Study On Physiological Mechanism Of Chilling Injury And Pretreatment Measures Of Postharvest Yam

Yam has high nutritional value and is considered to be a homologous plant of food and medicine.It is prone to chilling injury during long-term low temperature storage,Causing loss of its nutritional value.At present,there are few reports about the cold damage of long yam tuber at home and abroad.In this study,used Hebei yam as a test material,and the change of the index of chilling injuries,electric conductivity,antioxidant enzymes activity were analyzed.To investigate the effects of different storage temperature of chilling injury of yam occurrence mechanism of technologies and quality;To investigate the effects of Chitosan and UV-C treatment on chilling injury and quality of Yam during storage at 1?,this research Yam treated with Different concentration of chitosan and different doses of UV-C irradiation treatment,and the change of the index of chilling injuries,soluble solids content,MDA,electric conductivity,antioxidant enzymes activity were analyzed,it provides a theoretical basis for mitigating the cold damage of long yam after harvest.The results showed that:1.The yam chilling injury appeared relatively late,the yam show symptoms of chilling injuries at1? and 3? on the 20 d of storage;as the storage time is prolonged,the chilling injury extent was more severity when the temperature was lower,after storage to 30 d,the chilling injury rate at 1? is remarkably higher than at 3?;yam stored at 5? did not occur chilling injury during the whole storage period.The relative electrical conductivity and MDA content of Chilling injury occurred were significantly lower than not,chilling injury rate are positively correlated with conductivity and MDA content,but POD,SOD and CAT activities were significantly higher than not injury.The yam occurs chilling injury at 1? and3?,so yam storage temperature should not be less than 5 ?.2.This research Yam treated with 0.5%,1.0%,1.5% of chitosan and 4 ? 6 ? 8 KJ·m-2 of UV-C irradiation treatment,1.0% chitosan and 6KJ·m-2UV-C treatment can significantly reduce the chilling injury index of yam,and maintained the high level of total soluble solids content,inhibit the accumulation of and the increase in membrane permeability.Effectively maintain the integrity of the cell membrane and reduce the occurrence of chills.3.The optimum concentration of chitosan was 1.0%and the optimal irradiation dose for UV-C was 6KJ·m-2 for maintaining the quality of long yam tuber.Under this condition,chitosan?UV-C irradiation and chitosan combined with UV-C could significantly reduce chilling injury index and chilling injury incidence,inhibit the accumulation of malondialdehyde(MDA)and the increase in membrane permeability,Protective film structure integrity,significantly lower the of polyphenol oxidase(PPO)activity,and maintained the high level of total soluble solids content and peroxidase(POD).It was visible that these results indicated that three kinds of treatment can markedly alleviate the chilling injury symptoms and extend the storage time of yam,chitosan combined with UV-C is the most effective against chilling injury.This study will provide theoretical basis for alleviation of chilling injury of yam.