Method for reducing content of alpha-tomatine in green tomatoes and improving flavor of green tomatoes through probiotic fermentation

Abstract

The invention discloses a method for reducing the content of alpha-tomatine in green tomatoes and improving the flavor of the green tomatoes through probiotic fermentation, and belongs to the field of food processing. A strain which can grow in a green tomato system and can reduce alpha-tomaquine and improve the flavor of the alpha-tomaquine is obtained through screening, and a specific operation mode and fermentation treatment time are explored on the basis. By using the lactobacillus plantarum CICC 22703 to ferment the green tomatoes, alpha-tomaquine in the green tomatoes can be effectively reduced, the composition proportion of main organic acids, sweet and delicious amino acids and volatile flavor substances contained in the green tomatoes is improved, and the flavor of the green tomatoes is improved. The method is controllable in production cost, not only can effectively utilize immature green tomato resources, but also can endow the immature green tomato with unique flavor, and meets the pursuit of consumers for healthy and delicious food.

Description

Technical Field

[0001] The invention relates to a method for reducing the content of alpha-tomatine in green tomatoes and improving the flavor thereof through probiotic fermentation, and belongs to the field of food processing. Background Art

[0002] Tomato (Solanum lycopersicum L.) is an annual herbaceous plant of the Solanaceae family, rich in minerals, dietary fiber, vitamins, essential amino acids, sugars, carotenoids and phenolic substances. The annual production of fresh tomatoes worldwide is about 180 million tons. Fully ripe tomato fruits are soft in texture and easily cause mechanical damage and rot during transportation, so tomato fruits are often harvested when they are not fully ripe. Therefore, in the tomato value chain, unripe fruits that are considered unsuitable for sale in the market or for the production of tomato by-products due to their partial maturity and color have great recycling potential.

[0003] Unripe tomatoes are green and have a hard texture. Compared with ripe tomatoes, unripe tomatoes contain less sugar and have a crisper taste. Studies have shown that eating unripe tomatoes has multiple benefits, such as anti-inflammatory activity, lowering low-density lipoprotein cholesterol levels, promoting humoral immunity and cellular immunity, and maintaining blood pressure stability. However, excessive consumption may lead to potential health risks such as gastrointestinal dysfunction and tachycardia due to its higher content of tomatine. Traditional methods of reducing α-tomatine involve chemical treatment, which may have a negative impact on the flavor of tomatoes; in the traditional cooking process of green tomatoes, high temperatures degrade α-tomatine, but at the same time, it also causes the texture of tomatoes to be destroyed and lose their unique taste. Therefore, finding a method to reduce α-tomatine in green tomatoes and improve their flavor is crucial to effectively utilize unripe green tomato resources and reduce resource waste.

[0004] In the invention patent application with publication number CN113892574A, tomato juice was fermented with plant lactobacillus, and a large amount of metabolites such as organic acids, alcohols and various amino acids were produced after fermentation; in the invention patent application with publication number CN109770288A, tomatoes were fermented with plant lactobacillus and Lactobacillus pentosus (2:1) composite bacteria, and the fermented tomatoes had low nitrite content; the fermented tomatoes also had a light fragrance, which increased appetite. The above prior art did not propose a solution to α-tomatine in green tomatoes. In a study, the pH value, total sugar, total acid content, total phenol and total flavonoid content, ABTS free radical scavenging rate and DPPH free radical scavenging rate of tomato juice after fermentation with plant lactobacillus were measured (Response surface optimization of plant lactobacillus fermentation tomato juice process and quality evaluation. Food Industry Science and Technology, 2022, 43 (10): 246-253.), but the method did not mention how to reduce α-tomatine in tomatoes and produce flavor compounds.

[0005] The raw materials used in the above prior art are all ripe tomatoes. There are certain differences in the taste, flavor and nutritional value of unripe tomatoes, i.e. green tomatoes, and ripe tomatoes; further, the content of some components in green tomatoes and ripe tomatoes is also very different, such as vitamin C, lycopene, α-tomatine, etc. Green tomatoes contain a higher content of α-tomatine, while its content in ripe tomatoes is extremely low or non-existent.

