The Effect of Active Packaging Film Based on Chitosan Containing Rosemary (Rosmarinus officinalis L.) Extract on Cheese Shelf Life

White cheese is an inseparable part of the Persian breakfast table. However, it has limited shelf life owing to microbial growth and chemical changes. Application of active packaging incorporated with essential oils is an innovative technique to retain quality and extend shelf life of foods. In this study, the effect of chitosan (Ch 1 and 2%) film containing rosemary extract (RE 0.5 and 1%) was studied on the shelf life of white cheese at 4°C for 45 days. The physicochemical evaluation showed that all treated cheeses had higher pH, moisture, and fat content, but acidity and hardness in treated cheeses were lower than the nontreated ones. During storage, pH, moisture, and fat content decreased and acidity and hardness increased. At the end of the storage, the highest acidity (1.79 g lactic acid) and hardness (3.5 N) and the lowest pH (4.1) were observed in the control sample, and the highest moisture (53.92%) and fat (21.84%) content was observed in E₂C₂ treatment (1% extract + 2% chitosan). The active packaging of cheese caused a significant decrease in the total count of bacteria, coliforms, lactic acid bacteria, mold, and yeast. The population of microorganisms in the control sample increased significantly during storage (p < 0.05). The treated cheeses had acceptable sensory properties. The most effective treatment for maintaining the physicochemical properties and retarding the growth of microorganisms in cheese was the E₂C₂ sample. Therefore, it can be used in active packaging systems of cheese.