Effect of antinutrients on heat-set gelation of soy, pea, and rice protein isolates.

Plant-derived protein can present antinutrients (ANs) in its composition. The ANs can interact with the protein, affecting its solubility and functional properties, such as gelation. This work evaluated the effect of three ANs, namely phytic acid (PA), tannic acid (TA), and Quillaja bark saponin (QBS), on the gelation and solubility of soy (SPI), pea (PPI), and rice protein isolate (RPI). The ANs altered the protein isolates gelation and solubility. PA decreased the solubility and gelation of the three protein isolates at pH 3.0. The TA was the AN that most decreased the solubility and gelation characteristics of SPI and PPI at both pHs analyzed. QBS increased the gelation of SPI at pH 3.0 but decreased the final gel strength of RPI at the same pH. These results show that the knowledge of the presence of ANs in the protein isolates is of fundamental relevance for the processing of vegetable proteins.

Effect of phytic acid, tannic acid and saponin on asparagine-glucose Maillard reaction.

Antinutrients (ANs) interact with proteins changing its behavior and may affect Maillard reaction (MR). This work aimed to study the effect of phytic acid, tannic acid, and saponin on asparagine-glucose MR. The effect of AN concentration (0-1 mM) and reaction time (3-30 min at 150 °C) on the formation of melanoidins and acrylamide was determined. Other MR compounds were analyzed by gas chromatography and nuclear magnetic resonance. The ANs effect on asparagine-glucose thermal behavior was studied by differential scanning calorimetry. Results showed that ANs increase the melanoidins formation. Acrylamide content increased in saponin and phytic acid presence. The volatile profile was similar among the samples and formed mainly by pyrazines (>50%). ANs affect glucose's melting point, however, only phytic acid and saponin affect asparagine and glucose thermal behavior. The results presented in this work are important for food science and the industry to control MR in processed foods.

Quillaja bark saponin effects on Kluyveromyces lactis ß-galactosidase activity and structure.

Saponins are known for their bioactive and surfactant properties, showing applicability to the food, cosmetic and pharmaceutical industries. This work evaluated the saponins effects on Kluyveromyces lactis ß-galactosidase activity and correlated these changes to the protein structure. Enzyme kinetic was evaluated by catalytic assay, protein structure was studied by circular dichroism and fluorescence, and isothermal titration calorimetry was used to evaluate the interactions forces. In vitro enzymatic activity assays indicated an increase in the protein activity due to the saponin-protein interaction. Circular dichroism shows that saponin changes the ß-galactosidase secondary structure, favoring its protein-substrate interaction. Besides, changes in protein microenvironment due to the presence of saponin was observed by fluorescence spectroscopy. Isothermal titration calorimetry analyses suggested that saponins increased the affinity of ß-galactosidase with the artificial substrate o-nitrophenyl-ß-galactoside. The increase in the enzyme activity by saponins, demonstrated here, is important to new products development in food, cosmetic, and pharmaceutical industries.

Effect of divalent cations on bovine serum albumin (BSA) and tannic acid interaction and its influence on turbidity and in vitro protein digestibility.

Tannins, proteins, and divalent cations interactions are important for many processes in the food industry and human and animal nutrition and health. The effect of magnesium, calcium, and manganese on the interaction, turbidity, and in vitro protein digestibility of bovine serum albumin and tannic acid complexes was studied. The divalent cations increase the affinity and influence the enthalpy and entropy changes of the protein and tannin binding. Magnesium maintained the nature of interactions, and calcium and manganese changed the binding mechanism. The factor that most influenced turbidity was the tannic acid and divalent cations binary interaction. Samples containing tannic acid and magnesium and calcium decreased the protein digestibility. Manganese increased the in vitro protein digestibility when compared with samples without salt addition; nevertheless, the complexes formed was higher. These finds can help in the understanding of interactions involved food system and in physiological conditions.

Effect of tannic acid on the structure and activity of Kluyveromyces lactis ß-galactosidase.

Tannins are compounds with antinutrient properties that hinder food digestibility, prejudicing human and animal nutrition. This work aimed to evaluate the negative effects of tannic acid on Kluyveromyces lactis ß-galactosidase catalytic activity and correlate these changes with the protein structure. ß-Galactosidase activity decreased in the presence of tannins, which caused changes to the structure of the enzyme, as demonstrated by circular dichroism. It was verified that tannin binds to the protein by a static mechanism. Additionally, isothermal titration calorimetry suggested that tannic acid modified the molecular interaction between ß-galactosidase and o-nitrophenyl-ß-d-galactoside, reducing their affinity and prejudicing the protein activity. This study helps to understand the effects of tannins on the ß-galactosidase structure and how they are related to the enzyme catalytic activity. The alterations in the conformation and activity of the enzyme should be taken into consideration when dairy products are consumed with tannin-rich food.

Influence of Ternary Complexation between Bovine Serum Albumin, Sodium Phytate, and Divalent Salts on Turbidity and In Vitro Digestibility of Protein.

Phytate decreases mineral and protein availability and influences protein properties, such as solubility and stability. The binding constants and turbidity data can help with the understanding of the influence of phytate and divalent salts on protein behavior. Ternary complexes formed between bovine serum albumin, sodium phytate, and divalent salts were investigated by isothermal titration calorimetry, turbidity, and in vitro protein digestibility. Results showed a positive entropy change and a negative and small enthalpy change as a result of electrostatic binding forces and ternary and binary complex precipitation. The interaction was favored for the systems containing calcium and manganese, whereas those containing magnesium showed a low heat of interaction. Despite the high protein digestibility, the stability of divalent phytates in a wide pH range may decrease mineral bioavailability. These results can provide important insights for the study of mineral bioavailability and diverse processes that involve protein and minerals in several areas of knowledge.

Effect of heating and ionic strength on the interaction of bovine serum albumin and the antinutrients tannic and phytic acids, and its influence on in vitro protein digestibility.

Bioavailability of food nutrients can be reduced in the presence of antinutrients such as phytates and tannins. This work aimed to study bovine serum albumin binding to phytic acid and tannic acid, and its influence on in vitro protein digestibility. The effect of autoclaving and boiling on protein digestibility and the microstructure of complexes was also evaluated. Results showed that high ionic strength promotes greater affinity between tannic acid and bovine serum albumin, and decreases in vitro protein digestibility. For phytic acid and bovine serum albumin, the opposite behavior is observed because interactions are governed by electrostatic forces. A rise in temperature above that causing denaturation of the protein favors its interaction with phytic acid, and disfavors that with tannic acid, probably due to different protein binding site exposure. For both antinutrients, heating treatment increased protein hydrolysis, the size of complexes and their fragility.

Determination of heat-set gelation capacity of a quinoa protein isolate (Chenopodium quinoa) by dynamic oscillatory rheological analysis.

This work aimed to study the influence of pH (3.5 and 7.0) and CaCl2 and MgCl2 addition on heat-set gelation of a quinoa protein isolate at 10% and 15% (w/w). The protein isolate obtained was composed mainly of 11S globulin as was observed by electrophoresis and mass spectrometry analysis. Heat-set gelation occurred at both pH values studied. Nevertheless, the gels formed at pH 3.5 were more viscoelastic and denser than those formed at pH 7.0, that was coarser and presented syneresis. The CaCl2 and MgCl2 addition increased the gel strength during rheological analysis at pH 3.5, possibly due to the formation of fiber-like connections in the gel network. At pH 7.0, the divalent salts resulted in weaker gels formed by agglomerates, suggesting a neutralization of the protein surface charges. The differences in quinoa protein gelation were attributed to solubility, and the flexibility of proteins secondary structure at the pH studied.