Phenolics,fibre and fibre digestibility in the crop residue from bird resistant and non-bird resistant sorghum varieties

The relationship between phenolics and parameters of in-vitro digestibility of neutral-detergent fibre (NDF) in leaves and stems from the crop residue of bird resistant (BR) and non-bird resistant (NBR) sorghum varieties was determined. The phenolics studied were lignin, insoluble proanthocyanidins, soluble red pigments and soluble phenolics as measured by absorbance (280 nm)and precipitation with ytterbium. Parameters of the digestibility of NDF studied were 48-h digestibility, potentially digestible NDF, rate of digestion and indigestible NDF as determined by non-linear regression analysis. Leaves from BR varieties were higher in most phenolics than leaves from NBR varieties. Digestibility of NDF at 48 h, potentially digestible NDF and rate of NDF digestion was lower in leaves from BR varieties. The indigestible NDF was higher in BR varieties. Phenolics in leaves were negatively correlated with digestibility of NDF at 48 h, potentially digestible NDF and rate of NDF digestion and positively correlated with indigestible NDF. Phenolics in stems had non-significant correlations with parameters of the digestibility of NDF except for a positive correlation between lignin and indigestible NDF. These results indicate that breeding for bird resistance in sorghum would lead to lower nutritive value of the crop residue.     

Biochemical profiling of Pakistani sorghum and millet varieties with special reference to anthocyanins and condensed tannins

Cereals like sorghum and millet are splendid sources of phenolics, dependent on their genetic makeup, and possess varied levels of flavonoids, flavanols, flavanones, anthocyanins, and condensed tannins. In this study, chemical composition and anthocyanin and tannin content of seven sorghum and two millet varieties were evaluated. American Association of Cereal Chemists (AACC) respective methods were used for chemical composition. Anthocyanins were determined through HPLC/UV-Vis, while condensed tannins were determined spectrophotometrically. Four anthocyanins determined included apigeninidin, kuromanin, pelargonidin, and cyanidin. Among sorghum varieties, JS-263 had the highest apigeninidin (16 µg/g). Other anthocyanins were not found in appreciable quantities. None of the anthocyanins were detected in millet varieties. Condensed tannins were highest in sorghum variety PC-1 (179.76 mg/100g) and millet variety S. Bajra-2011 (172.75 mg/100g). Two varieties, one each from sorghum and millet, were selected for extraction of bran as a separate fraction. Brans were modified by size reduction and enzymatic treatment (xylanase and cellulase). Enzymatic treatment favorably affected the extraction of phenolic compounds like anthocyanins. Sorghum and millet flour- and bran-supplemented breads were also developed and evaluated for sensory acceptability.     

New Highly Stable Dimeric 3‐Deoxyanthocyanidin Pigments from Sorghum bicolor Leaf Sheath

Abstract: The growing interest in natural alternatives to synthetic petroleum‐based dyes for food applications necessitates looking at nontraditional sources of natural colors. Certain sorghum varieties accumulate large amounts of poorly characterized pigments in their nongrain tissue. We used High Performance Liquid Chromatography‐Tandem Mass Spectroscopy to characterize sorghum leaf sheath pigments and measured the stability of isolated pigments in the presence of bisulfite at pH 1.0 to 7.0 over a 4‐wk period. Two new 3‐deoxyanthocyanidin compounds were identified: apigeninidin‐flavene dimer and apigenin‐7‐O‐methylflavene dimer. The dimeric molecules had near identical UV‐Vis absorbance profiles at pH 1.0 to 7.0, with no obvious sign of chalcone or quinoidal base formation even at the neutral pH, indicating unusually strong resistance to hydrophilic attack. The dimeric 3‐deoxyanthocyanidins were also highly resistant to nucleophilic attack by SO₂; for example, apigeninidin‐flavene dimer lost less than 20% of absorbance, compared to apigeninidin monomer, which lost more than 80% of absorbance at λ_max within 1 h in the presence of SO₂. The increased molecular complexity of the dimeric 3‐deoxyanthocyanidins compared to their monomers may be responsible for their unusual stability in the presence of bisulfite; these compounds present new interesting opportunities for food applications. Practical Application: Natural dimeric pigments concentrated in sorghum sheath retain their hue properties and stability over a wide pH range and should be explored for potential use in mildly acidic to neutral food applications.     

