Changes in color, texture, odor, taste and even biochemical and pharmacokinetic properties can be explained by differences in polymorphy i.e. the crystal structure of a substance. For example, sand and glass are made of the same molecule (SiO2), but have very different properties.
Several factors influence polymorphy, including the rate of change of temperature, pressure and reactants during synthesis. The study of polymorphy is a critical discipline in its own right, integral to the application of chemistry, including materials science and medicine.
So, if you notice a slight difference between batches of products, polymorphy is most likely the reason.