Study On The Packaging, Logistics Technology And The Mechanism Of Chilling Injury Of Mini Cucumber

Fruit cucumber, also known as mini cucumber, is tenderer than normal cucumber with both fruit and vegetable edible characteristics, and is well received by consumers. However, the mini cucumber quickly deteriorates after harvest due to its thin peel and easiness to water loss. Under ambient temperature, it would wilt in 1 d~2 d after harvest. On the other hand, stored at unsuitable low temperature would lead to chilling injury of the fruit. Therefore, it is impracticable to promote long distance transportation. In this study, new packaging materials, refrigeration, precooling and logistics technology were investigated, and according to the occurrence of chilling injury of the cucumber fruit during storage and logistics process, the related gene expression patterns and interactions were studied as well. The main results were as follows:1. Sealed packaging with microporous anti-fog film and PE film were suitable to maintain the postharvest quality of mini cucumber stored at 11°C. It could maintain the commodity quality for more than 20 d. Chilling injury would occur if mini cucumber was stored at 7°C. If stored for 10 d~12 d at 7°C, and then removed to ambient temperature, the fruit would appear water soaked spots as the chilling injury symptom. With the extension of storage time at chilling low temperature, the chilling symptoms of mini cucumber would be more serious with sunken spots, rotting, core browning, bitter taste, increased respiration rate and ethylene production, etc.2. Precooling combined with transportation at low temperature could effectively maintain the quality of mini cucumber. Compared to ambient temperature, the cucumber fruit showed better appearance, higher firmness and vitamin C level when transported at low temperature(13°C), while precooling combined with transportation at low temperature could maintain the pulp firmness, green peel color and vitamin C level. Of all the packaging treatments with low-temperature transport, the precooling combined with carton packaging could most maintain the pulp firmness, appearance and vitamin C level. Considering ambient-temperature transport, precooling combined with foam box sealing packaging showed the best effect. However, once the logistic at ambient temperature exceeded 2 days, the cucumber tended to generate off flavor. In all, precooling and transportation at 13°C with either carton packaging or foam box sealing packaging could effectively extend the storage time of mini cucumber during logistics at ambient temperature, but the transportation time should not exceed 2 days.3. The full-length cDNA sequences of 11 genes, named as MAPK1, MAPK4-1, MAPK4-2, MAPK6, MAPK7, MAPK9-3, MAPK13, MAPK19, MAPK20-2, BADH, P5 CS, related to chilling injury were cloned from cucumber fruit(Genebank accession numbers: KM925149, KM925155, KM925150, KM925156, KM925151, KM925153, KM925154, KM925152, KM925157, KP645172, KP645173).4. Quantitative RT-PCR assay revealed that most MAPK, WRKY, P5 CS and BADH genes were up-regulated upon chilling, while some MAPK and WRKY genes may have irritable responses to chilling.5. Yeast two-hybrid assay revealed that MAPK7 could physically interact with WRKY2 and WRKY23.