Coating preservation of the hottest strawberry

2022-08-21
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Coating storage and preservation of strawberries

strawberries are berry fruits with high water content, delicate tissue, and easy to rot and deteriorate due to mechanical damage and microbial infection. At room temperature, strawberry fruits change color and taste after 1-3 days of storage, losing their original flavor and commodity value. Adopting appropriate storage technology can prolong the supply period of strawberries

first, choose storage resistant varieties:

strawberry varieties that are more storage resistant include: chicken heart, lion head, gorela, shuomi, Shuofeng, Chunxiang, nvfeng, Lihong, etc

II. Appropriate harvest time:

strawberries used for storage are generally harvested at the eighth maturity. The ripening period of strawberries is inconsistent, and they should be harvested in batches. During the ripening process, the fruit turns from green to white and then gradually turns red. It is appropriate to harvest strawberries when the color of about 3/4 of the surface area of strawberries turns red. No irrigation is allowed for 3-5 days before harvest. Harvest in sunny days when the dew is dry and the temperature is low. When harvesting, handle with care to avoid mechanical damage to the fruit

III. storage methods:

the main purpose of strawberry storage and preservation is to maintain its hardness and color and inhibit the growth of microorganisms (mainly fungi)

1. Chemical preservation

(1) phytic acid: phytic acid is a natural non-toxic food antioxidant extracted from rice bran or wheat bran. When it is used for strawberry preservation, it can delay the degradation of vitamins in the fruit, maintain the soluble solids and acid content in the fruit, and improve the speed and accuracy of conditioning, but the antibacterial effect is weak, so it needs to be used in combination with other chemicals. Strawberries treated with 0.1%-0.15% phytic acid, 0.05%-0.1% sorbic acid and 0.1% Peracetic acid can be kept fresh for one week at room temperature and 15 days at low temperature, with a good fruit rate of 90%-95%

(2) SO2: put strawberries into plastic boxes with covers, put 1 bag -2 bags of SO2 chronic releasing agent respectively, and keep a certain distance between the agent and strawberries, so that SO2 can diffuse evenly between fruits, so as to prevent SO2 from directly contacting strawberries with high concentration, making the fruits white and soft, and losing edible value and commodity value. The preservation test showed that using a bag of SO2 slow-release agent for storage for 20 days, the good fruit rate was 67.7%, the commodity rate was 61.1%, and the bleaching rate was 8%. It had a better storage effect and looked forward to the future

2. Controlled atmosphere storage

control the oxygen in the storage environment and the concentration of carbon dioxide in the oil system with serious oil leakage, which can reduce the respiration and other metabolic activities of strawberries, inhibit the reproduction of fungi and control decay. After research, strawberry storage oxygen concentration can not be less than 3%, carbon dioxide concentration can not be higher than 20%, beyond this range, strawberry metabolism disorders, due to the accumulation of acetaldehyde, ethanol and other substances produce odor. The suitable conditions for controlled atmosphere storage of strawberries are: temperature 0 ℃ -1 ℃, relative humidity 85%-95%, oxygen 3%, carbon dioxide 3%-6%

(1) plastic small package storage: it belongs to gas Limited (MA) storage. Put the selected strawberry fruit into 90cm × 60cm × A 15cm plate is filled and sent to the precooling room for precooling. The precooled strawberries are put into airtight plastic bags (0.04mm thick polyethylene film bag, 95cm × 65cm × 20cm), and put a piece of ethylene adsorbent, then seal it, and put it into a cold storage with a temperature of 0 ℃ -1 ℃ and a relative humidity of 85% - 95%, which can be stored for about 2 months

(2) map storage: it is a kind of controlled atmosphere storage, which is simple and easy to operate, that is, it has less investment, and can preserve the products in the process of transportation, wholesale and retail, without pollution. It has lower storage cost than Ca (cotrel atmosphere storage) and better storage effect than ma. Map storage requires zqf550/4 vacuum packaging machine, gm-b gas mixer, cyes-ii carbon dioxide/oxygen detector, N2 bottle, oxygen bottle, carbon dioxide bottle and other equipment

mix the gas in proportion. The strawberry is oxygen: 8%, carbon dioxide: 3%, n2:89%. Other requirements are the same as (1). After the pre cooled strawberries are put into plastic bags, vacuum them, drain the gas in the bags, and then fill the mixed gas into the plastic bags for sealed storage. The temperature is 0 ℃ -1 ℃, the relative humidity is 85%-95%, and they are fresh after storage for more than 2 months

because strawberry is a fruit whose water evaporation is independent of temperature, even under the condition of near freezing point, when there is no package, the water evaporation is also very intense. Therefore, in order to prevent water loss and maintain freshness, it is necessary to pack it in plastic bags to improve the relative humidity of the surrounding environment, and keep the storage temperature constant to prevent sweating and rot

3. Film preservation

coating preservation is a preservation technology developed in recent years. Chitosan film is widely used in strawberry preservation with good effect. After 31 days of chitosan coating, strawberries can still maintain hardness and better vitamin C content. The concentration of chitosan affects the quality and storage of strawberries, and the concentration is low, so it cannot play its due role; If the concentration is too high, not only the hardness and high vitamin C content cannot be maintained, but also the metabolism of strawberries is out of balance due to poor permeability, which shortens the storage period. At present, the optimal concentration of chitosan is recommended to be 0.5%. There are also composite films with 0.8% ethyl p-hydroxybenzoate and 0.5% stearic acid monoglyceride, which have good effects

in addition, adding calcium fertilizer before harvest or soaking calcium after harvest can inhibit the softening of strawberries and prolong the storage period. The time of soaking calcium is related to the concentration of calcium salt. If the concentration is large, the time of soaking calcium is short. Soak it in 3%-5%cacl2 solution for 5 minutes

(author/Xu Ling, Ding Liqun, Han Guotao)

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