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United States Department of Agriculture

Agricultural Research Service

Research Project: PHYTOCHEMICALS AND AGING: BIOAVAILABILITY, METABOLOMICS, AND BIOACTIVITY

Location: Human Nutrition Research Center on Aging

Title: Bleaching augments lipid peroxidation products in pistachio oil and its cytotoxicity

Authors
item Racicot, Kenneth -
item Craven, Andrew -
item Chen, C-Y Oliver -

Submitted to: European Journal of Lipid Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 29, 2012
Publication Date: December 1, 2012
Citation: Racicot, K., Craven, A., Chen, C. 2012. Bleaching augments lipid peroxidation products in pistachio oil and its cytotoxicity. European Journal of Lipid Science and Technology. 114:1362-1372.

Interpretive Summary: Pistachio consumption is associated with reductions in blood cholesterol and antioxidant defenses because they are rich in unsaturated fats, phytosterols, fiber, and antioxidants. Post-harvest bleaching is typically done to whiten nut shells in order to kill fungi and improve the product’s look. However, the impact of bleaching on nutritional quality and the overall safety of pistachios remains to be examined. In this study, we investigated whether bleaching would increase rancidity of lipids and oxidation of phytosterols in pistachio oil, as well as whether bleached oil would be toxic to modeled liver cells. We found that bleaching indeed increased lipid rancidity, with the largest increase noted with a type of bleach containing hydrogen peroxide and iron. Bleached pistachio oil also contained less phytosterols than untreated pistachio oil. The liver cells treated with bleached oil did not survive as well as those treated with untreated oil. Thus, our results showed that the bleaching treatment had detrimental effects on nutritional quality and expected health benefits of pistachios by increasing lipid rancidity, decreasing phytosterol content, and causing cell toxicity.

Technical Abstract: Pistachio consumption is associated with reductions in serum cholesterol and oxidative stress due to their constituents of unsaturated fats, phytosterols, fiber, and antioxidants. Bleaching has been applied to whiten nut shells for antifungal and cosmetic purposes. However, the impact of bleaching on nutritional quality and safety of pistachios remains to be examined. In this study, we investigated whether bleaching would increase malondialdehyde (MDA) or 7-keto-sitosterol and decrease phytosterols in pistachio oil, as well as cause cytotoxicity of modeled Hepa1c1c7 cells. Bleaching increased MDA by more than 32% from 0.23 µg/g in raw oil, with the largest increase noted with the bleach containing H2O2 and Fe2+ (P is less than or equal to 0.05). Bleached pistachio oil had larger than 12.6% decrease in beta-sitosterol and total phytosterols as compared to the raw oil (P is less than or equal to 0.05). Bleaching with Fe2+ significantly increase 7-keto-sitosterol compared to bleaching alone. Hepatic cell viability was decreased the most by the oil of the pistachios treated with bleach containing Fe2+ (P is less than or equal to 0.05), and lactate dehydrogenase activity in medium was elevated by >18 folds (P is less than or equal to 0.05). Compared to natural pistachios, the bleaching treatment had detrimental effects on nutritional quality and expected health benefits of pistachios by increasing lipid peroxidation, decreasing phytosterol content, and causing cytotoxicity.

Last Modified: 8/19/2014
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