Extending the Shelf Life of Camembert Cheese via Controlling Over-Ripening by Bacteriocin of Newly Lactic Acid Bacterial Isolate LAB100

摘要

Camembert cheese is a surface white mould ripened cheese; when full ripe the casein becomes liquefy as the intensive degradation occurs by proteinases from surface flora and results over-ripening and off flavor. To control this, partial purified bacteriocin like substances (PPBLS) from newly lactic acid bacterial isolate (LAB100) exhibited antifungal activity against Penicillium candidum (in vitro) were used. Inhibition (%) of P. candidum by PPBLS at concentrations of 2, 4, 8, 16 and 32 mg/ml was 34, 50, 79, 80 and 85%, respectively. Based on their superior antifungal potential activity; isolate LAB100 was phenotypically and genotypically characterized as newly Lactobacillus sp. For delaying the Camembert cheese over-ripening (in vivo), bacteriocin producing isolate LAB100 and its PPBLS were incorporated and applied in different camembert cheese treatments. Three treatments beside control were conducted; after brining all cheese treatments stored at 12±2℃ to ripen for 12 days and then at 5±2℃ for more 30 days to complete ripening. Organoleptic properties, pH values and nitrogen distribution were determined during ripening period. In addition, the proteolysis of treated Camembert cheese was monitored by gel electrophoresis. The cheese treatment (T2) made with bacteriocin producer isolate LAB 100 added as co-culture to main starter recorded the highest total score, followed by T3 and the lowest one was recorded for control (T1). The highest WSN/TN% was in T1; 5.4, 22.87, 34.41 and 57.65% at 3, 10, 20, and 40 days after brining, respectively, while the lowest WSN/TN% was recorded for treatment that made with both bacteriocin producer strain LAB100 and sprayed by PPBLS solution after 3 days of brining (T3), where it was 5.05, 9.85, 13.82, and 31.74% at the same previous ages, respectively. These results were confirmed by gel electrophoresis, indicating that bacteriocin producer LAB100 and or its bacteriocin controlled the protein degradation. These results suggest that both bacteriocin producer strain and its PPBLS minimize the growth of P. candidum as a consequence the rate of proteolysis was controlled and hence extending the shelf life of Camembert cheese is occurred.