2 sentences for 苦涩 (kǔ​sè — bitter and astringent)

1. 这种未成熟的果实吃起来非常苦涩。

   zhè zhǒng wèi chéng​shú de guǒ​shí chī qi​lai fēi​cháng kǔ​sè.

   This unripe fruit tastes very bitter.

   Source: Dong Chinese Dictionary

2. 这种青橄榄嚼起来虽然有些苦涩，但回味很甘甜。

   zhè zhǒng qīng gǎn​lǎn jiáo qi​lai suī​rán yǒu​xiē kǔ​sè, dàn huí​wèi hěn gān​tián.

   Although these green olives are a bit bitter to chew, they leave a sweet aftertaste.

   Source: Dong Chinese Dictionary