Determination of locust bean gum and guar gum by polymerase chain reactionand restriction fragment length polymorphism analysis

A polymerase chain reaction (PCR) was developed to differentiate the thicke ning agents locust bean gum (LBG) and the cheaper guar gum in finished food products. Universal primers for amplification of the intergenic spacer reg ion between trnL 3' (UAA) exon and trnF (GAA) gene in the chloroplast (cp) genome and subsequent restriction analysis were applied to differentiate gu ar gum and LEG. The presence of <5% (w/w) guar gum powder added to LEG powd er was detectable. Based on data obtained from sequencing this intergenic s pacer region, a second PCR method for the specific detection of guar gum DN A was also developed. This assay detected guar gum powder in LEG in amounts as low as 1% (w/w), Both methods successfully detected guar gum and/or LEG in ice cream stabilizers and in foodstuffs, such as dairy products, ice cr eam, dry seasoning mixes, a finished roasting sauce, and a fruit jelly prod uct, but not in products with highly degraded DNA, such as tomato ketchup a nd sterilized chocolate cream. Both methods detected guar gum and LEG in ic e cream and fresh cheese at levels <0.1%.