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John R N Taylor - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of formation of visco-elastic masses and their properties between zeins and Kafirins.
    Food chemistry, 2017
    Co-Authors: Janet Taylor, Joseph Ochieng Anyango, Peter J. Muhiwa, Segun I. Oguntoyinbo, John R N Taylor
    Abstract:

    Zeins of differing sub-class composition much more readily formed visco-elastic masses in water or acetic acid solutions than equivalent kafirin preparations. Visco-elastic masses could be formed from both zein and kafirin preparations by coacervation from glacial acetic acid. Dissolving the prolamins in glacial acetic acid apparently enabled protonation and complete solvation. Stress-relaxation analysis of coacervated zein and kafirin visco-elastic masses showed they were initially soft. With storage, they became much firmer. Zein masses exhibited predominantly viscous flow properties, whereas kafirin masses were more elastic. The γ-sub-class is apparently necessary for the retention of visco-elastic mass softness with kafirin and zein, and for elastic recovery of kafirin. Generally, regardless of water or acetic acid treatment, all the zein preparations had similar FTIR spectra, with greater α-helical conformation, than the kafirin preparations which were also similar to each other. Kafirin visco-elastic masses have a much higher elastic character than zein masses.

  • Extraction and film properties of kafirin from coarse sorghum and sorghum DDGS by percolation
    Cereal Chemistry Journal, 2017
    Co-Authors: Peter J. Muhiwa, Janet Taylor, John R N Taylor
    Abstract:

    The high cost of kafirin and zein restricts their use for bioplastic and food applications. Effective, simple, and rapid kafirin/zein isolation processes are required. Here a percolation-type aqueous ethanol solvent extraction process from coarse meals (grits) and coarse sorghum distillers dried grains and solubles (DDGS) for kafirin and zein isolation employing a low ratio of extractant to meal (2.5:1) was investigated, which is potentially applicable in the grain bioethanol industry. Postextraction filtration times were more than twice as fast using coarse meals compared with fine flours. Washing the meals prior to extraction to remove starch improved protein preparation purity to 73–85% compared with 68–72% for unwashed meals. Hence, no subsequent filtration or centrifugation step is required to clean up the kafirin/zein solution prior to solvent evaporation. With a single extraction step, kafirin/zein yields were 48% (protein basis) for DDGS and 53–70% for washed sorghum/maize meals. Cast films were u...

  • Kafirin microparticle encapsulated sorghum condensed tannins exhibit potential as an anti-hyperglycaemic agent in a small animal model
    Journal of Functional Foods, 2016
    Co-Authors: Malory R. Links, Janet Taylor, Marlena C. Kruger, Vinny Naidoo, John R N Taylor
    Abstract:

    Abstract In vitro analysis has indicated that sorghum condensed tannins (SCT) survive simulated gastric digestion and inhibit digestive amylases when encapsulated in sorghum kafirin protein microparticles (SCT-KEMS). This study investigated SCT-KEMS as a potential anti-hyperglycaemic nutraceutical agent in vivo. Oral starch tolerance tests were performed on healthy rats. SCT-KEMS prevented a blood glucose spike and decreased the maximum blood glucose level by 11.8% compared to the water control, the same reduction as the acarbose standard. Neither SCT-KEMS nor acarbose elevated serum insulin levels. Further, the rats took the SCT-KEMS willingly, unlike the case with the unencapsulated SCTs. SCT-KEMS are potentially effective nutraceuticals for the management of hyperglycaemia because of the high affinity of SCT for the proline-rich kafirin and kafirin's slow digestibility, which enables SCT bitterness to be masked and delivered to the small intestine to inhibit carbohydrate hydrolysis, thus reducing glycaemic response.