Phenolic composition and antioxidant activity of culms and sugarcane (Saccharum officinarum L.) products

The present work reports amounts of flavonoids and phenylpropanoids of culms of three sugarcane varieties and of raw juice, syrup, molasse and VHP sugar. The antioxidant activity of those materials was evaluated by the DPPH and β-carotene/linoleic acid methods. The predominant phenolics in culms were phenylpropanoids (caffeic, chlorogenic and coumaric acids), while flavones (apigenin, tricin and luteolin derivatives) appeared in lower amounts. Differences were noted either among phenolic profiles of sugarcane culms or between culms and sugarcane products. The antioxidant activities of solutions from most samples were similar or higher than a 80 μM Trolox solution.     

Structure and digestibility of tissues in normal and brown midrib pearl millet (Pennisetum glaucum)

The tissues in leaf blades, midribs, sheaths and stems of normal (N), 5848, and two brown midrib (bmr) mutants, 5753 and 5778, of pearl millet (Pennisetum glaucum (L) R Br) were examined for structural characteristics related to digestibility. The anatomies of the various plant parts were not substantially different between N and bmr plants. The more rigid, lignified tissues such as vascular bundles in all plant parts and the rind of stems were not digested after incubation for 7 days in N or bmr plants, indicating that modifications in these tissues were not sufficient to affect biodegradation. Modifications in the digestible tissues resulted in faster and more extensive degradation in bmr plants, and these changes appear to be the most significant in relation to biodegradation. The parenchyma of midveins and stems, which occupies c 70 and 60% of the cross-sectional area of these respective parts, were the sites where modification in phenolics resulted in the greatest improvement in digestibility.     

In vitro multienzyme digestibility of protein of six varieties of African yam bean flours

The in vitro multienzyme protein digestibilities of the flours of six varieties of African yam bean (Sphenostylis stenocarpa), made from both whole seeds and dehulled seeds were investigated. The multienzyme system consisted of trypsin, chymotrypsin and peptidase. Digestibilities were determined for a 10 min digestion period. Both dehulling and heat treatment improved digestibility. Comparison of flours from raw whole seeds with those from dehulled seeds showed that digestibility was better in the latter, with an increase of 6.78%. Heat-treated whole seed flcurs gave a digestibility increase of 6.06% compared with raw flours whereas in the dehulled samples the digestibility increase of heat-treated flours over raw was 5.19%. Heat-treated dehulled seeds were better, with a digestibility increase of 5.90% over the heat-treated whole seed flours. No significant differences (P < 0.05) were observed in the digestibilities among the whole seed flours but significant differences were observed in the dehulled seed flours.     

Effect of Extrusion Cooking on in Vitro Protein Digestibility of Sorghum

Extrusion variables including moisture (15 and 2.5%), temperature (50°, 125° and 200°C) and screw speed (50, 125 and 200 rpm) of two low tannin sorghum varieties extruded with 0, 2 and 4% calcium hydroxide were studied. Protein digestibility was determined by in vitro pepsin assay. Extrusion improved digestibility from 45.9 to 74.6% and 43.9 to 68.2% for the two varieties, respectively. Temperature was the key extrusion variable that influenced digestibility. Screw speed and moisture did not have significant effects. Alteration of pH before extrusion further improved digestibility.     

