Conjugated linoleic acid content of milk and milk products II. Conjugated linoleic acid content of cheese, butter, other milk products and some other foods (A review)

Abstract

During the production of the processed cheese or the Indian ghee the applied heat treatment and also certain steps of the processing of the food industry can increase the CLA content. Heat treatment involves significant CLA formation mainly when the protein content of the product is high. On the other hand roasting and cooking of meats does not change significantly the CLA content and the CLA content of meat and vegetable based tinned food did not change significantly during processing. The CLA content of chocolates, cakes and biscuits depend on the milk fat content of the product. In the case of milk products made by fermentation, their CLA content can change during the fermentation, since some Propionibacteria spp. used in certain types of cheese production are able to produce CLA from linoleic acid in microbiological nourishment conditions. During the actual cheese production though no differences were found between the CLA content of cheeses containing Propionibacteria and those, which were not. According to some experts the CLA content of cheeses can increase during ripening, but others have not experienced significant change in the CLA content of semi-processed goods after the implanting of the starter culture. In most cases the CLA content of cheeses had no significant differences from the CLA content of milk as used for cheese production. If synthetic CLA is given to butter, the free fatty acids can be transmitted to triacyl-glycerol molecules by enzymatic esterification, and using that method the increase of CLA content can also be solved. A fraction can be reached from the butter that is rich in CLA using supercritical fluid extraction. If it is desirable the increase of the CLA content of food-products can also be accomplished. The simplest and uncertainty method seems to be giving synthetic products to the end-product. Nowadays though consumers give preference to food-products containing only natural components. If the CLA content of the milk, which is the raw material for milk products, is increased with feeding, that might change the composition of the milk, since the undesirable fatty acid quantity can also be increased. The increase of the CLA content of cheeses with CLA producing starter cultures seems to be a promising possibility, but the completed experiences resulted without success. Several authors could not demonstrate any considerable amount of CLA in margarine and in vegetable oils, while others covered significan t (0.02-2 g/100 g oil) amounts. The reason for the differences according to the assumptions is possibly due to the different processing methods, since the formation of c9,t11-C18:2 CLA can happen during the partial hydrogenation of oils.