A method for preparing color and flavor enhanced whole-ingredient juice by synergistic fermentation of lactic acid bacteria

Abstract

This invention discloses a method for enhancing the color and aroma of whole-component fruit juice through synergistic fermentation with lactic acid bacteria, belonging to the field of food processing technology. The method uses ripe mangoes / pineapples as raw materials. After washing, pitting (peeling), and low-temperature jet milling to retain all components, the juice undergoes compound enzymatic hydrolysis and optimization of its uniformity. A compound strain composed of *Lactobacillus plantarum*, *Lactobacillus fermentum*, and *Lactobacillus helveticus* is then inoculated. The mixture undergoes constant-temperature anaerobic fermentation. The process is optimized using fuzzy mathematical sensory evaluation and response surface methodology, resulting in a sensory score of 91.67 for mango juice and 90.83 for pineapple juice. The retention rate of carotenoids is increased by 25%-30%, the lactic acid content reaches 2.97-26.45 mg / g, and the relative content of esters in volatile aroma components increases to over 35%. Simultaneously, the total sugar content decreases by 3.7%-24.0%. This method solves the problems of dull color, weak aroma, and nutrient loss in traditional whole-component fruit juices. The product combines natural functionality with a unique fermented flavor, making it suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to fruit juice fermentation preparation process, and more particularly to a preparation method that utilizes lactic acid bacteria to co-ferment whole-component fruit juice to achieve color enhancement and aroma enhancement. Background Technology

[0002] Mangoes and pineapples are tropical fruits rich in nutrients such as carotenoids, vitamin C, dietary fiber, and polyphenols. Carotenoids (such as beta-carotene and lutein) are natural pigments that give fruits their vibrant colors and also have antioxidant and vision-protecting functions. Bromelain in pineapples and mangiferin in mangoes also have physiological activities such as promoting digestion and anti-inflammation, making them high-quality raw materials for functional juices.

[0003] Current fruit juice processing often employs a "peeling and pitting-juicing-filtration" process, removing components rich in dietary fiber and pigment precursors, such as peels and pomace, resulting in nutrient loss and poor product color stability. While some whole-component fruit juices retain pomace, their dense cell wall structure easily leads to a dull color and poor stability. Furthermore, natural aroma components (such as esters and terpenes) are prone to volatilization during processing, requiring the addition of exogenous pigments, colloids, and flavorings to improve quality, which does not meet consumers' demand for "natural and healthy" products.

[0004] Lactic acid bacteria fermentation is an effective means to improve the quality of fruit juice. Existing technologies mostly use a single lactic acid bacteria (such as *Lactobacillus plantarum*) to ferment and clarify fruit juice. While this can reduce sugar content and produce organic acids, its effect on improving the color and aroma of the entire fruit juice is limited. On the one hand, a single strain is difficult to efficiently degrade cellulose and pectin in the peel, and cannot fully release bound carotenoids. On the other hand, the metabolic products of a single strain are limited, making it difficult to generate abundant volatile aroma substances (such as ethyl acetate and phenylethanol). Furthermore, traditional fermentation often leads to the oxidative degradation of carotenoids due to oxygen exposure, further affecting the color of the fruit juice. CN 111117926 B discloses *Lactobacillus plantarum* HU–C2W fermentation of lychee juice to increase GABA content, but does not involve compound strains or the utilization of all components. CN 115851520 B involves the co-fermentation of *Lactobacillus paracasei* and *Lactobacillus plantarum*, but mainly targets the generation of conjugated linoleic acid, without addressing the systematic improvement of color and aroma.

[0005] Therefore, developing a preparation method that can retain the full nutritional components and enhance color and aroma through the synergistic effect of lactic acid bacteria is of great significance for solving the quality defects of existing whole-component fruit juices and promoting the industrialization of natural fermented fruit juices.