Characterisation of polyphenols and antioxidant properties of five lettuce varieties and escarole

Salad vegetables could be relevant as dietary sources of natural antioxidants. A better knowledge of their composition can be useful for understanding their potential bioavailability and biological activities. The antioxidant compounds, polyphenols and vitamin C, have been determined in five varieties of lettuce (iceberg, romaine, continental, red oak leaf, lollo rosso) and one variety of escarole (frissé). The polyphenol study by HPLC-DAD-MS/MS ESI allowed the identification of two compounds previously not reported in lettuce; quercetin and luteolin rhamnosyl-hexosides. Qualitative and quantitative differences were observed between the polyphenol profiles. Caffeic acid derivatives were the main phenolics in green varieties, while flavonols were detected in higher quantities in red varieties and escarole, and anthocyanins were only present in red-leafed varieties. The highest total phenolic content was observed in red-leafed varieties while the highest level of vitamin C was detected in the continental variety. The red varieties showed the highest antioxidant activity by all the methods assayed.     

Sorghum kafirin interaction with various phenolic compounds

The ability of various phenolic compounds to bind and precipitate kafirin, the prolamin protein of sorghum, was investigated with regard to effects on its nutritional and functional uses. The protein–phenolic compound interaction was quantified by haze formation and colorimetric determination of total polyphenol bound. Ferulic acid, catechin and extracted phenolics (flavonoids) from condensed tannin‐free sorghum did not complex kafirin. Only tannic acid and sorghum‐condensed tannins had the ability to complex kafirin. The sorghum‐condensed tannins interacted more strongly than tannic acid. The haze of sorghum‐condensed tannins–kafirin was permanent, indicating a strong interaction. The fact that sorghum‐condensed tannins can bind irreversibly to kafirin indicates that this may play a role in decreasing protein digestibility in high‐tannin sorghum and can cause haze formation in lager beer made from high‐tannin sorghum. However, in condensed tannin‐free sorghum, phenolic compounds may not appear to play a major role in decreasing protein digestibility, as these endogenous phenolics may not bind with kafirin. Copyright © 2003 Society of Chemical Industry     

Extraction of antioxidant pigments from dye sorghum leaf sheaths

Extraction of antioxidant biocolorant pigments from leaf sheaths of dye sorghum was optimized. Effects of temperature and ethanol concentration of the extraction solvent on the concentrations of the 3-deoxyanthocyanidins, total phenolics and total anthocyanins, and the colour parameters of the biocolorant extract were evaluated using the response surface methodology. Extraction parameters affected the extraction rate of the biocolorant pigments and the colour characteristics of the extract. Maximum pigment yields were obtained at 50 °C and an ethanol concentration of the solvent of 51 mL 100 mL^?1. Addition of HCl (1 mL 100 mL^?1) to the solvent significantly improved the extractability of the biocolorant pigments. The crude extract from the leaf sheaths showed high antioxidant capacity with a total antioxidant capacity of 1026 mg of Trolox equivalent (TE) g^?1 of DM.     

Evaluation of alternative cereal sources in dog diets: effect on nutrient utilisation and hindgut fermentation characteristics

BACKGROUND: Rice is one of the most commonly used cereal grains in pet foods. However, other cereals such as pearl millet, sorghum and maize have good amino acid profiles and could be used as alternatives to rice in the diet of dogs, thus sparing rice for human consumption. The aim of this study was to evaluate the nutritional worth of these cereals for pet dogs. RESULTS: Eight adult Spitz dogs (age ～10 months, average body weight 6.14 ± 0.58 kg) were used in a 4 × 4 replicated Latin square design to compare the effects of dietary inclusion of four cereals, namely rice, maize, pearl millet and sorghum, on digestibility and hindgut fermentation characteristics. The digestibility of dry matter (DM) was significantly (P < 0.01) reduced when rice was replaced by the alternative cereals. Additionally, the digestibilities of protein, fat and total dietary fibre decreased (P < 0.01) in dogs fed the pearl millet‐based diet. The DM voided in faeces increased (P < 0.05) when rice was replaced by the alternative cereals. Faecal ammonia concentration was higher (P < 0.05) on the rice‐based diet, while faecal lactate concentration was reduced (P < 0.01) on the pearl millet‐ and sorghum‐based diets. CONCLUSION: The results suggest that maize, pearl millet and sorghum are not as effectively utilised as rice as cereal source in the diet of dogs. Copyright © 2009 Society of Chemical Industry     

