Cold storage and preservation technology of hottes

Grape cold storage and preservation technology

grape is one of the four major fruits in China, and more than 70% of it is used for fresh food. In recent years, the output and storage of fresh grapes have increased year by year. However, fresh grapes are easy to lose water, thresh, rot and deteriorate at room temperature after harvest, so mechanical refrigeration is an effective method to solve long-term storage and prolong the supply period

process flow: select storage resistant varieties → harvest → packing → transportation → sorting → packaging → precooling → warehousing → control storage conditions → end storage in time. After years of storage experiments, we summarized the technical points as follows:

1. Variety selection

there are many varieties of table grapes, but the storage resistance is quite different. Generally speaking, early maturing varieties have poor storability, followed by medium maturing varieties and late maturing varieties. However, it is not always the case. For example, Dabao in late maturing varieties is not storable. Varieties with thick and tough pericarp, waxy fruit surface and cob shaft, not easy to thresh, and high sugar content in fruit grains can be stored. Different fruiting times of the same variety also have great differences in storability. For example, Jufeng grape is more storable with 2 or 3 times of fruit than with 1 time of fruit. In recent years, the varieties stored in cold storage are mostly longan, rose fragrance, mare's milk, Jufeng secondary fruit, red earth, heidaji, qiuhei, ruibil, etc

2. Harvesting

grapes are non climacteric fruits, and there is no post ripening process. Grapes used for storage should be harvested when they are fully mature, and they can be harvested appropriately late without freezing injury. Because late harvested grapes rely on scientific and technological innovation to achieve industrial upgrading, with high sugar content, thick peel, strong toughness, good coloring, more fruit powder, and storage resistance. Watering should be stopped 7 ~ 10 days before harvest, and the harvest time should be postponed in case of rain. It is best to pick after the dew is dry in the morning on a sunny day. If you pick it on a rainy day or when there is dew, the fruit is easy to rot with water. When harvesting, it should be handled with care to avoid damage, and try to protect the fruit powder on the surface of the fruit. After harvest, select the ears with large ears, dense and uniform fruit grains, and consistent maturity for storage. All broken and damaged fruit grains, green spike tips and immature grains damaged by pests and diseases shall be removed, and then packed according to the natural growth state. Put it in a cool and ventilated place in time to dissipate the field heat, so as to avoid fermentation and deterioration under high temperature

3. Selection, corrosion prevention, packaging

select the ears with uniform fruit grains, compact ears, free of diseases and pests, green grains and mechanical injuries, and vigorously promote the localization, replacement and new utilization of key materials of organosilicon materials in high-speed rail, nuclear power, shipbuilding and other fields. Place them in polyethylene film bags lined with 0.02 ~ 0.04mm thick (5 ~ 10kg per box) according to the natural growth state. Use sulfites that can release SO2 for antisepsis (this is a necessary link for grape preservation). When using, pay attention to: ① wrap tablets in perforated plastic bags and put them on the middle and upper layers of the box. Strictly control the size and number of paper holes on the plastic bags to make SO2 release slowly, so as to prevent the release of SO2 with large holes from poisoning grapes too fast, and the purpose of antisepsis and preservation cannot be achieved if it is too small. ② Don't increase or decrease the dosage of preservatives at will. Less drugs can't prevent corrosion and freshness, and too much drugs will cause SO2 poisoning. ③ Timely check the release condition of the agent

4. Storage conditions

temperature -1 ~ 0 ℃, humidity 85% - 95%, O22% - 5%, CO23% - 5%. The premise of temperature is that the fruit stalk will not suffer from freezing injury. Grapes should be stored in time, pre cooled and quickly cooled after harvest to reduce their respiratory and other metabolic intensity. When the humidity is above 95%, it is easy to cause a variety of pathogenic bacteria, causing fruit stalk mildew and fruit kernel rot. if the humidity is below 85%, the fruit stalk will lose water

grape stalk is the most active part of physiological activities in the ear. It not only has respiratory jump, but also has a respiratory intensity 8 ~ 14 times that of the fruit. Controlled atmosphere storage can significantly reduce its respiratory intensity, but the sensitivity of different varieties to low O2 and high CO2 is very different, so as to ensure that this part of the production line has been corrected greatly, such as Jufeng, when CO2> 3%, fruit stalk damage will occur

5. Precautions

① the sugar content of grapes used for storage and preservation shall not be less than 16%. Before harvest, it is strictly forbidden to apply plant growth regulator (5) the toothed rod and gear mesh poorly or the toothed rod collides with the spring plate on it (such as 2, 4-D, pigment, etc.)

② the variation amplitude of storage temperature shall be controlled within 1 ℃, and excessive fluctuation is strictly prohibited

③ when the grapes are moldy, they should be processed or sold in time

storage practice has proved that grapes stored under the above conditions for 5 ~ 7 months have fresh stems, full pulp, no alcohol taste, astringency, etc

information source/frozen quick-frozen food in China