Optimizing Salting and Immersion Time in Liquid Smoke of Farmed Gilthead Sea Bream (Sparus aurata) Fillets Using Response Surface Methodology

Abstract

Aims: To produce smoked gilthead sea bream fillets using the liquid smoke dipping method during brining and optimize the brining-smoking process using the response surface method. Study Design: The experimental design was a two-level Central Composite Design that included 14 runs divided into two blocks.  Place and Duration of Study: Department of Fisheries and Aquaculture Technology, Technological Educational Institute of Western Greece, Messolonghi, Greece, between April 2015 and December 2015. Methodology: Second order polynomial models for yield, moisture content, salt content, water activity, pH, redness index and instrumental texture parameters of salted and smoked with liquid smoke gilthead sea bream filets were developed as a function of salt brine content  (from 8.7 to 19.3% (w/w)) and immersion time (from 30 to139 minutes) in brining solutions that contained 10% w/w liquid smoke. A numerical optimization was used to find the optimum values for salt brine content and immersion time. For the confirmation of the models, smoked gilthead sea breams were prepared using the optimal settings of the factors. The yield, salt content, water content, water activity, redness index and the textural parameters were determined. The results were statistically compared to the values predicted by the mathematical models. A consumer panel evaluated the smoked gilthead sea breams prepared using the optimal settings of the factors. The proximate composition of the smoked gilthead sea bream was also determined. Conclusion: Within the range of brine salt content and immersion time used in the present work, the response surface model analysis and the model derived from the numerical optimization method proved useful in determining the optimum settings for salting and smoking with the liquid smoke of gilthead sea bream fillets. The optimal conditions for salt brine content and immersion time were 15.867% (w/w) and 109.975 minutes, respectively. Under optimal conditions, yield, water and salt content, water activity, pH, redness index, maximum shear force and work of smoked gilthead sea bream were 79.73%, 61.99%, 3.81% 0.94, 5.55, 0.41, 1269.1 (g*) and 3659.8 (g* sec), respectively. The water, protein, lipid and ash content of the smoked product were 61.87%, 20.89%, 12.43% and 3.56%, respectively, and the consumer panel highly accepted it.