Method for preserving fresh-cut potatoes

Abstract

The invention provides a method for preserving fresh-cut potatoes, and belongs to the technical field of potato preservation. The fresh-keeping method of the fresh-cut potatoes comprises the following steps: sterilizing the cut potatoes with hot water, fishing out, mixing with water, salt and lactic acid bacteria, and fermenting at 30-40 DEG C for 12-60 hours. The lactic acid bacteria are used for fermentation and preservation of fresh-cut potato products, browning of the fresh-cut potatoes can be remarkably delayed, quality deterioration of the fresh-cut potatoes is inhibited, and the lactic acid bacteria have good application prospects in storage and preservation of the fresh-cut potatoes.

Description

Technical Field

[0001] The present invention belongs to the technical field of potato preservation, and particularly relates to a method for preserving fresh-cut potatoes. Background Art

[0002] Potato (Solanum tuberosum L.) is one of the four major food crops in the world. Because of its rich and comprehensive nutritional components, it has the reputation of "underground apple". At present, the main potato processing products include whole powder, frozen French fries, snack foods, and reprocessed products (vermicelli, noodles and sheets, etc.) with potato starch as the raw material. In order to solve many problems such as storage, transportation and processing after high potato yield, and improve the utilization rate and high added value of potato foods, scientific research personnel have done a lot of work. However, at present, potato consumption is still mainly fresh food (accounting for 80% of the total output).

[0003] With the improvement of people's living standards, the acceleration of the pace of life and the enhancement of health awareness, the market share of lightly processed foods (fresh-cut foods) is constantly expanding. Fresh-cut potato products stand out among many fresh-cut foods because of their rich nutrition and in line with the eating habits of most consumers. Fresh-cut potatoes almost completely retain the original quality and flavor of potato tubers, and have the advantages of freshness, hygiene, convenient eating, saving cooking time and easy transportation. However, fresh-cut potatoes are prone to many problems such as tissue browning, microbial over-standard, nutrient loss, and decline in cooking quality during storage and transportation. Summary of the Invention

[0004] In view of this, one of the purposes of the present invention is to provide an application of lactic acid bacteria starter in the preservation of fresh-cut potatoes. The co-fermentation of fresh-cut potatoes by Lactiplantibacillus plantarum ZYN-02 and Lactobacillus rhamnosus ZYN-01 can further delay the browning of fresh-cut potatoes and inhibit the deterioration of the quality of fresh-cut potatoes, and has good application prospects in the fresh-cut potato ready-to-eat vegetables.

[0005] Another purpose of the present invention is to provide a method for preserving fresh-cut potatoes, which can significantly delay the browning of fresh-cut potatoes and inhibit the deterioration of the quality of fresh-cut potatoes.

[0006] In order to achieve the above-mentioned invention purposes, the present invention provides the following technical solutions:

[0007] The present invention provides an application of lactic acid bacteria starter in the preservation of fresh-cut potatoes, and the lactic acid bacteria starter includes Lactiplantibacillus plantarum ZYN-02 and Lactobacillus rhamnosus ZYN-01.

[0008] Preferably, the lactic acid bacteria starter is composed of Lactiplantibacillus plantarum ZYN-02 bacterial liquid and Lactobacillus rhamnosus ZYN-01 bacterial liquid.

[0009] Preferably, the volume ratio of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid to the Lactobacillus rhamnosus ZYN-01 bacterial liquid is (2.0 - 4.0):(1.0 - 2.0); the viable bacteria concentration of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is 7.5 - 8.0 log10 CFU / mL, and the viable bacteria concentration of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is 7.5 - 8.0 log10 CFU / mL.

[0010] The present invention also provides a method for preserving fresh-cut potatoes, comprising the following steps: subjecting the cut potatoes to hot water sterilization, fishing them out and mixing them with water, salt and lactic acid bacteria, and fermenting at 30 - 40 °C for 12 - 60 h.

[0011] Preferably, the lactic acid bacteria include the Lactiplantibacillus plantarum ZYN-02 bacterial liquid and the Lactobacillus rhamnosus ZYN-01 bacterial liquid.

[0012] Preferably, the volume ratio of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid to the Lactobacillus rhamnosus ZYN-01 bacterial liquid is (2.0 - 4.0):(1.0 - 2.0); the viable bacteria concentration of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is 7.5 - 8.0 log10 CFU / mL, and the viable bacteria concentration of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is 7.5 - 8.0 log10 CFU / mL.

[0013] Preferably, the method of hot water sterilization is sterilization at 90 - 100 °C for 1 min.

[0014] Preferably, the mass ratio of the cut potatoes to the salt is (30 - 70):(1 - 5).

[0015] Preferably, the mass-to-volume ratio of the cut potatoes to the lactic acid bacteria is (30 - 70) g:(1 - 5) mL.

