Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 13, 2005
Publication Date: January 15, 2006
Repository URL: http://www.ars.usda.gov/sp2UserFiles/Place/66210000/Reprint957.pdf
Citation: Baldwin, E.A., Wood, B.W. 2006. Use of edible coating to preserve pecans at room temperature. HortScience. 41(1):188-192. Interpretive Summary: Shelled pecans are high in quantities of unsaturated fatty acids, which while healthy, also undergo degradation resulting in rancid off-flavor. For this reason these nuts must be stored at low or freezing temperatures which is costly. In this research edible coatings were developed to protect the nuts and prevent rancidity. These coatings extended the shelf life of pecans at room temperature by several months.
Technical Abstract: Oxidation of the unsaturated fatty acids in pecans (Carya illinoinensis) results in the development of rancid off-flavors, which shortens shelf life under ambient storage conditions. For this reason pecans must be stored using costly refrigeration. Edible coatings (hydroxypropyl cellulose (HPC) and carboxy methylcellulose (CMC) with various additives) were used to restrict oxygen contact with the nut fats by acting as a barrier to gas exchange. Pecans were acquired from experimental groves in Byron, Ga, coated with various coating formulations, drained, dried, and stored in open air or in zip-lock plastic bags with four 1-mm holes at 20-25C. The nuts were periodically sampled by sensory panels, consisting of 18-20 panelists, who scored the samples using a 9-point hedonic scale for appearance, shine, off- or overall flavor, and texture. Coated nuts generally scored lower and higher ratings for off- and overall flavor, respectively. Initial coatings resulted in less preferred appearance, but later coatings improved or had no effect on appearance. Coatings with CMC imparted shine to the coated nuts, and generally coatings did not affect texture. Development of rancidity involves hydrolysis of glycerides into free fatty acids, oxidation of double bonds of unsaturated fatty acids to form peroxides and ultimately autooxidation of the free fatty acids. One of the products of autooxidation is hexanal, which is therefore, a good indicator of rancidity. Analysis of pecan homogenate after 5 and 9 months of storage by gas chromatography revealed that hexanal levels were reduced in nuts coated with CMC, and CMC coatings with added a-tocopherol were most effective.