Om. Lai et al., EFFECT OF ENZYMATIC TRANSESTERIFICATION ON THE MELTING-POINTS OF PALMSTEARIN SUNFLOWER OIL MIXTURES, Journal of the American Oil Chemists' Society, 75(7), 1998, pp. 881-886
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.