Relative impact of α-tocopherol, copper and fatty acid composition on the occurrence of oxidized milk flavour

Abstract

The oxidative process in milk fat, resulting in spontaneous oxidized off-flavour (SOF), is commonly assumed to depend on contents of pro- and antioxidants in milk and availability of fatty acids acting as their substrate. An important antioxidant in milk is alpha-tocopherol whereas the most potent prooxidant is the metal ion copper. The separate effects of alpha-tocopherol, copper, and milk fatty acid profile, and their combined effect on SOF development were examined in milk from 44 multiparous cows fed different roughage types and different amounts of dietary, unsaturated fat. A clear association between concentrations of copper and poly-unsaturated fatty acids in milk and the risk for developing SOF was found. Heritability estimates suggest that occurrence of SOF is partly under genetic control which indicates that milk quality may be compromised if breeding bulls are selected that carry genotypes predisposing for milk prone to develop SOF.

Effects of Pro‐Oxidants and Antioxidants on the Total Antioxidant Capacity and Lipid Oxidation Products of Milk During Refrigerated Storage

“…Lipid oxidation reactions can occur in milk due to the imbalance of pro‐oxidants and antioxidants (Nielsen and others ). The major pro‐oxidants in milk are light, metals, and unsaturated lipids (Rysstad and others ; Timmons and others ; Juhlin and others ). The antioxidative factors of milk include ascorbic acid, α‐tocopherol, and carotenoids (St‐Laurent and others ; Laguerre and others ; Hall and others ).…”

Carotenoids, ergosterol and tocopherols in fresh and preserved herbage and their transfer to bovine milk fat and adipose tissues: A review

“…α-Tocopherol is an important antioxidant in milk preventing oxidative changes of unsaturated fatty acids. The processes result in spontaneous oxidised off-flavour (Juhlin et al 2010). Havemose et al (2004) determined a higher antioxidative capacity (including also carotenoids) in milk of cows fed grass silage as compared with milk from cows fed maize silage.…”

Identification of objectionable flavors in purported spontaneous oxidized flavor bovine milk

“…Juhlin et al (2010a) claimed that the problem might be partially genetic, especially in the variability of copper levels during lactation of individual cows. In a later study, the group also asserted that a significant correlation was present between PUFA, copper levels, and SOF formation, although they noted that precisely defining the levels of substrates and pro-and antioxidants directly responsible was exceedingly complex and required further study (Juhlin et al, 2010b). Timmons et al (2001) further described a link between increased SOF with higher levels of PUFA combined with a higher presence of copper within milk.…”