Conjugated linoleic acid (CLA), a bioactive component of milk fat, has health benefits. But, CLA content is significantly reduced during ultra-high-temperature treatment. Interestingly, our recent investigation on the effect of high-pressure high-temperature (HPHT) showed that CLA in milk was retained up to 90% when 1g catechin was added to 1 kg of milk, regardless the conditions used (60-120�C and 100-600 MPa). These findings suggest that the use of antioxidants enhance CLA retention in milk. However, antioxidant effectiveness and mechanism to capture free radicals or react with the dissolved oxygen to retard the free radical reactions have not been studied under HPHT conditions. In this study, the use of different antioxidants on the CLA retention in milk treated by HPHT was evaluated. Milk rich in CLA was first saturated with oxygen, followed by the addition of catechin, cysteine, ascorbic acid, tannic acid, gallic acid, caffeic acid or cumaric acid (500 mg/kg untreated milk). Then, samples were treated at 600 MPa, 120�C and 0-15 min. The dissolved oxygen was measured before and after each experimental run. CLA in the presence of oxygen was more stable in pressurized samples compared to the control. The analysis of oxidized CLA and consumed oxygen suggest that pressure induced isomerization of CLA through free radical mechanism. Antioxidants added to milk samples enhanced the retention of CLA when treated by HPHT. Gallic acid yielded the highest retention of CLA followed by catechin. During HPHT, the rate of oxygen quenching was higher than the oxidation rate of CLA, which might avoid isomerization and therefore preserving the biological activity of CLA. Thus, the combination of HPHT and the use of phenolic acids as antioxidants can produce milk beverages rich in CLA, addressing the growing market of functional drinks.

Impact of antioxidants in the retention of conjugated linoleic acid in milk treated by high-pressure high-temperature

246th National Meeting (2013)

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