[0006] In order to make full use of unripe tomato resources, reduce the α-tomatine content in green tomatoes, alleviate potential health risks, and improve their flavor and quality, finding a method that can effectively reduce the α-tomatine content in green tomatoes and improve their flavor characteristics has become a technical problem that needs to be solved urgently. Summary of the invention

[0007] In view of the above problems, the present invention provides a method that can effectively reduce the α-tomatine content in green tomatoes and improve their flavor. By adopting the method of biological fermentation, a large number of strains that can grow in the green tomato system and can reduce α-tomatine and improve its flavor are screened from existing microbial species. On this basis, specific operation methods and fermentation treatment times are explored, and a solution that can effectively solve the above problems is obtained. This method can quickly and effectively reduce α-tomatine, improve the composition ratio of the main organic acids, sweet and umami amino acids and volatile flavor substances contained in green tomatoes, retain its taste, and enhance the flavor of green tomatoes. This method has controllable production costs, can not only effectively utilize the resources of immature green tomatoes, but also give them a unique flavor, satisfying consumers' pursuit of healthy and delicious food.

[0008] The first object of the present invention is to provide a method for reducing the content of α-tomatine in green tomatoes and improving their flavor, wherein the method is to reduce the content of α-tomatine in green tomatoes and improve their flavor by fermenting green tomatoes with Lactiplantibacillus plantarum CICC 22703.

[0009] In one embodiment of the present invention, the method specifically comprises the following steps: treating green tomatoes, soaking them in water, inoculating the seed liquid of Bacillus plantarum into the soaked tomatoes for fermentation, and obtaining fermented green tomatoes.

[0010] In one embodiment of the present invention, the processing of green tomatoes includes but is not limited to slicing, chopping or juicing the green tomatoes.

[0011] In one embodiment of the present invention, preferably, the processing of green tomatoes is slicing the green tomatoes to retain their crisp taste.

[0012] In one embodiment of the present invention, the viable count of the seed solution is 10 7 ~10 9 CFU / mL, inoculum size 2-4% v / w;

[0013] Preferably, the viable count is 10 7 CFU / mL, the inoculum size was 3% v / w.

[0014] In one embodiment of the present invention, the fermentation condition is 15-20°C for more than 72 hours;

[0015] Preferably, the fermentation condition is fermentation at 18°C ​​for 72 hours.

[0016] In one embodiment of the present invention, the amount of water added is 90% to 110% w / w of the green tomatoes;

[0017] Preferably, the mass ratio of the added water to the green tomatoes is 1:1.

[0018] In one embodiment of the present invention, the seed liquid of Bacillus plantarum is obtained by the following steps:

[0019] (1) inoculating the activated plant lactobacillus into sterilized green tomato juice to obtain a culture solution;

[0020] (2) The culture solution obtained in step (1) is inoculated into green tomato juice to obtain a seed solution of the strain.

[0021] In one embodiment of the present invention, the green tomato juice is obtained by mixing and pulping green tomatoes with water in a mass ratio of (0.8-1.2): (1.8-2.2), and then sterilizing.

[0022] Preferably, the ratio is 1:2.

[0023] In one embodiment of the present invention, the sterilization condition is 110-125°C for 10-20 min;

[0024] Preferably, the sterilization condition is 121° C. for 15 min.

[0025] In one embodiment of the present invention, the culture condition in step (1) is culture at 35-38°C for 10-12 hours; preferably, the culture condition is culture at 37°C for 12 hours.

[0026] In one embodiment of the present invention, the culture condition in step (2) is culturing at 35-38° C. for 4-6 hours; preferably, the culture condition is culturing at 37° C. for 5 hours.

[0027] In one embodiment of the present invention, the method comprises the following steps:

[0028] (1) Chop green tomatoes and mix them with water in a mass ratio of 1:2 to obtain green tomato juice, which is sterilized at 121°C for 15 minutes; use a 5 μL inoculation loop to take a loop of Lactobacillus plantarum CICC 22703 and inoculate it into 10 mL of the green tomato juice, culture it at 37°C for 12 hours, then take 5 mL of the culture solution and inoculate it into 45 mL of sterilized tomato juice, culture it at 37°C for 5 hours, and make the number of viable bacteria reach 10 7 CFU / mL, and the seed solution of Lactobacillus plantarum was obtained.

[0029] (2) Take green tomato slices, add an equal mass of water to soak the sliced ​​tomatoes, and inoculate the seed solution obtained in step (1) into the soaked sliced ​​tomatoes at a ratio of 3% v / w, and ferment at 18° C. for 72 hours to obtain fermented green tomato slices.

[0030] The second object of the present invention is to provide a fermented green tomato product, which is prepared by the above method.

[0031] In one embodiment of the present invention, the fermented green tomato products include but are not limited to fermented green tomato slices, fermented green tomato pieces, and fermented green tomato juice.

[0032] The third object of the present invention is to provide use of the above method or the above fermented green tomato product in preparing green tomato products.

[0033] In one embodiment of the present invention, the fermented green tomato products include but are not limited to fermented green tomato slices, fermented green tomato pieces, and fermented green tomato juice.

[0034] In one embodiment of the present invention, the green tomato products include but are not limited to green tomato drinks, green tomato sauce, and canned green tomatoes.