[0016] Preferably, the mass-to-volume ratio of the cut potatoes to the water is 10 - 20 g:250 - 350 mL.

[0017] The beneficial effects of the present invention:

[0018] The lactic acid bacteria fermenting agent provided by the present invention combines Lactiplantibacillus plantarum ZYN-02 and Lactobacillus rhamnosus ZYN-01. Compared with single-strain fermentation, the viable lactic acid bacteria count of the composite lactic acid bacteria fermenting agent is significantly increased, with a significant difference (p < 0.05), indicating that the mixed fermentation of the two has a good synergistic effect on fresh-cut potatoes. At the same time, the synergistic fermentation of the two can significantly delay the browning of fresh-cut potatoes and inhibit the deterioration of the quality of fresh-cut potatoes, showing good application prospects in the storage and preservation of fresh-cut potatoes.

[0019] The method for preserving fresh-cut potatoes provided by the present invention uses lactic acid bacteria for the fermentation and preservation of fresh-cut potato products, which can significantly delay the browning of fresh-cut potatoes and inhibit the deterioration of the quality of fresh-cut potatoes, and has good application prospects in the storage and preservation of fresh-cut potatoes. Description of the Drawings

[0020] Figure 1 It is the free radical scavenging ability of fresh-cut potato shreds before and after fermentation. If the letters on the columns are different, it indicates significant differences, p < 0.05;

[0021] Figure 2 It is the viable count of lactic acid bacteria, hardness, total acid content (calculated as lactic acid), and sensory evaluation results of fresh-cut potato shreds fermented with different combinations of lactic acid bacteria dosages. Among them, A is the viable count of lactic acid bacteria and sensory evaluation results, B is the total acid content and hardness results. If the letters on the columns are different, it indicates significant differences, p < 0.05;

[0022] Figure 3 It is the relative abundance results of natural fermented potato species. Among them, A is the relative abundance of species at the phylum level, and B is the relative abundance of species at the genus level;

[0023] Figure 4 It is the change results of PPO, POD, PAL activities and MDA content of fresh-cut potato shreds before and after lactic acid bacteria fermentation. Among them, A is the PAL activity and PPO activity results, B is the POD activity and MDA content results. If the letters on the columns are different, it indicates significant differences, p < 0.05;

[0024] Figure 5 It is the change of L*, a*, b*, and BI values of fresh-cut potato shreds fermented by lactic acid bacteria compared with the untreated ones. Among them, A is the L* result, B is the a* result, C is the b* result, and D is the BI value result. If the letters on the columns are different, it indicates significant differences, p < 0.05. Detailed Embodiments

[0025] The present invention provides an application of a lactic acid bacteria starter in the preservation of fresh-cut potatoes. The lactic acid bacteria starter includes Lactiplantibacillus plantarum ZYN-02 and Lactobacillus rhamnosus ZYN-01.

[0026] In the present invention, the Lactiplantibacillus plantarum ZYN-02 is taxonomically named Lactiplantibacillus plantarum, deposited at the Guangdong Microbial Culture Collection Center, located on the 5th floor of the Institute of Microbiology, Guangdong Academy of Sciences, No. 59, Yard 100, Middle Xianlie Road, Guangzhou, with the deposit number GDMCC No: 64480 and the deposit date of April 1, 2024. The Lacticaseibacillus rhamnosus ZYN-01 is taxonomically named Lacticaseibacillus rhamnosus, deposited at the Guangdong Microbial Culture Collection Center, located on the 5th floor of the Institute of Microbiology, Guangdong Academy of Sciences, No. 59, Yard 100, Middle Xianlie Road, Guangzhou, with the deposit number GDMCC No: 64479 and the deposit date of April 1, 2024.

