Fingered citron essential oil yoghurt and preparation method thereof

Abstract

The invention belongs to the technical field of yoghourt preparation, and particularly relates to fingered citron essential oil yoghourt and a preparation method thereof. The invention provides a preparation method of fingered citron essential oil yoghurt, which comprises the following steps: mixing fingered citron essential oil, cane sugar and fresh milk according to a formula ratio, sterilizing, homogenizing, cooling, and adding a leavening agent under an aseptic condition for fermentation to finally obtain the fingered citron essential oil yoghurt. The preparation method disclosed by the invention is simple and easy to operate, the raw material formula is simple, and texture characteristics and sensory characteristics of the yoghourt can be improved without adding additives. Meanwhile, the fingered citron essential oil yoghurt prepared by the preparation method disclosed by the invention can regulate the intestinal flora structure, increase the number of beneficial flora (especially abundance of bifidobacterium and lactobacillus) in the intestinal tract, regulate the intestinal flora metabolite, remarkably increase the content of short-chain fatty acid in the intestinal tract and improve the health of the intestinal tract.

Description

Technical Field

[0001] The present invention belongs to the technical field of yogurt preparation. More specifically, it relates to a bergamot essential oil yogurt and a preparation method thereof. Background Art

[0002] The gut microbiota is a huge and complex microecosystem. As an important "microbial organ" of the human body, the gut microbiota can communicate, antagonize, and cooperate with each other, maintaining a relatively balanced state, and affecting the regulation of many physiological functions of the host, such as immunity, nutrition, and metabolism. Once the balance is broken, it will cause the dysregulation of the gut microbiota homeostasis, and then induce various diseases such as obesity, metabolic syndrome, fatty liver, diabetes, and inflammatory bowel disease. The gut microbiota and its metabolites can not only regulate human health, but also play an important bridging role between diet and the host. Many dietary components will escape the digestion of host enzymes in the upper digestive tract, then reach the large intestine, be decomposed and utilized by the gut microbiota, thereby changing the composition of the gut microbial community, and at the same time producing amino acid metabolites such as short-chain fatty acids (SCFAs), indole and indole derivatives, etc., and lipid metabolites such as bile acids, phospholipids, etc. These metabolites play various physiological roles in the human body, such as regulating the host's immune system, affecting lipid metabolism, and participating in maintaining the normal function of the intestine, thus affecting the host gut health.

[0003] Bergamot is the dried fruit of Citrus medica L. var. sarcodactylis Swingle of the Rutaceae citrus genus. Its nature and flavor are pungent, bitter, sour, and warm, and it belongs to the liver, spleen, stomach, and lung meridians. Bergamot is clinically commonly used to treat symptoms such as liver and stomach qi stagnation, epigastric fullness, chest and hypochondrium pain, cough with profuse phlegm, anorexia and vomiting, etc., and has the effects of regulating the stomach and relieving pain, regulating qi and soothe the liver, and removing dampness and resolving phlegm. It is a kind of traditional Chinese medicine that is both edible and medicinal. Bergamot is mainly distributed in tropical and subtropical regions, and it is planted in Zhejiang, Guangdong, Guangxi, Sichuan, Chongqing, Yunnan and other places in China. Among them, Guangfo bergamot, as a variety of genuine medicinal materials protected and developed by Guangdong Province, has been included in the "Regulations on the Protection of Lingnan Chinese Medicinal Materials in Guangdong Province" and has certain economic value and broad prospects for development and utilization. Guangfo bergamot mainly contains various functional components such as flavonoids, essential oils, coumarins, polysaccharides, and limonoids.

[0004] With the improvement of consumers' health awareness, the demand for yogurt products is increasingly tending towards natural and healthy. The research and application of new fermented dairy products are becoming the forefront trend in the field of food technology. A number of studies in recent years have confirmed that plant-derived natural active substances can be used as functional ingredients in yogurt fortification, which can not only optimize its chemical composition, but also act as natural stabilizers and texture modifiers, effectively improving the gel properties, microstructure, color and texture characteristics of yogurt. For example, Chinese patent application CN103355407A provides a perilla essential oil yogurt and its preparation method. First, ferment for 3 - 6 hours, then add perilla essential oil and mix well, and continue to ferment. The prepared yogurt has a unique flavor and an extended shelf life, and has the dual effects of sour milk and perilla essential oil; Chinese patent application CN114365766A provides a prickly ash black yogurt and its preparation method. First, sterilize milk, granulated sugar and high fructose syrup at high temperature, and then add prickly ash essential oil to ferment. The prepared prickly ash black yogurt emits a prickly ash fragrance and has a unique flavor, and improves the health care function to a certain extent. However, whether the yogurt prepared by the above existing technologies can improve the intestinal flora structure and regulate the intestinal flora metabolites is unknown, and there is no research on adding bergamot essential oil to yogurt yet. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and deficiencies of the prior art and provide a preparation method of bergamot essential oil yogurt.

[0006] The purpose of the present invention is to provide a bergamot essential oil yogurt.

[0007] The above purpose of the present invention is achieved by the following technical solutions:

[0008] A preparation method of bergamot essential oil yogurt, comprising the following steps:

[0009] S1. Mix fresh milk, sucrose and bergamot essential oil to obtain material A;

[0010] S2. Homogenize, sterilize and cool the material A obtained in step S1 to obtain a fermentation substrate;

[0011] S3. Under sterile conditions, add a fermenting agent to the fermentation substrate obtained in step S2, ferment at 40 - 44 °C, and refrigerate and ripen after fermentation to obtain bergamot essential oil yogurt;

[0012] The bergamot essential oil yogurt is made from the following raw materials: 0.05 - 0.15 wt% of bergamot essential oil, 4 - 12 wt% of sucrose, 0.003 - 0.006 wt% of fermenting agent, and the balance is fresh milk.

[0013] The raw materials of the present invention are simple, and the preparation method is easy to operate. Without the need for additional additives, the texture characteristics of yogurt can be significantly improved. In addition, the inventors have found through research that by using the preparation method of the present invention, bergamot essential oil yogurt prepared by adding bergamot essential oil before fermentation can promote the growth of probiotics in yogurt. At the same time, the growth of probiotics can enhance the conversion of bergamot essential oil components, thereby better regulating the intestinal flora structure, increasing the number of beneficial flora, and improving intestinal health.

