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ABSTRACT
The aim of this work is to evaluate the shelf life of Stracciatella cheese packaged in a protective atmosphere, using 4 different CO2:N2:02 gas mixtures [50:50:0 (M1), 95:5:0 (M2), 75:25:0 (M3), and 30:65:5 (M4) vol/vol] and stored at 8°C. Cheese in traditional tubs and under vacuum were used as the controls. Results showed that the modified-atmosphere packaging, in particular M1 and M2, delayed microbial growth of spoilage bacteria, without affecting the dairy microflora, and prolonged the sensorial acceptability limit.
Key words: Stracciatella cheese, modified-atmosphere packaging, shelf life
INTRODUCTION
Stracciatella cheese is produced from cow's milk in the Apulia region. It is a fresh cheese, white, and made up of fresh cream and frayed curd. It is stored and shipped like fresh Mozzarella and refrigerated in a tub. Considering that fresh cheeses have high moisture content and high fat content, these dairy products are very susceptible to microbial spoilage, especially under temperature abuse. Storage of fresh cheeses under aerobic conditions results in rapid spoilage.
The potential of modified-atmosphere packaging (MAP) for extending the shelf life of dairy products, including cheese, has been demonstrated (Floros et al., 2000; Papaioannou et al., 2007). These authors summarized that the success in cheese packaging is dependent on several important parameters such as the type of cheese, the use of starter cultures during production, its initial microbial contamination, and storage conditions. The gases normally used for MAP include CO2, O2, and N2. The most important gas from a microbiological point of view is CO2, used alone or in mixtures with N2 or O2, which inhibit the growth of many microorganisms, including spoilage bacteria (Daniels et al., 1985). Moir et al. (1993) demonstrated that a 40% CO2 atmosphere inhibited the growth of Pseudomonas spp. inoculated into the creamed-style cottage cheese at 5 and 15°C. Inhibition by CO2 was greater at 5°C and at the surface than in the interior of the cheese; the odor and the pH of the cheese were not affected by the gas. In a similar study, the effectiveness of flushing of headspace of commercial packages of cottage cheese with CO2 was investigated (Mannheim and Soffer, 1996). Flushing the packages with pure CO2 (25% vol/vol) increased the shelf life of cheese by increasing the lag phase...