A treatment method for preventing the browning of glutinous yam after peeling

Abstract

The present invention provides a treatment method for preventing the browning of peeled waxy yams, which relates to the technical field of yam preservation. The treatment method is to soak the yams in ice water before peeling, and then soak them with a bleaching agent composed of glutinous rice fermentation solution, zinc acetate, citric acid, white vinegar, and D-isoascorbic acid sodium. After that, it is treated with a protective solution prepared from sterile water, roselle polyphenols, calcium chloride, chitosan, konjac powder, and sodium alginate. After the treatment is completed, it is stored at normal temperature or low temperature. The present invention overcomes the deficiencies of the prior art, effectively prevents the browning of fresh-cut waxy yams while reducing the loss of starch content, ensures the taste of waxy yams, and enhances the value of fresh-cut storage of waxy yams.

Description

Technical Field

[0001] The present invention relates to the technical field of yam preservation, and particularly relates to a treatment method for preventing browning of glutinous yam after peeling. Background Art

[0002] Yam is a vegetable with both medicinal and edible properties. It is rich in nutrients and has a good market. However, yam is generally harvested once a year. In order to meet the annual market supply of yam, most of the yams are stored and preserved after being harvested in the current season. The existing yam storage and preservation methods mainly involve storing the whole yam in cold storage. However, due to the relatively long length of the whole yam, it is very easy to break during storage, transportation, or even harvesting. And the broken yam will deteriorate directly during storage, seriously affecting the quality of the yam. Therefore, at present, a part of the yam is peeled and stored as fresh-cut pieces.

[0003] After yam is cut into fresh pieces, two types of browning, namely enzymatic browning and non-enzymatic browning, will occur on its surface, which greatly affects the sensory quality of fresh-cut yam. On this basis, the anti-browning treatment of fresh-cut yam is crucial. The existing anti-browning methods mainly include physical methods, chemical methods, and biological technology methods. The physical methods mainly include temperature regulation and pressure control, such as refrigerating or blanching the fresh-cut yam, which can inhibit the browning of yam to a certain extent. The chemical methods mainly use chemical inhibitors to competitively bind to phenolic substrates with enzymes, thereby changing the structure of phenolic substrates. The biological technology methods mainly use enzymes or plant extracts to inhibit the activity of phenolase.

[0004] The existing treatment methods can inhibit the browning of fresh-cut yam to a certain extent, but the overall control time is limited. And most of these methods are for processing crispy yam to ensure the crispy taste of yam while preventing browning. However, due to the relatively high starch content of glutinous yam, using general methods for processing often causes a large amount of starch loss, resulting in the loss of the soft and glutinous taste of fresh-cut yam after storage for a period of time, thus affecting the quality of glutinous yam. Therefore, further research is needed on the storage and anti-browning of fresh-cut glutinous yam. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention provides a treatment method for preventing browning of glutinous yam after peeling, which can effectively prevent browning of fresh-cut glutinous yam while reducing the loss of starch content, ensure the taste of glutinous yam, and enhance the value of fresh-cut storage of glutinous yam.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] A treatment method for preventing browning of glutinous yam after peeling, the treatment method comprising the following steps:

[0008] S1. Yam peeling treatment: Wash fresh yams thoroughly, then place them in ice water and let them stand for 15 - 20 minutes. After that, take them out, rinse them with clean water, and then peel them to obtain peeled yams for standby.

[0009] S2. Prepare the bleaching agent according to the following components: glutinous rice fermentation solution + zinc acetate 4 - 6 g / L + citric acid 400 - 600 mg / L + white vinegar 40 - 60 mg / L + D - isoascorbic acid sodium 40 - 60 mg / L; among which, the glutinous rice fermentation solution is obtained by crushing glutinous rice, adding water, fermenting with Lactobacillus plantarum and Trichoderma koningii together, and then boiling and filtering.

[0010] S3. Prepare the protective liquid according to the following components: sterile water + roselle polyphenol 10 - 20 mg / L + calcium chloride 15 - 20 g / L + chitosan 200 - 400 mg / L + konjac powder 10 - 20 g / L + sodium alginate 4 - 10 g / L.

[0011] S4. Preliminary soaking treatment: Place the peeled yams in the bleaching agent and soak them at 40 - 50 °C for 10 - 15 minutes. Then place them in sterile water and perform ultrasonic treatment under ice - water bath conditions. After ultrasonic treatment, place them in the normal - temperature bleaching agent again and soak for 5 - 10 minutes. Then take them out to obtain preliminarily soaked yams for standby.

