英文文法詢問 These beans are then dried, roasted,and cooled before being put in a grinding machine,which turns the beans into coffee granules.?

These beans are then dried, roasted,and cooled [before being] put in a grinding machine,which turns the beans into coffee granules.
= These beans are then dried, roasted,and cooled before [they are/they are being] put in a grinding machine,which turns the beans into coffee granules.

有兩個要點:
1.) 原句的寫法 ...before being put in a grinding machine, 簡潔明快，不像...before they are being put in a grinding machine, 囉唆。before being + p.p. 正大行其道，在閱讀時經常會見到。

2.) 時態上來說，是 passive present progressive，但在語意上是不論 "過去、現在、未來"，只要這些 beans被置入磨豆機的那一刻，都要經過乾燥、烘焙和冷卻的過程。

As far as methods of making coffee granules being concerned, these beans are being dried, roasted and cooled prior to putting into coffee-mill for grinding purposes. Yip