Spent coffee grounds (SCG), the res

Spent coffee grounds (SCG), the residual materials obtained during the processing of raw coffee powder
to prepare instant coffee, are the main coffee industry residues. In the present work, this material was
chemically characterized and subsequently submitted to a dilute acid hydrolysis aiming to recover the
hemicellulose sugars. Reactions were performed according to experimental designs to verify the effects of
the variables H2SO4 concentration, liquid-to-solid ratio, temperature, and reaction time, on the efficiency
of hydrolysis. SCG was found to be rich in sugars (45.3%, w/w), among of which hemicellulose (constituted
by mannose, galactose, and arabinose) and cellulose (glucose homopolymer) correspond to 36.7% (w/w)
and 8.6% (w/w), respectively. Optimal conditions for hemicellulose sugars extraction consisted in using
100mg acid/g dry matter, 10 g liquid/g solid, at 163 ◦C for 45 min. Under these conditions, hydrolysis
efficiencies of 100%, 77.4%, and 89.5% may be achieved for galactan, mannan, and arabinan, respectively,
corresponding to a hemicellulose hydrolysis efficiency of 87.4%.