Isoelectric precipitation of protein from pea pod and evaluation of its physicochemical and functional properties

Pea pod shell as a solid waste in processing industries remains unutilized and is discarded as waste. Pea pod powder (PPP) prepared from pea pod waste was found to have 15.79% protein on dry weight basis (db) making it an excellent source of sustainable and vegan protein. In the present study, protein was extracted from PPP using two protocols (A and B) and subjected to air drying (AD-A and AD-B of method A and B, respectively) and freeze drying (FD-A and FD-B of method A and B, respectively). Based on the protein content, the best pH combination for protein extraction and precipitation was identified by employing factorial analysis of variance. Results revealed that pH combination 12.0 (alkali extraction)—3.5 (protein precipitation) was optimum for maximum protein yield (AD-A 48.68%, FD-A 50.64%, AD-B 60.45% and FD-B 63.10% db) from pea pod powder. FTIR spectra for all samples showed characteristic peaks corresponding to the secondary structure of proteins. Further, upon functionality evaluation FD-B protein was found best with higher protein content, high foaming capacity, emulsion stability, low moisture with good foam stability and emulsion capacity. However, sample AD-B was competitive with FD-B in terms of protein yield (60.33% vs 62.76% db), functionality and better handling. Therefore, we recommend heat assisted extraction method of pea pod protein that has been dried under forced air as a feasible low-cost alternative for manufacturing protein concentrate. Thus, the obtained pea pod protein can be incorporated as a high value supplement in human diets.