Oxidation of whey protein isolate after thermal convection and microwave heating and freeze-drying: Correlation among physicochemical and NIR spectroscopy analyses.

This study investigated the oxidative susceptibility of whey protein isolate (WPI) dispersions treated by microwave or thermal convection before freeze-drying. WPI (20 mg protein/mL) in distilled water (DW) was heated at 63 ± 2 °C for 30 min by microwave (WPI-MW) or convection heating (WPI-CH) and freeze-dried. Untreated WPI (WPI-C), WPI solubilized in DW and freeze-dried (WPI-FD), and WPI solubilized in DW, heated at 98 ± 2 °C for 2 min and freeze-dried (WPI-B) were also evaluated. Structural changes (turbidity, ζ potential, SDS-PAGE, and near-infrared spectroscopy (NIR)) and protein oxidation (dityrosine, protein carbonylation, and SH groups) were investigated. WPI-FD showed alterations compared to WPI-C, mainly concerning carbonyl groups. Microwave heating increased carbonyl groups and dityrosine formation compared to conventional heating. NIR spectrum indicated changes related to the formation of carbonyl groups and PCA analysis allowed us to distinguish the samples according to carbonyl group content. The results suggest that NIR may contribute to monitoring oxidative changes in proteins resulting from processing.

Peptide-metal complexes: obtention and role in increasing bioavailability and decreasing the pro-oxidant effect of minerals.

Bioactive peptides derived from food protein sources have been widely studied in the last years, and scientific researchers have been proving their role in human health, beyond their nutritional value. Several bioactivities have been attributed to these peptides, such as immunomodulatory, antimicrobial, antioxidant, antihypertensive, and opioid. Among them, metal-binding capacity has gained prominence. Mineral chelating peptides have shown potential to be applied in food products so as to decrease mineral deficiencies since peptide-metal complexes could enhance their bioavailability. Furthermore, many studies have been investigating their potential to decrease the Fe pro-oxidant effect by forming a stable structure with the metal and avoiding its interaction with other food constituents. These complexes can be formed during gastrointestinal digestion or can be synthesized prior to intake, with the aim to protect the mineral through the gastrointestinal tract. This review addresses: (i) the amino acid residues for metal-binding peptides and their main protein sources, (ii) peptide-metal complexation prior to or during gastrointestinal digestion, (iii) the function of metal (especially Fe, Ca, and Zn)-binding peptides on the metal bioavailability and (iv) their reactivity and possible pro-oxidant and side effects.

Whey Peptide-Iron Complexes Increase the Oxidative Stability of Oil-in-Water Emulsions in Comparison to Iron Salts.

Food fortification with iron may favor lipid oxidation in both food matrices and the human body. This study aimed at evaluating the effect of peptide-iron complexation on lipid oxidation catalyzed by iron, using oil-in-water (O/W) emulsions as a model system. The extent of lipid oxidation of emulsions containing iron salts (FeSO4 or FeCl2) or iron complexes (peptide-iron complexes or ferrous bisglycinate) was evaluated during 7 days, measured as primary (peroxide value) and secondary products (TBARS and volatile compounds). Both salts catalyzed lipid oxidation, leading to peroxide values 2.6- to 4.6-fold higher than the values found for the peptide-iron complexes. The addition of the peptide-iron complexes resulted in the formation of lower amounts of secondary volatiles of lipid oxidation (up to 78-fold) than those of iron salts, possibly due to the antioxidant activity of the peptides and their capacity to keep iron apart from the lipid phase, since the iron atom is coordinated and takes part in a stable structure. The peptide-iron complexes showed potential to reduce the undesirable sensory changes in food products and to decrease the side effects related to free iron and the lipid damage of cell membranes in the organism, due to the lower reactivity of iron in the complexed form.

Synthesis of whey peptide-iron complexes: Influence of using different iron precursor compounds.