[0027] In the present invention, the lactic acid bacteria starter preferably consists of Lactiplantibacillus plantarum ZYN-02 bacterial liquid and Lactobacillus rhamnosus ZYN-01 bacterial liquid; the volume ratio of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid to the Lactobacillus rhamnosus ZYN-01 bacterial liquid is preferably (2.0 - 4.0):(1.0 - 2.0), and in some embodiments, it can be 2:1, 2:2, 3:1, 3:2 or 4:1. In the present invention, the viable bacteria concentration of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is preferably 7.5 - 8.0 log10 CFU / mL, more preferably 7.7 - 7.9 log10 CFU / mL, and the viable bacteria concentration of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is preferably 7.5 - 8.0 log10 CFU / mL, more preferably 7.7 - 7.9 log10 CFU / mL. In the present invention, the preparation method of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is preferably to inoculate Lactiplantibacillus plantarum ZYN-02 into MRS liquid medium and culture it at 37°C, perform viable bacteria counting on the bacterial liquid according to the method of GB 4789.35-2016 "National Food Safety Standard Food Microbiology Examination - Lactic Acid Bacteria Examination", and adjust the cell concentration to 7.5 - 8.0 log10 CFU / mL to obtain the Lactiplantibacillus plantarum ZYN-02 bacterial liquid. The MRS liquid medium consists of the following components at the following concentrations: peptone 10.0 g, beef extract 10.0 g, yeast extract 5 g, diammonium hydrogen citrate 2.0 g, glucose 20.0 g, sodium acetate 5.0 g, Tween 80 1.0 mL, dipotassium hydrogen phosphate 2.0 g, magnesium sulfate 0.58 g, manganese sulfate 0.25 g, made up to 1000 mL with distilled water, with a pH value of 6.2 - 6.6, and sterilized at 121°C for 30 min. The preparation method of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is preferably to inoculate Lactobacillus rhamnosus ZYN-01 into the above-mentioned MRS liquid medium and culture it at 37°C, perform viable bacteria counting on the bacterial liquid according to the method of GB 4789.35-2016 "National Food Safety Standard Food Microbiology Examination - Lactic Acid Bacteria Examination", and adjust the cell concentration to 7.5 - 8.0 log10 CFU / mL to obtain the Lactobacillus rhamnosus ZYN-01 bacterial liquid.

[0028] The present invention also provides a method for preserving fresh-cut potatoes, which includes the following steps: subjecting the cut potatoes to hot water sterilization, fishing them out and mixing them with water, salt and lactic acid bacteria, and fermenting at 30 - 40°C for 12 - 60 h.

[0029] The present invention solves the problem that fresh-cut potatoes are prone to browning by subjecting fresh-cut potatoes to secondary processing through a microbial fermentation method. The fresh-cut potatoes are fermented by lactic acid bacteria, and natural antibacterial agents produced by the metabolites of lactic acid bacteria are used to extend the shelf life and enhance food safety. The lactic acid bacteria fermentation can not only improve the nutritional quality of potatoes and control the generation of harmful microorganisms, but also the antioxidant substances produced after microbial fermentation will effectively delay and control the occurrence of browning.

[0030] In the fresh-cut potato preservation method of the present invention, the lactic acid bacteria refer to the lactic acid bacteria present on the fermented potatoes after the natural fermentation of fresh-cut potatoes, and there are various types. In the present invention, the lactic acid bacteria preferably include Lactiplantibacillus plantarum ZYN-02 bacterial liquid and Lactobacillus rhamnosus ZYN-01 bacterial liquid; the volume ratio of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid to the Lactobacillus rhamnosus ZYN-01 bacterial liquid is preferably (2.0 - 4.0):(1.0 - 2.0), and in some embodiments, it can be 2:1, 2:2, 3:1, 3:2 or 4:1. In the present invention, the viable bacteria concentration of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is preferably 7.5 - 8.0 log10 CFU / mL, more preferably 7.7 - 7.9 log10 CFU / mL, and the viable bacteria concentration of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is preferably 7.5 - 8.0 log10 CFU / mL, more preferably 7.7 - 7.9 log10 CFU / mL. The preparation methods of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid and the Lactobacillus rhamnosus ZYN-01 bacterial liquid are the same as above and will not be elaborated here.

[0031] In the present invention, the method of hot water sterilization is preferably sterilization at 90 - 100°C for 1 min. In some embodiments, the sterilization temperature can be 90°C, 92°C, 94°C, 96°C, 98°C or 100°C. In the present invention, the mass ratio of cut potatoes to salt is preferably (30 - 70):(1 - 5). In some embodiments, the mass ratio of cut potatoes to salt can be 30:1, 40:1, 50:1, 60:1, 70:1, 30:2, 40:2, 50:2, 70:2, 30:3, 40:3, 50:3, 60:3, 70:3, 30:4, 50:4, 70:4, 30:5, 40:5 or 70:5. In the present invention, the mass - volume ratio of cut potatoes to lactic acid bacteria is preferably (30 - 70) g:(1 - 5) mL. In some embodiments, the mass - volume ratio of cut potatoes to lactic acid bacteria can be 30 g:1 mL, 40 g:1 mL, 50 g:1 mL, 60 g:1 mL, 70 g:1 mL, 30 g:2 mL, 40 g:2 mL, 50 g:2 mL, 70 g:2 mL, 30 g:3 mL, 40 g:3 mL, 50 g:3 mL, 60 g:3 mL, 70 g:3 mL, 30 g:4 mL, 50 g:4 mL, 70 g:4 mL, 30 g:5 mL, 40 g:5 mL or 70 g:5 mL. In the present invention, the mass - volume ratio of cut potatoes to water is preferably 10 - 20 g:250 - 350 mL, more preferably 14 - 18 g:280 - 320 mL.

[0032] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0033] In the following embodiments, unless otherwise specified, all are conventional methods.

