Inulin is the most important natural storage carbohydrate in plants after starch. It is the main reserve carbohydrate in global artichoke, an edible vegetable widely consumed in the Mediterranean diet. The non-digestibility, low caloric value and fermentability properties of inulin are of great interest in food and pharmaceutical fields. The main objective of this work is the characterization and quantification of inulin from raw and processed (blanched) artichoke industrial by-products, focusing on the effect of ultrasound in the extraction. Extraction of inulin was similar using either conventional or US extraction, although the latter was less time-consuming (60 min vs. 15 min) and need lower temperature (80 °C vs. 60 °C) . The parameters considered to evaluate the quality of extracts from these artichoke by-products were pH, protein, total carbohydrates and reducing sugar content. As expected, both total carbohydrates and protein content was lower for blanched samples. Moreover, Size-exclusion chromatography used to inulin characterization showed a decrease in the low molecular weight carbohydrates content for blanched samples, and the most abundant fragments derived from raw material had an estimated Mw lower than 10 kDa. In addition, gas chromatography (GC) was also used for the analysis of the low Mw carbohydrates (mono-, di-, tri-, tetra- pentasaccharides and poly-alcohols) present. At last, hydrolysis of inulin with NS-22013 (with a previous test, it is proved that this enzyme had inulinase activity vs. other enzymes which had only cellulase activity) was carried out to attempt to quantify the inulin present in the extracts. GC was also used for the analysis of the released fructose and glucose to evaluate the hydrolysis. However the selected enzyme or hydrolysis conditions were not adequate. The main conclusion is that both extraction conditions are equally effective and a subsequent step of purification is necessary.

Trabajo Fin de Grado. Grado en Química por la Universidad Autónoma de Madrid y realizado en el Instituto de Investigación en Ciencias de la Alimentación (CIAL-CSIC).

Peer reviewed