Analysis of Fungal Diversity in Ready-to-Eat Pizza and Effectiveness of Pulsed Ultraviolet-Light Treatment for Inactivation of Mold on Agar Surface

Abstract

Fungal contamination is a significant issue in the food production industry; therefore, identification and characterization of food spoilage fungi would allow for early intervention to limit the amount of fungal contamination, particularly in cereal-based industries. In the present study, culture-dependent and culture-independent methods were applied to study the microbiota of ready-to-eat pizza. The study was pursued by evaluating the effectiveness of a broad-spectrum pulsed ultraviolet light for the decontamination of Penicillium roqueforti (a dominant spoilage mold in bakery products) on the surface of solid agar as a representative of a flat food surface. The average population of mesophilic aerobic bacteria (MAB), mesophilic anaerobic bacteria (MANB), lactic acid bacteria (LAB), molds and yeasts (M+Y) on naturally spoiled pre-cooked pizza were 6.7 ± 0.5, less than 2.3, 2.8 ± 0.6 and 5.4 ± 0.4 log10 CFU g -1 , respectively. Cloning and sequencing identified at least 5 genera and species of fungi (Penicillium spp., Saccharomyces spp., Rhodotorula mucilaginosa, Monascus fuliginosus, Galactomyces geotrichum) from 2 phyla (Ascomycota and Basidiomycota). Pulsed light process parameters evaluated were treatment time (1, 3, 5, 7 and 10 min) and voltage input (500, 750 and 1,000 V) at 5 cm distance from the pulsed UV-light. An increase of the input voltage of the lamps and of the duration of the treatment resulted in a higher inactivation of P. roqueforti. The population of P. roqueforti was reduced after 10 min of exposure to pulsed light by 3.74, 5.36 and 6.14 log10 CFU ml -1 at 500, 750 and 1,000 V, respectively. The inactivation kinetics was best described by the Weibull model (2 parameters) with the smallest root mean squared error (RMSE) and R 2 ≥ 0.92. The results of this work show that pulsed light is a promising technique for fungi elimination or decontamination in the bakery industry.