Soaking aubergine (eggplant) in milk before frying serves a purpose beyond adding flavour. The soaking process helps to remove any potential bitterness from the aubergine and can also contribute to a better texture when fried. Aubergines can sometimes have a slightly bitter taste due to natural compounds called phenols. Soaking them in milk helps to draw out these bitter compounds, resulting in a milder flavour. Also, the milk helps to tenderise the aubergine and can make it more moist and less prone to absorbing excessive oil during frying. This can result in a lighter and crispier final texture.