Butter lipase activity

Mogensen, G., Jansen, K. 1986. Effect of pasteurization on lipase activity in milk, cream and butter. Dairy Sci. Abstr. 48, 244 (abstr no. 2073). 

Mortensen, B.K., Jansen, K. 1982. Lipase activity in cream and butter. Proc. 21st Int. Dairy Cong. (Montreal) 1(1), 334-335. 

An increasing problem is lipolysis in butter fat after manufacturing, which is caused by thermoresistant hpase enzymes that are created in the milk or cream by psycho-trophic bacteria or by residual native lipases that sirrvive pasteurization. Based on a determination of the lipase activity in cream, the keeping quality of manufactured butter in regard to hpolysis can be predicted with reasonable accirracy. A similar prediction for sweet cream butter can be based on lipase activity in the serum phase (71). The characteristic lipolytic flavors that can develop in milk products are primarily associated with the short- and medium-chain fatty acids that are relatively abundant in milkfat they have lower flavor threshold values than the long-chain fatty acids. As a result of improvements in the quality of raw milk and the standards of processing, lipolytic rancidity is seldom present in the fat source before its use in recombination (72). 

The C-mixed chain triglyceride test is designed as a test of intraluminal pancreatic lipase activity.The substrate for the test is 1,3-distearyl>2( carboxyl- C) octanoyl glycerol, which contains long chain fatty acids in positions 1 and 3 and the C-labeled medium chain fatty acid (octanoic acid) in position 2 (Figure 48-9). The labeled substrate is administered orally to fasting patients with a standard meal of toast and butter. Breath samples are collected over a 5-hour... 

Many lipases produced by psychrotrophic bacteria retain activity after pasteurization and ultra-high-temperature (UHT) heat treatments (Cousin 1982 Adams and Brawly 1981). Butter made from cream which supported growth of lipase-producing psychrotrophs became rancid within two days (Kishonti and Sjostrom 1970). UHT milk processed from raw milk contaminated with lipase from a Pseudomo-... 

A low level of NaCl (10 mM) may cause activation (Khan et al., 1967), although a high concentration inhibits the lipases. However, more than half of the activity remains in the presence of NaCl (2 M), a level similar to that in the aqueous phase of salted butter (Fitz-Gerald and Deeth, 1983). 

Lipase splits fatty acids from glycerol to produce free fatty acids, for example, butyric acid. If the original fat is butterfat then at low levels this produces a buttery or creamy flavour. As the free fatty acid content is increased, this strengthens the flavour to cheesy . Normally in toffees free butyric acid is not a problem at any practical level, possibly because of losses during cooking. Other free fatty acids have different flavours. Laurie acid, which is found in nuts, tastes of soap. This is not too surprising as soap often contains sodium laurate. Laurie fat sources, such as hardened palm kernel oil, are often used as a substitute for butter another potential source is nuts, which are sometimes combined with toffee. In any of these cases, lipolytic activity can shorten the shelf life of the product or render it totally unacceptable. 

Lipases in stored butter gradually release fatty acids from tri-acylglycerols, and their presence can be detected as a rancid and soapy flavour when they reach 30-40% of their threshold concentrations, which is a result of their synergism. The reaction is called hydrolytic rancidity. Responsibe for the rancid flavour is mainly butyric acid, followed by caproic acid. Caprylic acid has a rancid soap-like flavour, capric and lauric acids only have soapy flavours. Odour (and taste) threshold concentrations in butter made from sweet cream are 50 (60) mg/kg for butyric acid, 85 (105) mg/kg for caproic acid, 200 (120) mg/kg for caprylic acid, >400 (90) mg/kgfor caprinic (capric) acid and >400 (130) mg/kg for lauric acid, respectively. In long term stored butter, active oxidative rancidity products are (E)-non-2-enal, (Z)-non-2-enal in particular, while less active products are (Z)-hept-4-enal, oct-l-en-3-one and others. The rancid and soapy odour in butter can also be caused by contamination with anion active detergents, such as natriumdodecyl sulfate. 

Chen and Hong [65] showed that butterlike or cheeselike flavors could be obtained by the hydrolysis of butter fat by Candida cylidracea lipase solubilized in reverse micelles of soybean lecithin in a continuous butter oil phase. The enzyme exhibited less sensitivity to pH and temperature compared with an emulsified system and its activity increased with increasing surfactant or enzyme concentration. Due to a large interfacial area, a much higher enzyme concentration could be used before the system reached saturation. 

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