Post-harvest preservation method for glutinous Chinese yams

Abstract

The invention provides a postharvest preservation method of glutinous Chinese yam, and relates to the technical field of Chinese yam storage. The method mainly comprises the following steps: designing a preservative prepared from dry fig leaf powder, an anise extract, peppermint essential oil, rice sterilization fermentation liquor and calcium chloride, spraying the Chinese yam, soaking a non-woven fabric with the preservative to prepare a fumigating sheet, and performing long-term fumigating treatment on the Chinese yam in a storage period. The storage temperature is controlled to be low temperature or normal temperature. According to the method, the defects in the prior art are overcome, the glutinous Chinese yam can be preserved for a long time in a low-temperature environment and a normal-temperature environment through combined use of the preservative and the fumigating and killing pieces, germination and starch loss in the storage period of the Chinese yam are effectively prevented, the quality of the stored glutinous Chinese yam is comprehensively improved, and waste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of yam storage, and in particular to a method for preserving glutinous yam after harvest. Background Art

[0002] Yam is a root vegetable that can be used as both medicine and food, with high nutritional value. However, yam is generally harvested once a year. In order to meet the market supply of yam throughout the year, most of the yams are stored and preserved after being harvested in the season. Yam itself has the characteristics of storage resistance and is generally resistant to low humidity and low temperature. However, due to the high water content in yam, it is very easy to germinate in a certain environment. Using cold storage will inhibit germination to a certain extent, but it will greatly increase the storage cost.

[0003] Glutinous yam is a type of yam with a higher starch content. After long-term storage, it not only faces the problem of yam sprouting, but also easily causes the starch content to decrease, resulting in a sudden drop in the edible taste of the glutinous yam, affecting actual sales, especially in low-temperature storage environments. Due to the inhibition of yam metabolism, the starch content continues to decline. The longer the storage time, the less starch content. During room temperature storage, due to vigorous anabolism in the early stage, the starch synthesis rate is greater than the decomposition rate under appropriate temperature conditions. Therefore, the starch content will increase in the early stage of room temperature storage, further improving the taste of the glutinous yam. However, as the storage time increases, generally after three months, the yam's dormancy ends, and the starch will be greatly consumed in a room temperature environment. Sprouting may occur, and the starch content drops rapidly, seriously affecting the storage quality of the glutinous yam. On this basis, further research is needed on long-term preservation methods for glutinous yam. Summary of the invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a post-harvest preservation method for glutinous yam. The combined use of a preservative and a fumigation tablet can preserve the glutinous yam for a long time in a low-temperature environment and a normal temperature environment, effectively prevent germination and starch loss of the yam during storage, comprehensively improve the quality of the glutinous yam after storage, and reduce waste.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions: A method for preserving glutinous yam after harvest, the method comprising the following steps: S1. Precooling of Chinese yam: freshly obtained Chinese yam is placed in a cold storage at 4-8°C for 2-4 hours to obtain precooled Chinese yam for use; S2. Prepare the preservative according to the following parts by weight: 3-5 parts of fig leaf powder, 0.2-0.5 parts of star anise extract, 0.8-1.2 parts of peppermint essential oil, 30-40 parts of rice sterilized fermentation liquid, and 1-1.3 parts of calcium chloride; S3, preparation of fumigation tablets: soaking non-woven fabric in the above-mentioned preservative, then taking out and drying at 40-50° C. to a moisture content of ≤10%, to obtain fumigation tablets; S4, ultraviolet irradiation treatment of yam: the pre-cooled yam is irradiated with short-wave ultraviolet rays of 200-280nm for 10-20min to obtain irradiated yam for later use; S5. Preservative spraying treatment: spray the surface of the irradiated yam with preservative and dry it naturally. After bagging, store it in a cold storage or a normal temperature warehouse, and put a fumigation sheet in each bag after storage.

[0006] Preferably, the fig leaf dry powder is obtained by freeze-drying fig leaves and then crushing them through a 80-100 mesh sieve.

