Effect Of Emulsifiers On Crystallization Behavior In Palm Oil Based Margarine

Palm based oil is widely used in margarine and other specialty fats due to high-yield, low cost and excellent stability, but its crystal defects bring inconvenience for industry of specialty oil processing, such as post-harden of margarine, blooming of chocolate. This research used palm oil stearin POS, palm oil middle fraction PMF and palm kernel oil PKO to investigate based oil formulas and effects of emulsifiers on crystallization behavior in emulsified system, which guided the formula of margarine, the selection of emulsifiers and quality improvement.Firstly, through the analysis of the basic physical and chemical properties and crystalline characters of POS, PMF and PKO, it found that can be as skeleton of crystalline network and rapidly melted to give the product a good taste, which were suitable for based oil of margarine. According to mixing regression design, PLM and iso-solid curves, it could be found that the best formula is POS:PMF:PKO 0.45:0.45:0.1.Then,choosing DMGS,PGMS,PGE,MONO-DIGS,LACTEM and SE,and concentration are 0.3%, 0.5%, 0.7%, investigated average particle size and surface tension for emulsified system,it found that 0.5%PGE had minimum average particle size,0.3%DMGS and all concertration of SE had larger particle size.SE reduced surface tension greatly.From analysis of PLM,SFC,hardness and crystal morphology.It found that PGE and SE corresponded small crystalline size at 20℃,accompanied by flocculent crystalline,and others were dendrite or granular,but Db of PGE and PGMS were maximum.Adding MONO-DIGS,PGE,LACTEM, values of SFC at 21.1℃were relatively large.Adding PGE and SE had maximum values of hardness.Adding PGE correspondedβcrystal,PGE had near quantity ofβandβ'.When added LACTEM and MONO-DIGS, it appearedβ' crystal. The rest were dominated byβ'crystal.Using Avrami and Gompertz model to analyze the isothermal crystallization kinetics. Gompertz model is more applicable for this system. In Avrami model, it was a critical temperature between 25℃and 30℃, leading to different nucleation and growth mechanism, PGE accelerated crystal growth, but DMGS inhibited crystalline growth. In Gompertz model, it found that PGE not only accelerated the crystal nucleation, but also accelerate the growth, DMGS and SE had strongest inhibitory effect on nucleation.Non-isothermal crystallization kinetics was described by Jeiorny equations, unsaturated components had a better fit, the values of n were lower than the isothermal crystallization, values of n higher for unsaturated components,delegating the most complex mechanism of crystallization.Finally, effect of formulated emulsifiers on crystallization behavior was researched. Compared to single emulsifier, the SFC values were higher in whole.Hardness of those system was reduced,but had difference degree.It didn't appearβin all formulations.Gompertz model showed that DGMS:LACTEM2:8 accelerated nucleation, PGE:SE5:5 accelerted crystal growth.The results of non-isothermal crystallization showed that in saturated component crystallization rate of PGE:SE2:8 was the fastest, in unsaturated component crystallization rate of DMGS: LACTEM2:8 was the fastest.