Investigating and optimizing the effect of combined coating of whey protein concentrate, maltodextrin and rosemary essence on the chemical properties of tilapia fish during cold storage

polyunsaturated fatty acids, and pH. One of the methods which can control the spoilage rate is the use of natural coatings. This study aimed to investigate the effect of coating Tilapia fish fillets with whey protein concentrate (10, 15, and 20% w/w), maltodextrin (15, 20, and 25% w/w), and rosemary essential oil (1, 3 and 5% v/w). The optimization of the process was conducted by response surface methodology and Design Expert software. For this purpose, 18 models were presented by the software, and the samples were immersed in the produced solutions and were kept at 4 °C for 6 days. After this period, peroxide value (PV), Thiobarbituric acid (TBARS), Total Volatile Basic Nitrogen (TVBN), and pH were measured. The results showed that by increasing the concentration of biopolymers and essential oil, all the investigated parameters were in lower limits, and in the sample coated with the maximum concentration of substances, the values of PV, TBARS acid, TVBN, and pH (in 100 grams), were 1.05 meq, 0.05 mg, 5.7 mg and 6.2, respectively, while these values for the coated sample with minimum concentrations, were 3.44 meq, 0.305 mg, 10.85 mg and 6.79 respectively. By optimizing the production process by software, the best solution was achieved by mixing 11.214% w/w of whey protein concentrate, 25% w/w of maltodextrin, and 3.402% v/w of rosemary essential oil.