[0006] Technical solution To address the problems in existing fruit juice processing, such as dull color (insufficient release of carotenoids), weak aroma (loss of volatile components), low nutrient retention, poor compatibility of traditional lactic acid bacteria fermentation strains, and lack of a scientific evaluation system for process optimization, this invention provides a color-enhancing and aroma-enhancing preparation method based on the synergistic fermentation of specific lactic acid bacteria. Through low-temperature pulping to retain all components, compound enzymatic hydrolysis to optimize the matrix, synergistic fermentation of specific strains, and fuzzy mathematics-response surface methodology, a synergistic enhancement of color, aroma, and nutrition is achieved.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: In one aspect, the present invention provides a method for preparing a color-enhancing and flavor-enhancing fruit juice by co-fermentation with lactic acid bacteria, comprising the following steps: S1. Raw material pretreatment: Mango pulp or pineapple pulp is pulped at low temperature to obtain a whole-component crude fruit pulp with a particle size ≤100 μm; S2. Compound enzymatic hydrolysis: Add 0.15%~0.2% of the mass of the compound enzyme to the crude fruit pulp obtained in step S1, and enzymatically hydrolyze at 45~50℃ for 60~90 min. After enzymatic hydrolysis, inactivate the enzyme and quickly cool to 35~37℃. The compound enzyme is a combination of pectinase and cellulase. Preferably, the mass ratio of pectinase to cellulase is 2:1.

[0008] S3. Blending: Add flavoring agents to the whole component crude fruit pulp after enzymatic hydrolysis for blending; S4. Homogenization by jet mill: The prepared coarse fruit pulp is processed in a micro jet homogenizer at a pressure of 80-160 MPa to obtain a full-component fruit juice sample. S5. Sterilization: The whole-component juice obtained in step S4 is subjected to UHT sterilization and pasteurization.

[0009] S6. Strain activation: Inoculate *Lactobacillus plantarum*, *Lactobacillus fermentum*, and *Lactobacillus helveticus* into MRS liquid medium containing 0.8%–1% of their respective fruit juice extracts, and incubate at 37°C for 16–20 h until the viable count is ≥1×10⁻⁶. 9 CFU / mL; Mix the three activated bacterial solutions in a mass ratio of (0.01~2):(0.01~1.5):(0.01~1) to obtain a compound lactic acid bacteria starter; S7. Co-fermentation: Add 3%-5% (v / w) of compound lactic acid bacteria starter to the sterilized whole-component juice in step S5, place it in an anaerobic environment with an oxygen content ≤0.5%, and anaerobic constant temperature fermentation at 35-37℃ for 12-36 h; measure the pH value every 6 h during the fermentation process, and control the final pH to 3.4~3.8; after fermentation, refrigerate at 4℃ for 12 h for post-ripening to obtain the color-enhanced and aroma-enhanced whole-component fermented juice.

[0010] In one embodiment, before the raw material pretreatment in step S1, the mangoes / pineapples need to be screened to remove diseased, rotten, and mechanically damaged fruits to ensure uniform maturity of the raw materials; before low-temperature pulping, the raw materials are pre-cooled for 30 minutes to avoid the oxidation of carotenoids caused by the temperature rise during pulping.

[0011] In one embodiment, the compound enzyme is added in a gradient manner in step S2. First, 50% of the compound enzyme is added and stirred for 10 min, then the remaining 50% is added to continue enzymatic hydrolysis, ensuring uniform hydrolysis. The mass ratio of pectinase to cellulase in the compound enzyme is 2:1, with pectinase activity ≥40000 U / g and cellulase activity ≥20000 U / g. Enzymatic hydrolysis is carried out at 45-50℃ for 60-90 min, with continuous stirring at 50-80 r / min during the process. Subsequently, the enzyme is inactivated at 90-95℃ for 5-8 min, and then rapidly cooled to 35-37℃. The enzyme inactivation is carried out using a segmented heating method: first, the temperature is raised to 80℃ and held for 2 min, then raised to 90-95℃ and held for 3-6 min to reduce nutrient loss.

[0012] In one embodiment, the flavoring agent in step S3 includes one or more of fructose syrup, white sugar, citric acid, and ascorbic acid. Preferably, 2%-6% fructose syrup, 3%-7% white sugar, 0.06%-0.10% citric acid, and 0.06%-0.10% ascorbic acid are added as flavoring agents by weight of the fruit pulp.

