Effcts Of Controlled Atmosphere And Antistaling Reagents Treatments On Quality And Physiological Mechanism Of Fresh Walnuts

At present,due to rich nutrition and special flavors,wet-fresh walnuts have increasingly increased market demand and prices.However,storage time still fails to meet the increasing market demand for fresh walnuts at long-term supply due to significant mildew at post-harvest.Controlled atmosphere technology and antistaling treatments have certain preservation effect on fruits and vegetables,but there is no report on wet fresh walnuts.In order to effectively solve the mold problem at post-harvest,'XiFu NO.1'wet-fresh walnuts are treated with different O₂/CO₂ ratios,suitable O₂/CO₂ ratio treatment,antistaling treatments and a combination of both.The effect of CA on the quality and physiological mechanism of wet-fresh walnuts are analyzed.These will provide theoretical support and the best parameters for application of CA in wet-fresh walnuts.The trial includes the following main results:?1?'XiFu No.1'wet fresh walnuts treated with 8 different O₂/CO₂ conditions?including air control?were stored at 10L glass bottles at 0±1?,then sensory quality?mildew rate,seed coat and kernel colors,seed coat stripping degree,brittleness and flavor?and nutrient quality?soluble sugar,soluble protein and fat content?were analyzed.The results showed that high CO₂ concentration?exceed 25%?inhibited significantly mildew rate but affected the physiological activities of kernel,resulting in odor and loss of sensory flavor.The study also found that 2%O₂+25%CO₂ maintained better sensory quality,soluble sugar and soluble protein content of kernel closed to harvest value and has the highest fat content.Finally,2%O₂+25%CO₂ was selected as the suitable gas parameter.?2?'XiFu No.1'fresh walnuts treated with air?CK?,200mg/kg sodium diacetate?SDA?,50mg/L chlorine dioxide?Cl O₂?,2%O₂+25%CO₂?CA?,CA+SDA and CA+ClO₂,respectively,were stored in 10L glass bottles at 0±1?,then sensory quality,nutrient quality,lipid quality and physiological indicators were analyzed.The results showed that all of CA,CA+SDA and CA+ClO₂ treatments effectively inhibited the mold growth and mildew time was delayed to135d.The mildew rate in CA+ClO₂ treatment was significantly lower than those of the other two treatments.The CA+ClO₂ treatment maintained better color of the shell and seed coat and the firmness of kernel.?3?Walnuts treated with CA+ClO₂ kept the highest fat content,however crude protein and soluble sugar content were lower than those of CA+SDA treatment.The AV,PV and CV of kernel in CA+SDA treatment were lower than those of CA+ClO₂ treatment.But there was no significant differences in CV between CA+SDA and CA+ClO₂ treatments,and PV of walnuts treated CA+ClO₂ almost closed to the harvest value.?4?All of CA,CA+SDA and CA+ClO₂ treatments promoted POD activity and inhibited PPO activity.higher POD activity,lower PPO activity were found in walnuts treated with CA+ClO₂,in which the highest levels of total phenol,melatonin and phytic acid were found.In conclusion,Considering on the differences in sensory,nutrient and lipid quality and physiological indexes of wet fresh walnuts at 6 treatments during cold storage,it was determined that CA+ClO₂ was the optimal treatment for this study.