[0035] Beneficial effects:

[0036] The inventors adopted biological fermentation technology to extensively screen the existing microbial species suitable for growing in a system with green tomatoes as raw materials, and successfully selected a specific strain that can grow stably in a green tomato environment, effectively degrade α-tomatine and optimize the flavor. The inventors conducted a lot of exploration on how to use probiotics to solve the problems of the prior art, and finally screened out a strain of Lactobacillus plantarum CICC 22703, which effectively reduced the α-tomatine content of green tomatoes and significantly improved the flavor quality by controlling the inoculation amount and fermentation time.

[0037] (1) The present invention utilizes Lactobacillus plantarum to ferment green tomatoes, and the α-tomatine in the obtained fermented green tomatoes is greatly reduced, with a degradation rate of 35.66%;

[0038] (2) After fermentation with Lactobacillus plantarum, green tomatoes can produce a large amount of organic acids, with lactic acid and citric acid contents reaching 3.32 mg / mL and 2.11 mg / mL, respectively. After fermentation with Lactobacillus plantarum, green tomatoes produce a large amount of sweet amino acids, umami amino acids, and flavor substances such as alcohols, ketones, aldehydes, and esters, which significantly improves the flavor of green tomatoes and satisfies consumers' pursuit of healthy and delicious food.

[0039] (3) Green tomatoes are fermented at a relatively low temperature, which can appropriately preserve the hardness and crispness of green tomatoes, that is, retain their unique crisp taste; in addition, it can extend the shelf life, retain nutrients, and be safer;

[0040] (4) The method for improving the flavor quality of green tomatoes provided by the present invention has low production cost and is quick and simple to operate;

[0041] (5) The present invention can reduce waste generated by immature tomatoes by converting immature green tomatoes into fermented products, thereby helping to reduce resource waste and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the principal component analysis (PCA) diagram of five indicators: α-tomatine degradation rate, sensory score, pH value, fresh and sweet amino acids, and main organic acid content of six strains. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below in conjunction with specific embodiments to facilitate understanding by those skilled in the art.

[0044] The raw materials involved in the following examples are as follows:

[0045] Lactobacillus plantarum CICC 22703, Lactobacillus rhamnosus CICC 6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, Lactobacillus paracasei CICC 20286, and Lactococcus lactis CICC 23610 were purchased from China Industrial Microbiological Culture Collection Center.

[0046] The unripe tomatoes were in the green stage and were purchased from an e-commerce platform. The origin of the tomatoes is Xiangyang City, Hubei Province.

[0047] The culture medium involved in the following examples is as follows:

[0048] MRS agar medium was purchased from Qingdao Haibo, catalog number HB0384;

[0049] MRS broth medium was purchased from Qingdao Haibo, catalog number HB0384-1;

[0050] The culture medium mentioned above is a finished culture medium. It can be used after being weighed and dissolved in water according to the instructions, sterilized at 121°C for 15 minutes and cooled to room temperature.

[0051] Preparation method of solid slant culture medium: Heat to dissolve MRS agar culture medium, pipette 8 mL into a test tube while it is still hot, sterilize it and place it on a clean bench at an angle, and wait for it to cool until solidified.

[0052] The bacterial activation method involved in the following embodiments is as follows:

[0053] Take the lyophilized tube of the strain and pipette it, absorb 1mL of MRS broth medium to dissolve it, and transfer it to a test tube containing 9mL of MRS broth medium, and culture it at the optimal temperature for 12h; absorb 1mL of culture solution into 9mL of MRS broth medium and culture it at the optimal temperature for about 12h. Use 1μL inoculation loop to dip the culture solution into MRS solid slant medium and streak it, culture it at the optimal temperature for 48h, and then transfer it to a 2℃ refrigerator for storage. The culture temperature of Lactobacillus plantarum CICC 22703, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, and Lactobacillus casei CICC 20286 is 37℃, and the culture temperature of Lactobacillus rhamnosus CICC6001 and Lactococcus lactis CICC 23610 is 30℃.

[0054] The detection methods involved in the following embodiments are as follows:

[0055] 1. pH detection method:

[0056] The pH value of the fermented green tomatoes was measured by a pH meter, and the fermented green tomatoes were pulped and mixed before the measurement.

