Impact of pulsed light on mechanical properties and structure of strawberry (Camarosa var.)

GÓMEZ, PAULA L.; DUARTE, FERNANDO; CASTRO, MARIA AGUEDA; ALZAMORA, STELLA M.

Florianópolis

Workshop; International Nonthermal Food Processing Workshop; 2013

FIESC-SENAI

Strawberry has a high softening rate and is very susceptible to fungal attack, which limits its storage life. It is of interest to develop and improve preservation techniques to reduce post-harvest losses. Pulsed light (PL) treatment has emerged in recent years as an alternative method for surface decontamination of foods. The effect of pulsed light (PL) dose on mechanical behavior and micro and ultrastructure of strawberries was investigated. The PL treatment was performed with a Xenon RS-3000B Steripulse-XL system, which generated high intensity pulsed light of polychromatic radiation (200 to 1100 nm). Samples were exposed to irradiation for 10 to 40 s at 10 cm from the lamp (fluence ranging between 11.9 and 47.8 J/cm2). Irradiated strawberries were compared to a control (non-irradiated fruit) at 0 day and after 8 days of storage at 5 ºC. From the force-displacement curves obtained from puncture test, the maximal force in the skin rupture point and the mechanical work up to rupture point were analyzed. 25 replicates were performed for each treatment. Experiences were made in duplicate. Light and electronic transmission microscopy observations of tissues were made after processing and storage. After treatments, PL-treated strawberries did not show significant differences in the mechanical parameters compared to non-treated fruits. However, irradiated strawberries kept firmer than control after 8 days of storage, at all doses tested. In the microscopic observations, PL-stored treated tissues appeared with outer tangential and mesocarp cell walls markedly more stained than control samples. This improvement in tissue structure could explain, at least partially, the retention of firmness observed in stored treated strawberries. Results suggest that PL treatment could help in maintaining firmness of strawberries during refrigerated storage.