[0014] The bergamot essential oil yogurt prepared by the present invention can significantly increase the abundance of beneficial bacteria such as Bifidobacterium, Prevotella, Lactobacillus, and Bacteroides, and thus increase the content of short-chain fatty acids, the metabolites of intestinal flora, especially the content of acetic acid, propionic acid, butyric acid, and isovaleric acid.

[0015] Preferably, the bergamot essential oil yogurt is made from the following raw materials: 0.05-0.075 wt% of bergamot essential oil, 8-10 wt% of sucrose, 0.0045-0.006 wt% of starter culture, and the balance is fresh milk. Under this formula, the sensory and texture qualities of the prepared yogurt are better.

[0016] Preferably, the bergamot essential oil yogurt is made from the following raw materials: 0.053 wt% of bergamot essential oil, 9.2 wt% of sucrose, 0.0045 wt% of starter culture, and the balance is fresh milk. Under this formula, the sensory and texture qualities of the prepared yogurt are even better.

[0017] Preferably, the starter culture is selected from one or more of Bifidobacterium, Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus acidophilus.

[0018] Preferably, in step S2, the homogenization process is: homogenize at 4000-6000 r / min for 4-6 min.

[0019] Preferably, in step S2, the sterilization temperature is 90-100 °C. Preferably, the sterilization temperature is 95 °C.

[0020] Preferably, the sterilization time is 3-6 min. More preferably, the sterilization time is 5 min.

[0021] Preferably, in step S3, the fermentation time is 3-7 h.

[0022] Preferably, the preparation method of the bergamot essential oil includes the following steps:

[0023] (1). Take bergamot, dry and crush it to obtain bergamot powder;

[0024] (2) Take the bergamot powder obtained in step (1), use n-butane as the extractant, extract at 45-55°C, and the extraction pressure is 0.4-0.6 MPa to obtain a mixture of extractant and bergamot essential oil, and then perform post-treatment to obtain bergamot essential oil.

[0025] Preferably, the post-treatment is to heat the mixture of extractant and bergamot essential oil to 55-65°C to vaporize the extractant and separate it from the bergamot essential oil.

[0026] In the preparation method of the present invention, n-butane is compressed into a liquid at 0.4-0.6 MPa, flows through the extraction kettle at a flow rate of 55-65 L / h, extracts bergamot essential oil, and then flows into the analysis kettle, where it is depressurized and heated to 55-65°C. The extractant becomes a gas, separating the bergamot essential oil from the extractant. The extractant remaining in the bergamot essential oil is then evaporated by a water bath at 50-55°C, and the gaseous extractant is compressed back into a liquid and flows through the extraction kettle for cyclic extraction use.

[0027] Preferably, the extraction time is 50-70 min.

[0028] Preferably, the bergamot is Guangfo bergamot.

[0029] The present invention also protects the bergamot essential oil yogurt prepared by the above preparation method.

[0030] The present invention has the following beneficial effects:

[0031] The present invention provides a preparation method of bergamot essential oil yogurt, which mixes bergamot essential oil with sucrose and fresh milk according to the formula amount, sterilizes, homogenizes, cools, and adds a starter for fermentation under aseptic conditions to finally obtain bergamot essential oil yogurt. The preparation method of the present invention is simple and easy to operate, the raw material formula is simple, and no external additives are required, which can improve the texture characteristics and sensory characteristics of yogurt. At the same time, the bergamot essential oil yogurt prepared by the present invention can regulate the intestinal flora structure, increase the number of beneficial flora in the intestine (especially the abundance of Bifidobacterium and Lactobacillus), regulate the metabolites of intestinal flora, significantly increase the content of short-chain fatty acids in the intestine, and improve intestinal health. Description of the Drawings

[0032] Figure 1 It is a graph showing the effect of the addition amount of Guangfo bergamot essential oil on the water-holding capacity of yogurt.

[0033] Figure 2 It is a graph showing the effect of the addition amount of Guangfo bergamot essential oil on the viable bacteria of yogurt.

[0034] Figure 3 It is a graph showing the effect of the addition amount of Guangfo bergamot essential oil on the quality of yogurt.

[0035] Figure 4 It is the effect of the addition amount of sucrose on the quality of yogurt.

[0036] Figure 5 Effect of inoculum size of starter culture on the quality of yogurt

[0037] Figure 6 Effect of fermentation time on the quality of yogurt

[0038] Figure 7 Effect of fermentation temperature on the quality of yogurt

[0039] Figure 8 3D diagram of the interaction between the addition amount of essential oil from Fructus citri sarcodactylis and the addition amount of sucrose

[0040] Figure 9 3D diagram of the interaction between fermentation time and the addition amount of essential oil from Fructus citri sarcodactylis

[0041] Figure 10 3D diagram of the interaction between fermentation time and the addition amount of sucrose

[0042] Figure 11 Rheological property diagram of yogurt with essential oil from Fructus citri sarcodactylis. Among them, the left side is frequency sweep and the right side is shear sweep

[0043] Figure 12 Friction curve of yogurt with essential oil from Fructus citri sarcodactylis

[0044] Figure 13 Water-holding capacity of yogurt with different addition methods of essential oil from Fructus citri sarcodactylis. Among them, capital letters indicate the differences in different storage times of the same sample, and lowercase letters indicate the differences between samples at the same storage time

[0045] Figure 14 Change in the chemical components of the substance after the essential oil is fermented by yogurt

[0046] Figure 15 Change diagram of intestinal flora after in vitro fermentation of essential oil from Fructus citri sarcodactylis. Among them Figure 15 (a) in it is the analysis diagram of the alpha diversity index of intestinal flora Figure 15 (b) in it is the Venn diagram of the ASV / OTU distribution of intestinal flora Figure 15 (c) in it is the PCA analysis diagram of intestinal flora Figure 15 (d) in it is the PCaA diagram of intestinal flora Figure 15 (e) in it is the heat map of the species composition at the phylum level of intestinal flora Figure 15 (f) in it is the heat map of the species composition at the genus level of intestinal flora

[0047] Figure 16 Effect of yogurt with essential oil from Fructus citri sarcodactylis on short-chain fatty acids, the metabolites of intestinal flora Specific implementation method