[0057] 2. α-Tomatine determination method:

[0058] The green tomato slices before and after fermentation were freeze-dried, 1 g of freeze-dried powder was weighed, acetic acid-methanol solution (2%, v / v) was added, stirred and extracted for 2 h, the supernatant was taken and the precipitate was washed twice, the supernatant was combined, rotary evaporated and concentrated to 3-5 mL, 2 mol / L hydrochloric acid solution was added to dissolve, centrifuged at 10000 rpm at 4 ° C for 10 minutes, the pH of the supernatant was adjusted to 10.5-11.0 with ammonia water, kept at 65 ° C for 50 minutes and refrigerated overnight, centrifuged at 10000 rpm for 10 minutes, the precipitate was blown dry with nitrogen, and dissolved with 2 mL of methanol. HPLC equipped with an evaporative light detector was used for analysis. Chromatographic column: C18 column, liquid phase conditions: column temperature 30 ° C; flow rate 1 mL / min; injection volume 20 μL; ELSD drift tube temperature 80 ° C, carrier gas flow rate 2.5 L / min. The mobile phase A was 0.1% formic acid-water solution, and the mobile phase B was 0.1% formic acid-acetonitrile. The gradient elution method was adopted, and the mobile phase B gradient changed from 0min to 5min, and the B phase changed from 30% to 40%; from 5min to 20min, the B phase was kept at 40%; from 20min to 22min, the B phase changed from 40% to 30%; from 22min to 25min, the B phase was kept at 30%, and the total running time was 25min.

[0059] The calculation method of α-tomatine degradation rate is as follows:

[0060] α-tomatine degradation rate = (α-tomatine content of sample before fermentation - α-tomatine content of sample after fermentation) / α-tomatine content of sample before fermentation

[0061] α-Tomatine content unit: μg / g freeze-dried powder.

[0062] 3. Brittleness determination method:

[0063] The test was conducted using a texture analyzer equipped with a P2 probe in TPA mode. The speed before the test was 10 mm / s, the speed during the test was 5 mm / s, the speed after the test was 10 mm / s, the compression ratio was 70%, and the interval between the two tests was 5 seconds.

[0064] 4. Organic acid determination method:

[0065] After diluting the sample 5 times, centrifuge it at 10000r / min at 4°C for 10min, collect the supernatant and filter it through a 0.45μm water filter for determination. Use HPLC equipped with a C18 column for determination. Column temperature 30°C, injection volume 5μL. Elution was performed with a gradient of 0.1% phosphoric acid solution and methanol (97.5:2.5, v / v) at a flow rate of 1mL / min. A diode array detector (DAD) was used with a detection wavelength of 210nm. The standard is a mixed standard containing malic acid, citric acid, lactic acid, fumaric acid, acetic acid, succinic acid, propionic acid, and butyric acid.

[0066] 5. Determination method of volatile flavor substances:

[0067] The volatile flavor substances in the samples were determined by GC-MS. Solid phase microextraction was used for sample pretreatment: 3.0 g of sample was accurately weighed and placed in a 20 mL headspace bottle, and 20 μL of 4-methyl-2-pentanol (20 mg / mL) was added to it. The aged extraction head (50 / 30 μm, DVB / PDMS / CAR) was inserted into the sample bottle and adsorbed at 50 ° C for 30 min. After removal, it was inserted into the gas chromatography injection port and desorbed at 250 ° C for 3 min. The extraction head was withdrawn and the extractor was pulled out, and the instrument was started to collect data.

[0068] Gas chromatography (GC) conditions: using a DB-WAX (30m×0.25mm, 0.25μm) chromatographic column, the starting temperature was 40℃; the injection port temperature was 250℃; the heating process was first maintained at 40℃ for 4min, then increased to 90℃ at a rate of 5℃ / min, and then immediately increased to 230℃ at a rate of 1℃ / min and maintained for 6min; carrier gas: high purity He, flow rate 0.8mL / min.

[0069] Mass spectrometry (MS) conditions: EI ionization mode, emission current and energy are 70μA and 70eV respectively, ion source temperature is 200℃, quadrupole temperature is 150℃, interface temperature is 250℃, mass-to-charge ratio is 30-500. The retrieved volatiles are matched with the NIST standard spectral library, and those with a similarity of more than 80% are identified as target compounds. The relative content of volatile substances is quantitatively analyzed using the internal standard method.

[0070] 6. Free amino acid determination method:

[0071] The amino acid was determined using an automatic liquid phase analyzer.

[0072] 7. The sensory scoring standards are shown in Table 1:

[0073] Table 1

[0074]

[0075]

[0076] Example 1: Fermentation of green tomatoes with Lactobacillus plantarum CICC 22703

[0077] 1. Cultivation of strains: Activate the lyophilized tube of Bacillus plantarum CICC 22703 in MRS solid slant medium and store at 2°C; chop green tomatoes and mix with water at a mass ratio of 1:2 to make green tomato juice, which is then sterilized at 121°C for 15 minutes. Use a 5μL inoculation loop to scrape a loop of Bacillus plantarum from the slant medium and inoculate it into 10mL of green tomato juice, culture it at 37°C for 12h, then take 5mL of culture medium and inoculate it into 45mL of sterilized tomato juice, culture it at 37°C for 5h, so that the number of viable bacteria reaches 10 7 CFU / mL, and the seed solution of Lactobacillus plantarum was obtained.

