Sensory and microbiological shelf-life of a commercial Ricotta cheese

Ricotta is a soft cheese that has a high moisture content and an initial pH above 6.0 and, thus, has a limited shelf-life even under refrigeration. The objectives of the present work were to calculate sensory and microbiological shelf-life using Weibull's distribution and to obtain kinetic parameters to predict shelf-life for different storage temperatures. Ricotta cheese was stored at 6, 17, and 25 degrees C; during storage, samples were removed for sensory, microbiological, acidity and pH analyses. Appearance, texture, flavor, total aerobic mesophiles, and acidity followed a similar pattern over storage time. As expected, pH decreased over storage time, although the changes were irregular. Shelf-life values at +/-95% confidence limits, calculated from Weibull's distribution, were 33 +/- 1.4, 12.5 +/- 0.5, and 5.5 +/- 0.5 d for temperatures of 6, 17, and 25 degrees C, respectively. Q(10) (reaction rate at T + 10 degrees C/reaction rate at T degrees C) for shelf life was 2.52 between 6 and 16 degrees C and the corresponding activation energy was 14.8 kcal/mol.