46E-8 |
Characterization of pectin extracted from sunflower head residues |
J. E. LOZANO, SR., Food Engineering, PLAPIQUI (UNS-CONICET), Camino La Carrindanga KM.7, Bahía Blanca, 8000, Argentina and M. T. Iglesias. Sunflower pectin, obtained from heads and stalks, is a naturally occurring low methoxyl (LM) pectin. Although information on chemical composition and gelling properties are available, it is known that sunflower variety, location and processing methods affect yield and quality of pectin. The main objectives of this work were (1) to extract pectin from sunflower head residues; to (2) chemically characterize the obtained pectin; and (3) to study the gelling capability of this product. Pectin from sunflower (Helianthus annuus L., var.TC 3004-ATAR) harvested in Cnel. Pringles (Argentina) was isolated using sodium hexametaphosphate extraction followed by either alcohol (OHP) or acid (CLP) precipitation. Degree of methylation (DM); galacturonic acid (AGA) and acetyl ester content were determined by GLC, colorimetry and enzymatic methods, respectively. Viscosity average molecular weight (Mv) was estimated by applying the Mark-Houwink equation. Rheological properties, including gel-point temperature (Tg) were determined with a Bohlin CVO (Bohlin Instruments Ltd., London, UK) rheometer with cone (4cm dia.; 4°) and plate system. Pectin solutions were dynamically tested by (i) controlled cooling and heating (0.1 Hz; 5% strain; 99°- 20°C; 3°C/min) and (ii) frequency sweep ( 0.005 – 1.0 Hz; 5°- 30°C) assays. Magnitudes G´, G”, and phase angle () as a function of temperature were plotted. Temperature where phase angle variation is halved (/2) was regarded as gel point (Tg) . The low methoxyl pectin extracted from sunflower heads had DM=11%; high AGA content (77% - 85%) and low acetyl content (2,3 - 2,6%) on an ash-free basis. Mv was in the range 35300-48.000 for OHP and CLP pectin, respectively. Considering G´ was six times grater than G”, an elastic behavior without network structure rearrange was assumed. Calculated Tg was >90°C, indicating sunflower pectin formed gel almost instantly in the presence of calcium ions at high temperatures. Melting temperature resulted lower than Tg.
Session 46E, International
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