Physicochemical Properties of Safflower (<i>Carthamus tinctorius</i> L.) Seed Meal Protein and the Effects of pH and Ionic Strength on Its Functional Characteristics.

Abstract

In recent years, plant proteins recycled from agricultural waste have gained increasing attention in food manufacturing due to the relatively low environmental and economic cost. Safflower (<i>Carthamus tinctorius</i> L.) is an important edible oil crop which generates a large amount of seed meal as by-products. Thus, this study aimed to investigate the properties of proteins extracted from the safflower seed meal as food materials. The physicochemical properties and functional characteristics of safflower seed meal protein (SMP) were analyzed at different NaCl concentrations and pH. Results showed that the extraction rate of SMP is 55% and SMP contains 86% protein with an isoelectric point of 4.5. The molecular weight of proteins in SMP predominantly ranged from 10 to 43 kilodaltons (kDa), with a maximum weight loss temperature of 317 °C. Glutamic acid exhibited the highest, while lysine served as the primary limiting amino acid. All seven essential amino acids were present except for tryptophan, which was not included in the testing scope. Additionally, SMP exhibited its highest solubility (59.55%) and emulsifying capacity (62.63 m²/g) at pH 11, and its highest foaming capacity (70.67%) at pH 9. The highest solubility (41.56%) was observed at 1 mol/L NaCl; the highest emulsifying capacity (16.88 m²/g) was observed at 0.6 mol/L NaCl; and the highest foaming capacity (90.67%) was observed at 0.7 mol/L NaCl. This study demonstrates that SMP has excellent nutritional value and a variety of functional properties, making it a promising plant-based protein source for the food processing industry. Subsequent processing involving adjustment to a high pH and increased NaCl concentration can help SMP to exhibit its processing characteristics.