[0013] In one embodiment, in step S5, UHT sterilization is performed at 137°C for 5 seconds, and pasteurization is performed at 85°C for 30 minutes.

[0014] In one embodiment, the method for preparing the fruit juice extract in step S6 is as follows: take the whole component fruit juice of the corresponding raw material, sterilize at 95°C for 10 min, cool and centrifuge (4000 r / min, 10 min) to obtain the supernatant, and vacuum concentrate it to 1 / 5 of the original volume, which is the fruit juice extract for MRS culture medium.

[0015] In one embodiment, the anaerobic environment in step S7 is achieved by an anaerobic incubator, in which nitrogen is introduced to replace the air and the oxygen content is controlled to be ≤0.5%; the fermentation container is made of light-proof material to avoid light-induced degradation of carotenoids; during the cold-cold ripening process, the mixture is gently stirred once every 4 hours to promote the uniform distribution of flavor substances.

[0016] In one embodiment, the optimal fermentation process parameters for mango juice in step S7 are: fermentation time 30 h, fermentation temperature 36℃, and inoculum size 3%; the optimal fermentation process parameters for pineapple juice are: fermentation time 12 h, fermentation temperature 36℃, and inoculum size 3%. These parameters are optimized using response surface methodology, with sensory scores as the response values, and the regression model R0... 2≥0.97, indicating good fit.

[0017] In one aspect, the present invention provides a method for preparing a color-enhancing and flavor-enhancing fruit juice by co-fermentation with lactic acid bacteria, comprising the following steps: (1) Raw material pretreatment: Select “Tainong No. 1” mangoes with a maturity of 80-90% or Xuwen “Golden Diamond Pineapple”. After washing, remove the pit and peel from the mangoes, keeping the pulp. Peel the pineapples, keeping the pulp and the tissue around the eyes. Pulp at low temperature to obtain a whole component crude pulp with a particle size ≤100 μm. Among them, mangoes and commercial drinking water are mixed and pulped at a mass ratio of 1:3, and pineapples and commercial drinking water are mixed and pulped at a mass ratio of 1:2. (2) Compound enzymatic hydrolysis: Add 0.15%~0.2% of the mass of the crude fruit pulp obtained in step (1) to the compound enzyme, which is composed of pectinase and cellulase in a mass ratio of 2:1, with pectinase activity ≥40000 U / g and cellulase activity ≥20000 U / g; hydrolyze at 45~50℃ for 60~90 min, stirring continuously at 50~80 r / min during the hydrolysis process, then inactivate the enzyme at 90~95℃ for 5~8 min, and quickly cool to 35~37℃; (3) Preparation: Add 2%-6% fructose syrup, 3%-7% white sugar, 0.06%-0.10% citric acid and 0.06%-0.10% ascorbic acid by weight of the whole component crude fruit pulp, stir well and let it dissolve completely.

[0018] (4) Homogenization by jet mill: The prepared coarse pulp is processed in an industrial-scale micro jet homogenizer at a pressure of 80-160 MPa to obtain the corresponding whole-component fruit juice sample.

[0019] (5) Sterilization: The whole component juice is sterilized by UHT at 137℃ for 5 s and pasteurized at 85℃ for 30 min.

[0020] (6) Activation of strains: Lactobacillus plantarum, Lactobacillus fermentum and Lactobacillus helveticus were inoculated into MRS liquid medium containing 0.8%~1% of the corresponding fruit juice extract, and incubated at 37℃ for 16-20 h until the viable count was ≥1×10⁻⁶. 9 CFU / mL; the three activated bacterial solutions were mixed in a mass ratio of (0.01~2):(0.01~1.5):(0.01~1) to obtain a compound fermentation agent; (7) Co-fermentation: Inoculate 3%-5% (v / w) lactic acid bacteria into the sterilized whole-component juice in step (5), place it in an anaerobic environment with an oxygen content ≤0.5%, and anaerobic constant temperature fermentation at 35-37℃ for 12-36 h; measure the pH value every 6 h during the fermentation process, and control the final pH to 3.4~3.8; after the fermentation is completed, refrigerate at 4℃ for 12 h for post-ripening, and the color-enhanced and aroma-enhanced whole-component fermented juice is obtained.

