Abstract
A mixture of beef tallow with rapeseed oil (3:1 wt/wt) was interesterified using sodium metoxide or immobilized lipases from Rhizomucor miehei (Lipozyme IM) and Candida antarctica (Novozym 435) as catalysts. Chemical interesterifications were carried out at 60 and 90 oC for 0.5 and 1.5 h using 0.4, 0.6 and 1.0 wt-% CH3ONa. Depending on the catalyst used enzymatic interesterifications were carried out at 60 oC for 8 h (Lipozyme IM) or at 80 oC for 4 h (Novozym 435). The catalysts doses were kept constant (8 %) but the water content in catalysts varied from 2 to 10 %. The starting mixture and the interesterified products were separated by column chromatography into a pure triacylglycerol fraction and a non-triacylglycerol fraction, which contained free fatty acids, mono- and diacylglycerols. It was found that the concentrations of free fatty acids and partial acylglycerols increased after interesterification. The slip melting points and solid fat contents of the triacylglycerol fractions isolated from interesterified fats were lower when compared with nonesterified blends. The sn-2 and sn-1,3 distributions of fatty acids in the triacylglycerol fractions before and after interesterification were determined.These distributions were random after chemical interesterification and near random when Novozym 435 was used. When Lipozyme IM was used, the fatty acid composition at the sn-2 position remained practically unchanged compared with the starting blend. The interesterified fats and isolated triacylglycerols had reduced oxidative stability, as assessed by Rancimat induction times. The addition of 0.02 % of BHA or BHT to the interesterified fats improved their stabilitie.
Highlights
The annual European production of beef tallow is about 1.42 million tonnes (Gunstone, 2000) with the annual production in Poland being about 0.12 million tons
The Free fatty acids (FFA) and MAG + DAG contents in interesterified samples increased when compared with the starting blend and these increases were proportional to the temperature and time of reaction and to the catalyst concentration
The relatively large contents of DAG in the interesterification products are presumably caused by the reaction of MAG with FFA and by the high amount of catalyst used
Summary
The annual European production of beef tallow is about 1.42 million tonnes (Gunstone, 2000) with the annual production in Poland being about 0.12 million tons. Because of its high melting point and low level of polyunsaturated fatty acids, beef tallow is considered a less valuable fat not suitable for direct human consumption. Minor quantities of beef tallow are used for edible purposes such as frying fats or shortenings, tallow should be modified before use. One of the possible ways of tallow modification is its interesterification with vegetable oils. The selection of vegetable oil depends on regional production. In Poland only rapeseed oil can be taken into account, as its annual production is about 0.35 million tons (Gunstone, 2001)
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