Choice of Natural Or Modified Fats For Solid Fat Formultions: The Current Health Dilemma
by Kalyana Sundram & Yusof Basiron

Malaysian Palm Oil Council (MPOC), 2nd Floor Wisma Sawit, Lot 6, SS6 Jalan Perbandaran, 47301 Kelana Jaya, Selangor, Malaysia
E-mail: kalyana@mpoc.org.my, yusof@mpoc.org.my

Modified Fats: Interesterified Fats

Interesterification is currently viewed as an alternate process to partial hydrogenation of edible oils and fats. The process involves the randomisation among all three stereospecific positions of fatty acids in native edible oils and fats by either enzymatic or chemical catalysis at low temperatures. The positional distribution of fatty acids on the glycerol backbone are altered either through fatty acids switching positions within a TAG molecule or between TAGs. If interesterification involves TAG species within the same dietary fat, the fatty acid composition remains the same. A solid fat is often interesterified with a liquid oil and in this case fatty acid composition of the interesterified product will differ. Randomised fats have diverse applications both in the food industry and in clinical applications [12,13]. Interesterified fats and oils developed for the food industry have different melting and crystallisation properties from that of native fats and oils which confer desired rheological properties to bakery and confectionary products [14].
The metabolic effects of randomisation of fats has not been extensively studied as the development and use of structured fats is only recent and in the nascent stage. Three recent reviews in this area indicate that literature is confined to mostly animal studies with piglets and rats as models [12-14].  Human studies are few and apart. In contrast increasing citations on the use of structured lipids in the catabolically stressed state is now apparent. Of prime interest is whether structural differences arising from the positional distribution of fatty acids, between randomised and native fats, alters their nutritional behaviour as regards lipid metabolism and gene expression. Given the interest in studying structural influences on digestion, absorption and transport of TAG, methodological preferences favour the postprandial model in current literature.

The effects of chemically modified vegetable oils, either from partial hydrogenation or interesterification were compared with a natural oil rich in saturated-monounsaturated fatty acids in a recent human clinical trial (unpublished data, Sundram et al. 2005) All three fats were matched to reflect similar plasticity.  The primary focus was on blood lipids and the lipoprotein profile in normocholesterolaemic humans, with a secondary focus on blood glucose and insulin using a postprandial approach.    Palm olein (POL) was chosen as the natural fat, as it is widely consumed and used extensively for many solid fat formulations. Partially hydrogenated soybean oil (PHSO) and chemically randomised fat (IE) were included as typical examples of modified fats commonly used in solid fat formulations.