Chemical and thermal characteristics of buffalo butter oil fractions obtained by multi-step dry fractionation

Abstract

Buffalo butter oil was fractionated by stepwise crystallization at several temperatures between 15–40°C using slow cooling of melted butter oil (80°C) with agitation (10 rpm) in conjunction with vacuum filtration to produce five solid and five liquid fractions. Fractions were analysed for fatty acid (FA) composition, acyl-carbon profile and evaluated for solid fat content (SFC) by pulsed nuclear magnetic resonance and thermal profile by differential scanning calorimeter (DSC). Based on chemical and thermal properties, the fractions were divided into three main groups: high-melting fractions (HMF), middle-melting fractions (MMF) and low-melting fractions (LMF). HMF (slip melting point (SMP) 36.5–45°C) were enriched in saturated long-chain fatty acids and reduced in short-chain fatty acids and unsaturated fatty acids. Conversely, LMF (SMP 12.6°C) were reduced in saturated-long chain fatty acids and enriched in short-chain fatty acids and unsaturated fatty acids. FA composition of MMF (SMP 24.2–29.8°C) lie between those of LMF and HMF. Likewise, high-melting triacylglycerol (HMTAG) were concentrated in HMF (44.17–59.67 mg/100 mg), whereas low-melting triacylglycerol (LMTAG) were predominately in LMF (17.51 mg/100 mg). MMF were enriched in middle-melting triacylglycerol (MMTAG) (44.10–51.67 mg/100 mg). Multi-step dry fractionation caused substantial differences in the thermal profile of the obtained fractions. SFC of HMF and MMF was 17.7–31.5 g/100 g and 4.0–20.5°C g/100 g at 25°C, respectively while LMF was entirely liquid at this temperature. HMF have a significantly higher ( P<0.05) melting characteristics compared with LMF as analysed by DSC with melting enthalpies of 48.46–71.28 J/g for the former and 15.81 J/g for the latter. Melting peak temperature increased from 9.25°C in LMF to 33.54–40.46°C in HMF.