[0034] In the following embodiments, the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0035] The MRS liquid medium in the following embodiments is made of components with the following concentrations: peptone 10.0 g, beef extract 10.0 g, yeast extract 5 g, diammonium hydrogen citrate 2.0 g, glucose 20.0 g, sodium acetate 5.0 g, Tween 80 1.0 mL, dipotassium hydrogen phosphate 2.0 g, magnesium sulfate 0.58 g, manganese sulfate 0.25 g. The volume is made up to 1000 mL with distilled water, the pH value is 6.4, and it is sterilized at 121°C for 30 min.

[0036] Example 1

[0037] A lactic acid bacteria starter culture is composed of Lactiplantibacillus plantarum ZYN-02 bacterial liquid and Lactobacillus rhamnosus ZYN-01 bacterial liquid with a volume ratio of 2:1. The viable bacteria concentration of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is 7.8 log10 CFU / mL, and the viable bacteria concentration of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is 7.8 log10 CFU / mL.

[0038] The preparation method of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid is to inoculate Lactiplantibacillus plantarum ZYN-02 into MRS liquid medium and culture it at 37°C. According to the method of GB 4789.35-2016 "National Food Safety Standard Microbiological Examination of Foods - Examination of Lactic Acid Bacteria", the viable bacteria count of the bacterial liquid is carried out, and the cell concentration is adjusted to 7.8 log10 CFU / mL to obtain the Lactiplantibacillus plantarum ZYN-02 bacterial liquid.

[0039] The preparation method of the Lactobacillus rhamnosus ZYN-01 bacterial liquid is to inoculate Lactobacillus rhamnosus ZYN-01 into the above-mentioned MRS liquid medium and culture it at 37°C. According to the method of GB 4789.35-2016 "National Food Safety Standard Microbiological Examination of Foods - Examination of Lactic Acid Bacteria", the viable bacteria count of the bacterial liquid is carried out, and the cell concentration is adjusted to 7.8 log10 CFU / mL to obtain the Lactobacillus rhamnosus ZYN-01 bacterial liquid.

[0040] Example 2

[0041] The lactic acid bacteria starter culture obtained in Example 1 is used for the preservation of fresh-cut potatoes. The specific steps are as follows: Peel and shred fresh potatoes (purchased from Qiqihar City, Heilongjiang Province). Sterilize the shredded potatoes in 100°C hot water for 1 min. After fishing out, mix them with water, salt and the lactic acid bacteria starter culture obtained in Example 1. The mass ratio of shredded potatoes to salt is 30:1, the mass-volume ratio of shredded potatoes to the lactic acid bacteria starter culture obtained in Example 1 is 30 g:1 mL, and the mass-volume ratio of shredded potatoes to water is 15 g:300 mL. Ferment at 40°C on a shaker at 100 r / min for 12 h.

[0042] The effects of fresh-cut potato strips on DPPH free radicals, ABTS free radicals, OH free radicals and Fe 2+ are measured before and after fermentation respectively. The specific measurement method is as follows:

[0043] (1) Determination of DPPH free radical scavenging activity

[0044] Refer to the method of Rozzello et al. to determine the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability of lactic acid bacteria. Take 2 mL of DPPH anhydrous ethanol solution (0.2 mmol / L) and add 1 mL of FS sample. After mixing, react for 30 min under dark conditions. After centrifugation (4 °C, 8000×g, 10 min), take the supernatant and measure the absorbance at 517 nm. Use 1 mg / mL L-ascorbic acid as the positive control. Calculate using the following formula.

[0045] Scavening rate(%)=[1-(As / Ab)]×100

[0046] Where: As, the absorbance of the mixture of DPPH and the sample, that is, the absorbance value of the sample group;

[0047] Ab, the absorbance of the mixture of DPPH and anhydrous ethanol, that is, the absorbance value of the blank group.

[0048] (2) Determination of ABTS cation radical scavenging rate

[0049] Refer to the method of Yang et al. The specific method is as follows: Mix the ABTS + solution (7 mmol / L) and potassium sulfate solution (2.45 mmol / L) in equal volumes, and react at 25 °C in the dark for 16 h. Adjust the absorbance of the mixture with phosphate buffer (Phosphate-Buffered Saline, PBS) at 734 nm to (0.70 ± 0.01), then mix it with the FS sample in equal volumes, and store at 25 °C for 6 min. Measure the absorbance value at 734 nm. Deionized water and the mixture (ABTS + solution (7 mmol / L) and potassium sulfate solution (2.45 mmol / L) in equal volumes) are used as blank controls. Use 1 mg / mL L-ascorbic acid as the positive control, and the ABTS + radical scavenging ability is calculated as follows:

[0050] Scavening rate(%)=(Ac - As) / Ac×100

[0051] Where: Ac, the absorbance value of the ABTS + working solution, that is, the absorbance value of the blank group;

[0052] As, the absorbance value of the sample and the ABTS + working solution, that is, the absorbance value of the sample group.