[0012] S5. Secondary soaking treatment: Rinse the above - mentioned preliminarily soaked yams with sterile water, then place them in the protective liquid and soak for 30 - 40 seconds, and then take them out to obtain secondarily soaked yams for standby.

[0013] S6. Standing and packaging: Let the above - mentioned secondarily soaked yams stand at 50 - 60 °C for 20 - 30 minutes, then package them with polyethylene packaging film, and then store them in a normal - temperature environment or a cold storage at 2 - 5 °C for preservation.

[0014] Preferably, a ceramic knife is used for peeling in step S1.

[0015] Preferably, the preparation method of the glutinous rice fermentation solution in step S2 includes the following steps:

[0016] S2 - 1. Grind and crush glutinous rice, then add 6 - 10 times of clear water, and then add Lactobacillus plantarum for fermentation treatment for 8 - 10 hours to obtain a preliminarily fermented material for standby.

[0017] S2 - 2. Add Trichoderma koningii to the above - mentioned preliminarily fermented material and continue fermentation treatment for 4 - 6 hours to obtain a secondarily fermented material for standby.

[0018] S2 - 3. Boil the above - mentioned secondarily fermented material at 100 - 110 °C for 20 - 30 minutes, and then press and filter to obtain the glutinous rice fermentation solution.

[0019] Preferably, the addition amount of Lactobacillus plantarum in the step S2-1 is 0.2%-0.3% of the total mass of glutinous rice.

[0020] Preferably, the addition amount of Trichoderma koningii in the step S2-2 is 0.1%-0.2% of the total mass of glutinous rice.

[0021] Preferably, the time from the completion of peeling the peeled yam to placing it in the rinsing agent is ≤2 min.

[0022] Preferably, the power of the ultrasonic treatment in the step S4 is 200-400 W, and the time of the ultrasonic treatment is 20-30 s.

[0023] Preferably, the time of rinsing with sterile water in the step S5 is 10-15 s.

[0024] Preferably, the soaking treatment in the protective liquid in the step S5 is carried out at room temperature.

[0025] Preferably, the thickness of the polyethylene packaging film in the step S6 is 0.01-0.03 mm.

[0026] The present invention provides a treatment method for preventing the browning of peeled waxy yam. Compared with the prior art, the advantages are as follows:

[0027] In the present invention, after the yam is soaked in ice water and then peeled, it is soaked in a rinsing agent, which effectively inhibits the surface oxidation browning of the yam. At the same time, the heat preservation soaking and ultrasonic cleaning effectively remove the mucus on the surface of the yam, facilitating the subsequent treatment of the surface with the protective liquid. After the treatment with the protective liquid, it effectively prevents further oxidation and starch loss during storage. At the same time, static treatment is carried out at a temperature of 50-60 °C for a period of time to remove excessive moisture and accelerate the synthesis of starch in the yam, making up for the starch lost due to soaking and cleaning before, ensuring the soft and glutinous taste of the yam, and comprehensively ensuring the fresh-keeping effect of fresh-cut waxy yam. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the color change of the surface of the yam 3 minutes after peeling the yam in Example 1 and Comparative Example 1 of the present invention;

[0029] Figure 2 It is a schematic diagram of the browning situation of the yam after being treated with the methods of Experimental Groups 1-7 in the examples of the present invention when stored at room temperature for 30 days;

[0030] Figure 3 It is a schematic diagram of the browning situation of the yam after being treated with the methods of Experimental Groups 1-7 in the examples of the present invention when stored at 4 °C for 90 days. DETAILED DESCRIPTION OF THE INVENTION

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following describes the technical solutions in the embodiments of the present invention clearly and completely in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0032] The Lactobacillus plantarum used in the following examples was purchased from Xi'an Meihe Biotechnology Co., Ltd., with the product number MH-2104016076; Trichoderma koningii was purchased from Wuhan Huerna Biotechnology Co., Ltd., with the product number WN-Jj83546.

[0033] Example 1

[0034] 1. Preparation of glutinous rice fermentation solution:

[0035] 1.1 Fermentation solution A:

[0036] (1) Grind and crush glutinous rice, add 6 times the amount of clear water, and then add 0.2% of the total mass of glutinous rice of Lactobacillus plantarum for fermentation treatment for 10 h to obtain a preliminary fermentation material for standby;

[0037] (2) Add 0.1% of the total mass of glutinous rice of Trichoderma koningii to the above-mentioned preliminary fermentation material, and continue fermentation treatment for 6 h to obtain a secondary fermentation material for standby;

[0038] (3) Boil the above-mentioned secondary fermentation material at 100 °C for 30 min, and then press and filter to obtain fermentation solution A.

