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Extrusion of Maize–Cowpea Blends in a Modified Oil Expeller
Author(s) -
SefaDedeh S,
Saalia F K
Publication year - 1997
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(199702)73:2<160::aid-jsfa683>3.0.co;2-u
Subject(s) - die swell , extrusion , moisture , water content , absorption of water , volume (thermodynamics) , plastics extrusion , bulk density , expansion ratio , materials science , food science , composite material , chemistry , environmental science , soil science , physics , geotechnical engineering , quantum mechanics , engineering , soil water
A laboratory oil expeller was modified by using a press cylinder without openings for expelling the oil. Central composite rotatable design for k =3 was used to study the effects of process variables, cowpea level (0–25%), feed moisture (10–25%) and barrel temperature (130–200°C) on product indices (moisture, expansion index, bulk density, water absorption, extractable solids, swell volume and the degree of gelatinisation of flour from the extrudate). Regression models developed to predict product indices were significant and showed no significant lack of fit. The model for moisture content of the extrudate had an R 2 of 0·98. Product moisture was influenced by the amount of cowpea in the feed, the temperature of extrusion and feed moisture. Furthermore, the product moisture measured at each cowpea level was dependent on the temperature of extrusion. The model for product expansion index showed that this index decreased with feed moisture and the cowpea level. Regression models for bulk density, water absorption, extractable solids and the maximum swell volume of flour from the extrudate were influenced by the process variables. The degree of gelatinisation decreased with cowpea level and increased with extrusion temperature. © 1997 SCI.