Effects of ultraviolet-light emitting diodes (UV-LEDs) on microbial inactivation and quality attributes of mixed beverage made from blend of carrot, carob, ginger, grape and lemon juice

Abstract

Efficacy of ultraviolet light-emitting diodes (UV-LEDs) with peak and coupled emissions at 280, 365 and 280/365 nm on inactivation of E. coli K12 in mixed beverage (MB) was investigated. MB comprised of 31.6% carrot, 44.3% carob, 8.7% grape, 10.2% ginger, and 5.2% lemon juice. The impact of UV-LEDs on some physicochemical and phytochemical properties of MB was compared to that of heat treatment (70 °C, 120 s). While, UV-LED irradiation using coupled 280/365 nm for 40 min resulted in the highest inactivation of E. coli K12 (>4 log) out of tested wavelengths, the number of mesophilic bacteria (TAC), and yeast and molds (YM) in mixed beverage were reduced by 2.59 log CFU/mL (from 5.69 log CFU/mL of initial load), and 0.17 log CFU/mL (from 3.28 log CFU/mL of the initial load), respectively. Although, the color parameters slightly changed after irradiation, the color of MB did not show visual difference (?E = 0.94) compared to untreated samples. UV-LED treatment caused a significant increase in total phenolic compound (1.75-fold) and antioxidant capacity (4.60 fold) compared to heat-treated samples (p < 0.05). UV-LED treatment caused a decrease in carotenoid content (71.3%) lower than that of heat-treated samples (88.9%), indicating that UV-LED irradiation preserved the total carotenoid content better than the heat treatment. Industrial relevance: Light-emitting diodes (LEDs) are new sources of ultraviolet light utilized for non-thermal processing of foods. In this study, a static bench top unit was designed to investigate the efficacy of UV-LEDs with different treatment times and peak emissions by considering the inactivation of E. coli K12 in newly formulated mixed drink (MB). UV-LED irradiation of MB using coupled 280/365 nm for 40 min provided the highest microbial inactivation and preserved bioactive compounds better than the heat treatment. It can be proposed as an effective method for the processing of fruit juices which is rich in bioactive constituents. © 2020 Elsevier Ltd