[0053] (3) Determination of hydroxyl radical scavenging activity

[0054] The hydroxyl radical scavenging rate of the strains was determined according to the method of Zhang et al. In a test tube, 1 mL of FeSO4 solution (5 mmol / L), 1 mL of salicylic acid-ethanol solution (5 mmol / L), and 1 mL of H2O2 (3 mmol / L) were added in sequence. After mixing, 1 mL of the FS sample of each strain was added, and deionized water was added to make up the volume to 10 mL. The sample was placed in a water bath at 37 °C for 30 min. After centrifugation (4 °C, 5000×g, 20 min), the absorbance of the supernatant was measured at 510 nm, and 1 mg / mL L-ascorbic acid was used as the positive control. The calculation formula for the hydroxyl radical scavenging activity is as follows.

[0055] Scaveningrate(%)=(Ac-As) / Ac×100

[0056] Where: Ac, the absorbance value of the blank control with deionized water replacing the sample, that is, the absorbance value of the blank group;

[0057] As, the absorbance value after the reaction of the sample solution, that is, the absorbance value of the sample group.

[0058] (4)Fe 2+ Reducing power determination

[0059] According to the method of BarlaF et al. and modified. In the FS sample, 2.5 mL of potassium ferricyanide (1% mass fraction) and 2.5 mL of phosphate buffer solution (0.2 mol / L, pH 6.6) were added. After shaking evenly, it was placed in a water bath at 50 °C for 20 min. After rapid cooling, 2.5 mL of trichloroacetic acid solution (10% mass fraction) was added, and after centrifugation (4 °C, 3000×g, 10 min), 2.5 mL of the supernatant was taken, 2.5 mL of deionized water, 0.5 mL of ferric chloride solution (0.1% mass fraction), and 1 mL of sterile ddH2O were added, vortexed and mixed evenly, and left to stand at room temperature for 10 min. The absorbance was measured at a wavelength of 700 nm, and the Fe 2+ reducing ability of the strain was calculated according to the following formula.

[0060] Reducing ability%=(A 样品 -A 参比 ) / A 参比 ×100%

[0061] Wherein, A 样品 , the absorbance measured for the sample; A 参比 , ultrapure deionized water was used instead of the sample.

[0062] The results are as Figure 1 shown. After fermentation with the lactic acid bacteria starter obtained in Example 1, the DPPH radical scavenging rate of fresh-cut potato strips was 89.54% (IC 50The value was 0.099 mg / mL Vc equivalent), an increase of 12.44% compared with that before fermentation. After fermentation, the ABTS free radical scavenging ability reached 82.54% (IC 50 The value was 0.129 mg / mL Vc equivalent). Compared with that before fermentation, the ABTS free radical of lactic acid bacteria increased by 12.04% after fermentation. After fermentation, the OH free radical scavenging ability reached 62.54% (IC 50 The value was 0.147 mg / mL Vc equivalent). After fermentation, Fe 2+ The chelation rate had the largest increase. After fermentation, the Fe 2+ chelation rate was 48.53%, a 20% increase compared with that before fermentation.

[0063] Comparative Example 1

[0064] A lactic acid bacteria fermenting agent, which is different from Example 1 in that it does not contain the liquid of Lactobacillus rhamnosus ZYN-01, and only contains the liquid of Lactiplantibacillus plantarum ZYN-02, and the rest are the same as in Example 1. The total volume of this lactic acid bacteria fermenting agent is the same as that of the lactic acid bacteria fermenting agent in Example 1.

[0065] Comparative Example 2

[0066] A lactic acid bacteria fermenting agent, which is different from Example 1 in that it does not contain the liquid of Lactiplantibacillus plantarum ZYN-02, and only contains the liquid of Lactobacillus rhamnosus ZYN-01, and the rest are the same as in Example 1. The total volume of this lactic acid bacteria fermenting agent is the same as that of the lactic acid bacteria fermenting agent in Example 1.

[0067] Example 3

[0068] A lactic acid bacteria fermenting agent, which is different from Example 1 in that the volume ratio of the liquid of Lactiplantibacillus plantarum ZYN-02 to the liquid of Lactobacillus rhamnosus ZYN-01 is 1:1, and the rest are the same as in Example 1.

[0069] Comparative Example 3

[0070] A lactic acid bacteria fermenting agent, which is different from Example 1 in that the volume ratio of the liquid of Lactiplantibacillus plantarum ZYN-02 to the liquid of Lactobacillus rhamnosus ZYN-01 is 1:2, and the rest are the same as in Example 1.