[0021] In one aspect, the present invention provides a fully-fledged lactic acid bacteria fermented mango / pineapple juice prepared based on the above method.

[0022] In this invention, the prepared whole-component fermented mango juice has a carotenoid content ≥0.85 mg / 100 mL, a sensory score ≥90 points, and a lactic acid bacteria viable count ≥1×10⁻⁶. 8 The prepared whole-component fermented pineapple juice has the following characteristics: CFU / mL, dietary fiber content ≥1.2 g / 100 mL, total sugar content ≤3.8 g / 100 mL, and lactic acid content ≥26.0 mg / g; ascorbic acid content ≥0.44 mg / g, sensory score ≥90 points, and viable lactic acid bacteria count ≥1×10⁻⁶. 8 CFU / mL, dietary fiber content ≥1.2 g / 100 mL, total sugar content ≤4.6 g / 100 mL, lactic acid content ≥2.9 mg / g.

[0023] In one aspect, the present invention provides the application of the above-mentioned whole-component lactic acid bacteria fermented mango juice / pineapple juice in the preparation of functional beverages, fermented foods and health foods.

[0024] In one embodiment, the whole-component fermented fruit juice is directly used as a live bacteria beverage, aseptically filled, refrigerated at 4°C, and has a shelf life of ≥60 days; or it is pasteurized (85°C, 10 min) to make a non-live bacteria beverage, stored at room temperature, and has a shelf life of ≥180 days.

[0025] In one embodiment, the whole-component fermented fruit juice is compounded with other fruit and vegetable juices (such as orange juice and apple juice) at a mass ratio of 1:1 to 3, and 0.1% to 0.2% xanthan gum is added as a stabilizer to prepare a compound fermented fruit and vegetable juice, thereby improving the product's taste and stability.

[0026] Beneficial effects Compared with the prior art, the present invention has the following advantages: (1) Significantly improved sensory quality: Mango juice scored 91.67 points, pineapple juice scored 90.83 points, and color brightness ( L *The value is increased by 15%~20%, the carotenoid retention rate is increased by 25%~30%, and the color change rate after 30 days of storage is ≤5%; the relative content of esters in volatile aroma components is ≥35%, the aroma types are increased by more than 40%, giving it a complex flavor of "fruit aroma + fermentation aroma", without the need for exogenous flavorings.

[0027] (2) Nutritional and functional fortification: All components are retained, resulting in a dietary fiber content ≥1.2 g / 100 mL and a live lactic acid bacteria count ≥1×10⁻⁶. 8 CFU / mL; after fermentation, the lactic acid content reaches 2.97~26.45mg / g, and the total sugar content decreases by 3.7%~24.0%, meeting the requirements for low-sugar health; the ascorbic acid content in pineapple juice increases by 30%, and the carotenoid content in mango juice is ≥0.85 mg / 100 mL.

[0028] (3) Outstanding process innovation: For the first time, Lactobacillus plantarum, Lactobacillus fermentum and Lactobacillus helveticus were applied to the fermentation of all components of mango / pineapple juice in a specific ratio, with excellent strain compatibility; combined with fuzzy mathematical sensory evaluation and response surface methodology, the process was precisely optimized, overcoming the defects of traditional subjective evaluation; low-temperature pulping and anaerobic fermentation control effectively reduced the loss of nutrients due to oxidation. Attached Figure Description

[0029] Figure 1 Fermentation process flow chart; Figure 2 Color comparison chart, (a) mango juice, (b) pineapple juice; Figure 3 GC-MS total ion chromatograms of Example 2 and Comparative Example 6; Detailed Implementation The present invention will be further described below with reference to specific embodiments.

[0030] Lactobacillus plantarum (GDMCC, No. 1.140, purchased from Guangdong Provincial Center for Microbial Culture Collection), Lactobacillus fermentum (GDMCC, No. 1.1796), Lactobacillus helveticus (GDMCC, No. 1.1795); pectinase (40,000 U / g activity, Shanghai Yuanye Biotechnology), cellulase (20,000 U / g activity, Beijing Solarbio); MRS medium.

