Evaluation of Conventional Techniques and Ultrasonic Extraction of Some Plant by-products as Eco-friendly Antimicrobial Agents for Food Pathogens and Spoilage Microorganisms

Abstract

<title>Abstract</title> Plant byproduct extracts are obtained by extracting bioactive compounds from various plant byproduct sources, such as leaves, seeds and peels. These sources are rich in bioactive compounds such as total phenols (TPC), total flavonoids (TFC), and antioxidant capacity (TAC). These compounds have antioxidant and antimicrobial effects; hence, they are widely used as natural preservatives. The antimicrobial activity of organic extracts of some plant byproducts was determined via the disk diffusion method. The results revealed that the solvent (70%, 50% ethanol and water extraction) and extraction methods (conventional and ultrasonic extraction) significantly affected the amount of photochemical compounds (phenols, total flavonoids and total antioxidants) and antioxidant activity. Compared with the conventional method, ultrasonic extraction clearly affected antimicrobial activity, as it was more effective against <italic>Fusarium solani</italic>, <italic>Penicillium digitatum</italic>, <italic>E. coli</italic> and <italic>Erwinia cartov</italic> in most of the extracts. Pomegranate peels subjected to ultrasonic extraction resulted in the greatest inhibitory effect on the diameter of <italic>E. coli</italic> (31.5 mm) and <italic>Erwinia cartov</italic> (29.5 mm) in addition to fungi (<italic>Penicillium ssp.</italic>, 31.5 mm). However, the 50% ultrasonic ethanolic extract of Sidr leaves was highly effective <italic>against F. solani</italic>. Through this study, it became clear that the extraction method and the solvent used led to an increase in antimicrobial activity, and pomegranate peel extraction resulted in a higher inhibition rate than did the chemical preservatives used in the study. Therefore, plant extracts can be used as safe alternatives to chemical preservatives.