A probiotic yoghurt containing dioscorea oligosaccharide and a preparation method thereof

Abstract

The application discloses a kind of probiotic yoghurt containing dioscorea alata oligosaccharide and a preparation method thereof, and relates to the technical field of functional food.The probiotic yoghurt comprises the following components in parts by weight: 0.1-1.0 parts of dioscorea alata oligosaccharide, 100-200 parts of pure milk, 4-20 parts of icing sugar and 0.1-1.0 parts of starter.The preparation method comprises the following steps: mixing dioscorea alata oligosaccharide, pure milk and icing sugar, adding the starter, inoculating and fermenting, and aging to obtain the probiotic yoghurt.The probiotic yoghurt containing dioscorea alata oligosaccharide is a thick solid with milk yellow color, free of foreign matter and chemical additives such as preservatives, has unique flavor, pure milk flavor, moderate sour and sweet taste, and delicate texture.The addition of dioscorea alata oligosaccharide promotes the proliferation of lactic acid bacteria in the yoghurt, especially Lactobacillus bulgaricus, and after eating the yoghurt, the composition of intestinal probiotics can be adjusted to promote intestinal health.The probiotic yoghurt containing dioscorea alata oligosaccharide provides a new way for the development and utilization of dioscorea alata resources.

Description

Technical Field

[0001] This invention relates to the field of functional food technology, specifically to a probiotic yogurt containing soybean-yam oligosaccharides and its preparation method. Background Technology

[0002] Yogurt is generally defined as a dairy product fermented by inoculating *Lactobacillus bulgaricus* and *Streptococcus thermophilus*. Studies have shown that consuming yogurt can have beneficial effects on the human body, such as regulating the gastrointestinal microecological environment, maintaining intestinal flora balance, supplementing high-quality protein and calcium, and improving immunity. Based on the production process and characteristics of the final product, yogurt can be broadly divided into two types: stirred yogurt and set yogurt. Yogurt that is fermented directly in the final product packaging container without disrupting its curd state is called set yogurt. Set yogurt should have a firm, scoopable texture without a sticky or slippery feel. In various studies, yogurt is often used as a carrier of dietary fiber and other beneficial components.

[0003] Lactic acid bacteria are the core functional microorganisms involved in yogurt fermentation. They metabolize lactose in milk to produce lactic acid, causing milk proteins to coagulate and forming the unique flavor and texture of yogurt. They are also a type of probiotic beneficial to human gut health. Studies have found that adding plant polysaccharides to yogurt not only improves its texture but also promotes lactic acid bacteria fermentation, thus enhancing the yogurt's quality.

[0004] yam bean( Pachyrhyizus erosus Jicama (also known as white sweet potato, yam bean, etc.) is rich in starch, sugar, protein, vitamins, and minerals. It can be eaten directly or used as a health food or medicinal material. Fujian province has a warm and humid climate with abundant sunshine and favorable conditions, resulting in a very high yield of jicama, but it is not resistant to storage and is easily spoiled. Jicama polysaccharides are the main sugars in jicama tubers besides starch. Jicama oligosaccharides can be prepared by processing jicama polysaccharides using ultrasound-Fenton combined technology. Studies have shown that jicama oligosaccharides can effectively regulate intestinal flora. Therefore, this invention organically combines jicama oligosaccharides with yogurt fermentation technology to develop a new type of functional yogurt, which is of great significance for expanding the application value of jicama resources. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a probiotic yogurt containing soybean-jiuctooligosaccharides and a method for preparing the same. Specifically, it provides a yogurt that can promote the proliferation of lactic acid bacteria and a method for preparing the same. This probiotic yogurt can promote the proliferation of Lactobacillus bulgaricus and Streptococcus thermophilus, especially promoting the proliferation of Lactobacillus bulgaricus.

