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United States Department of Agriculture

Agricultural Research Service

Research Project: Improvement & Maintenance of Flavor & Shelf-Life, Functional Characteristics & Biochem/Bioactive Process, & Use of Genetic/Genomic Resource

Location: Market Quality and Handling Research

Title: Removal of Heavy Metal Contamination from Peanut Skin Extracts by Waste Biomass Adsorbents

Authors
item Massie, Brianna -
item Dean, Lisa
item Davis, Jack
item Sanders, Timothy

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: April 8, 2014
Publication Date: N/A

Interpretive Summary: Peanut skins are a waste product of the peanut blanching industry. Large quantities are produced which have little or no commercial market. This material is rich in polyphenols which could be of value once isolated for nutraceutical applications. Extraction and concentration of this material can sometimes result in an end product containing heavy metals such as cadmium and arsenic above acceptable levels. This research examined the effectiveness of other waste biomass materials such as chitosan and peanut shells or hulls to remove the metals from the extraction solutions. It was found that the peanut shells were more effective than chitosan but that cadmium was removed in greater amounts than arsenic. This was attributed to the multivalent nature of arsenic indicating more than one mechanism of absorption is necessary.

Technical Abstract: Each year, 3.6 million pounds of peanuts are harvested in the United States. Consequent processing, however, generates large amounts of waste biomass as only the seed portion of the fruit is consumed. The under-utilization of waste biomass is a lost economic opportunity to the industry. In particular, discarded peanut skins are a rich source of phenolic antioxidant compounds which could be extracted to produce value-added products. However, certain obstacles prevent the utilization of peanut skins such as its high heavy metal content. This study attempted to develop an economically feasible method for the remediation of peanut skin extract using adsorption technology. Milled peanut skins from a commercial blanching operation were extracted with aqueous ethanol (70%). After filtration, the supernatant was tested with and without removal of the ethanol. Each matrix was spiked to a 10ppm concentration of arsenic and cadmium. Two agricultural waste products were chosen as adsorbent materials; peanut hulls and chitosan cross-linked beads. Batch adsorption experiments were used to determine the effect of adsorbent dosage by varying the amount of chitosan beads from 0.050 to 1.50g and the amount of peanut hull from 0.050 to 1.00 g. Isothermal data was evaluated using the Langmuir adsorption model to determine the best adsorbent material. The most efficient material was then evaluated under a range of pH values to optimize performance and determine adsorption kinetics. The Langmuir adsorption model determined peanut hulls were the more effective material. The optimized pH was found to be between pH 3-4. Peanut hulls removed 88.6 ± 1.9 % of added Cd within 20 min of contact. Apparent removal of arsenic (21.7 ± 9.5%) showed no correlation to adsorbent dosage. Adsorption isotherms could not be completely explained using the Langmuir model indicating sorption resulted from more than one mechanism. Successful removal of Cd without reduction of the phenolic content of the extracts shows this strategy is feasible for heavy metal remediation of peanut skin extracts making them a viable source of antioxidants in food applications.

Last Modified: 10/24/2014
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