[0048] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments. However, the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0049] Extraction of Guangfo Hand essential oil: The extraction of Guangfo Hand essential oil is carried out by low-temperature continuous phase change extraction and improved. Using n-butane as the extraction solvent, the fingered citron is dried (moisture content less than 13%) and crushed, then passed through a 30-mesh sieve. A certain amount of the fingered citron dry powder passed through the 30-mesh sieve is loaded into the extraction kettle. Using n-butane as the extractant, the extraction temperature is 50°C, the extraction time is 60 min, the extraction pressure is 0.6 MPa. After the extraction solvent enters the extraction device, it turns into a liquid under high pressure and flows into the extraction kettle at a flow rate of 60 L / h for 60 min of extraction. After the extraction is completed, the extractant dissolved with the fingered citron essential oil enters the analytical kettle. The analytical temperature is 60°C. By heating and reducing the pressure, the extractant changes from a liquid state to a gaseous state and rises to the condensation device. After condensation, it turns into a liquid state and is stored in the liquid storage tank. The extractant in the liquid storage tank can enter the extraction kettle again to realize cyclic extraction. The fingered citron essential oil is separated from the extractant in the analytical kettle and exists in the analytical kettle in a liquid state. The fingered citron essential oil is taken out from the bottom of the analytical kettle with a container, and the n-butane is evaporated in a 50°C water bath to obtain the Guangfo Hand essential oil (BEO). The sample is stored at -20°C for standby.

[0050] Fermenting agent: YF-L903 (Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus), Chr. Hansen (China) Co., Ltd.

[0051] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0052] Example 1 Process optimization of Guangfo Hand essential oil yogurt

[0053] Preparation of Guangfo Hand essential oil yogurt: Mix the Guangfo Hand essential oil, sucrose, and fresh milk according to the formula amount, homogenize at 5000 r / min for 5 min, sterilize at 95°C for 5 min, and quickly cool. After cooling to 42°C, add the fermenting agent according to the formula amount under sterile conditions, put it into a constant temperature incubator for fermentation, and after the fermentation is completed, put it into a 4°C refrigerator for cold storage and after-ripening for 12 h overnight.

[0054] The sensory scoring table of the yogurt is shown in Table 1 below.

[0055] Table 1 Sensory scoring table of fingered citron essential oil yogurt

[0056]

[0057]

[0058] 1. Single-factor experiment on the yogurt preparation process:

[0059] (1) Single-factor experiment on the addition amount of Guangfo hand essential oil:

[0060] Yogurt raw material formula (w%): Addition amount of Guangfo hand essential oil (0%, 0.05%, 0.075%, 0.1%, 0.125%, 0.15%), addition amount of sucrose 10%, inoculation amount of starter 0.005%, and the balance is fresh milk; Fermentation conditions: Fermentation at 42°C for 6 h.

[0061] Effect of the addition amount of Guangfo hand essential oil on the water-holding capacity of yogurt: Add 10 g of the Guangfo hand essential oil yogurt sample prepared according to the above formula to a 50 mL refrigerated centrifuge tube and seal it for storage. Take out the yogurt on specific days of storage, centrifuge it at 4°C (3000 r / min) for 10 min, then discard the supernatant, and weigh the total mass of the centrifuge tube and the remaining precipitate. The water-holding capacity of the Guangfo hand essential oil yogurt sample is calculated according to the following formula:

[0062]

[0063] In the formula: m is the mass of the empty centrifuge tube (g); m1 is the mass of the centrifuge tube containing the yogurt sample (g); m2 is the total mass of the centrifuge tube and the remaining precipitate after discarding the supernatant (g).

[0064] The experimental results are as Figure 1 shown. During the storage period of 1 - 21 d, with the extension of the storage days, the water-holding capacity of each group decreased significantly (P < 0.05). During the storage period, the water-holding capacity of the bergamot essential oil yogurt was higher than that of the yogurt without adding Guangfo hand essential oil (0% BEO) (P < 0.05), and showed a concentration effect. The higher the concentration of bergamot essential oil, the stronger the water-holding ability. On the 21st day of storage, the water-holding performance of the yogurt added with 0.05%, 0.1%, and 0.15% bergamot essential oil was 8.91%, 14.81%, and 17.17% higher than that of the ordinary yogurt respectively. The above results indicate that bergamot essential oil can improve the water-holding property of yogurt.

[0065] Effect of the addition of bergamot essential oil on the viable bacteria in yogurt: The determination of the viable bacteria count was carried out by referring to the methods for counting Lactobacillus and Streptococcus thermophilus in the national food safety standard (GB4789.35 - 2023) to detect the viable bacteria count of lactic acid bacteria in yogurt with different concentrations of bergamot essential oil, and each sample was measured in parallel three times.

[0066] The experimental results are as Figure 2 shown. The total viable bacteria count in yogurt increased with the extension of the fermentation time. At the 6th h of fermentation, the addition of 0.05% - 0.1% bergamot essential oil significantly promoted the growth of viable bacteria in yogurt (P < 0.05), and then the addition of 0.125% - 0.15% bergamot essential oil had no significant effect on the growth of probiotics in yogurt (P > 0.05). Therefore, a certain concentration of bergamot essential oil accelerated the growth of probiotics.

[0067] Effect of adding bergamot essential oil on the quality of yogurt: The experimental results are as Figure 3 shown. With the increase of the addition amount of bergamot essential oil, the hardness, adhesiveness, and chewiness of yogurt showed no significant change (P>0.05); however, the acidity of yogurt generally showed a trend of first increasing and then decreasing with the increase of the addition amount of essential oil, and reached the maximum when the addition amount of essential oil was 0.1%; the sensory score showed a downward trend with the increase of the essential oil concentration. According to the experimental results, the addition amount of bergamot essential oil was initially selected as 0.05 - 0.15%.

[0068] (2) Single - factor experiment on the addition amount of sucrose:

[0069] Yogurt raw material formula (w%): The addition amount of bergamot essential oil is 0.1%, the addition amounts of sucrose are (4%, 6%, 8%, 10%, 12%), the inoculation amount of the starter is 0.005%, and the balance is fresh milk; the fermentation conditions are: ferment at 42°C for 6 h.

[0070] The effect of the addition amount of sucrose on the quality of bergamot essential oil yogurt is as Figure 4 shown. With the increase of the addition amount of sucrose, the hardness, adhesiveness, and chewiness of yogurt generally showed a trend of first increasing and then decreasing; the acidity and sensory score generally showed an increasing trend with the increase of the addition amount of sucrose. The acidity reached the maximum when the addition amount of sucrose was 10%, and the sensory score reached the maximum when the addition amount of sucrose was 8%. According to the experimental results, the addition amount of sucrose was initially selected as 4 - 12%.

