Pulsed light treatment of cut apple: dose effect on color, structure and microbiological stability.

GÓMEZ, P.; SALVATORI, D.; GARCÍA LOREDO, A. ; ALZAMORA, S.M.

FOOD AND BIOPROCESS TECHNOLOGY

SPRINGER

Lugar: Nueva York; Año: 2012 vol. 5 p. 2311 - 2322

1935-5130

This study investigated the effect of pulsed light (PL) dose on color, microstructure, and microbiological stability of cut apples during 7-day refrigerated storage. Apples were irradiated at two different distances  from the lamp (5 or 10 cm) during 2 to 100 s (2.4 to 221.1 J/cm2). Cut-apple surface exposed to high PL fluencies turned darker (lower L* values) and less green (higher a* value) than the control, and this effect was more pronounced as PL dose and/or storage time increased. On the contrary, the application of few flashes (2.4 J/cm2) allowed maintaining the original color of apples slices along storage. Light microscopy images of treated samples showed degraded walls and broken plasmalemma and tonoplast, which may explain, at least partially , the increase in browning of irradiated apples at high doses. Inactivation patterns of inoculated microorganisms depended on PL dose and the type of microorganism. After 100 s PL treatment at 5 cm, no counts were observed for Saccharomyces cerevisiae KE162, while for Escherichia coli ATCC 11229 and Listeria innocua ATCC 33090, reduction levels were 2.25 and 1.7 logs, respectively . Native microflora population was in general higher in control samples than in 10 and 60 s PL irradiated apples along the whole storage. Although the application of high PL fluencies allowed obtaining greater microbial reductions, they also promoted browning of apple. Application of PL at a dose of 11.9 J/cm2 could extend the shelf life of cut apple with minimal modification in color.