The milk smells off.

这奶的味道不对劲。

《牛津词典》

The food has spoiled.; The food smells a bit off.

饭菜馊了。

《新英汉大辞典》

He is at one with the night forest, with its thousand bio-sources glowing like the milkyway through the dark branches, its strange sounds and smells, water dripping off the unfamiliar leaves.

丛林中弥漫着奇怪的叫声和气味，水滴自从未见过的树叶上滴下。

youdao

If your starter turns pink or orange or it just smells "off, " toss it.

NPR: Sourdough: More than a Bread

Northumbria Police were tipped off about the savoury smells and activities coming from Tabram's bungalow and twice raided her house last May and June.

BBC: NEWS | UK | England | Tyne | Cannabis grandmother spared jail

The biggest losers will be inefficient local producers, such as one in Samara, in southern Russia, where the decrepit town brewery, featuring fermentation tanks with flaking linings, nasty smells and beer brewed to purists' horror from sugar and rice, has fought off all outside interest.

ECONOMIST: Russian beer