Effect of walnut flour addition on rheological, thermal and microstructural properties of a gluten free-batter

Abstract

For proper industrialization of gluten-free (GF) foods, it is important to know their properties and behavior under process. This is even more important when using novel ingredients. The by-product of walnut oil (Juglans regia L.) extraction is a press cake rich in polyunsaturated fatty acids and other bioactive compounds. From this cake, walnut flour (WF) is obtained by milling. This study was focused on evaluating the effects of adding WF on the rheological, textural, thermal, and microstructural properties of batters. Different levels of addition of WF (0, 100, 150, 200 g/kg flours blend) were assayed. The pasting properties of the flour blend (rice flour, cassava and maize starches) were altered by WF addition. Likewise, increased WF concentration on batters increased their firmness, cohesiveness and, consistency and viscosity indexes.Regarding the molecular mobility of components of batters, a decrease in the relaxation times in NMR assays and in the amount of freezable water was found while the glass transition was not affected. Confocal scanning laser micrographs of batters showed a protein matrix with starch granules, oil droplets, and fiber fragments. Overall, these results showed that the addition of WF enhanced the quality of the GF batters.