[0006] This invention provides a probiotic yogurt containing jicama oligosaccharides. By adding jicama oligosaccharides to yogurt, this invention not only develops a new flavor of yogurt—a creamy yellow, viscous solid free of impurities, preservatives, and other chemical additives—but also provides a unique flavor, pure milk taste, balanced sweetness and sourness, and a delicate texture. Furthermore, jicama oligosaccharides can promote the proliferation of lactic acid bacteria in yogurt, especially Lactobacillus bulgaricus. Compared with jicama polysaccharides or other prebiotics such as inulin, the jicama oligosaccharides of this invention have a significantly better effect on promoting lactic acid bacteria proliferation, helping to maintain the probiotic activity level of yogurt during storage. Their prebiotic properties can also further enhance the nutritional value and functional activity of the yogurt.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a probiotic yogurt containing jicama oligosaccharides, wherein the probiotic yogurt is fermented from raw materials including jicama oligosaccharides, a starter culture, and milk, wherein the jicama oligosaccharides can promote the proliferation of lactic acid bacteria in the starter culture. The starter culture includes Lactobacillus bulgaricus and Streptococcus thermophilus.

[0008] In some optional embodiments, the soybean-pickled oligosaccharide has a weight-average molecular weight of 2 kDa, a total sugar content of 70.9% ± 1.2%, a uronic acid content of 21.7% ± 1.0%, and a sugar chain composed of glucose, galacturonic acid, galactose, rhamnose, and arabinose.

[0009] In some optional embodiments, the mass fractions of each component in the raw materials are: 0.1-1.0 parts of soybean-piglet oligosaccharide, 100-200 parts of pure milk, and 0.1-1.0 parts of starter culture.

[0010] In some alternative embodiments, the starter culture is a commercially available yogurt starter culture composed of Lactobacillus bulgaricus and Streptococcus thermophilus.

[0011] In some alternative implementations, the number of viable Lactobacillus bulgaricus in the probiotic yogurt is increased by 60% to 70% compared to before fermentation.

[0012] In some alternative implementations, the viable count of Streptococcus thermophilus in the probiotic yogurt is increased by 15% to 25% compared to before fermentation.

[0013] In some alternative embodiments, the raw materials further include icing, wherein the icing is present in parts by weight of 4 to 20 parts.

[0014] Secondly, the present invention provides a method for preparing the aforementioned probiotic yogurt, comprising the following steps: Mix the jicama oligosaccharides, milk, and icing sugar to obtain a mixture; Add the starter culture to the mixture, mix well, and ferment. The fermented yogurt is then subjected to post-fermentation to obtain the probiotic yogurt.

[0015] The preparation method of the present invention has simple procedures, reasonable cost, and is suitable for large-scale production.

[0016] In some alternative embodiments, the fermentation conditions include: fermentation at a temperature of 36-45°C for 6-12 hours.

[0017] In some alternative embodiments, the fermentation conditions include: fermentation at 38-44°C for 7-11 hours.

[0018] In some alternative implementations, the fermentation conditions include: fermentation at 42°C for 8 hours.

[0019] In some optional embodiments, the post-ripening method includes: refrigerating the fermented yogurt at 2-8°C for 12-24 hours. Preferably, the fermented yogurt is refrigerated at 3-7°C for 14-20 hours; more preferably, the fermented yogurt is refrigerated at 4°C for 16 hours. This invention has at least one of the following beneficial effects: This invention has found that adding jicama oligosaccharides to the yogurt fermentation system resulted in yogurt with acidity, pH, and water-holding capacity all within a reasonable range. The addition of jicama oligosaccharides effectively promoted the proliferation of lactic acid bacteria, especially Lactobacillus bulgaricus, in the yogurt, helping to maintain the probiotic activity level during storage. Furthermore, its prebiotic properties further enhanced the nutritional value and functional activity of the yogurt. Attached Figure Description

[0020] Figure 1 The images shown are actual pictures of the yogurt used in the embodiments and comparative examples of this invention.

[0021] Figure 2 The number of viable Lactobacillus bulgaricus and Streptococcus thermophilus in the yogurt in the embodiments and comparative examples of the present invention.

