Influence of medium-chain triglycerides on expansion and rheological properties of extruded corn starch

• Published in: Carbohydrate polymers 2013-04, Vol.93 (2), p.492-498
• Main Authors: Horvat, Mario, Emin, M. Azad, Hochstein, Bernhard, Willenbacher, Norbert, Schuchmann, Heike Petra
• Format: Article
• Language: English
• Subjects: Applied sciences; Bagley pressure; Biological and medical sciences; Biomechanical Phenomena; corn starch; Elasticity; Elongational properties; Exact sciences and technology; Expansion; Extrusion; Food industries; Fundamental and applied biological sciences. Psychology; gelatinization; Gels - chemistry; health promotion; Inline-rheometer; lipid content; medium chain triacylglycerols; Medium-chain triglycerides; Natural polymers; oils; Oils - chemistry; Physicochemistry of polymers; Porosity; Pressure; Rheology - methods; rheometers; Shear Strength; Solubility; starch; Starch - chemistry; Starch and polysaccharides; Starch and starchy product industries; Transition Temperature; Triglycerides - chemistry; Viscosity; Water; Zea mays - chemistry
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2012.12.052

► Addition of MCT-oil increased sectional expansion by up to three times. ► Longitudinal expansion only slightly decreased upon oil addition. ► Thermomechanical history of starch was not affected by oil. ► We determined the Bagley pressure, which is a measure of elongational properties. ► We observed a change in the Bagley pressure by addition of MCT-oil. Enhancement of product properties of extruded starch based products can be achieved by incorporating health promoting oil into the matrix. In order to achieve a preferably high expansion with a homogeneous pore structure, the expansion mechanisms have to be understood. In our study, we applied a customized twin-screw extruder set up to feed medium-chain triglycerides after complete gelatinization of corn starch, minimizing its effect on the starch gelatinization. Despite the fact, that the addition of up to 3.5% oil showed no influence on the extrusion parameters, we observed a three-fold increase in sectional expansion. Longitudinal expansion was less affected by the oil content. Rheological properties of the gelatinized starch were measured using an inline slit die rheometer. In addition to shear viscosity, we presented a method to determine the Bagley pressure, which reflects the elongational properties of a fluid. We were able to observe an increase in the Bagley pressure from about 25bar up to 35–37bar due to the addition of oil.