Abstract

Milk jam (dulce de leche) is a typical Argentine sweet spread prepared from milk concentrated by evaporation to about 70% w/w total solids at atmospheric pressure with added sucrose, glucose and vanillin. Growth of xerotolerant moulds represents a severe problem in this type of product with high sugar concentration. This work aimed at analysing the influence of water activity (a(w) range 0.74-0.85), pH (5.5 and 6.0) and the addition of 1,000 ppm potassium sorbate on Eurotium chevalieri, Aspergillus fumigatus and Penicillium brevicompactum growth response in milk jam stored at 25 degrees C or 35 degrees C during 90 days. Growth curves were successfully modelled by applying the modified version of Gompertz equation. There were proposed polynomials equations relating time to detection, lambda, with two independent variables: potassium sorbate and water activity at pH 6.0. Some useful combinations of these factors were found to assure inhibition of mould growth during a critical storage period. Results might contribute to optimise manufacture conditions and/or milk jam composition to obtain a safer product when failure occurs during the hot filling process or when the product is stored for a long period of time.