Interaction between palm stearin and milk fat fractions and their implication for the preparation of cold spreadable fats

The demand for convenience (e.g., spreadable at refrigeration temperature) and health (inclusion of polyunsaturated fat and absence of trans fatty acids) is reflected in the composition of the fat spreads available in the market today. Two types of fat spreads are available, i.e. butter and margarine. In the production of cold spreadable fat, different oils and fats are blended to make a product that is spreadable at refrigerated temperature. However, incompatibilities between fats limit the use of modified fat in confectionery products. To understand interaction between palm stearin and milk fat fraction, the effects of blending and interaction on the physicochemical characteristics of the blends were studied. Anhydrous milk fat (AMF) was fractionated by two-stage acetone fractionation process to produce three fractions: high melting (HMF), middle melting (MMF) and low melting (LMF) fractions. To study purity, laboratory milk fat fractions were compared with commercial milk fat fractions. Then palm stearin and milk fat fractions were blended in various ratios. The characteristics of the palm stearin based blends were tailored to resemble oil blends extracted from commercial soft margarine. It was found that the purity of laboratory fractions were better than the commercial fractions. Eutectic interaction was observed in the bends, indicating the limited compatibility between two fats. Results showed that eutectic interactions could be eliminated by interesterification. However a bigger increase in slip melting point (SMP) and solid fat content (SFC) restrict its use in cold spreadable fat. Formulation diagrams showed that cold spreadable fat could be produced by blending of 16.7% of soft palm oil stearin, (sPOs), 16.7% of MMF and 66.6% of LMF before interesterification. Similarly, uninteresterified ternary blend containing 9% of hard palm oil stearin (hPOs), 15% of MMF and 76% of LMF could be used to produce the cold spreadable fat. However, the texture of the product may change during storage due to eutectic effect. Interesterification of these blends results in increase SFC>32% at 10˚C in all ternary mixture. This increase caused reduction in spreadability and hence rendered them less suitable as cold spreadable fats