Combined effects of ascorbic acid and chitosan on the quality maintenance and shelf life of plums

The combined effects of chitosan (CTS) and ascorbic acid (AsA) on the quality maintenance and shelf life of harvested plums (Prunus salicina Lindley. cv. 'Sanhuali') were investigated. The fruits were treated with aqueous solutions including water (control), 40.0 mM AsA, 1.0% CTS, and 40.0 mM AsA combined with 1.0% CTS; all samples were stored at 5 +/- 1 degrees C and 90 +/- 5% relative humidity for 20 days. Fruit firmness, weight loss, respiration rate, soluble solids content, titratable acidity, ascorbic acid, color characteristics (L*, C*, and h), and anthocyanin contents were measured, along with the specific activities for superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), polyphenol oxidase (POD), polygalacturonase (PG), pectin methylesterase (PME), and phenylalanine ammonia lyase (PAL). The results showed that AsA and CTS combined maintained tissue firmness, inhibited an increased respiration rate, and decreased color changes, as compared with the control. The efficiency was better for the combined MA and CTS treatment than AsA or CTS alone. The inhibition of softening was associated with decreased PME and PG activities. Furthermore, plums treated with the AsA and CTS combination also exhibited a significantly lower PPO activity and significantly higher SOD, POD, and CAT activities throughout the storage period. During postharvest storage, anthocyanin synthesis was significantly inhibited with the combination of AsA and CTS and was accompanied by decreased PAL activity. Moreover, the production of superoxide free radicals (O2(center dot-)) and malondialdehyde (MDA) was significantly decreased in the treated fruits. These results clearly indicated that the 40.0 mM AsA and 1.0% CTS treatment could be an effective means to contribute to the shelf-life extension and quality maintenance of plums during storage. (C) 2014 Elsevier B.V. All rights reserved.