[0031] Example 1: Preparation of whole-component mango juice by co-fermentation with lactic acid bacteria 1. Raw material pretreatment: Select 25 kg of Panzhihua mangoes, rinse with clean water and remove the pits, retain the pulp (about 20 kg), place it in a -5℃ refrigerator for pre-cooling for 30 min, transfer it to a low temperature pre-pulverizer (XCFG-2018, Beijing Collaborative Innovation Food Technology Co., Ltd.), and use commercial drinking water at a ratio of 1:3 (mass ratio) to pulverize, to obtain a whole-component mango crude pulp with a particle size of 80~100 μm; 2. Compound enzymatic hydrolysis: Add 0.18% (w / w) of compound enzyme (pectinase: cellulase = 2:1) to mango pulp, incubate at 48°C in a constant temperature water bath, stir at 60 r / min for 75 min, then inactivate the enzyme at 92°C for 6 min, and quickly cool to 36°C. 3. Preparation: Add 3% fructose syrup, 6% white sugar, 0.08% citric acid and 0.08% ascorbic acid by weight of the whole component crude fruit pulp to the crude fruit pulp, and stir thoroughly to dissolve completely.

[0032] 4. Homogenization by jet mill: The prepared coarse slurry is processed in a microjet homogenizer at a pressure of 90 MPa to obtain a full-component mango juice sample with a particle size ≤30 μm.

[0033] 5. Sterilization: The whole mango juice is sterilized by UHT at 137℃ for 5 seconds and pasteurized at 85℃ for 30 minutes.

[0034] 6. Strain activation: *Lactobacillus plantarum*, *Lactobacillus fermentum*, and *Lactobacillus helveticus* were inoculated into MRS medium containing 0.8% mango juice extract and cultured at 37°C for 16 h. The viable cell counts were 4.6 × 10⁻⁶. 9 CFU / mL, 3.2×10 9 CFU / mL and 5.4×10 9 A compound lactic acid bacteria starter culture was prepared by mixing CFU / mL of bacteria at a ratio of 1.5:1:0.8.

[0035] 7. Co-fermentation: 3% (v / w) compound lactic acid bacteria were added to the sterilized whole-component mango juice, and the mixture was transferred to an anaerobic incubator (oxygen content 0.3%) and fermented at 36℃ for 30 h. The pH value was monitored during the fermentation process. The final pH value was 3.5. The mixture was then refrigerated at 4℃ for 12 h to obtain the whole-component fermented mango juice.

[0036] Example 2: Preparation of whole-component pineapple juice by co-fermentation with lactic acid bacteria 1. Raw material pretreatment: Select 30 kg of Golden Diamond pineapple, rinse with clean water and peel, retain the pulp and tissue around the eyes (about 20 kg), place in a -10℃ refrigerator for pre-cooling for 20 min, transfer to a low temperature pre-pulverizer (XCFG-2018, Beijing Collaborative Innovation Food Technology Co., Ltd.), and use commercial drinking water at a ratio of 1:2 (mass ratio) to pulverize, to obtain a whole component pineapple crude pulp with a particle size of 80~100 μm; 2. Compound enzymatic hydrolysis: Add 0.2% (w / w) compound enzyme (pectinase: cellulase = 2:1) to pineapple pulp, incubate at 50℃ in a constant temperature water bath, stir at 80 r / min for 60 min, then inactivate the enzyme at 95℃ for 5 min, and quickly cool to 36℃. 3. Preparation: Add 4% fructose syrup, 5% white sugar, 0.08% citric acid and 0.08% ascorbic acid by weight of the whole component crude fruit pulp to the crude fruit pulp, and stir thoroughly to dissolve completely.

[0037] 4. Homogenization by jet mill: The prepared coarse slurry is processed in a microjet homogenizer at a pressure of 120 MPa to obtain a full-component pineapple juice sample with a particle size ≤20 μm.

