Linamarase activity and detoxification of cassava (Manihot esculenta) during fermentation for gari production

La funcion destoxicadora de la linamarasa exogena adicionada se evaluo mediante la fermentacion a temperatura ambiente durante 5 dias de 5 muestras iguales de tejido parenquimatoso de yuca molida. La muestra 1 recibio 192.6 unidades de linamarasa (1 unidad de actividad de linamarasa = cantidad de enzima que produce 1 umol de p-nitrofenolato/min) solamente el primer dia. Las muestras 2, 3 y 4 recibieron el mismo nivel de enzima en los primeros 2, 3 y 4 dias, resp. La muestra 5 no recibio linamarasa y sirvio como testigo. Las muestras despues se exprimieron y tostaron para producir gari (9 por ciento de humedad). La actividad de la linamarasa y el contenido total de HCN disminuyeron constantemente hasta el dia 3 de la fermentacion y luego se nivelaron, lo cual ocurrio simultaneamente con la disminucion del pH desde 6.0 (optimo para la linamarasa) hasta 4.0 y lo cual demuestra que la destoxicacion esta asociada con la enzima en vez de la hidrolisis acida. Esto ultimo tambien lo evidencia el hecho de que la linamarasa exogena destoxico la yuca fermentada en un 87.5 por ciento en comparacion con un 50 por ciento de destoxicacion sin la adicion de la enzima. La linamarasa exogena adicionada destoxico mas rapidamente la yuca en las primeras 24 h que despues de 5 dias de fermentacion sin la adicion de la enzima; ademas, se logro poca destoxicacion al adicionar mas enzima a la masa despues de las primeras 24 h, debido al pH favorable para la enzima. Se estan adelantando trabajos sobre el uso de la linamarasa para reducir el periodo de fermentacion de la yuca para producir gari. (CIAT)

The detoxifying role of exogenously added linamarase was evaluated by fermenting 5 equal samples of grated parenchymatous tissue of cassava roots at room temp. for 5 days. The 1st sample received 192.6 units of linamarase (1 unit of linamarase activity = the amount of enzyme which produced 1 Micro mol of p- nitrophenolate/min) on the 1st day only. The 2nd, 3rd, and 4th samples received the same level of enzyme activity on each of the 1st 2, 3, and 4 days, resp. The 5th sample received no linamarase and was used as control. Samples were then pressed and roasted to yield gari (9 percent moisture). Linamarase activity and total HCN content decreased steadily until day 3 of fermentation and thereafter levelled off, thos occurring simultaneously with a decrease in pH from 6.0 (optimum of linamarase) to 4.0. This shows that detoxification is associated with the enzyme rather than acid hydrolisis. The fact that fermented cassava was detoxified by 87.5 percent with exogenous linamarase additions compared with 50 percent detoxification without enzyme addition is a further indicative. The addition of exogenous linamarase detoxified cassavamore rapidly after 24 h of fermentation than after 5 days of fermentation without enzyme addition. Very little detoxification was achieved by adding more enzyme to the mash beyond the 1st 24 h due to the favorable pH. Research on the use of linamarase to shorten the fermentation period of cassava during gari production is in progress. (CIAT)