Hydration kinetics of direct expanded tef flour breakfast cereals in water and milk
Hydration kinetics of tef flour breakfast cereals extruded at barrel temperatures of 110, 130, and 150°C was investigated by hydrating them in water and whole milk at 25°C (±1°C). The normalized Weibull model described the rehydration characteristics of the extrudates in water and milk adequately (R2 = 0.98–0.99). Water absorption rate was significantly (P < 0.05) influenced by barrel temperature where extrudates processed at 150°C barrel temperature exhibited high water absorption rate followed by those extruded at 130 and 100°C, respectively. Hydration rate and equilibrium moisture content were higher for samples hydrated in water than those in milk. In view of the values of the shape parameter β, the hydration process is predominantly controlled by diffusion (β = 0.40–0.51) for samples extruded at 110°C whereas external resistance to mass transfer dominated (β = 0.60–0.73) those extruded using 150 and 130°C. Extrudates processed at 130 and 150°C exhibited better hydration characteristics. Thus, these temperature ranges could be used to produce extruded products from tef.
Effect of milk fat and total solids concentration on the kinetics of moisture uptake by ready‐to‐eat breakfast cereal
Summary When immersed in milk, breakfast cereal easily take up moisture, lose their brittle texture and become soggy. Earlier comparative analysis of the moisture sorption by breakfast cereal immersed in water and milk indicated that milk solids might play an important role on the sorption kinetics. In this work, the moisture uptake by ready-to-eat corn breakfast cereal immersed in milk solutions, reconstituted from whole and skimmed milk powder, was measured under isothermal conditions at 5, 30 and 55 °C. Dilutions between 0.25 and 1.5 were tested, with the factor of dilution 1 corresponding to the standard recommended by the milk powder manufacturer. The Weibull probabilistic model adequately fitted the experimental data by appropriate choice of its variable parameters. The dependence of the model parameters on temperature and total solids concentration was assessed for both skimmed and whole milk. Fat was found to play a major role on the process mechanism, which was attributed to the deposition of a fat layer at the solid matrix surface, hindering water and solids uptake. Yet, for short times, moisture uptake proceeded at a similar rate both in skimmed and whole milk.
Comparative Industrial Sociology and the Convergence Hypothesis
Industrial sociology grew spectacularly after World War II, concentrating on three areas: workers' relations with each other, their managers, and their unions; the social organization of the factory; and the impact of technology on social systems extending from the factory to the society. Unable to sus­ tain leadership in all of these areas, industrial sociology shrivelled as other fields invaded its domains. Human relations became the ideological property of the business schools; labor economics maintained its grip on industrial relations; industry-community relations waned as interest in community power soared; industrial organizations were absorbed into the study of com­ plex organizations; occupational sociology maintained research impetus in labor force analysis; and the sociology of the economy dominated the study of industry's institutional relationships. Industrial sociology survived on remnants: worker-machine relationships (job satisfaction, alienation, un­ employment), organizational responses to technological changes. and a bit of working-class ethnology. Enduring interest in technology, however, en­ abled industrial sociology to take part in sociology's expanding interest in comparative studies.