Impact of Pulsed Light on Mold Growth Isolated from Cheese: Mycelial Growth and Spore Inhibition

Pulsed light (PL) is emerging as a non-thermal technology with excellent prospects for the control of various kinds of microorganisms. Its application for mould inactivation in cheese would allow a reduction of mold spoilage losses as well as the prevention of mycotoxin contamination at a storage condition. The aim of the study was to investigate the antifungal activity of PL on Alternaria spp and Penicillium spp isolated from caciocavallo samples, evaluating the effect on mycelia growth and spore germination. Alternaria and Penicillium strains were grown on Cheese agar medium (CAM) and Potato dextrose agar (PDA) medium, incubated at 15°C.The mycelia of 2 days and spores from mature culture were treated by Xenon X-100 PL system emitting 3 pulses/sec, placed at 6 cm from the lamp and subjected to 30,60,120 pulses. No treated samples were considered as control. The samples were incubated at 15°C for 10 days in case of mycelia and for spores 24 hours. The inhibition (%) of mycelial growth and spore germination was measured. Significantly inhibitory effects on mycelial growth of tested strains were observed after PL treatments. The highest inhibition of about 25% was reached with T120 treatment on CAM, or both Alternaria and Penicillium. Interesting results were obtained for spore germination. In fact, all PL treatments significantly inhibited the germination of Alternaria spores with percentage of inhibition ranging from 82 to 87% on CAM and on PDA medium. While in the case of Penicillium spores PL treatment significantly inhibited spore germination from 89 to 95%. The results obtained in this study confirmed that PL is a technology able to control molds. However, further studies are needed to understand the effectiveness of cheese and the applicability on dairy industry for improving the safety and the quality of the products.