[0078] 2. Preparation of fermented green tomatoes: Take green tomatoes with smooth appearance and no mechanical damage, remove the fruit stems, wash the surface soil with running water, rinse with sterile water, wipe clean and cut into slices with a thickness of about 0.5-1.0 cm, add sterile water of equal mass, and inoculate the seed liquid of Lactobacillus plantarum CICC 22703 into the soaked sliced ​​tomatoes at a ratio of 3% (seed liquid volume: sterile water and tomato slice mass), ferment at 18° C. for 72 hours, and obtain fermented green tomato slices.

[0079] The texture characteristics, pH, α-tomatine degradation rate, organic acids, volatile flavor substances, free amino acids, and sensory scores of the green tomato slices fermented by Lactobacillus plantarum CICC 22703 obtained above were measured, and the results were as follows:

[0080] Table 2 Determination of α-tomatine in green tomato slices fermented by Lactobacillus plantarum CICC 22703

[0081]

[0082]

[0083] Table 3 Determination of various indicators of green tomato slices fermented by Lactobacillus plantarum CICC 22703

[0084] index Numeric Hardness(g) 458.51 Crispness(g) 453.40 Cohesion 0.09 pH 3.99 Comprehensive sensory score 81.75

[0085] Table 4 Determination of free amino acids in green tomato slices fermented by Lactobacillus plantarum CICC 22703

[0086] Amino Acids (mg / kg) Numeric Amino Acids (mg / kg) Numeric ASP 74.13 VAL 16.23 GLU 186.54 MET 3.18 SER 6.28 TRP 322.34 HIS 6.39 PHE 54.32 GLY 23.98 ILE 23.30 THR 12.12 LEU 27.33 ARG 31.25 LYS 39.46 ALA 12.01 PRO 15.6 TYR 39.33 Sweet amino acids 42.27 CYS 5.04 Umami Amino Acids 260.67

[0087] Table 5 Determination of organic acids in green tomato slices fermented by Lactobacillus plantarum CICC 22703

[0088] Organic acid (mg / mL) Numeric Organic acid (mg / mL) Numeric Malic Acid 0.84 Succinic acid 0.05 lactic acid 3.32 Fumaric Acid 0.01 Acetic acid 0.11 Propionic acid 0.23 Citric Acid 2.11 Butyric acid 0.39

[0089] Table 6 Determination of volatile flavor compounds in green tomato slices fermented by Lactobacillus plantarum CICC 22703

[0090]

[0091]

[0092] As shown in Tables 2 to 6, after 72 hours of fermentation with Lactobacillus plantarum, the degradation rate of α-tomatine in green tomatoes reached 35.66%, which was significantly higher than that of the uninoculated control group, and maintained a good crisp taste and a certain cohesion, with good feedback in sensory evaluation. At the same time, the content of major organic acids was richer after fermentation, which enhanced the "sour and refreshing" taste of green tomato slices. The amino acid content was significantly increased, especially the sweet amino acid and umami amino acid, which reached 42.27 mg / kg and 260.67 mg / kg after fermentation. Leaf alcohol with a strong green leaf fragrance and 3-hydroxy-2-butanone with both butter and grass aroma contribute to the main flavor of green tomato slices fermented by Lactobacillus plantarum, reaching 140.17 μg / kg and 137.54 μg / kg respectively after 72 hours of fermentation; at the same time, substances such as n-hexanal, n-hexanol, and 2-tridecanone also contribute to fruity, nutty, floral, and herbal aromas, making the fermented green tomato slices present a rich, diverse, refreshing, and multi-layered flavor. Example 2: Green tomatoes fermented by Lactobacillus rhamnosus CICC 6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, Lactobacillus paracasei CICC 20286, or Lactococcus lactis CICC 23610

