Effect of sorghum flour addition on resistant starch content, phenolic profile and antioxidant capacity of durum wheat pasta

Foods containing elevated levels of health functional components such as resistant starch and polyphenolic antioxidants may have beneficial effects on human health. Pasta incorporating either red sorghum flour (RSF) or white sorghum flour (WSF) each at 20%, 30% and 40% substitution of durum wheat semolina (DWS) was prepared and compared to pasta made from 100% DWS (control) for content of starch fractions, phenolic profile and antioxidant capacity, before and after cooking. Total, digestible and resistant starch contents were determined by the AOAC method; individual phenolic acids and anthocyanins by reverse phase-HPLC analysis; total phenolic content by the Folin–Ciocalteu method and antioxidant capacity by the ABTS assay. The addition of both RSF and WSF increased the resistant starch content, bound phenolic acids, total phenolic content and antioxidant capacity at all incorporation levels compared to the control pasta; while free phenolic acids and anthocyanins were higher in the RSF-containing pasta only. Cooking did not change the resistant starch content of any of the pasta formulations. Cooking did however decrease the free phenolic acids, anthocyanins, total phenolic content and antioxidant capacity and increased the bound phenolic acids of the sorghum-containing pastas. The study suggests that these sorghum flours may be very useful for the preparation of pasta with increased levels of resistant starch and polyphenolic antioxidants.

Effect of sorghum flour addition on in vitro starch digestibility, cooking quality and consumer acceptability of durum wheat pasta

Whole grain sorghum is a valuable source of resistant starch and polyphenolic antioxidants and its addition into staple food like pasta may reduce the starch digestibility. However, incorporating nondurum wheat materials into pasta provides a challenge in terms of maintaining cooking quality and consumer acceptability. Pasta was prepared from 100% durum wheat semolina (DWS) as control or by replacing DWS with either wholegrain red sorghum flour (RSF) or white sorghum flour (WSF) each at 20%, 30%, and 40% incorporation levels, following a laboratory-scale procedure. Pasta samples were evaluated for proximate composition, in vitro starch digestibility, cooking quality, and consumer acceptability. The addition of both RSF and WSF lowered the extent of in vitro starch digestion at all substitution levels compared to the control pasta. The rapidly digestible starch was lowered in all the sorghum-containing pastas compared to the control pasta. Neither RSF or WSF addition affected the pasta quality attributes (water absorption, swelling index, dry matter, adhesiveness, cohesiveness, and springiness), except color and hardness which were negatively affected. Consumer sensory results indicated that pasta samples containing 20% and 30% RSF or WSF had acceptable palatability based on meeting one or both of the preset acceptability criteria. It is concluded that the addition of wholegrain sorghum flour to pasta at 30% incorporation level is possible to reduce starch digestibility, while maintaining adequate cooking quality and consumer acceptability.

Acute effect of sorghum flour-containing pasta on plasma total polyphenols, antioxidant capacity and oxidative stress markers in healthy subjects: a randomised controlled trial

SUMMARY
Background & aims
It has been previously reported that pasta containing wholegrain sorghum flour exhibits high content of polyphenols and antioxidant capacity and hence might enhance antioxidant status and reduce markers of oxidative stress in vivo; however no clinical studies have yet been reported. Therefore, the present study assessed the effect of pasta containing red or white wholegrain sorghum flour on plasma total polyphenols, antioxidant capacity and oxidative stress markers in humans. The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN: 12612000324819).

Methods
In a randomised crossover design, healthy subjects (n = 20) consumed three test meals of control pasta (CP), 30% red sorghum pasta (RSP) or 30% white sorghum pasta (WSP), 1–2 wk apart. The test meals were consumed as breakfast after an overnight fast. Blood samples were obtained at fasting and 2 h after consumption and analysed for total polyphenols, antioxidant capacity, superoxide dismutase (SOD) activity, protein carbonyl and 8-isoprostanes.

Results
Compared to baseline, the 2 h post-prandial levels following the RSP meal of plasma polyphenols, antioxidant capacity and SOD activity were significantly (P < 0.001) higher while the protein carbonyl level was significantly lower (P = 0.035). Furthermore, net changes in polyphenols, antioxidant capacity and SOD activity were significantly (P < 0.001) higher while protein carbonyl were significantly (P = 0.035) lower following consumption of the RSP meal than the CP meal.

