Changes in composition and thermal transition temperatures of grain sorghum wax during storage

Grain sorghum (Sorghum bicolor) wax is composed mainly of aldehydes, alcohols, and acids. Aldehydes, comprising about one-half of the wax, are readily converted to acids in presence of air. In this study, whole sorghum wax and an aldehyde fraction from sorghum wax were subjected to oxidative conditions. Changes in the major components and thermal transition temperatures were determined using HPLC and differential scanning calorimeter (DSC), respectively. The aldehyde fraction was oxidized markedly to acids over 4 months in storage at room temperature. Acid content, in the fraction, was initially 5-7% and increased to 42-51% after 135 days in storage. Consequently, thermal transition apex and end temperatures of the fraction, which were initially 73-74 and 76-77 degreesC, respectively, increased to 80-81 and 83-85 degreesC, respectively, after 135 days. Whole sorghum wax, composed initially of 55% aldehydes, 37% alcohols, and 7% acids, slightly increased acid level to 8-12% during storage over 5 months under various conditions. Thermal transition temperatures of the wax changed little over all storage conditions during 5 months of storage with 83-84 degreesC for apex temperatures and 86-87 degreesC for end temperatures. (C) 2003 Elsevier B.V. All rights reserved.