[0093] 1. Cultivation of strains: Lactobacillus rhamnosus CICC 6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC20375, Lactobacillus paracasei CICC 20286, and Lactococcus lactis CICC 23610 were activated in MRS solid slant medium and stored at 2°C; green tomatoes were chopped and mixed with water at a mass ratio of 1:2 to obtain green tomato juice, which was then sterilized at 121°C for 15 minutes. A 5μL inoculation loop was used to take a loop of Lactobacillus rhamnosus, Lactobacillus helveticus, Streptococcus thermophilus, Lactobacillus paracasei, or Lactococcus lactis, respectively, and inoculated into 10mL of green tomato juice, cultured at the optimal temperature for 12h, and then 5mL of culture solution was taken from it and inoculated into 45mL of sterilized tomato juice, and cultured at the optimal temperature for 5h to make the number of viable bacteria reach 10 7CFU / mL, the seed solution of Lactobacillus rhamnosus, Lactobacillus helveticus, Streptococcus thermophilus, Lactobacillus paracasei and Lactococcus lactis was obtained. Among them, Lactobacillus rhamnosus and Lactococcus lactis were cultured at 30°C, and Lactobacillus helveticus, Streptococcus thermophilus and Lactobacillus paracasei were cultured at 37°C.

[0094] 2. Preparation of fermented green tomatoes: Take green tomatoes with smooth appearance and no mechanical damage, remove the fruit stems and wash the epidermis with running water to remove the dirt, rinse with sterile water, wipe and cut into slices with a thickness of about 0.5-1.0 cm, add sterile water of equal mass, and inoculate the seed liquids of Lactobacillus rhamnosus CICC 6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, Lactobacillus paracasei CICC 20286 and Lactococcus lactis CICC23610 into the soaked sliced ​​tomatoes at a ratio of 3% (seed liquid volume: sterile water and tomato slice mass), respectively, and ferment at 18°C ​​for 72 hours to obtain fermented green tomato slices.

[0095] The pH, α-tomatine degradation rate, organic acid, free amino acid, and sensory score of the five fermented green tomato slices obtained above and the green tomato slices not fermented with lactic acid bacteria were measured, and the results are as follows:

[0096] Table 7 Degradation rate of α-tomatine after fermentation by different strains

[0097]

[0098] Table 8 pH values ​​after fermentation of different strains

[0099]

[0100] Table 9 Changes of free amino acids after fermentation of different strains

[0101]

[0102]

[0103] Table 10 Changes of main organic acids after fermentation of different strains

[0104]

[0105] Table 11 Comprehensive sensory scores of different strains after fermentation

[0106] strains CICC 23610 CICC 20375 CICC 20275 CICC 20286 CICC 6001 Comprehensive score 62.00 61.61 83.00 56.25 41.25

[0107] Compared with the control group, the degradation rate of α-tomatine in green tomato slices fermented by Lactobacillus rhamnosus CICC 6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC20375, Lactobacillus paracasei CICC 20286 or Lactococcus lactis CICC 23610 was significantly increased, but significantly lower than the degradation rate of α-tomatine in green tomatoes fermented by Lactobacillus plantarum CICC 22703 in Example 1 (35.66%) (Table 7);

[0108] The pH of green tomatoes fermented by the five bacteria was lower than that of the control group and unfermented tomatoes, but the pH of green tomatoes fermented by Bacillus plantarum CICC 22703 in Example 1 was the lowest, at 3.99 (Table 8); the total content of free amino acids in green tomato slices fermented by Lactobacillus rhamnosus CICC6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, Lactobacillus paracasei CICC 20286 or Lactococcus lactis CICC 23610 was significantly increased. Among them, the content of sweet amino acids and umami amino acids in green tomato slices fermented by Lactobacillus helveticus CICC20275 was relatively high, contributing the most to the overall flavor, but still slightly lower than the 42.27 mg / kg and 260.67 mg / kg of green tomato slices fermented by Bacillus plantarum CICC 22703 in Example 1 (Table 9);

[0109] The content of main organic acids in green tomato slices fermented by Lactobacillus rhamnosus CICC 6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, Lactobacillus paracasei CICC 20286 or Lactococcus lactis CICC 23610 increased, and each strain had a strong acid production ability, and the content of lactic acid, the main fermentation product, was significantly improved, but it was still slightly lower than the lactic acid content (3.32 mg / mL) after fermentation by Lactobacillus plantarum CICC 22703 in Example 1 (Table 10);

[0110] Compared with other bacteria, the green tomato slices fermented by Lactobacillus helveticus CICC 20275 and Lactobacillus plantarum CICC22703 in Example 1 had the highest comprehensive sensory scores, which were 83.00 and 81.75, respectively (Table 11).

[0111] By principal component analysis (PCA), five indicators including α-tomatine degradation rate, sensory score, pH value, sweet amino acid and main organic acid content were selected for dimension reduction, and two principal components PC1 and PC2 were generated. The test results of green tomato slices fermented by Lactobacillus rhamnosus CICC6001, Lactobacillus helveticus CICC 20275, Streptococcus thermophilus CICC 20375, Lactobacillus paracasei CICC 20286, Lactococcus lactis CICC 23610 and Lactobacillus plantarum CICC 22703 in Example 1 were ranked by scores ( Figure 1 ), among which the green tomato slices fermented by Lactobacillus plantarum CICC 22703 strain in Example 1 scored the highest.

