engleski

Properties of extruded corn flours with added cocoa shell extracts

Extrusion is a popular process often used for the modification of flours with the aim to improve their properties. The aim of this study was to investigate the properties of corn flours obtained by milling of corn grits extrudates produced with addition of cocoa shell aqueous extracts. The extracts were prepared by using cold plasma as innovative technology and included extraction under following conditions: 1) ratio cocoa shell : water = 1 : 50, cold plasma frequency 100 Hz for 60 min ; 2) ratio cocoa shell : water = 1 : 30, cold plasma frequency 100 Hz for 30 min. The obtained extracts were added in corn grits in order to prepare the samples with 15% moisture content. Prepared samples were extruded in the laboratory single screw extruder at two different temperature profiles: 1) 135/170/170 °C ; 2) 155/185/185 °C, by using screw with compression ratio 4:1 and die with 4 mm diameter. Obtained extrudates were air-dried, milled and physical and rheological properties of flours were determined. The obtained results showed the extrusion process significantly changed all investigated properties of flours in comparison with non-extruded sample. Water absorption index (WAI) and water solubility index (WSI) increased, where the higher temperature profile had a greater effect. Damage of starch (DS) increased and resistant starch (RS) content decreased after extrusion process, regardless of the type of extract. The obtained results for rheological properties indicate the extrusion process decreased peak viscosity as well as that the extruded samples were less prone to retrogradation.

extruded corn flours ; cocoa shell extracts ; physical and rheological properties

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