Effects Of Storage Temperature And Drying On Polyphenols,Pectin And Gel Properties Of Hawthorn

Hawthorn,belonging to a medicinal and edible fruit,is a kind of specialty in China,which has many varieties,large yield,concentrated harvest period,high nutrients content and good gel performance.At present,the main utilization ways of hawthorn in China are fresh-eating,canning,pharmaceutical and primary processing of gel products such as hawthorn slices and hawthorn gels.The key to realize the quality and efficiency utilization of hawthorn is to satisfy annual supply of superior hawthorns with low storage cost.In this study,the differences of hawthorn varieties were evaluated by the indexes,i.e.,physiological quality,nutrient,phenolics,gel property and antioxidant activity.The effects of storage temperature and drying techniques on nutrients and processing quality were also investigated.A product of hawthorn and other fruits complex was developed in order to provide data reference for raw material selection,storage and deep-processing,which could further promote the healthy and continuous development of hawthorn industry chain.The main research results are as follows:(1)The physiological qualities and nutrients of hawthorn varieties such as Jinxing,Mianqiu and Fuxi hawthorn were investigated compared with the commercial hawthorn as the control(CHF).The results showed that the content of lipid in Mianqiu was higher,the contents of total sugar and reducing sugar in Jinxing were higher,and the contents of total acids in Fuxi hawthorn were higher.The contents of total phenolics and flavonoids ranking from high to low was Jinxing,Mianqiu,Fuxi hawthorn and CHF.No significance was seen on emulsifying activity among these four samples(p > 0.05).The emulsion stability of Mianqiu was higher than the other three samples,and the emulsion stability of Fuxi hawthorn,CHF and Jinxing successively decreased.(2)The difference of antioxidant activities and gel properties among hawthorn varieties were compared.The results showed that the contents of total acids and pectin of Mianqiu,which accounted for 14.55% and 14.24%,respectively,were higher than those of Jinxing.The contents of crude protein,total starch,reducing sugar,ash and total dietary fiber of Jinxing were higher than those of Mianqiu.For the pasting property,the setback value of Jinxing was higher than that of Mianqiu,indicating a lower starch retrogradation resistance,a higher emulsion stability and antioxidant activity.(3)The effects of temperature on physicochemical qualities,phenolics,antioxidant activities and oxidase activities of hawthorns during storage were studied.The results showed that the moisture,hardness,total sugar,reducing sugar,total acids and color of hawthorns stored at 25 °C gradually decreased,which showed a greater decline compared with the other two treatments.Hawthorn stored at 25 °C appeared to be perishable from the 30 th day.The decrease of these indexes for hawthorns stored at 4 °C slowed down and the storage time exceeded 60 days.These indexes of hawthorns stored at-18 °C showed the minimum variation.The contents of ascorbic acid,EPP(extractable phenolic)and flavonoids also gradually decreased during storage and the decreasing rate ranking from high to low was25 °C,4 °C,-18 °C.HPP(hydrolyzable phenolic)content during storage showed no significant difference and was relative stable.NEPA(non-extractable proanthocyanidins)content gradually increased and the increasing rate was 25 °C > 4 °C >-18 °C.FRAP(ferric reducing antioxidant power)values of EPP and HPP in hawthorns stored at 25 °C decreased at the beginning and then increased,while the DPPH-RSC(DPPH radical scavenging capacity)of NEPA gradually increased.As for FRAP values and DPPH-RSC in hawthorns stored at4 °C,no significant difference was shown within 60 days.PPO(polyphenol oxidase)and POD(peroxidase)activities increased at the beginning and then decreased at 25 °C,and the maximum value was reached on the 30 th day.However,these enzymatic activities gradually reduced at 4 °C and-18 °C with no significant difference.(4)The processing technique and quality characteristics of hawthorn and fruit composite gels were studied through mixture between hawthorn pump and fruits including blueberries,apricots,apples and cherries.The results showed that the hardness and rupture distance of hawthorn gels firstly decreased,and subsequently increased within 6 h.The drying duration had no significance on the color of hawthorn gels(p > 0.05).A better product of hawthorn and fruit composite gel was obtained,with the hawthorn addition of more than 50% at 60 °C drying for 6 h.