Phenolic acids released from bermudagrass (Cynodon dactylon) by sequential sodium hydroxide treatment in relation to biodegradation of cell types

Sections of solvent-extracted bermudagrass (Cynodon dactylon L Pers) leaf blades were treated sequentially with increasing concentrations of sodium hydroxide. The amounts of saponifiable phenolic acid monomers and cyclobutane dimers released and the digestibility of the treated blades (ie % dry weight loss) were determined. Leaf sections were examined by scanning electron microscopy for biodegradation of cell types and histochemically (light microscopy) for lignin after treatment with sodium hydroxide. Treatment with 0.1 m sodium hydroxide for 1 h resulted in only minor changes from untreated sections. However, this treatment for 24 h released 86% of the ferulic acid, 65% of the dimers, and c 50% of the p-coumaric acid. Digestibility was increased from 6.5% in the untreated control to 56.6%. Substantial loss of the slowly biodegradable tissues (ie epidermis and parenchyma bundle sheath) and partial biodegradation and disruption of the refractory tissues (ie sclerenchyma, xylem and mestome sheath) occurred; histochemical reactions for lignin were less intense after NaOH treatment. Treatment with 1 m sodium hydroxide for 24 h released 50% of the p-coumaric acid and the remainder of the alkali-extractable ferulic acid and dimers, increased digestibility to 72%, and increased biodegradation of mesophyll and phloem. Mestome sheath cell walls only gave a histochemical reaction for phenolics and the reaction was weak after 1 m NaOH treatment. Alkali treatment increased the biodegradation of all cell types, with lignified tissues reduced to single-cell fibres after 1 and 2 m treatments.     

Leaf and Stem In Vitro Digestibility for Grasses and Dicotyledons of Meadow Plant Communities in Spring

The aim of this study was to improve prediction of the herbage digestibility of meadow plant communities rich in species. The variability of the in vitro dry matter digestibility (IVDMD) at a given date could result both from the species which constitute the plant community and from the variability in the proportion of the different plant components in relation to growth conditions. In order to separate the two factors, we studied the IVDMD change in spring, through the NIRS procedure, one month before and one month after the flowering stage of the main species. This was done for two sets of plant communities with very different botanical composition, dominated by species such as Dactylis glomerata and Chaerophyllum aureum (three) or Festuca rubra and Sanguisorba minor (two plant communities). The IVDMD of dicotyledons was higher than those of grasses both for leaf blades and for stems. The leaf blade IVDMD was quite stable throughout the period studied while those of grasses decreased by about 100 g kg^-1. The stem IVDMD for grasses as for dicotyledons first decreased quickly the month before the flowering stage of the main species, and then move slowly the next month. The difference in IVDMD between those species which were mostly in nutrient-rich habitats was 20 (stems of dicotyledons) to 80 g kg^-1 (leaf blades of grasses) higher when compared to those species which were mostly in nutrient-poor habitats. These results, obtained for leaf blades and stems of sets of species with different habitat characteristics, were in agreement with those of the literature on swards which are almost always pure. For modelling the digestibility change for such plant communities through a growth period, we propose to use the IVDMD values characteristic of a given set of species, as outlined above, and the proportion of the different plant components in the herbage. © 1997 SCI.     

Sorghum (Sorghum bicolor L.): Nutrients,bioactive compounds,and potential impact on human health

