The Effect of Various Processing Methods on Ease of Removal of More than Half the Silver Skin from Green Coffee Beans

It has been shown that the methods utilized to process coffee cherries to dry coffee parchment affect to a considerable extent the ease with which the silver skin may be removed from the green coffee bean subsequently. Natural fermentation is significantly more effective at the 0.01 probability level in producing a sample with an easily removable silver skin than mechanical demucilaging with the Hess machine. Artificial drying produces a sample from which the silver skin can be more easily removed than natural drying at the 0.05 probability level. Furthermore, there was significance at the 0.01 probability level when the interaction between the two main effects of drying and demucilaging were considered. In considering the interaction of the two main effects it was found that natural fermentation combined with artificial (rotary-drier) drying produced the most favorable results. It was significantly greater than any of the other three possible combinations at the 0.01-percent probability level and there was no significant difference between the latter three. This lack of significance may be attributed, in part, to possible negative interaction between the two main effects, that is, in certain combinations the two main effects may have the effect of causing the silver skin to adhere tenaciously to the bean.