Effect of the Seasonal Variation of Fatty Acids in Milk Fat on the Sensitivity of a Test for Vegetable Fat Adulteration

The objective of this study was to ascertain whether the sensitivity of a test for vegetable fat adulteration of milk fat might be improved by considering the seasonal variation of the criteria for identifying suspect samples. The test is based on the ratio of the concentrations of butyric acid to oleic acid (C4: C18:1). Sampies of milk fat that exhibit a ratio value greater than 2 standard deviations from the mean can be considered abnormal and possibly adulterated with vegetable fat. For the 6 mo of November through April, when the value of this ratio is typically high, the criteria for identifying suspect samples can be modified, that is, the minimum value of the ratio for pure milk fat can be increased. The minimum amount of vegetable fat in a sample of milk fat that can be detected using this method is reduced for 10.5% to approximately 8.2%.