Bioactivity and functionality of chickpea protein-spent coffee phenolic complex

Abstract

The demand for alternative protein resources is growing by the day, due to factors such as rising population and changing environmental conditions. Plant-based proteins are one of the most beneficial protein sources to consider in this regard. However, since the functional and nutritional properties of plant-based proteins are inadequate to those of animal-based proteins, several modification applications are being explored in order to improve these properties. Protein interaction is one of the promising protein modification methods that have the potential to improve the bioactive properties of plant-protein resources. The interaction of chickpea protein with spent coffee phenolics was investigated in this study under two conditions interaction conditions including pH 7 and pH 9. The binding properties, the effect of the interaction on the structure and functional properties of the chickpea protein and the in vitro bioaccessibility properties of the complex were then investigated to characterize the effect of interaction on protein and phenolic compounds. Although chlorogenic acid was found in the extract, it was not found in the protein phenolic solution. Besides that, the amount of catechin in the protein phenolic interaction solution was lower than in the phenolic extract. Therefore, it was concluded that these two compounds were bound with chickpea protein. The effect of protein phenolic interaction on the functional properties of chickpea protein was investigated regarding protein solubility, foaming and emulsifying properties. There was no significant difference on the solubility of chickpea protein after its interaction with phenolic compounds. Similarly, there was no significant difference between foaming properties and emulsion capacity and stability of chickpea protein after at pH 7 (p>0.05). However, these properties of chickpea protein are enhanced at pH 9. The foaming capacity of chickpea protein was 43.33%, while the phenolic addition ranged from 123.33 to 142.89% with no significant difference between concentrations. Similarly, interaction at pH 9 increased the emulsion capacity and stability of chickpea protein by 10% and 8%, respectively. The emulsion activity index and stability index of the samples increased after both interactions. The CPI + PE 1 example showed the highest increase in chickpea protein. The determined increase was 55 % for the interaction at pH 9 and 47% for the interaction at pH 7, respectively. In the same examples, the emulsion stability indexes increased by 70% and 6%, respectively. In vitro bioavailability analysis was performed to examine the bioactive properties of protein phenolic solution and its stability during gastrointestinal digestion. The total phenolic content and antioxidant capacity of the samples were increased with the addition of phenolic extract. After intestinal digestion, the total phenolic content in covalent samples decreased, however, no statistically significant difference was observed after the interaction at pH 7. The total phenolic content of the samples interacted at pH 9 decreased after intestinal digestion, but there was no statistically significant difference the samples interacted at pH 7. The ABTS method indicated that, while total antioxidant capacity was reduced in the gastric phase, total antioxidant capacity was increased by up to 33% only after the interaction at pH 9 in the intestinal phase. Although there was little or no increase in total antioxidant capacity of the samples in the gastric phase, an increase in antioxidant capacity of up to 68 and 18 %, respectively, was observed in the intestinal phase after interaction at pH 7 and pH 9 with the addition of phenolic. Zeta potential, FTIR spectrum, and fluorescence intensity analyses were used to investigate the effect of the interaction on the structural properties of the chickpea protein. While the samples' absolute zeta potential was low after interaction at pH 9, the absolute zeta potential increased after interaction at pH 7. The FTIR spectrum of the analysis showed that there was a change in the secondary structure of the chickpea protein due to the change in the amide bands. Also, change in the tertiary structure was detected due to the change in the fluorescence intensity after both interaction conditions. Consequently, spent coffee ground phenolics were found to cause changes in protein structure as a result of interaction with chickpea protein. The functional properties of the chickpea protein have been improved as a result of these changes. It was concluded that phenolics from spent coffee grounds could be an effective alternative protein modification for chickpea protein.