Processing method of dried milk cake

Abstract

The invention relates to the technical field of bean product processing, in particular to a processing method of dried milk cakes. According to the specific technical scheme, in the fermentation stage of the dried milk cake, an auxiliary leavening agent is added, and the auxiliary leavening agent is any one of lactobacillus casei, lactobacillus rhamnosus, lactobacillus helveticus, lactobacillus delbrueckii subsp. Bulgaricus and lactobacillus plantarum. The antioxidant activity and the flavor of the Inner Mongolia dried milk cake are improved by using the auxiliary leavening agent.

Description

Technical Field

[0001] The present invention relates to the technical field of soy product processing, and particularly relates to a processing method of milk tofu. Background Art

[0002] Inner Mongolia milk tofu, also known as Hurood, is a well-known traditional dairy product in Inner Mongolia. This milk tofu not only tastes delicious but also is rich in protein, calcium and other important nutrients, bringing undeniable benefits to health. It is favored by consumers for its unique taste and rich nutritional value. However, with the increasing demand of consumers for healthy foods, the antioxidant capacity and flavor diversity of traditional milk tofu can no longer fully meet the market demand.

[0003] In the field of food science, antioxidant activity refers to the ability of certain specific components in foods to inhibit or slow down the oxidation process, which is of great significance for preventing diseases related to oxidative stress. Oxidative stress refers to cell damage caused by the excessive production of reactive oxygen species (ROS) and the imbalance of antioxidant defense mechanisms in living organisms. Therefore, improving the antioxidant activity of foods is crucial for enhancing their health benefits.

[0004] Flavor improvement involves the overall enhancement of the sensory quality of foods, including improving the aroma, taste and texture of foods, etc. In dairy products, the formation of flavor is a complex biochemical process involving the interaction of various microbial metabolites. Starter cultures, such as specific lactic acid strains, have been widely used in the fermentation process of dairy products to enhance the flavor and functionality of products.

[0005] Research shows that certain lactic acid strains can produce secondary metabolites with antioxidant properties, such as polyphenols, organic acids and vitamins, through their metabolic pathways. These metabolites can not only enhance the antioxidant activity of foods but also enrich the flavor profile of foods. Nevertheless, the research on the antioxidant activity and flavor improvement of Inner Mongolia milk tofu, a specific dairy product, is relatively scarce, and there is a lack of systematic methods to achieve this goal. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a processing method of milk tofu, which uses starter cultures to enhance the antioxidant activity and flavor improvement of Inner Mongolia milk tofu.

[0007] To achieve the above object, the present invention is realized through the following technical solutions:

[0008] The present invention discloses a processing method of milk tofu. During the fermentation stage of milk tofu, an auxiliary fermenting agent is added, and the auxiliary fermenting agent is any one of Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, and Lactobacillus plantarum.

[0009] Preferably, the addition amount of the auxiliary fermenting agent is 0.01% - 0.03%.

[0010] The present invention has the following beneficial effects:

[0011] During the natural fermentation process of Inner Mongolia milk tofu, the present invention significantly improves the sensory properties and antioxidant activity of milk tofu by adding different auxiliary fermenting agents. Description of the Drawings

[0012] Figure 1 is the determination result of the DPPH free radical scavenging ability of 16 milk tofu samples;

[0013] Figure 2 is the determination result of the ABTS free radical scavenging ability of 16 milk tofu samples;

[0014] Figure 3 is the determination result of the Fe 2+ scavenging ability of 16 milk tofu samples;

[0015] Figure 4 is the radar chart of the sensory properties of antioxidant milk tofu products; (A) Traditional milk tofu A and Lactobacillus casei Lc60 (B1, B2, and B3); (B) Traditional milk tofu A and Lactobacillus rhamnosus LRa66 (C1, C2, and C3); (C) Traditional milk tofu A and Lactobacillus helveticus Lh76 (D1, D2, and D3); (D) Traditional milk tofu A and Lactobacillus delbrueckii subsp. bulgaricus Lb42 (E1, E2, and E3); (E) Traditional milk tofu A and Lactobacillus plantarum Lp90 (F1, F2, and F3);

