Effect Of Controlled Atmosphere On The Preservation And Postharvest Physiology Of Green Walnut Fruit

Fresh walnut (Juglans regia L.) product is a newly immersing consumption trend. Itresulted in the investigation and application of fresh walnut storage technology a hot focus.Using green walnut fruit of QingXiang as material, the influence of O2、CO2and combinedtreatment on postharvest physiology of green husk and kernel quality of storage walnut werestudied. Also, by comparing the effect of different O2/CO2composition on walnut physiologyand kernel quality during storage, the optional atmosphere parameters for green walnutpreservation was screened. Main results were as following:(1) During storage, fruit firmness, water content of green husk and kernel were alldecreased under5%O2、9%CO2and combined treatment (5%O2+9%CO2) conditions, with(5%O2+9%CO2) giving the smallest decline. Total phenol content of kernel increased duringearly storage phase and then decreased, total antioxidant capacity (FRAP value) rosethroughout the storage, with9%CO2giving the sharpest increase.5%O2promoted appearanceof two respiration peaks,9%CO2enhanced the value of the first respiration peak, promotedappearance of the second peak, increased fruit respiration intensity after harvest.(2) In comparison with control,5%O2could reduce ascorbic acid (ASA) content,increased ascorbate peroxidase(APX) activity, reduced ascorbic acid reductase (DHAR)activity, showing that oxidation process was greater than reduction in walnut green husk;9%CO2and (5%O2+9%CO2) maintained a high level of ASA, controlled APX activity,maintained DHAR activity, indicating that ASA reduction was greater than oxidation at thistime.9%CO2also increased total phenol content, improved FRAP value, while it inhibitedperoxidase (POD)、polyphenol oxidase(PPO)、phenylalanine ammonia lyase(PAL）activity,showing that reduction of total phenol was quicker than destroyed;5%O2and (5%O2+9%CO2)showed that total phenol content and FRAP value were low, POD and PAL activity were high,it showed that reduction of total phenol was slower than destroyed in this two groups. Insummary, total phenol、ASA and total antioxidant capacity were the result of O2and CO2coordinated action.(3) Compared to control, all treatments superoxide dismutase (SOD) activity had decreased, with CO2giving the sharpest decline. Early12days in storage period, exceptcontrol catalase (CAT) activity decreased during early storage and then increased, reached thepeak at12th days, another three groups were all decreasing, after12days, CAT activity ofthree groups were increasing and they were higher than control.5%O2significantly increasedfruit decay rate and MDA content;9%CO2significantly reduced decay rate and browning rate;(5%O2+9%CO2) could delay the increasing rate of decay rate in late storage.(4) The experiment studied sensory quality of fresh walnut、soluble protein、acid value、peroxide value、oil content、malondiadehyde (MDA) and the impact of fresh walnut fruits instorage70d and110d. The result showed that:（5%O2+6%CO2）was the best group in ninecombinations, it could guarantee fresh walnut kernel flavor, maintained the soluble proteincontent, could significantly reduce fruit decay rate and decay rate index, we initially selectedthis gas parameter as suitable storage atmosphere in green walnut fruit.