Preparation and Formation Mechanism of Spherical Particles\nwith High Quality: A Case Study of l‑Isoleucine

As\none of the eight essential amino acids in the human body, l-isoleucine plays an important role in human life metabolism\nand can be applied as a nutritional supplement and food additive in\nthe food field. However, the crystallization of l-isoleucine\nis generally flaky with poor powder properties, such as bulk density\nand flowability, which is not conducive to a wide range of industrial\napplications. In this study, we successfully prepared large spherical\nparticle crystals via two different ways of crystallization. l-Isoleucine undergoes the evolution from initial round flakes to\nthree-dimensional petal-like structures and finally to spherical particles\nby evaporation crystallization in the presence of hydroxypropylmethylcellulose\n(HPMC). l-Isoleucine also aggregates into spherical particles\nin the acid–base reaction crystallization process by adding\na small amount of suitable and volatile bridging liquids, such as\ncyclohexane and ethyl acetate. In conclusion, both approaches improved\nthe crystal properties of l-isoleucine and produced spherical\nparticles with a larger particle size, higher bulk density, and higher\ncompression resistance, thereby providing new insight into the preparation\nof high-quality l-isoleucine.