Antioxidant and antimicrobial effects of stevia (Stevia rebaudiana Bert.) extracts during preservation of refrigerated salmon paste

Abstract

Stevia (Stevia rebaudiana Bert.) is a relevant source of natural phenolic compounds with antioxidant and antimicrobial properties. The aim of this study was to evaluate the potential protective effect of crude stevia extracts on the quality and shelf-life of salmon (Salmo salar) paste. For this, polyphenol extracts obtained by water extraction, ethanol/water extraction and supercritical CO2 with ethanol extraction were evaluated in preserving salmon paste. Salmon paste was stored under refrigerated conditions (5 degrees C) for 21 days, being primary, secondary, and total lipid oxidations monitored along storage by means of peroxide, p-anisidine, and TOTOX indices, respectively. In addition, 3/6 ratio, polyene index, and -tocopherol were monitored. Microbiological analysis comprised the investigation of aerobic mesophiles and psychrotrophes. Salmon paste samples treated with ethanol/water and supercritical CO2-ethanol stevia extracts exhibited the highest (p<0.05) 3/6 ratio and -tocopherol content. Besides, partial inhibition of both primary and secondary lipid oxidation events and aerobes and psychrotroph growth was also observed in both samples. These results correlated with the fact that ethanol/water and supercritical CO2-ethanol extracts provided the highest DPPH and FRAP values. These results open the way to the utilization of bioactive compounds from stevia leaves for the preservation of foods derived from salmon. Practical applications: The results obtained in this research show the possibility of using stevia and/or its derivatives of the sweetener industry as an alternative source of natural antioxidants in refrigerated fatty fish paste. The results indicate that it is possible to obtain advantages in the refrigerated salmon paste, based on the use of some extracts of stevia, which can help to inhibit lipid oxidation and development of pathogenic microorganisms. Further studies on the use of stevia and its derivatives should focus on the application of clean separation technologies such as supercritical fluid extraction. Stevia extracts obtained by extraction with water (W), ethanol-water mixture (E/W, 50:50 v/v) and extraction with supercritical CO2 and ethanol (SCE; scCO(2)/E, 95: 5 v/v) previously elimination of the steviosides demonstrates a conservative effect of refrigerated salmon paste. The SCE and E/W extracts provides better control of primary and secondary lipid oxidation compounds and moderate inhibition of aerobes and psychrotrophs.