  • biocompatibility and biodegradation of protein microparticle and film scaffolds made from kafirin sorghum prolamin protein subcutaneously implanted in rodent models
    Journal of Biomedical Materials Research Part A, 2015
    Co-Authors: Janet Taylor, Vinny Naidoo, Joseph Ochieng Anyango, Marnie Potgieter, Karlien Kallmeyer, Michael S Pepper, John R N Taylor
    Abstract:

    Kafirin, the sorghum prolamin protein, like its maize homologue zein, can be made into microparticles and films and potentially used as a biomaterial. Zein has good bio- and cyto-compatibility. Kafirin could be advantageous as it is more hydrophobic, more crosslinked, more slowly digested by mammalian proteases than zein and is non-allergenic. The safety and biocompatibility of kafirin implants in two forms was determined in rodent models. One week post subcutaneous injection of kafirin microparticles (size 5-µm diameter) in mice, chronic inflammation, abnormal red blood cells, and gross fibrin formation were observed. This chronic inflammatory response was possibly caused by the release of hydrolysis products such as glutamate during the degradation of the kafirin microparticles. In contrast, films made from kafirin microparticles (50-µm thick, folded into 1 cm3) implanted in rats showed no abnormal inflammatory reactions and were only partially degraded by day 28. The slower degradation of the kafirin films was probably due to their far smaller surface area when compared to kafirin microparticles. Thus, kafirin films appear to have potential as a biomaterial. This study also raises awareness that the form of prolamin based biomaterials, (kafirin and zein) should be considered when assessing the safety of such materials. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2582–2590, 2015.

  • Co-suppression of synthesis of major α-kafirin sub-class together with γ-kafirin-1 and γ-kafirin-2 required for substantially improved protein digestibility in transgenic sorghum
    Plant Cell Reports, 2014
    Co-Authors: Andile W. Grootboom, Nompumelelo L. Mkhonza, Zodwa Mbambo, Martha M. O’kennedy, Laura S. Silva, Rachel Chikwamba, Janet Taylor, John R N Taylor, Luke Mehlo
    Abstract:

    Key message Co-suppressing major kafirin sub-classes is fundamental to improved protein digestibility and nutritional value of sorghum. The improvement is linked to an irregularly invaginated phenotype of protein bodies. Abstract The combined suppression of only two genes, γ kafirin-1 (25 kDa) and γ-kafirin-2 (50 kDa), significantly increases sorghum kafirin in vitro digestibility. Co-suppression of a third gene, α-kafirin A1 (25 kDa), in addition to the two genes increases the digestibility further. The high-digestibility trait has previously only been obtained either through the co-suppression of six kafirin genes (α-A1, 25 kDa; α-B1, 19 kDa; α-B2, 22 kDa; γ-kaf1, 27 kDa; γ-kaf 2, 50 kDa; and δ-kaf 2, 18 kDa) or through random chemical-induced mutations (for example, the high protein digestibility mutant). We present further evidence that suppressing just three of these genes alters kafirin protein cross-linking and protein body microstructure to an irregularly invaginated phenotype. The irregular invaginations are consistent with high pepsin enzyme accessibility and hence high digestibility. The approach we adopted towards increasing sorghum protein digestibility appears to be an effective tool in improving the status of sorghum as a principal supplier of energy and protein in poor communities residing in marginal agro-ecological zones of Africa.

Janet Taylor - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of formation of visco-elastic masses and their properties between zeins and Kafirins.
    Food chemistry, 2017
    Co-Authors: Janet Taylor, Joseph Ochieng Anyango, Peter J. Muhiwa, Segun I. Oguntoyinbo, John R N Taylor
    Abstract:

    Zeins of differing sub-class composition much more readily formed visco-elastic masses in water or acetic acid solutions than equivalent kafirin preparations. Visco-elastic masses could be formed from both zein and kafirin preparations by coacervation from glacial acetic acid. Dissolving the prolamins in glacial acetic acid apparently enabled protonation and complete solvation. Stress-relaxation analysis of coacervated zein and kafirin visco-elastic masses showed they were initially soft. With storage, they became much firmer. Zein masses exhibited predominantly viscous flow properties, whereas kafirin masses were more elastic. The γ-sub-class is apparently necessary for the retention of visco-elastic mass softness with kafirin and zein, and for elastic recovery of kafirin. Generally, regardless of water or acetic acid treatment, all the zein preparations had similar FTIR spectra, with greater α-helical conformation, than the kafirin preparations which were also similar to each other. Kafirin visco-elastic masses have a much higher elastic character than zein masses.