[0112] Example 3: Effects of different inoculation amounts of Lactobacillus plantarum CICC 22703 on green tomato fermentation

[0113] 1. Cultivation of strains: Activate the lyophilized tube of Lactobacillus plantarum CICC 22703 in MRS solid slant medium and store at 2°C; chop green tomatoes and mix with water at a mass ratio of 1:2 to make green tomato juice, which is then sterilized at 121°C for 15 minutes. Use a 5μL inoculation loop to take a loop of the strain and inoculate it into 10 mL of green tomato juice, culture it at 37°C for 12 hours, then take 5 mL of the culture medium and inoculate it into 45 mL of sterilized tomato juice, and culture it at 37°C for 5 hours until the number of viable bacteria reaches 10 7 CFU / mL, and the seed solution is obtained.

[0114] 2. Preparation of fermented green tomatoes: Take green tomatoes with smooth appearance and no mechanical damage, remove the fruit stems and wash the surface soil with running water, rinse with sterile water, wipe clean and cut into slices with a thickness of about 0.5-1.0 cm, add equal weight of sterile water, and add 1% and 5% (seed liquid volume: sterile water and tomato slice weight) to the soaked sliced ​​tomatoes, respectively, and ferment at 18° C. for 72 hours to obtain fermented green tomato slices.

[0115] The pH, α-tomatine degradation rate, organic acid, free amino acid and sensory score of the two fermented green tomato slices obtained above were measured, and the results were as follows:

[0116] Table 12 Changes of free amino acids at different inoculation amounts

[0117]

[0118] Table 13 Changes of organic acids at different inoculation amounts

[0119]

[0120]

[0121] Table 14 pH value changes at different inoculation amounts

[0122] Inoculation volume 1％ 5％ pH 4.08 3.77

[0123] Table 15 Degradation rate of α-tomatine after fermentation with different strain inoculation amounts

[0124]

[0125] Table 16 Comprehensive sensory scores after fermentation with different strain inoculation amounts

[0126] Inoculation volume 1％ 5％ Comprehensive score 73.0 75.6

[0127] As shown in Tables 12 to 16, CICC 22703 plant lactobacillus was inoculated in soaked green tomato slices at 1% and 5% inoculations, and the degradation rate of α-tomatine was significantly reduced compared with the control group in Example 2, which were 25.35% and 37.59% respectively. The 5% inoculation was compared with the 3% inoculation in Example 1. The α-tomatine degradation rate (35.66%) did not significantly improve it, but increased the cost. With the increase of organic acid content, the pH value after fermentation decreased to varying degrees, and the main organic acids lactic acid and citric acid changed significantly, but in the 1% inoculation experiment, the acid production capacity was significantly weaker than other groups. The content of sweet amino acids and umami amino acids was not significantly improved compared with the 3% inoculation of plant lactobacillus CICC 22703 in Example 1. Considering the cost and effect, the 3% inoculation is the best choice.

[0128] Example 4: Effect of different fermentation times on green tomato fermentation

[0129] 1. Cultivation of strains: Activate the lyophilized tube of Lactobacillus plantarum CICC 22703 in MRS solid slant medium and store at 2°C; chop green tomatoes and mix with water at a mass ratio of 1:2 to make green tomato juice, and then sterilize at 121°C for 15 minutes. Use a 5μL inoculation loop to take a loop of strains and inoculate it into 10mL green tomato juice, culture it at 37°C for 12h, then take 5mL of culture medium from it and inoculate it into 45mL sterilized tomato juice, and culture it at 37°C for 5h until the number of viable bacteria reaches 10 7 CFU / mL, and the seed solution is obtained.

[0130] 2. Preparation of fermented green tomatoes: Take green tomatoes with smooth appearance and no mechanical damage, remove the fruit stems and wash the surface soil with running water, rinse with sterile water, wipe clean and cut into slices with a thickness of about 0.5-1.0 cm, add an equal mass of sterile water, and add 3% (seed liquid volume: sterile water and tomato slice mass) to the soaked sliced ​​tomatoes, ferment at 18° C., and obtain fermented green tomato slices fermented for 0, 24, 48, 60, and 84 hours.