[0016] Figure 5 is the consumer characteristics of antioxidant milk tofu; (A) Age composition of consumers; (B) Male - female ratio of consumers; (C) Educational level of consumers; (D) Frequency of consuming milk tofu by consumers in the past three months;

[0017] Figure 6 is the analysis of variance of the 9 - point hedonic test of antioxidant milk tofu;

[0018] Figure 7 is the internal preference map analysis of antioxidant milk tofu samples; (A) Observations (axes F1 and F2: 74.86%); (B) Variables (axes F1 and F2: 74.86%);

[0019] Figure 8 It is the ideal point analysis of JAR data for antioxidant milk tofu;

[0020] Figure 9 It is the proportion of consumers with JAR scores;

[0021] Figure 10 It is the penalty analysis of antioxidant milk tofu samples. Specific implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] If not specifically specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0024] The present invention discloses a processing method for milk tofu. In the fermentation stage of milk tofu, an auxiliary fermenting agent is added, and the auxiliary fermenting agent is any one of Lactobacillus casei Lc60, Lactobacillus rhamnosus LRa66, Lactobacillus helveticus Lh76, Lactobacillus delbrueckii subsp. bulgaricus Lb42, and Lactobacillus plantarum Lp90. The addition amount of the auxiliary fermenting agent is 0.01% - 0.03%.

[0025] The natural fermentation production process of milk tofu is: raw milk → filtration, purification → separation → fermentation → heating → addition of whole milk → whey discharge → frying → cooling. On the basis of the natural fermentation production process of milk tofu, an auxiliary fermenting agent is added in the fermentation stage to participate in the fermentation process of milk tofu, and then the antioxidant activity of the prepared milk tofu is measured and the sensory evaluation is carried out.

[0026] The specific process of the natural fermentation production process is as follows: after the raw milk is filtered through a double filter, it is heated to 30-35°C for milk fat separation to obtain skim milk. The skim milk is fermented at 30-32°C for about 16 hours until the acidity is about 36°T and the pH is 5.4. The fermented milk is then heated and stirred to 42°C. The purpose of stirring is to release the whey in the curd and promote the formation of cheese. After forming, the cheese block has a certain elasticity and toughness, and is a cube with a length, width and height of about 2cm. The formed cheese block is further fried at 50-60°C to remove excess whey, add sugar to soften and form, and finally package and sterilize to make the finished milk tofu.

[0027] Among them, DPPH free radical scavenging ability, ABTS free radical scavenging ability and Fe 2+ The chelation capacity was used to determine the antioxidant activity of the new milk tofu product. The appearance, flavor and taste of the milk tofu were evaluated by a sensory panel.

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] The specific process of testing the antioxidant activity of milk tofu prepared in the following examples and the sensory evaluation is as follows:

[0030] 1. Extraction method of milk tofu water-soluble extract

[0031] Six times the weight of ultrapure water was added to the milk tofu sample for vortex mixing. The mixture was shaken in a water bath shaker at 40°C and 220rpm for 1 hour and centrifuged at 9000rpm for 20 minutes at 40°C. The supernatant was taken and its pH was adjusted to 4.6 with 1M hydrochloric acid to precipitate soluble casein. After the casein was precipitated, it was centrifuged at 9000rpm and 4°C for 20 minutes. The supernatant was filtered through a 0.45μm aqueous membrane filter, and the obtained water-soluble extract was divided into centrifuge tubes and placed in a vacuum freeze dryer for lyophilization for 48 hours to obtain the milk tofu water-soluble extract.

[0032] 2. DPPH free radical scavenging ability determination

[0033] The free radical scavenging activity was determined by 1,1-diphenyl-2-trinitrohydrazine (DPPH). 1 mL of DPPH solution (0.1 mM DPPH, dissolved in 95% ethanol) was mixed with 1 mL of different concentrations of milk tofu water-soluble extract, vortexed and incubated at room temperature in the dark for 30 min. 95% ethanol solution was used as a reference, and the absorbance of the incubated samples was measured at 517 nm. Three parallel experiments were set up for each group.

[0034] The DPPH free radical scavenging activity was calculated as follows:

[0035] DPPH radical scavenging ability (%) = [1 - (A1 - A2) / A3] × 100%;

[0036] Where: A1: Absorbance of the sample and DPPH; A2: Absorbance of the reaction between 95% ethanol and the sample; A3: Absorbance of the reaction between distilled water and the DPPH solution.

