Evaluation of antimicrobial effects of aqueous and alcoholic extracts of Spirulina platensis in UF white cheese

One of the most widely used cheeses in Iran is UF white cheese. The presence of nutrients in different types of cheese, make that susceptible to the growth of various microorganisms. Therefore, the use of preservatives to maintain the quality of this high-consumption dairy product is inevitable. In this study, the effect of concentrations of 0.3 and 0.5% aqueous and methanolic extracts of Spirulina platensis on growth inhibition of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli and also the effect of these extracts in preventing the growth of A.flavus in the UF white cheese has been investigated during 60 days of storage of the product in the refrigerator. In addition, the effect of extracts on texture, taste, color and overall acceptance of the product was evaluated. According to the results, a significant inhibitory effect (p≤0.05) of concentrations of 0.3 and 0.5 aqueous and methanolic extracts was observed on Listeria monocytogenes and Escherichia coli from the 15th day of the storage period and on Staphylococcus aureus from the 30th day of the storage period. The antibacterial effect of 0.5 concentration of methanolic extract was significantly higher than other treatments (p≤0.05). All treatments had a significant antifungal effect on Aspergillus flavus strains (p≤0.05). According to the results of the present research, the used extracts did not have a significant adverse effect on the sensory characteristics of the cheese samples, although the concentration of 0.5 methanolic extract insignificantly decreased the quality of the sensory characteristics of the cheese samples. In general, it can be said that concentrations of 0.5 aqueous extract and 0.3 concentration of methanolic extract of Spirulina platensis can be used as natural preservatives in UF white cheese.