Preservative effect of combined treatment with electrolyzed NaCl solutions and essential oil compounds on carp fillets during convectional air-drying

The antimicrobial and antioxidant effects on carp fillet samples of treatments with alkaline electrolyzed NaCl solution EW (−) prior to treatment with acidic electrolyzed NaCl solution EW (+) and 1% solutions of the essential oils consisting of 0.5% carvacrol and 0.5% thymol (1% Cv + Ty) were tested. First carp fillet samples were treated with EW (−), then EW (+), followed by 1% (C + T), represented as [EW (−)/EW (+) / 1% (Cv + Ty)] for 15 min, during drying at 45 °C. Samples were subsequently evaluated by microbiological, chemical and sensory analyses. Microbiological analyses indicated that the initial total microbial counts of samples treated with EW (−)/EW (+), 1% (Cv + Ty) or EW (−)/EW (+) / 1% (Cv + Ty) were significantly (p ≤ 0.05) reduced, compared with the control sample. Treatment with EW (−)/EW (+) / 1% (Cv + Ty) gave the strongest overall inhibition of microbial growth when compared to all of the other treatments. The volatile basic nitrogen (VBN) value of samples treated with EW (−)/EW (+) / 1% (Cv + Ty) was kept at low level (18.46 ± 0.45) until the end of drying period (5 days), compared with control samples (40.33 ± 0.58). Treatment with EW (−)/EW (+) / 1% (Cv + Ty) during drying significantly reduced the peroxide values (PV) and thiobarbituric acid values (TBA). Sensory evaluation indicated that there were significant differences (p ≤ 0.05) in the color, odor, taste, flavor and texture, on the end of the 5-day drying period between samples treated with EW (−)/EW (+) / 1% (Cv + Ty), as compared to all of the other treatments. We conclude that treatment with EW (−)/EW (+) / 1% (Cv + Ty) had stronger antimicrobial and antioxidant effects than all of the other treatments on carp fillets during drying, and could be a good alternative to artificial preservatives in food industry.