Physicochemical, microbiological, and sensorial characteristics of cooked, marinated, and vacuum-packed oysters under frozen storage

This study evaluated the quality of frozen oyster meat. Seven hundred and twenty Crassostrea gigas oysters (~7-cm shell length) were steam-cooked at 100°C for 30 minutes and later divided into two groups. Group 1 was submerged for 20 minutes in water and ice; and group 2 in a solution containing water, ice, and 4% vinegar (4% acidity, produced by fermentation of acetic alcohol). After cooling, the oysters were shucked, and the meat was packed with a vacuum sealer in plastic bags containing 24 oysters each. The experiment evaluated physicochemical (pH, moisture, and total volatile bases nitrogen) and microbiological (total mesophilic and psychrotrophic bacterial counts) parameters every 45 days and performed sensory analyses after 180 and 365 days of storage. Adequate physicochemical and microbial characteristics were registered for up to one year of storage for both protocols. Marination with vinegar reduced the levels of psychrotrophic bacteria during storage, and the sensory analysis judges preferred the marinated oysters.