Extraction and functionality of membrane-concentrated protein from defatted Rosa rubiginosa seeds

Rosa rubiginosa protein was extracted either with distilled water or in the presence of 0.5 M NaCl and further concentrated by ultrafiltration membranes. Temperature and pH influenced the extractability of both protein and polyphenolic compounds. Up to 55–60% of the initial protein was solubilized during alkaline extraction. More than 90% of the solubilized protein was recovered in the unwashed concentrate, which contained more than 80% pure protein (d.b.). Grinding and the presence of NaCl during extraction influenced both the nutritional and functional properties of the protein products. These latter properties could be related to the molecular weight distribution of the extracted protein. The protein concentrated by ultrafiltration was highly soluble in the range of neutral and alkaline pH and the concentrates showed water- and oil-holding capacities up to 26.75 and 16.33%, respectively. The solid byproduct after protein extraction has potential for food uses due to both the high dietary fibre content, and the water and oil absorption capacities.