Effect of aqueous ozone post-drying conditioning on microbiological quality and optical properties of raisins

POK, PAULA; GÓMEZ, PAULA; RESNIK, SILVIA; ALZAMORA, STELLA

chicago

Congreso; IFT 2022 Annual Meeting; 2022

Institute of Food Technologists

Sun drying in the open air is the most widely applied drying method in the commercial production of raisins. The quality of the product thus obtained is affected by environmental contamination, microbiological deterioration, and discoloration. A post-drying conditioning stage is usually performed to improve the quality of the final product. In this work, the effect of ozone washing as a post-drying sanitizing treatment of raisins was studied. Its impact on raisin color was also analyzed.Dried grapes cv. Sultanina were exposed to aqueous ozone (100 g per 1.25 L H2O; 4.5 mg O3/L,20±1°C; 10 to 15 min) by means of an ozone generator module connected to a bubble column. Inorder to compare with the conventional decontamination treatment, raisins were also treated with0.01 % (w/v) sodium hypochlorite solution for 2 min. Untreated raisins were used as control. Theexperiments were replicated twice. The enumeration of molds and yeasts, and the aerobic platecount were performed according to the Bacteriological Analytical Manual (FDA). The color ofsamples was recorded using a Konica Minolta photocolorimeter, analyzing 20 raisins per treatment.Data obtained were analyzed by one-way ANOVA and MANOVA.Microbial load after sun drying was significantly reduced with the application of aqueous ozonetreatments. Non-significant differences between the ozone doses applied were observed. Thereductions achieved were about 0.6-0.7 log cycles for total aerobic and 0.76-0.78 log cycles formolds and yeasts. When compared to the hypochlorite treatment, a significantly higher reduction in mold and yeasts were observed in ozonized samples. Regarding the color of raisins, none of thetreatments induced significant changes in the colorimetric parameters (L*, a* and b*) as comparedto the control samples. These findings suggest that ozone washing could be a suitable alternative treatment for thepost-drying conditioning of raisins, improving microbiological quality and maintaining theircharacteristic color.