Occurrence of ochratoxin A and ochratoxin B in commercial coffee in Vietnam and Thailand

Abstract

Occurrence of ochratoxin A (OTA) and ochratoxin B (OTB) in 32 Vietnamese roasted coffees, 30 Thai roasted coffees and 38 Thai instant coffees was performed using an immunoaffinity column-HPLC method. Twenty-six of Vietnamese roasted coffees were contaminated with overall average 0.75 μg/kg of OTA and 11 samples were contaminated with overall average 0.20 μg/kg of OTB. Four of Thai roasted coffees were contaminated with overall average 0.17 μg/kg of OTA and one sample was contaminated with 0.56 μg/ kg of OTB. Twenty-eight of Thai instant coffees were contaminated with overall average 2.19 μg/kg of OTA, and OTB from these samples was not detected. There was no sample more than OTA regulatory limits of European Union. Therefore, it seems that the risk of ochratoxins in retail coffees in Vietnam and Thailand was acceptably low. This report is the first on occurrence of OTB in Vietnamese roasted coffee and ochratoxins in Thai instant coffee. Ochratoxins, which have nephrotoxic, teratogenic, genotoxic and neurotoxic effects on animals and humans1), are produced principally by several species of Aspergillus and Penicillium verrucosum2). Ochratoxins occur in various cereals and beans and their related products, wine, meats and meat products3). Ochratoxin A (OTA), which is classified as a possible human carcinogen (Group 2B) by the International Agency for Research on Cancer2), is the most potent ochratoxin. Ochratoxin B (OTB), which is the non-chlorinated analog of OTA, was lower toxic than OTA4). The lower levels of OTB than OTA has been found in cereals, cacao and coffee products in Japan5),6). However, red wines in Italy and Spain were contaminated with OTB which was almost the same levels of OTA7),8). Because 22 (28.6%) of the 77 red wines in these reports were contaminated with higher concentration of OTB than OTA, we considered that it was preferable to analyze both OTA and OTB in coffee products. Coffee has been found to be contaminated with OTA at a relatively high frequency9). In the European Union, the OTA regulatory limit is 5 μg/kg for roasted coffee and 10 μg/kg for instant coffee10), but a regulatory limit for OTA in food has not been established in Thailand and Vietnam11). Vietnam is the world’s second largest coffee producer, mainly of Robusta coffee. Its Robusta coffee is exported around the world and commonly consumed as a regular coffee in Vietnam12). Thailand is Southeast Asia’s third largest coffee exporter12). In Thailand, Arabica beans are cultivated in the mountains at high altitude in the north, whereas Robusta beans are cultivated in the south13). There are some reports on contamination of OTA and infection of OTA-producing fungi in green coffee in Vietnam14),15) and Thailand13). Only two reports on OTA in Vietnamese roasted coffee and Thai roasted coffee have been published16),17), but there are no reports in international journals on ochratoxins in Thai instant coffee. The aim of this study was to survey OTA and OTB in commercial coffee from Vietnam and Thailand using an in-house immunoaffinity-column (IAC) HPLC method6). Thirty-two roasted coffees (Robusta) were purchased from conventional supermarkets and stores in Ho Chi Minh City and Can Tho City in Vietnam during 2011 and 2012. Thirty roasted coffees (Arabica) were purchased in Chiang Mai City and 38 instant coffees (mainly Robusta) were purchased in Chiang Mai and Bangkok in Thailand during 2012 and 2013. All samples were kept at 4 ̊C until analysis. Acetonitrile and methanol (HPLC-grade), and other chemicals (reagent grade) were purchased from Wako Pure Chemicals (Osaka, Japan). Water was purified using a Milli-Q ultra-purification system (Millipore, Bedford, MA, USA). Standard solutions of OTA and OTB (10 μg/mL in acetonitrile)