[0038] 5. Sterilization: The whole pineapple juice is sterilized by UHT at 137℃ for 5 seconds and pasteurized at 85℃ for 30 minutes.

[0039] 6. Strain activation: *Lactobacillus plantarum*, *Lactobacillus fermentum*, and *Lactobacillus helveticus* were inoculated into MRS medium containing 1% pineapple juice extract and cultured at 37°C for 18 h. The viable cell counts were 5.2 × 10⁻⁶. 9 CFU / mL, 3.6×10 9 CFU / mL and 2.8×10 9 A compound lactic acid bacteria starter culture was prepared by mixing CFU / mL of bacteria at a ratio of 1:1.2:0.6.

[0040] 7. Co-fermentation: 3% (v / w) compound lactic acid bacteria were added to the sterilized whole-component pineapple juice, and the mixture was transferred to an anaerobic incubator (oxygen content 0.3%) and fermented at 36℃ for 12 h. The pH value was monitored during the fermentation process. The final pH value was 3.8. The mixture was then refrigerated at 4℃ for 12 h to obtain the whole-component fermented pineapple juice.

[0041] Comparative Example 1: Mango Juice Fermented with a Single Lactobacillus Plantarum Compared with Example 1, only Lactobacillus plantarum was used as the starter culture, and the rest of the process was the same, to obtain single-strain fermented mango juice; Comparative Example 2: Mango Juice Fermented with a Single Lactobacillus Fermentans Compared to Example 1, only Lactobacillus fermentum was used as the starter culture, while the rest of the process was the same, to produce single-strain fermented mango juice. Comparative Example 3: Whole-component mango juice fermented with a single Lactobacillus helveticus Compared to Example 1, only Lactobacillus helveticus was used as the starter culture, while the rest of the process was the same, to produce single-strain fermented mango juice. Comparative Example 4: Traditionally filtered and fermented mango juice Compared with Example 1, the mango pulp was filtered through a 200-mesh filter cloth to remove fruit residue, and the rest of the process was the same to obtain clarified fermented mango juice.

[0042] Comparative Example 5: Unfermented whole-component mango juice Comparative Example 6: Unfermented whole-component pineapple juice Product property determination (a) Sensory evaluation (fuzzy mathematics method) 1. Evaluation system construction: Establishing a factor set U=(U 色泽 U 香气 U 滋味 U 组织状态 ), Comment set A = (A 优 A 良 A 中 A 差 The evaluation levels were correlated with specific scores: excellent, good, average, and poor, corresponding to 90, 70, 50, and 30 respectively, i.e., S = (95, 70, 50, 30). A panel of 12 food professionals was selected to evaluate the juice based on color, aroma, taste, and texture, as shown in Table 1. According to the importance of color, aroma, taste, and texture in the fuzzy mathematical sensory evaluation, the weights were set as X = {0.2, 0.2, 0.4, 0.2}. Y represents the comprehensive sensory evaluation result of the juice, which is the product of the weights and the fuzzy matrix, i.e., Y = X × R. The final comprehensive sensory evaluation score was set as T, T = Y × S. 2. Fuzzy Comprehensive Evaluation: An evaluation matrix was constructed, and the membership degrees were calculated; the results are shown in Table 2.

[0043] Table 1 Sensory Evaluation Criteria for All Components of Mango / Pineapple Juice

[0044] Table 2 Comparison of sensory scores for different samples

[0045] Taking Example 1 as an example, the following comments were obtained: A 色泽 ={0.83 0.17 0.00 0} A 香气 ={0.92 0.08 0 0} A 滋味 ={0.83 0.17 0.08 0} A组织状态 ={0.92 0.08 0 0} The sample has four factor sets: R1 =

[0046] Y1=X×R1=(0.2, 0.2, 0.4, 0.2)×R1={0.87 0.13 0.00 0} T1=Y1×A={0.87 0.13 0.00 0}×(95,70,50,30)=91.67 Similarly, the sensory scores of Comparative Examples 1, 2, 3, 4, 5, and 6 in Example 2 were 90.83, 83.17, 82.75, 82.00, 79.67, 77.58, and 75.50, respectively.

