Effects of thermal and mechanical treatments on the physicochemical properties of wheat flour

Effect of transglutaminase on the structure, properties and oil absorption of wheat flour

The structure, properties, as well as the oil absorption characteristics of wheat flour (WF) treated with varying concentrations of transglutaminase (TG) (0 U/g ∼ 50 U/g) were characterized. The content of free amino groups in WF modified by TG (TG-WF) decreased and protein aggregated. The isopeptide bonds and disulfide bonds played important roles in protein crosslinking. The thermal stability, the peak viscosity after gelatinization and protein secondary structure stability of TG-WF were improved. In addition, the oil absorption and surface oil content of TG-WF after frying were reduced. TG enhanced the protein-protein interactions in WF, so that protein played barrier roles in the process of high-temperature frying, protecting the starch particles covered by them from the infiltration of oil, thus reducing the oil absorption of TG-WF during frying. Among them, the oil content of TG-WF-30 U/g after frying was the lowest, which decreased by 10.73 % compared with the control group.

Wheat milling across history altered sugar bioaccessibility assessed using TIM-1 in vitro digestion model

The differences in wheat flour characteristics caused by ancient (pestle and mortar), old (stone hand mill), and modern (roller and cyclone) milling techniques and their effect on in vitro starch digestibility of wheat porridge using the simulated TIM Gastrointestinal Model (TIM-1) were investigated. Ancient flour (AF) was the coarsest flour (∼70 % is >1000 µm), followed by old wholemeal flour (OWF) and old refined flour (ORF) with similar particle size distribution showing one prominent peak (at ∼1000 µm for OWF and ∼800 µm for ORF). Modern refined flour (MRF) had a monomodal distribution centered at a particle size of ∼100 μm, while modern wholemeal flour (MWF) particle size was distributed between 40 and 600 μm. MRF and MWF porridges had higher cumulative sugar bioaccessibility than OWF and AF porridges, with ORF porridge having an intermediate cumulative sugar bioaccessibility. Characterizing the cumulative sugar bioaccessibility profile with a shifted logistic model allows identifying that the maximum sugar bioaccessibility and rate of sugar release were significantly higher (p < 0.05) for MRF and MWF compared to OWF and AF porridges, while the induction times were shorter, demonstrating the importance of processing on modulating starch digestibility.

Nonthermal physical modification of starch: An overview of recent research into structure and property alterations

To tailor the properties and enhance the applicability of starch, various ways of starch modification have been practiced. Among them, physical modification methods (micronization, nonthermal plasma, high-pressure, ultrasonication, pulsed electric field, and γ-irradiation) are highly potential for starch modification considering its safety, environmentally friendliness, and cost-effectiveness, without generating chemical wastes. Thus, this article provides an overview of the recent advances in nonthermal physical modification of starch and summarizes the resulting changes in the multi-level structures and physicochemical properties. While the effect of these techniques highly depends on starch type and treatment condition, they generally lead to the destruction of starch granules, the degradation of molecules, decreases in crystallinity, gelatinization temperatures, and viscosity, increases in solubility and swelling power, and an increase or decrease in digestibility, to different extents. The advantages and shortcomings of these techniques in starch processing are compared, and the knowledge gap in this area is commented on.

Effects of thermal properties and behavior of wheat starch and gluten on their interaction: A review

Starch and gluten, the most important macromolecules in wheat flour, vary in thermal properties. The thermal behavior of starch, gluten and their complexes during the manufacture and quality control of flour products need to be accurately understood. However, the high complexity of starch-gluten systems impedes the accurate description of their interactions. When heated within varying temperature ranges and when water molecules are involved, the behaviors of amylose and amylopectin change, and the properties of the starch are modified. Moreover, important indicators of starch granules such as gelatinization temperature, peak viscosity, and so on, which are encapsulated by the gluten matrix, are altered. Meanwhile, the high-temperature environment induces the opening of the intrachain disulfide bonds of gliadin, leading to an increase in the probability of interchain disulfide bond formation in the gluten network system. These behaviors are notable and may provide insights into this complex interaction. In this review, the relationship between the thermal behavior of wheat starch and gluten and the quality of flour products is analyzed. Several methods used to investigate the thermal characteristics of wheat and its flour products are summarized, and some thermal interaction models of starch and gluten are proposed.

Quantitative Analyses of Key Odorants and Their Precursors Reveal Differences in the Aroma of Gluten-Free Rice Bread and Wheat Bread

Rice flour is one of the most important raw materials in gluten-free products. However, the aroma of gluten-free rice bread is less accepted by consumers than that of commercial wheat bread. Therefore, 18 selected aroma compounds were determined in rice and wheat breads by stable isotope dilution assays (SIDA) to elucidate differences in the sensory characteristics, concentrations, and odor activity values (OAVs). The OAVs of most aroma compounds varied greatly between a rice and a wheat bread. In particular, 2-aminoacetophenone with a grape-like, medicinal aroma was characteristic for rice bread crumb and crust, while maltol was only relevant in wheat bread crust. Ehrlich pathway products varied in their concentration between the bread crumbs and were correlated with the contents of their corresponding free amino acid precursors in the flours and doughs. The analysis of rice flour revealed that only a few aroma compounds were retained in the bread. Consequently, the bread making process has a high relevance in aroma compound formation. In a comparison of breads prepared from fresh and stored rice flour, hexanal was identified as an important indicator for aging in rice bread and flour.