Source of Variation of Conjugated-Linoleic-Acid Contents in Dairy Products

Abstract

Samples of bovine milk (raw, thermized, or pasteurized) and of cheeses (raw and pasteurized) at 60 d of ripening were analyzed for contents in CLA. Detected values varied between 1.45 ± 0.20 mg/g in raw milk, 1.44 ± 0.05 mg/g lipid in thermized milk and 1.40 ± 0.11 mg/g in pasteurized milk, and 9.6 ± 0.5 mg/g in pasteurized cheeses and 10.8 ± 4.2 mg/g in raw-milk cheeses. Our results indicate that although processing factors such as heating and ripening affect the CLA contents of a dairy product, the major source of its variation among products may be the intrinsic amount of CLA present in the raw-milk.

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“…The average content of CLA found in milk samples from the Azores in Portugal varied from 1.45 ± 0.21 mg/g fat in raw milk, 1.44 ± 0.06 mg/g fat in thermized milk, and 1.40 ± 0.11 mg/g fat in milk samples when pasteurized. The CLA varied between 9.6 ± 0.5 mg/g, in pasteurized cheeses and 10.8 ± 4.2 mg/g in raw-milk cheeses (Kongo et al, 2014). These values agree with those reported by Pestana et al (2009) and Regula et al (2005) who reported that pasteurization, causes different changes in the free fatty acid profiles of ewes' milk, which in general has a higher content of CLA than cows' milk.…”

“…However, Shantha et al (1992) and Garcia-Lopez et al (1994) reported that the application of heat enhanced the formation of linoleic acid radicals and increased CLA content during the production of natural and processed cheeses, though this may partly be contributed by the concentration of the solids content including lipid fractions as % of serum (by dehydration through pressing and ripening under low relative humidity conditions). Although processing factors such as heating and ripening affect the CLA contents of a dairy product, the major source of its variation among products is the intrinsic amount of CLA present in the raw milk (Kongo et al, 2014), which varies with the livestock species (Pestana et al, 2009;Regula et al, 2005), as well as the nature of feed (Nuernberg et al, 2005). In a study in Argentina, Niuwenhove et al (2008) found that CLA averaged 0.85 and 0.96 in milk and 0.76 and 1.04 g/100 g of fatty acids in cheese of cow and goat, respectively, which seemed lower than values reported elsewhere (Ponnampalam et al, 2006).…”