Effect of freeze-chilling, in comparison with fresh, chilling and freezing, on some quality parameters of raw whiting, mackerel and salmon portions

Freeze-chilling involves freezing and frozen storage followed by thawing and chilled storage. It offers logistic benefits for fish packers as it enables packaged fillets to be held frozen and then released into the chill chain as required. Trials with whiting, mackerel and salmon fillets/portions indicated no difference in odour scores (raw samples) between freeze-chilled and chilled samples; however, freeze-chilled salmon portions were inferior in terms of odour to chilled. Fresh fillets received the highest acceptability scores (cooked samples) followed by frozen, chilled and freeze-chilled samples. The pattern in the data was the same for each species and there was no statistically significant difference between the freeze-chilled and chilled samples. The total volatile base nitrogen (TVBN), trimethylamine (TMA) and total viable count (TVC) data were the same for the three species in that the chilled and freeze-chilled samples had the highest values and the fresh and frozen the lowest. However, there was no statistically significant difference between the freeze-chilled and chilled samples. Freeze-chilled samples had the highest free fatty acid (FFA) and peroxide values (PV) but the levels were low and did not influence sensory response. Gravity drip was significant in the frozen and freeze-chilled samples but presented no major visual problems and could readily be absorbed by drip pads. The effects of the four treatments on the colour and texture of the raw samples were small in practical terms. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.