Narchi I, Vial Ch, Djelveh G
Laboratoire de Génie Chimique et Biochimique, Université Blaise Pascal, Aubière cedex, France.
Appl Biochem Biotechnol. 2008 Dec;151(2-3):105-21. doi: 10.1007/s12010-008-8136-0. Epub 2008 Feb 21.
The aim is to understand the effect of matrix elasticity on continuous foaming using food models based on glucose syrup. This was modified by adding polyacrylamide (PAA) with 2% whey protein isolate (WPI) or Tween 80 as foaming agents. Foaming was conducted in a stirred column. Rotation speed N and gas-to-liquid flow ratio (G/L) were varied. Overrun, average bubble size d (32), texture and stability were measured using densimetry, image analysis, and rheometry, respectively. Experimental results showed that 0.01% PAA did not modify the viscosity of 2% WPI models, but conferred low elastic behavior. PAA (0.05%) doubled matrix viscosity and drastically increased elasticity. The increase of elasticity became slower for further PAA addition. Foaming experiments demonstrated that theoretical overrun could not be achieved for inelastic WPI models in two cases: for high viscosity and low N, as dispersion effectiveness was reduced; for high G/L and N because of enhanced coalescence. Matrix elasticity was shown to increase overrun at constant viscosity for high G/L by enhancing interface stabilization. However, in elastic models, gas dispersion was more difficult and d (32) was higher than in inelastic fluids of similar viscosity. Finally, when the limiting step was dispersion, foaming was shown to be negatively affected by matrix elasticity.
目的是利用基于葡萄糖浆的食品模型来了解基质弹性对连续发泡的影响。通过添加含2%乳清蛋白分离物（WPI）的聚丙烯酰胺（PAA）或吐温80作为发泡剂对其进行改性。发泡在搅拌柱中进行。改变转速N和气液流量比（G/L）。分别使用密度测定法、图像分析和流变学测量膨胀率、平均气泡尺寸d(32)、质地和稳定性。实验结果表明，0.01%的PAA不会改变2%WPI模型的粘度，但会赋予其低弹性行为。0.05%的PAA使基质粘度加倍并显著提高弹性。进一步添加PAA时，弹性的增加变得更慢。发泡实验表明，在两种情况下，无弹性的WPI模型无法实现理论膨胀率：对于高粘度和低N，由于分散效果降低；对于高G/L和N，由于聚并增强。通过增强界面稳定性，基质弹性在高G/L下以恒定粘度增加膨胀率。然而，在弹性模型中，气体分散更困难，d(32)高于类似粘度的无弹性流体。最后，当限制步骤是分散时，发泡显示受到基质弹性的负面影响。