[0022] Figure 3 The acidity and pH value of the yogurt in the embodiments and comparative examples of this invention.

[0023] Figure 4 This refers to the water-holding capacity of the yogurt in the embodiments and comparative examples of the present invention. Detailed Implementation

[0024] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0025] The soybean-based oligosaccharides used in the following examples were obtained by oxidative degradation of soybean-based polysaccharides using an ultrasonic-Fenton combined technique. For details, please refer to Example 1 of Chinese Patent CN 120399106 A. The weight-average molecular weight of the soybean-based oligosaccharides was 2 kDa, the total sugar content was 70.9% ± 1.2%, the uronic acid content was 21.7% ± 1.0%, and the sugar chains were composed of glucose, galacturonic acid, galactose, rhamnose, and arabinose.

[0026] The starter culture used in the following examples is Baizuan Classic Probiotic Type (2-strain type) Yogurt Starter Culture (Angel Yeast Co., Ltd.), which contains Lactobacillus bulgaricus and Streptococcus thermophilus.

[0027] Example 1 This embodiment provides a probiotic yogurt (DPEP-6P) containing jicama oligosaccharides. The yogurt fermentation ingredients include: 0.4 parts by weight of jicama oligosaccharides, 100 parts by weight of pure milk, 6 parts by weight of icing sugar, and 0.1 parts by weight of starter culture.

[0028] This embodiment also provides a method for preparing the above-mentioned yogurt, the specific steps of which are as follows: (1) Mix 0.4 parts by weight of soybean oligosaccharide, 100 parts by weight of pure milk and 6 parts by weight of icing sugar to obtain a mixture; (2) Add 0.1 parts by weight of yogurt starter to the mixture to inoculate Lactobacillus bulgaricus and Streptococcus thermophilus, and stir thoroughly. (3) Place the inoculated milk at 42℃ for fermentation for 8 hours; (4) Place the fermented yogurt at 4℃ for 16 h to ripen.

[0029] The resulting probiotic yogurt containing jicama oligosaccharides (DPEP-6P) is shown in the image below. Figure 1 As shown.

[0030] Comparative Example 1 This comparative example provides a yogurt (PEP-6P) containing diosgenin. The yogurt fermentation ingredients include: 0.4 parts by weight of diosgenin, 100 parts by weight of pure milk, 6 parts by weight of icing sugar, and 0.1 parts by weight of starter culture.

[0031] This comparative example also provides a method for preparing the above-mentioned yogurt, the specific steps of which are as follows: (1) Mix 0.4 parts by weight of diosgenin, 100 parts by weight of pure milk and 6 parts by weight of icing sugar; (2) Add 0.1 parts by weight of yogurt starter to inoculate Lactobacillus bulgaricus and Streptococcus thermophilus, and stir thoroughly; (3) Place the inoculated milk at 42℃ for fermentation for 8 hours; (4) Place the fermented yogurt at 4℃ for 16 h to ripen.

[0032] The resulting yogurt containing diosgenin (PEP-6P) is shown in the image below. Figure 1 As shown.

[0033] Comparative Example 2 This comparative example provides a control yogurt, whose fermentation ingredients include: 100 parts by weight of pure milk, 6 parts by weight of icing sugar, and 0.1 parts by weight of starter culture.

[0034] This comparative example also provides a method for preparing the above-mentioned yogurt, the specific steps of which are as follows: (1) Mix 100 parts by weight of pure milk and 6 parts by weight of icing sugar; (2) Add 0.1 parts by weight of yogurt starter to inoculate Lactobacillus bulgaricus and Streptococcus thermophilus, and stir thoroughly; (3) Place the inoculated milk at 42℃ for fermentation for 8 hours; (4) Place the fermented yogurt at 4℃ for 16 h to ripen.

[0035] The actual picture of the resulting control yogurt is as follows: Figure 1 As shown.

