An optimization approach for the production of fatlike protein isolates from different leguminous seeds using response surface methodology

Plant proteins are gaining increasing importance in the food industry and are isolated by extraction followed by precipitation. However, the yields obtained are often unsatisfactory, especially when isolating proteins for specific purposes. In this study, relevant processing parameters and different raw materials have been investigated systematically to obtain high yields of protein preparations with characteristic fatlike textural properties by salt-assisted extraction followed by dilution precipitation. A d-optimal design was used and analyzed by response surface methodology considering individual processing parameters (independent variables) and their influence on extraction and protein yield (dependent variables). The extraction parameters (pH value [5.0-6.5], NaCl concentration [0.0-1.0M], solid-to-solvent ratio [1:7-1:13]) and different raw materials (peas, lentils, white beans, faba beans, soybeans, full-fat und deoiled lupins) were investigated. Quadratic equations for the response variables were calculated and used to identify optimum protein extraction conditions for all raw materials used. The highest protein yields (38%) were calculated for full-fat lupins as the raw material extracted at pH5.0, a NaCl concentration of 0.6M and a solid-to-solvent ratio of 1:7. The protein yields of other grain legumes were considerably lower. Furthermore, the sensory profile of the lupin protein isolate showed unique creamy, smooth and fatlike characteristics. Practical ApplicationsPlant-based proteins, particularly protein isolates from grain legumes, are becoming increasingly important to industry as food ingredients due to their nutritional and functional properties. The major draw back of the specific protein isolation is the poor economic efficiency of the process and the low protein yields. Even though some processing parameters for protein isolation are well established, there is a lack of systematic studies on protein preparations with specific properties using different raw materials. In this study, the influence of key process parameters on the overall protein yields were investigated using pea, lentil, white bean, faba bean, soybean and lupin as raw materials. The findings will facilitate the choice of different leguminous seeds for the production of protein isolates and their potential use as fat replacers.