Synthesis and estimation of calorific value of a structured lipid-potential reduced calorie fat.
The majority of reduced calorie fats and fat substitutes available today, though similar in texture and flavor to natural fats, contain fatty acids that are not usually present in edible oils and fats and thus do not fully match the chemistry and functions of natural fats. For example, such products do not provide nutritionally important essential fatty acids (EFA). In this investigation, we prepared and evaluated a reduced calorie fat, prepared entirely from natural fats, taking advantage of the fact that long-chain saturated fatty acids (LCSFA), such as behenic acid (22:0), are poorly absorbed. Mustard oil (MO) and sunflower oil (SO) were used as substrates to yield a structured lipid (SL). The product, being derived from a natural vegetable oil, would thus provide EFA, as would a native fat, a feature not provided by the low-calorie fats available in the market. Erucic acid (22:1) was isolated from MO by a lipase (EC 3.1.1.3)-catalyzed reaction. It was then hydrogenated to behenic acid, the ethyl ester of which was subsequently enzymatically transesterified with SO to yield a plastic fat containing about 30-35% behenic acid. Absorption of this fat was studied in Wistar rats. In a preliminary single oral dose experiment, rats were fed equal amounts (2 mL) of SO and the SL. Plasma triacylglycerol (TAG) levels were estimated after 1, 2, and 3 h of feeding. The significantly lower concentration of plasma TAG in the 2-h sample, observed in the SL-fed group compared to the SO-fed group (P<0.001), indicated poor absorption of the SL. In order to estimate the calorific value of the SL, we conducted a restricted diet growth experiment over 21 d on weanling Wistar male rats with SO as caloric control. Diets for the test groups were modified by adding 5, 10, and 15% SO for the control groups, and 5 and 10% SL for the experimental groups. Food consumption of the test groups was restricted to 50% of the feed containing 5% SO that had been consumed by the ad libitum group the previous day. Body weights were recorded during the experiment. Calorific value of the SL was estimated by comparing the 21 st-d mean body weight gain of the control group with that of the experimental group. Estimated calorific value of the SL was 5.36 kcal/g. Most of the behenic acid fed was excreted, as indicated by the analysis of the fatty acids of plasma and fecal total lipid. A second growth experiment on ad libitum diet was conducted over 21 d on weanling Wistar male rats to compare the absorption behavior of the SL with that of natural oil. SO (10%) was added to the diet of the control group, and SL (10%) was added to the diet of the experimental group. Feed consumption, as well as body weights, was recorded during the experiment. The growth pattern of the experimental group was identical to that of the control group during the period of study. The mean feed intake (9.8 g/d/rat for the control group vs. 9.9 g/d/rat for the experimental group) indicated good palatability of the product. In conclusion, the enzymatically synthesized SL containing EFA and natural antioxidants has nutritional properties almost identical to those of natural fats, and can be used as a reduced calorie fat.