NON THERMAL PRESERVATION OF FRESH- CUT FRUIT SLICES BY USING UV-C LIGHT

GÓMEZ, PAULA; SCHENK, MARCELA; GUERRERO, SANDRA; SALVATORI, DANIELA; ALZAMORA, STELLA MARIS

Viña del Mar

Congreso; International Congress on Engineering and Food; 2008

Instituto Chileno de Ingeniería para los Alimentos (IChIA). G; International Asocciation of Engineering and Food (IAEF)

The use of UV-C light (radiation in the range of 200 to 400 nm, with maximum lethal effect at 254 nm) has been proposed as an emergent non-thermal preservation technology for disinfection of fruits and vegetables. The objective of this work was to investigate the effect of UV-C doses on the inactivation of Listeria innocua on the surface of apple and pear slices and to study the fruit color changes    along storage at 4-5ºC. For inactivation studies, pears and apples were washed, peeled and sliced into 3 cm in diameter and 3 mm thick disks under aseptic conditions,  inoculated with Listeria innocua (~106 CFU/ml) and placed at 10 cm distance from two UV-C lamps (15 W, 254 nm) inside a wooden box covered with aluminium foil. At selected storage times, four disks of each duplicate experiment were analyzed for survival at each treatment dose by pour plating in tripticase soy agar. Survival curves were modeled using a Weibullian distribution of resistances model. Color measurements were made on fruits cut into 3 cm in diameter and 6 mm thick slices. A pretreatment with an antibrowning solution containing 1% (w/v) ascorbic acid + 0.1 (w/v) calcium chloride for 5 min at 4ºC applied prior to irradiation was also investigated. Tristimulus color measurements were made on ten treated samples for each condition throughout a week of storage in closed plastic trays. UV-C intensity was measured by the iodide-iodate chemical actinometer and UV-C radiation doses were between 0 and 145 kJ/m2. The greatest log reduction rates were observed at doses £ 15 kJ/m2. UV-C was more effective at reducing microbial counts on pear (3.4 log) than on apple (1.8 log) surface. Inactivation kinetics was successfully fitted using the Weibullian model. Narrow frequency shapes, strongly skewed to the right, without mode and with high variances were obtained. Superficial browning increased in irradiated samples throughout storage, especially at greater doses.  Antibrowning solution pretreatment helped in decreasing browning after UV-C exposure. This study gives useful quantitative information on the effectiveness of UV-C light against L. innocua and changes in quality (color) of minimally processed fruits.