Milk fat hydrolysis

Lipase from Aspergillus sp. Milk fat hydrolysis (rich in saturated fatty acids) Oil-phosphate buffer (1/2) 35.7 101... 

Bachman, K.C., Hayen, M. J., Morse, D., Wilcox, C. J. 1988. Effect of pregnancy, milk yield, and somatic cell count on bovine milk fat hydrolysis. J. Dairy Sci. 71, 925-931. 

Holland, R., liu, S.Q., Crow, V.L., et al. (2005) Esterases of lactic acid bacteria and cheese flavour Milk fat hydrolysis, alcoholysis and esterification. 7nf Dairy 715, 711-718. 

Continuous stirred-tank reactor Hydrolysis of milk fat Lipase from Rhizopus delemar 127... 

Lipolysed milk fat was one of the first flavours produced with the help of enzymes. The original process was based on the controlled lipase-catalysed hydrolysis of cream [18]. For instance, Mucor miehei lipase possesses a high selectivity towards flavour-active short-chain fatty acids. Additionally, lipases that prefer long-chain fatty acids or lipases without particular preferences can be found. The free fatty acids produced can be isolated by steam distillation and further purified. Thus, it is possible to obtain pure short-chain fatty acids like butanoic, hexanoic, octanoic and decanoic acid. 

Downey (1980) reasoned that although milk lipoprotein lipase is present in sufficient amounts to cause extensive hydrolysis and potential marked flavor impairment, this does not happen in practice for the following reasons (1) the fat globule membrane separates the milk fat from the enzyme, whose activity is further diminished by (2) its occlusion by casein micelles (Downey and Murphy 1975) and by (3) the possible presence in milk of inhibitors of lipolysis (Deeth and Fitz-Gerald 1975). The presence in milk of activators and their relative concentration may also determine whether milk will be spontaneously rancid or not (Jellema 1975 Driessen and Stadhouders 1974A Murphy et al. 1979 Anderson 1979). 

The use of homogenized milk for cheesemaking has been reviewed by Peters (1964). The advantages of homogenized milk in the manufacture and ripening of cheese are (1) lower fat losses in whey and therefore a higher yield, (2) reduced fat leakage of cheese at room temperatures, and (3) increased rate of fat hydrolysis and, therefore, desired flavor production in blue cheese. 

Breakdown of milk fat probably occurs in all cheeses, but the rate and extent of hydrolysis varies considerably between cheese varieties... 

Stadhouders, J. and Veringa, H. A. 1973. Fat hydrolysis by lactic acid bacteria in cheese. Neth. Milk Dairy J. 27, 77-91. 

Two types of enzymes in milk are important those useful as an index ol heat treatment and those responsible tor bad flavors. Phosphatase is destroyed by the heat treatments used to pasteurize milk hence its inactivation is an indication of adequate pasteurization. Lipase catalyzes the hydrolysis of milk fat which produces rancid flavors. It must be inactivated by pasteurization or more severe heat treatment to safeguard the product against off-flavor development Other enzymes reported to have been found in milk include catalase, peroxidase, protease, diastase, amylase, oleinase. reductase, aldehydrase. and lactase. 

In some milk fat globules, small aqueous compartments are located beneath the membrane bilayer, which have been termed cytoplasmic crescents (Huston and Patton, 1990). Whether or not this cytoplasmic inclusion provides some benefit is unknown. Yet, as this aqueous compartment is protected from the bulk serum phase by the MFGM, constituents located therein are presumably afforded some protection, at least initially, from gastric hydrolysis. Huston and Patton (1990) found crescents in all samples of milk they examined, and they were more prevalent in human (7.3% of globules), than in bovine (1% of globules) milk. Furthermore, there was considerable individual and diurnal variation. The structure of a cytoplasmic inclusion, surrounded by an intact plasma membrane on one side and a fat globule surface on the other, may allow certain labile constituents to be protected until they reach their proper site of bioactivity. At this point it is not known whether the crescents have a purpose or are simply the result of inefficiencies in the secretion process. As it is possible to isolate milk preparations enriched in cytoplasmic crescents, there is an opportunity to determine the nature of the materials found within. This unusual biocompartment may prove to be a model of food structure for biodelivery. 

