Structured lipids replace oil in functional beverages.

One ideal application for structured lipids (SLs) involves their use as a replacement for oil in nutritional beverages. Such SLs would contain medium- and long-chain fatty acids on the same glycerol backbone that could be harnessed as a delivery mechanism for essential fatty acids and as a way to improve absorption.

But sensory analysis is needed to determine if the SL changes the sensory profile of the nutritional beverage when it is used in place of canola oil. Additionally, the oxidation properties of SL-based oil-in-water emulsions need to be examined before incorporating SLs into commercial beverage formulations.

Researchers from the University of Georgia synthesized the SL from canola oil and caprylic acid in a bioreactor packed with a sn-1,3 specific lipase that was sourced from Rhizomucor miehei. Differences between beverages formulated with SL and canola oil were determined using a triangle test and quantitative descriptive analysis (QDA).

The scientists then formulated 10% oil-in-water emulsions with SL, a-tocopherol, [beta]-carotene, genistein and daidzein. They were stabilized with 0.5% whey protein isolate (WPI) or sucrose fatty acid ester (SFE). The peroxide values, anisidine values and TOTOX values of emulsions stored at 50 C were measured during a 30-day period.

Substituting the SL for unmodified canola oil significantly enhanced the perception of sweet flavor and decreased bubble formation. Significantly (p < 0.05) less total oxidation occurred in the WPI emulsions compared to their SFE counterparts. [beta]-carotene did not affect the oxidation of WPI emulsions, while a-tocopherol, genistein and daidzein significantly (p < 0.05) increased secondary oxidation. All four natural compounds exhibited pro-oxidant activity in the SFE emulsions.

These results indicate that a canola oil-caprylic acid SL may be suitable for use in nutritional beverages. WPI provides both emulsification and antioxidant properties to SL-based emulsions. Because a-tocopherol, [beta]-carotene, genistein and daidzein may exhibit pro-oxidant activity in some emulsions, manufacturers must test a variety of formulations before adding them to SL-based beverages as antioxidants or functional ingredients.

Generally, SLs make it possible to include virtually any fatty acid profile in formulations. Nutritional supplements, ready-to-drink beverages and beverage dry mixes can offer added health benefits with the inclusion of SLs containing specific fatty acid profiles.

Further information. Casimir Akoh, Department of Food Science and Technology, University of Georgia, Food Science Building, Athens, GA 30602; phone: [phone]; fax: [phone]; email: [e-mail].