Iron-binding peptides are an alternative for increasing the bioavailability of iron and to decreasing its pro-oxidant effect. This study aimed to synthesize and characterize peptide-iron complexes using FeCl2 or FeSO4 as the iron precursor compounds. Whey protein isolate (WPI), WPI hydrolyzed with pancreatin, and its fractions obtained via ultrafiltration (cut-off 5kDa) were used as ligands. The fluorescence intensity of the ligands significantly decreased as the iron concentration increased as a result of metal coordination with the iron-binding sites, which may have led to changes in the microenvironment of tryptophan. For both iron precursor compounds, the primary iron-binding site was carboxylate groups, and the linkage occurred via a bidentate coordination mode with two vibrational modes assigned to the COOFe linkage. However, infrared spectroscopy and thermal analysis results showed that the dynamics of the interaction is different for the iron precursor. The iron source may be of great importance because it may impact iron absorption and the pro-oxidant effect of the mineral.

Influence of Protein-Phenolic Complex on the Antioxidant Capacity of Flaxseed (Linum usitatissimum L.) Products.

The impact of the naturally present phenolic compounds and/or proteins on the antioxidant capacity of flaxseed products (phenolic fraction, protein concentrates, and hydrolysates) before and after simulated gastrointestinal digestion was studied. For that, whole and phenolic reduced products were assessed. Four glycosylated phenolic compounds (secoisolariciresinol and ferulic, p-coumaric, and caffeic acids) were identified in flaxseed products. Phenolic fraction exerts the highest antioxidant capacity that increased by alkaline hydrolysis and by simulated gastrointestinal digestion. The action of Alcalase and digestive enzymes resulted in an increase of the antioxidant capacity of whole and phenolic reduced products. Principal component analysis showed that proteinaceous samples act as antioxidant is by H+ transfer, while those samples containing phenolic compounds exert their effects by both electron donation and H+ transfer mechanisms. Protein/peptide-phenolic complexation, confirmed by fluorescence spectra, exerted a positive effect on the antioxidant capacity, mainly in protein concentrates.

Stability and in vitro digestibility of emulsions containing lecithin and whey proteins.

The effect of pH and high-pressure homogenization on the properties of oil-in-water (O/W) emulsions stabilized by lecithin and/or whey proteins (WPI) was evaluated. For this purpose, emulsions were characterized by visual analysis, droplet size distribution, zeta potential, electrophoresis, rheological measurements and their response to in vitro digestion. Lecithin emulsions were stable even after 7 days of storage and WPI emulsions were unstable only at pH values close to the isoelectric point (pI) of proteins. Systems containing the mixture of lecithin and WPI showed high kinetic instability at pH 3, which was attributed to the electrostatic interaction between the emulsifiers oppositely charged at this pH value. At pH 5.5 and 7, the mixture led to reduction of the droplet size with enhanced emulsion stability compared to the systems with WPI or lecithin. The stability of WPI emulsions after the addition of lecithin, especially at pH 5.5, was associated with the increase of droplet surface charge density. The in vitro digestion evaluation showed that WPI emulsion was more stable against gastrointestinal conditions.

In search of a tolerance-induction strategy for cow's milk allergies: significant reduction of beta-lactoglobulin allergenicity via transglutaminase/cysteine polymerization.

OBJECTIVE: To explore the use of ß-lactoglobulin polymerized using microbial transglutaminase and heating to identify whether protein polymerization could reduce in vivo allergenicity and maintain in vitro and ex vivo immunoreactivity for use in tolerance-induction protocols. METHODS: Based on previous protocols applied in mice and children, we performed in vivo challenges (using a skin prick test) with native and polymerized ß-lactoglobulin in adult patients with an IgE-mediated allergy to plactoglobulin. In vitro humoral immunoreactivity was analyzed using immunoblotting. Cell-mediated immunoreactivity was analyzed using ex vivo challenges with native and polymerized ß-lactoglobulin and monitored by leukocyte adherence inhibition tests. RESULTS: The skin tests demonstrated that there was a significant reduction in immediate cutaneous reactivity after polymerization. Polymerization did not decrease the immunoblotting detection of s-IgE specific to ß-lactoglobulin. Cell-mediated immunoreactivity, as assessed by ex vivo challenges and leukocyte adherence inhibition tests, did not exhibit significant differences between leukocytes challenged with native versus polymerized ß-lactoglobulin. CONCLUSIONS: The polymerization of ß-lactoglobulin decreased in vivo allergenicity and did not decrease in vitro humoral or ex vivo cell-mediated immunoreactivity. Therefore, we conclude that inducing polymerization using transglutaminase represents a promising technique to produce suitable molecules for the purpose of designing oral/ sublingual tolerance induction protocols for the treatment of allergies.

