Investigating the effect of Thyme essential oil and chitosan as a natural preservative on the quality and antioxidant properties of French salad sauce

Today, sodium benzoate and potassium sorbate are mainly used to control microbial contamination, mold and yeast, which have carcinogenic effects. The aim of this study was to evaluate the effect of chitosan (0.06 %w/w) and thyme extract (0.08 %w/w) separately and simultaneously (chitosan 0.03+thyme extract 0.04 %w/w) on physicochemical, microbial and sensory properties of French salad dressing and comparison with control samples (French sauce containing sodium benzoate + potassium sorbate and without preservative). The results showed that the addition of chitosan and thyme extract in comparison with the control sample had no significant effect on changes in pH, water activity and emulsion suspension during storage (p <0.05). Addition of chitosan and thyme extract showed a significant increase and decrease of L * index and a * index in comparison with the control sample and had no significant effect on the amount of b * index. The results of microbial tests showed that treatment with chitosan 0.03% + 0.04% thyme in both MIC and MBC concentrations had a good inhibitory effect on the growth of hetero fermentative lactic acid bacteria, Escherichia coli and mold and yeast at the end of the storage period, no growth was observed. The sample containing chitosan 0.03% + 0.04% thyme received the highest sensory evaluation score. The results of this study showed that the use of natural preservatives of chitosan and thyme extract can significantly reduce the consumption of chemical additives and this is a step in improving the health of the consumer community.