Protein Digestibility of Cereal Products

Protein digestibility is currently a hot research topic and is of big interest to the food industry. Different scoring methods have been developed to describe protein quality. Cereal protein scores are typically low due to a suboptimal amino acid profile and low protein digestibility. Protein digestibility is a result of both external and internal factors. Examples of external factors are physical inaccessibility due to entrapment in e.g., intact cell structures and the presence of antinutritional factors. The main internal factors are the amino acid sequence of the proteins and protein folding and crosslinking. Processing of food is generally designed to increase the overall digestibility through affecting these external and internal factors. However, with proteins, processing may eventually also lead to a decrease in digestibility. In this review, protein digestion and digestibility are discussed with emphasis on the proteins of (pseudo)cereals

Protein nanoparticles to build food structure

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Peak Fitting Applied to Fourier Transform Infrared and Raman Spectroscopic Analysis of Proteins

FTIR and Raman spectroscopy are often used to investigate the secondary structure of proteins. Focus is then often laid on the different features that can be distinguished in the Amide I band (1600–1700 cm−1) and, to a lesser extent, the Amide II band (1510–1580 cm−1), signature regions for C=O stretching/N-H bending, and N-H bending/C-N stretching vibrations, respectively. Proper investigation of all hidden and overlapping features/peaks is a necessary step to achieve reliable analysis of FTIR and FT-Raman spectra of proteins. This paper discusses a method to identify, separate, and quantify the hidden peaks in the amide I band region of infrared and Raman spectra of four globular proteins in aqueous solution as well as hydrated zein and gluten proteins. The globular proteins studied, which differ widely in terms of their secondary structures, include immunoglobulin G, concanavalin A, lysozyme, and trypsin. Peak finding was done by analysis of the second derivative of the original spectra. Peak separation and quantification was achieved by curve fitting using the Voigt function. Structural data derived from the FT-Raman and FTIR analyses were compared to literature reports on protein structure. This manuscript proposes an accurate method to analyze protein secondary structure based on the amide I band in vibrational spectra

Anthocyanin Content of Crackers and Bread Made with Purple and Blue Wheat Varieties

Purple and blue wheats contain anthocyanins in the outer layers of the wheat kernel, and therefore purple and blue wholemeals can be a source of anthocyanins when developing processed cereal products. However, cereal processing is anticipated to cause significant anthocyanin losses. In this study, the anthocyanin content of crackers and bread made from one purple and three blue wholemeals was measured during processing and after baking. LC-MS/MS was used to confirm the presence of anthocyanins, and to tentatively identify them. Mixing and baking steps significantly decreased the anthocyanin content, whereas resting and fermentation steps did not. Purple and blue wholemeal samples reacted differently, indicating that the starting anthocyanin content, localization and composition may have some impact on anthocyanin retention. Additionally, dough systems with decreased pH were more protective of anthocyanins during intermediate processing steps, as were high-temperature, short-time baking procedures. This research provides insights into the processing steps that cause significant anthocyanin losses, and proposes some modifications to formulation and processing conditions which can further reduce losses

Biopolymer-based nanoparticles and microparticles: fabrication, characterization and application

© 2014 Elsevier Ltd. Tailor-made microparticles and nanoparticles are finding increasing use in food products to alter their nutritional characteristics, flavor profile, appearance, rheology, stability, and processability. These particles are often fabricated from food-grade biopolymers, such as proteins and polysaccharides. Food biopolymers display a diverse range of molecular and physicochemical properties (e.g. molecular weight, charge, branching, flexibility, polarity, and solubility) which enables the assembly of colloidal particles that exhibit a broad range of functional attributes. By careful selection of appropriate biopolymers and assembly methods, biopolymer particles can be fabricated with tailored behaviors or features. In this article, we review recent developments in the design and fabrication of functional biopolymer nanoparticles and microparticles, and highlight some of the challenges that will be the focus of future research.publisher: Elsevier articletitle: Biopolymer-based nanoparticles and microparticles: Fabrication, characterization, and application journaltitle: Current Opinion in Colloid & Interface Science articlelink: http://dx.doi.org/10.1016/j.cocis.2014.07.002 content_type: article copyright: Copyright © 2014 Elsevier Ltd. Published by Elsevier Ltd. All rights reserved.status: publishe

Emulsifying and emulsion stabilizing properties of gluten hydrolysates

Gluten is produced as a coproduct of the wheat starch isolation process. In this study, gluten was hydrolyzed to degrees of hydrolysis (DH) of 3-6-10 and 1-2-3 with alcalase and trypsin, respectively. These peptidases have a clearly distinct substrate specificity. Corn oil-in-water emulsions (10 wt % oil) were prepared by high-pressure homogenization at pH 7.5. Gluten peptides with DH 3 proved to be the most effective in producing peptides displaying emulsifying properties. Higher levels of alcalase hydrolysates (2.0 wt %) than of trypsin hydrolysates (1.0 wt %) were required to produce stable emulsions with small droplet sizes, which is attributed to differences in the nature of the peptides formed. The emulsions had small mean droplet diameters (d32 < 1000 nm). Emulsions produced with trypsin hydrolysates (stable after 9 days at 55 °C) displayed better thermal stability compared to those produced with alcalase hydrolysates (destabilized after 2 days at 37 °C). The hydrolysate-containing emulsions, however, were quickly destabilized by salt addition (≤100 mM NaCl) and when the pH approached the isoelectric point of the coated droplets (pH ~5.5). Microscopic analysis revealed the formation of air-in-oil-in-water emulsions at lower hydrolysate concentrations, whereas at higher concentrations (≥3.0 wt %) extensive flocculation occurred. Both phenomena contributed to creaming of the emulsions. These results may be useful for the utilization of gluten hydrolysates in food and beverage products.status: publishe

Food-grade strategies to increase stability of whey protein particles: Particle hardening through aldehyde treatment

Protein particles are promising systems for encapsulation purposes and structure building and stabilization in a food context (Arroyo-Maya & McClements, 2015; Oduse, Campbell, Lonchamp, & Euston, 2017). Whey protein isolate (WPI) nanoparticles can be easily produced using liquid antisolvent precipitation. An additional particle hardening step is however often required, since WPI particles tend to disintegrate in aqueous environment. In this study, the potential of different food-grade aldehydes (i.e., cinnamaldehyde, salicylaldehyde, syringaldehyde, vanillin and p-anisaldehyde) to stabilize the protein particle matrix was explored. In general, the largest increase in stability against disintegration was observed for vanillin-treated particles. Incubation with vanillin did not only improve particle stability in aqueous environment, but also during isothermal storage (T=6, 23 or 37 °C for 3 weeks) and thermal treatment (T≤80 °C for 30 min). Although less pronounced, an increased particle stability in aqueous environment was also observed after salicylaldehyde or syringaldehyde treatment. All particles however disintegrated at pH values far removed from their isoelectric point (IEP≈pH 4.9), while extensive aggregation was observed near the IEP and under variable salt concentrations (0–250mM NaCl). Vanillin treatment did not induce conformational changes or covalent bond formation within the particle matrix. Therefore, the observed hardening effect presumably results from non-covalent interactions between vanillin and protein molecules. The provided insights will serve as a basis to further optimize the stabilization of protein-based systems, with the eventual goal of increasing their application potential in the food industry.status: publishe

Understanding the behavior of wheat gliadin based nanoparti-cles upon adsorption at air-water interfaces

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