SOLUBLE FIBER FROM RED BEET (Beta vulgaris L. var. conditiva) WASTES

FISSORE ELIANA N; ROJAS ANA M; GERSCHENSON LÍA N

Roma

Conferencia; 5th International Dietary Fibre Conference 2012; 2012

International Asociation for Cereal Science and Technology

By-products of vegetable-food processing represent a major disposal problem for the industry. Transformation of vegetable waste of the food industry into value added products, as fibers are, may contribute to diminish pollution and to recover valuable biomass and nutrients. The isolation of pectin-enriched products from the food industry wastes constitutes an interesting alternative since pectins are widely used as texture modifiers in food and pharmaceutical industries. The objective of this research was to explore the feasibility of isolation of pectin from residues of beetroot (Beta vulgaris L. var. conditiva) industrialization with the primary aim of waste upgrading. For the extraction procedure beetroots were peeled and juice was removed. The residue was washed, dried (85ºC, 2h), milled and sieved (420-710 um). The cell wall material obtained (10g) was treated with with 2 M-NaOH solution (500 mL) at 25ºC for 30 min and then filtered. The residue obtained was poured into a beaker containing 1000 mL of 0.05 M-sodium citrate buffer solution. The pH was adjusted to 5.2 with citric acid and the systems were then submitted to digestion with a cell wall degrading enzyme. Enzymes used were hemicellulase or cellulase (SIGMA, St. Louis, USA). The assay was performed at 30ºC for 20h. Insolubles obtained after digestions were separated through filtration and cell wall polysaccharides were finally precipitated from each supernatant through ethanol addition (2 volumes), collected through filtration under vacuum and freeze-dried. Yields obtained were 9.6% for hemicellulase treatment and 20.7% for cellulase treatment. Both fractions were characterized by an almost total demethylation (Degree of Methylation 2.5%) and deacetylation (Degree of acetylation < 2%) as expected, after saponification suffered by the methyl esters at the C6-carboxylic groups of galacturonic acid (GalA) monomers, during the alkaline pretreatment. Hemicellulase fraction showed a total carbohydrate content of 94% with 47% GalA and 2% protein. Cellulase fraction presented 88 % total carbohydrate content with 54% GalA and 2% protein. The most important distribution of molecular weights for both fractions occurred around a broad (685-300) peak at 457 KDa. The extractive process developed permitted the extraction of products enriched in low methoxyl pectins with high yields, especially when celullase was used. These water-soluble fiber products with important molecular weights have promising chemical characteristics in relation to their use as potential thickeners in food and pharmaceutical formulations. The results obtained contribute to the conversion of residues of beetroot into value added products and its adaptation for bioconversion of other agro- industrial residues can be performed tending to environmental protection, non-contaminating industrial procedures and optimum raw materials utilization.