Is it alright to mix freshly pumped breastmilk with chilled breastmilk? Well, opinions vary on this matter. Some experts advise against it, suggesting that combining the two could warm up the previously chilled milk, potentially creating an environment conducive to bacterial growth. 👉🏻👉🏻 However, others argue that breastmilk possesses natural antibacterial properties that might mitigate this risk to some extent.