[0047] The sensory scores of Examples 1-2 were significantly higher than those of the control group, indicating that the synergistic effect of the compound microbial strain and enzymatic hydrolysis can effectively improve sensory quality.

[0048] (II) Measurement of color index Measurements were taken using a colorimeter (CR-400, Konica Minolta). L* (brightness), a* (Red-green hue) b* (Yellow-blue hue) values, the results are shown in Table 3: Table 3 Comparison of color indices of different samples

[0049] As shown in Table 1, Example 1 L* value, a* value, b* The values ​​were all significantly higher than those of the control group, indicating that the synergistic effect of the compound strain and enzymatic hydrolysis can effectively improve the color of the whole component juice.

[0050] (III) Determination of aroma components Volatile components were analyzed by GC-MS. Tables 4 and 5 show the main aroma components (relative content %) of different mango juice samples, and Tables 6 and 7 show the main aroma components (relative content %) of different pineapple juice samples.

[0051] Table 4. Analysis of volatile substances in mango juice before and after fermentation

[0052] Table 5 Overall effect of fermentation on mango juice flavor

[0053] The fermentation process fundamentally transforms the flavor profile of mango juice. From "single" to "complex": the single, fresh, and astringent aroma dominated by terpenes before fermentation transforms into a complex aroma composed of esters, lactones, ketones, and alcohols; from "green" to "ripe": the strong pine and resinous aromas (terpenes) diminish, replaced by the sweet aromas of ripe fruit (lactones, esters) and floral notes (ketones, alcohols); from "fresh juice" to "rich fermented drink": the overall flavor becomes fuller and rounder, with the typical mellow aroma of fermentation, resulting in a richer and more layered taste. In short, fermentation brings a richer tropical fruit sweetness, a more elegant floral aroma, and a more rounded and mellow mouthfeel to mango juice, greatly enhancing its flavor complexity and appeal.

[0054] Table 6. Analysis of volatile substances in pineapple juice before and after fermentation (Example 2, Comparative Example 6)

[0055] Table 7 Overall effect of fermentation on the flavor of pineapple juice (Example 2, Comparative Example 6)

[0056] The fermentation process completely reshapes the aroma of pineapple juice. The dominant aroma compounds shift from a ketone-dominated system, represented by 2-heptanone, to an ester-dominated system, represented by ethyl hexanoate and methyl hexanoate. Unpleasant odors are eliminated and improved: the unpleasant 3-methyl-1-butanol is completely consumed, while a more diverse and pleasant array of higher alcohols and esters is generated. The complexity of the aroma is enhanced: various esters, alcohols, and terpenes are newly formed, collectively creating a more intense, layered, and mellow flavor characteristic of fermented pineapple juice.

[0057] (iv) Determination of physicochemical and nutritional indicators Carotenoid content was determined by high performance liquid chromatography (HPLC), organic acids were determined according to GB 5009.157-2016, and total sugar and reducing sugar were determined by the DNS method. The results are shown in Table 8. Table 8 Comparison of physicochemical and nutritional indicators of different samples

[0058] In Example 1, the carotenoid content was almost completely preserved. In Examples 1-2, the lactic acid content was significantly increased, while the total sugar and reducing sugar content decreased, meeting the requirements for a low-sugar diet. (v) Determination of microbial indicators According to GB 4789.35-2023, the viable count of lactic acid bacteria in Examples 1-2 was ≥1.2×10⁻⁶. 8 The CFU / mL count meets the standards for probiotic beverages; in comparison, due to nutrient loss caused by filtration, the viable bacteria count in Example 4 was only 8.5 × 10⁻⁶. 7The CFU / mL ratio indicates that the complete component can optimize the growth environment of the strain.

