Some factors involved in milk lipase activation by agitation

Abstract

SummarySeveral factors which influence the shape of activation curves relating the degree of agitation-induced lipolysis in raw milk to the temperature of agitation were investigated. Curves of the type previously reported (Fitz-Gerald, 1974) containing a maximum at 12–15 °C resulted from low speed agitation with incorporation of air, with fresh (< 12-h old) milk, with milk of fat content ≥ 3·0 % approx. and by low temperature incubation of activated milks. Activation curves containing no distinct maximum at 12–15 °C were obtained from high speed agitation and homogenization, with milks of low fat contents and with aged (≥ 24-h old) milk. Agitation at low temperatures resulted in a maximum degree of activation in fresh milk after 2–4 h cold storage.During agitation of raw milk redistribution of lipase activity between the cream and skim-milk phases occurred. The extent of redistribution depended on the time and temperature of agitation. Cream prepared from milk agitated at low temperatures contained lipase activity several times greater than cream from unactivated milk. The practical significance of this effect is discussed.

Cheese: Methods of Chemical Analysis

“…Aliquots of the free fat are weighed, dissolved in solvent and the free fatty acids titrated with alcoholic KOH (-0·02 M) using methanolic phenolphthalein as indicator. 175 The Bureau of Dairy Industry (BDI) method, developed by Thomas et al,l76 was applied to Cheddar cheese by Dulley & Grieve. 177 Cheese samples were dispersed in 2% sodium citrate prior to de-emulsification arid titration.…”

Lipolytic Enzymes and Hydrolytic Rancidity in Milk and Milk Products

“…This can be explained in terms of the agitation causing either aggregation or dispersion of the milk fat globules, with the predominant effect being determined by the temperature of the milk and the severity of agitation. 247 Besides its effect on the integrity of the milk fat globule, agitation causes a redistribution of lipase between the skim-milk and cream phases. 53 ,231.248.249 Agitation of milk at 5-lO o C or 3rC results in a severalfold increase in lipase activity associated with the cream.…”

“…53 ,231.248.249 Agitation of milk at 5-lO o C or 3rC results in a severalfold increase in lipase activity associated with the cream. 231 The amount of lipase transferred to the cream is not reflected in the extent of lipolysis in whole milk, but it is in the lipolysis in cream separated from activated milk. Since the transferred enzyme is bound to the milk fat globule membrane and in this form has enhanced heat stability.…”

Determination of free fatty acids in milk and cheese procedures for extraction, clean up, and capillary gas chromatographic analysis

“…Various procedures have been proposed for isolating the FFA from the lipid extract after extraction. These methods include column chromatography with supports such as silicic acid-KOH 16, 81, strong anion exchange resins [3, [9][10][11], and alumina 112,131 …”