[0007] Preferably, the preparation method of the star anise extract comprises the following steps: S2-1-1, grind the star anise into powder, mix with vegetable oil, and steam for 30-40 minutes to obtain the pre-treated star anise material for later use; S2-1-2, add ethanol solution to the pretreated star anise material, increase the pressure to 1-2Mpa at 40-50°C, extract for 2-4h, filter to obtain filter residue and filtrate, continue to add ethanol solution to the filter residue, continue to increase the pressure to 1-2Mpa at 40-50°C, extract for 2-4h, centrifuge, separate the clear liquid and combine the filtrate to obtain the extract for standby use; S2-1-3. Concentrate the above extract in vacuo to 1 / 5-1 / 10 of its original volume, and then freeze-dry to obtain anise extract.

[0008] Preferably, the vegetable oil in step S2-1-1 is any one or more of coconut oil, palm oil, olive oil, and soybean oil, and the amount of the vegetable oil added is 5%-8% of the total mass of the star anise.

[0009] Preferably, the concentration of the ethanol solution in step S2-1-2 is 65%-75%.

[0010] Preferably, the method for preparing the sterilized rice fermentation liquid comprises the following steps: S2-2-1, adding 5-10 times volume of water to rice and soaking overnight, then inoculating yeast and Lactobacillus paracasei, stirring and mixing evenly, and fermenting for 3-5 days to obtain fermented material for standby use; S2-2-2, boiling and sterilizing the fermented material at 100-110°C for 20-30 minutes, and then filtering, and the filtrate is the sterilized rice fermentation liquid.

[0011] Preferably, the number of live yeast cells inoculated in step S2-2-1 is 10 10 -10 11 / g, the inoculation amount is 0.2%-0.4% of the total weight of rice; the number of viable Lactobacillus paracasei is 10 10 -10 11 / g, and the inoculation amount is 0.1%-0.2% of the total mass of rice.

[0012] Preferably, the thickness of the non-woven fabric in step S3 is 1.2-1.5 mm.

[0013] Preferably, the weight of each bag of yam in step S5 is 25-35 kg, and the specifications of the smoked slices put into each bag of yam are 10 cm×15 cm.

[0014] Preferably, the temperature of the cold storage in step S5 is 4-15°C.

[0015] The present invention provides a method for preserving glutinous yam after harvest, which has the following advantages compared with the prior art: The invention uses dried fig leaf powder, star anise extract, peppermint essential oil, rice sterilization fermentation liquid and other ingredients combined with calcium chloride to treat the yam, and combines precooling and ultraviolet irradiation treatment to effectively preserve the yam, prevent the yam from corruption during storage, and effectively prevent the consumption of starch when the glutinous yam is stored in low-temperature and normal-temperature environments. At the same time, combined with subsequent fumigation tablets, the germination phenomenon of the yam stored at room temperature is effectively inhibited, thereby achieving a good preservation and storage purpose, and is suitable for low-temperature storage and normal-temperature storage. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The yeast in the following examples was purchased from Jinan Jinyuyuan Biotechnology Co., Ltd. with the product number JYY-01 and the viable count was 2×10 10 Lactobacillus paracasei was purchased from Shandong Pingao Pharmaceutical Co., Ltd. with the product number PG-LPF109 and the number of viable bacteria was 10 10 Pieces / g.

[0018] Example 1 Preparation of fresh-keeping medicine: 1. Preparation of Fig Leaf Powder: Take fresh fig leaves, wash them, freeze-dry them, and then grind them through an 80-mesh sieve to obtain fig leaf dry powder.

[0019] 2. Preparation of star anise extract: 2.1. Extract A: (1) Grind the star anise into powder, mix it with palm oil (6% by weight of the total weight of the star anise), and steam it for 35 minutes to obtain the pre-treated star anise material for later use; (2) Add 70% ethanol solution to the pretreated star anise material, increase the pressure to 1 MPa at 45°C, extract for 4 hours, filter to obtain the residue and filtrate, continue to add 70% ethanol solution to the residue and continue to increase the pressure to 1 MPa at 45°C to extract for 4 hours, centrifuge, separate the clear liquid and combine the filtrate to obtain the extract for use; (3) The above extract was concentrated under vacuum to 1 / 5 of its original volume, and then freeze-dried to obtain extract A.

[0020] 2.2 Extract B: (1) Grind the star anise into powder, add 70% ethanol solution, increase the pressure to 1 MPa at 45°C, extract for 3 hours, filter to obtain the residue and filtrate, add 70% ethanol solution to the residue, continue to increase the pressure to 1 MPa at 45°C, extract for 3 hours, centrifuge, separate the clear liquid and combine the filtrate to obtain the extract for use; (2) The above extract was concentrated under vacuum to 1 / 5 of its original volume, and then freeze-dried to obtain extract B.

