Determination of changes in microbiological properties and quality parameters during and after shelf life of some dairy products

The main problems encountered by food products throughout their shelf life include microbial spoilage, chemical changes, and sensory quality losses. This situation increases risks to public health and negatively affects the market value of these products by directly impacting consumer perception through the deterioration of sensory characteristics. This study aimed to investigate the changes in microbiological properties and various quality parameters of low-fat fresh lor (cottage) cheese, grated mozzarella cheese, and full-fat homogenized yogurt products sold in their original packaging under appropriate shelf-life conditions before and after the expiration of their shelf life. The products were stored in a cold cabinet at 2-4°C for twice their designated shelf life, based on the best-before date. Samples were taken from the cheeses at 30-day intervals and from the yogurt at weekly intervals, depending on the total storage duration. Initially, these products were suitable in terms of microbiological load and quality analysis. For cheese, coagulase-positive Staphylococcus bacteria counts, and moisture content were determined throughout the shelf life, while for yogurt, E. coli and acid content were determined. Additionally, these products were evaluated in terms of sensory characteristics such as appearance, odor, taste, and texture. Considering the expiration date indicated on the packaging, it was determined that low-fat fresh cottage cheese and full-fat homogenized yogurt maintained their quality throughout their shelf life, but deterioration was observed in grated mozzarella cheese. This deterioration was found to be due to a loss of sensory quality. In conclusion, it was determined that low-fat fresh cottage cheese and full-fat homogenized yogurt maintained their quality throughout their shelf life, while grated mozzarella cheese deteriorated before the end of its shelf life.