*2.6. Soluble Solids*

The cowpeas were homogenized, filtered and centrifuged to yield a supernatant, in which soluble solids were measured using a refractometer (WYA-2WAJ, Shanghai Lichen Instrument Technology Co., Ltd., Shanghai, China).

### *2.7. Respiratory Rate*

The cowpeas (approximately 1 kg) were tightly sealed in a 1000 mL glass container at 25 ◦C for 2 h. The carbon dioxide content of the headspace was determined using a Trace 2000 GC and a Thermo mass spectrometer [13].
