Antifungal Activity of Carboxymethyl Cellulose Edible Films Enriched with Propolis Extracts and Their Role in Improvement of the Storage Life of Kashkaval Cheese

Abstract

Propolis (bee glue) is a complex biological product known for its antimicrobial activity and antioxidant potential, and widely used as food additive and biopreservative. The aim of the present research was to examine the effects of propolis on the improvement of the storage life of ripened kashkaval cheese. For this purpose, three types of 1% carboxymethyl cellulose edible films containing three different ethanolic propolis extracts in concentration of 1% were prepared. Double-layer edible films were applied on the kashkaval cheese surface, and the samples were designated as T1, T2, and T3. An untreated sample was kept as a control. The four experimental groups (T1, T2, T3, and control) were then stored under refrigeration conditions at 4°C and 75% relative humidity (RH) for 56 days. During the storage period, the cheese was observed for visible changes, and samples for physicochemical and microbiological analyses were taken. The results from physicochemical analysis demonstrated that values of titratable acidity decreased in all experiment groups during the storage period. The results from microbiological analysis revealed that three types of edible films T1, T2, and T3 did not affect the decreasing number of lactic acid bacteria, a normal process for the period after the cheese ripening. The application of T1, T2, and T3 edible films did not affect the increasing number of yeasts in kashkaval cheese through the storage period. However, T1 and T2 edible films effectively inhibited the fungal growth on cheese surface, and no signs of spoilage were observed until the end of the storage for 56 days. In contrast, T3 treatment delayed but did not inhibit the fungal growth, and the first signs of fungal decay appeared between the 35th and 42nd day of the storage, compared to the control (28th day). Thus, the application of propolis can be considered an effective means for the prevention of fungal spoilage of kashkaval cheese.