Sensory Detection and Recovery by Acid Degree Value of Fatty Acids Added to Milk

¹ Department of Food Technology and Science, The University of Tennessee, Knoxville 37901-1071
² Department of Food Technology and Science, The University of Tennessee, Knoxville 37901-1071

To evaluate the relationship between acid degree value and rancid off-flavor, milk samples were supplemented with varying concentrations of selected fatty acids. Recovery of added fatty acids into fat phase was influenced by level of supplementation and chain length. Short-chain fatty acids (C₄ to C₈) when added to milk at concentrations .55 µmol/ml did not enter the fat phase recovered by acid degree value procedure in quantities comparable with those of similarly added medium- (C₁₀ to C₁₆) or long-chain (C_18:0 to C_18:1) fatty acids (.56 vs. 2.14 or 3.68 µmol FFA/g of fat). Except for C₄, percentage recovery into the fatty phase tended to increase with increased rate of supplementation. Gas chromatographic procedures documented that chain length affected partitioning of fatty acids into the recovered fat phase. Long- and medium-chain fatty acids contributed more to the acid degree value than short-chain fatty acids because their hydrophobic nature resulted in their greater presence in the recovered fat. Flavor detection threshold for C₄ was low relative to that for C_18:1 (.20 vs. .55 µmol/ml). Capric acid (C₁₀) could not be detected at .55 µmol/ml. Results indicate that acid degree value does not measure the short-chain fatty acids, which contribute to the threshold sensory detection of rancid off-flavor.

Key Words: fatty acids • acid degree value • rancidity

Submitted on January 12, 1990
Accepted on July 30, 1990

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