  • Extraction and film properties of kafirin from coarse sorghum and sorghum DDGS by percolation
    Cereal Chemistry Journal, 2017
    Co-Authors: Peter J. Muhiwa, Janet Taylor, John R N Taylor
    Abstract:

    The high cost of kafirin and zein restricts their use for bioplastic and food applications. Effective, simple, and rapid kafirin/zein isolation processes are required. Here a percolation-type aqueous ethanol solvent extraction process from coarse meals (grits) and coarse sorghum distillers dried grains and solubles (DDGS) for kafirin and zein isolation employing a low ratio of extractant to meal (2.5:1) was investigated, which is potentially applicable in the grain bioethanol industry. Postextraction filtration times were more than twice as fast using coarse meals compared with fine flours. Washing the meals prior to extraction to remove starch improved protein preparation purity to 73–85% compared with 68–72% for unwashed meals. Hence, no subsequent filtration or centrifugation step is required to clean up the kafirin/zein solution prior to solvent evaporation. With a single extraction step, kafirin/zein yields were 48% (protein basis) for DDGS and 53–70% for washed sorghum/maize meals. Cast films were u...

  • improved storage and eat ripe quality of avocados using a plant protein based coating formulation
    Quality Assurance and Safety of Crops & Foods, 2016
    Co-Authors: Janet Taylor, M Muller, Amanda Minnaar
    Abstract:

    Coating comprising the plant protein, kafirin, propylene glycol (PG) and glucono-delta-lactone (GDL) have been shown to extend the quality of ‘Packham’s Triumph’ pears. In this study, both of these coating treatments considerably extended the shelf-life and the time that the eat-ripe quality of ‘Hass’ avocados was maintained when compared to uncoated fruit. To determine the roles of the additives, PG and GDL in the functionality of kafirin edible coatings, different kafirin coatings were applied to ‘Hass’ avocados prior to storage under ripening conditions of 18 °C for up to 21 days. All the kafirin coatings were effective at extending and maintaining the shelf-life quality of avocados compared to uncoated fruit due to reduced respiration rate, 102 ml CO2/kg/h for kafirin-PG+GDL compared to 115 ml CO2/kg/h uncoated avocados on day 14 and consequently reduced ethylene production of the coated fruit. Kafirin-PG+GDL coated avocados lost less weight and remained firmer than uncoated fruit. Descriptive sensory...

  • Kafirin microparticle encapsulated sorghum condensed tannins exhibit potential as an anti-hyperglycaemic agent in a small animal model
    Journal of Functional Foods, 2016
    Co-Authors: Malory R. Links, Janet Taylor, Marlena C. Kruger, Vinny Naidoo, John R N Taylor
    Abstract:

    Abstract In vitro analysis has indicated that sorghum condensed tannins (SCT) survive simulated gastric digestion and inhibit digestive amylases when encapsulated in sorghum kafirin protein microparticles (SCT-KEMS). This study investigated SCT-KEMS as a potential anti-hyperglycaemic nutraceutical agent in vivo. Oral starch tolerance tests were performed on healthy rats. SCT-KEMS prevented a blood glucose spike and decreased the maximum blood glucose level by 11.8% compared to the water control, the same reduction as the acarbose standard. Neither SCT-KEMS nor acarbose elevated serum insulin levels. Further, the rats took the SCT-KEMS willingly, unlike the case with the unencapsulated SCTs. SCT-KEMS are potentially effective nutraceuticals for the management of hyperglycaemia because of the high affinity of SCT for the proline-rich kafirin and kafirin's slow digestibility, which enables SCT bitterness to be masked and delivered to the small intestine to inhibit carbohydrate hydrolysis, thus reducing glycaemic response.

  • biocompatibility and biodegradation of protein microparticle and film scaffolds made from kafirin sorghum prolamin protein subcutaneously implanted in rodent models
    Journal of Biomedical Materials Research Part A, 2015
    Co-Authors: Janet Taylor, Vinny Naidoo, Joseph Ochieng Anyango, Marnie Potgieter, Karlien Kallmeyer, Michael S Pepper, John R N Taylor
    Abstract:

