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In addition to health effects, plant extracts can be used as natural preservatives with antioxidant and antimicrobial properties in the food industry. In this study, effect of antioxidant and antimicrobial properties of ethanolic extracts of watercress on the chemical and microbial quality of rainbow trout fillet at refrigerator temperature for 12 days was investigated. After drying the leaves at darkness and room temperature extract was extracted with 45, 65, 75 and 96% ethanol solvents for 24 hours at 65 °C. The results showed a significant difference (P≤0.05) in yields and phenolic content, 0.1 mg /ml of extract 65% with an extraction efficiency of 20% the highest amount of total phenol (88.60 ± 2.46%), DPPH (84.73 ± 0%); and ABTS (83.83 ± 0.06%) were. Also, the growth inhibition of the pathogenic bacteria Listeria monocytogenes, Escherichia coli, Staphylococcus aureus and Salmonella enteritidis in sample extracted with 65% ethanol had a significant difference with other extracts (P≤0.05). Rainbow trout fillet samples in 65% ethanol extract showed lower levels of TVB-N, PV and TBA to the control treatment during storage (P≤0.05). Rainbow trout fillet samples in 65% ethanol extract showed lower levels of TVB-N, PV and TBA indices of fillets compared to control treatment during storage (P≤0.05). Talking about bacterial index, the amount of total and pseudomonas bacteria in the treatment containing the extract did not reach the maximum allowable limit (10⁶ cfu /g^-1) by the twelfth day, Indicates the effectiveness of the extract on increasing the shelf-life of fillets compared to the control.
 

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Fungal spoilage plays an essential role in the deterioration of food and in the creation of foodborne disease. In addition, the production of various mycotoxins by fungi can cause serious dangers such as carcinogenic, teratogenic, immunotoxic, neuromastoxic, toxic dead, mycotoxicosis and Kashin Beck disease. On the other hand, despite the increasing resistance of molds to synthetic preservatives, that may produce carcinogenic nitrosamine, no effective strategy has been proposed to safely reduce of microbial growth for public health. Therefore, due to the safe and probiotic properties of the lactic acid bacteria that have been approved (GRAS and QPS), can be used as natural preservatives to prevent fungal spoilage of food. The ability to prevent and inhibitory fungal spoilage by lactic acid bacteria is mainly due to the production of antimicrobial compounds such as organic acids, fatty acids, hydrogen peroxide, phenyllactic acid, cyclic delpeptide, proteinaceous compounds, diacetyl, bacteriocin and reuterin. Also, the most important inhibitory mechanisms of lactic acid bacteria against fungal corruption include membrane  destabilization, proton  gradient interference,  enzyme  inhibition,  and  creation  of  reactive  oxygen  species. Therefore, in this paper, it has been tried to overview of antifungal metabolites and their chemical structure, inhibitory mechanisms and probiotic properties of the lactic acid bacteria.

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In recent years, the use of natural antimicrobial compounds in food has attracted the attention of consumers and researchers, the two main reasons for this is the excessive and incorrect use of antibiotics due to the selective pressure it exerts on microorganisms It creates resistance to antibiotics, thus increasing a group of microorganisms, including pathogens in food, which are not only resistant to antibiotics but also resistant to food processing and storage methods. Increasing public awareness of the potential negative effects of artificial preservatives on human health versus natural additives has led many researchers to focus more on the use of natural preservatives in food. Many compounds obtained from natural sources have antimicrobial properties and can be used to maintain food safety. Today, the use of food preservatives has become a necessity that plays an important role in the storage and transportation of food. The goals of adding preservatives to foods are to preserve the appearance of the food, to help preserve the organoleptic properties, and to increase the shelf life of the food. In this review article, we will examine the antimicrobial activity of some natural compounds obtained from different sources and their mechanism of action.