Effect of cowpea seed drying temperature and wet milling on the rheological properties of Moin-Moin paste and gel

Abstract

The effects of cowpea seed drying temperature and wet-milling on the viscosity of moin-moin paste and texture (rheology) of moin-moin gel were studied. The large brown eye Kano white cowpea seeds were soaked in water at 250C for 5 min, drained and dried at temperatures between 30 and 120oC, decorticated and dry milled into flour. Decorticated cowpea seeds dried at 30oC were soaked in cold water at 250C for 1.5hr and wet milled into paste. The cowpea flours and paste were reconstituted with water and prepared into moin-moin with and without addition of salt, pepper, tomato paste, onions, vegetable oil and beef flavour. Determination of the moin-moin paste viscosity prior to steaming showed that all the pastes exhibited pseudoplastic flow behaviour. The moin-moin from the wet milled paste had higher viscosity than the samples from flours due to higher swelling of the starch, protein and cell wall materials. The moin-moin pastes containing additional ingredients had higher viscosity than the plain samples due to the additional solid matter. Drying at temperatures between 80 and 120oC increased the viscosity of the plain moin-moin paste but decreased those of samples with added ingredients. Texture studies showed that drying temperature, wet milling and addition of ingredients decreased the hardness of the moin-moin gel at 50% double compression and relaxation.
Key words: Cowpea, moin-moin, viscosity, and texture