    Kafirin, the sorghum prolamin protein, like its maize homologue zein, can be made into microparticles and films and potentially used as a biomaterial. Zein has good bio- and cyto-compatibility. Kafirin could be advantageous as it is more hydrophobic, more crosslinked, more slowly digested by mammalian proteases than zein and is non-allergenic. The safety and biocompatibility of kafirin implants in two forms was determined in rodent models. One week post subcutaneous injection of kafirin microparticles (size 5-µm diameter) in mice, chronic inflammation, abnormal red blood cells, and gross fibrin formation were observed. This chronic inflammatory response was possibly caused by the release of hydrolysis products such as glutamate during the degradation of the kafirin microparticles. In contrast, films made from kafirin microparticles (50-µm thick, folded into 1 cm3) implanted in rats showed no abnormal inflammatory reactions and were only partially degraded by day 28. The slower degradation of the kafirin films was probably due to their far smaller surface area when compared to kafirin microparticles. Thus, kafirin films appear to have potential as a biomaterial. This study also raises awareness that the form of prolamin based biomaterials, (kafirin and zein) should be considered when assessing the safety of such materials. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2582–2590, 2015.

Scott R. Bean - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of extraction methods for isolating kafirin protein from food grade sorghum flour
    August 2019, 2019
    Co-Authors: Paola Pontieri, Scott R. Bean, Jacopo Troisi, Michael Tilley, Marco Di Salvo, Antonio Boffa, Domenico Pignone, Fabio Del Giudice, Mariarosaria Aletta, Pietro Alifano
    Abstract:

    Isolated sorghum (Sorghum bicolor) storage proteins (Kafirins) have been successfully used in the production of several bio-materials including adhesives, films, micro-particles, fibers, and biological scaffold material. Comparatively little research has been conducted on the use of isolated Kafirins in food products or to produce bioactive peptides via hydrolysis for nutritional uses. To support such research, the aim of this study was to compare existing methods for bulk isolation of sorghum Kafirins with the goal of identifying a solvent with the least toxicity that maintained a high extraction rate from food grade sorghum flour. A secondary goal was to characterize the kafirin isolates produced from various extraction methods to provide some information on their potential use in food products to guide future research in this area. Five different extraction methods were compared including 1) aqueous ethanol containing NaOH and sodium metabisulfite, 2) glacial acetic acid, 3) aqueous ethanol with sodium metabisulfite, 4) aqueous ethanol at acidic pH, and 5) alkaline pH alone. The protein contents of the kafirin isolates obtained by the five methods ranged from 49.76% to 56.83%. Kafirin isolates were characterized using reversed phase (RP)-high performance liquid chromatography (HPLC), which revealed substantial variability in the various kafirin patterns among the extraction methods tested. However, characterization of the kafirin isolates by size exclusion chromatography (SEC) did not show a high degree of variability among the methods tested. Likewise, analysis of the samples using sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE) showed essentially the same band profiles but with different band intensities among kafirin extraction methods. Surface hydrophobicity of the kafirin isolates varied considerably with isolates extracted with glacial acetic acid and aqueous ethanol plus sodium metabisulfite the most hydrophobic as indicated by hydrophobic dye binding.

  • Grain sorghum proteomics: integrated approach toward characterization of endosperm storage proteins in kafirin allelic variants.
    Journal of agricultural and food chemistry, 2014
    Co-Authors: Julia E. Cremer, Scott R. Bean, Brian P. Ioerger, Michael Tilley, Jae B. Ohm, Rhett C. Kaufman, Jeff D. Wilson, David J. Innes, Edward K. Gilding, Ian D. Godwin
    Abstract:

    Grain protein composition determines quality traits, such as value for food, feedstock, and biomaterials uses. The major storage proteins in sorghum are the prolamins, known as Kafirins. Located primarily on the periphery of the protein bodies surrounding starch, cysteine-rich beta- and gamma-Kafirins may limit enzymatic access to internally positioned alpha-Kafirins and starch. An integrated approach was used to characterize sorghum with allelic variation at the kafirin loci to determine the effects of this genetic diversity on protein expression. Reversed-phase high performance liquid chromatography and lab-on-a-chip analysis showed reductions in alcohol-soluble protein in beta-kafirin null lines. Gel-based separation and liquid chromatography-tandem mass spectrometry identified a range of redox active proteins affecting storage protein biochemistry. Thioredoxin, involved in the processing of proteins at germination, has reported impacts on grain digestibility and was differentially expressed across genotypes. Thus, redox states of endosperm proteins, of which Kafirins are a subset, could affect quality traits in addition to the expression of proteins.

