Detection of Mold in Processed Foods by High Performance Liquid Chromatography1

Abstract

A high-performance liquid chromatographic (HPLC) method was developed to analyze for the degree of mold contamination in processed fruit and vegetable products. The method is based on detection of glucosamine, a breakdown product of chitin which is one of the major constituents of fungal cell walls Food samples were hydrolyzed at 121°C for 2 h to release glucosamine from fungal chitin. The hydrolysates were partially purified by passing them through a Dowex-50 cation exchanger. Effluents were derivatized by o-phthalaldehyde and the fluorogenic reaction products were separated by reversed-phase HPLC and detected by a spectroflurometer. Six species of mold, Alternaria alternata, Alternaria solani, Colletotrichum coccodes, Fusarium oxysporum, Geotrichum candidum and Rhizopus stolonifer, which are commonly associated with fruit and vegetable products, were used in this study and different levels (0.1 to 2.5 mg/g of sample) of mold mycelium were added to rot-free tomato products. A linear relationship between concentration and glucosamine was observed. However, different species of mold gave different amounts of glucosamine. The effect of insect contamination on the assay was negligible unless high levels were present. Results obtained by the HPLC method were compared with those obtained with an amino acid analyzer and reasonable correlation between the two methods was evident.