Advanced Food Systems Research Unit, Institute of Sustainable Industries and Liveable Cities and College of Health and Biomedicine, Victoria University, Werribee campus, Victoria 3030, Australia.
School of Science, RMIT University, Bundoora, VIC 3083, Australia.
J Dairy Sci. 2020 Dec;103(12):11050-11061. doi: 10.3168/jds.2020-18375. Epub 2020 Oct 15.
The presence of acids in a lactose-containing system can affect its crystallization. The crystallization kinetics of lactose solutions were investigated as affected by lactic, citric, or phosphoric acid at a concentration of 0.05, 1, or 4% (wt/wt) as compared with that of pure lactose. The crystallization behavior of lactose was affected differently by the presence of all 3 acids and was mostly concentration dependent. The presence of 1 and 4% citric or phosphoric acid reduced the crystal yield significantly (≥18%) as compared with that of pure lactose (∼82%). Thermographic analysis of lactose crystals showed that the presence of 1% lactic, 0.05 and 1% citric, and 4% phosphoric acids in the lactose solutions induced the formation of amorphous lactose. X-Ray diffraction analysis revealed that the lactose crystallized mainly into α-lactose monohydrate, stable anhydrous α-lactose, and anhydrous crystals containing α-lactose and β-lactose in a molar ratio of 5:3 and 4:1. Average size of the lactose particles, comprising of several crystallites, declined depending on the type of the acids and their concentration, but size of a single crystallite was not altered. The findings suggested that the lactose crystallization and crystal properties are governed by the lactose-water interactions, which can be influenced by the presence of acids in a concentration-dependent manner.
乳糖系统中酸的存在会影响其结晶。研究了乳酸、柠檬酸或磷酸在 0.05%、1%或 4%（wt/wt）浓度下对乳糖溶液结晶动力学的影响，与纯乳糖相比。三种酸的存在都会对乳糖的结晶行为产生不同的影响，且主要取决于浓度。与纯乳糖（约 82%）相比，1%和 4%柠檬酸或磷酸的存在显著降低了晶体产率（≥18%）。乳糖晶体的热分析表明，1%乳酸、0.05%和 1%柠檬酸以及 4%磷酸的存在会在乳糖溶液中诱导无定形乳糖的形成。X 射线衍射分析表明，乳糖主要结晶为α-乳糖一水合物、稳定的无水α-乳糖和无水晶体，其中α-乳糖和β-乳糖的摩尔比为 5:3 和 4:1。乳糖颗粒的平均粒径（由多个晶核组成）取决于酸的类型和浓度，而单个晶核的大小没有改变。研究结果表明，乳糖的结晶和晶体性质受乳糖-水相互作用的控制，而酸的存在可以以浓度依赖的方式影响这种相互作用。