[0071] (3) Single - factor experiment on the inoculation amount of the starter:

[0072] Yogurt raw material formula (w%): The addition amount of bergamot essential oil is 0.1%, the addition amount of sucrose is 10%, the inoculation amounts of the starter are (0.0015%, 0.003%, 0.0045%, 0.006%, 0.0075%), and the balance is fresh milk; the fermentation conditions are: ferment at 42°C for 6 h.

[0073] The effect of the inoculation amount on the quality of bergamot essential oil yogurt is as Figure 5 shown. With the increase of the inoculation amount, the hardness, adhesiveness, and chewiness of yogurt showed no significant change (P>0.05); the acidity and sensory score generally showed an increasing trend with the increase of the inoculation amount. After 0.0045%, the acidity and sensory score showed no significant change (P>0.05), so 0.003 - 0.006% was selected as the inoculation dose.

[0074] (4) Single - factor experiment on the fermentation time:

[0075] Yogurt raw material formula (w%): The addition amount of Guangfo Fructus aurantii essential oil is 0.1%, the addition amount of sucrose is 10%, the inoculation amount of the starter is 0.0045%, and the balance is fresh milk; The fermentation conditions are: fermentation at 42°C for a fermentation time of (3h, 4h, 5h, 6h, 7h).

[0076] The experimental results are as Figure 6 shown. As the fermentation time increases, the hardness, adhesiveness, and chewiness of the yogurt generally show an increasing trend, and there is no significant difference after 6h of fermentation; The acidity and sensory score generally show an increasing trend as the fermentation time increases. The acidity and sensory score reach the maximum at 6h of fermentation, and after that, increasing the addition amount has no significant effect on them (P>0.05). According to the experimental results, the fermentation time is initially selected as 3 - 7h.

[0077] (5) Single - factor experiment on fermentation temperature:

[0078] Yogurt raw material formula (w%): The addition amount of Guangfo Fructus aurantii essential oil is 0.1%, the addition amount of sucrose is 10%, the inoculation amount of the starter is 0.0045%, and the balance is fresh milk; The fermentation conditions are: fermentation temperature (38°C, 40°C, 42°C, 44°C, 46°C), fermentation time 6h.

[0079] The influence of temperature on the quality of Guangfo Fructus aurantii essential oil yogurt is as Figure 7 shown. As the fermentation temperature increases, the hardness, adhesiveness, and chewiness of the yogurt generally show a trend of increasing first and then decreasing, and the hardness, adhesiveness, and chewiness are the largest at 42 and 44°C; The acidity and sensory score generally show a trend of increasing first and then decreasing as the essential oil temperature increases, and the acidity and sensory score reach the maximum at 42°C of fermentation temperature. According to the experimental results, 40 - 44°C is initially selected as the fermentation temperature.

[0080] 2. Response surface optimization of yogurt preparation process

[0081] Based on the results of the single - factor experiment, three factors, namely the addition amount of essential oil, the addition amount of sucrose, and the fermentation time, are selected. The fermentation temperature is fixed at 42°C and the inoculation amount of the starter is 0.0045%. Taking the comprehensive score (Y) of hardness, adhesiveness, chewiness, acidity, and sensory after weighting as the response value, a response surface optimization experiment is carried out. The experimental results are shown in Table 1 and Table 2.

[0082] Among them, the specific calculation of the comprehensive score (Y) is as follows: The weighting coefficients of yogurt hardness, adhesiveness, chewiness, acidity, and sensory score are all 20%. The intermediate values of each item and the calculation formula of the comprehensive score (Y) of each group are shown in formulas (1) and (2):

[0083]

[0084] Y * = w1y1'+ w2y2'+…+ wj y j '(2)

[0085] Where: y j ’ is the calculated intermediate value; y j refers to the measured value of each index in this group; y jmin is the minimum value of the same index among several groups; y jmax is the maximum value of the same index among several groups; Y* is the weighted comprehensive score of a certain group; w j is the weighted coefficient corresponding to each index.

[0086] Table 1 Box - Benhnken experimental design and results

[0087]

[0088]

[0089] Table 2 Significance analysis between factors and analysis of variance of regression equation

[0090]

[0091] Note: P < 0.05 indicates that the model or the investigated factor has a significant influence; P < 0.01 indicates that the model or the investigated factor has an extremely significant influence.

[0092] From the analysis results in Table 2, it can be seen that the order of the influence of each factor on the comprehensive score of bergamot essential oil yogurt is as follows: essential oil addition amount (A) > sucrose addition amount (B) > fermentation time (C). In this model, A, AB, C 2 are extremely significant factor terms (P < 0.01), AC is a significant factor term, while B, C, BC, A 2 , B 2 have no significant difference (P > 0.05), indicating that there is an interaction between the essential oil addition amount and the sucrose addition amount and the fermentation time, and there is no interaction between the sucrose addition amount and the fermentation time. According to Table 2, the regression model equation for the comprehensive score (Y) of bergamot essential oil yogurt is obtained:

[0093] Y = 0.5821 - 0.1212A - 0.0104B + 0.2750C - 0.0845AB + 0.0340AC + 0.0098BC + 0.0270A 2 - 0.0750B 2 - 0.1524C 2It can be seen from the analysis of variance table 2 of the regression model that the F value of the overall model of Guangfo hand essential oil yogurt is 8.11, P < 0.0001, and the model factors are significant. The lack-of-fit F value of this model is 3.50, P > 0.05, indicating no significant difference, which means the model can well predict the test results. Figures 8 - 9 It is a trend chart showing the influence of three factors, namely the essential oil addition amount, sucrose addition amount, and fermentation time value, on the comprehensive score of bergamot essential oil yogurt.

[0094] Table 3 Reliability analysis of the quadratic regression equation

[0095]

[0096] In Table 3, the correlation coefficient R of the comprehensive score model of Guangfo hand essential oil yogurt 2 = 0.9402, indicating that the model has a good linear fit and the test error is small; Adeq Precision = 74.4507, C.V = 2.84%, indicating that the model has a good signal-to-noise ratio and the test stability is relatively good. The model equation can be used to reflect the true test values.

