Abstract
Pectic substances from eleven samples of dried apple pomace were extracted using an acid procedure (100 mM HNO3, 10 min., 80oC), dried, ground and stored in a P2O5 atmosphere. The degree of esterification was determined by the classical titrimetric method and confirmed by the instrumental FTIR method. The samples showed an average DE of 73% and the typical fingerprint in IR spectrogram. The steric exclusion chromatograms obtained with the multi-angle laser light scattering (MALLS) and refraction index (RI) detectors showed that all samples had a high molar fraction eluted at 36-38 min., another large polysaccharide family had an elution time around 43 min, and some samples showed yet another low molecular oligosaccharide that appeared at 58-60 min. Gas chromatography of alditol acetate allowed estimates of the proportion of the neutral sugar in the samples. The ratio of galacturonic acid and rhamnose may give the average size of the galacturonan fraction. These results showed that yields of pectin extracted by the same acid procedure were slightly different. However, the degree of esterification of pectin was similar, with both factors pointing to the best sources in this group of varieties.
Highlights
Pectin has been used in jelly manufacture for more than 200 years (WILLATS et al, 2006), but, in praxis, only two traditional sources have been economically important, citrus albedo and apple pomace, despite research into new raw materials (IGLESIAS; LOZANO, 2004; LEVIGNE et al, 2002)
The gravimetric yield was calculated as the ratio (%) of pectin obtained from the apple pomace raw material
Acid-soluble polysaccharide extracted with an average yield of 15.04% ± 1.53 reflects the small difference of hydrocolloids in the raw material, and the average esterification degree of 72.29% points to a good processing
Summary
Pectin has been used in jelly manufacture for more than 200 years (WILLATS et al, 2006), but, in praxis, only two traditional sources have been economically important, citrus albedo and apple pomace, despite research into new raw materials (IGLESIAS; LOZANO, 2004; LEVIGNE et al, 2002). Apple pectin shows a similar rheological quality to that of citrus pectin, but due to the presence of phenol compounds, the latter is preferred for use in translucent or transparent foods. The process of producing a colorless acidic polysaccharide from apple induces the separation of pectin from phenolic compounds by ion exchange chromatography (SCHIEBER et al, 2003). Their composition depends on source, processing and Pectin quality and acid extraction are related to many factors, including the type of fruit (THAKUR et al, 1997), and, concerning apple pomace, the variety and process (COSTENLA et al, 2002), including extraction, purification and drying. The type and concentration of acid (FERTONANI et al, 2006) and the time and temperature of reaction (FERTONANI et al, 2006; GARNA et al, 2007; SCABIO et al, 2007) play a fundamental role in the balance of pectin extraction and degradation
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