Acid hydrolysis and carbohydrates characterization of coffee pulp

Hydrolysis of coffee pulp with diluted sulfuric acid was studied by keeping boiling temperature with reflux, a liquid to solid ratio of 10:1 and a particle size ≤ 1.00 mm. Coffee pulp was treated using several acid concentration (C) and retention times (t). The hydrolysates were analyzed for total sugars by phenol-sulfuric acid and HPLC (TSPA and TSHPLC), reducing sugar (RS) by DNS and individual sugars by HPLC. Data were analyzed by using the Statistical Analysis System (SAS). The average sugar yields were: TSHPLC between 12.87-20.31% and 14.02-19.01%; TSPA between 23.41-19.07% and 25.74-30.58%; RS between 10.24-19.07% and 9.66-17.80% for (C) y (t) respectively, expressed as wt% of dry coffee pulp. The general range of variations for individual sugars was: xylose from 0.08 to 3.23; arabinose from 0.23 to 11.26; fructose from 0.90 to 3.00 and glucose from 1.30 to 6.31, expressed in gl^-1 The sucrose varied between 0.08 and 3.96 and maltose between 0.01 and 3.50, also expressed in gl^-1 of hydrolysate. The overall efficiency of hydrolysis was 64% for TSPA and 67% for RS.