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

Abstract

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 (~70% w/w) that is highly polyunsaturated, which contributes to oxidative instability. The objectives of this study were: (i) to use supercritical carbon dioxide (SC-CO 2 ) extraction to decrease the total fat content of walnuts, and (ii) to determine the effects of SC-CO 2 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-CO 2 extraction system. Full-fat, 25-, and 40%-reduced-fat walnuts were stored at 25 and 40°C 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. Fullfat 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.

Effect of packaging and storage conditions on quality of shelled walnuts

“…Several studies have focused on the influence of storage conditions on pistachio, almond, peanut, and walnut at high temperatures such as 30, 36, and 40°C. Results showed nuts to be dramatically more rancid as compared to those stored at 8, 10, 20 or 25°C for the same period of time (Braddock, Sims, & O'Keefe, 1995;Crowe & White, 2003;Garcia-Pascual et al, 2003;Maskan & Karatas, 1999;Nepote, Mestrallet, Accietto, Galizzi, & Grosso, 2006).…”

Oxidative stability of walnut oils extracted with supercritical carbon dioxide

“…In other work conducted in our laboratory, supercritical carbon dioxide (SC-CO 2 ) was used to decrease the total fat content of walnuts by 25 and 40% (1). Walnut oil is prized as a specialty oil because of its characteristic flavor and aroma and its potential health benefits (2,3).…”

Comparison of starch films and effect of different rice starch‐based coating formulations on physical properties of walnut during storage time at accelerated temperature

“…A 3.6 cm probe was used at 50% compression with a compression rate of 0.5 mm/s. The eleven measurements of each sample type were made (Crowe & White, ). From the resulting force time curves, fracturability (g unit) (first peak of first compression that indicated toughness), and hardness (g unit) (maximum peak of first compression that indicates the maximum force) were determined (Kahyaoglu & Kaya, ; Meullent & Gross, ).…”

“…A 3.6 cm probe was used at 50% compression with a compression rate of 0.5 mm/s. The eleven measurements of each sample type were made (Crowe & White, 2003).…”