Pressing of coffee pulp

Abstract Coffee pulp is a by-product of coffee processing representing about 40% by weight of the ripe coffee fruit. In this paper results of coffee pulp pressing experiments are presented and discussed. Pressing trials were carried out with a batch hydraulic press and evaluated by calculation of two parameters, juice yield and extracted solids. Several pretreatments, before pulp pressing, were experimented with, among which were agitation, heating with live steam and adding commercial pectic enzymes. The major chemical components of the juice were analysed in all samples. It has been shown that juice yields close to 60% of the initial fresh weight of pulp can be obtained, extracting with it about 35% of the total solids present, if a combination of pectic enzyme and temperature is employed as pretreatment. The above figures are reduced to 35% and 23%, respectively when there are no pretreatments before pressing. The juice has about 14 Brix, 75% of the total hot water extractable sugars present in fresh coffee pulp, all of the polyphenols, about 50% of the nitrogen and 30% of the caffeine. It can be employed as a raw material for microbial biomass production. The residual solid has a final moisture content of about 70% which makes the material suitable for further composting or ensilage.