Interlaboratory variability of methods used for detection of economic adulteration in apple juice

Abstract

Thirteen laboratories participated in a study to determine the interlaboratory variability of 4 methods used to detect economic adulteration in apple juice. The methods included the determination of individual sugars, 5-(hydroxymethyl)-2-furaldehyde, chlorogenic acid, organic acids, and L-malic acid. The coefficients of variation found depended on the method and level of analyte, but were often 5% or less. At this point, the most important test for detecting economic adulteration is the total malic/L-malic acid ratio. Any ratio of 0.9 or less would indicate a nonauthentic sample. The 0.9 ratio represents an addition of 20% synthetic malic acid in the unknown juice sample. A 0.75 ratio would indicate 50% adulteration, while a 0.5 ratio would indicate a totally synthetic juice. Furamic acid, a minor contaminant in synthetically produced malic acid, shows great promise as an indicator of economic adulteration. The results support the view that the methods are now ready for AOAC collaborative study.