Nestlé Product Technology Centre Orbe, Route de Chavornay 3, CH-1350 Orbe, Switzerland.
J Sci Food Agric. 2011 Nov;91(14):2582-6. doi: 10.1002/jsfa.4496. Epub 2011 Jun 14.
Beverage powders can exhibit caking during storage due to high temperature and moisture conditions, leading to consumer dissatisfaction. Caking problems can be aggravated by the presence of sensitive ingredients. The caking behaviour of cocoa beverage powders, with varying amounts of a carbohydrate sensitive ingredient, as affected by climate conditions was studied in this work. Sorption isotherms of beverage powders were determined at water activities (a(w) ) ranging from 0.1 to 0.6 in a moisture sorption analyser by gravimetry and fitted to the Brunauer-Emmett-Teller (BET) or the Guggenheim-Anderson-de Boer (GAB) equation. Glass transition temperatures (T(g) ) at several a(w) were analysed by differential scanning calorimetry and fitted to the Gordon-Taylor equation. Deduced T(g) = f(a(w) ) functions helped to identify stability or caking zones. Specific experimental methods, based on the analysis of mechanical properties of powder cakes formed under compression, were used to quantify the degree of caking. Pantry tests complemented this study to put in evidence the visual perception of powder caking with increasing a(w) .
The glass transition approach was useful to predict the risks of caking but was limited to products where T(g) can be measured. On the other hand, quantification of the caking degree by analysis of mechanical properties allowed estimation of the extent of degradation for each product.
This work demonstrated that increasing amounts of a carbohydrate sensitive ingredient in cocoa beverages negatively affected their storage stability.
由于高温和高湿条件，饮料粉在储存过程中可能会结块，导致消费者不满。存在敏感成分会加剧结块问题。本工作研究了不同量碳水化合物敏感成分的可可饮料粉在气候条件下的结块行为。通过重量法在水分吸附分析仪中测定饮料粉在水活度（a(w)）为 0.1 至 0.6 范围内的吸附等温线，并拟合到 Brunauer-Emmett-Teller（BET）或 Guggenheim-Anderson-de Boer（GAB）方程。通过差示扫描量热法分析了几个 a(w)下的玻璃化转变温度（T(g)），并拟合到 Gordon-Taylor 方程。推断的 T(g) = f(a(w) )函数有助于确定稳定性或结块区域。基于对压缩下形成的粉末蛋糕机械性能分析的特定实验方法用于定量结块程度。食品储藏室测试补充了这项研究，以随着 a(w)的增加显示出粉末结块的视觉感知。
玻璃化转变方法可用于预测结块风险，但仅限于可以测量 T(g)的产品。另一方面，通过机械性能分析对结块程度进行定量可以估计每种产品的降解程度。
这项工作表明，可可饮料中碳水化合物敏感成分的含量增加会对其储存稳定性产生负面影响。
