Hydration properties of durum wheat semolina: influence of particle size and temperature

• Published in: Powder technology 2003-02, Vol.130 (1), p.211-218
• Main Authors: Hébrard, A, Oulahna, D, Galet, L, Cuq, B, Abecassis, J, Fages, J
• Format: Article
• Language: English
• Subjects: Absorption; Biological and medical sciences; Cereal and baking product industries; Chemical and Process Engineering; Engineering Sciences; Food engineering; Food industries; Fundamental and applied biological sciences. Psychology; Heat of absorption; Internal transformation; Isotherm; Kinetics; Life Sciences; Semolina; Temperature
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/S0032-5910(02)00268-1

The hydration of semolina particles is an essential step in couscous processing which leads to binding between particles for the formation of agglomerates. Despite this importance, the hydration properties of such food products are rarely studied and in particular, durum wheat semolina has never been investigated. Here we present a study of the hydration properties of durum wheat semolina by determination of water sorption isotherms, and other characterisation techniques to obtain a better understanding of hydration mechanisms. Equilibrium and dynamic sorption properties have been measured as a function of relative humidity by means of a controlled atmosphere microbalance. It is found that durum wheat semolina presents a type II isotherm [F. Rouquerol, J. Rouquerol, K. Sing, Adsorption by Powders and Porous Solids—Principles Methodology and Applications, Academic Press, 1999] indicative of multi-layer adsorption. The Guggenheim–Anderson–de Boer (GAB) model is used to describe the isotherm and obtain a better understanding of hydration mechanisms and liquid/solid interactions. The effects observed are related to physical properties of the semolina. In particular, the size of the semolina particles is found mainly to influence sorption kinetics: the finer the particles, the faster their sorption kinetics. Increasing temperature in the range 25–45 °C accelerates sorption kinetics. Furthermore, hydration causes no irreversible transformation of semolina components. Thus, absorption kinetics seem to be influenced by physical mechanisms, while the biochemical composition determines the amount of water sorbed. Le procédé de fabrication du couscous se compose de plusieurs étapes: agglomération, cuisson, séchage. Au cours de l'agglomération, les particules de semoule sont hydratées, mélangées et roulées. Par hydratation, des liens se forment entre particules de semoule et permettent leur agglomération. Même si les propriétés d'hydratation de nombreux produits alimentaires sont connues, celles des semoules n'ont jamais été étudiées. Les isothermes de sorption couplées à d'autres caractérisations permettent de comprendre les mécanismes d'interactions eau-semoule. Les propriétés de sorption, variations de masse et de temps en fonction de l'humidité relative, ont été mesurées par une balance de sorption. La semoule présente des isothermes de sorption de type II [F. Rouquerol, J. Rouquerol, K. Sing, Adsorption by Powders and Porous Solids—Principles Methodology and Appl