Heat treatments delay ripening and postharvest decay of strawberry fruit

PEDRO MARCOS CIVELLO; MARTÍNEZ GA; CHAVES AR; AÑÓN MC

JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

American Chemical Society

Año: 1997 vol. 45 p. 4589 - 4594

0021-8561

Fully red strawberries (Fragaria x ananassa Duch., cv. Selva) were treated for 1 to 5 h at temperatures ranging from 39 to 50°C. After treatments, fruits were placed at 0°C overnight and then held at 20°C for 3 days. Most of the heat treatments improved strawberry shelf life, with best results obtained for fruit heated at 42°C and 48°C for 3 h. Heat treatments prevented fungal development and decreased the number of damaged fruits. These treatments were then used to treat strawberries at 50-75% red to analyze effects on firmness, surface color, anthocyanin content, polypeptide composition and protein synthesis. Softening rate and external color development was less in fruit heated at 48°C compared to the control, while treatment at 42°C did not significantly affect these parameters. However, both treatments reduced anthocyanin accumulation and PAL activity relative to the controls. In addition, treatment at 48°C for 3 h reduced protein synthesis, but this effect was partially reversed after holding fruits at 20°C for 48 h. Heat treatments (42°C and 48°C) led to the accumulation of five heat shock proteins of 88, 76.5, 69, 19 and 17 kDa. In addition, treatment at 42°C induced the synthesis of a 22 kDa polypeptide that was not observed in the 48°C treatment. Fruits treated at 48°C continued the synthesis of 69, 19 and 17 kDa polypeptides even after 48 h at 20°C. According to these results, the lower fungal development and the slower ripening rate shown by heat-treated fruits suggest that this physical method could be useful to extend the postharvest shelf life of strawberry.   Key words: Strawberry; heat treatment; ripening; postharvest decay; heat shock protein; protein synthesis.