Quantitative and qualitative gradients in gluten protein composition are established during grain development. These gradients may be due to the origin of subaleurone cells, which unlike other starchy endosperm cells derive from the re-differentiation of aleurone cells, but could also result from the action of specific regulatory signals produced by the maternal tissue on specific domains of the gluten protein gene promoters.
The starchy endosperm is the major storage tissue in the mature wheat grain and exhibits quantitative and qualitative gradients in composition, with the outermost cell layers being rich in protein, mainly gliadins, and the inner cells being low in protein but enriched in high-molecular-weight (HMW) subunits of glutenin. We have used sequential pearling to produce flour fractions enriched in particular cell layers to determine the protein gradients in four different cultivars grown at two nitrogen levels. The results show that the steepness of the protein gradient is determined by both genetic and nutritional factors, with three high-protein breadmaking cultivars being more responsive to the N treatment than a low-protein cultivar suitable for livestock feed. Nitrogen also affected the relative abundances of the three main classes of wheat prolamins: the sulfur-poor ω-gliadins showed the greatest response to nitrogen and increased evenly across the grain; the HMW subunits also increased in response to nitrogen but proportionally more in the outer layers of the starchy endosperm than near the core, while the sulfur-rich prolamins showed the opposite trend.
The food consumption trends have long since shifted from demanding simple calories and essential nutrients in order to support the basic human body functions to demanding a balanced nutrition supply in order to achieve optimal health. Vitamins play a vital role in human health, yet are often lost or destroyed during food processing before they reach consumers, as they are highly prone to degradation by environmental factors. Microencapsulation technology is a technology aiming to protect sensitive compounds from environmental elements. It is widely used in pharmaceutical and cosmetic industries but its application in food production are few. This article reviews microencapsulation studies conducted in food with a specific focus on protecting vitamins from processing and stage losses. We found that although current technologies have the potential to create vitamin microcapsules, none could meet all the criteria for a successful product. To develop suitable vitamin microcapsules which are processing stable, digestible and safe to consume, we recommend further studies to focus on seeking and developing porous and thermal stable carbohydrate or protein based wall materials derived from natural food ingredients. Principles of microencapsulation technologies, selection of wall materials, and release mechanisms are reviewed. The impact of environmental factors on vitamin stability are complicated and not as established as commonly believed. Existing technologies cannot produce vitamin microcapsules that are processing stable, digestible and safe to consume, mainly due to the lack of thermal stable wall materials that are digestible. Further studies should focus on developing thermal stable carbohydrate or protein based wall materials derived from natural food ingredients. *Highlights (for review) *Manuscript Click here to view linked References Microencapsulation 29Microencapsulation is a process of encasing micron-sized materials in a polymeric shell. The 30 material to be encapsulated may be referred to as the internal phase, core material, fill, 31 payload phase or active agent, whilst the encapsulating material may be referred to as 32 membrane, carrier material, coating, shell, matrix, external phase or wall material (Zuidam & 33 Shimoni, 2010). The microcapsule implies core-wall structure and can be categorised as 34 reservoir and matrix systems. In the reservoir, the core is coated with the wall material, whilst 35 in a matrix system, the core material is embedded within a continuous network of the matrix 36 material lacking a distinctive external wall (Augustin & Hemar, 2009; Singh, Hemant, Ram, 37 & Shivakumar, 2010). The applied pressure can lead to the breakage of the reservoir capsules 38 and hence, the release of its contents. In a matrix type, the active agent is dispersed over the 39 carrier material either in the form of small droplets or more homogenously (Zuidam & 40 Shimoni, 2010). The capsules can be mononuclear where one core material is encapsulated 41 by a shell, or can be aggrega...
Increasing nitrogen supply can increase Fe and Zn concentrations in wheat grain, but the underlying mechanisms remain unclear. Size-exclusion chromatography coupled with inductively coupled plasma mass spectrometry was used to determine Fe and Zn speciation in the soluble extracts of grain pearling fractions of two wheat cultivars grown at two N rates (100 and 350 kg of N ha(-1)). Increasing N supply increased the concentrations of total Fe and Zn and the portions of Fe and Zn unextractable with a Tris-HCl buffer and decreased the concentrations of Tris-HCl-extractable (soluble) Fe and Zn. Within the soluble fraction, Fe and Zn bound to low molecular weight compounds, likely to be Fe-nicotianamine and Fe-deoxymugineic acid or Zn-nicotianamine, were decreased by 5-12% and 4-37%, respectively, by the high N treatment, whereas Fe and Zn bound to soluble high molecular weight or soluble phytate fractions were less affected. The positive effect of N on grain Fe and Zn concentrations was attributed to an increased sink in the grain, probably in the form of water-insoluble proteins.
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