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Accelerate solvent extraction of lipids.

Lipid oxidation is a problem because it produces compounds that degrade product quality, alter textural properties and adversely affect the color and nutrition of products. Unsaturated fatty acids decompose into volatile compounds with low molecular weights that produce off-aromas associated with rancidity.

Ultimately, lipid oxidation reduces shelf life and causes spoilage. Susceptibility of fatty acids to lipid oxidation increases with the degree of unsaturation. But if manufacturers abide by the latest dietary guidelines and reduce solid fats by simply substituting healthier polyunsaturated fatty acids, they risk severely decreasing food acceptability and shelf life.

Scientists at Rutgers University investigated the ability of accelerated solvent extraction (ASE) to extract lipids more rapidly and completely with minimal oxidation in extruded pet foods, both mixed meat and grain base. Their results demonstrate that ASE is a highly efficient method for extracting lipids from difficult matrices while inducing minimal oxidative and hydrolytic modifications.

First, Kibbles 'n Bits[R] were ground to less than 500 microns, packed into ASE cells, and extracted under 1,500 psi of nitrogen pressure. Temperature, the type of lipid solvent (chloroform, hexane, iso-octane, petroleum ether and methanol), extraction static time and numbers of extraction cycles were varied to determine the conditions for optimum lipid yields and minimal degradation. Extracts were dried under vacuum. Then the lipid composition was analyzed using thin-layer chromatography. Conjugated dienes and hydroperoxides were measured to determine the extent of oxidation.

ASE at 40 C provided comparable or higher yields than manual extraction in shorter extraction times--10 to 40 minutes, depending on the matrix. The presence of methanol increased the extraction of non-lipid materials. With ASE, normally immiscible hexane and methanol injected into extraction cells separately were able to nearly duplicate extractions of chloroform and methanol, providing an option for replacing chlorinated hydrocarbon solvents.

Oxidation levels increased with the number of extraction cycles and with the ASE temperature above 40 C, but under all conditions remained notably lower than with manual extraction. Cumene hydroperoxide and corn oil controls extracted alone confirmed that hydroperoxides were not degraded and were produced in only trace amounts by ASE at 40 C. Oxidation occurred the least in chloroform, probably due to higher argon solubility and the presence of radical stabilizers.

Further information. Karen Schaich, Food Science Department, 65 Dudley Rd., Cook College, Rutgers University, New Brunswick, NJ 08901; phone: 848-932-5454; email: schaich@aesop.rutgers.edu.

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Publication:Emerging Food R&D Report
Date:Mar 1, 2016
Words:393
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