Probiotic in Lamb Rennet Paste Enhances Rennet Lipolytic Activity, and CLA and Linoleic Acid Content in Pecorino Cheese

Cheeses manufactured using traditional lamb rennet paste, lamb rennet paste containing Lactobacillus acidophilus, and lamb rennet paste containing a mix of Bifidobacterium lactis and Bifidobacterium longum were characterized for the lipolytic pattern during ripening. Lipase activity of lamb rennet paste, lamb rennet containing Lb. acidophilus, and lamb rennet containing a mix of bifidobacteria was measured in sheep milk cream substrate. Rennet paste containing probiotics showed a lipase activity 2-fold greater than that displayed by traditional rennet. Total free fatty acid (FFA) in sheep milk cream was lower in lamb rennet paste (981 μg/g of milk cream) than in lamb rennet containing Lb. acidophilus (1,382.4 μg/g of milk cream) and in lamb rennet containing a mix of bifidobacteria (1,227.5 μg/g of milk cream) according to lipase activity of lamb rennet paste. The major increase of FFA in all cheeses occurred during the first 30 d of ripening with the greatest values being observed for C16:0, C18:0 C18:1. At 60 d of ripening all cheeses showed a reduction in the amount of free fatty acids; in particular, total free fatty acids underwent a decrease of more than 30% from 30 to 60 d in cheeses manufactured using traditional lamb rennet paste, whereas the same parameter decreased 10% in cheeses manufactured using lamb rennet paste containing Lb. acidophilus and cheeses manufactured using lamb rennet paste containing a mix of B. lactis and B. longum. Cheese containing Lb. acidophilus was characterized by the greatest levels of total conjugated linoleic acids (CLA) 9-cis, 11-trans CLA and 9-trans, 11-trans CLA, whereas cheese containing bifidobacteria displayed the greatest levels of free linoleic acid. Rennet pastes containing viable cells of Lb. acidophilus and a mix of B. lactis and B. longum were able to influence the amount of FFA and CLA in Pecorino cheese during ripening. Key words: conjugated linoleic acid , rennet paste , probiotic , Pecorino cheese IntrODuCtIOn Lipolysis is an important biochemical event occurring during cheese ripening that leads to the formation of FFA, which are precursors of compounds that are volatile and contribute to flavor (Collins et al., 2003). However, excessive lipolysis could result in the presence of off-flavors, because high concentrations of volatile FFA influence cheese flavor either directly or as precursors for other compounds (Pinho et al., 2003). Lipases in cheese originate from different sources such as milk, rennet paste, starter, adjunct starter, nonstarter bacteria, and the addition of exogenous lipases (Deeth and Fitz-Gerald, 1995; Fox and Wallace, 1997; McSweeney and Sousa, 2000). Rennet paste is used for ovine and caprine cheese production in Mediterranean countries and its lipolytic activity is responsible for the extensive lipolysis occurring during ripening. Rennet paste contains lipases with different specific characteristics and activities identified as pregastric esterase, highly specific for realizing free fatty acids from the sn-1 and sn-3 positions of tryacylglycerols, and gastric lipase (Richardson et al., 1971; Nelson et al., 1977). Sheep milk is commonly used for cheese production due to its high fat and total solids content. However, the high fat content in sheep milk might limit the demand for milk products by health-conscious consumers (Zhang et al., 2006). Several studies have shown the possibility of manipulating milk fat acid composition through animal diet to increase the concentration of polyunsaturated fatty acids, health-promoting conjugated linoleic acids (CLA), and linoleic acid (Cabiddu et al., 2006; Van Nieuwenhove et al., 2007). An alternative strategy to improve the nutritional value of dairy