Survey of antibacterial activity of alcoholic extracts of Aloe vera, German chamomile and Mentha piperita L as natural preservative of pasteurized milk

Recently, studies have been conducted to use plant compounds as natural preservatives in foods. So, the objective of this study was first to evaluate antimicrobial activity of ethanolic and methanolic extracts of Aloe vera, German chamomile and Mentha piperita L cultivated in Medicinal plants farm of agricultural research institute of zabol university, against spoilage and pathogenic microorganisms associated with pasteurized milk including Pseudomonas aeruginosa, Bacillus cereus, Micrococcus luteus, listeria monocytogenes and Escherichia coli and the next stage was to investigate the impact of ethanolic extracts of aloe vera and German chamomile on the shelf life of pasteurized milk. The results indicated that Aloe vera had the most antimicrobial activity followed by German chamomile and Mentha piperita L respectively (P<0.05). In general, the ethanolic extract of studied plants was found to posses more powerful antibacterial activity than methanolic one (P<0.05). Ethanolic extracts of Aloe vera and German chamomile were evaluated as natural preservatives at concentrations of 0.15, 0.3 and 0.6 (% v/v). The results revealed that the treatments of pasteurized milk with 0.3% and 0.15% of German chamomile and also Aloe vera with a concentration of 0.3% with acceptable sensory properties had a significantly lower total microbial count and longer shelf life compared to the control sample. Therefore, this study confirmed the possibility of usingof the extract of mentioned plants as a preservative in pasteurized milk besides its beneficial properties of a functional food.