[0131] The texture characteristics, pH, α-tomatine degradation rate, organic acids, volatile flavor substances, and free amino acids of the fermented green tomato slices obtained above were determined, and the results were as follows:

[0132] Table 17 Changes in texture characteristics during fermentation of Lactobacillus plantarum CICC 22703

[0133] Fermentation time (h) Hardness(g) Crispness(g) Cohesion 0 551.81 583.206 0.042 24 514.397 517.132 0.049 48 494.142 510.552 0.046 60 490.638 481.81 0.096 84 307.581 331.312 0.106

[0134] Table 18 Changes in the degradation rate of α-tomatidine during the fermentation process of Lactobacillus plantarum CICC 22703

[0135]

[0136] Table 19 pH of the fermentation process of Lactobacillus plantarum CICC 22703

[0137] Fermentation time (h) pH 0 4.44 24 4.62 48 4.21 60 3.94 84 3.78

[0138] Table 20 Changes of main organic acids during fermentation of Lactobacillus plantarum CICC 22703

[0139]

[0140]

[0141] Table 21 Volatile flavor substances during fermentation of Lactobacillus plantarum CICC 22703

[0142]

[0143]

[0144] Table 22 Changes of free amino acids during fermentation of Lactobacillus plantarum CICC 22703

[0145]

[0146] As shown in Tables 17 to 22, in the green tomato slices fermented by Lactobacillus plantarum CICC 22703, as the fermentation time increased, the content of α-tomatine in the green tomato slices showed a downward trend, and the degradation rate of α-tomatine increased significantly after 24 hours, and reached 35.66% at 72 hours of fermentation (Example 1); the pH value showed a gradual downward trend, and was basically stable at 60 to 72 hours, and was accompanied by an increase in major organic acids during this process, among which lactic acid and citric acid as the main organic acids showed an obvious upward trend at 60 to 72 hours, and increased to 3.32 mg / t at 72 hours. mL and 2.11 mg / mL (Example 1), close to the content at 84h; the main volatile flavor substance leaf alcohol reaches the highest value at 60-72h, giving the fermented green tomato slices a strong green leaf fragrance; the umami and sweet amino acids in the free amino acids also reach the highest concentration at 72h of fermentation in Example 1, and the contribution to the flavor is higher than 60h and 84h; in addition, the hardness and crispness of the green tomato slices after fermentation for 72h in Example 1 are moderate, while the hardness and crispness of the green tomato slices after fermentation for 84h are significantly reduced, resulting in a poor taste. Taking into account the cost and changes in various indicators, the green tomato slices fermented for 72h are the best.

[0147] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for reducing the content of α-tomatine in green tomatoes and improving their flavor, characterized in that: The method is to reduce the α-tomatine content in the green tomatoes and improve the flavor of the green tomatoes by fermenting green tomatoes with Bacillus plantarum CICC 22703.

2. The method according to claim 1, characterized in that The method specifically comprises the following steps: treating green tomatoes, soaking them in water, inoculating the seed liquid of Bacillus plantarum into the soaked tomatoes for fermentation, and obtaining fermented green tomatoes; Preferably, the processing of green tomatoes includes but is not limited to slicing, chopping or juicing the green tomatoes.

3. The method according to claim 2, characterized in that The viable count of the seed solution is 10 7 ~10 9 CFU / mL, the inoculation amount is 2% to 4% v / w; preferably, the viable count is 10 7 CFU / mL, the inoculum size was 3% v / w.

4. The method according to claim 2, characterized in that: The fermentation condition is 15-20° C. for more than 72 hours; preferably, the fermentation condition is 18° C. for 72 hours.

5. The method according to claim 2, characterized in that: The amount of water added is 90% to 110% w / w of the green tomatoes.

6. The method according to claim 2, characterized in that The seed liquid of the plant lactobacillus is obtained by the following steps: (1) inoculating the activated plant lactobacillus into sterilized green tomato juice to obtain a culture solution; (2) The culture solution obtained in step (1) is inoculated into green tomato juice to obtain a seed solution of the strain.

7. The method according to claim 6, characterized in that The green tomato juice is obtained by mixing and pulping green tomatoes with water in a mass ratio of (0.8-1.2):(1.8-2.2), and then sterilizing. Preferably, the sterilization condition is 110-125° C. for 10-20 min.

8. The method according to claim 6, characterized in that The culture conditions in step (1) are culturing at 35-38° C. for 10-12 hours; and the culture conditions in step (2) are culturing at 35-38° C. for 4-6 hours.

9. A fermented green tomato product, characterized in that: The fermented green tomato product is prepared by the method of claims 1 to 8; Preferably, the fermented green tomato product includes but is not limited to green tomato slices, green tomato pieces, and green tomato juice.

10. Use of the method according to claims 1 to 8 or the fermented green tomato product according to claim 9 in the preparation of green tomato products; Preferably, the green tomato products include but are not limited to green tomato drinks, green tomato sauce, and canned green tomatoes.

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