Prevention of oil migration in palm mid fraction and palm olein using a stabilizer rich in behenic acid

Oil loss is a common problem in high oil volume fraction fat-structured foods, where trans fatty acids are absent and saturated fatty acids minimized. Usually a stabilizer “fat”, rich in behenic and stearic acids is added to these products. This stabilizer significantly reduces oil migration and loss; however, the mechanism by which it exerts its effect is not known. Here we study the structure and oil loss characteristics of blends of palm mid fraction (PMF) and palm olein (PO) mixed with a commercial stabilizer of fully hydrogenated cottonseed and rapeseed oils added at 1.25, 3.5, and 7% (w/w) levels. The addition of as little as 1.25% stabilizer reduced oil migration from 13% to ~ 2% for the 80:20 PMF/PO blend and from 29% to ~ 3.5% for 20:80 PMF/PO blend after 14 days of storage at 20 °C, as judged from a filter paper assay. Polarized light microscopy results demonstrated that addition of stabilizer decreased fat crystal size and lead to the formation of a denser network with smaller pores. The rate of crystallization, determined by monitoring increases in solid fat content as function of time by pulsed NMR, increased upon addition of the stabilizer as indicated by decreases in the half-time of crystallization. Addition of stabilizer lead to an increase in the mechanical strength of the material, as indicated by increases in breaking force. Differential scanning calorimetry showed the formation of a new fraction, intermediate between the high melting fractions in both PMF and PO and the stabilizer upon incorporation of the stabilizer in the blends. We hypothesize that the stabilizer helps the formation of this new fraction which has a higher nucleation rate and thus forms a denser network of small crystals with an improved ability to bind and retain oil.