[0097] Through the regression model of Design-Expert.V13 software, the optimal process conditions of Guangfo hand essential oil yogurt are systematically predicted as follows: the essential oil addition amount is 0.053%, the sucrose addition amount is 9.241%, and the fermentation time is 5.99 h. Under these conditions, the predicted comprehensive score of Guangfo hand essential oil yogurt can reach 0.77. According to the actual feasibility, the optimal process is adjusted to: the addition amount of Guangfo hand essential oil is 0.053%, the sucrose addition amount is 9.2%, and the fermentation time is 6 h. The comprehensive score is 0.78 ± 0.03, and no significant difference is found compared with the predicted theoretical value (p > 0.05). Within the allowable error range, it shows that the model is accurate and reliable and has a good fit.

[0098] Example 2

[0099] According to the optimal process conditions of Example 1, with the addition amount of Guangfo hand essential oil being 0.053%, the sucrose addition amount being 9.2%, the fermentation time being 6 h, the fermentation temperature being 42 °C, and the inoculation amount of the starter being 0.0045%, Guangfo hand essential oil yogurt is prepared. The specific preparation process is as follows:

[0100] Mix Guangfo hand essential oil, sucrose, and fresh milk, homogenize at 5000 r / min for 5 min, sterilize at 95 °C for 5 min, and quickly cool to 42 °C. Add the formulated amount of starter under sterile conditions, put it into a constant temperature incubator for fermentation, and after fermentation, put it into a 4 °C refrigerator for cold storage and after-ripening for 12 h overnight to obtain Guangfo hand essential oil yogurt (BEO-Y).

[0101] Among them, the yogurt formula (w%): 0.053% of Fructus citri sarcodactylis essential oil, 9.2% of sucrose, 0.0045% of starter, and 90.2655% of fresh milk.

[0102] Comparative Example 1

[0103] Prepare yogurt without Fructus citri sarcodactylis essential oil (blank yogurt). Compared with Example 2, the difference is that Fructus citri sarcodactylis essential oil is not added, and the rest of the preparation methods and conditions are the same as those in Example 2. Finally, blank yogurt B-Y is obtained.

[0104] Yogurt formula in Comparative Example 1 (w%): 9.2% of sucrose, 0.0045% of starter, and 90.7955% of fresh milk.

[0105] Comparative Example 2

[0106] Preparation of yogurt: Mix sucrose and fresh milk, homogenize at 5000 r / min for 5 min, sterilize at 95 °C for 5 min, quickly cool, cool to 42 °C, add the formulated amount of starter under aseptic conditions, put it into a constant temperature incubator for fermentation. After fermentation, add Fructus citri sarcodactylis essential oil, and put it into a 4 °C refrigerator for cold storage and after-ripening for 12 h overnight to obtain Fructus citri sarcodactylis essential oil yogurt (BEO-Y').

[0107] Among them, the yogurt formula (w%): 0.053% of Fructus citri sarcodactylis essential oil, 9.2% of sucrose, 0.0045% of starter, and 90.2655% of fresh milk.

[0108] The difference between Comparative Example 2 and Example 2 is that the addition order of Fructus citri sarcodactylis essential oil is different. In this comparative example, Fructus citri sarcodactylis essential oil is added after fermentation.

[0109] Comparative Example 3

[0110] Prepare yogurt with Fructus citri sarcodactylis essential oil added after sterilization (M + BEO). Compared with Example 2, the difference is that after mixing sucrose and fresh milk, homogenize for 5 min, sterilize at 95 °C for 5 min, then add 0.053% of Fructus citri sarcodactylis essential oil, and the rest of the preparation methods and conditions are the same as those in Example 2. Finally, yogurt with essential oil added after sterilization M + BEO is obtained.

[0111] Comparative Example 4

[0112] Prepare yogurt with Fructus citri sarcodactylis essential oil added during yogurt fermentation (3h + BEO). Compared with Example 2, the difference is that after inoculating the yogurt, add 0.053% of Fructus citri sarcodactylis essential oil after fermentation for 3 h, and the rest of the preparation methods and conditions are the same as those in Example 2. Finally, yogurt with essential oil added during fermentation 3h + BEO is obtained.

[0113] Texture, rheology, and oral friction measurement of Fructus citri sarcodactylis essential oil yogurt in Example 4

[0114] 1. Experimental materials: Guangfo Hand essential oil yogurt (BEO-Y) prepared in Example 2, blank yogurt (B-Y) prepared in Comparative Example 1, and commercially available yogurt (CY).

[0115] 2. Experimental methods:

[0116] Texture detection method: The texture parameters of the samples were measured using a TA.XTPlus texture analyzer. The TPA mode was used for testing, a cylindrical probe was selected, the test distance was 10 mm, the trigger point was 10.0 g, the pre-test speed was 6 mm / s, the in-test speed was 2 mm / s, and the post-test speed was 2 mm / s. The measurement indicators included: hardness in the first cycle, adhesiveness, and chewiness degree.

[0117] Rheological property detection method: A rheometer with a P20 / Ti-01170847 rotor and a gap of 0.05 mm was used. The yogurt was subjected to a shear sweep at 25 °C, and the shear frequency was 0.1 s -1 ~100 s -1 , and the time was 180 s. In the frequency sweep, the shear strain was 0.1%, and the sweep range was 0.1 - 60 Hz.

[0118] Oral friction detection method: The oral tribological properties of the yogurt samples were measured and analyzed using a rheometer. Open the built-in software “HAAKE RheoWin Job Manager” of the rheometer, confirm the probe TR 13 45°, select the “tribologymeasuring” program, set the shear rate range: 0 - 300 mm / s, temperature: 37 °C, zero the instrument, add the sample to 2 / 3 of the height of the accessory, click “continue” to start the measurement, the measurement time: 6 min, and each measurement was repeated three times.

[0119] Water-holding capacity detection method: Refer to the method described in Example 1.

[0120] Essential oil component change detection method: The essential oil yogurt was mixed with n-hexane at a ratio of 1:1, centrifuged at 12000 r / min for 5 min, the supernatant was taken and filtered through a 0.22 μm filter membrane, and then analyzed by gas chromatography-mass spectrometry (GC-MS).

[0121] The samples were analyzed by gas chromatography-mass spectrometry (GC-MS) using a TG-5MS weak polar capillary column (60 m × 0.25 mm × 0.5 μm), helium as the carrier gas, a column flow rate of 1.0 mL / min, an injection volume of 1.0 μL, and the following programmed temperature conditions: hold at 50 °C for 2 min, then increase the temperature at a rate of 8 °C / min to 150 °C and hold for 0 min, and then increase the temperature at a rate of 5 °C / min to 260 °C and hold for 10 min.

