In vitro digestibility of proteins from historical and modern wheat cultivars.

BACKGROUND: Previous research has suggested that proteins and other quality parameters of wheats may have changed over a century of wheat breeding. These changes may affect protein digestibility. The in vitro protein digestibility of breads made with 21 cultivars of wheat introduced or released in the USA between 1870 and 2013 was therefore evaluated. RESULTS: Protein digestibility increased with release year, but was not normally distributed; three older cultivars had significantly lower digestibility than the other cultivars: 42.0 ± 0.3 mol% (primary amino N/total N) versus 34.7 ± 0.7 mol%; P < 0.001. High molecular weight (MW) protein fractions increased and low MW protein fractions decreased with release year, but these changes were not related to protein digestibility. Thus, other differences in protein composition or other flour components may contribute to diminished digestibility of the three older cultivars. CONCLUSIONS: This study identified differences in protein digestibility among wheat cultivars that may have important implications for human nutrition. Further investigation is required to determine the specific characteristics that differentiate high- and low-digestibility wheat cultivars. © 2020 Society of Chemical Industry.

Effect of extrusion on folic acid concentration and mineral element dialyzability in Great Northern beans (Phaseolus vulgaris L.).

Great Northern beans (GNB) contain appreciable magnesium (Mg), potassium (K), phosphorus (P), and iron (Fe), together with the heat-labile vitamin, folate, and the anti-nutritional compound phytate. Thus, the objective was to increase dialyzability of essential mineral elements while degrading phytate and minimizing destruction of folate through extrusion of GNB. Extrusion resulted in significant (p < 0.05) increases in dialyzability of Mg, P, K, and Fe by as much as 50%, 30%, 5%, and 79%, respectively, while decreasing cadmium (Cd) dialyzability. Screw speed (SS) had a significant quadratic effect on dialyzability of all elements. Low MC resulted in a significant reduction (46%) in phytate, although this was accompanied by as much as 24% destruction of folate. In conclusion, low barrel temperature, medium MC and high SS were identified as the optimum conditions to maximize essential mineral element dialyzability and folate retention while minimizing phytate and dialyzable Cd.

In Vitro Pepsin Digestibility of Cooked Proso Millet ( Panicum miliaceum L.) and Related Species from Around the World.

Thirty-three samples of proso millet ( Panicum miliaceum) with different countries of origin were screened for their pepsin digestibility after cooking to identify samples with high digestibility. The pepsin digestibility of all samples ranged from 26% to 57% (average 32%). There were no apparent differences in protein profiles (by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE) of samples with the lowest, intermediate, and highest digestibilities. However, liquid chromatographic-tandem mass spectrometric (LC-MS/MS) analysis revealed a negative correlation between pepsin digestibility and peptides that matched to high molecular weight proteins (24 kDa) from Panicum hallii with regions of contiguous hydrophobic amino acids. Low digestibility upon cooking was also observed for other species from the Panicum genus, such as little millet, switchgrass, and panicgrass, which suggests a unique inherent property of the genus. The results obtained from this study may form a basis for in-depth analysis of proso proteins that may help in developing new cultivars with higher digestibility upon cooking.

Effects of processing method and solute interactions on pepsin digestibility of cooked proso millet flour.

Previous studies have reported a substantial decline in in vitro digestibility of proso millet protein upon cooking. In this study, several processing techniques and cooking solutions were tested with the objective of preventing the loss in pepsin digestibility. Proso millet flour was subjected to the following processing techniques: high pressure processing (200 and 600 MPa for 5 and 20 min); germination (96 h); fermentation (48 h); roasting (dry heating); autoclaving (121 °C, 3 h), and treatment with transglutaminase (160 mg/g protein, 37 °C, 2 h). To study the interaction of millet proteins with solutes, millet flour was heated with sucrose (3-7 M); NaCl (2-6 M); and CaCl2 (0.5-3 M). All processing treatments failed to prevent the loss in pepsin digestibility except germination and treatment with transglutaminase, which resulted in 23 and 39% increases in digestibility upon cooking, respectively, when compared with unprocessed cooked flours. Heating in concentrated solutions of sucrose and NaCl were effective in preventing the loss in pepsin digestibility, an effect that was attributed to a reduction in water activity (aw). CaCl2 was also successful in preventing the loss in digestibility but its action was similar to chaotrops like urea. Thus, a combination of enzymatic modification and cooking of millet flour with either naturally low aw substances or edible sources of chaotropic ions may be useful in processing of proso millet for development of novel foods without loss in digestibility. However, more research is required to determine optimum processing conditions.

