Microbial and sensory changes during refrigerated storage of desalted cod (Gadus morhua) preserved by combined methods

Water blanching and the use of additives (potassium sorbate and citric acid) combined with different types of packaging (air, vacuum VP and modified atmosphere packaging MAP: 60% CO2, 30% N-2 and 10% O-2), were studied as new methods of preservation of chilled desalted cod. Microbial counts and total volatile basic nitrogen (TVB-N) analyses were carried out during a period of 42 days on all samples stored at 4 degrees C. No Aeromonas or sulphite-reducing Clostridium were isolated from any of the analysed samples. The lowest microbial counts of mesophilic, psychrotrophic, Pseudomonas, moulds and yeasts, were found in samples with additives in all kinds of packaging. These samples in VP or MAP maintained an excellent microbial quality throughout the 42 days of storage, with mesophilic and psychrotrophic counts always below 4 log CFU/ g. Counts of the four microorganisms above-mentioned in blanched samples packaged with air, exceeded 5 log CFU/g on days 21-28, so it became necessary to use VP or MAP to maintain these microorganisms at an acceptable level for the entire storage period. TVB-N contents were low in samples with additives, regardless of the kind of packaging, as well as in blanched samples packaged in VP and MAP, never reaching 25 mg/100 g. Since there were no significant differences either in microbial growth or in TVB-N between samples in VP and MAP, a sensory analysis was performed only in desalted cod submitted to the two treatments (blanching and additives) combined with VP, both in raw and cooked samples. The results of this analysis showed that the addition of potassium sorbate and citric acid did not alter the typical organoleptic features of desalted cod. The sensory characteristics of both blanched samples and those with additives in VP showed no change during the period of the study. (c) 2007 Elsevier B.V. All rights reserved.