Characterization and functional properties of protein isolates from wild almond

Wild almond (Amygdalus scoparia) is a drought-resistant, non-cultivated plant rich in protein. The extraction of protein isolates from wild almond was carried out using NaOH, buffered saline borate (BSB), and Tris-HCl and the isolates were characterized by their physico-chemical, thermal and emulsifying attributes. Use of BSB solution resulted in the maximum recovery of protein (56%, w/w) from wild almond. The amino acid compositions of wild almond protein isolates (WAPIs) were identified by high-performance liquid chromatography after acid hydrolysis. Aspartic and glutamic acids were the most abundant amino acids found in the WAPIs. Differential scanning calorimeter showed that WAPI is denatured above 80 degrees C. It was also found that the surface hydrophobicity values of the NaOH- and BSB-extracted proteins were 375 +/- 6 and 359 +/- 5, respectively. Water absorption capacities of isolates extracted by NaOH and BSB were 2.3 +/- 0.4 and 2.6 +/- 0.3 g water/g protein, respectively. In addition, oil absorption capacities for the isolates extracted using NaOH and BSB were 3.5 +/- 0.7 and 3.1 +/- 0.4 g oil/g protein, respectively. Moreover, the solubility levels of the extracted isolates increased up to 85.3% under alkaline conditions. The emulsion-activity indices of isolates increased at pH < 4 and also at pH > 4.5. In addition, the highest foaming capacity was obtained at pH 2 for the extracted isolates. In conclusion, the study has shown that WAPIs can enhance the oil absorption capacity, emulsifying and foaming properties. Thus, they could be considered for application as an ingredient for functional foods processed in alkaline conditions at temperatures below 80 degrees C.