Sensory and Microbiological Shelf-Life of a Commercial Ricotta Cheese

¹ Instituto Superior Experimental de Tecnología Alimentaria 6500 Nueve de Julio, Buenos Aires, Argentina

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°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°C, respectively. Q₁₀ (reaction rate at T + 10°C/reaction rate at T°C) for shelf life was 2.52 between 6 and 16°C and the corresponding activation energy was 14.8 kcal/mol.

Key Words: cheese • Ricotta • shelf-life prediction • sensory

Submitted on July 30, 1998
Accepted on November 16, 1998