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Assessment of high intensity ultrasound impact on citrus and apple pectin structure and properties

AuthorsMuñoz-Almagro, Nerea ; Montilla, Antonia ; Moreno, F. Javier ; Villamiel, Mar
Issue Date2015
CitationSECyTA 2015
AbstractPectins are complex carbohydrates composed of up to seventeen different monosaccharides covalently bonded and distributed in different domains mainly constituted by chain of homogalacturonan (65%), rhamnogalacturonan (20-30%) and rhamnogalacturonan-II (1-8%). Although pectins are used in pharmaceutical formulations, it is in the food industry where they can find more applications as gelling agents, thickeners, stabilizers, among others. However, an increasing interest toward pectins is arousing due to their bioactivity derived from their role as dietary fiber, although other properties such as antioxidant capacity are also reported. The composition, structure and properties of pectins depend on the sources and conditions of their obtainment, thus, it is possible to find pectins with similar molecular parameters but with different functional properties. Also, the obtained pectins can be transformed into fractions with different structural characteristics and improved bioactivity by enzymatic or chemical hydrolysis. However, emergent technologies such as high intensity ultrasound (US) is an effective, energy-saving and environmentally friendly way for depolymerisation of biomolecules, that is the mechanical degradation during collapse of bubbles (20-100 kHz) by cavitation. Although the application of US for pectin depolymerisation is known [4], hardly information exists about the evaluation of the structure-function relationship of pectins treated by US. The aim of this work has been the application of different analytical techniques to evaluate the structural changes and the potential modifications in the antioxidant activity suffered by pectin subjected to power US. Aqueous solutions of apple and citrus pectin (0,5%) were treated in an ultrasonic bath (45 kHz) (continuous and intermittent) and in a sonicator (20 kHz) provided by two probes of 3 and 12.7 mm at 30, 50 and 70% of amplitude, controlling the temperature between 30-40°C. Chemical modifications were examined by the determination of reducing power (DNS method), Size Exclusion Chromatography (SEC), Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). Regarding to citrus pectin whose initial relative molecular mass (Mr) was 2900 kDa, the results indicated a Mr reduction of 87%, while in the apple pectin (initial Mr 660 kDa) the Mr reduction reached 51%. The main effects were more pronounced in citrus than in apple pectin, due to the higher compound size in the former. Despite the high reduction of Mr, hardly any change was detected in the antioxidant activity of samples, indicating the suitability of power US to the production of modified pectin but preserving the bioactivity of the initial structures.
DescriptionPóster presentado a la XV Reunión Científica de la Sociedad Española de Cromatografía y Técnicas Afines (SECyTA), celebrada en Castellón del 27 al 30 de octubre de 2015.
Appears in Collections:(CIAL) Comunicaciones congresos
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