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Essaid Ait Barka, Siamak Kalantari and Joseph Arul

Fresh fruit and vegetables are highly perishable because of their active metabolism during the postharvest phase. Previous studies showed that hormic dose of UV cause a delay in the senescence of tomato fruit by about 7 days. The objective of this study was to elucidate whether UV acts on the cell membrane in producing the phenomenon of delayed senescence, since it is known that UV radiation can provoke photooxidation of membrane lipids. Membrane lipid peroxidation was studied in tomato fruit (Lycopersicon esculentum Mill cv. Trust) treated by hormic UV dose, and was followed by assaying products of lipid oxidation during the storage period. We observed the production of lipofuscin-like compounds, malondialdehyde, aldehydes, pentane, ethane, and hydrogen peroxide within few days of the treatment. An increase in the efflux of electrolytes (total, potassium, and calcium) was also observed. An immediate increase in the level of these products of oxidation supports the hypothesis that UV radiation induces membrane lipid peroxidation. However, beyond 5 to 7 days after treatment, the production of oxidation products and electrolyte leakage were lower than the control fruits. Thereafter, the level of products of lipid oxidation associated with senescence was higher in control fruits than in treated ones. Results suggest that the initial oxidation stress by the exposure to UV led to biochemical reactions inducing the production of stress compounds, such as polyamines, which are non specific antioxidants. Consequently, a delay in the senescence was observed.

Open access

Mohsen Hatami, Siamak Kalantari, Forouzandeh Soltani and John C. Beaulieu

Dudaim melon (Cucumis melo Group Dudaim) is a unique edible melon for which few postharvest physiology studies have been conducted. To investigate the postharvest behavior of dudaim melon, two cultivars (Zangi-Abad and Kermanshah) were planted, tagged at anthesis, and harvested at two maturity stages: 21 and 28 d after anthesis (DAA). Harvested fruit were stored at 5 or 13 °C for up to 3 weeks and various quality parameters including color, firmness, titratable acidity (TA), total soluble solids (TSS), weight loss, chilling injury (CI), ethylene production, protein content, glucose content, fructose content, sucrose content, and maltose content were assessed during storage. After 3 weeks of storage at 13 °C, early-harvested fruit (21 DAA) had relatively similar color values (L*, lightness; a*, green–red tones; b*, blue–yellow tones) and TA compared with late-harvested fruit (28 DAA); however, some quality traits, such as TSS, were not similar. Ethylene content decreased initially after harvest and then started to increase during storage at 13 °C. For most treatments, glucose and fructose contents decreased whereas sucrose and maltose contents increased with advancing maturity. Increased ethylene production, in concert with color development at 13 °C, similar to ripe fruit, and the changing balance of measured mono- and disaccharide sugars in harvested fruit likely indicates ‘Kermanshah’ is climacteric. Results for ‘Zangi-Abad’ were not as definitive. Dudaim melon fruit can be harvested at an optimum stage of maturity, similar to known climacteric melon fruit, and then allowed to ripen at proper storage temperatures before consumption. Based on the results of this study, we recommend that harvest at 21 DAA and storage at a nonchilling temperature such as 13 °C are the optimal stage and temperature for long storage purposes.