[0037] 3. Determination of ABTS radical scavenging ability

[0038] ABTS· + solution (7.0 mM) was added to an equal volume of potassium persulfate (2.45 mM) and incubated at room temperature in the dark for 12 - 16 h. Before use, the above ABTS· + solution was diluted with 95% ethanol to make its absorbance at 734 nm wavelength be 0.70 ± 0.02, obtaining the ABTS· + working solution. 500 μL of the sample and 500 μL of the diluted ABTS working solution were added respectively, reacted at room temperature for 10 min, 200 μL was taken and added to a 96-well plate, and the absorbance at 734 nm was measured. Three parallel experiments were set for each group.

[0039] The calculation of ABTS scavenging activity is as follows:

[0040] ABTS radical scavenging ability (%) = [1 - (A1 - A2) / A3] × 100%;

[0041] Where: A1: Absorbance of the sample; A2: Absorbance of the reaction between 95% ethanol and the sample; A3: Absorbance of the reaction between distilled water and the ABTS solution.

[0042] 4. Fe 2+ Chelating ability determination

[0043] 1 mL of water-soluble extracts of milk tofu with different concentrations was mixed with 50 μL of ferrous sulfate (2 mM) and 200 μL of ferrozine (phenanthroline, 5 mM) to activate the reaction. After incubation at room temperature for 10 min, the absorbance at 562 nm was measured. The A0 value was measured after mixing ultrapure water with other reagents. Ethylenediaminetetraacetic acid (EDTA) with the same concentration was used as a control. Three parallel experiments were set for each group.

[0044] Fe 2+ The calculation formula for Fe

[0045] Fe 2+ Chelating ability (%) = [(A0 - A1) / A0] × 100%

[0046] Where: A1: Absorbance of the sample; A0: Absorbance of the reaction between ultrapure water and the reagent.

[0047] 5. Descriptive Analysis (QDA)

[0048] The sensory evaluation panel was trained to help them become familiar with the experimental procedures of descriptive analysis and to train their ability to distinguish different attributes of the samples. The descriptive analysis training was divided into two stages.

[0049] In the first stage, by referring to the literature, vocabulary that could describe the appearance (milky white, yellow, glossiness), odor (yogurt flavor, buttery flavor, butter flavor, fruity flavor, floral flavor, nutty flavor, fermented flavor, grassy flavor, alcoholic flavor, musty flavor, earthy flavor, metallic flavor) and taste (sourness, bitterness, saltiness, sweetness, umami, and richness) of the samples was given respectively to establish a vocabulary list. The duration of this stage was 30 - 60 minutes each time, and it was carried out twice. After discussion among the panel members, the final descriptive vocabulary library (milky white, glossiness, sourness, sweetness, bitterness, saltiness, umami, richness, yogurt flavor, buttery flavor, butter flavor, fruity flavor, floral flavor, and fermented flavor) was determined.

[0050] In the second stage, reference samples were selected for intensity scoring (scoring on a 15 - cm linear scale), and the duration of this stage was 30 - 60 minutes each time, and it was carried out three times.

[0051] 6. Consumer Analysis: 120 consumers were recruited. The recruited consumers were interested in the test and volunteered to participate, and the frequency of consuming solid milk tofu in the past three months was greater than or equal to once a month.

[0052] Six kinds of milk tofu were cut into small pieces (1.5 cm × 1.5 cm × 1.5 cm), taken out from the refrigerator and placed at room temperature (25 °C) for 1 h, and then provided to consumers for testing.

[0053] A 9 - point hedonic scale (1 point / extremely dislike - 9 points / extremely like) was used to score the aroma, taste, and overall flavor of the six kinds of milk tofu to examine the differences in consumers' preference for milk tofu.

[0054] Consumer testing used a 5 - point just - right scale (JAR scale, 1 point / tooweak, 2 points / a little weak, 3 points / just right, 4 points / a little strong, 5 points / toostrong) to determine the optimal levels of 12 sensory attributes (milky white, glossiness, sourness, sweetness, bitterness, saltiness, umami, richness, yogurt flavor, buttery flavor, butter flavor, fruity flavor, floral flavor, and yeast flavor) of the milk tofu samples for consumers.

