Inhibition of angiotensin I-converting enzyme by wheat gliadin hydrolysates

A tryptic gliadin hydrolysate was fractionated into peptide fractions, which were assigned to either the central domain (CD) or terminal domains (TD) of gliadins. The domains were expected to contain amino acid (AA) sequences which, when released from the parent protein, inhibit the angiotensin I-converting enzyme (ACE), which plays a key role in regulating blood pressure. A proline (Pro) poor TD related fraction, containing the smallest peptides, showed the highest ACE inhibitory activity (IC₅₀ = 0.33 mg/ml). Additional peptidases were selected based on their in silico predicted ability to release ACE inhibitory peptides. Further hydrolysis of the tryptic hydrolysate fractions with thermolysin, Clarex, Alcalase and Esperase increased ACE inhibitory activities. Immobilised Ni²⁺-ion affinity chromatography (IMAC) purification of a TD related peptide fraction obtained by sequential hydrolysis with trypsin and thermolysin yielded a fraction with an IC₅₀ value of 0.02 mg/ml. This IMAC fraction was enriched in histidine and hydrophobic AA (Pro, Val, Ile, Leu and Phe).     

Proteins of Amaranth (Amaranthus spp.), Buckwheat (Fagopyrum spp.), and Quinoa (Chenopodium spp.): A Food Science and Technology Perspective

There is currently much interest in the use of pseudocereals for developing nutritious food products. Amaranth, buckwheat, and quinoa are the 3 major pseudocereals in terms of world production. They contain high levels of starch, proteins, dietary fiber, minerals, vitamins, and other bioactives. Their proteins have well‐balanced amino acid compositions, are more sustainable than those from animal sources, and can be consumed by patients suffering from celiac disease. While pseudocereal proteins mainly consist of albumins and globulins, the predominant cereal proteins are prolamins and glutelins. We here discuss the structural properties, denaturation and aggregation behaviors, and solubility, as well as the foaming, emulsifying, and gelling properties of amaranth, buckwheat, and quinoa proteins. In addition, the technological impact of incorporating amaranth, buckwheat, and quinoa in bread, pasta, noodles, and cookies and strategies to affect the functionality of pseudocereal flour proteins are discussed. Literature concerning pseudocereal proteins is often inconsistent and contradictory, particularly in the methods used to obtain globulins and glutelins. Also, most studies on protein denaturation and techno‐functional properties have focused on isolates obtained by alkaline extraction and subsequent isoelectric precipitation at acidic pH, even if the outcome of such studies is not necessarily relevant for understanding the role of the native proteins in food processing. Finally, even though establishing in‐depth structure–function relationships seems challenging, it would undoubtedly be of major help in the design of tailor‐made pseudocereal foods.     

Wheat (Triticum aestivum L. and T. turgidum L. ssp. durum) Kernel Hardness: I. Current View on the Role of Puroindolines and Polar Lipids

Wheat hardness has major consequences for the entire wheat supply chain from breeders and millers over manufacturers to, finally, consumers of wheat‐based products. Indeed, differences in hardness among Triticum aestivum L. or between T. aestivum L. and T. turgidum L. ssp. durum wheat cultivars determine not only their milling properties, but also the properties of flour or semolina endosperm particles, their preferential use in cereal‐based applications, and the quality of the latter. Although the mechanism causing differences in wheat hardness has been subject of research more than once, it is still not completely understood. It is widely accepted that differences in wheat hardness originate from differences in the interaction between the starch granules and the endosperm protein matrix in the kernel. This interaction seems impacted by the presence of either puroindoline a and/or b, polar lipids on the starch granule surface, or by a combination of both. We focus here on wheat hardness and its relation to the presence of puroindolines and polar lipids. More in particular, the structure, properties, and genetics of puroindolines and their interactions with polar lipids are critically discussed as is their possible role in wheat hardness. We also address future research needs as well as the presence of puroindoline‐type proteins in other cereals.     

Wheat (Triticum aestivum L. and T. turgidum L. ssp. durum) Kernel Hardness: II. Implications for End‐Product Quality and Role of Puroindolines Therein

Wheat kernel hardness is a major quality characteristic used in classifying wheat cultivars. Differences in endosperm texture among Triticum aestivum L. or between T. aestivum and T. turgidum L. ssp. durum cultivars profoundly affect their milling behavior, the properties of the obtained flour or semolina particles, as well as the quality of products made thereof. It is now widely accepted that the presence, sequence polymorphism, or absence of the basic and cysteine‐rich puroindolines a and b are responsible for differences in endosperm texture. These proteins show features in vitro, including foaming and lipid‐binding properties, which provide them with a potential impact in the production of wheat‐based food products, where they may improve gas cell stabilization or modulate interactions between starch, proteins, and/or lipids. We here summarize the impact of wheat hardness on milling properties and bread, cookie, cake, and pasta quality and discuss the role of puroindolines therein.     

