Abstract
Hydrochloric acid and ammonium oxalate are used to refine pectin from black tomato pomace. The characterization of pectin‐yield, galacturonic acid (GalA) content, degree of methoxylation, neutral sugar composition and molecular weight, interaction with gallotannin as well as emulsion stability are investigated. Hydrochloric acid‐extracted pectin (HEP) and chelating agent‐extracted pectin (ChEP) satisfy the commercial pectin requirements (GalA% > 65%) and are smooth pectin with high homogalacturonan segments (70.6 and 65.4%, respectively). As the structure results suggest, HEP has fewer and shorter branches compared with ChEP. As titration results suggest, gallotannin is bound by pectin and forms insoluble gallotannin–pectin complexes, the maximum combination gallotannin to pectin mass ratios are 0.28 and 0.47 for HEP and ChEP, respectively. Yet as distribution of volume‐weighted diameter, micrographs and values of surface‐weighted diameter suggest, the emulsions stabilized by HEP show better stability than ChEP. The study shows that ChEP is a better additive in beverages containing gallotannin, while HEP has better emulsifying stability.
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