[0071] Example 4

[0072] A method for preserving fresh-cut potatoes, the steps are as follows: Peel and shred fresh potatoes (purchased from Qiqihar City, Heilongjiang Province), sterilize the shredded potatoes in 95°C hot water for 1 min, fish them out and mix with water, pickled vegetable salt and lactic acid bacteria. The mass ratio of shredded potatoes to salt is 40:1, the mass-volume ratio of shredded potatoes to lactic acid bacteria is 40 g:1 mL, and the mass-volume ratio of shredded potatoes to water is 20 g:350 mL. Ferment at 35°C on a shaker at 100 r / min for 25 h under airtight conditions.

[0073] Example 5

[0074] A method for preserving fresh-cut potatoes, the steps are as follows: Peel and shred fresh potatoes (purchased from Qiqihar City, Heilongjiang Province), sterilize the shredded potatoes in 90°C hot water for 1 min, fish them out and mix with water, pickled vegetable salt and lactic acid bacteria. The mass ratio of shredded potatoes to salt is 70:5, the mass-volume ratio of shredded potatoes to lactic acid bacteria is 70 g:5 mL, and the mass-volume ratio of shredded potatoes to water is 15 g:300 mL. Ferment at 30°C on a shaker at 100 r / min for 50 h under airtight conditions.

[0075] Example 6

[0076] Use the lactic acid bacteria starters obtained from Example 1 (2:1), Example 3 (1:1), Comparative Example 1 (1:0), Comparative Example 2 (0:1) and Comparative Example 3 (1:2) respectively to replace the lactic acid bacteria in Example 4 to obtain fresh-cut potato shred products fermented with different lactic acid bacteria.

[0077] Detect the viable lactic acid bacteria count, hardness, total acid content (calculated as lactic acid) and sensory evaluation of fresh-cut potato shred products fermented with different lactic acid bacteria. Each index is repeated three times. Among them, the viable lactic acid bacteria count is determined by the method of GB4789.35-2016, the hardness of fresh-cut potato shreds is measured by a TA-XTplus texture analyzer, the total acid is determined by the method of GB12456-2021, and the sensory evaluation criteria are shown in Table 1.

[0078] Table 1 Sensory evaluation criteria

[0079]

[0080] The results are as Figure 2As shown, compared with single-strain fermentation, the viable count of lactic acid bacteria after compound-strain fermentation has increased significantly, indicating that there is not only a symbiotic relationship between Lactiplantibacillus plantarum and Lactobacillus rhamnosus, but also that co-cultivation can well promote the growth of each other and play a good synergistic role in the fermentation of fresh-cut potato shreds. Especially when the volume ratio of the Lactiplantibacillus plantarum ZYN-02 bacterial liquid to the Lactobacillus rhamnosus ZYN-01 bacterial liquid is 2:1, the maximum hardness is 4901.77 g, the maximum viable count of lactic acid bacteria is 11.56 log10 CFU / mL, and the highest sensory evaluation score is 92.08 points.

[0081] Example 7

[0082] The types of lactic acid bacteria applicable in the fresh-cut potato preservation method of the present invention:

[0083] After the samples of naturally fermented potato shreds (purchased from Longjiang County, Heilongjiang Province, China) (six samples) were quickly frozen in liquid nitrogen, they were sent to Majorbio Bio-Pharm Technology Co., Ltd. (Shanghai, China) for bacterial 16S rDNA sequencing. The DNA of the samples was electrophoretically detected using 1% agarose gel. Then, Polymerase Chain Reaction (PCR) amplification was performed using the bacterial 16S rRNA primer pairs 27F and 338R, and the sequences were 27F: 5'-AGAGTTTGATCCTGGCTCAG-3' (SEQ ID NO.1) and 338R: 5-TGCTGCCTCCCGTAGGAGT-3 (SEQ ID NO.2). Subsequently, the PCR products were recovered by cutting the gel using the AxyPrep DNA Gel Extraction Kit (Shanghai Biosciences Co., Ltd., Shanghai, China), and subsequent detection was carried out on the PE300 sequencing platform. The α-diversity and β-diversity of naturally fermented potatoes were analyzed according to the sequencing results, and the results were as Figure 3 .

[0084] The microbial diversity of naturally fermented potatoes was analyzed by 16S rDNA high-throughput sequencing, and its main fermentation strains were found. A total of 8 phyla, 10 classes, 21 orders, 38 families, 51 genera, and 58 species of annotation information were identified in naturally fermented potatoes.

[0085] Among the annotation information at the phylum level, the relative abundance of Firmicutes in each sample ranged from 78.4% to 86.6%, with an average of 83.3%, ranking first in relative abundance. The relative abundance of Proteobacteria in each sample ranged from 13.0% to 21.1%, with an average of 16.3%, ranking second in relative abundance. The relative abundances of other phylum-level species were all less than 0.4%.

