Antimicrobial Activity Of Cranberry Extract Against Staphylococcus Aureus And The Effect Of Cranberry Extract On The Quality Of Cooked Meat

Botanical natural products have attracted much attention due to their broad-spectrum antibacterial activity,natural health and safety.Cranberry is a botanical natural product rich in antibacterial components such as anthocyanins and proanthocyanidins.In recent years,scholars have conducted a lot of researches on the antibacterial ability of cranberry berry juice,diluted cranberry juice,cranberry juice concentrate,cranberry juice powder and cranberry extracts to foodborne pathogenic bacteria.However,the mode of action of effective antibacterial ingredients in cranberry against food-borne pathogens is not completely clear.The application research in food on the antibacterial effect of cranberry is rare.Therefore,in this study,Staphylococcus aureus ATCC 13565 was selected as the tested strain to study the antibacterial ability,mode of action and application in the food of cranberry extract(the main component is anthocyanin).In this study,the antibacterial ability of cranberry extract against Staphylococcus aureus is determined by the minimum inhibitory concentration(MIC)of cranberry extract against Staphylococcus aureus and the effect of different concentrations of cranberry extract on the growth of Staphylococcus aureus;the mode of action of cranberry extract is revealed by studying the intracellular ATP content,cell membrane potential,changes of bacterial protein and cell morphology of S.aureus treated with cranberry extract;the antiseptic effect of cranberry extract was studied by measuring the effects of different concentrations of cranberry extract on the p H and chromaticity of cooked meat products during storage and the control effect on S.aureus in the samples.The study indicates:The MIC of cranberry extract against Staphylococcus aureus was 5.0 mg/m L;and as the concentration of cranberry extract increased,the antibacterial effect was significantly enhanced.Treatment with 2 MIC of cranberry extract for 0.5 h inhibits 108 CFU/m L of Staphylococcus aureus completely.In the study of mode of action,by measuring the ATP content of S.aureus cells treated with cranberry extract,it was found that the intracellular ATP content of the cells was significantly decreased(P < 0.05)which indicated the cells were damaged;by measuring the membrane potential and intracellular p H changes of S.aureus after the treatment of cranberry extract,it was found that the depolarization of the cell membrane and lower intracellular p H appeared in the cells,which proved that the cell membrane was damaged.The changes of bacterial cell protein content wereanalyzed by SDS-PAGE.The results showed that as the treatment time increased,the bacterial protein bands gradually became lighter and disappeared,which proved that the cranberry extract could destroy the bacterial proteins.The effect of cranberry extract on the morphology of S.aureus cells was observed by transmission electron microscopy.The results showed that the S.aureus treated with 1 MIC of cranberry extract showed irregular wrinkles and rough surface,deformation and collapse,damage of cell membrane and cell wall,leakage of part of the cell contents.S.aureus treated with 2 MIC cranberry extract showed more severe morphological damage,including separation of the plasma membrane from the cell wall,large leakage of cell contents,and observation of collapsed or broken cells.In the application study,different concentrations of cranberry extract were added to cooked meat samples and stored at 4oC for 9 days.The antibacterial activity of cranberry extract on Staphylococcus aureus in cooked meat products showed that the number of Staphylococcus aureus was effectively reduced compared with the control group.With the increase of the concentration of cranberry extract,the inhibition effect is more ideal,and the inhibition effect can last for a while.By measuring the p H and color changes of samples after adding the cranberry extract,it was found that the cranberry extract changed the p H and color of samples compared to the control group,but the cranberry extract could maintain a stable p H and color of the samples during storage.In a word,the cranberry extract can effectively inhibit Staphylococcus aureus,and the antibacterial effect is gradually enhanced with the increase of the concentration of cranberry extract.The antibacterial action of cranberry extract against Staphylococcus aureus was related to lower intracellular ATP and higher membrane potential,leakage of proteins,pore-formation with damaging cell membranes and promoting the release of cell constituents of Staphylococcus aureus.Cranberry extract can effectively inhibit Staphylococcus aureus in cooked meat products,and maintain the p H and color of the samples stably.The results showed that the cranberry extract,which is a botanical natural product,has the potential to be used as a natural preservative to reduce the risk of Staphylococcus aureus.