Factors Related to the Occurrence of Trimethylamine in Milk1

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Abstract
The overall objectives of this research were to (a) identify the odor threshold for trimethylamine (TMA) in milk and determine how precisely different concentrations are delineated by taste, and (b) investigate the relationship of different factors to the occurrence of TMA flavor in milk of cows grazed on wheat pasture. The odor threshold for TMA in milk, defined as detection by 50% of a panel untrained in milk judging, was determined to be 1 ppm. Trained milk judges detected 5 ppm TMA in milk in every instance, but were not able to distinguish between 5 and 10 ppm TMA. There appeared to be a positive relationship between the amount of TMA administered orally to cows and its intensity in milk 2 h later. There was a linear relationship between amount of wheat forage consumed as well as stage of maturity of the forage and TMA flavor in milk. Feeding of grain or silage plus grain either before or after grazing wheat pasture had little influence on TMA milk scores. Feeding of alfalfa hay between grazing wheat pasture and milking tended to increase TMA milk scores. There was significant variation among cows in TMA milk flavor scores in all trials.