Interaction of factors which influence the extent of lipolysis during milking and storage of raw milk

Abstract

SUMMARYThe effect of aeration and agitation during milking on free fatty acid (FFA) levels in raw milk was investigated by comparing (a) a dual vacuum system with a ‘round the barn’ installation and (b) a claw piece requiring high air bleed with conventional claw pieces. Reduced milk transfer pressure resulted in a reduction in lipolysis of 54%, while high air bleed led to a 21% increase. FFA values were related to milk yield, stage of lactation and to a lesser extent the incidence of mastitis. These relationships were largely independent of the type of milking equipment. Fat content and somatic cell count did not affect the level of lipolysis. Increases in FFA due to activation by added blood serum were strongly related to the initial FFA concentrations.

Lipase redistribution in cows' milk during induced lipolysis: I. Activation by agitation, temperature change, blood serum and heparin

“…However, as observed by Needs et al (1986), lipolytic response tailed off in milks with high spontaneous lipolysis. On the other hand, induced lipolysis resulting from vigorous activations was relatively independent of spontaneous lipolysis.…”

“…Deeth & Fitz-Gerald, 1975;Anderson & Needs, 1983;Ahrne & Bjorck, 1985;Cartier & Chilliard, 1986;Needs et al 1986;Jellema, 1986;Sundheim & Bengtsson-Olivecrona, 1987 a).…”

“…Ahrne 1 & Bjorck (1985) and Needs et al (1986) proposed that FFA level could play a more important role. Indeed, studies carried out with artificial lipid emulsion as substrate showed that FFA and monoacyl-glycerols released during lipolysis could inhibit LPL by coating the lipid substrate (Bengtsson & Olivecrona, 1980).…”

“…Milk from some cows may be completely resistant to activation by temperature changes (Deeth & Fitz-Gerald, 1976) or by blood serum (Anderson & Needs, 1983). However, correlations between spontaneous and induced lipolysis have been reported (Cardwell & Asher, 1980;Anderson & Needs, 1983;Jellema, 1986;Needs et al 1986;Chazal & Chilliard, 1987).…”

Introduction of automatic milking system in Finland effect on milk quality

“…Escobar and Bradley (1990) suggest that lipolysis is mainly caused by milk pipelines, but it can also be caused by bacteria, such as psychrotrophic bacteria (Shah 1994). The effect of mechanical treatment on milk causing lipolysis continues during storage (Needs et al 1986). However, rapid cooling of milk has been reported to delay the lipolysis (Escobar and Bradley 1990).…”