Conjugated Linoleic Acid in Milk and Fermented Milks: Variation and Effects of the Technological Processes

Abstract

Background: Conjugated linoleic acid (CLA) is a generic term used to describe a group of geometric and positional isomers of linoleic acid with a conjugated double bond system. CLA-isomers have been widely studied because of their important biological activity and their protective effects against several diseases, such as obesity, atherosclerosis, chronic inflammatory diseases, and cancer. Consequently, these biomolecules have attracted much attention from the dairy industry, since they are naturally found in ruminants' milk, and because the development of CLA-enriched dairy foods can be a good economic opportunity given the growth of the functional foods market, in which the dairy industry plays an important role. Objectives: This work presents a comprehensive review of the following aspects: (i) The synthesis and concentration of the CLA-isomers in milk, and the main strategies employed to increase their content in a natural manner; (ii) The influence of the main technological treatments applied to milk on the concentration of CLA-isomers; and (iii) The effects of milk fermentation on the content of CLA-isomers, and the challenges of this technological process, which has been though as a promissory alternative to naturally increase the content of CLA in fermented dairy products. Methods: Information available in various databases was reviewed. A total of 103 articles were selected on the basis of their relevance and scientific-technical quality. Results: The CLA concentration in cows' milk normally ranges between 2 and 37 mg/g fat, and is mainly affected by the dietary regime offered to the animals. From the total CLA-isomers, rumenic acid represents between 75 and 90%. The technological processes normally applied to milk (thermal processing, high pressure processing, and fermentation) might cause slight changes on the CLA concentration, but the mechanisms causing these changes have not been still established. The increase in CLA concentration by milk fermentation is strain-dependent, because of the different linoleate isomerase activity of the species. . Conclusions: Although several studies have reported increases in the concentration of CLA in milk and fermented milks in a natural manner, they are fairly moderate, and the obtained levels of CLA are significantly lower than those recommended to achieve therapeutic effects.

Biological Activity of Sacha Inchi (Plukenetia volubilis Linneo) and Potential Uses in Human Health: A Review

“…Sources of high daily impact are represented by milk and dairy products, like yoghurt, already supplemented with components rich in linoleic fatty acid as for example fish and sunflower oil, canola and soy, showing a moderate increase of unsaturated fatty acid content ( 102 - 104 ). Supplementation of yoghurt with sacha inchi seeds has been studied recently, revealing an increase of the levels of ALA and LA of 25- and 50-fold respectively, from an average PUFA content of 3.60 to 81.51% in the modified product compared to the control, concomitant with reduced content of saturated fatty acids (palmitic and stearic) from 76 to 84% and sensory acceptance by >70% consumers (volunteers) ( 105 ).…”

Fatty Acids Profile, Trans Isomers, and Lipid Quality Indices in Smoked and Unsmoked Cheeses and Cheese-Like Products

“…The principal natural sources of CLA in the human diet are dairy products from ruminant animals (such as milk, yogurt, and cheese) and meat. The content of CLA in milk ranged from 2 to 23.6 mg CLA/g lipid [72] with cis9, trans11 C18:2 as the major isomer (75% to 90% of total CLA) [73,74]. The smoked and the unsmoked cheeses were characterized by a higher content of cis9trans11 C18:2 (CLA) compared to cheese-like products (Figure 2, Table 3).…”

Biotechnological approaches for the production of designer cheese with improved functionality

“…Major CLA isomers include the biologically active cis ‐9, trans ‐11 CLA, trans ‐10, and cis ‐12 CLA (de Almeida et al., 2015). Cheese‐derived CLA exhibit antioxidative, antihypertensive, anticarcinogenic, antiadipogenic, antiinflammatory, antidiabetic, and antiobesity properties (Table 2; Bassaganya‐Riera et al., 2012; Florence et al., 2009; Gutiérrez, 2016; Koba & Yanagita, 2014; Murru et al., 2018; Renes et al., 2019). CLA isomers are naturally found in milk and are formed upon incomplete dietary fatty acids biohydrogenation in the rumen of cows.…”