Effect of storage temperature and osmotic pre-treatment with alternative solutes on the shelf-life of gilthead seabream (Sparus aurata) fillets

Abstract

The objective of the study was the kinetic modelling of the shelf-life of osmotically pre-treated fish during refrigerated and super-chilled storage. Fresh gilthead seabream (Sparus aurata) fillets were treated for 0–360 min at 15 °C in osmotic solutions 50:5 high dextrose equivalent maltodextrin:NaCl/100 g (HDM), 40:10:5 HDM:trehalose:NaCl/100 g (HDM + treh) and 40:10:5 HDM:glucosamine:NaCl/100 g (HDM + gluc). Water loss, solid gain, salt content and water activity were monitored throughout treatment. Slices untreated and osmotically pre-treated for 45 min were aerobically packed and stored isothermally at 15, 10, 5, 2.5, 0, −1 and −3 °C. Quality assessment was based on microbial growth (total viable count, Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae spp., H2S-producing bacteria, lactic acid bacteria, yeasts and moulds), total volatile nitrogen (TVB-N), lipid oxidation (TBARs) and sensory scoring. Quality indices were kinetically modelled and temperature dependence of quality loss rates was modelled by Ratkowsky equation.Osmotic pre-treatment led to significant shelf-life extension of fillets, in terms of microbial growth, chemical changes and organoleptic deterioration. The pre-treatment with the alternative solutes led to depression of the freezing point (−1.8, −2.6, −3.2 and −3.5 °C for the untreated samples and the osmotically pre-treated with HDM, HDM + treh and HDM + gluc, respectively). TVB-N values were higher in untreated samples, followed by osmotically treated fillets, mainly at higher storage temperatures (i.e. 10 and 15 °C). Based on the mathematical models for sensory evaluation scoring, the shelf-life was 12, 19, 22 and 22 days at 0 °C for untreated and osmotically pre-treated with HDM, HDM + treh and HDM + gluc fish slices, respectively, while the respective values at −3 °C were 21, 35, 38 and 38 days. The alternative solutes had no significant effect on the quality and shelf-life of pre-treated fish fillet during storage at refrigerated conditions.