[0122] 3. Experimental results:

[0123] Texture: To compare the differences between Bergamot essential oil yogurt under the optimal conditions and commercially available yogurt, the results of the texture characteristics of the yogurt are shown in Table 4. Compared with the blank yogurt (B-Y), the bergamot essential oil added to the bergamot essential oil yogurt (BEO-Y) significantly increased the hardness and adhesiveness of the yogurt (P<0.05), but there was no significant difference in chewiness (P>0.05). Among them, the hardness and adhesiveness increased by 5.87% and 19.30% respectively. Thickeners and other additives will be added during the preparation of commercially available yogurt (CY) to improve the texture of the yogurt. The yogurt preparation process and raw materials of the present invention are simple, and the texture characteristics of the yogurt, such as hardness, adhesiveness, and chewiness, are not significantly different from those of commercially available yogurt without the need to add additional additives. These results indicate that bergamot essential oil can improve the texture characteristics of yogurt.

[0124] Table 4 Texture characteristics of different yogurts

[0125]

[0126] Rheological properties: The shear sweep and frequency sweep curves of bergamot essential oil yogurt are as follows Figure 11 shown. At low shear rates, compared with the blank yogurt (B-Y), the apparent viscosity of the bergamot essential oil yogurt increased significantly (P<0.05), and its apparent viscosity was higher than that of commercially available yogurt (P<0.05). This indicates that bergamot essential oil improves the rheological properties of yogurt and increases its apparent viscosity.

[0127] Oral tribology: The combined use of a rheometer and tribology is a new method for predicting the oral perception of food. To study the differences in smoothness between bergamot essential oil yogurt, commercially available yogurt, and blank yogurt, their differences were evaluated through oral friction. The results are as Figure 12 shown. The coefficient of friction value (F30) at a rate of 10 mm / s is an important parameter reflecting the friction scenario at a low chewing level, while the coefficient of friction value (F24) at a rate of 24 mm / s is a reflection of the oral friction sensation at a high chewing level. A shorter boundary state and lower coefficient of friction F10 or F24 values indicate a smoother and softer gel texture. Compared with ordinary yogurt, commercially available yogurt and bergamot essential oil yogurt showed lower F24, indicating that the smoothness of yogurt was improved after bergamot essential oil intervention. At the same time, the F24 of bergamot essential oil yogurt was the lowest (P<0.05), indicating that bergamot essential oil yogurt has a better smooth taste.

[0128] Water holding capacity: The water holding capacity of yogurt with bergamot essential oil added at different time points was measured. The results are as Figure 13As shown, the water-holding capacity of plain yogurt decreased significantly with the extension of storage time. On the 21st day of storage, the addition of Buddha's hand essential oil to yogurt at each time point improved the water-holding performance of yogurt. The group with the best water-holding capacity was the BEO-Y group, indicating that inoculating and fermenting after simultaneous sterilization of the essential oil and milk sucrose was better than other addition methods.

[0129] Changes in essential oil components: As Figure 14 shown, there were significant changes in the content of volatile substances in yogurt before and after fermentation. Compared with the BEO-Y group, 6 differential substances decreased in the BEO-Y' group, namely 3-pentanone, β-pinene, 4-Methyldecane, 2,6-dimethylundecane, 3,4-dimethylbenzaldehyde, and methyl palmitate; 4 metabolites increased, namely 2,3,4-trimethyl-n-hexane, 2,3-dimethyldecane, 2-methylundecane, and 2-methyl-1-hexadecanol. Among them, 4-Methyldecane is a hydrocarbon compound belonging to branched-chain alkanes; the contents of 3-pentanone and methyl palmitate were 0 after yogurt fermentation. During the fermentation of yogurt, the pH value decreased from about 6.5 to below 4.5. Under acidic conditions, 3-pentanone may be protonated or undergo a condensation reaction with other compounds (such as lactic acid), resulting in a decrease in its volatility or detection sensitivity. Similarly, under acidic conditions, it can catalyze the hydrolysis of ester compounds such as methyl palmitate. 2-Methyl-1-hexadecanol may indirectly affect the colonization of bacteria by changing the intestinal environment, such as through surface activity. The above results indicate that there are significant differences in the volatile components of yogurt prepared by adding Buddha's hand essential oil before fermentation and after fermentation.

[0130] Example 5 In vitro digestion of yogurt

[0131] Experimental materials: Buddha's hand essential oil yogurt (BEO-Y) prepared in Example 2, plain yogurt (B-Y) prepared in Comparative Example 1, and Buddha's hand essential oil yogurt (BEO-Y') prepared in Comparative Example 2.

[0132] Experimental method: Take B-Y, BEO-Y, and BEO-Y' yogurts and perform salivary digestion, gastric digestion, intestinal digestion in sequence, and finally use fecal bacteria for in vitro fermentation. The specific experimental methods are as follows:

[0133] S1. Sample solution preparation

[0134] Simulated saliva: α-amylase was dissolved in 1 mmol / L CaCl2 solution with an enzyme activity of 100 U / mL.

[0135] Simulated gastric juice: 250 mg of pepsin was dissolved in 10 mL of 0.1 mol / L HCl.

[0136] Simulated intestinal fluid: Dissolve 40 mg of trypsin and 250 mg of bile salts in 10 mL of 0.1 mol / L NaHCO3.

[0137] Preparation of intestinal flora inoculum:

[0138] S2. Preparation of in vitro fermented fecal bacteria solution

[0139] The fecal samples used in the experiment were collected from the fresh feces of 4 volunteers (aged 20 - 25 years, 2 males and 2 females, with normal diet, not taking antibiotics in the past 3 months and having no digestive tract diseases). After collecting the feces of the volunteers, they were immediately transported at low temperature and processed in a timely manner. In a laminar flow hood, the fresh fecal samples were mixed with sterile PBS solution at a ratio of 1:5 (w / v), vortexed for 2 min and then centrifuged at 4000 r / min for 10 min, and the supernatant was collected. In an anaerobic workstation, the collected supernatant was aliquoted into 5 mL cryotubes, mixed with sterile glycerol solution at a ratio of 1:1 (v:v), and stored in a -80 °C refrigerator for later use.

[0140] Preparation of growth medium:

[0141] Fully dissolve the components of the growth medium in Table 5 with deionized water and make up the volume to 1 L. Take 8 mL of the dissolved growth medium into an anaerobic tube and introduce CO2 for 10 min. After the ventilation is completed, sterilize at 121 °C for 20 min.

