Estimation of the content of pectins in feeds: Fractional extraction and quantitative determination

Pectic substances, found in the primary cell wall and middle lamella of the plant tissues as complex polymers of galacturonic acid, play an important nutritional role in the gastrointestinal tract. Their dietary function is due to their physical properties, which include the ability to form gels, to build cations and to increase the waterholding capacity (Voragen et al., 1995, 2001). These physical characteristics are dependent on the substances’ chemical structure and, consequently, pectic substances are fractionated into HM pectins (high-methoxyl pectins), LM pectins (low-methoxyl pectins) and protopectin (Thibault and Ralet, 2001). Must studies have been carried out on fruit because the ripening process induces a modification of the amount of total pectins (TP) and also of the ratio among the three fractions Robertson, 1979). Moreover, the additives employed in the food industry are usually obtained from apple or citrus extraction (Thibault and Ralet, 2001). The purpose of this preliminary work is evaluation of the fractional extraction procedure and quantitative determination of total pectic substances of different feeds. The results obtained in this trial allowed evaluation of the procedure for total pectin determination and a preliminary characterization of the soluble fibre components in feeds, with important implications for their inclusion in diets