Sunday, May 4, 2008
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Multiple valuation of residues generated by the agro food processing industry

I. Alegría1, M. Zazpe1, C. González-Ferrero2, B. Zarranz1, A. Yetano2, A. Romo2, I. del Campo1, P. Navarro2, and I. Echeverria1. (1) Biomass, Renewable Energy National Centre (CENER), Ciudad de la Innovación 7 31621, Sarriguren, Spain, (2) R+D, Centro Nacional de Tecnología y Seguridad Alimentaria, Ctra. NA-134 km. 31570, San Adrián, Spain

 The aim of this study is the search of alternatives for upgrading residues generated by the agro food processing industry. Two consecutive alternatives have been developed in this project: bioactive compounds extraction and bioethanol production.
Bioactive compounds have been extracted from vegetable wastes generated in the canning industry. Firstly, the characterisation of wastes was carried out, measuring the content of fiber, antioxidant capacity and different vitamins. Subsequently, the extraction of vitamins was made by supercritical fluid extraction (SFE) from a freeze dried and sieved sample. Parameters to be controlled in the extraction are water content and particle-size. Extraction conditions were optimised. A yield of extraction of 41.4% (extracted/initial) was obtained working at 280 bar, 50ºC and particle-size between 0.3 and 0.5 mm.
In order to optimize bioethanol yields, preliminary pre-treatments were carried out varying temperatures (110ºC -120ºC)  and residence times (5 to 20 min). Assays were performed with dry matter content between 5% and 10% with working volumes that varied from 20 ml to 400 ml, in the absence or presence of sulphuric acid (concentration ranged from 0.5 to 1.0 % (wt/wt). Enzymatic hydrolysis was carried out at 50ºC for 72 h followed by fermentation assayed at 37ºC using Saccharomyces cerevisiae.
Characterization of vegetable wastes before and after SFE showed no major differences. Pretreatment process reached a solubilization of 53.6 - 57.7% of the total initial sugar content. Enzymatic hydrolyzation increased this yield in between 8.8 to 9.0 %. Fermentation yields obtained varied from 72-92% with respect to theoretical.