Ochratoxin A in commercial soluble coffee and coffee substitutes

Abstract

Coffee and cereals are recognized sources of ochratoxin A (OTA) in the human diet, but data concerning its amounts in soluble coffee substitutes are scarce. This work aimed to determine the amounts of OTA in commercial soluble coffee substitutes (mixtures of barley, malt, and chicory, either with or without coffee). OTA was isolated by immunoaffinity columns and quantified by HPLC with fluorescence detection.

In a total of 40 samples analyzed, including 10 of soluble coffee, 13 mixtures with coffee and 17 mixtures without coffee, all commercialized in Portugal, 35 samples were positive for OTA, with concentrations ranging from < 0.15 to 11.8 μg/kg. Overall, coffee-containing samples had significantly higher amounts of OTA (p < 0.001) than substitutes without coffee. Indeed, coffee was the main determinant for the OTA content in the substitute beverages analyzed, with a highly significant linear correlation (r = 0.559, p < 0.001) between OTA amounts and coffee percentage in the mixtures. The high variability observed between samples is influenced by the “brand” effect as well as by raw-material quality.

Globally, OTA amounts in coffee substitutes are generally low and within the regulated and safety limits. Their contribution to the provisional tolerable daily intake (PTDI) is therefore reduced (from 1.0 to 2.0% on average). Nevertheless, the high incidence of OTA contamination in these products should not be disregarded.