For a number of applications, gluten protein polymer structures are of the highest importance in determining end-use properties. The present article focuses on gluten protein structures in the wheat grain, genotype- and environment-related changes, protein structures in various applications, and their impact on quality. Protein structures in mature wheat grain or flour are strongly related to end-use properties, although influenced by genetic and environment interactions. Nitrogen availability during wheat development and genetically determined plant development rhythm are the most important parameters determining the gluten protein polymer structure, although temperature during plant development interacts with the impact of the mentioned parameters. Glutenin subunits are the main proteins incorporated in the gluten protein polymer in extracted wheat flour. During dough mixing, gliadins are also incorporated through disulfide-sulfhydryl exchange reactions. Gluten protein polymer size and complexity in the mature grain and changes during dough formation are important for breadmaking quality. When using the gluten proteins to produce plastics, additional proteins are incorporated in the polymer through disulfide-sulfhydryl exchange, sulfhydryl oxidation, β-eliminations with lanthionine formation, and isopeptide formation. In promising materials, the protein polymer structure is changed toward β-sheet structures of both intermolecular and extended type and a hexagonal close-packed structure is found. Increased understanding of gluten protein polymer structures is extremely important to improve functionality and end-use quality of wheat- and gluten-based products.
Systematic studies were performed on the effect of the surfactant alkyl chain length (10–16 carbon atoms) and the head group charge/structure (anionic, cationic, nonionic) on the pasting properties of wheat flour and starch aqueous suspensions by means of a Rapid Visco Analyser (RVA). An excellent agreement was observed between the effect of surfactants on the onset temperature of the pasting process (PT) and the time to reach peak viscosity (tpeak) of wheat flour and wheat starch suspensions. Moreover, a correlation was found between the effect of different surfactants on these two parameters. With the exception of the cationic surfactants (alkyl trimethyl ammonium bromides), the effect of surfactants (alkyl sulfates, maltosides, monoglycerides, and sucrose esters) was found to be strongly dependent on the surfactant chain length. Shorter chain surfactants (C10–C12) induced an earlier pasting, while longer chain surfactants (C14–C16) had the opposite effect. The effect of surfactants on PT and tpeak of flour suspensions was enlarged when the surfactant concentration was increased from !1% to 15% (w/w) on a dry starch basis.
The microstructure of ?-gel and ?-crystalline emulsifiers and their effects on cake batter foam have been studied with polarized light microscopy, confocal laser scanning microscopy (CLSM) and image analysis, freeze-etching, and transmission electron microscopy (TEM). The emulsifiers Colco and Aroplus, which are commercial ?-gels, and the monoglyceride Dimodan P in its ?-gel and ?-crystalline forms were added to the batter in concentrations of 0.8, 2.0, 3.1, and 4.2%. Dimodan P ?-gel was also prepared with three NaCl concentrations (0.05, 0.67, and 1.35%c). The distribution of air in the foam was evaluated with density measurements and with image analysis of bubbles in optically sectioned batter. In the cake batter, all the ?-gel emulsifiers decreased the density, thereby increasing the incorporation of air, more than the ?-crystalline emulsifier, which did not have any effect on the density. There were noticeable differences in microstructure between the different ?-crystalline emulsifiers. Large, regular ?-structures seemed to increase the batter volume and interfacial area more than smaller aggregates. Adding salt in the emulsifier gel changed the structure, probably into ?-lamellar liposomes, which impaired the aerating effect at lower concentrations.
A barley-soaking process was studied to find conditions that inactivate the prooxidative enzyme lipoxygenase and the lipolytic enzyme lipase but preserve phytase activity to develop possible procedures for production of barley products with potentially high mineral bioavailability and good oxidative stability. Lactic acid concentration, temperature, and soaking time were studied. The study was done using a multivariate experimental design. Lactic acid concentration varied between 0 and 1%, temperature varied between 45 and 70°C, and soaking time varied between 30 and 120 min. Although conditions under which lipoxygenase was inactivated were found, total inactivation of lipase was not obtained. Total lipoxygenase inactivation with <20% remaining lipase activity and >60% remaining phytase activity was reached after soaking in 1% lactic acid at suitable time-temperature combinations of 70-110 min and 53-58°C.
A steeping process of barley grains was evaluated regarding lipid oxidation. The steeping process was evaluated with respect to the temperature during the first steep and second steep, and the lactic acid concentration of the steep solutions. The study was conducted using a central composition circumscribed design, and response surface models were estimated with the use of partial least square. The change in the concentration of hexanal was used to monitor the oxidation during processing and subsequent storage at 30°C. In all samples there was hexanal development during processing and the hexanal concentration increased considerably during storage. The results show that it is possible to optimize the process to get a lower oxidation during the subsequent storage. The temperature during the second steep in the hydrothermal process and the level of lactic acid addition were the most important factors. Both of them should be kept low to favor the oxidative stability.