Chlorine dioxide and sodium diacetate treatments in controlled atmospheres retard mold incidence and maintain quality of fresh walnuts during cold storage

Abstract Fresh walnuts deteriorate and develop mold rapidly during cold storage. The effects of chlorine dioxide (ClO2) and sodium diacetate (SDA) in controlled atmosphere (CA) storage on deterioration of fresh walnuts have been investigated. 'Xifu No.1′ fresh walnuts were treated with air (Control), air +200 mg kg−1 sodium diacetate (SDA), air +50 mg L−1 chlorine dioxide (ClO2), 2 % O2 + 25 % CO2 (CA), CA + SDA and CA + ClO2 and then stored at 0 ± 1 °C for 135 d. Mold incidence, nutrient quality, oil quality and physiological indices of the walnuts were analyzed. The results showed that CA, CA + SDA, CA + ClO2 treatments delayed the development of mold, increased POD activity while decreasing PPO activity, and maintained quality of fresh walnuts in comparison to air treatments. CA + SDA and CA + ClO2 maintained higher melatonin content and lower peroxide and carbonyl values of fresh walnuts than CA treatment alone, but no difference in mold incidence were detected between CA and CA + SDA treatments. Overall, CA + ClO2 was the optimal treatment and kept quality of fresh walnuts for 135d at 0 ± 1 °C, with the lowest mold incidence (5 %), the highest firmness and contents of fat and melatonin, as well as the maximum POD activity.