Hsu, min-chi, Yu-shan Lin and Chao-Chai Huang
Pitaya, dragon fruit (Hylocereus undatus Britt. & Rose) belongs the Cactaceae family and is native of mid and south America. Its major harvest months in Taiwan is from June to December. Red flesh pitayas are even harvested for nine months per year by lighting treatment, but production season are from July to November and requires short time for storage and exportation. Another disadvantage are that peels on harvested fruits will will appear dry and old, and lower temperature with high moisture storage will induce fungal disease after being reheated to room temperature. In order to overcome these problems, dragon fruit growers should be concerned about postharvest handling technologies.
Precooling is the first step after harvest. This strategy is essential and vital for storage and export. Room cooling is common and is a simple way to remove “field heat”. More efficient methods are Forced-air cooling and Hydrocooling. Within forced-air cooling fruits decreased 5-15 times compared to room-cooling. Hydrocooling is another novel method for precooling, but still needs to overcome water, energy, mico-organism and handling method.
Investigating the cold resistance of white-pulp pitayas’ field in the middle and south fields of Taiwan, whether it be summer (Jul-Aug) or winter (Oct-Dec), the fruits were found to be less divergent to cold resistance. On the other hand, disease which occur on the fruit peel within long time storage severely increased with lobgerstorage time, especially more if it was more than 3 weeks. The object of selecting packing materiasl to avoid chilling injury, non-woven fabric with PE bag( 24 holes with 0.8cm diameter) were used without chilling injury and had better performance for 20 days storage. The preliminary results show that fruits treated with active MAP (bags sealed after flushed with 3% O2 and 5% CO2), followed by hypobaric packaging and sealed package maintained better visual appearance after 19 days of storage at 5℃. In addition, MAP (1~5% O2 and 5% CO2) did not cause significant negative effect on fruit quality.
Quarantine treatment of VHT (vapor heat treatment) usually used for pitaya export to Japan there are no fruit flies. The process of treatment need 2.5-3 hours and the center temperature of fruit is more than 46.5℃ for 30 mins. After quarantine treatment, Differential maturity fruits were treated and quarantine treatment shows no remarkable difference. is the peel and pulp showed no significant change. VHT could also decrease the occurrence of disease during export transportation and shelf storage.
Each data represents mean ±S.E of fourteen replicates (n=14).
＊＊Apparence score (9=fresh and well , 7= good, 5=fair for sale, 3=loss soldability, 1=wrose)
＊＊＊Decay severity score (decay region :0=0%, 1=0-5%, 2=6-10%, 3=11-20%, 4=21-30%, 5 more than 30%)
The preliminary results show that fruit stored in plastic bags had lower weight loss and maintained greener bracts compared with fruit without plastic bags during storage. Sealed with LDPE plastic bags maintained better visual appearance of pitaya fruit after 20 days storage at 5℃ and shelf-life, by reducing decay severity.
Table 2. Influence of package on the gas compositions during modified atmosphere storage at 5°C.
Table 3. Effect of MAP on the soluble solids and titratable acidity of pitaya.
＊Each data represents mean ±S.E of seven replicates (n=7).
＊＊taste evaluation (59=fresh and well , 4= good, 3=fair for sale, 2=loss soldability, 1=wrose)
VAPOR HEAT TREATMENT (VHT)
To prevent the proliferation of disease and pests, strict plant quarantine is being carried out in every country. For example, there is an obligation to exceed international standards when importing vegetables and fruits such as papaya, mango, lychee, and paprika into any country that does not have oriental fruit flies (Bactrocera dorsalis species complex) or melon fly (Bactrocera cucurbitae).
This kind of container-based Vapor Heat Treatment System (VHTs) uses no chemicals but has high temperature vapor to cleanly disinfect fruit from the eggs and larvae of harmful insects (Fig. 6 and Fig. 7).
Fig. 6. VHTs facility treating for quarantine treatment. (Pic from: http://fth-net.jp/en-vhts/)
Fig. 7. Pitaya quarantine treatment for ecporting to Japan in Taiwan.
After quarantine treatment, fruits are pre-cooled then packed in corrugated boxes. Such method is necessary before export. In Taiwan, we used a king of force-air cooling facility which is called: “ceiling jet” for producing steady and continuous air flow for cooling fruits. Differential maturity fruits treated with quarantine treatment shows non-remarkable difference. Fruit pulps and peels showed no significant change. VHTs could also decrease disease occurrence during export transportation and shelf storage.
In many countries, marketing of perishable crops becomes increasingly important as the consumers’ standard of living increases. Because the requirement is higher, more consistent quality of fruits is needed by the consumers. This normally results in a seller’s market where the farmer can sell all horticultural products that they grow. There may be little incentive to supply higher-quality proucts to the target market. This happened in less and normal developed countries. In developed countries, the crop and potential crop production are greater than the demand. In both of these conclusions, postharvest handling is very important for dragon fruits to earn more benefits and decrease food loss in all countries. According to these technologies and handling stratergies, dragon fruit could maintain achieve better quality, higher price, larger markets, and more long supply.
Taipei Wholesale Market Trading Information Website: (http://amis.afa.gov.tw/menu/FruitMenuTransInfo.aspx)
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