Effect Of Different Pre-cooling Treatment On The Characteristics Of Blueberry Fruit During Storage

One of the most important factors causing the postharvest rot of fruits and vegetables is the respiratory metabolism,not only consuming nutrients in fruits and vegetables but also producing a lot of breathing heat that will further strengthen respiration and lead to speed up rate of rotting.The process of precooling for rapid removal of field heat is the good way to solve this problem.The experiment selected"Tifblie" blueberry as experimental material,treated by cold room precooling,forced-air precooling,vacuum precooling and Freezing precooling,kept at non-precooling served as a control.All experiments at 0? storage conditions.Precooling as a valid method for effectively slowing down the decreasing of quality and extending the shelf life of blueberry was demonstrated,by observing related indexes of postharvest quality,anti-oxidation metabolism and energy metabolism.The main findings are as fellows:1.The effects of pre-cooling treatment on the quality ofbhieberry during storage:with the increase of storage time,the decay rate and the weightlessness rate respectively accelerated after slowly rising first,ascorbic acid content constantly declined,the trend of soluble solid content went up slightly then declined.These changes of blueberry fruit during storage lead to a decline in its commercial qualities and shorten the shelf life.The results showed that rot rate and weightlessness rate of blueberry after treatments of precooling both increased slower than blank control group,the decreasing speed of ascorbic acid and soluble solids content were slower.The effect of treatment of forced-air precooling was the most significant It could be seen that precooling of blueberry fruit significantly inhibited the decline of quality bidicators during storage.2.The efifects of pre-cooling treatrent on the active oxygen metabolism and membrane lipid peroxidation of blueberry during storage:the experimental results show that,because of the effect of blueberny fruit ripening and stress of environmental factors during its storage,lipoxygenase activity and peroxidase activity both declined after rising first.The peroxidase enzyme activity peak of blank control group was obviously earlier than blueberry after treatments of precooling,the lipoxygenase activity peak appeared earlier than the other groups,and enzyme activity value was higher.This suggested that the precooling could effectively delay the ripening of fruit of aging,and enhanced its ability to resist adversity stress.Accumulation of hydrogen peroxide content and superoxide anion can directly or indirectly cause membrane lipid peroxidation damage.The rate of hydrogen peroxide content and superoxide anion content of blank control group were respectively 621.5mmol/g and 1827nmol/min · g,and ofthe group treated by forced-air precooling were 458.8mmol/g and 740.6nmol/,in·g.The results showed that the precooling could effectively reduce the accumulation of hydrogen peroxide and superoxide anion during storage,and delay the blueberry fruit membrane lipid peroxide process.Malondialdehyde is one of the important products of membrane lipid peroxidation,the content of which is the main index of the membrane lipid peroxide level.The blueberry treated by precooling maintained lower content of malondialdehyde than blank control group,explaining that precooling could effectively slow the membrane lipid peroxidation of blueberny fruit during storage.3.The effects of pre-cooling treatment on the energy metabolism of blueberry during storage:the experimental results show that the contents of ATP and ADP were on the decline,AMP was increasing constantly,and energy charge continued to decline.The decline of ATP and energy charge has a certain relationship with fruit browning,aging,disease resistance and chilling injury.Precooling could effectively reduce the energy chaige of blueberny,strengthening resistance off fruits.Of the pre coo ling unit operations on postharvest blueberry fruits could effectively slow the decline of fruit quality during storage,the forced-air precooling method worked best...