Microbiological and nutritional quality impact of gamma irradiation at low doses on spinach leaves (Spinacia oleracea L.)

FINTEN GABRIEL; COVA CONSTANZA; NARVAIZ PATRICIA; AGÜERO MARÍA VICTORIA; JAGUS ROSA JUANA

Concordia, Argentina

Conferencia; FoodInnova, International Conference on Food Innovation; 2014

UNER

The consumption of minimally processed vegetables (MPV) has dramatically increased during last decades, as well as foodborne outbreaks associated with the consumption of these products. It has been demonstrated that disinfection step during elaboration of MPV achieves reductions in microbial load between 1 and 2 log cycles; therefore this procedure does not guarantee that fresh produce is free of pathogens. In this context, the irradiation treatment after packaging has been proposed by many researchers as an effective method to market a safe product. The objective of this study was to evaluate the impact of γ-irradiation treatments on microbiological and nutritional quality of spinach leaves. Spinach leaves were harvested, washed, packaged and subjected to irradiation doses of 1.5 and 3.0 kGy. Microbiological quality was followed through aerobic mesophilic bacteria (AMB, PCA, 37°C-24h), psychrotrophic bacteria (PB, PCA, 5°C-5d) and yeasts & moulds (Y&M, YGC, 28°C-48h). Nutritional quality of spinach leaves was evaluated through antioxidant capacity (DPPH methodology), total polyphenols content (Folin-Ciocalteau), chlorophyll and carotenoids contents (AOAC methodology). All samples (including control) were analysed before and after treatments, and during storage (15 d; 5±1°C). Log reductions in microbial counts immediately after treatments were 3.22, 4.86 and 2.41 for AMB, PB and Y&M, respectively, at the lowest dose, and for the highest dose were 4.59, 4.86 and 3.06 for AMB, PB and Y&M, respectively. At the end of the storage the microbiological quality of treated samples was better than control samples, especially those subjected to the highest dose, besides, the impact of irradiation was more noticeable in AMB than in PB and Y&M counts. Regarding nutritional parameters they didn´t suffered significant changes after γ-irradiation treatments and during the 15 days of storage, however, they vary slightly over the storage period without a clear trend and that could be attributed to the intrinsic variability of the spinach leaves. Hence γ-irradiation treatments at low doses are a good way of keeping good microbiological quality of packaged spinach leaves throughout refrigerated storage, thus improving product safety. In addition these treatments didn´t show a detrimental effect on the nutritional parameters studied.