Growth Response of Eurotium chevalieri, Aspergillus fumigatus and Penicillium brevicompactum in Argentine Milk Jam

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 (aw range 0.74–0.85), pH (5.5 and 6.0) and the addition of 1,000 ppm potassium sorbate on Eurotium chevalieri, Aspergillus fumigatusand Penicillium brevicompactumgrowth response in milk jam stored at 25 °C or 35 °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, λ, 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.