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Crystallization Kinetics and Mechanical Properties of Nougat Creme Model Fats
Food Biophysics ( IF 3 ) Pub Date : 2019-07-15 , DOI: 10.1007/s11483-019-09596-w
Stephen-Sven Hubbes , André Braun , Petra Foerst

Fat crystal networks result from a crystallization process, forming interlinked crystal aggregates of viscoelastic character. Palm oil-based fat crystal networks, such as chocolate and nougat spreads, often show liquid oil separation during storage because the fat crystal network is too weak to retain the liquid oils trapped within its structure. To explore the relationship between crystallization kinetics and subsequent mechanical properties, i) palm oil from three different geographical origins and with diverging crystallization properties, ii) mixtures of Ghanaian palm oil with gradually increasing additions of hazelnut oil, and iii) blends of Ecuadorian palm oil with palm stearin as a tripalmitin (PPP)-rich fraction were investigated. Kinetic parameters were acquired from an extended Avrami model by isothermal differential scanning calorimetry measurements, and the results combined with the elastic properties measured by oscillation rheology since studying crystallization kinetics alone insufficiently informs about the mechanical/structural properties needed to overcome liquid oil separation. Rate constants of all investigated fats followed bell-shaped curves, with curve progression strongly dependent on the lipid composition. Ameliorating crystallization properties entailed enhanced elastic properties. The higher the maximum rate constants, the higher the elastic modulus and the gel rigidity of the respective fats. However, two different linear regions of elastic modulus versus PPP or solid fat content resulted, depending on whether palm oil was diluted with hazelnut oil or blended with a PPP-rich fraction. Hazelnut oil strongly diluted crystallizable portions of the structuring fat, thereby decreasing the mechanical properties in a power-law fashion, because the fat crystal network became less connected between fat crystal aggregates.

中文翻译:

牛轧糖奶油模型脂肪的结晶动力学和力学性能

脂肪晶体网络是由结晶过程形成的,形成具有粘弹性特征的互连晶体聚集体。基于棕榈油的脂肪晶体网络(例如巧克力和牛轧糖涂抹酱)在存储过程中经常显示出液体油分离,因为脂肪晶体网络太弱而无法保留滞留在其结构中的液体油。为了探索结晶动力学与随后的机械性能之间的关系,i)来自三个不同地理起源且具有不同结晶性能的棕榈油,ii)加有逐渐增加的榛子油加纳棕榈油的混合物,iii)厄瓜多尔棕榈油的混合物用棕榈硬脂精作为富含三棕榈精(PPP)的级分进行了研究。动力学参数是通过等温差示扫描量热法从扩展的Avrami模型获取的,并且将结果与通过振荡流变学测量的弹性性质相结合,因为仅研究结晶动力学不足以告知克服液油分离所需的机械/结构性质。所有研究的脂肪的速率常数遵循钟形曲线,曲线的变化在很大程度上取决于脂质的组成。改善结晶性能需要增强的弹性。最大速率常数越高,各个脂肪的弹性模量和凝胶刚性越高。但是,得出了弹性模量与PPP或固体脂肪含量的两个不同线性区域,取决于棕榈油是用榛子油稀释还是与富含PPP的馏分混合。榛子油强烈稀释了结构脂肪的可结晶部分,从而以幂律方式降低了机械性能,因为脂肪晶体网络在脂肪晶体聚集体之间的连接变得较少。
更新日期:2019-07-15
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