Effect of Aqueous Ozone Treatment on Fungal Decay and Mechanical Properties of Strawberry Fruit

CONTIGIANI, E.; JARAMILLO-SANCHEZ, G.; CASTRO, M.A; GÓMEZ, P.L.; GARCIA-LOREDO, A.; NIETO, A.; ALZAMORA, S.M.

Chicago

Congreso; Institute of Food Technologist Annual Meeting 2016; 2016

Institute of Food Technologists

Storage life of strawberries is limited by fungal attack. The traditional use of fungicides to reduce postharvest losses has been questioned and the development of new preservation strategies is necessary. This work investigated the effect of aqueous ozone treatment on fungal spoilage, mechanical properties and structure of strawberries stored at refrigeration temperatures.Strawberries (Fragaria x AnanassaDuch cv. Albion) were immersed in ozonated water (3.7 ppm O3) in a bubble column (1.25 L) and treated at different times (5, 10 and 15 min) at 20±1ºC. Ozone-treated fruits were compared to controls (fruits without washing and fruits dipped in water bubbled with oxygen instead of ozone) throughout 12 days of storage at 5±1ºC. The presence of macroscopic fungal growth was daily visually inspected and the results were expressed as percentage of decayed fruit. Puncture tests and light microscopy observations were made after processing and at selected intervals of the storage period. From the force-displacement curves, the maximal force in the skin rupture point, the mechanical work up to the rupture point and the probe position at the rupture point (D) were analyzed. 40 replicates were performed for each condition. Mechanical data were analyzed by MANOVA.Strawberries exposed to ozone 5 min showed a decrease in fungal incidence during storage. After 12 days of storage, the percentage of infected fruits was about 25% lower compared to stored control fruits without washing or dipped in non-ozonated water. Higher treatment times did not allow reducing the number of infected fruits. Ozone-treated fruits and controls did not show significant differences in the mechanical behavior throughout storage, but D parameter values of stored fruits were greater than at day 0. This change could be attributed to the disruption of cuticular membrane, degradation of polysaccharides of the inner and outer cellular walls of the epidermis, contraction of epidermal cells, and rupture of membranes of mesocarp cells in stored tissues.Exposure of strawberries to 3.7 ppm ozone for 5 min could help in reducing fungal decay during refrigerated storage without affecting mechanical properties. The application of higher treatment times did not improve the microbiological quality.