Fresh grapevine (Vitis vinifera L.) leaves: Postharvest biology and handling recommendations
Marita Cantwell, G. Hong, Karin Albornoz, M. Berlanga
Abstract
Developing grapevine leaves are harvested for the preparation of stuffed dolmas. Fresh leaves are preferred, but since they are perishable and can be harvested at ideal maturity for only a limited period, most leaves for dolmas are currently preserved. This research on fresh grapevine leaves (var. Thompson Seedless) was conducted over three seasons, and focused on their postharvest performance in relation to leaf maturity, respiration rates, storage temperature, water loss and packaging, and decay control. Appropriate leaf maturity for dolmas are leaves that are bright green and not yet fully expanded. The 4 leaf maturity stages that can be harvested commercially for dolmas are clearly delineated by differences in color, and corresponding color values and pigment concentrations. Sugar, acid, and phenolic concentrations and % dry weight vary little among the 4 maturity stages studied. Respiration rates of grapevine leaves (mature for dolmas) are moderate, about 350 µmol CO2 kg−1 h − 1 at 5 °C. Grapevine leaves can be stored for 4–8 weeks at 0 °C. A storage period of 1 month can be expected if they are stored in the range of 0–5 °C. Grapevine leaves can be stored below 0 °C but freezing injury occurs near -2.5 °C. Water loss at 8–10% is needed to reduce marketable quality (loss of gloss, leaf curling, browning). Botrytis decay is the major limitation to storage life and decay incidence varied from harvest to harvest. Decay is partially retarded by high CO2 atmospheres (10–15% v/v), but is more effectively controlled by hot water dips of 47.5 °C to 52 °C (15 to 9 min). Grapevine leaves harvested for dolmas do not show yellowing during aging or senescence when held below 10 °C.