Abstract
The utilization of industrial sunflower meal to produce protein-rich products for the food industry is an alternative approach for better and more efficient use of this agricultural by-product. Sunflower meal proteins possess specific functional properties, which however need improvement to broaden their potential as supplements for delivering high--quality products for human nutrition. The aim of the study is to evaluate the combined influence of low-degree pepsin hydrolysis and transglutaminase (TG) modification on industrial sunflower meal protein isolate functionality at pH=2 to 10. Three TG-modified pepsin hydrolysates with the degree of hydrolysis of 0.48, 0.71 and 1.72% were produced and named TG-PH1, TG-PH2 and TG-PH3, respectively. All three TG-modified pepsin hydrolysates exhibited improved solubility at pH between 3.5 and 5.5 as the highest was observed of TG-PH3 at protein isoelectric point (pI=4.5). Sunflower meal protein isolate and TG-modified sunflower meal protein isolate had greater solubility than the three TG-modified hydrolysates at pH<3 and >7. Significant improvement of foam making capacity (p<0.05) was achieved with all three TG-modified pepsin hydrolysates in the entire pH area studied. Pepsin hydrolysis of the protein isolate with the three degrees of hydrolysis did not improve foam stability. Improved thermal stability was observed with TG-PH3 up to 80 °C compared to the protein isolate (pH=7). At 90 °C, TG modification of the protein isolate alone resulted in the highest thermal stability. Pepsin hydrolysis followed by a treatment with TG could be used to produce sunflower protein isolates with improved solubility, foam making capacity and thermal stability for use in the food industry.
Highlights
Sunflower is an economically important oil-bearing crop which is primarily used for production of vegetable oil
This study demonstrated the application of low-degree pepsin hydrolysis combined with transglutaminase (TG) treatment for the improvement of specific functional properties of a protein isolate prepared from industrial sunflower meal
The results implied that hydrolysis of the protein with pepsin decreased the influence of pH on protein solubility at isoelectric point
Summary
Sunflower is an economically important oil-bearing crop which is primarily used for production of vegetable oil. In 2012, sunflower oil production reached 15.22 million tonnes worldwide [1] and was further projected to increase due to enhanced consumer demand for trans-fat-free unsaturated fats [2] and its potential value as a feedstock for biodiesel generation [3]. Either for food or technical purposes, the oil extraction results in a substantial quantity of sunflower meal, which may reach up to 30 % of the initial amount of the used sunflower seeds [4]. This by-product is used as a protein source in the feed industry. The overproduction and accumulation of excessive amounts of unutilized sunflower meal causes higher storage or disposal expenses leading to overall decrease in net profit margin
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