The effect of adding walnut green husk extract on antioxidant and antimicrobial properties of ketchup

In this study, walnut green husk extract, which is a valuable waste of horticultural products, was used to enhance antioxidant properties and reduce microbial load of ketchup sauce. Extraction efficiency of walnut green husk extract 22.01%, total phenolic compounds 65.40 (mg gallic acid per 100 g dry husk), flavonoids 10.06 (catechin mg per 100 g dry husk), and EC50 0.17 (mg/mL) were expressed. The MBC value of this extract for Saccharomyces cerevisiae (0.045 mg/mL) is lower than the value of this factor in Lactobacillus fructivorans (0.123 mg/mL). Next, ketchup sauce samples containing control sample, containing 0.086 (mg/mL) walnut green husk extract and 0.123 (mg/mL) walnut green husk extract were prepared. The results showed that application of higher concentrations of extract (0.123 mg/mL) in the first month increased the total phenolic compounds (73.72 mg gallic acid per 100 g dry matter) and  flavonoids (14.11 mg catechin per 100 g dry matter) and reduced EC50 (0.34 mg/mL) in ketchup sauce. The results of the total counts, mold, yeast and Lactobacillus bacteria of ketchup sauce samples containing walnut green husk extract were significantly different from allowing control sample.