[0036] Comparative Example 3 This comparative example provides a yogurt containing inulin. The yogurt fermentation ingredients include: 0.4 parts by weight of inulin, 100 parts by weight of pure milk, 6 parts by weight of icing sugar, and 0.1 parts by weight of starter culture.

[0037] This comparative example also provides a method for preparing the above-mentioned yogurt, the specific steps of which are as follows: (1) Mix 0.4 parts inulin, 100 parts whole milk and 6 parts icing sugar; (2) Add 0.1 part of yogurt starter, inoculate with Lactobacillus bulgaricus and Streptococcus thermophilus, and mix thoroughly; (3) Place the inoculated milk at 42℃ for fermentation for 8 hours; (4) Place the fermented yogurt at 4℃ for 16 h to ripen.

[0038] The resulting inulin-containing yogurt is shown in the image below. Figure 1 As shown.

[0039] Example 2 The viable lactic acid bacteria counts were performed on the yogurts obtained in Example 1 and Comparative Examples 1-3.

[0040] The viable count of lactic acid bacteria in yogurt was determined according to GB4789.35-2023, "National Food Safety Standard - Microbiological Examination of Food - Lactic Acid Bacteria Examination". The specific method was as follows: Weigh 1 g of yogurt, add an equal mass of sterile physiological saline, shake well, and then serially dilute to 10⁻⁶. -5 0.1 mL of the diluted solution was added to sterile, cooled MRS and MC agar media, respectively, and incubated at 37 ± 1 °C for 72 ± 2 h. After incubation, the number of lactic acid bacteria colonies on the plates was visually observed and counted.

[0041] The results are shown in Table 1 and Figure 2 As shown. There were no significant differences in the number of Lactobacillus bulgaricus and Streptococcus thermophilus among the three comparative yogurt groups; compared with Comparative Example 2, the number of Lactobacillus bulgaricus in the probiotic yogurt containing soybean-jiuctooligosaccharides in Example 1 was significantly increased by 66% compared with the control yogurt. p The concentration of *Streptococcus thermophilus* in the prebiotic yogurt containing *Dioscorea bulbifera* oligosaccharides (<0.05) showed good probiotic activity. Furthermore, the *Streptococcus thermophilus* count in the prebiotic yogurt containing *Dioscorea bulbifera* oligosaccharides in Example 1 was 22% higher than in the control yogurt, indicating that adding *Dioscorea bulbifera* oligosaccharides to yogurt promotes the proliferation of *Lactobacillus bulgaricus* and *Streptococcus thermophilus*, especially *Lactobacillus bulgaricus*, which helps maintain the probiotic activity level of the yogurt during storage. In addition, compared with Comparative Example 1, the viable counts of *Lactobacillus bulgaricus* and *Streptococcus thermophilus* in the yogurt of Example 1 were significantly higher than in Comparative Example 3, indicating that compared with other prebiotics such as inulin, *Dioscorea bulbifera* oligosaccharides promote the proliferation of *Lactobacillus bulgaricus* and *Streptococcus thermophilus*.

[0042] Table 1. Viable Lactic Acid Bacteria Counts in Examples and Comparative Examples Example 3 The acidity and pH of the yogurts obtained in Example 1 and Comparative Examples 1-3 were measured.

[0043] Acidity is an important indicator for determining the fermentation endpoint and evaluating the quality of yogurt. Acidity was determined according to the method in GB 5009.239-2016, "National Food Safety Standard - Determination of Acidity in Food". 1 g of yogurt sample was mixed with 2 mL of distilled water, and 0.2 mL of phenolphthalein was added as an indicator. After mixing, titration was performed with a 0.01 mol / L sodium hydroxide standard solution. The endpoint was a faint red color that did not fade within 5 seconds. The titrated acidity was calculated by multiplying the volume of sodium hydroxide solution consumed by 10. pH was determined by mixing the yogurt sample and measuring it using a pH meter.

