Introduction. Pomegranate fruits (Punica granatum L.) are chilling-sensitive crops. Materials and methods. Pomegranate fruits were treated with calcium chloride and spermidine, alone or in combination, by normal dip and vacuum infiltration methods. The treated fruits were stored at 2 °C for 4 months. At the end of the storage period, samples were held for 3 days at 20 °C, then the qualitative constituents were evaluated. Results and discussion. Treated fruits exhibited less weight loss and higher juice content than control fruits. Non-treated fruits developed chilling injury manifested as an increase in K+ leakage and polyphenol oxidase activity. Calcium chloride and spermidine treatments resulted in lower soluble solid content, but some fruits showed higher titratable acidity. All treatments significantly increased ascorbic acid content. The pH of aril juice in treated fruits was lower than that of non-treated fruits, probably due to higher titratable acidity. Total antioxidant activity and total phenolic content increased in treated fruits. In our study, a correlation was observed between total phenolic content and total antioxidant activity. Conclusion. The treatments applied in our experiments maintained overall quality of pomegranate fruits during long-term storage. Postharvest application of calcium and spermidine either alone or in combination could ameliorate adverse effects of low temperature on pomegranate fruit quality during cold storage. Vacuum infiltration was as effective as the normal dip method. However, normal dip is a simpler and faster treatment method.

Introduction. After harvest, litchi fruits (Litchi chinensis Sonn.) rapidly lose their bright red skin color. Peel browning of harvested litchi fruit has largely been attributed to rapid degradation of red anthocyanin pigments associated with the oxidation of phenolic compounds by polyphenol oxidase (PPO) and/or peroxidase (POD). An anthocyanase has been also identified in litchi peel. Our work aimed at characterizing two specific litchi varieties that differ greatly in their color and browning behavior. Materials and methods. The anthocyanins, polyphenol oxidase (PPO), peroxidase (POD) and anthocyanase in the pericarp of two litchi cultivars, Kwai May and Wai Chee, grown in Reunion Island and Spain, respectively, were studied. Results and discussion. The qualitative composition of major anthocyanins (cyanidin-3-rutinoside and cyanidin-3-glucoside) was identical for the two cultivars studied, but, quantitatively, the variety Kwai May had a lower concentration than Wai Chee (64% less) of cyanidin-3-rutinoside. This component represented more than 90% of total anthocyanins in both cultivars. The activity of PPO was 6 times greater in the variety Kwai May than in Wai Chee and the activity of POD 30 times greater. The activity of POD was greater than that of PPO in both varieties. These differences help to explain the different behaviors of the cultivars during subsequent postharvest studies.

Introduction. Biennial bearing and malformation are the two present problems of mango which are threatening the very existence of a global mango industry in India. Many factors are closely associated with these problems but, presently, those really responsible are not known exactly. Polyphenol oxidase (PPO) plays vital roles in higher plants and, hence, its activity was measured in swollen buds at panicle initiation in regular and biennial bearing mango cultivars to establish a relation between the PPO activity and the flowering behaviour or the malformation incidence. Materials and methods. Six regular (Sensation, Eldon, Tommy Atkins, Amrapali, Neelum and Bangalora) and six biennial bearing cultivars (Langra, Chausa, Edward, St. Alexandrina, Extrema and Bombay Green) were studied. PPO activity was measured in fully swollen buds by preparing a crude enzyme extract at 4 °C. Catecholase activity was measured by using 4-methyl catechol (4-MC) as the substrate, while 4-methyl phenol (p-cresol) was used for cresolase. Results and discussion. Both catecholase and cresolase activities were higher in the swollen buds in the year 2000 than in 1999. Regular bearers exhibited low PPO activity and showed the higher incidence of malformation as compared to the biennial bearing cultivars.Whatever their type of production, cultivars exhibited significant variations in PPO activities and malformation incidence. Conclusion. A strong negative correlation between PPO activity and number of panicles, and PPO activity and malformation incidence, suggests that the PPO activity is inversely related to both flowering and malformation incidence in mango.