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Научни трудове на Съюза на учените в България-Пловдив. Серия В. Техника и технологии, естествен ии хуманитарни науки, том XVI., Съюз на учените сесия "Международна конференция на младите учени" 13-15 юни 2013. Scientific research of the Union of Scientists in Bulgaria-Plovdiv, series C. Natural Sciences and Humanities, Vol. XVI, ISSN 1311-9192, Union of Scientists, International Conference of Young Scientists, 13 - 15 June 2013, Plovdiv.
BIOACTIVE FATTY ACIDS IN MILK AND THEIR HEALTH BENEFITS Maja Dimanovska*., Mila Arapceska
"University St. Kliment Ohridski", Faculty of Biothecnical Sciences -
Bitola, R. Macedonia e-mail: [email protected]
Abstract
In recent years there is increased interest about foods which contain components that have bioactivity. Milk and dairy products have long traditions in human nutrition.
Milk composition is rather than complex. Its constituents have been for many years on the priority list of research, with their positive and negative effects on human health. Milk alone is much more than the sum of its nutrients. It is composed of various substances with bioactive properties and therefore milk was given an epithet of functional food.
The most variable component of milk is milk fat. It is one of the components which determine milk nutritive quality and technological performance of milk. Milk fat contains a number of components which are metabolically active such as: sphingolipids, conjugated linoleic acid (CLA), butyric acid, other fatty acids, vitamins A and D. A variety of health benefits have been associated with these compounds.
Key words: milk fat, conjugated linoleic acid (CLA), health benefits
Introduction
The changes in the alimentary patterns in the last years are the reasons for many human diseases. In recent years there is increased interest about foods which contain components that have bioactivity. Milk and dairy products have long traditions in human nutrition.
Milk composition is rather than complex. Its constituents have been for many years on the priority list of research, with their positive and negative effects on human health. Milk alone is much more than the sum of its nutrients. It is composed of various substances with bioactive properties and therefore milk was given an epithet of functional food.
Composition of milk fat
The most variable component of milk is milk fat. It is one of the components which determine milk nutritive quality and technological performance of milk. Milk fat has influence on smell and aroma of milk, and on consistence and texture of dairy products. Despite of other milk components milk fat has highest energetic value (9 kcal/g or 37 kJ/g).
Bovine milk contains about 3.5 to 5% total lipid, existing as emulsified globules 2 to 4 ^m in diameter and coated with a membrane derived from the secreting cell (Jensen et al., 1991).
About 98% or more of the lipid is triacylglycerol, which is found in the globule. Phospholipids are about 5 to 1% of total lipids, and sterols are 2 to 5%. These are mostly located in the globule membrane. Cholesterol is the major sterol at 10 to 20 mg/dL (Jensen et al., 1991).
It is composed of triacylglycerides, diacylglycerides, monoacylglycerides, free fatty acids, cholesterol, phospholipids and cerebrosides.
The major functional properties of milk fat are based on its triglyceride (TG) composition. Milk fat is uniquely complex in its TG composition because of the large number of fatty acids, which range from C4 to C28, and because of all of the isomers that have been identified. Milk fat contains fatty acids of complex structures, including monobranched, multibranched, dienes, trienes, hydroxy, cyclic, and others (Jeminez-Flores, 1997).
According saturation of fatty acids, bovine milk fat contains 70-75% saturated fatty acids, 20-25% monounsaturated fatty acids, and 2-5 % polyunsaturated fatty acids. Percentage of fatty acids with short chain is higher in milk from ruminates than in milk from unruminates. Profile of fatty acids present in milk fat determines uniqueness of its composition as well as its physiological characteristics (Chilliard et al., 2003).
Health benefits of bioactive components of milk fat
Milk fat is composed of components which are needed for normal performing of physiological functions of human It contains a number of components which are metabolically active such as: sphingolipids, conjugated linoleic acid (CLA), butyric acid, other fatty acids, vitamins A and D. A variety of health benefits have been associated with these compounds.
A variety of health benefits have been associated with sphingolipids and their digestion products, ceramides and sphingosines. They are suggested to be important in prevention from carcinogenesis, reduction of serum LDL cholesterol, regulation of the immune system and inhibition of foodborne pathogens.
Conjugated linoleic acid which is a naturally occurring fatty acid found in animal and dairy fats, exhibits a number of health benefits. CLA is found in relatively large quantities in the milk and/or meat of ruminant animals and appears to be metabolized differently than linoleic acid. In the diet of many consumers, meat and dairy products would be a significant source of CLA. (Barbosa et al. 2003).
Reported beneficial health-related effects of CLA include anticarcinogenesis, antiatherogenic, antidiabetagenic and immune modulating properties. Most of the research on CLA is associated with its anticarcinogenesis properties. CLA reportedly has anticarcinogenesis effects at various stages of cancer development, including initiation, progression and metastasis. Proposed mechanisms of CLA and its anticarcinogenic activities include a reduction in cell proliferation, and prostaglandin metabolism. CLA seems to significantly reduce prostaglandin E synthesis which could inhibit tumour formation (Alkalin et al. 2006).
Natural CLA is known to consist of several positional and geometrical isomers but the cis-9, trans-11, and cis-12, trans-10 are the principal forms present. It is formed as a by-product or intermediate in the microbial biohydrogenation of linoleic acid in the rumen (Christie, 1990; Dhiman et al., 2005).
The rumen bacteria involved in biohydrogenation have been classified into two groups, A and B, based on their metabolic pathways. To obtain complete biohydrogenation of polyunsaturated fatty acids (PUFA), bacteria from both groups are generally required (Bauman et al., 2003).
Two key biohydrogenation intermediates are trans-11 18:1 (vaccenic acid; VA) formed
from linoleic and linolenic acids and cis-9, trans-11 conjugated linoleic acid (CLA) formed in the biohydrogenation of linoleic acid. These intermediates are present in appreciable quantities in ruminant fat at a ratio of about 3:1 (Bauman et al., 2003).
Figure 1: Pathway of biohydrogenation of linoleic and a-linolenic acids to stearic acid by rumen microorganisms (Bauman et al., 2003)
In the rumen cis-9, trans-11 CLA is only a transitory intermediate and instead it is VA that accumulates. The difference is because most of the cis-9, trans-11 CLA found in ruminant fat originates in the mammary gland and adipose tissue from endogenous synthesis involving the enzyme delta-9 desaturase with rumen-derived VA as the substrate.
Figure 2: Metabolic pathways involved in the biosynthesis of CLA in ruminants (Griinari
et al., 2000)
This discovery is of special importance in considerations of " designing foods'" because cis-9, trans-11 CLA is among the most potent naturally occurring anti-carcinogens (Bauman et al., 2003).
Butyric acid have been suggested to have an anti-tumour role and it is especially effective in colon cancer prevention. Vitamin A and D and B-carotene are also offered as natural anticancerogens in numerous reviews. As health benefits of these bioactive components of milk fat has been studied mostly in vitro conditions, in vivo researches are not sufficient. So, further research is required to establish the contribution of these dietary components to host metabolism and health (Alkalin et al., 2006).
Conclusion
Recent discoveries in the functional foods area indicate that specific fatty acids produced in the rumen may have beneficial effects on human health, and there is a increased interest in the possibility of designing natural food products with enhanced levels of these fatty acids.
Bovine milk fat represents a rich source of biologically active molecules, many of which offer potential for commercial exploitation in health-promoting functional food products.
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