Lipolysis and the distribution of lipase activity in bovine milk in relation to stage of lactation and time of milking

Abstract

The increase in levels of free fatty acids (FFA) in morning and afternoon milk after 48 h cold storage at 5 °C was determined at two stages of lactation in milk from 96 cows. Lipolysis was positively correlated to day of lactation (r = 0-6, P < 0-001), while the correlations between lipolysis and milk yield and fat content respectively were due to these factors being related to day of lactation. In afternoon milk the level of FFA increased almost three times above that in morning milk. Lipolysis was closely related to the Hpoprotein lipase (LPL) activity associated with the cream fraction (r = 0-8, P < 0-001). Afternoon milk had higher LPL activity in the cream fraction than morning milk. Lipase activity in the cream increased with increasing stage of lactation. Cooling of milk increased LPL activity associated with the fat phase. This effect was greater in afternoon milk from late lactation than in morning milk from early lactation. When heparin was added to milk the LPL activity associated with the fat increased substantially; again, this effect was greater in afternoon milk from late lactation than in morning milk from early lactation. Lipolysis was higher in heparinized milk than in normal milk, and there was a close correlation between lipolysis and LPL activity associated with the fat (r = 0-82, P < 0-001). Characteristics of the milk fat globule influencing the attraction of LPL were found to be fundamentally important to lipolysis.

The influence of a seasonal milk supply on the biochemical and sensory properties of Cheddar cheese

“…Auldist et al (1996) reported that Cheddar cheese made using LL milk had a lower flavour score with 'lipolytic' or 'oxidized' flavour notes, and attributed this to a high concentration of FFAs in LL milk or from increased lipolytic activity by lipoprotein lipase (LPL). The activity of LPL associated with the cream fraction was reported to increase with SOL (Ahrne´& Bjo¨rck, 1985), but its contribution to lipolysis in Cheddar cheese is unclear (Fox & Stepaniak, 1993). LPL is extensively inactivated by high-temperature short-time (HTST) treatment (72 C Â 15 s) (Deeth & Fitz-Gerald, 1983), but Driessen (1989) reported that heat treatment of 78 C Â 10 s is required for its complete inactivation.…”

Best use for milk – A review.II– Effect of physiological, husbandry and seasonal factors on the physicochemical properties of bovine milk

“…Suhren et al . (), Ahrne and Bjorck () reported that free fatty acid levels were higher when shorter milking intervals were used. O'Brien et al .…”

Lactation Responses toward Milk Indigenous Enzymes

“…Higher activity is associated with its presence in fat fraction of milk. Activity of lipase in milk fat increases with the advancement in lactation stages [21]. The lipolysis process is of major apprehension in the dairy industry, as rancid off flavors are produced in milk and milk products during this phenomenon [22].…”