Resumo

Mold spoilage is an issue of great concern in the food industry since it represents significant economic losses. Ascospores of heat resistant molds belonging to the genera Neosartorya, Byssochlamys, Talaromyces and Eupenicillium can survive commercial treatments normally applied to the food, as apple juice. The extremely resistance of B. fulva and N. fischeri ascospores serve as standards for sterilization quality of acid products. Studies relate the difficulty of quantifying the growth of filamentous mold associated with foods. The most common used method to assess mold growth in solid substrates is radial growth of the colonies. However, this method is difficult to be applied to real food substrates. Alternatively, ergosterol content has been used to quantify mold contamination in food products. Ergosterol is the dominant sterol in most molds and is not found to any significant extent in plants, animals or bacteria. Thus, its quantification in food samples can be taken as an index of the presence of mold. Accordingly, the aim of this study was modelling the growth of heat resistant molds by ergosterol quantification compared to radial colonies growth rate (mm/h) measurements. Apple juice with soluble solids adjusted to 12 °Brix and added for 1.5 % of agar was used as growth media. Media were pasteurized at 115 °C for 1 min and added in plates. A loop of the analyzed microorganism (10⁵ spores/mL) was inoculated into the center of each plate and incubated at 30 °C. The radial growth of the colonies was measured at each 24 hours, and the quantification of ergosterol was realized by HPLC when the colonies growth reached 30, 60, 90, 120 and 150 mm. A linear relation between the radial growth and ergosterol content of B. fulva and N. fischeri in solidified apple juice was observed showing that the ergosterol quantification can be accepted as a reliable method for quantifying mold growth in foods. The high sensitivity of the ergosterol determination makes it extremely useful for the quality measurement of mold in food.