UV-C light inactivation of single and composite microbial populations in tangerine-orange juice blend. Evaluation of some physicochemical parameters

Abstract

This study was aimed at investigating the response of single Saccharomyces cerevisiae KE162 or composited with three cocktails in a turbid orange-tangerine juice blend processed by UV-C 1720mJ/cm2, 20°C). Additionally, changes in polyphenol content (PC), total antioxidant activity (TAA), and some physicochemical parameters were analyzed after treatment. S. cerevisiae was combined with cocktails of yeasts (YC), Escherichia coli or native flora isolated from orange-tangerine peel. The adequacy of three conceptually different predictive models was also assessed. Overall, microbial inactivation curves displayed, in general, sigmoidal shape, with a significant shoulder. Moderate inactivation of single or composited inocula was achieved after UV-C treatment (3.9–4.3 log reductions). Coroller model allowed the best fit and the most accurate parameters’ estimation. S. cerevisiae in presence of background cocktails was less sensitive to UV-C, probably due to the interfering populations that hindered light path. UV-C treated juice displayed similar PC (0.61±0.06mg GAE/mL) and TAAABTS (0.82±0.14mg TroloxEq/mL) values than untreated juice (PC=0.63±0.10mg GAE/mL; TAAABTS=0.58±0.40, TAADPPH=3.69±0.14mg TroloxEq/mL), and a slight decrease in TAADPPH (2.77±0.06mg TroloxEq/mL), according to MANOVA. In addition, no changes in colour, acidity, turbidity, °Brix and pH (p>0.05) were recorded after UV-C exposure.