Steam-explosion pretreatment of olive cake |
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Authors: | B Felizón J Fernández-Bolaños A Heredia R Guillén |
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Affiliation: | (1) Departmento de Biotecnología de Alimentos, Instituto de la Grasa (CSIC), Avda. Padre Garcìa Tejero, no 4, 41012 Seville, Spain |
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Abstract: | Olive cake was processed by steam-explosion under different steam conditions, followed by fractionation to separate the main
components. In the water-soluble fraction, the main compounds were carbohydrates. Glucose represented a significant part of
the total monosaccharide content, especially under conditions of mild severity, followed by arabinose, but the solubilization
of sugars occurred predominantly in the oligomeric fraction. Mannitol was also found in significant amounts (1.5%), similar
to that in the initial material. In the ethyl acetate extract, low molecular weight phenols were identified, the most aboundant
being hydroxytyrosol, which is present in the olive pulp. Hydroxytyrosol is abundant and has great antioxidant activity, reaching
149 mg/100 g of dry olive cake. The procedure used in this study obtained all the hydroxytyrosol residual present in the by-product.
The constitutive polymers were quantified in the insoluble fraction, and the sugar composition showed that cellulose was associated
with a high proportion of xylans and other polysaccharides rich in arabinose and galactose. This cellulose was nearly amorphous,
as it was highly susceptible to hydrolytic enzymes. The extractables in dilute alkali (not true lignins) increased as steaming
became more severe; the residual “lignin” in this fraction decreased. Enzymatic hydrolysis of the insoluble fraction using
a cellulolytic complex was also studied. The slight increase in the extent of saccharification was not proportional to the
high alkaline delignification. However, when the residues were efficiently delignified with chlorite treatment, the susceptibility
to enzymatic hydrolysis greatly increased. |
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Keywords: | By-product cellulose olive cake phenols saccharification steam-explosion sugars |
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