Oxidative stability of ultra high temperature milk enriched in conjugated linoleic acid and trans-vaccenic acid

Milk naturally enriched in conjugated linoleic acid (CLA) and trans-vaccenic acid (TVA) was ultra high temperature (UHT)-treated at 125-145 °C for 2-20 s and stored at 4 and 25 °C for up to 120 d. The oxidative stability of treated enriched milk was evaluated in terms of changes on the contents of CLA and TVA, dissolved oxygen, hydroperoxides, thiobarbituric acid reactive substance (TBARS) and formation of volatiles. After UHT treatment, more than 78% of CLA and 87% of TVA remained. After 15 d of storage at 25 °C, the CLA and TVA were relatively stable with values in the range of 67-75 and 63-73%, respectively. During storage, CLA oxidized faster than TVA, independently of the UHT treatment and storage conditions. Heptanal was the most abundant volatile resulting from UHT processing and a potential suitable marker for heat treatment of milk rich in CLA and TVA.