Wijayasinghe Rangani, Vasiljevic Todor, Chandrapala Jayani
Advanced Food Systems Research Unit, Institute of Sustainable Industries & Liveable Cities, College of Health and Biomedicine, Victoria University, Melbourne, VIC 8001, Australia.
Biosciences and Food Technology, School of Science, RMIT University, Melbourne, VIC 3083, Australia.
Foods. 2023 Dec 7;12(24):4397. doi: 10.3390/foods12244397.
The inability of lactose to properly crystallize due to the presence of high amounts of salts poses significant hurdles for its downstream processing with some dairy waste streams such as acid whey. This study aimed to investigate the physicochemical and thermal behaviors of lactose in the presence of cations commonly present in acid whey. A model-based study was conducted, utilizing various cations (Mg, Ca, K, and Na) at concentrations (8, 30, 38, and 22 mM, respectively) that are typically found in acid whey. The research experiments were conducted using a factorial design. The thermal analysis of concentrated solutions revealed augmentation in the enthalpy of water evaporation in the presence of individual cations and their combinations in comparison with pure lactose (698.4 J/g). The degree of enthalpy increased following the order of Na (918.6 J/g), K (936.6 J/g), Mg (987.0 J/g), Ca (993.2 J/g), and their mixture (1005.4 J/g). This resulted in a substantial crystal yield decline in the exactly reversed order to that of the enthalpy. The greatest decline was observed in the presence of the salt mixture (63%) followed by Ca (67%) compared with pure lactose (79%). The yield reduction was also inversely related to the solubility of lactose. The presence of divalent cations appeared to play a role in the isomerization of lactose molecules observed using DSC and XRD diffractograms according to the disappearance of peaks related to β lactose. The effect of salts on the crystallization of lactose was a combination of cation-lactose interactions, changes in the solubility of lactose, ion-dipole interactions between water and cations, and changes in the structure of water molecules. By deviating the composition of acid whey, the crystallization of lactose can be enhanced, leading to the improved downstream processing of acid whey.
由于存在大量盐分，乳糖无法正常结晶，这给其与一些乳清废物流（如酸性乳清）的下游加工带来了重大障碍。本研究旨在调查酸性乳清中常见阳离子存在下乳糖的物理化学和热行为。进行了一项基于模型的研究，使用了酸性乳清中通常存在的各种阳离子（Mg、Ca、K和Na），其浓度分别为8、30、38和22 mM。研究实验采用析因设计。对浓缩溶液的热分析表明，与纯乳糖（698.4 J/g）相比，在单个阳离子及其组合存在的情况下，水蒸发焓增加。焓增加的程度顺序为Na（918.6 J/g）、K（936.6 J/g）、Mg（987.0 J/g）、Ca（993.2 J/g）及其混合物（1005.4 J/g）。这导致晶体产率以与焓完全相反的顺序大幅下降。与纯乳糖（79%）相比，在盐混合物存在下观察到最大降幅（63%），其次是Ca（67%）。产率降低也与乳糖的溶解度呈负相关。根据与β-乳糖相关峰的消失，使用DSC和XRD衍射图观察到二价阳离子的存在似乎在乳糖分子的异构化中起作用。盐对乳糖结晶的影响是阳离子-乳糖相互作用、乳糖溶解度变化、水与阳离子之间的离子-偶极相互作用以及水分子结构变化的综合结果。通过改变酸性乳清的组成，可以提高乳糖的结晶，从而改善酸性乳清的下游加工。
