Effect of Cis-Trans Isomers and Related Physical Properties of Monounsaturated Lipids on Shortening Power

The effect of cis-trans isomers on the shortening power of lipids was investigated. Lipid samples studied included: a commercial vegetable oil (control), oleic acid, elaidinized triolein, two samples in which elaidinized oleic acid was substituted at different levels for oleic acid, and two samples in which elaidinized triolein was substituted at different levels for triolein. Breaking strengths of plain pastry wafers were used for estimating the shortening power. Melting point, surface tension, interfacial tension and viscosity measurements were made on the lipid samples. Lipid composition analyses included gas-liquid and thin-layer chromatography.

Except at the 100 percent level of substitution, wafers containing fatty acids had lower breaking strengths than those containing triglycerides. Breaking strengths of wafers containing samples substituted at the 100 percent level of elaidinized material were greater than those of wafers containing samples substituted at lower levels. Melting points of the lipids were positively correlated with breaking strength and with percent trans isomers. Surface tension and viscosity of fatty acid samples were lower than those of triglyceride samples. Values for interfacial tension did not differ consistently. The moisture levels of the doughs made from fatty acids were higher than those made from triglycerides. Doughs containing elaidinized lipids at the 100 percent level of substitution were higher in moisture content than the other doughs. Relationships among various measurements are discussed. A multiple regression equation is presented for predicting breaking strength values.