Food Quality, Safety and Technology by Giuseppina P. P. Lima & Fabio Vianello

Author:Giuseppina P. P. Lima & Fabio Vianello
Language: eng
Format: epub
Publisher: Springer Vienna, Vienna

7.1.1.2 Conjugated Linoleic Acids

The term “conjugated linoleic acid” (CLA) refers to a mixture of positional and geometric isomers of omega-6 essential fatty acids (cis-9, cis-12, C18:2, LA) (Kelly 2001). In ruminants, these isomers are mostly synthesised by some bacteria in the rumen as intermediate compounds of the bio-hydrogenation process, and, partly, in the mammary gland from the endogenous conversion of transvaccenic acid by Δ9-desaturase. In recent years, CLA aroused great interest in the scientific community because several in vivo and in vitro studies highlighted not only its anti-carcinogenic activity but also its anti-atherogenic, anti-obesity, anti-diabetic and immune-stimulating properties (McGuire and McGuire 1999). Cis 9, trans 11 CLA is the biologically more active isomer and accounts for 80–90 % of the total CLA present in milk or meat.

Even if food products derived from ruminant animals, milk in particular, are commonly rich in CLA (Bailoni et al. 2005), attempts are being made at further enriching their contents by means of nutritional strategies (Antongiovanni et al. 2003). The CLA content in milk or meat varies greatly from 0.1 to 2 % of fatty acids (Khanal and Olson 2004). The content of CLA in milk is mainly influenced by the amount and quality of forages. Cows fed with pasture, better if high hill pasture, produced milk with a higher content of CLA than those fed hay or silage (Bortolozzo et al. 2003) (Fig. 7.1). If pasture or fresh forages are not available, fats or fatty feeds can be added to the diet but, in order to avoid the process of bio-hydrogenation in the rumen, these supplements must be ruminally protected. The best protection is their saponification to calcium salts. As an alternative, full-fat oilseeds can be used, provided that they are adequately treated (i.e. extrusion) in order to protect lipids from rumen degradation (Bailoni et al. 2004) (Fig. 7.2).

Fig. 7.1CLA content of milk obtained by cows at pasture (PSR) and with total mixed ration with the addition of toasted (TS) or raw (RS) soybean (Bortolozzo et al. 2003)

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