Oxidation, flavor, and texture of walnuts reduced in fat content by supercritical carbon dioxide

English walnuts are popular because of their good taste, high n-3 FA content, and reported hypocholesterolemic effects. However, walnuts have a high fat content (similar to70% w/w) that is highly polyunsaturated, which contributes to oxidative instability. The objectives of this study were: (i) to use supercritical carbon dioxide (SC-CO2) extraction to decrease the total fat content of walnuts, and (ii) to determine the effects of SC-CO2 lipid extraction on the oxidative stability, flavor, and textural characteristics of the reduced-fat walnuts. The fat content of English walnut pieces was reduced by 25 and 40% with a pilot-scale SC-CO2 extraction system. Full-fat, 25-, and 40%-reduced-fat walnuts were stored at 25 and 40degreesC for 8 wk. FA profiles were similar for residual oil in all treatments, and the profiles did not change with storage. PV and volatile compounds were significantly greater (P < 0.05) in full-fat walnuts than in reduced-fat walnuts at both storage temperatures. A trained sensory panel judged the reduced-fat walnuts to be less astringent and to have less walnut and rancid flavors. Full-fat walnuts had greater hardness than reduced-fat walnuts by both sensory and instrumental texture profile analyses. In general, reducing the relative fat contents of walnuts by 25% improved oxidative stability and maintained a high level of consumer acceptance.