Water Activity Influence on Walnuts (Juglans Regia L.) Microbiological and Oxidative Stability

Walnut is the gold reserve of Republic of Moldova, being highly valued for their quality (size and protein content). In 2017, Republic of Moldova managed to become one of the top producers and exporters of walnuts in the world. Lipid oxidation and microbiological growth has been correlated to water activity, therefore the objective of this study was to identify the influence of water activity on walnut (Juglans Regia L.) oxidative and microbiological stability. Walnuts were stored under different water activities and maintained for 16 weeks. Through this period, changes of moisture, peroxide value and microorganisms' development were monitored. The highest oxidation rates were observed in walnuts stored under water activities ranges 0.0 - 0.28 and 0.48 - 1.00. Moisture content showed an increasing trend for all the water activity conditions. Analyzing the obtained results, we concluded that to reduce the number of bacteria and molds, as well as peroxide value and moisture content from walnut kernel, with a view to preserve their quality, it is necessary that the water activity of storage rooms to fit in limits from 0.28 to 0.48.