Sorghum is the fifth most produced cereal in the world and is a source of nutrients and bioactive compounds for the human diet. We summarize the recent findings concerning the nutrients and bioactive compounds of sorghum and its potential impact on human health, analyzing the limitations and positive points of the studies and proposing directions for future research. Sorghum is basically composed of starch, which is more slowly digested than that of other cereals, has low digestibility proteins and unsaturated lipids, and is a source of some minerals and vitamins. Furthermore, most sorghum varieties are rich in phenolic compounds, especially 3-deoxyanthocyanidins and tannins. The results obtained in vitro and in animals have shown that phenolics compounds and fat soluble compounds (polycosanols) isolated from sorghum benefit the gut microbiota and parameters related to obesity, oxidative stress, inflammation, diabetes, dyslipidemia, cancer, and hypertension. The effects of whole sorghum and its fractions on human health need to be evaluated. In conclusion, sorghum is a source of nutrients and bioactive compounds, especially 3-deoxyanthocyanidins, tannins, and polycosanols, which beneficially modulate, in vitro and in animals, parameters related to noncommunicable diseases. Studies should be conducted to evaluate the effects of different processing on protein and starch digestibility of sorghum as well as on the profile and bioavailability of its bioactive compounds, especially 3-deoxyanthocyanidins and tannins. Furthermore, the benefits resulting from the interaction of bioactive compounds in sorghum and human microbiota should be studied.     

Replacement of buckwheat by black sorghum flour on soba-type noodles

Incorporation of black sorghum flour containing high levels of polyphenols and slowly digestible starch could provide opportunity to enhance nutritional functionality of noodles. Soba-type noodles were prepared based on a typical wheat-buckwheat (65:35) formulation by replacement of buckwheat flour with black sorghum flour at 0%, 25%, 50%, 75% and 100%. Noodle colour, texture, total phenolics, antioxidant capacity, in vitro starch digestibility and sensory acceptability were evaluated. Increasing the addition of black sorghum flour significantly (P < 0.05) decreased the firmness (g) in noodles and imparted a darker colour but increased total polyphenolics and antioxidant capacity. Significantly (P < 0.05) lower rapidly digestible starch and higher resistant starch was found in noodles with >50% replacement with black sorghum flour. Overall acceptability of noodles showed preference for noodles containing 25%–75% black sorghum flour. This study demonstrates the potential of using black sorghum as a novel functional food ingredient in noodle manufacturing.     

Cellulase inhibition by tannins in the testa of field beans (Vicia faba)

The testa of field bean varieties with coloured flowers contained 4–8 % tannin (measured as total phenolics) compared with less than 0.6 % in the testa of white flowered varieties. The tannin present in whole beans was almost entirely contained in the testa. The presence of high levels of tannin reduced in vitro digestibility and solubility in cellulase solutions of the testa and addition of high tannin testa decreased the solubility of cotyledon protein in acid pepsin. Water extracts of the testa from coloured-flower varieties inhibited the action of fungal cellulase and reduced the in vitro digestibility of white flowered testa and cellulose. A highly significant relationship (r= ?0.93***) was found between the tannin content and solubility in cellulase of testa for a range of 24 varieties. It is concluded that the effect of testa tannins on in vitro digestibility can be mainly attributed to their effect on cell wall digesting enzymes rather than an effect on protein solubility per se.     

Analysis of the temperature effect on the components of plant digestibility in two populations of perennial ryegrass

For the development of mechanistic models of herbage digestibility, quantitative insight into the effects of age, temperature and cultivar on digestibility characteristics of individual plant parts is needed. Towards that goal, glasshouse experiments were conducted at day/night temperatures of 13/8, 18/13 and 23/18 °C with vegetative and reproductive crops of two populations of perennial ryegrass (Lolium perenne L) selected for differences in leaf blade digestibility. Cell wall content (CWC) and true cell wall and organic matter digestibility (CWD and OMD) of vegetative and reproductive tillers were related to dimensions, mass, CWC and digestibility of separate plant parts. Compared with the vegetative tillers, the reproductive tillers had higher rates of leaf appearance, organic matter growth and CWD decline. Strikingly, for both tiller types, no direct effect of temperature on whole tiller CWD was observed, since temperature effects could be eliminated completely by relating CWD to development stage (DVS) expressed as number of leaves appearing on the main tiller. Temperature effects on CWD were restricted to its influence on tiller development rate only. The decline of CWD of individual plant parts with DVS in the reproductive tillers could be described with a negative exponential curve, which reached an asymptote that was higher for leaf blades (755 g kg^?1) than for leaf sheaths (491 g kg^?1) and stem internodes (230 g kg^?1). However, all plant parts in both tiller types had the same fractional CWD decline rate of 0.395 per leaf appearance interval, independent of plant part insertion level, population or temperature. Differences between temperature treatments in OMD were caused by the higher CWC of plant parts at higher temperature, due to a stronger decline of the specific organic matter mass than of the specific cell wall mass of plant parts at increasing temperature. Differences in whole tiller OMD between populations were observed only for vegetative tillers and were also caused by differences in CWC. It is concluded that temperature increase accelerated both the tiller development rate and the rate of decline of CWD during aging to the same extent, whereas plant parts responded similarly in the fractional CWD decline pattern as a function of DVS. These trends offer unique possibilities for modelling grass digestibility under contrasting temperature regimes. © 2003 Society of Chemical Industry     