[0055] Example 1

[0056] The natural fermentation production process of milk tofu is as follows: raw milk → filtration, purification → separation → fermentation → temperature rise → addition of whole milk → whey discharge → frying → cooling. On the basis of the natural fermentation production process of milk tofu, during the fermentation stage, the auxiliary fermenting agent Lactobacillus casei Lc60 is added, and the addition amounts are 0.01%, 0.02% and 0.03%, which participate in the fermentation process of milk tofu.

[0057] Example 2

[0058] Same as Example 1, the difference is that: the auxiliary fermenting agent Lactobacillus rhamnosus LRa66 is added, and the addition amounts are 0.01%, 0.02% and 0.03%.

[0059] Example 3

[0060] Same as Example 1, the difference is that: the auxiliary fermenting agent Lactobacillus helveticus Lh76 is added, and the addition amounts are 0.01%, 0.02% and 0.03%.

[0061] Example 4

[0062] Same as Example 1, the difference is that: the auxiliary fermenting agent Lactobacillus delbrueckii subsp. bulgaricus Lb42 is added, and the addition amounts are 0.01%, 0.02% and 0.03%.

[0063] Example 5

[0064] Same as Example 1, the difference is that: the auxiliary fermenting agent Lactobacillus plantarum Lp90 (100 billion CFU / g) is added, and the addition amounts are 0.01%, 0.02% and 0.03%.

[0065] The DPPH free radical scavenging ability, ABTS free radical scavenging ability and Fe 2+ chelating ability of the milk tofu prepared in Examples 1 - 5 were calculated, and the results are shown in Figures 1 - 3 As shown, the results show that: B1 (0.01% Lactobacillus casei Lc60), C3 (0.03% Lactobacillus rhamnosus LRa66), D1 (0.01% Lactobacillus helveticus Lh76), E1 (0.01% Lactobacillus delbrueckii subsp. bulgaricus Lb42) and F2 (0.02% Lactobacillus plantarum Lp90) are the products with the best sensory properties and the highest antioxidant activity among the five auxiliary fermenting agents. These 5 new products and the traditional milk tofu A (provided by Muxiangyuan Dairy Food Co., Ltd., Xilinhaote City, Inner Mongolia) were subjected to consumer tests.

[0066] The appearance, flavor and taste of the milk tofu were evaluated by a sensory evaluation panel, and the preference for the milk tofu was analyzed through consumer tests. The composition and characteristics of the consumers are shown in Figure 5 As shown. The results are shown in Figures 6 - 10As shown, the results show that: B1 significantly improved the umami, saltiness, sweetness, richness and fruity aroma of milk tofu (p<0.05), and significantly reduced the fermented flavor; C3 significantly improved the sweetness, richness and yogurt flavor; D1 helped to increase the sweetness, umami, yogurt flavor, butter flavor, cream flavor and fruity aroma of milk tofu (p<0.05); E1 helped to increase the umami, richness and floral aroma, and significantly reduced the sourness and fermented flavor (p<0.05); F2 significantly improved the taste attributes of milk tofu, including increasing umami and sweetness, and reducing sourness, bitterness and fermented flavor (p<0.05). For the overall preference and flavor preference, the 5 kinds of milk tofu with added adjunct starters were all higher than the traditional milk tofu A. Among them, D1, E1 and F2 were the most popular, followed by C3 and B1, and D1 was closer to the ideal milk tofu product considered by consumers. The results of penalty analysis pointed out the further improvement analysis of some sensory attributes of milk tofu, such as sweetness, cream flavor, etc., laying a foundation for developing functional milk tofu products that meet consumer expectations.

[0067] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for processing milk tofu, characterized in that: During the fermentation stage of milk tofu, an auxiliary fermentation agent is added, wherein the auxiliary fermentation agent is any one of Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus helveticus, Lactobacillus delbrueckii subspecies bulgaricus and Lactobacillus plantarum.

2. The method for processing milk tofu according to claim 1, characterized in that: The addition amount of the auxiliary fermentation agent is 0.01% to 0.03%.

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