Changes in the oligosaccharides and the α-galactosidase content of coffee seeds during soaking and germination

Abstract

The oligosaccharides sucrose, raffinose and stachyose are present in the seeds of different varieties of coffee belonging to the species Coffea arabica and C. robusta that were investigated. The sucrose content was more than ninety times that of raffinose in C. arabica varieties but only about forty times more in the C. robusta variety. Stachyose content in all cases was about 1·5 times greater than raffinose. During soaking, the three sugars decreased by about 50 per cent, and during germination, while there was a further reduction of about 50 per cent in sucrose content, raffinose and stachyose disappeared in the C. arabica varieties and were greatly reduced in the C. robusta variety. During the disappearance of these oligosaccharides traces of glucose and fructose appeared, but galactose, melibiose or manninotriose were not detectable at any stage. α-Galactosidase activity was fairly high in resting seeds. This activity increased by 50–75 per cent on soaking and increased further by another 25–55 per cent on germination of the seeds, the increase being greater both on soaking and on germination in the seeds of C. arabica varieties than in the seeds of the C. robusta variety.