Original scientific paper
Moisture sorption isotherms of dehydrated whey proteins
Suzana Rimac Brnčić
orcid.org/0000-0002-5657-9379
; Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia
Vesna Lelas
Zoran Herceg
Marija Badanjak
Abstract
Moisture sorption isotherms describe the relation between the moisture content of the dry material (food) and relative humidity of the surrounding environment. The data obtained are important in modelling of drying process conditions, packaging and shelf-life stability of food that will provide maximum retaining of aroma, colour and texture as well as nutritive and biological value. The objective of this research was to establish the equilibrium moisture content and water activity, as well as monolayer value of two commercial powdered whey protein isolates before and after tribomechanical micronisation and enzymatic hydrolysis, respectively. At the same time it was necessary to evaluate the best moisture sorption isotherm equation to fit the experimental data. The equilibrium moisture contents in investigated samples were determined using standard gravimetric method at 20 °C. The range of water activities was 0.11 to 0.75. The monolayer moisture content was estimated from sorption data using Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) models. The results have shown that tribomechanically treated whey protein isolates as well as protein hydrolizates had lower monolayer moisture content values as well as higher corresponding water activity. Therefore, in spite of the fact that they have lower moisture content, they can be storage at higher relative humidity compared to untreated samples. BET model gave better fit to experimental sorption data for a water activity range from 0.11-0.54, while GAB model gave the closest fit for a water activity to 0.75.
Keywords
whey protein; water sorption isotherm
Hrčak ID:
49404
URI
Publication date:
22.3.2010.
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