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首页> 外文期刊>Journal of dairy research >Algal meal supplementation of the cows' diet alters the physical properties of milk fat
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Algal meal supplementation of the cows' diet alters the physical properties of milk fat

机译：补充牛奶中的藻粉会改变牛奶脂肪的物理特性

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A three-week algal meal supplementation of the cows' basal diet resulted in an increase in the firmness of milk fat crystallized isothermally at 5 degreesC for 24 h - the apparent elastic constant increased from 100 to 224 N/mm. This was accompanied by a decrease in solid fat content, from 47(.)7% to 44(.)4%. The crystallization behaviour of milk fat was also modified significantly. The rate constant of crystallization (Avrami constant) of the enriched milk fat at 19 degreesC was similar to20 times higher than that of control milk fat. A shorter induction time of nucleation was also observed in the temperature range [20, 27 degreesC]. These effects were attributed to a higher degree of supersaturation of the enriched milk fat. Enriched milk fat nucleated in a more stable beta' polymorphic form at 5 degreesC, while control milk fat nucleated in the metastable alpha form, as determined by powder X-ray diffraction and differential scanning calorimetry. Changes in the microstructure of the material were observed by polarized light microscopy at 5 degreesC. The enriched milk fat displayed a greater amount of crystal clustering than the control. This effect was reflected in a decrease in the box-counting mass fractal dimension (D-b) of the fat crystal network from 1(.)853 to 1(.)809. The decrease in D-b closely predicted the observed 2(.)2-fold increase in the elastic constant of the fat. These changes in mechanical properties, crystallization behaviour and microstructure were driven by an increase in the 18 : 1 trans and a decrease in the 18 : 1 cis fatty acid content of the enriched milk fat.
机译：为期三周的藻类补充牛的基础饮食，导致在5摄氏度下等温结晶24小时的乳脂的硬度增加-表观弹性常数从100 N / mm增加至224 N / mm。这伴随着固体脂肪含量从47（。）7％降至44（。）4％的降低。乳脂的结晶行为也被显着改变。在19℃下，浓缩乳脂的结晶速度常数（Avrami常数）与对照乳脂的结晶速度常数（Avrami常数）相似，约为20倍。在温度范围[20，27℃]下也观察到较短的成核诱导时间。这些作用归因于富含乳脂的较高的过饱和度。通过粉末X射线衍射和差示扫描量热法测定，富含乳脂在5摄氏度时以更稳定的β'多晶型形式成核，而对照乳脂以亚稳态α形式成核。通过在5℃下的偏光显微镜观察材料的微观结构的变化。富乳脂比对照组显示出更多的晶体簇。胖晶体网络的盒数质量分形维数（D-b）从1（.853）减少到1（.809）反映了这种效果。 D-b的减少紧密预测了脂肪弹性常数的2（。）2倍增加。机械特性，结晶行为和微观结构的这些变化是由富乳脂中18：1反式的增加和18：1顺式脂肪酸含量的下降驱动的。

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