Efeitos da adição de óleo essencial de Origanum vulgare L. e de Rosmarinus officinalis L. combinados em queijo fresco durante armazenamento

Abstract

Lactic acid bacteria (LAB) are widely used as starter cultures in the preparation of fresh cheeses. These products have been described as good matrices for incorporation of probiotic bacteria, because they have pH close to neutral and high moisture content. These same characteristics can favor the contamination of fresh cheeses by pathogens able to survive under refrigeration, such as Escherichia coli O157:H7. The essential oil (EO) from Origanum vulgare L. (Oregano - OVEO) and Rosmarinus officinalis L. (rosemary - ROEO) may act in synergism against food related bacteria, however, information on its effects on starter cultures and probiotics, or against pathogens during the storage are scarce. The present study evaluated the effects of OVEO and ROEO in synergistic combination on the viable cell counts of the pathogen Escherichia coli O157:H7, the probiotic strain Lactobacillus acidophilus LA-5 and Lactococcus spp., and in fresh cheese over 21 days refrigerated storage (7 ± 0.5 °C). The prevalent OVEO and ROEO terpenes and the physicochemical and sensory aspects that characterize the cheese incorporated of these EOs in synergistic concentrations were also determined during storage. The incorporation of OVEO (0.03 or 0.07 μL/g) and ROEO (1.32 or 2.65 μL/g) in combination in cheeses (produced with the starter or probiotic culture) did not reduce the counts of Lactococcus spp. or L. acidophilus LA-5, while caused a reduction of approximately 3.0 log CFU/g in E. coli O157:H7 counts during the earlier 15 days storage. After this storage time, only a bacteriostatic effect was observed against the pathogen in the cheese. The incorporation of OVEO and ROEO in synergistic combination delayed the increase in counts of both starter and probiotic cultures in cheeses during storage but did not affect the ability of the probiotic strain to survive under simulated gastrointestinal conditions throughout the storage time. A total of 15 OVEO and/or ROEO terpenes were detected in cheeses immediately after production or after 24 h of storage and the amount of all terpenes detected decreased over the 21 days of storage. Eucalyptol, camphor and α-pinene were the terpenes detected in highest amounts in cheeses during the storage time studied. The incorporation of OVEO and ROEO in synergistic concentrations in the cheeses did not affect the yield, or the physical-chemical characteristics of the product. The cheese incorporated of OVEO and ROEO in combination produced with the starter culture was characterized by camphor and mint flavor and greater softness. The sensory scores attributed to aroma, taste, overall impression and purchase intention of probiotic cheese (produced with L. acidophilus LA-5) with OVEO and ROEO increased over the storage. The results show that the incorporation of OVEO and ROEO in synergistic concentrations does not compromise the viability of starter or probiotic culture but is effective to control of E. coli O157:H7 in cheese during refrigerated storage.