DETERMINATION OF THE RELEVANT VARIABLES FOR THE PRETREATMENT OF ALPERUJO TO INCREASE SUGAR BIOAVAILABILITY

Alperujo (AL) is the semisolid residue from the olive oil production by two phase centrifugation system. In San Juan (Argentine), about 40,000 MG of AL are annually produced. AL is a highly polluting waste (COD: 230-240 g/kg and BOD: 90 g/kg, approximately), and its treatment and disposal is a concerning problem. AL contains mineral and organic matter, including tannins, polyphenols, polyalcohols, pectins, sugars and lipids. Some of these compounds serve as nutrients for microorganisms, which constitutes a way to valorize the AL. The carbohydrate content in AL is about 20-25% (wet matter) and approximately 70% of which are cellulose and hemicelluloses units. To increase the soluble carbohydrate content, i.e., its bioavailability, these materials are usually subjected to physical, chemical, biological or electrical pre-treatments. Chemical pretreatment using diluted sulphuric acid is recognized to be one of the more advantageous methods because of its easy implementation, low cost and high efficiency. However, the importance of the conditions that may affect the efficacy of this treatment has not been clearly stated. This work reports the results of applying the Plackett-Burman method to determine the relevance of the following variables: sulphuric acid concentration, time, temperature, solid/liquid ratio, pressure and agitation rate. The usual ranges for these variables were determined from the literature and eight experiences were carried out, combining them according to the Plackett-Burman methodology. As response, the sugar content at the end of each treatment was quantified. Results show that sulphuric acid concentration and treatment temperature are the most relevant variables (confidence level 99%) for the increase of the sugars content in AL. The results are encouraging and optimization studies of the relevant variables are in progress.