[0039] 1.2 Fermentation solution B:

[0040] (1) Grind and crush glutinous rice, add 10 times the amount of clear water, and then add 0.3% of the total mass of glutinous rice of Lactobacillus plantarum for fermentation treatment for 8 h to obtain a preliminary fermentation material for standby;

[0041] (2) Add 0.2% of the total mass of glutinous rice of Trichoderma koningii to the above-mentioned preliminary fermentation material, and continue fermentation treatment for 4 h to obtain a secondary fermentation material for standby;

[0042] (3) Boil the above-mentioned secondary fermentation material at 110 °C for 20 min, and then press and filter to obtain fermentation solution B.

[0043] 1.3 Fermentation solution C:

[0044] (1) Grind and crush glutinous rice, add 10 times the amount of clear water, and then add 0.3% of the total mass of glutinous rice of Lactobacillus plantarum and 0.2% of the total mass of glutinous rice of Trichoderma koningii for fermentation treatment for 10 h to obtain a fermentation material for standby;

[0045] (2) Boil the above fermentation material at 110 °C for 20 min, then press and filter to obtain fermentation solution C.

[0046] 1.4 Preparation of glutinous rice slurry:

[0047] Grind glutinous rice into powder, add 10 times the amount of water, boil at 110 °C for 20 min, then press and filter to obtain glutinous rice slurry;

[0048] 2. Preparation of the bleaching agent:

[0049] Prepare different bleaching agents according to the formula in Table 1 below:

[0050] Table 1

[0051]

[0052] 3. Preparation of the protective liquid:

[0053] Prepare different protective liquids according to the formula in Table 2 below:

[0054] Table 2

[0055]

[0056] Example 2:

[0057] Post-treatment of peeled waxy yam:

[0058] (1) Wash fresh yam clean, then place it in ice water and let it stand for 15 min, then take it out and peel it with a ceramic knife to obtain peeled yam for standby;

[0059] (2) Quickly put the peeled yam into the bleaching agent, soak it at 40 °C for 15 min, then place it in sterile water and perform ultrasonic treatment at 200 W for 30 s under ice bath conditions, then place it in the bleaching agent at room temperature again and soak it for 5 min, and then take it out to obtain the preliminarily soaked yam;

[0060] (3) Rinse the above preliminarily soaked yam with sterile water for 15 s, then place it in the protective liquid and soak it at room temperature for 40 s and then take it out to obtain the secondarily soaked yam for standby;

[0061] (4) Let the above secondarily soaked yam stand at 50 °C for 30 min, then package it with a polyethylene packaging film with a thickness of 0.02 ± 0.01 mm, and then store it.

[0062] Example 3

[0063] Post-treatment of peeled waxy yam:

[0064] (1) Wash fresh yam clean, then place it in ice water and let it stand for 20 min, then take it out and peel it with a ceramic knife to obtain peeled yam for standby;

[0065] (2) The peeled yam is quickly placed in a rinse agent, soaked at 50°C for 10 minutes, then placed in sterile water and ultrasonically treated at 400W for 20 seconds in an ice water bath, then placed in a room temperature rinse agent and soaked for 10 minutes, and then taken out to obtain the preliminary soaked yam;

[0066] (3) The yam that was initially soaked was rinsed with sterile water for 15 seconds, and then soaked in a protective solution at room temperature for 40 seconds before being taken out to obtain the second soaked yam for use;

[0067] (4) The twice-soaked yam is placed at 60°C for 20 minutes, and then packaged with a polyethylene packaging film with a thickness of 0.02±0.01 mm, and then stored.

[0068] Comparative Example 1:

[0069] Glutinous yam peeling process:

[0070] Wash the fresh yam, and then use a ceramic knife to peel the yam.

[0071] Detection

[0072] Select the commercially available iron stick yam as the glutinous yam raw material for the following tests:

[0073] 1. Peel the yam using the methods of Example 1 and Comparative Example 1, respectively, and observe the changes on the surface of the peeled yam within 3 minutes after peeling. The specific results are shown in Tables 3 and Figure 1 As shown:

[0074] Table 3

[0075]

[0076] 2. The treatment methods of the above-mentioned embodiment 2 and embodiment 3 are respectively adopted, and different rinsing agents and protective liquids are selected for treatment. The specific selection of rinsing agents and protective liquids is shown in the following Table 4:

[0077] Table 4

[0078]

[0079] Set the yam browning level according to Table 5 below:

[0080] Table 5

[0081]

[0082] 2.1. The yams of each of the above experimental groups were stored at room temperature (12 - 20 °C) for 10 days, 20 days, and 30 days. After being taken out, they were washed and then the browning grades of each group were observed (3 yams in each group, taking the average value), and the starch contents of the yams before peeling and after storage were detected. The specific results are shown in Tables 6 and 7 below:

[0083] Table 6

[0084]

[0085] Table 7

[0086]

[0087] As can be seen from the above table, under room temperature storage, Experimental Group 1 and Experimental Group 2 had a lower degree of browning during the 30 - day storage period, and the overall starch loss was also low.

