A plug-based microfluidic system based on the principle of the light-addressable potentiometric sensor (LAPS) is proposed. The LAPS is a semiconductor-based chemical sensor, which has a free addressability of the measurement point on the sensing surface. By combining a microfluidic device and LAPS, ion sensing can be performed anywhere inside the microfluidic channel. In this study, the sample solution to be measured was introduced into the channel in a form of a plug with a volume in the range of microliters. Taking advantage of the light-addressability, the position of the plug could be monitored and pneumatically controlled. With the developed system, the pH value of a plug with a volume down to 400 nL could be measured. As an example of plug-based operation, two plugs were merged in the channel, and the pH change was detected by differential measurement.
The predominant acid-producing organism isolated from Nigerian cassava mixed fermentation cultures was Streptococcus faecium. Corynebacterium manihot was also abundant in the mixed cultures, but contrary to earlier reports, this organism grew slowly and lacked significant acid-producing capabilities. Cultural characteristics of S. faecium indicated that it was the primary fermentation organism in acidic cassava fermentations rather than the earlier indicated C. manihot. Diacetyl production in both milk cultures and fermented cassava was demonstrated for S. faecium. Detection of diacetyl in fermented cassava products indicated that S. faecium may also play an additional role in the flavor development of these products.
One of the problems related to the food supply in Nigeria and other West African countries at present is that of efficient preservation and processing of raw products. In this brief review of potato processing techniques, properties of West African yams are compared with those of potato with a view to explore possibilities of adapting potato processing techniques to yams. Yams referred to in this article are of the family Dioscoreaceae, and they are different from the yams known in the U.S.A. The American yams are of the family Convovulaceae and are a variety of sweet potatoes. Possible new foods from West African yams, similar to convenience foods made from potato are also proposed. Of the varieties of yam grown in Nigeria, Dioscorea alata (water yam) is compositionally closest to potato. Properties of other varieties also are comparable to those of potato. Because there are similarities between the two tuberous crops, various methods for dehydrating potato could be adapted to drying of the West African yam.
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