[0086] In the annotation information at the genus level, the relative abundance of Lactobacillus in each sample ranges from 37.5% to 45.2%, with an average of 42.8%, ranking first in relative abundance and showing an obvious dominant flora. The relative abundance of Leuconostoc in each sample ranges from 28.6% to 39.3%, with an average of 35.1%, ranking second in relative abundance. The relative abundances of other bacterial genera are all less than 5%. It indicates that the microorganisms of the genus Lactobacillus can be used for the preservation of fresh-cut potatoes in the present invention.

[0087] Example 8

[0088] Use the lactic acid bacteria starter obtained in Example 1 for the preservation of fresh-cut potatoes. The specific steps are as follows: Peel and shred fresh potatoes (purchased from Qiqihar City, Heilongjiang Province), sterilize the shredded potatoes in 100°C hot water for 1 min, take them out and mix them with water, salt and the lactic acid bacteria starter obtained in Example 1. The mass ratio of shredded potatoes to salt is 70:3, the mass-volume ratio of shredded potatoes to the lactic acid bacteria starter obtained in Example 1 is 70 g:3 mL, and the mass-volume ratio of shredded potatoes to water is 15 g:300 mL. Ferment at 38°C on a shaker at 100 r / min for 30 h under airtight conditions (denoted as the composite fermentation group).

[0089] Control group (untreated group): The difference from the above scheme is only that the lactic acid bacteria starter obtained in Example 1 is not added, and the rest are the same as the above scheme.

[0090] After treating fresh-cut potato strips by the above method, immediately analyze the effects on browning-related enzymes in the untreated group and the composite fermentation group. The specific method is as follows:

[0091] Determination method of browning-related enzymes:

[0092] Take the fermented fresh-cut potato strips for ice bath homogenization, centrifuge at 4°C and 12,000 rpm for 15 min, and take the supernatant. Measure according to the specific steps of the phenylalanine ammonia-lyase (PAL) kit, polyphenol oxidase (PPO) kit, peroxidase (POD) kit and malondialdehyde (MDA) kit (Gries, Suzhou, China).

[0093] The results are as Figure 4 shown. PAL is the key synthetic enzyme for plants to synthesize phenolic compounds through the phenylpropanoid pathway. When plants are physically damaged, it will promote the transcription of PAL and increase the PAL activity. At the end of fermentation, the PAL enzyme activity of lactic acid bacteria fermentation (26.89 U·g -1 ) is increased by 16.20 U·g compared with the untreated group (10.69 U·g -1 ) -1. PPO is a phenolic compound oxidase. Under its catalytic action, phenolic substances can be oxidized to form o-quinone and its polymer melanin, which in turn causes the color of raw materials to deepen or darken. It is the main reason for the browning of fresh fruits and vegetables. At the end of fermentation, the PPO activity (0.48 U·g -1 ) in the composite lactic acid bacteria fermentation group was significantly lower than that in the untreated group (1.46 U·g -1 ). POD is a protective enzyme. It can catalyze the oxidation and polymerization of phenols and flavonoids to form brown substances, which can not only cause browning, but also oxidize glutathione and ascorbic acid in fruit and vegetable tissues, promote the synthesis of ethylene, accelerate senescence, and affect the flavor and nutrition of fruits. The POD activity in the lactic acid bacteria-fermented fresh-cut potato strips group was 3.89 U·g -1 , which was significantly lower than that in the untreated group (6.09 U·g -1 ). MDA is a reactive compound produced during lipid peroxidation, which is a process that occurs when lipids in food are exposed to oxygen. MDA is a marker of oxidative stress and affects the texture, color, and flavor of products. Excessive content of MDA will lead to a decline in food quality and shorten the product shelf life. Compared with the untreated group, the MDA content in the lactic acid bacteria-fermented fresh-cut potato strips was 1.15 μmol·kg -1 , which was significantly lower than the MDA content in the untreated group (1.87 μmol·kg -1 ). It can be seen that lactic acid bacteria fermentation can effectively control the production of MDA. After potato cutting, the cells will be irreversibly damaged, and the MDA content will gradually accumulate over time, leading to the aging of potato tissues and a decline in quality. Lactic acid bacteria fermentation can effectively shield the occurrence of peroxidation reactions and delay the accumulation of MDA.

[0094] Color change is the most intuitive indicator of the browning of fresh-cut potatoes. To study the effect of fermentation on the browning degree of fresh-cut potato strips before and after fermentation, a color difference meter was used to measure the color of the surface of fermented fresh-cut potato strips to obtain the anti-browning effect of potato strips before and after fermentation. After treating fresh-cut potato strips using the above method, the effects of the untreated and composite fermentation groups on the color index of potato strips were immediately analyzed. The measured value of fresh-cut potato strips was used as the initial value. The specific method is as follows:

[0095] Color index measurement method:

[0096] Use a color difference meter to measure the color of the surface of potato strips. L* represents the brightness of the sample color, and the larger the value, the brighter it is. The a* value represents the distribution of red and green in the color. The larger the a* value, the closer it is to red, and vice versa, closer to green. The b* value represents the distribution of blue and yellow. The larger the b* value, the closer it is to yellow, and vice versa, closer to blue. Calculate the browning index (BI).

