Combined Effect of Extraction and Purification Conditions on Yield, Composition and Functional and Structural Properties of Lupin Proteins
Résumé
Lupin meal presents great potential as an alternative plant-based source of proteins for hu-
man nutrition. In the present work, different conditions of extraction and purification were evaluated
for production of lupin protein isolates. The results showed that the protein extraction yield was
comparable at acidic and conventionally used alkaline extraction pH (37% vs. 40–45%, respectively).
Proteins extracted were principally composed of globulins. The ionic strength negatively impacted
the protein extractability at pH 2, whereas no significant differences were observed between extrac-
tions at 20 to 50 ◦C. The selected extraction conditions (pH 2 and 7) combined with purification by
isoelectric precipitation or ultrafiltration process generated the isolate-grade products. Interestingly,
further characterization revealed a partial denaturation of proteins extracted at pH 2 resulting in loss
of protein solubility at pH 6 and 7 (10–50%), modifications in secondary structure, lower thermal
stability, and formation of protein aggregates. However, foaming and emulsifying properties were
generally similar for almost all lupin isolates. Further investigation might be of interest with regard to
the extraction behaviours and structural and functional properties of specific lupin protein fractions.
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