Abstract #M289

# M289
Physical characterization of fat supplements highly enriched in palmitic and stearic acid.
R. P. Shepardson*1, E. Bazileyskaya1, K. J. Harvatine1, 1Penn State University, University Park, PA.

Fatty acid (FA) supplements are widely used in lactating cow diets to increase energy intake. Previous published research has reported that supplements with moderate enrichment (~85%) of palmitic acid have expected digestibility, while very high enrichments (~98%) have lower digestibility. Saturated FA have the potential to form organized secondary structures at high purity. Differential scanning calorimetry (DSC) is a thermal technique commonly used in material science to measure the change in heat flow as energy is absorbed or released from a sample during heating. Our hypothesis was that a supplement with a very high enrichment would differ in physical characteristics due to the formation of a secondary structure, which may contribute to a decreased digestibility. A 98% stearic acid (SA; 98.5% C18:0, 0.4% C16:0), 98% palmitic acid (PA; 98.5% C16:0, 0.7% C18:0), and a mixture of palmitic and stearic (PA/SA; 54.5% C16:0, 44.5% C18:0) sample were used for this characterization. Sample FA profile was determined by gas chromatography with a flame ionization detector. Data from DSC was gathered on a Q600 SDT (TA Instruments). Briefly, ~40 mg of sample was heated at 5°C/min from 25°C to 110°C. TA Universal Analysis software (TA Instruments) was used to determine melting temperature, and total enthalpy of melting (area under the curve). Triplicate runs were highly reproducible. Melting temperature of the PA/SA mixture was 61.2°C, similar to the reported melting temperature of PA (62.9°C). However, the melting temperatures of the high purity PA and SA were increased to 67.8°C and 73.7°C, respectively. The enthalpy of melting was increased 12.5% in the high purity PA compared with the PA/SA blend. Melting enthalpy for the high purity SA supplement was increased 3.5% from the high purity PA and 16.4% from PA/SA mixture. Although melting temperatures are well above body temperature, increasing the energy required to melt the sample is indicative of physical characteristics of the supplement expected to decrease digestibility.

Key Words: fatty acid supplement, lipid, melting point