2, low-temperature air-conditioned storage: appropriate temperature can reduce the respiratory strength of the fruit, effectively inhibit the activity of polyphenol oxidase and microbial activity. Longan after harvest after pre-cooling treatment, plastic film packaging or film tent storage, and combined with drug preservation and low temperature storage; this is an effective method of longan storage, the method can play a spontaneous air-conditioning effect, change the carbon dioxide and oxygen content, thereby inhibiting microbial infestation and reducing the loss of spoilage.
3, sulfur preservation: Thailand in recent years, the export of longan have been fumigated with sulfur treatment, the method is to burn 100 grams per cubic meter of 90% sulfur powder, treatment for 20 to 30 minutes. Formulated with sodium bisulfite sulfur dioxide release agent, per 2 kg longan dosage of 16 to 22 grams of room temperature storage achieved good results. Longan with sulfite solution immersion without freshness, slow release sulfur treatment to 6 to 8 grams per kg of longan with sodium dithionite is good. Fumigation treatment is 20 grams of sulfur per 10 kg longan, fumigation for 20 minutes, low temperature storage for 35 days, good fruit rate of 96%, while the control is 0. Sulfur dioxide can effectively prevent peel browning and inhibit microbial infestation, fumigated by sulfur longan fruits at 10 or 5 degrees Celsius, the peel is not browning and disease can be maintained for 11 months (peel has been shriveled).
4, air-conditioned freshness: longan after harvest, the first pre-cooled 2 days, and then sort out the fruit, cut off the poor fruit, broken fruit, with 0.1% metribuzin drenched spike to sterilize, directly in 0.04 mm thick polyethylene film bag, or first installed in a plastic crate, and then set on a plastic bag (thickness of 0.04 mm), in the humidity of 85% to 95%, the temperature of 0 to 5 ℃ (not exceeding 10 ℃) in the warehouse storage. After pre-cooling, packaged in plastic bags, and then pumping, nitrogen-filled treatment, storage at 0 ~ 5 ℃ or 6 ~ 10 ℃ conditions, the preservation effect is very good, 40 days of storage, the good fruit rate is still up to 93% or so. During the storage period, pay attention to adjust the proportion of carbon dioxide and oxygen in the storage environment. The bag of gas indicators to oxygen 6% to 8%, carbon dioxide 4% to 6% more appropriate.
5, hot ironing freshness: this method is the traditional folk preservation method. Folk is the whole spike of fruit immersed in boiling water for 30 to 40 seconds, in order not to scald the flesh to the extent that it is lifted immediately, hanging in the wind to dry. The treated fruits are left for 15 to 25 days, and the flesh remains basically fresh with a sweeter flavor. This method combined with modern preservation technology, that is, the hot scald treatment, drying, boxing of the fruit, placed in a cold storage at 2 ± 1 ℃, storage for 22 days, the rate of good fruit is 100%. Fruit appearance and color similar to fresh fruit, endocarp uniform browning, pulp flavor normal.
6, quick-frozen freshness: pick a good fresh fruit, anti-cracking treatment, the center of the longan fruit temperature down to -30 ° C in 1 hour, and then long-term storage at -18 ° C in cold storage, can be stored for a year or longer. Quick-frozen longan from -18 ℃ low temperature removed, with 0.5% citric acid plus 0.03% vitamin C solution or 1% citric acid solution treatment, can keep 48 hours of fruit skin does not change color.