[0088] 2.2. The yams of each of the above experimental groups were stored in a cold storage at 4 °C for 10 days, 45 days, and 90 days. After being taken out, they were washed and then the browning grades of each group were observed (3 yams in each group, taking the average value), and the starch contents of the yams before peeling and after storage were detected. The specific results are shown in Tables 8 and 9 below:

[0089] Table 8

[0090]

[0091] Table 9

[0092]

[0093] As can be seen from the above table, Experimental Group 1 and Experimental Group 2 can effectively inhibit the browning of yams under low - temperature storage at 4 °C, the shelf life can reach 90 days, and they can also effectively reduce the starch loss, ensuring that the yams after storage still have a soft and glutinous texture.

[0094] The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing glutinous yam from browning after peeling, characterized in that: The processing method comprises the following steps: S1. Peeling of yam: Wash the fresh yam, place it in ice water for 15-20 minutes, then take it out, rinse it with clean water and peel it. The peeled yam is set aside; S2. Prepare a rinse agent according to the following ingredients: glutinous rice fermentation solution + zinc acetate 4-6g / L + citric acid 400-600mg / L + white vinegar 40-60mg / L + D-sodium isoascorbate 40-60mg / L; wherein the glutinous rice fermentation solution is obtained by grinding glutinous rice, adding water, fermenting with Lactobacillus plantarum and Trichoderma koningii, and then boiling and filtering; The preparation method of glutinous rice fermentation solution comprises the following steps: S2-1, grind the glutinous rice, add 6-10 times of clean water, and then add Lactobacillus plantarum to ferment for 8-10 hours to obtain a preliminary fermented material for use; S2-2, adding Trichoderma koningii to the above-mentioned primary fermentation material, and continuing the fermentation process for 4-6 hours to obtain a secondary fermentation material for standby use; S2-3, cooking the secondary fermentation material at 100-110° C. for 20-30 min, and then squeezing and filtering to obtain a glutinous rice fermentation solution; S3. Prepare protective solution according to the following ingredients: sterile water + roxburghii polyphenol 10-20 mg / L + calcium chloride 15-20 g / L + chitosan 200-400 mg / L + konjac powder 10-20 g / L + sodium alginate 4-10 g / L; S4, preliminary soaking treatment: the peeled yam is placed in a rinse agent and soaked at 40-50°C for 10-15 minutes, then placed in sterile water and ultrasonically treated in an ice water bath, and then placed in a room temperature rinse agent and soaked for 5-10 minutes, then taken out, and the preliminary soaked yam is set aside; S5, secondary soaking treatment: rinse the above-mentioned primary soaked yam with sterile water, soak it in a protective liquid for 30-40 seconds, then take it out to obtain the secondary soaked yam for use; S6. Static packaging: The twice soaked yam is placed at 50-60°C for 20-30 minutes, then packaged with polyethylene packaging film, and then placed in a room temperature environment or a cold storage at 2-5°C for freshness preservation.

2. The method for preventing browning of peeled glutinous yam according to claim 1, characterized in that: In the step S1, a ceramic knife is used for peeling.

3. The method for preventing browning of peeled glutinous yam according to claim 1, characterized in that: The amount of Lactobacillus plantarum added in step S2-1 is 0.2%-0.3% of the total mass of the glutinous rice.

4. The method for preventing browning of peeled glutinous yam according to claim 1, characterized in that: In the step S2-2, the amount of Trichoderma koningii added is 0.1%-0.2% of the total mass of the glutinous rice.

5. The method for preventing glutinous yam from browning after peeling according to claim 1, characterized in that: The time from peeling to placing the peeled yam in the rinse agent is ≤2 minutes.

6. The method for preventing glutinous yam from browning after peeling according to claim 1, characterized in that: The power of the ultrasonic treatment in step S4 is 200-400W, and the time of the ultrasonic treatment is 20-30s.

7. The method for preventing glutinous yam from browning after peeling according to claim 1, characterized in that: The sterile water rinsing time in step S5 is 10-15 seconds.

8. The method for preventing glutinous yam from browning after peeling according to claim 1, characterized in that: The immersion treatment in the protective liquid in step S5 is performed at room temperature.

9. The method for preventing glutinous yam from browning after peeling according to claim 1, characterized in that: The thickness of the polyethylene packaging film in step S6 is 0.01-0.03 mm.

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