ABSTRACT 

Enwere (1998) reported that the product could also be prepared by peeling, washing, shredding and sun- drying. When prepared for human consumption, the shreds are cooked, washed, possibly soaked for 12- 24 hours and washed again before consumption. It can be consumed alone, with coconuts or sauce made from palm oil, pepper, salt and other ingredients. The dried shreds are snow white, crispy and bland (Mbah and Nnanyelugo, 1989). Apart from sun-drying, "ighu" can also be oven-dried (Okaka, 1997). Moisture sorption studies the relationship between total moisture content and the corresponding water activity over a range of values at a constant temperature. Sorption isotherms exist in the four main food processing areas: drying, mixing, packing and storage (Jowift et al., 1981). The sorption process is fully reversible. The sorption isotherm indicates the water activity at which a food is stable and allows predictions of the effect of changes in moisture content on water activity and hence on storage stability. it is used to determine the rate and extent of drying, the optimum frozen storage temperature and the moisture barrier properties required in packaging materials. Several instruments with different operating principles may be used to measure water activity. They include change in electrical conductivity of immobilized salt solutions, change in electrical capacitance of polymer thin films, longitudinal change in dimensions of water-sorbing fiber, partial water vapour pressure by a manometric system, relative weight of moisture sorbed by an anhydrous hydrophilic solid and dew point by a chilled mirror technique. The rate of change in water activity on a sorption isotherm differs according to whether moisture is removed from a food (desorption) or whether it is added to dry food (absorption).