[0142] Table 5 Growth medium formula

[0143]

[0144]

[0145] Table 6 Macronutrient solution formula

[0146]

[0147] Note: a. Preparation of hemin solution: Accurately weigh 0.5 g of hemin and dissolve it in 1 mL of 1 M NaOH solution, then make up the volume to 100 mL with sterile water. b. Preparation of vitamin K solution: Accurately weigh 5 mg of vitamin K and dissolve it in 1 mL of 95% ethanol solution, then add the hemin solution and make up the volume to 100 mL, and store it in a brown bottle.

[0148] S3. Salivary digestion: Take 10 g of B-Y, BEO-Y, and BEO-Y' yogurts and place them in a 50 mL centrifuge tube. Add 10 mL of 0.9% sterile NaCl solution, and adjust the pH value of the digested samples in each experimental group to 6.0 (using 1 mol / L NaHCO3 solution). Finally, add 0.3 mL of simulated saliva to each experimental digested sample with a pH value of 6.0, and digest at 37 °C and 200 r / min for 1 min. End the reaction by cooling in an ice-water bath;

[0149] S4. Gastric digestion: Adjust the pH value of the samples after salivary digestion in each group to 2.0 with 1 mol / L HCl solution. Add simulated gastric juice to each experimental digested sample with a pH value of 2.0 at an addition ratio of 0.05 mL / g of digested sample, and digest at 37 °C and 200 r / min for 4 h respectively. End the reaction by cooling in an ice-water bath;

[0150] S5. Intestinal digestion: Adjust the pH value of the samples after salivary digestion and gastric digestion in each group to 6.0 (using 1 mol / L NaHCO3 solution). Then add simulated intestinal fluid to each experimental digested sample with a pH value of 6.0 at an addition ratio of 0.125 mL / g of digested sample, and digest at 37 °C and 200 r / min for 2 h respectively. End the reaction by cooling in an ice-water bath to terminate the reaction;

[0151] S6. In vitro fermentation: Under an anaerobic environment, dispense the growth medium and digested samples into anaerobic tubes (each anaerobic tube: 1.5 mL of fecal bacterial solution + 6.5 mL of growth medium + 2 mL of sample digest). After fermentation for 24 h, take samples. Immediately insert the sample tubes into ice after sampling, and centrifuge at 10000 r / min and 4 °C for 10 min. After centrifugation, take the supernatant as the fecal fermentation broth, and store it in a -80 °C refrigerator for later use, for high-throughput sequencing and determination of SCFAs content;

[0152] Perform high-throughput sequencing on the fecal fermentation broth prepared above: Take the supernatant of each group in a sterile centrifuge tube, take 5 parallel samples for each group, seal them with a sealing film to prevent cross-contamination between samples, and entrust Shanghai OE Biotech Co., Ltd. to perform 16S microbial diversity sequencing. After sequencing, use the OE Cloud platform independently developed by OE Biotech for independent online analysis to study the changes in the intestinal flora structure of the fecal fermentation broth after HTE treatment.

[0153] Determination of short-chain fatty acids: The contents of 6 SCFAs, namely acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid and isovaleric acid, were detected by GC-MS, and the differential SCFAs among groups were screened through data analysis. Extraction of short-chain fatty acids from fecal fermentation broth: The supernatant was obtained by centrifuging the fecal fermentation broth at 13000 r / min for 5 min. 500 μL of the supernatant was taken, 500 μL of methyl tert-butyl ether (MTBE) was added, vortexed and extracted for 30 min, centrifuged at 12000 r / min for 10 min, and the supernatant was transferred to a new 1.5 mL enzyme-free and sterile centrifuge tube, and filtered through a 0.22 μm organic filter membrane for on-machine detection.

[0154] GC-MS instrument parameters: Chromatographic column: TG-WAXMS capillary column (30 m × 0.25 mm × 0.25 μm); Temperature programming: Initial temperature 70 °C, then raised to 180 °C at 10 °C / min, held for 5 min, then raised to 220 °C at 15 °C / min, held for 5 min; Carrier gas: Nitrogen, flow rate 1 mL / min; Injection port temperature: 220 °C; Injection mode: Splitless, injection volume 1 μL; Detector temperature: 210 °C.

[0155] Standard solutions of 6 SCFAs (acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid and isovaleric acid) were prepared with methyl tert-butyl ether. Each SCFAs standard solution was diluted to SCFAs working solutions with gradient concentrations of 25, 50, 100, 200, 400, 800 μg / mL. After on-machine detection, a graph was plotted with peak area vs. concentration, and the sample concentration was calculated according to the standard curve.

[0156] Experimental results:

[0157] Alpha diversity, also known as within-sample diversity, can reflect information such as the richness and diversity of the microbial environment within a sample. As shown in Figure 15 Figure (a) below, compared with blank yogurt (B-Y), yogurt added with Fructus citri sarcodactylis essential oil before fermentation (BEO-Y) significantly increased the community abundance of intestinal flora (P < 0.05), but there was no significant difference between yogurt added with bergamot essential oil after fermentation (BEO-Y’) and blank yogurt (P > 0.05), indicating that yogurt added with bergamot essential oil before fermentation can better increase the abundance of intestinal flora.

[0158] As Figure 15As shown in Figure (b), a total of 101 ASVs were observed in the high-throughput sequencing of the intestinal microbiota. Of these, 8 ASVs were shared by the three groups, accounting for 7.41% of the total. The blank yogurt (BY) had 11 unique ASVs, accounting for 10.89% of the total. The yogurt with added bergamot essential oil before fermentation (BEO-Y) had 34 unique ASVs, accounting for 33.66% of the total. BEO-Y' had 13 unique ASVs, accounting for 12.87% of the total. These results indicate that the intestinal microbiota of the three yogurt groups shared common bacterial communities, while each group also had its own unique flora. BY had the fewest unique ASVs, while BEO-Y had the most. Furthermore, the number of unique ASVs in the yogurt with added bergamot essential oil before fermentation was higher than that in the yogurt with added bergamot essential oil after fermentation, indicating that adding bergamot essential oil to yogurt before fermentation contributes to the formation of a characteristic intestinal microbiota.

