Effect of processing and storage on the conjugated linoleic acid (CLA) levels of dairy products manufactured from CLA enhanced milk

Dairy products, high in conjugated linoleic acids (CLA), show promise as functional foods due to their reported numerous health benefits.Conjugated linoleic acids, specifically the cis-9, trans-l1 isomer have been shown to have activity as anti- oxidants, anti-carcinogens and anti-atherosclerotic agents.They also have been reportedto have beneficial functions in reducing body fat and in modulating the immune system.For this study three experiments were conducted to determine the effect of dairy lactation diets, processing technologies and storage on CLA levels in milk and processed dairy products.The processing variables examined were heat treatment, the addition of whey protein concentrate and probiotic cultures.Sensory evaluations of products were performed to compare the taste of dairy products manufactured from ClA-enhanced milk to those made from control milk.Conjugated linoleic acid-enhanced milk was obtained from dairy cows fed forage and barley grain based diets supplemented with either fresh forage and solin (FF- solin) or fishmeal and solin (FM-solin).Control and ClA-enhanced milk were processed into pasteurized milk, butter and fermented dairy products using standard procedures.Fatty acids of milk and dairy products were analyzed by gas chromatography.Results indicated that supplementing dairy cow diets with solin and fishmeal significantly increased CLA levels in milk (2.78%) compared to control diets (0.40%).Processing milk into pasteurized milk and fermented dairy products, and their subsequent storage had no significant effect on CLA levels.Similarly, various heat treatments of milk had no significant effect on the levels of CLA.Processing milk into butter, however, significantly decreased the level of CLA by 4.5%.The addition of different probiotic cultures in yogurt and kefir production had no significant effect on CLA levels when compared to products without probiotics.Conjugated linoleic acids decreased by 9% when whey protein concentrate was added to yogurt at either 6 or lÙYo.Sensory panelists found the flavour of ClA-enhanced dairy products to be acceptable and comparable to control products.Results from feeding trials and sensory studies indicate the feasibility of producing ClA-enhanced dairyproducts.This will position the dairy industry as an important contributor to the functional food industry.