Effects of different drying methods and storage conditions on the reduction of Escherichia coli and the quality parameters of barley sprouts

Abstract

Due to their high nutritional value and functional content, barley sprouts are commonly ground into powder for human use. This study investigated the effect of drying methods, viz., hot-air drying (HAD), freeze-drying (FD), and infrared drying (IRD), and storage conditions for the removal of Escherichia coli quality parameters of barley sprouts. Herein, the barley sprouts were subjected to HAD, FD, and IRD and stored at different temperatures, such as −20, 4, and 25°C, for six months. The changes in the colony count of E. coli and food quality indicators, viz., Hunter color, chlorophyll, and saponarin, were measured once a month. The HAD and FD were found to reduce E. coli from 7 log CFU/g to 4 log CFU/g, whereas IRD eliminated them (limit of detection ⟨ 1 log CFU/g). In the case of HAD, the E. coli counts and the quality of dried leaves did not change significantly (p>0.05) for six months under all storage conditions. Freeze-dried leaves stored at 25 and 4°C showed a decrease in E. coli counts from 4.5 to 1.2-1.5 log CFU/g after six months (p⟨0.05), and no significant change in quality during their storage was observed (p⟩0.05). In the case of infrared-dried samples, E. coli was not detected even after six months under all storage conditions, storing at −20°C was the best condition for the chlorophyll content and Hunter color (p⟨0.05). On the other hand, the content of saponarin was constant regardless of the drying method and storage.