EFFECT OF ENZYMATIC TRANSESTERIFICATION ON THE MELTING-POINTS OF PALMSTEARIN SUNFLOWER OIL MIXTURES

Transesterification with lipases may be used to convert mixtures of fa ts to plastic fats, making them more suitable for use in edible produc ts. In our study, 1,3-specific (Aspergillus niger, Mucor javanicus Rhi zomucor miehei, Rhizopus javanicus, and Rhizopus niveus) and nonspecif ic (Pseudomonas sp. and Candida rugosa) lipases were used to transeste rify mixtures of palm stearin and sunflower oil IFS-SO) at a 40:60 rat io in a solvent-free medium. The transesterified mixtures of PS-SO wer e analyzed for their percentage free fatty acids (FFA), degree and rat e of transesterification, solid fat content, slip melting point (SMP), and melting characteristics by differential scanning calorimetry. Res ults indicated that Pseudomonas sp. lipase produced the highest degree (77,3%) and rate (50.0 h(-1)) of transesterification, followed by R. miehei lipase at 32.7% and 27.1 h(-1), respectively. The highest perce ntage FFA liberated was also in the reaction mixtures catalyzed by Pse udomonas sp. (2.5%) lipase and R. miehei (2.4%). Pseudomonas-catalyzed mixtures produced the biggest drop in SMP (13.5 degrees C) and showed complete melting at below body temperature. All results indicated con version of the PS-SO mixtures to a more fluid product. The findings al so suggest that the specificity of lipases may not play a significant role in lowering the melting point of the PS-SO mixtures.