Mechanism Of Cold-induced Sweetening In Potato During Postharvest Storage

Potato has been widely consumed as staple food and snacks,which contains plenty of vitamins and minerals.Potato tubers are used to store at low temperature which can suppress sprouting and control the occurrence of diseases.However,low temperatures also lead potatoes easier to suffer from cold-induced sweetening,which has a negative effect on food processing.It has been reported that cold-induced sweetening leads to unpleasant dark color and unacceptable bitter flavor product as a result of Maillard reaction in the high temperature frying process.What's more,it can also promote the formation of acrylamide identified as “probably carcinogenic to humans”.Hence,the aim of this research was to evaluate UV-C,gibberellin and s-carvone treatments on controlling sugar accumulation in potatoes and investigate the possible mechanism of cold-induced sweetening.The mainly findings are as follows:Through different temperature storage,it can be concluded that cold temperature can stimulate the occurrence of sweetening in potatoes to improve cold stress tolerance by regulating ADP-glucose pyrophosphorylase(AGPase),granule-bound starch synthase(GBSS),b-amylase(BAM1/2),sucrose phosphate synthase(SPS),vacuolar invertase(INV1)and invertase inhibitor(INH1)expression.UV-C treatment significantly decreased the reducing sugars accumulation during the whole storage period,with 39% lower content than that in CK at 28 days of storage.UV-C treatment can down-regulate SPS and INV1 expression,causing a suppression of sucrose synthesis and hydrolysis.Thus,the cold-induced sweetening was alleviated by UV-C treatment.According to gibberellin and s-carvone treatment,we found that gibberellin can up-regulate the expression of BAM1/2 and UDP-glucose pyrophosphorylase(UGPase),and down-regulate the expression of AGPase,GBSS and INH1/2,which caused a reduction of starch synthesis rate and an increase of starch and sucrose hydrolysis rate.Thus it promoted the cold-induced sweetening in potatoes.In contrast,s-carvone can inhibit cold-induced sweetening through modulating GBSS and INH1/2.In conclusion,there are various of enzymes involved in cold-induced sweetening in potaotes,mainly including BAM1/2,AGPase,GBSS,SPS,INV1 and INH.From our results,UV-C,gibberellin and s-carvone can control the degree of cold induced sweetening in potatoes by modulating those related genes expression.Both of UV-C and s-carvone can be applied as sweetening inhibitors in potatoes during postharvest storage.