Moisture Sorption Isotherm of Durum Wheat Flour

Abstract

The moisture sorption isotherms of durum semolina were observed in the temperature range of 30 to 80℃ for both the sorption and desorption processes. The isotherms of its constituent starch and gluten were observed at 30℃ and that of spaghetti was observed at 60℃. All the isotherms were well expressed by the Guggenheim-Anderson-de Boer equation. The isotherm for the desorption process lay over that for the sorption one at any temperature, and a slight hysteresis was recognized. Isosteric heats, q, for sorption and desorption processes were estimated according to the Clausius-Clapeyron equation as a function of the moisture content of durum semolina. The q values were larger at lower moisture contents, indicating that water molecules more strongly interact with the wheat flour at lower moisture contents. The q values for the desorption process were greater than those for sorption. The isotherms of starch lay over those of gluten at any water activity, and those of spaghetti were located between those of starch and gluten.Keywords: durum wheat flour, moisture sorption isotherm, GAB equation, isosteric heat, Clausius-Clapeyron equation *To whom correspondence should be addressed. E-mail: adachi@kais.kyoto-u.ac.jp IntroductionDurum semolina is a kibble of durum wheat (Triticum durum), which is a hard spring wheat of amber color, and it is mainly used in making pasta, which is prepared by extruding stiff dough (Feillet and Dexter, 1996). The protein of durum wheat plays a crucial role in the texture of cooked pasta.A moisture sorption isotherm has been used to describe the relationship between moisture content and equilibrium relative humidity, and that knowledge is useful for understanding two phenomena in food technology (Lagoudaki et al., 1993). One is the storage stability of food products. The microbial growth, enzymatic reactions, non-enzymatic browning and lipid oxidation are some of the deteriorative mechanisms that are known to be related to the moisture content (Acker, 1969;Labuza, 1984). Another is the drying or rehydration of food. The equilibrium moisture content allows us to optimize drying times and energy utilization. In this context, the moisture sorption isotherms of many food products, for example, starchy foods (e.g., corn, potato, wheat flour and rice), high protein foods (e.g., chicken, egg, milk and cheese), fruits (e.g., banana, apple, apricots and raisins) and vegetables (e.g., green pepper, lentil, tomato, onion, sugar beet root, carrot and celery) have been experimentally determined as reviewed by Al-Huhtaseb et al. (2002).A number of models have been proposed in the literature for the dependence of the equilibrium moisture content and the relative humidity. In 1981, van den Berg and Bruin classified the models into 77 types. These models can be further categorized into several groups: kinetic models based on the monolayer sorption theory (e.g., Langmuir model), kinetic models based on the multilayer sorption theory (e.g., BET and GAB models) and empirical and semi-empirical models (e.g., P...

Moisture sorption characteristics of Greek durum wheat semolina

“…This is attributed to the fact that, as the moisture content increases, the availability of sites for sorption of water diminish and sorption occurs on the less active sites, giving rise to lower heats of sorption . These findings are in accordance with those of recent investigations, on chestnut and wheat flours , on Chinese wheat varieties , on Spanish whole wheat flour , and on Japanese durum wheat flour .…”

The Effect of Various Dosages of Poly-Cereal Raw Materials on the Drying Speed and Quality of Cooked Pasta During Storage

“…In addition, a number of works also show similar results. 13,14,30 This comparative analysis with other studies indicates the reliability of the results obtained in this paper and the assumptions made.…”

“…These data are useful for understanding the phenomena that occur during the drying or rehydration of food. 14 The equilibrium moisture content allows to optimize the drying time and energy use. In addition, the data gained may be useful for assessing storage stability of food products.…”

Engineering aspects of rate-related processes in food manufacturing

“…149) A further study showed that the moisture sorption and desorption isotherms of durum semolina for a temperature range of 30-80°C were well expressed by the Guggenheim-Anderson-de Boer equation; while the desorption isotherm could be overlaid with the sorption one at any temperature, a slight hysteresis was observed. 150) Meanwhile, the partial molar volume of water sorbed to durum wheat flour was measured by dilatometry, which showed that the volume increased with moisture content and reached a constant value of about 17.5 cm 3 /mol at 0.2 kg-H 2 O/kg-d.m. 151) Water sorption of pasta The temperature dependency of equilibrium moisture content and initial sorption rate in spaghetti indicated that the former is limited by starch gelatinization and the latter is governed by diffusion through pores, a process independent of starch gelatinization.…”