College of Food Science and Engineering/Collaborative Innovation Center for Modern Grain Circulation and Safety/Key Laboratory of Grains and Oils Quality Control and Processing, Nanjing University of Finance and Economics, Nanjing 210023, China.
Center of Analytical Facilities of Nanjing University of Science and Technology, Nanjing 210094, China.
Food Res Int. 2024 May;183:114226. doi: 10.1016/j.foodres.2024.114226. Epub 2024 Mar 13.
Highland barley (HB) is an intriguing plateau cereal crop with high nutrition and health benefits. However, abundant dietary fiber and deficient gluten pose challenges to the processing and taste of whole HB products. Extrusion technology has been proved to be effective in overcoming these hurdles, but the association between the structure and physicochemical properties during extrusion remains inadequately unexplored. Therefore, this study aims to comprehensively understand the impact of extrusion conditions on the physicochemical properties of HB flour (HBF) and the multi-scale structure of starch. Results indicated that the nutritional value of HBF were significantly increased (soluble dietary fiber and β-glucan increased by 24.05%, 19.85% respectively) after extrusion. Typical underlying mechanisms based on starch structure were established. High temperature facilitated starch gelatinization, resulting in double helices unwinding, amylose leaching, and starch-lipid complexes forming. These alterations enhanced the water absorption capacity, cold thickening ability, and peak viscosity of HBF. More V-type complexes impeded amylose rearrangement, thus enhancing resistance to retrogradation and thermal stability. Extrusion at high temperature and moisture exhibited similarities to hydrothermal treatment, partly promoting amylose rearrangement and enhancing HBF peak viscosity. Conversely, under low temperature and high moisture, well-swelled starch granules were easily broken into shorter branch-chains by higher shear force, which enhanced the instant solubility and retrogradation resistance of HBF as well as reduced its pasting viscosity and the capacity to form gel networks. Importantly, starch degradation products during this condition were experimentally confirmed from various aspects. This study provided some reference for profiting from extrusion for further development of HB functional food and "clean label" food additives.
青稞（HB）是一种具有高营养价值和健康益处的高原粮食作物。然而，丰富的膳食纤维和缺乏面筋使得整个 HB 产品的加工和口感面临挑战。挤压技术已被证明可以有效地克服这些障碍，但挤压过程中结构和物理化学性质之间的关联仍未得到充分研究。因此，本研究旨在全面了解挤压条件对 HB 面粉（HBF）的物理化学性质和淀粉多尺度结构的影响。结果表明，挤压后 HBF 的营养价值显著提高（可溶性膳食纤维和β-葡聚糖分别增加了 24.05%和 19.85%）。建立了基于淀粉结构的典型基础机制。高温促进淀粉糊化，导致双螺旋展开、直链淀粉浸出和淀粉-脂质复合物形成。这些变化提高了 HBF 的吸水性、冷增稠能力和峰值黏度。更多的 V 型复合物阻碍了直链淀粉的重排，从而提高了抗回生能力和热稳定性。高温高湿挤压与湿热处理相似，部分促进了直链淀粉的重排，提高了 HBF 的峰值黏度。相反，在低温高湿条件下，溶胀良好的淀粉颗粒很容易被更高的剪切力破碎成较短的支链，从而提高了 HBF 的即时溶解度和抗回生能力，降低了其糊化黏度和形成凝胶网络的能力。重要的是，从各个方面证实了该条件下淀粉降解产物的存在。本研究为进一步开发 HB 功能性食品和“清洁标签”食品添加剂提供了挤压利用的一些参考。
