Research On Techniques For Controlling Postharvest Senescence And Predicting CO₂ Disorder Of Postharvest Garlic Scape

The senescence and CO₂ disorder in postharvest garlic scape not only result in reduction in the nutritional value of the garlic scape, but also cause great economic losses. In this paper, the key plant hormone to delay the senescence of garlic scape and its possible mechanism were determined by investigating the influence of removing the garlic involucre on the contents of lignin, endogenous hormone levels and the activity of senescence related enzymes in the tissue. The studies indicated the key endogenous hormone which inhibited the senescence of garlic scape. The effect of exogenous hormone on retarding the senescence was confirmed by using exogenous hormone to treat the garlic scape. Furthermore, the CO₂ disorder warning in garlic scape was found. The study aimed to control the CO₂ disorder and provide reliable technical support to enhance postharvest quality of garlic scape. The results showed that:1. The results showed that the treatment of removing the garlic involucre delayed the senescence of garlic scape and slow downed the increase in the lignin content. Furthermore, the activities of phenylalanine ammonia-lyase （PAL）, cinnamate-4-hydroxylase （C4H）, cinnamyl-alcohol dehydrogenase （CAD）,4-Coumaratc:Co A ligase （4CL） and peroxidase （POD） in treated garlic scape tissue were also reduced compared with control. The content of indole acetic acid （IAA） in treated garlic scape was significantly higher than control, but there were no obvious difference in gibberellic acid （GA3） and abscisic acid （ABA） between the treatment and control.2. The treatment with exogenous IAA inhibited the lignification and weight loss, and increased the contents of chlorophyll and ascorbic acid compared to control. The research concluded postharvest treatment with exogenous IAA could be applied to improve the quality and extend shelf-life of garlic scape for industry storage.3. The effect of treating with 100% CO₂ for short time on quality of garlic scape during shelf-life was studied. The quality indexes were determined at regular intervals. The results showed that, high CO₂ treatment not only maintained garlic scape water content, chlorophyll content and vitamin C content, but also inhibited the senescence and lignification of garlic scape.4. It treated with 20% CO₂,3% O2, and 77% N2 in the treatment, while it treated with 3% O2, and 77%N2 in control which simulated the cold production environment. Before CO₂ disorder in garlic scape, the electrolyte leakage, respiration rate and MDA content were lower than control, while Vc content and succinate dehydrogenase （SDH） activity were higher than control. But after CO₂ disorder in garlic scape, the content reversed. The ethanol and propanal in the treatment by the analysis of automated static headspace and GC-MS could be as the index of predicting CO₂ disorder in garlic scape. When carbonic acid, dimethyl ester occurred in treatment by the analysis of solid-phase micro-extraction method with GC-MS, the CO₂ disorder in garlic scape would impend.