A number of studies have examined the use of lipases from a variety of sources for hydrolysis of milk fat. Lipase from Aspergillus niger could be... 

Alternatively, the enzyme may be used in an encapsulated form. Chen and Chang (1993) showed that hydrolysis of milk fat by lipase from Candida cyclindracea encapsulated in reverse micelles formed by soybean lecithin in isooctane, could be manipulated to favor the release of short-chain fatty acids by using a higher concentration of enzyme and a higher ratio of water to surfactant concentration at 45°C. 

Chen, J.-P., Chang, K.-O. 1993. Lipase-catalyzed hydrolysis of milk fat in lecithin reverse micelles. J. Ferment. Bioeng. 76, 98-104. 

Phospholipids also have a role in the LPL-catalyzed hydrolysis of triglycerides. The activator apo-LPs exhibit enhanced activation in the presence of phospholipids such as phosphatidyl choline (La Rosa et al., 1970 Blaton et al., 1974) and in milk there is evidence that apo-LPs in the absence of phospholipids are unable to initiate lipolysis of intact milk fat globules by the indigenous LPL (Driessen and Stadhouders, 1974 Clegg, 1980). The phospholipids are believed to be involved in the reaction through their interaction with the substrate rather than with the enzyme (Blaton et al., 1974). 

The natural substrates for lipases are triglycerides but, because of the complexity of these and the fact that they seldom contain a chromophore or other label to enable ready detection of the products, several synthetic substrates have been developed. These enable different detection techniques such as spectrophotometry, fluorimetry, chromatography, or radiometry to be used. It is important to note that, by definition, true lipases are active only on water-insoluble esters while esterases cleave only water-soluble esters (Jaeger et al., 1994). Thus, it is important that methods used for milk and milk products use substrates, which detect true lipase but not esterases as lipases play a major role in the hydrolysis of milk fat, while the role of esterases is considered insignificant (McKay et al., 1995). 

Blackberg, L, Hernell, O., Olivecrona, T. 1981a. Hydrolysis of human milk fat globules by pancreatic lipase. J. Clin. Invest. 67, 1748-1752. 

Sundheim, G., Bengtsson-Olivecrona, G. 1987b. Hydrolysis of bovine milk fat globules by lipoprotein lipase inhibition by proteins extracted from milk fat globule membrane. J. Dairy Sci. 70, 1815-1821. 

Evidence suggests that dietary sphingolipids, acting through their hydrolysis products, ceramide and sphingosine, can inhibit the development of colon cancer (Duan, 1998 Vesper et al., 1999). In milk fat, sphingomyelin is by far the predominant sphingolipid. 

Patel, M.T., Nagarajan, R., Kilara, A. 1996. Hydrolysis of milk fat by lipase in solvent-free phospholipid reverse micellar media. J. Food Sci. 61, 33-38. 

Lipases are produced by microorganisms such as bacteria and molds are produced by plants are present in animals, especially in the pancreas and are present in milk. Lipases may cause spoilage of food because the free fatty acids formed cause rancidity. In other cases, the action of lipases is desirable and is produced intentionally. The boundary between flavor and off-flavor is often a very narrow range. For instance, hydrolysis of milk fat in milk leads to very unpleasant off-flavors at very low free fatty acid concentration. The hydrolysis of milk fat in cheese contributes to the desirable flavor. These differences are probably related to the background upon which these fatty acids are superimposed and to the specificity for particular groups of fatty acids of each enzyme. 

Dairy Hydrolysis of milk fat Cheese ripening Modification butter fat Elavour compounds Cheese, cheese flavour Butter, butter flavour... 

---