Nanoparticles prepared by proso millet protein as novel curcumin delivery system.

Encapsulation of lipophilic bioactive compounds using plant-derived proteins as delivery systems has received increasing interest. In this study, proso millet protein was extracted by either wet milling or 60% (v/v) aqueous ethanol and then used as the wall material to encapsulate curcumin. Millet protein was composed of prolamines that showed a significant difference in surface hydrophobicity depending on extraction procedure. The millet protein-curcumin nanoparticles were spherical with diameter around 250-350nm. The entrapment efficiency ranged from 11.2% to 78.9%, with millet protein extracted by ethanol showing better performance than that by wet milling process. The encapsulated curcumin exhibited a lower degradation rate than free curcumin at 60°C. The encapsulation showed no negative effect on the antioxidant activity of curcumin as assessed by the DPPH and ABTS assays. These results suggested that MP could be a promising encapsulant for the delivery of lipophilic compounds.

Heating Reduces Proso Millet Protein Digestibility via Formation of Hydrophobic Aggregates.

Proso millet protein has reported structural similarities with sorghum. In order to explore the potential of this crop as an alternative protein source for people with gluten sensitivity, in vitro protein digestibility was analyzed. Dehulled proso millet flour was subjected to various processing techniques (dry heating and wet heating). Regardless of the processing technique there was a significant decline in digestibility of protein in proso millet flour when compared with unprocessed flour (from 79.7 ± 0.8% to 42.0 ± 1.2%). Reduced digestibility persisted even when cooking with reducing agents. Heating in the presence of urea (8 M) and guanidine-HCl (4.5 M) prevented the reduction in observed digestibility (urea cooked 77.4 ± 0.8%; guanidine HCl cooked 84.3 ± 0.9%), suggesting formation of hydrophobic aggregates during heating in water. This was supported by an increase in surface hydrophobicity upon cooking. Thus, the proso millet protein, termed panicin, forms hydrophobic aggregates that are resistant to digestion when subjected to heat.

Effects of processing moisture on the physical properties and in vitro digestibility of starch and protein in extruded brown rice and pinto bean composite flours.

The influence of pinto bean flour and processing moisture on the physical properties and in vitro digestibility of rice-bean extrudates has been investigated. Brown rice: pinto bean flour (0%, 15%, 30%, and 45% bean flour) were extruded under 5 moisture conditions (17.2%, 18.1%, 18.3%, 19.5%, and 20.1%). Physical properties [bulk density, unit density, radial expansion, axial expansion, overall expansion, specific volume, hardness, color, water solubility index, and water absorption index] and in vitro starch and protein digestibilities were determined. Increasing bean flour and processing moisture increased density and hardness while decreasing expansion. Rapidly digestible starch decreased and resistant starch increased as bean substitution and processing moisture increased. In vitro protein digestibility increased with increasing bean flour or with decreasing processing moisture. Incorporating bean flour into extruded snacks can negatively affect physical attributes (hardness, density, and expansion) while positively affecting in vitro starch (decrease) and protein (increase) digestibilities.

Evaluation of nutritional, textural and particle size characteristics of dough and biscuits made from composite flours containing sprouted and malted ingredients.

Composite flours (CF) using cereals, legumes, millets, soy-protein isolate, dairy ingredient and fruit without refined flour were used for preparing multi-nutrient biscuits. Dough and biscuits were evaluated for physical, nutritional and textural properties, particle size, colour and sensory evaluation and compared against refined-flour biscuits (C). Effect of malting and sprouting on biscuit quality were also analyzed. The highest volume of particles for CF was 140 µm higher than C flour. CF biscuits had significantly (p ≤ 0.05) lower spread ratio and % weight loss compared to C. The hardness, stickiness and cohesiveness values of CF doughs were significantly (p ≤ 0.05) lower than C resulting in lower cutting strength and increased hardness of CF biscuits. Sprouting further decreased hardness of CF dough. Nutrient content of CF biscuits (sprouted and unsprouted) were significantly (p ≤ 0.05) higher than C biscuits. Sensory evaluation showed CF biscuits especially with sprouted flour had higher acceptability and were superior to C.