Discipline: yogurt; Keywords: CLA, microbial, physical, chemical, sensory, yoghurt.

Conjugated linoleic acid (CLA) has the ability to inhibit growth in a number of human cancer cell lines. It is also immune-modulating and growth-promoting and was shown to decrease fat mass without significantly affecting body weight. In terms of prevention of heart disease, CLA depressed total cholesterol and lowered the ratio of low-density lipoprotein (LDL) to high-density lipoprotein (HDL). These positives are the main reason why dairy consumption became a strong recommendation as part of the human diet because dairy milk was found to be the richest natural source of CLA. The average CLA level in milk fat is in the range of 0.559.12 mg/g fat, depending on the fat concentration in the product. It is recommended that a 70-kg human should consume about 3.03.5 g CLA per day, which is more than three times the current daily consumption of the average adult. The amount of CLA in dairy products is, therefore, still too low to have maximum health benefits, and some 40 L of full-cream milk must be consumed per day to reach the full recommended dietary allowance (RDA). Direct supplementation is thus required and therefore the aim of the study cited below was to study the effect of synthetic CLA fortification on the microbial, physical, chemical and sensory properties of yoghurt, in order to establish whether a functional food which complies with the RDA for CLA can be manufactured. 

Yoghurt was prepared by adding synthetic CLA (‘Tonalin’) at levels of respectively 0%, 25%, 50% and 100% of the RDA for CLA. None of the levels had an effect on the viability and counts of the yoghurt lactic acid bacteria (LAB), which is important because of the positive health benefits of live LAB cultures. The non-fat solid content was increased and consequently the free water content was reduced with increasing CLA. This may be regarded as positive as the yoghurt is possibly ‘protected’ against the effects of syneresis by the contribution of CLA to the higher solid content. The physical properties such as viscosity and pH increased with increasing CLA levels and the fat content increased. The latter result may be regarded as negative by most consumers. Therefore, it is necessary to inform the consumers that the additional fat is mainly CLA, which is metabolized differently by the human body than other fatty acids and would not have a negative impact on health. The oxidative stability of the yoghurt during a six-week shelf life period was improved with the addition of CLA. The inclusion of CLA also had an effect on the fatty acid (FA) composition of the yoghurt. The polyunsaturated fatty acids (PUFAs) increased, which resulted in a reduction in the percentage saturated fatty acids (SFAs). This is positive, as SFAs are negatively associated with human health. A drastic increase in CLA isomers occurred with increased CLA inclusion levels. At the highest CLA inclusion level, a consumer will receive 100% of the CLA needed per day to obtain maximum health benefits, if a 100 g of the CLA-fortified yoghurt is consumed. The yoghurt was accepted by the consumer panel regardless of the level of CLA inclusion. This is a major positive factor, as an unacceptable product will not sell. Potentially then, the total recommended daily amount of CLA can thus be reached by consuming only 100 g of yoghurt. 

It was concluded that by elevating the yoghurt CLA levels with the addition of a synthetic CLA product, such as Tonalin, will create a more stable yoghurt product. Supplementation of yoghurt with synthetic CLA may therefore be considered for the development of a new functional dairy food product. 


T-J. FAIHST, J. MYBURGH, C. BOTHMA, C. HUGO & A. HUGO, 2017. Effect of conjugated linoleic acid supplementation on the microbial, physical, chemical and sensory properties of yoghurt. International Journal of Dairy Technology 70, 228-236.