[0097]

[0098] The results are as follows Figure 5 shown. Compared with the fresh-cut potato strips without fermentation, the L* values of the two groups of fresh-cut potato strips decreased to varying degrees. Among them, the decrease amplitude of the L* value in the fermentation group was 20.69 compared with the initial brightness (87.39) of the fresh-cut potato strips, which was significantly lower than that of the untreated group (28.95). The a* values of the fresh-cut potato strips fermented by lactic acid bacteria and the control group increased to varying degrees compared with the initial values. After the fermentation ended, the a* value of the lactic acid bacteria fermentation group increased by 1.60 compared with the initial fresh-cut potato strips, which was -1.34, and the a* value of the untreated group increased by 2.12. It can be seen that the a* value of the lactic acid bacteria fermentation group was significantly lower than that of the untreated group. This may be because when the potato was mechanically damaged, the rate of the enzymatic browning reaction was accelerated, and as the storage time prolonged, the tissue cells of the potato gradually aged, the degree of browning deepened, the surface of the potato gradually evolved into reddish-brown, and the a* value showed an increasing trend. For the change of the b* value, the b* value increased slightly after lactic acid bacteria fermentation. The b* value increased by 13.80% after lactic acid bacteria fermentation, and the b* value of the untreated group decreased by 27.71%. It can be seen that the effect of lactic acid bacteria fermentation on the yellow-blue hue of potatoes is positive, and it can significantly delay the deepening of the yellow color of fresh-cut potatoes. Next, the BI value can directly reflect the degree of browning of the fresh-cut potato strips. The larger the BI value, the higher the degree of browning. As time increased, the BI value showed an upward trend. The initial BI value of the fresh-cut potato strips was 12.32, and the browning index (20.89) of the lactic acid bacteria fermentation was significantly lower than that of the untreated group (28.75) (p < 0.05). It can be seen that the treatment with lactic acid bacteria has the effect of inhibiting the browning of fresh-cut potatoes.

[0099] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Application of a lactic acid bacteria starter in fresh-cut potato preservation, characterized in that, The lactic acid bacteria starter culture includes Lactiplantibacillus plantarum ZYN-02 and Lactobacillus rhamnosus ZYN-01.

2. The application according to claim 1, wherein The lactic acid bacteria starter culture is composed of the bacterial liquid of Lactiplantibacillus plantarum ZYN-02 and the bacterial liquid of Lactobacillus rhamnosus ZYN-01.

3. The application according to claim 2, wherein The volume ratio of the bacterial liquid of Lactiplantibacillus plantarum ZYN-02 to the bacterial liquid of Lactobacillus rhamnosus ZYN-01 is (2.0-4.0):(1.0-2.0); the viable bacteria concentration of the bacterial liquid of Lactiplantibacillus plantarum ZYN-02 is 7.5-8.0 log10 CFU / mL, and the viable bacteria concentration of the bacterial liquid of Lactobacillus rhamnosus ZYN-01 is 7.5-8.0 log10 CFU / mL.

4. A method for preserving fresh-cut potatoes, characterized in that, It includes the following steps: subject the cut potatoes to hot water sterilization, fish them out and then mix them with water, salt and lactic acid bacteria, and ferment at 30-40 °C for 12-60 h.

5. The method according to claim 4, characterized in that, The lactic acid bacteria include the bacterial liquid of Lactiplantibacillus plantarum ZYN-02 and the bacterial liquid of Lactobacillus rhamnosus ZYN-01.

6. The method according to claim 5, characterized in that, The volume ratio of the bacterial liquid of Lactiplantibacillus plantarum ZYN-02 to the bacterial liquid of Lactobacillus rhamnosus ZYN-01 is (2.0-4.0):(1.0-2.0); the viable bacteria concentration of the bacterial liquid of Lactiplantibacillus plantarum ZYN-02 is 7.5-8.0 log10 CFU / mL, and the viable bacteria concentration of the bacterial liquid of Lactobacillus rhamnosus ZYN-01 is 7.5-8.0 log10 CFU / mL.

7. The method according to claim 4, characterized in that The method of hot water sterilization is sterilization at 90-100 °C for 1 min.

8. The method according to claim 4, characterized in that The mass ratio of the cut potatoes to salt is (30-70):(1-5).

9. The method according to claim 4, characterized in that The mass-volume ratio of the cut potatoes to lactic acid bacteria is (30-70) g:(1-5) mL.

10. The method according to claim 4, wherein The mass-volume ratio of the cut potatoes to water is 10-20 g:250-350 mL.

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