In-vitro protein and sulphur amino acid availability as a measure of bean protein quality

The total and ‘available’ cystine and methionine, and the in-vitro and in-vivo protein digestibilities were determined in six varieties of Phaseolus vulgaris with different seed coat colours. Reactive cystine and methionine, evaluated by chemical methods after in-vitro enzymic digestion, were taken as a measure of the availability of sulphur amino acids. Cystine ‘availability’ ranged from 43 to 51% and from 31 to 58% in raw and cooked samples, respectively, while methionine ‘availability’ was over 90%, except for the two red varieties (55% and 74%). No correlation was found between cystine and methionine ‘availability’ and in-vitro protein digestibility. In-vitro protein digestibility (76.6-80.7%) showed a good correlation (r = 0.857; P < 0.05) with in-vivo values (72.0-80.9%). Amino acid score corrected for protein digestibility and for sulphur amino acids availability, as suggested by the Codex Committee on Vegetable Proteins, seems to predict accurately the biological quality of bean protein, as was shown when in-vitro indices were compared with net protein utilisation and relative protein value.     

Tiller Development Influences Seasonal Change in Cell Wall Digestibility of Big Bluestem(Andropogon gerardii)

The productivity of cool-season forage grasses declines during mid-summer in the southern corn belt of the USA. Warm-season grasses are productive during this time, but their digestibility decreases from spring to summer. The objective of this study was to investigate cell wall factors contributing to the decline in in vitro dry matter digestibility (IVDMD) of big bluestem ( Andropogon gerardii Vitman) leaf blades from late spring (May) to mid-summer (July) under three harvest regimens. Under frequent defoliation, decrease in cell wall digestibility accounted for much of the change in IVDMD. Among cell wall constituents, only xylose and alkali-labile phenolic acids increased significantly from spring to summer. Change in p -coumaric acid content and the ratio of p -coumaric acid to ferulic acid were both negatively correlated with the decrease in cell wall digestibility. While glucose and uronic acid digestibility decreased from spring to summer, xylose was consistently the least digestible of the cell wall monomers. In warm-season grasses grown under constant environments, tiller development causes an increase in leaf structural tissue, and the data suggest that the seasonal decline in leaf blade cell wall digestibility was partially due to tiller development.     

Alleviation of the adverse effect of cooking on sorghum protein digestibility through fermentation in traditional African porridges

Cooking sorghum is well known to reduce its protein digestibility. In southern Africa fermented sorghum porridges are commonly consumed. Knowledge is lacking as to how their preparation affects sorghum protein digestibility. Five sorghum varieties of varied origin were fermented using traditional semi-solid state fermentation. In vitro protein digestibility and a new index, in vitro insoluble protein digestibility, were measured. Both increased during fermentation, generally within the first day, coinciding with a strong decrease in pH. The increase in insoluble protein digestibility suggests fermentation causes structural changes in the sorghum storage proteins (prolamins and glutelins), making them more accessible to pepsin attack. Wet cooking during porridge-making greatly reduced protein digestibility. Combining fermentation with cooking, either fermenting then cooking or cooking then fermenting, significantly improved protein digestibility over wet cooking alone. Thus natural fermentation, as applied in traditional African porridge preparation is an effective method of improving the protein digestibility of cooked sorghum.