Effects Of Different Processing Methods On The Stability Of Bioactive Substances In Cherries

Cherries are rich in a variety of bioactive substances with high nutritional value.However,cherries are prone to softening,browning and rotting during transportation and storage.Therefore,extensive processing methods have been developed to extend their shelf-life.In the market,the heat treatment of fruits and vegetables into shelf-stable jams and purees is one of the most common ways of processing.As a non-hot processing technology for sterilization and inactivation of microorganisms,high hydrostatic pressure treatment plays an important role in the storage of fruits and vegetables.At present,there are few studies on the effects of heat treatment and high hydrostatic pressure treatment on bioactive substances in cherries.In this study,cherry jams were processed at different temperatures(65℃,80℃ and 90℃)to observe the effects of temperature on the stability and quality of nutrients in cherry jams.On this basis,the changes of content and antioxidant capacity of the bound polyphenols after treatment of cherry purees at different temperatures(65°C,80°C and 90°C)were analyzed,and the effects of removing the bound polyphenols on the structure of cherries and fruit purees were observed from multiple angles.Dietary fiber and polyphenols are linked in a covalent and non-covalent manner,and the non-covalent bonds are affected by high hydrostatic pressure treatment.The topics further explored the effects of high hydrostatic pressure treatment on the content and structure of dietary fiber-bound polyphenol adducts in cherries,and analyzed the structural changes of dietary fiber-bound polyphenols adducts before and after removing the bound polyphenols by a variety of characterization methods.(1)When cherries were processed into jam at different temperatures,the comparisons of bioactive substances,enzymes and rheological properties among cherries and jams were analyzed.The content of total ascorbic acid(TAA)and anthocyanins decreased after the cherries were heat processed into jam,and the contents were the highest at 65℃.Processing temperature at 65℃ significantly increased the content of total phenolics(p <0.05),and there was no difference between cherries and jams processed at 80℃ and 90℃.The jams processed at 65℃ had better color and could form a stable gel.Furthermore,no polyphenol oxidase(PPO)and peroxidase(POD)activities were detected in cherry jams,which was beneficial for storage.Despite reducing bioactive substances,jams processing maintained these compounds.Especially when the temperature of processing was 65℃,it showed better advantages in hot processing.(2)When cherries were processed into purees at different temperatures,the effects of bound polyphenols on antioxidant capacity and structure of cherries during heat treatment were investigated.The content of bound polyphenols in cherry purees showed an increasing trend with the increase of temperature.The heat treatment of cherries enhanced the antioxidant capacity of bound polyphenols.The structure of cherries did not change significantly after alkaline hydrolysis treatment,which was observed by scanning electron microscopy(SEM).The analysis by infrared spectroscopy showed that the treatment of alkaline hydrolysis could remove the bound polyphenols.The results of differential scanning calorimetry(DSC)showed that the thermal stability of cherries and purees decreased after the removal of bound polyphenols,and the thermal stability of 90℃purees was better than that of cherries.The results of X-ray diffraction showed that the removal of bound polyphenols caused the disintegration of amorphous hemicellulose.(3)When cherries were processed by high hydrostatic pressure treatment,the content of dietary fiber was determined,and the content of bound polyphenols and structural characterization in insoluble dietary fiber-bound polyphenol adducts(IDF-BPA)was studied.High hydrostatic pressure treatment increased the content of dietary fiber,but reduced the content of bound polyphenols in IDF-BPA.The structure of IDF-BPA in cherries was broken after the removal of bound polyphenols,but the microstructure of cherries had not changed significantly after high hydrostatic pressure treatment.The results of confocal laser scanning microscopy(CLSM)and infrared spectra confirmed that bound polyphenols of IDF-BPA were removed by alkaline hydrolysis.The result of DSC showed a decrease in thermal stability after the removal of bound polyphenols from IDFBPA and an increase in the stability after high hydrostatic pressure treatment.The results of X-ray diffraction found that the insoluble dietary fiber belonged to the cellulose type I,and the crystallinity of IDF-BPA increased after the removal of bound polyphenols.