[0059] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A method for preparing color-enhancing and aroma-enhancing fruit juice through synergistic fermentation with lactic acid bacteria, characterized in that, Includes the following steps: S1. Raw material pretreatment: Mango pulp or pineapple pulp is pulped at low temperature to obtain a whole-component crude fruit pulp with a particle size ≤100 μm; S2. Compound enzymatic hydrolysis: Add 0.15%~0.2% of the mass of the compound enzyme to the crude fruit pulp obtained in step S1, and enzymatically hydrolyze at 45~50℃ for 60~90 min. After enzymatic hydrolysis, inactivate the enzyme and rapidly cool to 35~37℃. The compound enzyme is a mixture of pectinase and cellulase. Preferably, the mass ratio of pectinase to cellulase is 2:

1. S3. Blending: Add flavoring agents to the whole component crude fruit pulp after enzymatic hydrolysis for blending; S4. Homogenization by jet mill: The prepared coarse fruit pulp is processed in a micro jet homogenizer at a pressure of 80-160 MPa to obtain a full-component fruit juice sample. S5. Sterilization: The whole-component juice obtained in step S4 is subjected to UHT sterilization and pasteurization. S6, strain activation: Lactobacillus plantarum, Lactobacillus fermentum and Lactobacillus helveticus are inoculated into MRS liquid medium containing 0.8%-1% corresponding fruit juice extract, and incubated at 37°C for 16-20 h, until the viable cell count is ≥1×10 9 CFU / mL; the three activated bacterial liquids are mixed in a mass ratio of 0.01-2:0.01-1.5:0.01-1 to obtain a composite lactic acid bacteria starter; S7. Co-fermentation: Add 3%-5% (v / w) of compound lactic acid bacteria starter to the sterilized whole-component juice in step S5, place it in an anaerobic environment with an oxygen content ≤0.5%, and anaerobic constant temperature fermentation at 35-37℃ for 12-36 h; measure the pH value every 6 h during the fermentation process, and control the final pH to 3.4~3.8; after the fermentation is completed, refrigerate at 4℃ for 12 h for post-ripening to obtain the color-enhanced and aroma-enhanced whole-component fermented juice.

2. The preparation method according to claim 1, characterized in that, In step S1, before the raw material pretreatment, mangoes / pineapples need to be screened to remove diseased, rotten, and mechanically damaged fruits to ensure uniform ripeness. Before low-temperature pulping, the raw materials are pre-cooled for 30 minutes to avoid the oxidation of carotenoids caused by temperature rise during pulping.

3. The preparation method according to claim 1, characterized in that, In step S2, the compound enzyme is added in a gradient manner. First, add 50% of the compound enzyme and stir for 10 min, then add the remaining 50% of the compound enzyme to continue enzymatic hydrolysis. The pectinase activity is ≥40000 U / g and the cellulase activity is ≥20000 U / g. During the enzymatic hydrolysis process, stirring is carried out continuously at a stirring rate of 50-80 r / min.

4. The preparation method according to claim 1, characterized in that, The flavoring agent mentioned in step S3 includes one or more of fructose syrup, white sugar, citric acid, and ascorbic acid.

5. The preparation method according to claim 1, characterized in that, In step S4, the homogenization pressure is 120 MPa to ensure that the pulp particle size is ≤30 μm.

6. The preparation method according to claim 1, characterized in that, In step S5, UHT sterilization is performed at 137℃ for 5 seconds, and pasteurization is performed at 85℃ for 30 minutes.

7. The preparation method according to claim 1, characterized in that, The whole-component fermented mango / pineapple juice contains ≥0.85 mg / 100 mL of carotenoids, ≥35% of esters in volatile aroma components, and ≥2.97 mg / g of lactic acid.

8. A whole-component lactic acid bacteria fermented mango / pineapple juice prepared by the method according to any one of claims 1-7, characterized in that, Live bacteria count ≥ 1 x 10 8 CFU / mL, dietary fiber content ≥ 1.2 g / 100 mL, without exogenous colorants and flavorings.

9. The application of the preparation method according to any one of claims 1-7 in the development of color-enhancing and aroma-enhancing whole-component fruit and vegetable juices and functional fermented beverages.

10. A compound fermented fruit and vegetable juice, characterized in that, The fruit and vegetable juices include whole-component lactic acid bacteria fermented mango / pineapple juice prepared by any of the methods described in claims 1-7.

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