Influence of roasting time on the microstructural characteristics and amino acid profile of barley Kolo processed under controlled soaking and dehulling conditions

Abstract

The influence of processing conditions on the microstructure and amino acid composition of roasted barley snack (Kolo), and the relationship between structural changes and nutrient availability, remains insufficiently understood. This study evaluated the effect of roasting time on the microstructure and amino acid composition of Kolo. Microstructural changes were examined using SEM in samples that were soaked for 3 hr, roasted at 380°C for 1–4 min, and subsequently dehulled. Amino acid profiling was conducted on raw and 3 hr soaked, 3 min roasted and dehulled samples using HPLC. Raw barley exhibited a dense endosperm with intact starch granules embedded in a continuous protein matrix. Soaking followed by roasting progressively disrupted the starch–protein network, producing micro-cracks, increased porosity, and structural fragmentation. Samples roasted for 4 min showed severe degradation, whereas 3 min roasting achieved an optimal balance, enhancing matrix openness without excessive deterioration. Amino acid analysis revealed reductions in heat-sensitive amino acids, such as lysine, glutamate, and aspartate, while relatively stable amino acids, including glycine, methionine, leucine, and cystine, increased moderately due to oxidation. Integrating SEM-based structural evaluation with amino acid profiling provides valuable insights for enhancing the nutritional quality of traditionally processed Kolo.