[0159] PCA reduces the dimensionality of complex data based on the species abundance matrix to generate principal component variables of sample data, reflecting the similarity and difference between samples according to the distance of the samples. Figure 15 As shown in Figure (c), the BEO-Y group is significantly different from the BY group. The BEO-Y group is further to the right in the PC1 direction, and the BEO-Y' group and the BY group are close in the PC1 and PC2 directions, indicating that the difference is not obvious. PCoA is an analysis method based on the sample distance matrix algorithm. It can reflect the species differences between communities based on the similarity or difference of the data. The result is shown in Figure 3. Figure 15 Figure (d) shows that adding bergamot essential oil before fermentation is well separated from the BY group and the yogurt added after fermentation, and the yogurt added after fermentation is closer to the BY group. These results indicate that adding bergamot essential oil before fermentation can better change the bacterial flora structure of the intestinal flora.

[0160] Heat maps were further used to perform species composition analysis, further compare species composition differences among samples, and display the species abundance distribution trends of each sample. Figure 15Figures (e) and (f) show the results of the heatmap analysis of the species composition of the gut microbiota at the phylum and genus levels. It can be seen from the figure that there are significant differences in the species composition of the gut microbiota at the phylum and genus levels between the pre-fermentation addition group and the blank group and the post-fermentation addition group. At the phylum level, the compositions of four microbiota, Proteobacteria, Desulfobacterota, Deferribacterota, and Fusobacteriota, are similar in the three groups. The abundances of Firmicutes, Actinobacteriota, and Bacteroidota in the pre-fermentation addition group are significantly higher than those in the other two groups. At the genus level, the abundances of Bifidobacterium and Prevotella in the BEO-Y and BEO-Y’ groups are significantly higher than those in the B-Y group (P<0.05), and the content in the BEO-Y group is the highest. Prevotella is associated with positive health outcomes, promoting the fermentation of dietary fiber and the production of short-chain fatty acids, which are related to improved metabolic health and reduced risk of certain diseases, such as inflammatory bowel disease. The beneficial bacteria, Lactobacillus and Bacteroides, have the highest abundances in the BEO-Y group (P<0.05). Compared with the BEO-Y’ group, the abundances of Muribaculaceae and Collinsella are the highest in the BEO-Y group. Muribaculaceae can produce short-chain fatty acids and regulate intestinal barrier function and immune responses, and is considered a promising "next-generation probiotic". The gut microbiota has limited metabolic capacity for long-chain alkanes, but some microbiota (such as the Clostridium genus) may decompose alkanes through β-oxidation to generate short-chain fatty acids (SCFAs). Specifically, Collinsella can promote the production of butyric acid, which has beneficial effects on intestinal health. The content in the pre-fermentation addition group is higher than that in the blank group, and the abundance of Lactobacillus in the pre-fermentation addition group is significantly higher than that in the post-fermentation addition group (P<0.05). In summary, the yogurt added with Buddha's hand essential oil before fermentation can regulate the species of gut microbiota, increase the abundance of gut microbiota, and promote the growth of beneficial bacteria in the intestine.

[0161] The effects of yogurt made with Buddha's hand essential oil added before and after fermentation on the short-chain fatty acids, which are intestinal metabolites, were studied through in vitro gastrointestinal fermentation simulation. The results are as Figure 16The results showed that compared with the blank group of yogurt (B-Y), yogurt added with essential oil of Citrus medica var. sarcodactylis before fermentation (BEO-Y) could significantly increase the contents of acetic acid, propionic acid, butyric acid, isobutyric acid and total acid (P<0.05); compared with yogurt added with essential oil after fermentation (BEO-Y’), yogurt added with essential oil before fermentation (BEO-Y) significantly increased the contents of acetic acid, propionic acid, butyric acid and isovaleric acid (P<0.05), but the content of valeric acid was lower, with no significant difference from B-Y (P<0.05). Bifidobacterium, Lactobacillus and Providencia are the main acetic acid-producing microorganisms, which can regulate the pH in the intestine and control people's appetite by producing acetic acid. The results of intestinal flora abundance showed that the number of Bifidobacterium increased, which might be one of the reasons for the increase in acetic acid content.

[0162] The above results indicate that yogurt added with essential oil of fingered citron before fermentation can better regulate the metabolites of intestinal flora and maintain human intestinal health.

[0163] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing bergamot essential oil yogurt, characterized in that, It includes the following steps: S1. Mix fresh milk, sucrose, and bergamot essential oil to obtain material A; S2. Homogenize, sterilize, and cool the material A obtained in step S1 to obtain a fermentation substrate; S3. Under sterile conditions, add a starter to the fermentation substrate obtained in step S2, ferment at 40 - 44 °C, and refrigerate and ripen after fermentation to obtain bergamot essential oil yogurt; The bergamot essential oil yogurt is made from the following raw materials: bergamot essential oil 0.05 - 0.15 wt%, sucrose 4 - 12 wt%, starter 0.003 - 0.006 wt%, and the balance is fresh milk.

2. The preparation method according to claim 1, wherein The bergamot essential oil yogurt is made from the following raw materials: bergamot essential oil 0.05 - 0.075 wt%, sucrose 8 - 10 wt%, starter 0.0045 - 0.006 wt%, and the balance is fresh milk.

3. The preparation method according to claim 2, wherein, The bergamot essential oil yogurt is made from the following raw materials: bergamot essential oil 0.053 wt%, sucrose 9.2 wt%, starter 0.0045 wt%, and the balance is fresh milk.

4. The preparation method according to claim 1, wherein The starter is selected from one or more of Bifidobacterium, Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus acidophilus.

5. The preparation method according to claim 1, wherein In step S2, the sterilization temperature is 90 - 100 °C.

6. The preparation method according to claim 1, characterized in that, The preparation method of the bergamot essential oil includes the following steps: (1). Take bergamot, dry and crush it to obtain bergamot powder; (2). Take the bergamot powder obtained in step (1), use n-butane as the extractant, extract at 45 - 55 °C, and the extraction pressure is 0.4 - 0.6 MPa to obtain a mixture of extractant and bergamot essential oil, and perform post-treatment to obtain bergamot essential oil.

7. The preparation method according to claim 6, characterized in that, The post-treatment is to heat the mixture of extractant and bergamot essential oil to 55 - 65 °C to vaporize the extractant and separate it from the bergamot essential oil.

8. According to the preparation method described in claim 1, characterized in that, In step S3, the fermentation time is 3 - 7 h.

9. According to the preparation method described in claim 1, characterized in that, The homogenization process is: homogenize at 4000 - 6000 r / min for 4 - 6 min.

10. Bergamot essential oil yogurt prepared by the preparation method according to any one of claims 1 - 9.

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