Kallu Sravya, Kowalski Ryan J, Ganjyal Girish M
School of Food Science, Washington State Univ., Pullman, Wash., U.S.A.
J Food Sci. 2017 Jul;82(7):1647-1656. doi: 10.1111/1750-3841.13756. Epub 2017 Jun 14.
Objective of this study was to understand the impacts of cellulose fiber with different particle size distributions, and starches with different molecular weights, on the expansion of direct expanded products. Fiber with 3 different particle size distributions (<125, 150 to 250, 300 to 425 μm) and 4 types of starches representing different amylose contents (0%, 23%, 50%, and 70%) were investigated. Feed moisture content (18 ± 0.5 % w.b) and extruder temperature (140 °C) were kept constant and only the extruder screw speed was varied (100, 175, and 250 rpm) to achieve different specific mechanical energy inputs. Fiber particle size and starch type significantly influenced the various product parameters. In general, the smaller fiber particle size resulted in extrudate with higher expansion ratio. Starch with an amylose: amylopectin ratio of 23:77 resulted in highest expansion compared to the other starches, when no fiber was added. Interestingly, starch with 50:50, amylose: amylopectin ratio in combination with smaller fiber particles resulted in product with significantly greater expansion than the control starch extrudates. Aggregation of fiber and shrinkage of surface was observed in the Scanning Electron Microscope images at 10% fiber level. The results suggest the presence of active interactions between the cellulose fiber particles and corn starch molecules during the expansion process. A better understanding of these interactions can help in the development of high fiber extruded products with better expansion.
本研究的目的是了解不同粒度分布的纤维素纤维以及不同分子量的淀粉对直接膨化产品膨胀度的影响。研究了具有3种不同粒度分布（<125、150至250、300至425μm）的纤维以及代表不同直链淀粉含量（0%、23%、50%和70%）的4种淀粉。进料水分含量（18±0.5%湿基）和挤出机温度（140℃）保持恒定，仅改变挤出机螺杆转速（100、175和250转/分钟）以实现不同的比机械能输入。纤维粒度和淀粉类型对各种产品参数有显著影响。一般来说，纤维粒度越小，挤出物的膨胀率越高。在不添加纤维时，直链淀粉与支链淀粉比例为23:77的淀粉相比其他淀粉产生的膨胀度最高。有趣的是，直链淀粉与支链淀粉比例为50:50的淀粉与较小的纤维颗粒结合时，产生的产品膨胀度明显大于对照淀粉挤出物。在扫描电子显微镜图像中，在纤维含量为10%时观察到纤维聚集和表面收缩。结果表明在膨胀过程中纤维素纤维颗粒与玉米淀粉分子之间存在活跃的相互作用。更好地理解这些相互作用有助于开发具有更好膨胀度的高纤维挤压产品。
