关键词: 石榴果实, 保鲜剂, 采后生理, 贮藏品质, 病原菌

Abstract: 【Objective】 Several unexpected phenomenon can be easily occurred on postharvest pomegranate fruit such on peel browning, aril deterioration, softening, decay and so on during storage. The storage period of pomegranate fruit is short, its quality becomes poor and the commodity value drops after storage. The best formula of multiplex antistaling agent for pomegranate fruit was optimized. In order to provide the theoretical basis and technical parameters for pomegranate storage, the effects of antistaling agent on postharvest physiology, storage quality and storage diseases of pomegranate fruit were studied in this study. 【Method】‘Jingpitian’ pomegranate fruit was used as raw material. The composition proportion of multiplex antistaling agent was optimized by orthogonal experiment, and the best formula was determined by physiological changes and sensory evaluation. The pomegranate fruit coated with multiplex antistaling agent was stored under the conditions of temperature (1.0±0.5)℃, relative humidity (RH) 90%-95%. The fruit without antistaling agent treatment was used as the control. The changes of fruit respiration rate, relative conductance rate, firmness, peel polyphenoloxidase (PPO) activity, peroxidase (POD) activity, catalase (CAT) activity, superoxide dismutase (SOD) activity and arils soluble solids content, total sugar content, titratable acidity content of each treatment were measured during storage. Moreover, the browning index, decay index, weight loss rate and commodity fruit rate were calculated in different periods of storage. The sensory characteristics such as taste, color and smell of the fruit were overall evaluated. The storage disease pathogenic fungi were identified by Koch’s validation, ITS sequence analysis and morphological characteristics. The inhibition rate, semi lethal concentration (EC₅₀) and minimal inhibitory concentration (MIC) of multiplex antistaling agent on pathogenic fungi of pomegranate fruit were also determined during storage. 【Result】 The multiplex antistaling agent was prepared by 7 types of components including chitosan oligosaccharide, natamycin, glucono-δ-lactone, citric acid, ascorbic acid, sodium hexametaphosphate and sodium caseinate. The results generally showed that the coating treatment of multiplex antistaling agent could reduce the fruit respiration rate, slow down the rise of the peel browning index and relative conductance rate, inhibit the activities of PPO and POD, keep the activities of CAT and SOD at a high level, maintain the soluble solids content, titratable acidity content, total sugar content of arils and fruit firmness well, decrease the fruit decay index and weight loss rate, improve the commodity fruit rate, and keep the good sensory quality of pomegranate fruit. Botryotinia fuckeliana and Penicillium spinulosum were the pathogenic fungi that led to main diseases during storage. Multiplex antistaling agent could inhibit the growth of pathogenic fungi obviously. The storage life could reach up to 160 days with the browning index being 0.21, decay index being 0.16 and commodity fruit rate being 90.2%. After long-term storage, the pomegranate fruit had a colorful appearance and glassy arils and its sensory quality was excellent and the fresh-keeping effect was perfect.【Conclusion】 The optimum formula of multiplex antistaling agent included chitosan oligosaccharide 0.2 g, natamycin 0.02 g, glucono-δ-lactone 0.08 g, citric acid 3 g, ascorbic acid 2 g, sodium hexametaphosphate 0.1 g, and sodium caseinate 0.6 g. All the components were mixed and dissolved in distilled water to prepare the 160 mg·L^-1 antistaling agent. After pre-cooling at (5.0±0.5)℃ for 3 days, the pomegranate fruit was immersed in the above mentioned antistaling agent for 10-20 s, then was taken out and dried naturally, then was packed with plastic bag individually, and then was stored at (1.0±0.5)℃ and RH 90%-95%.

Key words: pomegranate fruit, antistaling agent, postharvest physiology, storage quality, pathogenic fungi