Conclusion
The results demonstrated that pasta containing red wholegrain sorghum flour enhanced antioxidant status and diminished marker of oxidative stress in healthy subjects.

Metabolic consequences of knocking out UGT85B1, the gene encoding the glucosyltransferase required for synthesis of dhurrin in Sorghum bicolor (L. Moench)

Many important food crops produce cyanogenic glucosides as natural defense compounds to protect against herbivory or pathogen attack. It has also been suggested that these nitrogen-based secondary metabolites act as storage reserves of nitrogen. In sorghum, three key genes, CYP79A1, CYP71E1 and UGT85B1, encode two Cytochrome P450s and a glycosyltransferase, respectively, the enzymes essential for synthesis of the cyanogenic glucoside dhurrin. Here, we report the use of targeted induced local lesions in genomes (TILLING) to identify a line with a mutation resulting in a premature stop codon in the N-terminal region of UGT85B1. Plants homozygous for this mutation do not produce dhurrin and are designated tcd2 (totally cyanide deficient 2) mutants. They have reduced vigor, being dwarfed, with poor root development and low fertility. Analysis using liquid chromatography-mass spectrometry (LC-MS) shows that tcd2 mutants accumulate numerous dhurrin pathway-derived metabolites, some of which are similar to those observed in transgenic Arabidopsis expressing the CYP79A1 and CYP71E1 genes. Our results demonstrate that UGT85B1 is essential for formation of dhurrin in sorghum with no co-expressed endogenous UDP-glucosyltransferases able to replace it. The tcd2 mutant suffers from self-intoxication because sorghum does not have a feedback mechanism to inhibit the initial steps of dhurrin biosynthesis when the glucosyltransferase activity required to complete the synthesis of dhurrin is lacking. The LC-MS analyses also revealed the presence of metabolites in the tcd2 mutant which have been suggested to be derived from dhurrin via endogenous pathways for nitrogen recovery, thus indicating which enzymes may be involved in such pathways.

Effect of feeding systems on omega-3 fatty acids, conjugated linoleic acid and trans fatty acids in Australian beef cuts: potential impact on humnan health

The influence of feeding systems on the levels of functional lipids and other fatty acid concentrations in Australian beef was examined. Rump, strip loin and blade cuts obtained from grass feeding, short-term grain feeding (80 days; STGF) and long-term grain feedlot rations (150-200 days; LTFL) were used in the present study. The typical Australian feedlot ration contains more than 50% barley and/or sorghum and balanced with whole cottonseed and protein meals were used as feed for STGF and LTFL regimens. Meat cuts from 18 cattle for each feeding regimen were trimmed of visible fat and  connective tissue and then minced (300 g lean beef); replicate samples of 7g were used for fatty acid (FA) analysis. There was a significantly higher level of total omega-3 (n-3) and long chain n-3 FA in grass-fed beef (P <0.0001) than the grain-fed groups regardless of cut types. Cuts from STGF beef had significantly reduced levels of n-3 FA and conjugated linoleic acid (CLA) and similar levels of saturated, monounsaturated and n-6 FA compared with grass feeding (P <0.001). Cuts from LTFL beef had higher levels of saturated, monounsaturated, n-6 FA and trans 18:1 than similar  cuts from the other two groups (P <0.01), indicating that increased length of grain feeding was associated with more fat deposited in the carcass. There was a step-wise increase in trans 18:1 content from grass to STGF to LTGF, suggesting grain feeding elevates trans FA in beef, probably because of increased intake of 18:2n-6. Only grass-fed beef reached the target of more than 30mg of long chain n-3 FA/100 g muscle as recommended by Food Standard Australia and New Zealand for a food to be considered a source of omega- 3 fatty acids. The proportions of trans 18:1 and n-6 FA were higher (P<0.001) for both grain-fed beef groups than grass-fed beef. Data from the present study show that grain feeding decreases functional lipid  components (long chain n-3 FA and CLA) in Australian beef regardless of meat cuts, while increasing total trans 18:1 and saturated FA levels.