The Study On Quality Defects And Improvement Of Palm Oil-based Margarine

The palm oil-based margarines have common defects of over-hardness and poor whipping, which seriously affect its processing and application. This paper compares two typical commercial margarines, in terms of chemical composition and crystallization behavior difference as to their effects on margarine texture.The triacylglycerols (TAG) composition and crystal types of margarine A and B was studied. High performance liquid chromatographic (HPLC) analyses showed that margarines B has higher content of monounsaturated TAGs (POP, PLP, POS) and small amounts of medium chain TAGs. X-ray diffraction analysis revealed thatβ′was the predominant polymorph in margarine B, whileβl was in margarine A. In the 5-45°C range the SFC of margarine B was higher than that of margarine A.Then the isothermal and non-isothermal crystallization of margarine A and B were tested under 15℃, 20℃, 25℃, 30℃, and at cooling rates of 1℃/min, 5℃/min, 10℃/min, 20℃/min, respectively; and their kinetics were fitted using the Avrami and Jeziorny model, respectively. For isothermal crystallization, at temperatures≥25℃, the rate constant K of Sample B were lower than Sample A which indicate in harder to crystal. For non-isothermal crystallization, the crystallization degree depended on the cooling rate strongly. Under the non-isothermal cooling rate, nucleation mechanism and crystal growth became more complicated. Different crystallization mechanism causes different morphologies of crystals; as revealed by the scanning electron microscopy(SEM) images and polarized light microscopy(PLM)images, the morphology of the crystal networks in Sample B is much loose and porous and there were many big-sized and fluffy spherulite clusters in Sample B. The morphologic observations showed that formation of spherulite clusters has an important influence on margarine texture.The formulation of base oil and emulsifiers as well as the process parameters were optimized as follows: palm oil stearin/palm oil middle fraction/palm kernel oil = 66.47%:12.85%:4.18% (total oil phase content 83.5%); propylene glycol ester/lecithin = 3:1, addition 0.5%; water content 16%; precooling temperature 37℃, flow rate 20L/h; A-unit (chilling unit) working temperature -10℃, scraper blade speed 300r/min; B-unit (pin worker) speed 100r/min; post-ripening at 25℃for 2 days. The hardness of the margarine prepared using the optimum conditions at room temperature was 327g and the specific gravity of its creaming was 0.65 after beating 30 minutes which proved that adjustment of formulation and process can improve the quality of the palm oil-based margarine..Finally the margarine prepared by pilot plant was used pound cake test and sensory evaluation of cake showed it meet the requirements of baking oil.