Defining the relationship between fetal Doppler indices,abdominal circumference and growth rate in severe fetal growth restriction using functional linear discriminant analysis

The relationship between Doppler measurements, size and growth rate in fetal growth restriction has not been defined. We used functional linear discriminant analysis (FLDA) to investigate these parameters taking account of the difficulties inherent in exploring relationships between repeated observations from a small number of cases. In 40 fetuses with severe growth restriction, serial abdominal circumference (AC), umbilical, middle cerebral artery (MCA) and ductus venosus Doppler pulsatility index measurements were recorded. In 11 singleton fetuses with normal growth, umbilical artery pulsatility index only was measured. Data were expressed as z-scores in relation to gestation and analysed longitudinally using FLDA. In severe growth restriction, the Spearman correlation coefficients between umbilical artery pulsatility index and AC z-score, MCA pulsatility index and AC z-score and ductus venosus pulsatility index z-score and AC z-score were, respectively: −0.36, p = 4.4 × 10⁻⁷; 0.70, p = 1.1 × 10⁻¹⁷ and −0.50, p = 8.1 × 10⁻⁴. No relationship was seen between Doppler parameters and growth rate. There was no relationship between umbilical artery pulsatility index and AC nor growth rate in normally grown fetuses. In severe fetal growth restriction, Doppler changes are related to absolute fetal AC size, not growth rate.     

Solid Acids as Heterogeneous Support for Primary Amino Acid‐Derived Diamines in Direct Asymmetric Aldol Reactions

We have achieved the non‐covalent immobilization of chiral primary amino acid‐derived diamines on organic and inorganic sulfonated solid acids through acid‐base interaction. With the commercial sulfonated fluoropolymer nafion® NR50 as support an optimal balance was found between activity and stereoselectivity of the supported catalyst in direct asymmetric aldol reactions of linear ketones and aromatic aldehydes. Under optimized conditions aldol products were obtained in high yields and with excellent enantioselectivities for the syn‐product (up to 98% ee). Furthermore, catalysis with the supported diamine was demonstrated to occur truly heterogeneously and the loaded nafion® NR50 beads could be reused several times. Ultimately, the immobilized catalyst/nafion® NR50 system was successfully implemented in a fixed‐bed reactor set‐up under continuous flow conditions.     

Foaming properties of tryptic gliadin hydrolysate peptide fractions

A tryptic gliadin hydrolysate was separated into central domain (CD) or terminal domain (TD) related peptide fractions. Whereas the initial foam volume (FV) of CD peptide fractions remained constant as a function of pH, FV of TD peptide fractions increased from acidic to alkaline pH. Foam stability (FS) of CD peptide fractions was maximal near neutral pH. For TD peptide fractions, one fraction showed maximal FS at strongly alkaline pH, while the other showed no clear maximal FS. CD related peptide foams contained higher levels of hydrophobic peptides than the respective solutions, while small differences were observed for TD peptide fractions. Peptide compositions of foams did not vary with pH, indicating that the foaming properties of gliadin peptides are mainly dictated by charges. As the pH dependent foaming properties of TD related peptides resemble best those of gliadin, it was concluded that the pH dependent foaming properties of gliadins are mainly determined by their TDs.     

Synthesis of sulphonated mesoporous phenolic resins and their application in esterification and asymmetric aldol reactions

Mesoporous phenolic resins were functionalized with sulphonic acid groups by four different types of sulphonation procedures: (i) direct sulphonation on the aromatic ring, (ii) alkyl sulphonation of the aromatic ring, and functionalizations of the phenolic hydroxyl surface by using an aryl silane, 2-(4-chlorosulphonylphenyl)ethyl trichlorosilane (iii) or a propyl silane, 3-mercaptopropyltrimethoxysilane (iv). The highest acidity loadings were obtained through direct sulphonation with fuming sulphuric acid (1.90 mmol H⁺ g⁻¹) or chlorosulphonic acid (1.31 mmol H⁺ g⁻¹) and these materials showed the highest conversion (97+ %) in Fischer esterification of acetic acid with propanol. However, the alkyl sulphonic groups, obtained through sulphonation procedure (ii) showed the highest stability in terms of maintenance of their acidity after use in consecutive catalytic runs or leaching treatments. This was demonstrated both through evaluation of the regenerated catalysts in a consecutive esterification run and during a leaching resistance test in aqueous medium. Moreover, the developed sulphonated mesoporous phenolic resins are presented as novel support for the non-covalent immobilization of an l-phenylalanine derived chiral diamine organocatalyst for asymmetric aldol reactions. The immobilization is established by an acid–base interaction between the sulphonic acid group and the amine function. The acidity and in particular the electronic withdrawing environment of the sulphonic acid groups influence enormously the catalytic performance of the non-covalent immobilized chiral diamine catalyst (aromatic > aliphatic).