Extrusion effect on properties of corn meal mixtures with buckwheat and chestnut flour

Proizvodnja ekstrudata iz različitih vrsta brašna danas je često primjenjivan proces u prehrambenoj industriji. Cilj ovog rada bio je utvrditi utjecaj postupka ekstruzije na svojstva smjesa kukuruzne krupice s heljdinim i kestenovim brašnom (omjeri krupica : brašno = 70 : 30; 50 : 50 i 30 : 70). Smjese vlažnosti 25 % ekstrudirane su pri dva temperaturna profila: 80/90 °C i 75/180 °C. Dobivenim ekstrudatima ispitana su fizikalna, termofizikalna i reološka svojstva te probavljivost u odnosu na neekstrudirane uzorke. Utvrđeno je povećanje ekspanzijskog omjera i smanjenje nasipne mase pri višoj temperaturi ekstruzije, kao i povećanje lomljivosti te smanjenje tvrdoće većine ekstrudata kod više temperature. Ekstruzija je uzrokovala potamnjivanje i povećanje intenziteta boje uzoraka, i to proporcionalno temperaturi ekstruzije. Moć upijanja vode povećala se, i to znaĉajnije pri višoj temperaturi. Ekstruzija je uzrokovala smanjenje udjela rezistentnog škroba (RS). Udio proteina kod većine uzoraka povećao se, a udio masti smanjio nakon provedenog procesa ekstruzije. Ekstruzija je uzrokovala smanjenje viskoznosti vrha. Udio ukupnih polifenola i antioksidativna aktivnost povećali su se dodatkom heljdinog i kestenovog brašna, ali je ekstruzija uzrokovala njihovo smanjenje.Production of extrudates from different types of flour is used widely in the food industry. The aim of this study was to determine the effect of extrusion process on the properties of mixtures of corn meal with buckwheat and chestnut flour (ratio meal : flour = 70 : 30, 50 : 50 and 30 : 70). Blends (25% moisture) were extruded at two temperature regimes: 80/90 °C and 75/180 °C. Physical, thermophysical and rheological properties, and digestibility of the obtained extrudates were investigated in relation to non extruded samples. Results showed an increase in expansion ratio and the reduction of bulk density at the higher extrusion temperature, and increased fragility and decrease in extrudate hardness of most of extrudates produced at the higher temperatures. Extrusion resulted in darker color and increased intensity of color, proportionally to extrusion temperature. Water absorption index increased proportionally to extrusion temperature. Extrusion caused a reduction of the resistant starch content and peak viscosity. Protein content in most samples increased, and fat content decreased after the extrusion process. Total polyphenol content and antioxidant activity increased by the addition of buckwheat and chestnut flour, but the extrusion caused their decrease