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Towards the development of corn flour rich in densely packed matrices and isomaltooligosaccharides (IMOs)
M. M. MARTINEZ (1), M. Gomez (1). (1) University of Valladolid, Palencia, Spain

A feasible process for the industry to manufacture corn flours rich in densely packed matrices and IMOs was developed. Native, boiled and extruded corn flours were subjected to enzymatic treatment by transglucosidase (T), transglucosidase and maltogenic α-amylase (T+α) and transglucosidase and pullulanase (T+P). Hydrolysis kinetics was assessed by measuring iodine binding capacity, carbohydrates content and oligosaccharides profile of supernatants after washing samples with water or ethanol at different reaction times. The microstructure, crystalline polymorphism, amylose/amylopectin ratio and thermal properties as well as IMOs content of flours obtained at the end of the process were evaluated. Combination of extrusion and enzymatic treatment gave rise to different packing degree affecting the subsequent milling and therefore the flour particle size. In addition, finer molecular changes were also appreciated, such as the apparition of semicrystalline rings and microfibers based flour particles. X-Ray diffraction results showed different crystalline patters and especially how T+α and T+P treatments fostered a higher V-type crystallinity in all flours studied. T+α and T+P treatments increased the enthalpy in native flours. Meanwhile, extruded flour without enzymatic treatment did not present any endothermic peak but their subsequent enzymatic treatment lead to the presence of a noticeable endothermic peak at around 67ºC. The enzymatic treatment of all flours and in particular of boiled and extruded flours, increased the variety of IMOs, highlighting the presence of panose and isomaltotriose. Therefore, work is underway with a view to the discovery and the processes development for designing novel glucans for controlling postprandial hyperglycaemia and health promoting bacteria in the intestinal tract of humans and animals.

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