[0021] 3. Preparation of rice sterilized fermentation liquid: 3.1. Fermentation broth A: (1) adding 8 times the volume of water to rice and soaking it overnight, then inoculating 0.3% of the total weight of the rice with yeast and 0.15% of the total weight of the rice with Lactobacillus paracasei, stirring and mixing evenly, and fermenting for 4 days to obtain a fermented material for use; (2) The fermented material is placed at 110°C for 20 minutes for sterilization and then filtered. The filtrate is fermentation liquid A.

[0022] 3.2. Fermentation broth B: (1) adding 8 times the volume of water to rice and soaking it overnight, then inoculating 0.3% of the total weight of the rice with yeast and 0.15% of the total weight of the rice with Lactobacillus paracasei, stirring and mixing evenly, and fermenting for 4 days to obtain a fermented material for use; (2) Filter the fermentation material and the filtrate is fermentation liquid B.

[0023] 4. Preparation of preservatives and fumigation tablets: Prepare each group of preservatives according to the mass proportions of the components in Table 1 below: Table 1

[0024] Select a non-woven fabric with a thickness of 1.35 mm, soak it in the above-mentioned preservatives 1-6 for 20 minutes, take it out, and dry it at 45°C until the water content is ≤10%, and obtain fumigation tablets 1, fumigation tablets 2, fumigation tablets 3, fumigation tablets 4, fumigation tablets 5, and fumigation tablets 6 respectively (each group of fumigation tablets is cut into a rectangular sheet of 10 cm×15 cm for standby use).

[0025] Example 2 How to keep glutinous yam fresh after harvesting: (1) Place the freshly obtained yam in a cold storage at 6°C for 3 hours to pre-cool the yam for later use; (2) irradiating the pre-cooled yam with short-wave ultraviolet light of 200-280 nm for 15 minutes to obtain the irradiated yam for later use; (3) The irradiated yam is sprayed with a preservative on the surface and then dried naturally. The yam is packed in nylon bags with each bag weighing 25-35 kg. The yam is then stored in a cold storage or a warehouse at room temperature, and a fumigation sheet is placed in each bag after storage.

[0026] Detection 1. Referring to the above Example 2, the yam was weighed before bagging, and the starch content of the glutinous yam before storage was detected to be 22.5%. The yam was then bagged and stored in a cold storage at 4°C for 180 days. The yam was then taken out and the germination rate, weight loss rate and starch content after storage were detected (the starch content was determined by randomly selecting 5 yams for testing and taking the average value): The germination rate was tested as follows: 60 buds were selected from a single yam tuber to observe the germination, repeated for 3 times, and the average value was taken; germination rate (%) = (number of germinations / total number of observed buds) × 100%; Weight loss rate (%) = (weight before storage - weight after storage) / weight before storage × 100%; The specific results are shown in Table 2 below: Table 2

[0027] It can be seen from Table 2 above that when stored in a low temperature environment of 4°C, the experimental groups using preservative 1 + fumigation tablet 1 and preservative 2 + fumigation tablet 2 can effectively reduce starch loss and reduce weight loss.

[0028] 2. Same as the above experiment 1, only the storage temperature was controlled at 15°C, and the germination rate, weight loss rate and starch content of each group of glutinous yam after storage for 180 days were tested. The specific results are shown in Table 3 below: Table 3

[0029] It can be seen from Table 3 above that when the glutinous yam was stored at 15°C for 180 days, the starch content in experimental groups 8 and 9 increased relatively. This is because the metabolism of starch synthesis is relatively high at this temperature, and the yam can further synthesize starch in the early stage of storage. In addition, due to the subsequent inhibition of germination of the yam, the starch was not consumed significantly, so the overall starch content increased.