In search of a tolerance-induction strategy for cow's milk allergies: significant reduction of beta-lactoglobulin allergenicity via transglutaminase/cysteine polymerization

OBJECTIVE: To explore the use of β-lactoglobulin polymerized using microbial transglutaminase and heating to identify whether protein polymerization could reduce in vivo allergenicity and maintain in vitro and ex vivo immunoreactivity for use in tolerance-induction protocols. METHODS: Based on previous protocols applied in mice and children, we performed in vivo challenges (using a skin prick test) with native and polymerized β-lactoglobulin in adult patients with an IgE-mediated allergy to plactoglobulin. In vitro humoral immunoreactivity was analyzed using immunoblotting. Cell-mediated immunoreactivity was analyzed using ex vivo challenges with native and polymerized β-lactoglobulin and monitored by leukocyte adherence inhibition tests. RESULTS: The skin tests demonstrated that there was a significant reduction in immediate cutaneous reactivity after polymerization. Polymerization did not decrease the immunoblotting detection of s-IgE specific to β-lactoglobulin. Cell-mediated immunoreactivity, as assessed by ex vivo challenges and leukocyte adherence inhibition tests, did not exhibit significant differences between leukocytes challenged with native versus polymerized β-lactoglobulin. CONCLUSIONS: The polymerization of β-lactoglobulin decreased in vivo allergenicity and did not decrease in vitro humoral or ex vivo cell-mediated immunoreactivity. Therefore, we conclude that inducing polymerization using transglutaminase represents a promising technique to produce suitable molecules for the purpose of designing oral/ sublingual tolerance induction protocols for the treatment of allergies.

Allergenicity of Bos d 5 in Children with Cow's Milk Allergy is Reduced by Transglutaminase Polymerization.

Background: Cow's milk allergy in pediatric patients is an unresolved issue. Among the proteins in milk, bovine whey beta-lactoglobulin (Bos d 5) is the most commonly allergenic. Allergenicity to native cow's milk proteins in humans is a well-studied issue, but very little is known about the allergenicity of cross-linked proteins found in bioprocessed dairy products. Objective: The objective of this study was to evaluate the allergenicity of polymerized bovine whey beta-lactoglobulin in symptomatic children diagnosed with IgE-mediated Bos d 5 hypersensitivity. Methods: Side-by-side skin prick tests with native and polymerized bovine whey beta-lactoglobulin were performed in 22 symptomatic children allergic to cow's milk with detectable specific IgE to Bos d 5 by CAP Systems Pharmacia. A matched control group tolerant to cow's milk and undetectable specific IgE to Bos d 5 was established for comparison. Wheal mean diameter was compared between the native and polymerized groups by paired t-tests. Results: The mean difference in wheal mean diameter observed between native versus polymerized bovine whey beta-lactoglobulin in the paired skin prick test of the allergic group was 2.27 mm (p=0.02; 95% CI 0.38-4.16). Conclusions: The skin prick test showed a significant reduction in the allergenicity of polymerized compared with native bovine whey beta-lactoglobulin in children with IgE-mediated Bos d 5 hypersensitivity.

Chemical composition and bile acid binding activity of products obtained from amaranth (Amaranthus cruentus) seeds.

Cardiovascular diseases are currently the greatest cause of mortality in the world, and dislipidemia is appearing as one of the most important risk factors. The binding of bile acids (BAs) has been hypothesized as a possible mechanism by which dietary fibers lower blood cholesterol levels. Besides the fibers, other components in the amaranth seeds may be related to this hypocholesterolemic effect. The objective of the present study was to evaluate the BA binding capacity of some products obtained from defatted amaranth flour (DAF) and from the amaranth protein concentrate (APC). The alkaline residue, rich in fibers (8.6%), presented the lowest binding activity for the BAs tested, with the exception of glycocholic acid. The DAF showed intermediary binding activity for all the BAs tested, although similar to that of the APC for deoxycholic acid, and to that of the amaranth protein hydrolysate (APH) for taurocholic acid. The DAF and APC showed binding activity for secondary bile acids toxic to the intestinal mucus. From the results, amaranth products were shown to have the ability to bind BAs, but it was not possible to affirm whether the main component responsible for this activity was the proteins, fibers or eventually some other non-evaluated component.

