Characterization of soluble fibro-protein extract from Tunisian date seeds "Deglet Nour" by targeted and untargeted techniques

The present study aims to characterize Tunisian date seeds "Deglet Nour" and to determine the functional properties of the fibro-protein fraction obtained by simple water extraction. Date seed powder contains 10.61 g/100g water, 5.00 g/100g protein, 1.48 g/100g ash, 5.39 g/100g fat and 77.50 g/100g carbohydrate. The fibro-protein extract was prepared from defatted date seed powder by isoelectric precipitation at pH 4.5. The extract contained 18 g/100g of proteins with a yield of 18.58%. The oil retention capacity and water retention capacity were 3.23 g/ml and 3.04 g/ml, respectively. The emulsion capacity was significantly higher at pH 10 (174.04 m2/g) than at pH 7 (149.30 m2/g) and pH 4 (143.13 m2/g); however, a more stable emulsion over time was observed at pH 7. Protein solubility was improved with increasing pH from 4 to 7 and 10. The Fourier transform mid-infrared spectroscopy (FTIR) showed the presence of proteins at 1300–1400 cm−1, 1615–1652 cm−1 (Amide I), 1557–1437 cm−1 (Amide II) and 1212–1340 cm−1 (Amide III) and fibers (771 cm−1, 820 cm−1, 1066 cm−1 and 1110 cm−1). Fluorescence spectroscopy revealed changes in the shape of spectra according to pH values. The obtained results showed that the fibro-protein extract of date seeds "Deglet Nour" presents good techno-functional properties and could be of interest as a natural additive for food applications.