In vitro and in vivo Digestibility of Blended and Corresponding Interesterified Fats in Rats

Abstract

The process of interesterification of fat blends namely vanaspati-groundnut oil (40 :60) (vanaspati-GNO). sal fat and groundnut oil (30 : 70) (sal-GNO), sheep tallow and groundnut oil (30 : 70) (ST-GNO),and cottonseed oil (CSO) was found to bring about limited but consistent increase in inuzlro digestibility (compared to starting stocks) during first four hours studied. Apparent digestibility of blends of sal-GNO and vanaspati-GNOinrats was not effected by the process of interesterification while interesterified products had significantly higher in uiuo tme digestibility compared to starting stocks. I n t r o d u c t i o n Filer et al. ''and Renner and Hill4 showed that digestibility of a fat is determined by the position occupied by saturated fatty acids (palmitic and stearic acids) in glyceride molecules. In natural vegetable oils, saturated fatty acids are mostly located in the 1,3-positions and such a triglyceride is less absorbed than its randomised counterpart having saturated fatty acids predominantly in the 2-position. Digestibility of such fats is thus expected to decrease after randomisation. On the other hand, fats such as lard or human milk fat with saturated fatty acid (palmitic acid) mostly in the 2-position of glyceride molecules is better absorbed than one (such as randomised lard or butterfat) with saturated fatty acid in the 1,3-positions. Again, investigations by A@-Slattr and her coworkers and Bhattucharyya and Chakrabarty indicate that randomisation has no effect on the digestibility of an oil rich in polyunsaturated fatty acids.Thus the effect of interesterification on digestibility requires study with each fat stock before and after above processing.In our earlier communications '-lo, preparation, stability, suitability for use in food preparations and hypolipidaemic effect of a few interesterified fats based on groundnut oil, cottonseed oil, sal (Shorea robusta) fat and sheep tallow have been reported. The present communication reports the effect of interesterification on their (i) in vitro and (ii) in vivo digestibility in rat. M a t e r i a l s a n d M e t h o d s Materialr Refined groundnut oil (GNO), refined and bleached cottonseed oil (CSO), refined and bleached sal (Shorea robusta) fat (sal) extracted from its kernel, vanaspati and edible grade sheep tallow (ST) were used. Vanaspati is a partially hydrogenated edible vegetable oil containing 10 % unhydrogenated edible liquid oils including 5 (Yo sesame oil, plastic in consistency, having a slip point of 31-41' C and conforming to the requirements laid down by the Government of India". Vanaspati-GNO (40 :60, w/w), ST-GNO (30 : 70, w/w), sal-GNO (30 : 70, w/w) and CSO were randomised at 65 f 0.FioC for 30 minutes using dry sodium methoxide as the catalyst. Withvanaspati-GNO and CSO, randomised stocks were cooled to 25OC and held at that temperature for Investigations by Mattson and his coworker