Development of a Combined Temperature and pH Model and the Use of Bioprotectants to Control of Mucor circinelloides

Abstract

Fungi are the major cause of fresh fermented dairy spoilage adversely affecting the economic performance of the dairy industry. The control of the contamination and the inhibition of the fungal growth is a constant challenge during the production process. The development of natural and effective procedures that guarantee food quality is nowadays an imperative. However, the successful application of the hurdle technology demands a better understanding of the behaviour of microorganisms in relation to the most relevant preservation factors. In this study the effect of temperature, pH and bioprotectants on the growth of Mucor circinelloides was investigated. The mold was isolated from deteriorated yogurt and identified by molecular techniques. Mucor circinelloides was inoculated in potato dextrose agar at two different pH levels (4.5 and 5.8) and five different temperatures (4, 12, 21, 29 and 37°C). The growth was evaluated by a factorial design at different combinations of pH and temperature. The results demonstrated that temperature and pH and the interaction between them were the factors that controlled the growth rate of the microorganism. At pH 4.5 and 21°C, the mycelium growth rate presented the highest growth rate and no evident apparent lag phase. Biological control with the addition of lactic acid bacteria and their metabolites as bioprotectants resulted in a reduction of up to 50% in the mycelial growth rate of M. circinelloides. The present study provides useful information of the kinetic growth parameters of M. circinelloides under different pH and temperatures values and presence of bioprotective agents. The results of the study showed the biocontrol potential of lactic acid bacteria and their metabolites on the growth of molds.