Development of an analytical method for determination of carbohydrates in food by gc - fid using chemical derivatization with anhydride acetic acid

Abstract

The present research describes a simple and inexpensive derivatization method that uses acetylation to address the challenges associated with the quantification of the ten most common carbohydrates. The derivatization reaction has two periods : (1) The oxime formation of carbohydrates was carried out at 15 minutes, 500 µL of NH2OH 2.5%  and  60 ºC and (2) acetylation of carbohydrates was carried out at 45 minutes, 600 µL of AAA  and  80ºC. Most of the carbohydrates generate single peaks via chromatographic separation, except fructose, which generates a double peak. The procedure was successfully applied to analyze carbohydrates in some samples including honey, fresh milk, and polysaccharide hydrolyzate. The method validation results had the linear concentration range of carbohydrates at 50-4000 mg/g, the LODs at 20-50 µg/g, the relative standard deviations (% RSDs) of peak area under 5.0 % and the accuracy at 95–115% of recoveries. The method was applied to determine carbohydrate content in raw milk, honey, and hydrolysis polysaccharide extract. The results showed that the honey sample has fructose and glucose content of 65.8% and 33.4%, respectively, while sucrose makes up 0.74% of the total carbohydrate content. The raw milk sample has lactose content of 47.6% of the total carbohydrates. Some rare polysaccharides such as arabinose and xylose were found in the hydrolysis polysaccharide extract from the mushroom sample.