Evaluation of the hypotensive potential of bovine and porcine collagen hydrolysates.

Angiotensin-converting enzyme (ACE) inhibitory activity and antihypertensive activity of bovine and porcine collagen hydrolysates in spontaneously hypertensive rats (SHR) were investigated. The hydrolyzed collagens were subjected to ultrafiltration using membranes with cutoffs of 30-50 kDa (permeate P1), 5-8 kDa (permeate P2), or 1-2 kDa (permeate P3) in order to obtain products with a narrower range of molecular size. The hydrolyzed bovine and porcine collagens and their permeates showed low ACE inhibitory activity (50% inhibitory concentration [IC(50)] = 5.42-15.58 mg of protein/mL). However, after in vitro gastrointestinal digestion, a significant increase in the ACE inhibitory potency of the hydrolyzed collagens was observed (IC(50) = 0.97-4.02 mg of protein/mL). Permeates had a higher ACE inhibitory activity and hypotensive activity than non-ultrafiltered hydrolysates. The P1 permeate of bovine and porcine collagen and the P3 fraction of the porcine collagen hydrolysate exhibited the best antihypertensive activity in vivo, promoting a maximum reduction in blood pressure of 22 mm Hg, 21.33 mm Hg, and 21.33 mm Hg, respectively, while lisinopril promoted a maximum reduction of 51.00 mm Hg. These results suggest that the commercial collagen hydrolysates of bovine and porcine origin may be a potential source of bioactive peptides.

Influência das condições de secagem nas propriedades funcionais da Aphanothece microscopica Nageli cultivada no efluente da parbolização do arroz / Influence of drying conditions in the functional properties of Aphanothece microscopica Nageli cultivated in the rice parbolizing efluent

O objetivo deste trabalho foi caracterizar a solubilidade e a capacidade emulsificante da biomassa da cianobactéria Aphanothece microscopica Nageli em diferentes condições de secagem. Produziu-se a biomassa na água residuária do processo de parbolização do arroz, inoculando 100 mg.L de Aphanothece microscopica Nageli na fase exponencial de crescimento em reator cilíndrico de mistura completa, na ausência de luz, pH 8,0, 30ºC, razão C/N 50 e tempo de detenção hidráulica de 72 h. A biomassa foi separada do efluente por centrifugação e desidratada em secador descontínuo de bandejas nas condições de 40, 50 e 60ºC em espessuras de biomassa de 3, 5 e 7 mm. A solubilidade pritéica foi avaliada em pH 2, 3, 4, 6, 8, 9 e 10 e a capacidade emulsificante determinada em pH 7,0. Os resultados demonstraram que as maiores solubilidades protéicas ocorreram em pH 10, havendo incremento da capacidade emulsificante nas camadas de biomassa de 3 mm de espessura.

Influência da fonte lipídica da dieta na utilizaçäo de caseína e proteína de soja por ratos Wistar / Influence of dietary lipid on utilization of casein and soybean protein by Wistar rats

Estudou-se a influência das fontes lipídicas, óleo de soja e banha de porco, nas propriedades nutricionais de caseína e isolado protéico de soja, sob forma de dieta balanceada, com ratos Wistar, em termos de ganho de peso, quociente de eficiência alimentar e proteíca e índices aparentes de digestibilidade, valor biológico e utilizaçäo líquida da proteína. Verificou-se que, para uma mesma fonte protéica, a fonte lipídica näo influiu nesses índices de qualidade, mas ocorreu influência a comparar fontes protéicas diferentes. Assim, inferiu-se que a combinaçäo caseína e óleo de soja forneceu os melhores resultados e a combinaçäo isolado protéico de soja e óleo de soja, o pior desempenho. Entretanto, ao combinar-se o isolado protéico de soja com a banha de porco, o valor nutritivo da proteína de soja näo diferiu daquele da caseína