[0030] 3. Same as the above experiment 1, only the storage temperature was controlled to be room temperature (20-30°C), and the germination rate, weight loss rate and starch content of each group of glutinous yam after storage for 180 days were tested. The specific results are shown in Table 4 below: Table 4

[0031] It can be seen from Table 4 above that the starch content in experimental groups 15 and 16 increased significantly after storage for 180 days. This is mainly due to the relatively suitable temperature, the early metabolism and synthesis of starch in the yam is relatively large, and the subsequent germination is inhibited, and the amount of starch consumed is relatively small. Under this condition, the overall taste of the yam after storage is glutinous, which can meet the market sales demand of glutinous yam, and the overall water loss rate is low.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preserving glutinous yam after harvesting, It is characterized in that The fresh-keeping method comprises the following steps: S1. Precooling of Chinese yam: freshly obtained Chinese yam is placed in a cold storage at 4-8°C for 2-4 hours to obtain precooled Chinese yam for use; S2. Prepare the preservative according to the following parts by weight: 3-5 parts of fig leaf powder, 0.2-0.5 parts of star anise extract, 0.8-1.2 parts of peppermint essential oil, 30-40 parts of rice sterilized fermentation liquid, and 1-1.3 parts of calcium chloride; S3, preparation of fumigation tablets: soaking non-woven fabric in the above-mentioned preservative, then taking out and drying at 40-50° C. to a moisture content of ≤10%, to obtain fumigation tablets; S4, ultraviolet irradiation treatment of yam: the pre-cooled yam is irradiated with short-wave ultraviolet rays of 200-280nm for 10-20min to obtain irradiated yam for later use; S5. Preservative spraying treatment: spray the surface of the irradiated yam with preservative and dry it naturally. After bagging, store it in a cold storage or a normal temperature warehouse, and put a fumigation sheet in each bag after storage.

2. A method for preserving glutinous yam after harvest according to claim 1, Features: The fig leaf dry powder is prepared by freeze-drying fig leaves and then crushing them through a 80-100 mesh sieve.

3. A method for preserving glutinous yam after harvest according to claim 1, It is characterized in that The preparation method of the star anise extract comprises the following steps: S2-1-1, grind the star anise into powder, mix with vegetable oil, and steam for 30-40 minutes to obtain the pre-treated star anise material for later use; S2-1-2, add ethanol solution to the pretreated star anise material, increase the pressure to 1-2Mpa at 40-50°C, extract for 2-4h, filter to obtain filter residue and filtrate, continue to add ethanol solution to the filter residue, continue to increase the pressure to 1-2Mpa at 40-50°C, extract for 2-4h, centrifuge, separate the clear liquid and combine the filtrate to obtain the extract for standby use; S2-1-3. Concentrate the above extract in vacuo to 1 / 5-1 / 10 of its original volume, and then freeze-dry to obtain anise extract.

4. A method for preserving glutinous yam after harvest according to claim 3, Features: In step S2-1-1, the vegetable oil is any one or more of coconut oil, palm oil, olive oil, and soybean oil, and the amount of the vegetable oil added is 5%-8% of the total mass of the star anise.

5. A method for preserving glutinous yam after harvest according to claim 3, Features: The concentration of the ethanol solution in step S2-1-2 is 65%-75%.

6. A method for preserving glutinous yam after harvest according to claim 1, It is characterized in that The preparation method of the rice sterilization fermentation liquid comprises the following steps: S2-2-1, adding 5-10 times volume of water to rice and soaking overnight, then inoculating yeast and Lactobacillus paracasei, stirring and mixing evenly, and fermenting for 3-5 days to obtain fermented material for standby use; S2-2-2, boiling and sterilizing the fermented material at 100-110°C for 20-30 minutes, and then filtering, and the filtrate is the sterilized rice fermentation liquid.

7. A method for preserving glutinous yam after harvest according to claim 6, Features: The number of live yeast cells inoculated in step S2-2-1 is 10 10 -10 11 / g, the inoculation amount is 0.2%-0.4% of the total weight of rice; the number of viable Lactobacillus paracasei is 10 10 -10 11 / g, and the inoculation amount is 0.1%-0.2% of the total mass of rice.

8. A method for preserving glutinous yam after harvest according to claim 1, Features: The thickness of the non-woven fabric in step S3 is 1.2-1.5 mm.

9. A method for preserving glutinous yam after harvest according to claim 1, Features: In step S5, the weight of each bag of yam is 25-35 kg, and the specifications of the smoked slices put into each bag of yam are 10 cm×15 cm.

10. A method for preserving glutinous yam after harvest according to claim 1, Features: The temperature of the cold storage in step S5 is 4-15°C.

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