Investigating the Effect of Preservatives and Antioxidant on the Oxidative and Microbial Properties of Walnut Butter during the Shelf-life

Walnuts contain many nutritional compounds, including omega-3, various vitamins, especially vitamin E and types of minerals. Therefore, the development of foods based on walnut and studies on chemical and microbial stability during storage, is very important. In this research, the effects of various concentrations of BHT (three levels 100, 150 and 200 mg/L) on changes in peroxide value and acid value of walnut butter, as well as the effect of two types of preservatives of benzoic acid and sorbic acid, each in two levels (400 and 800 mg/kg) were separately and mixed, on the total count of microorganisms and the count of mold and yeast of walnut samples during 75 days of storage at ambient temperature is investigated. The results of this study showed that by adding BHT at 200 mg/L, the peroxide value decreased significantly compared to the control sample. After production, acidic value was 0.3% and it rose to 0.4-0.5% after 75 days of storage. Also, benzoic acid was more effective in reducing total bacterial count and counting mold as well as yeast during storage in comparison with sulfuric acid.