Physico-Chemical Characteristics of Canadian Milk Fat. Unsaturated Fatty Acids

Abstract

Seasonal and regional variations in ethenoid acids of Canadian milk fat have been established from 327 authentic samples, representative of every month of the year and of 29 creameries across Canada. About 30% of the fatty acids in milk fat were unsaturated; 12% of these were polyunsaturated acids, with one-third being of the conjugated type. The average values and the 95% fiducial limits, in brackets, were as follows: conjugated dienes 1.13% (0.24–2.01), conjugated trienes 0.021% (0.001–0.033), conjugated tetraenes 0.002% (0.000–0.005), nonconjugated dienes 1.31% (0.78–1.84), nonconjugated trienes 0.89% (0.32–1.46), nonconjugated tetraenes 0.19% (0.07–0.31), nonconjugated pentaenes 0.12% (0.02–0.22), nonconjugated hexaenes 0.042% (0.001–0.083), total polyethenoid acids 3.71% (2.82–4.60), monoethenoid acids 26.1% (21.8–30.4), ethanoid acids 65.8% (60.5–71.1). The ethanoid acids which varied with the season were the conjugated dienes and trienes, the nonconjugated trienes and pentaenes, and the monoethenoid acids. They were all higher in summer than in winter milk fat. Triene values were higher in Ontario, and monoethenoid acids were higher in the coastal than in the other provinces. The most significant feature of the seasonal variations was the close relationship between iodine value, monoethenoid acids, conjugated dienes, and non-conjugated trienes. Of the total iodine value, 74% was contributed by monoethenoid acids, 14% by dienes, 8% by trienes, and 4% by tetraenes, pentaenes, and hexaenes. The occurrence of conjugated dienes in relatively large amounts and of hexaenes in all samples is of special interest as characteristics of milk fat. © 1963, American Dairy Science Association. All rights reserved.