep warm at 90-95℃ for 5 minutes. Use the "Amylase Residue Assessment Method" to determine the HPDSP residue, and the starch residue after 15 days is 100%.

[0118] In the process of optimizing the yogurt preparation process to maintain stable viscosity, this example explores the effects of two processes on viscosity when HEa amylase is used: heating first and then adding amylase HEa and adding amylase HEa first and then heating. Heating first is to gelatinize starch Hea. At this time, amylase HEa has not been heated, and a lower content of amylase HEa will cause starch hydrolysis.

[0119] In the present application, the step of adding amylase HEa first and then heating can allow the amylase HEa to undergo certain treatment to avoid premature inactivation. Even if there is a high concentration of amylase HEa in the raw materials, this process can effectively stabilize the starch content in the yogurt, thereby maintaining stable viscosity.

[0120] Example 6 Effect of Additives

[0121] This example uses ultra-high amylase content to optimize the additives.

[0122] 6.1 Raw material and auxiliary material number: (a) Sodium alginate 0.1g; (b) Pectin 0.1g; (c) Whey powder 1g; (d) Apple jam 10g; (e) White sugar 10g.

[0123] 6.2 Weigh 100g of commercially available fresh milk (14 bottles in total), preheat to 80℃, add raw materials a to e respectively, dissolve and cool to room temperature.

[0124] 6.3 Add 250 mg of ASa amylase and mix well.

[0125] 6.4 Preheat at 55℃ for 10min and heat according to the following conditions (n=2)

[0126] Since this embodiment uses an ultra-high amylase content, the insulation time is extended, ①95℃ / 30min, ②95℃ / 15min, ③85℃ / 30min, ④85℃ / 15min, ⑤75℃ / 30min, ⑥75℃ / 15min, ⑦no heating.

[0127] 6.5 Cool to 4℃ and balance. Put two tubes in each bottle. Centrifuge at 10000rpm for 15min. Take 10mL of supernatant from each tube and add 10mL of hydroxypropyl distarch phosphate (12mg / mL HPDSP, pH4.2).

[0128] 6.6 Preparation of 50mM lactic acid buffer: Weigh 5.0g of 90% lactic acid and dissolve it in 1L of water to prepare a 50mM lactic acid solution. Weigh 9.3g of 60% sodium lactate and dissolve it in 1L of water to prepare a 50mM sodium lactate solution. Take 500mL of sodium lactate solution and adjust the pH to 4.2 with lactic acid solution. Store at 4℃.

[0129] 6.7 Preparation of HPDSP: Dissolve 12 g of HPDSP in 1 L of pH 4.2 lactic acid buffer.

[0130] 6.8 Mix evenly at 55℃ for 25min, and sterilize at 95℃ for 5min.

[0131] 6.9 After cooling, store at 55℃ for 7 days and measure the starch content (A660).

[0132] The experimental results are shown in Table 3.

[0133] Table 3 Effect of additives on starch residue

[0134]

[0135] The results show that when the amylase content is high, 88% to 101% of the starch can be retained by using 95℃ for 30 minutes. Under the same heating condition of 95℃ for 15 minutes, the raw materials with the highest starch content are ranked as white sugar>apple jam>sodium alginate>pectin>whey powder. This shows that when white sugar is used, the highest starch residue can be guaranteed, and it is speculated that the stability of yogurt at room temperature can be maintained. Whey powder may have a protective effect on amylase due to its high protein content, which can reduce the damage of heating to amylase, so the degree of starch hydrolysis is relatively high.

[0136] Example 7 Expanding the Experimental Scale

[0137] The experimental system was expanded from a small volume (99 g + 1 mL enzyme solution) to industrial production conditions (such as 11 kg or ton-level reactions). The prepared yogurt could be stored at room temperature for more than 180 days with stable viscosity, verifying the scalability of the method.

[0138] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A method for producing yogurt that is resistant to amylase contamination, comprising pretreating milk, mixing the pretreated milk with hydroxypropyl distarch phosphate and an additive, subjecting the mixture to a first heat preservation and a second heat preservation, cooling and then fermenting to obtain the yogurt; the additive contains amylase; the first heat preservation temperature is 50-55°C, and the first heat preservation time is 25-30 minutes; the second heat preservation temperature is 90-95°C, and the second heat preservation time is 5 minutes to 5 minutes 20 seconds.

2. The yogurt production method according to claim 1, characterized in that: The addition amount of the hydroxypropyl distarch phosphate is 1.5-3.0wt%; And / or, the additive is added in an amount of 0.1 to 10 wt %.

3. The yogurt production method according to claim 1 or 2, characterized in that: The additive is selected from sodium alginate, pectin, whey powder, apple jam, and white sugar; Preferably, the additive is white sugar.

4. The yogurt production method according to claim 1, characterized in that: The second heat preservation also includes stirring, and the stirring speed is 200-300 rpm; And / or, the cooling is cooling to 40-44°C.

5. The yogurt production method according to claim 1, characterized in that: The fermentation includes adding a fermentation agent, wherein the fermentation agent includes thermophilic streptococcus and bulgaricus lactobacillus; Preferably, the addition amount of the leavening agent is 0.3-0.5wt%.

6. The yogurt production method according to claim 1 or 5, characterized in that: The fermentation time is 5 to 6 hours, and the fermentation temperature is 42 to 45°C.

7. The yogurt production method according to claim 1, characterized in that: The pretreatment is to heat to 55-58° C., maintain for 20-25 minutes, and stir at a speed of 1000-1200 rpm.

8. The yogurt production method according to claim 1, characterized in that: The method further comprises sterilizing the yogurt.

9. The yogurt production method according to claim 1, characterized in that: The amylase is selected from ASa or HEa; preferably, based on the volume of the mixture, the concentration of ASa is ≤1 mU / mL, and the concentration of HEa is ≤0.001 mU / mL.

10. A room temperature yogurt prepared by the yogurt production method according to any one of claims 1 to 9.

11. Use of the yogurt production method according to any one of claims 1 to 9 in yogurt production to tolerate amylase contamination.

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