Chandrapala Jayani, Duke Mikel C, Gray Stephen R, Zisu Bogdan, Weeks Mike, Palmer Martin, Vasiljevic Todor
Advanced Food Systems Research Unit, College of Health and Biomedicine, Victoria University, Werribee campus, VIC 3030, Australia.
Institute for Sustainability and Innovation, College of Engineering and Science, Victoria University, Werribee campus, VIC 3030, Australia.
J Dairy Sci. 2015 Jul;98(7):4352-63. doi: 10.3168/jds.2015-9435. Epub 2015 May 7.
Compositional differences of acid whey (AW) in comparison with other whey types limit its processability and application of conventional membrane processing. Hence, the present study aimed to identify chemical and physical properties of AW solutions as a function of pH (3 to 10.5) at 4 different temperatures (15, 25, 40, or 90°C) to propose appropriate membrane-processing conditions for efficient use of AW streams. The concentration of minerals, mainly calcium and phosphate, and proteins in centrifuged supernatants was significantly lowered with increase in either pH or temperature. Lactic acid content decreased with pH decline and rose at higher temperatures. Calcium appeared to form complexes with phosphates and lactates mainly, which in turn may have induced molecular attractions with the proteins. An increase in pH led to more soluble protein aggregates with large particle sizes. Surface hydrophobicity of these particles increased significantly with temperature up to 40°C and decreased with further heating to 90°C. Surface charge was clearly pH dependent. High lactic acid concentrations appeared to hinder protein aggregation by hydrophobic interactions and may also indirectly influence protein denaturation. Processing conditions such as pH and temperature need to be optimized to manipulate composition, state, and surface characteristics of components of AW systems to achieve an efficient separation and concentration of lactic acid and lactose.
与其他类型的乳清相比，酸性乳清（AW）的成分差异限制了其可加工性以及传统膜处理的应用。因此，本研究旨在确定在4个不同温度（15、25、40或90°C）下，AW溶液的化学和物理性质随pH值（3至10.5）的变化情况，从而提出合适的膜处理条件，以有效利用AW物流。随着pH值或温度的升高，离心上清液中矿物质（主要是钙和磷酸盐）和蛋白质的浓度显著降低。乳酸含量随pH值下降而降低，在较高温度下升高。钙似乎主要与磷酸盐和乳酸形成络合物，这反过来可能诱导了与蛋白质的分子吸引力。pH值升高导致形成更多具有大粒径的可溶性蛋白质聚集体。这些颗粒的表面疏水性在温度升至40°C时显著增加，进一步加热至90°C时则降低。表面电荷明显依赖于pH值。高浓度的乳酸似乎通过疏水相互作用阻碍蛋白质聚集，也可能间接影响蛋白质变性。需要优化诸如pH值和温度等处理条件，以控制AW系统中各成分的组成、状态和表面特性，从而实现乳酸和乳糖的有效分离和浓缩。
