Acta Scientiarum Polonorum Technologia Alimentaria

Background. Cooling and freezing were used as one of the most important and widely used methods of fixation of the food. However, it must be stressed that low temperatures should not be applied to stock up bakery goods, but to improve production organisation, balance demand and supply, as well as to provide consumers with a wide range of fresh fish.

Material and methods. Raw Atlantic herring was packed in polyethylene (PE) bags: in air or in vacuum and then frozen and stored at –25°C. The quality of fresh fish and of carcasses and fillets after 1, 2, 3 and 4 months of storage was estimated by determination of weight change, pH, moisture and fat content, hardness, cohesiveness, springiness, resilience, gumminess, and chewiness.

Results. Weight of the air-packed herring samples decreased along with frozen storage time, due to changes in moisture content in the muscle tissue. The vacuum-packed raw material did not demonstrate weight changes. Moisture content was correlated with cohesiveness of the fish packed in air. Strong correlations were found between hardness and gumminess / chewiness regardless of the packing method, springness and pH / fat content of vacuum-packed fillets, and cohesiveness and springness / resilience of the vacuum-packed carcasses. Additionally, significant correlation coefficients were obtained between coherence and resilience for carcasses packed in air, as well as between gumminess and chewiness regardless of the packing method. Significant correlation occurred also between cohesiveness and resilience for carcasses packed in air, as well as between gumminess and chewiness regardless of the packing method. The packing method, as well as raw fish processing were found to have a major impact on cohesiveness and springiness, and in the case of carcasses also on resilience. No significant differences in hardness, gumminess and chewiness were found for samples obtained from different sections of the same fish, either fillets or carcasses. Significant differences were found in textural properties between the fresh and stored samples. Only hardness, gumminess and chewiness of fish samples did not show any significant changes throughout the storage period.