Browsing by Subject "gelation"

The literature review focused on acid- and heat-induced protein gelation and the value of rice bran as a food ingredient. A protein-enriched rice bran fraction containing 24% protein, 24% fibre and 22% phytate was used in the experimental work. The aim was to investigate the effect of phytate on protein solubility and study the gelling ability and the effect of a phytate-degrading enzyme, phytase, and a crosslinking enzyme, transglutaminase, in heat- and acid-induced gelation. Phytase treatment of the protein-enriched rice bran fraction decreased the phytate content to 1%. As a result, protein solubility increased at pH 2 from 40 to 55% and at pH 4 from 40 to 47%. In addition, phytase treatment improved gel strength from 1100 to 8200 Pa and water holding capacity from 54.6% to 77.7% of heat-induced gels at pH 8. Acid-induced gelation resulted in low gel strength of 108–190 Pa and water holding capacity of 52.8–56.6%. Transglutaminase had limited crosslinking ability on the protein-enriched rice bran fraction and consequently acid induced gelation and final gel characteristics were not affected by transglutaminase treatment. Acid-induced gels showed fine and homogeneous microstructure, whereas heat induced gelation led to more dense protein and fibre network structure. Based on these results, the protein-enriched rice bran fraction has gelling ability upon heating and acidification. Phytase treatment had great technological potential in altering the protein solubility and heat-induced gelation ability of the fraction.

Previous studies have demonstrated that legume proteins have high potential to lose their native functional properties during conventional wet fractionation, since heating and drying in the processes can lead to protein aggregation and solubility reduction. However, the effect of this process on faba bean protein has not been investigated thoroughly before, according to the literature review. Therefore, the aim of this study was to investigate the influence of wet fractionation process with and without spray drying on faba bean protein gelling properties. The hypothesis was that protein isolate produced with isoelectric precipitation without spray drying would have better solubility and gelling properties than spray dried isolate. Faba bean protein concentrate (FBPC) was used to prepare faba bean protein isolate with alkaline extraction followed by isoelectric precipitation, which was then dispersed into water and neutralized (faba bean protein slurry, FBPS). Some of FBPS was spray-dried (pilot faba bean protein isolate, FBPI-P). Commercial faba bean protein isolate (FBPI-C) was used as a reference sample. Their (FBPC, FBPS, FBPI-P, FBPI-C) functionality was studied by measuring thermal denaturation (DSC), protein solubility, particle size and light microscope pictures. In addition, glucono delta lactone (GDL) induced oil-in-water emulsion gels were prepared from FBPS, FBPI-P and FBPI-C. Water holding capacity (WHC), rheological and texture properties were measured from the gel samples. Surprisingly the obtained results of faba bean in this study were different from previous research on other legume proteins. It was found that spray-dried FBPI-P showed better gelling properties than wet based FBPS. This might be due to differences in thermal denaturation. Based on DSC curves, FBPI-C was found to be fully denatured and in a poor solubility. Interestingly, GDL-induced gels had strongest gel properties, which might be highly related to industrial manufacturing process of FBPI-C. When considering the theoretical environmental impact of these processes, FBPS could show potential of being more environmentally friendly process, as it could be more energy efficient than processes which require drying and heating. It was demonstrated that FBPS showed almost as good functional properties as the pilot spray-dried isolate. Hence, FBPS could work as functional and more environmentally friendly option for food industry. Future study could be conducted in near future about FBPS safety, technological applications, process optimization and environmental impact.