Abstract #T40

# T40
Effect of temperature variation on raw whole milk density and its impact on milk payment system for Irish dairy Industry.
P. Parmar*1, J. T. Tobin1, J. Grant3, J. A. O'Mahony2, L. Shalloo1, 1Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland, 2University College Cork, Cork, Ireland, 3Teagasc Food Research Centre, Ashtown, Dublin, Ireland.

Variation in temperature induces variance in milk density and estimation of fat content and subsequently affects the milk payment since fat content is an integral part of multiple component pricing systems. Thus, the objective of this study was to determine the effect in whole milk density due to variations in temperature. Whole milk samples were collected from morning milking of 32 individual dairy cows of national average genetic merit once every 2 weeks over a period of 6 weeks from the Teagasc research farm, in Kilworth, Co. Cork, Ireland. A total of 93 samples were assessed on the rapid testing technique Dairyspec FT system (Make- Bentley) for milk compositional analysis. Density of milk was evaluated using 2 methods, a portable density meter DMA 35 (a standard industrial method for quick results) and desktop version DMA 4500M (a standard lab testing method for higher accuracy levels), and also to compare and determine accurate density factor dependent upon processing temperature for weight-volume calculations. Statistical analysis using ANOVA showed a significant difference in means of densities (F, 78.866 > F-crit., 3.947 and P < 0.01) measured at different temperatures. The results were then analyzed using PROC GLM procedure, SAS software to develop a quadratic model and identify the relationship (linear or curved) between temperature and density. The output indicated a significant nonlinear relationship (P = 0.0008) with the model equation defining the curvature and density-temperature relationship (r2 = 0.659) as Density = 1.033 + 0.0000632 × temp − 0.0000114 × temp2. There was an inverse correlation between whole milk density and temperature (i.e., as temperature increased, milk density decreased). Mean density calculated at 5°C was 1.0332 g/cm3 with corresponding figures of 1.0328, 1.0315 and 1.0300 g/cm3 at 10, 15 and 20°C respectively. This implies that the volume of milk and subsequent total milk solids content estimated at lower temperature (5°C) will be higher than the values estimated at a higher temperature (20°C)

Key Words: whole milk, density, temperature