As others have pointed out, since homogenisation, milk does not really need to be shaken.

Is it bad to shake milk?

There is no published evidence to support that shaking actually damages breast milk when compared to swirling. Many of the issues identified with shaking are better described as myths, and simply do not hold up when the actual shear forces are calculated.

Is shaking milk good?

They've heard that shaking breastmilk harms its nutritional value, because shaking denatures, or breaks down, its protein molecules. ... The truth is, there's no scientific evidence to support the claim that shaking breastmilk takes away from its nutritional value, or that swirling is better.