[0044] The results are as follows Figure 3 As shown, the acidity of all four groups of yogurts met the requirements of the national standard GB19302-2025, "National Food Safety Standard for Fermented Milk". There were no significant differences in acidity and pH among the three comparative yogurt groups; the pH of the probiotic yogurt containing soybean-jiuctooligosaccharides was lower than that of the control yogurt and the yogurt containing inulin, while the corresponding titratable acidity was significantly higher. p <0.05). The reason for this might be that jicama oligosaccharides, as a carbon source substrate for lactic acid bacteria fermentation, promote acid production metabolism, thereby lowering the pH and increasing acidity. Under the same fermentation time, probiotic yogurt containing jicama oligosaccharides ferments the fastest. In practical industrial applications, this could potentially shorten fermentation time and improve industrial efficiency.

[0045] Example 4 The water-holding capacity of the yogurts obtained in Example 1 and Comparative Examples 1-3 was measured.

[0046] The water-holding capacity of yogurt can indirectly reflect the density of the gel network and the texture of the yogurt. Water-holding capacity was determined by centrifugation. Yogurt samples were added to centrifuge tubes and centrifuged at 5000 rpm for 10 min, after which the supernatant was discarded. The mass of the centrifuge tube (W0), the mass of the yogurt and the total mass of the centrifuge tube before centrifugation (W1), and the mass of the yogurt and the total mass of the centrifuge tube after centrifugation (W2) were recorded. The water-holding capacity was calculated by the mass ratio of the yogurt before and after centrifugation.

[0047] (Formula 1) The results are as follows Figure 4 As shown, the water-holding capacity of the probiotic yogurt containing jicama oligosaccharides was not significantly different from that of the control yogurt, indicating that adding jicama oligosaccharides does not reduce the water-holding capacity of yogurt. In the evaluation of yogurt texture, the water-holding capacity index is qualified.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A probiotic yogurt containing jicama oligosaccharides, characterized in that, The probiotic yogurt is fermented from raw materials including jicama oligosaccharides, a starter culture, and milk, wherein the jicama oligosaccharides can promote the proliferation of lactic acid bacteria in the starter culture. The starter culture includes Lactobacillus bulgaricus and Streptococcus thermophilus.

2. The probiotic yogurt according to claim 1, characterized in that, The weight-average molecular weight of the soybean-yam oligosaccharide is 2 kDa, the total sugar content is 70.9 ± 1.2%, the uronic acid content is 21.7 ± 1.0%, and the sugar chain is composed of glucose, galacturonic acid, galactose, rhamnose, and arabinose.

3. The probiotic yogurt according to claim 1, characterized in that, The mass fractions of each component in the raw materials are: 0.1-1.0 parts of soybean-pickled oligosaccharide, 100-200 parts of pure milk, and 0.1-1.0 parts of starter culture. The starter culture is a commercially available yogurt starter culture.

4. The probiotic yogurt according to claim 1, characterized in that, Compared to before fermentation, the number of live Lactobacillus bulgaricus in the probiotic yogurt increased by 60% to 70%.

5. The probiotic yogurt according to claim 1, characterized in that, Compared to before fermentation, the number of viable Streptococcus thermophilus bacteria in the probiotic yogurt increased by 15% to 25%.

6. The probiotic yogurt according to claim 1, characterized in that, The raw materials also include icing, which is 4 to 20 parts by weight.

7. The method for preparing probiotic yogurt according to any one of claims 1 to 6, characterized in that, Includes the following steps: Mix the jicama oligosaccharides, milk, and icing sugar to obtain a mixture; Add the starter culture to the mixture, mix well, and ferment. The fermented yogurt is then subjected to post-fermentation to obtain the probiotic yogurt.

8. The preparation method according to claim 7, characterized in that, The fermentation conditions include: fermentation at 36~45℃ for 6~12 h.

9. The preparation method according to claim 7, characterized in that, The fermentation conditions include: fermentation at 38~44℃ for 7~11 h.

10. The preparation method according to claim 7, characterized in that, The post-ripening method includes: refrigerating the fermented yogurt at 2~8℃ for 12~24 h.

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