Petya Ivanova¹, Vesela I. Chalova¹*, Hristo Kalaydzhiev¹, Mariana Perifanova-Nemska², Turid Rustad³
and Lidia Koleva¹

¹University of Food Technologies, Department of Biochemistry and Molecular Biology, 26 Maritsa Bulv., BG-4002 Plovdiv,
  Bulgaria
²University of Food Technologies, Department of Technology of Tobacco, Sugar, Vegetable and Essential Oils, 26 Maritsa
  Bulv., BG-4002 Plovdiv, Bulgaria
³Norwegian University of Science and Technology, Department of Biotechnology and Food Science, Sem Salandsvei 6/8,
  NO-7491 Trondheim, Norway

Article history:
Received: November 15, 2016
Accepted: May 4, 2017

Key words:
industrial sunflower meal, pepsin, protein hydrolysates, transglutaminase modification, functional properties

Summary:
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.

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