NCU researchers achieve lowest toxin level in processed cassava

Northern Caribbean University (NCU) researchers have found a technique to lower the toxin levels in cassava, from which bammy, a favourite food of Jamaicans, is produced.

Professor of Environmental Geoscience Mark Harris and graduate student Charles Koomson achieved world-record-high levels of cyanide extraction from bitter cassava using a moisture-pressure combination technique.

This involved soaking cassava in water for two hours, adding heat at 50 degrees Celsius, then applying pressure to the moistened tuber for 12 hours or overnight.

The process reduced the cyanide level in toxic bitter cassava to 13 per cent, which represents 38 parts per million (ppm) of the toxin in tubers - the lowest level achieved worldwide to date. These results compare favourably with the 2010 research findings of Howard Bradley and company of Australian National University, who reduced cyanide levels in cassava to 16 per cent, or 45 ppm.

In underscoring the significance of the NCU research findings, lead researcher Professor Harris pointed out that 38ppm of toxicity in cassava is relatively close to the 10ppm level recommended as safe for human consumption by the Food and Agriculture Organization and the World Health Organization. But he noted that the NCU results were far from the 100ppm level considered a health risk by Australian state authorities.

The body of research by Harris and Koomson was conducted from 2009 to 2016. The findings are just now being released locally, but they were published previously as an article titled, 'Moisture-pressure combination treatments ... ' in the Journal of Food Science (2011) and the Journal of Agricultural Science (2016).

In addition, the research findings appear in Harris' 2016 book titled Geobiotechnological Solutions to Anthropogenic Disturbances: A Caribbean Perspective, published by Switzerland-based Springer International Publishing.

 

High cyanide levels in bammy

 

In 2009, Harris also produced research findings that pointed to high cyanide levels in samples of bammy. Commenting on his cumulative research on the subject, the NCU faculty member pointed out that the consumption of protein containing amino acids can offset the negative effects of moderate dosages of cyanide of cassava.

In this regard, he gave a thumbs up to the favourite Jamaican dish of bammy and fish.

"This is a perfect match from a biochemical perspective because fish, being protein, can offset any ill effects from a moderate dosage of cyanide in cassava," Harris explained, advising that persons should avoid consuming cassava or its by-products in quick succession so as to prevent harmful cumulative effects.

According to Harris and Koomson, location greatly influences the impact of cyanide, and occupational exposure remains a major problem associated with all phases of bitter cassava processing.

This is often a semi-mechanised process with the use of graters, pressers of varying forms, and sieves. In all stages, the deadly hydrogen cyanide gas is released into

the environment and joins atmospheric air or makes it way to the soil and water bodies. The extent of this occurrence depends on soil topography and geology of the area, the researchers pointed out.

Harris and Koomson noted that "the diurnal/nocturnal winds in southern Jamaica (the cassava-processing areas) are weak compared with the dominant trade winds in the northern section, including north of the Blue Mountains." They added: "Such relatively calm conditions prevailing in southern Jamaica may not sufficiently dilute and disperse toxic atmospheric gases from large piles of factory waste. Moreover, south of the Blue Mountains, subsiding, sinking air compresses itself, further suppressing the vertical and lateral dispersion of atmospheric pollutants."

 

Recommendations

 

- For rapid atmospheric dilution, dispersion, and environmental health, cassava-processing factories are best located within zones of continual air movements. Thus, for Jamaica, north coast and higher-altitude locations are better than those in the south.

- Toxic materials in bitter cassava waste water can endanger humans, as well as other organisms, if they are not properly treated before disposal.

- In order to address these problems, the most efficient method of cyanide removal from cassava, particularly of the peels, which are rich in starch and toxin, is the moisture-pressure treatment pioneered by the NCU research team, thereby minimising groundwater contamination.

- Relevant government agencies should advise on the location of future cassava-processing factories to reduce potentially adverse environmental effects.