Hyun Jung Lee and Dojin Ryu from the School of Food Science at the University of Idaho tested 489 samples of corn- rice- wheat- and oat-based breakfast cereal from the US retail marketplace for the mycotoxin Ochratoxin A (OTA) over two years.
“On the basis of the incidence and concentration of OTA, oats and oat-based products may need greater attention in further surveillance programs and development of intervention strategies to reduce health risks to consumers,” they write, noting that OTA levels are regulated in the EU but not in the States.
Using liquid chromatography techniques the scientists found that 205 cereals (42%) were contaminated at levels from 0.10 to 9.30ng/g. OTA levels were mostly below the European Commission Regulation level of 3ng/g, but 16 samples of oat-based cereals came in above this threshold.
Oat-based breakfast cereals (70%, 142/143) were the worst culprits in terms of basic incidence, followed by wheat-based (32%, 38/117), corn-based (15%, 15/103) and rice-based breakfast cereals (15%, 10/66).
Contextualizing their study, the authors describe ochratoxin A (OTA) as one of the most commonly occurring mycotoxins in the world, considered a potent renal carcinogen on the basis of animal studies and classified as a potential human carcinogen by bodies including the International Agency for Research on Cancer (IARC).
Widely detected in cereals and cereal-derived products, the toxin is mainly produced by two fungi – Aspergillus ochraceus and Penicillium verrucosum, which contaminate grains during growing and storage.
Lee and Ryu said that several studies demonstrated that moisture and temperature were two major factors in the occurrence of OTA, although it’s incidence and levels are also related to geography, location, grain type and agronomic practice, harvesting, stocking and transport conditions.
Therefore, OTA has increasingly been regulated worldwide, by the EU for instance, to minimize exposure levels – the bloc’s maximum limits for OTA are 5ng/g in raw cereal grains and 3ng/g in processed cereal products.
A health risk to consumers arises because mycotoxins are relatively heat stable within conventional food processing temperature ranges (80-120C); OTA has a melting point of 169C and is nearly stable when heated to 200C.
“Consequently, OTA may not be completely removed from the food supply and is difficult to destroy under normal industrial food processing or cooking conditions,” Lee and Ryu write.
The scientists said that levels of OTA in breakfast cereal collected from the US market were generally low – of the 489 samples analysed, 126 were taken in 2012-13, 363 in 2013-14 – with the overall average detection limit of 0.03ng/g below EU levels.
Interestingly, average levels of OTA in organic cereals were not statistically different from those found in standard cereals across all the samples, but the key finding in this study was that 16 out of 203 samples of oat-based cereals (8%) exceeded the EU maximum limit for OTA of 3ng/g.
“These results suggest that the prevalence and high levels of OTA contamination mainly in oat-based products must be acknowledged with caution,” Lee and Ryu write.
Urging good agricultural practice and on-farm management to reduce initial fungal infestation and OTA accumulation, the scientists add that best practice in grain storage and other downstream processes is vital, as well as more research to optimise food processing techniques to reduce OTA in cereals.
“This study also suggests a need for greater effort in monitoring OTA in the food supply for additional data and potential concern in public health from the long-term exposure of this potent mycotoxin,” Lee and Ryu write.
Title: ‘Significance of Ochratoxin A in Breakfast Cereals from the United States’
Authors: Lee, H.J., Ryu, D.
Source: Journal of Agricultural and Food Chemistry, DOI: 10.1021/jf505674v
Cereal study urges US focus on oats to cut risk from ‘potent renal carcinogen’