Lung J, Doyen A, Remondetto G, Pouliot Y, Brisson G
Department of Food Sciences, Institute of Nutrition and Functional Foods (INAF), Dairy Science and Technology Research Centre (STELA), Université Laval, Quebec, Quebec, G1V 0A6, Canada.
Agropur Cooperative, St Hubert, Quebec, J3Z 1G5, Canada.
J Dairy Sci. 2024 Jul;107(7):4235-4247. doi: 10.3168/jds.2024-24353. Epub 2024 Mar 14.
Buttermilk differs from skim milk by the presence of milk fat globule membrane (MFGM) fragments that are released during cream churning. Milk fat globule membrane is rich in health-promoting components, such as phospholipids and membrane proteins, but these compounds have a negative impact on buttermilk techno-functional properties in dairy applications. The isolation of MFGM from buttermilk improved its functionality while also recovering the MFGM bioactive components. Hydroxyapatite (HA) can be used to extract MFGM by adsorption via charged site interactions. However, the affinity of HA to MFGM or the main buttermilk proteins (casein micelles [CM], β-LG, and α-LA) is not known. The influence of important physicochemical parameters such as pH and temperature on these interactions is also unclear. For each buttermilk component, a quartz crystal microbalance diffusion analysis was performed to determine the maximum adsorption time and the attached mass density on HA-coated gold sensors. The influence of pH, ionic strength (IS), and temperature (T) on the affinity of each buttermilk component for HA particles was assessed using a 3-levels and 3-factors Box-Behnken design. The absorption rate was highest for the CM, followed by β-LG and α-LA, and then by the MFGM. Nevertheless, the final maximal attached mass densities to the HA were similar for the MFGM and CM, and 2.5 times higher than for β-LG and α-LA. This difference can be explained by the higher number of binding sites found in CM and their heavier mass. The model obtained by the Box-Behnken design plan showed that the adsorption of the CM changed with T, pH, and IS. These results suggest that the techno-functional properties of buttermilk may be restored by specifically extracting MFGM with HA. Experiments are ongoing to determine conditions for fractionating MFGM directly from buttermilk.
酪乳与脱脂乳的不同之处在于，在搅打奶油过程中会释放出乳脂肪球膜（MFGM）碎片。乳脂肪球膜富含促进健康的成分，如磷脂和膜蛋白，但这些化合物对乳制品应用中酪乳的技术功能特性有负面影响。从酪乳中分离MFGM可改善其功能，同时还能回收MFGM生物活性成分。羟基磷灰石（HA）可通过电荷位点相互作用吸附来提取MFGM。然而，HA对MFGM或酪乳主要蛋白质（酪蛋白胶粒[CM]、β-乳球蛋白[β-LG]和α-乳白蛋白[α-LA]）的亲和力尚不清楚。重要的物理化学参数如pH和温度对这些相互作用的影响也不明确。针对每种酪乳成分，进行了石英晶体微天平扩散分析，以确定在HA包覆的金传感器上的最大吸附时间和附着质量密度。使用三水平三因素的Box-Behnken设计评估了pH、离子强度（IS）和温度（T）对每种酪乳成分与HA颗粒亲和力的影响。CM的吸附速率最高，其次是β-LG和α-LA，然后是MFGM。然而，MFGM和CM最终在HA上的最大附着质量密度相似，比β-LG和α-LA高2.5倍。这种差异可以用CM中发现的结合位点数量更多且质量更重来解释。通过Box-Behnken设计方案获得的模型表明，CM的吸附随T、pH和IS而变化。这些结果表明，通过用HA特异性提取MFGM，酪乳的技术功能特性可能得以恢复。正在进行实验以确定直接从酪乳中分离MFGM的条件。