  • impacts of kafirin allelic diversity starch content and protein digestibility on ethanol conversion efficiency in grain sorghum
    Cereal Chemistry, 2014
    Co-Authors: Julia E. Cremer, Scott R. Bean, Michael Tilley, Rhett C. Kaufman, Jeff D. Wilson, Edward K. Gilding, I. D. Godwin, Thanh H Vu, Donghai Wang
    Abstract:

    ABSTRACT Seed protein and starch composition determine the efficiency of the fermentation process in the production of grain-based ethanol. Sorghum, a highly water- and nutrient-efficient plant, provides an alternative to fuel crops with greater irrigation and fertilizer requirements, such as maize. However, sorghum grain is generally less digestible because of extensive disulfide cross-linking among sulfur-rich storage proteins in the protein– starch matrix. Thus, the fine structure and composition of the seed endosperm directly impact grain end use, including fermentation performance. To test the hypothesis that kafirin (prolamin) seed storage proteins specifically influence the efficiency of ethanol production from sorghum, 10 diverse genetic lines with allelic variation in the β-, γ-, and (δ-Kafirins, including three β-kafirin null mutants, were tested for ethanol yield and fermentation efficiency. Our selected lines showed wide variation in grain biochemical features, including total protein (9.96–16...

  • Grain Sorghum Proteomics: Integrated Approach toward Characterization of Endosperm Storage Proteins in Kafirin Allelic Variants
    2014
    Co-Authors: Julia E. Cremer, Scott R. Bean, Brian P. Ioerger, Jae B. Ohm, Rhett C. Kaufman, Jeff D. Wilson, David J. Innes, Edward K. Gilding, Michael M. Tilley, Ian D. Godwin
    Abstract:

    Grain protein composition determines quality traits, such as value for food, feedstock, and biomaterials uses. The major storage proteins in sorghum are the prolamins, known as Kafirins. Located primarily on the periphery of the protein bodies surrounding starch, cysteine-rich β- and γ-Kafirins may limit enzymatic access to internally positioned α-Kafirins and starch. An integrated approach was used to characterize sorghum with allelic variation at the kafirin loci to determine the effects of this genetic diversity on protein expression. Reversed-phase high performance liquid chromatography and lab-on-a-chip analysis showed reductions in alcohol-soluble protein in β-kafirin null lines. Gel-based separation and liquid chromatography–tandem mass spectrometry identified a range of redox active proteins affecting storage protein biochemistry. Thioredoxin, involved in the processing of proteins at germination, has reported impacts on grain digestibility and was differentially expressed across genotypes. Thus, redox states of endosperm proteins, of which Kafirins are a subset, could affect quality traits in addition to the expression of proteins

  • Separation of alcohol soluble sorghum proteins using non-porous cation-exchange columns.
    Journal of Chromatography A, 2012
    Co-Authors: Deidre L. Blackwell, Scott R. Bean
    Abstract:

    a b s t r a c t Kafirins, the storage proteins and major protein of the cereal grain sorghum, play an important nutritional role for millions of people in parts of Africa and Asia. Kafirins are non-water soluble, being soluble only in the presence of detergents or aqueous alcohol mixtures and are among the most hydrophobic of the cereal proteins. Limited Mw heterogeneity of Kafirins reduces their resolution when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Charge based separation techniques have been shown to have improved resolution of Kafirins, but due to the nature of their solubility, ion-exchange (IE)-HPLC has not been widely used to separate these proteins. To overcome issues of solubility, two different mobile phases were evaluated. The first mobile phase was based on 60% acetonitrile at acidic pH using guanidine-hydrochloride (Gdn-HCl) gradients to elute the proteins from a non-porous cation-exchange column. The second mobile phase tested consisted of 60% acetonitrile using an increasing concentration gradient of a triethylamine phosphate (TEAP) buffer at pH 3.0. The type of alkylation reagent used to stabilize kafirin extracts prior to analysis was found to have an impact on the IE-HPLC separations with the reagent 4-vinylpyridine providing the best resolution. Separations of Kafirins in the TEAP mobile phase system resulted in 10 major peaks being resolved. Combining IE-HPLC with reverse phase (RP)-HPLC into 2D separations revealed that the -Kafirins clustered into three major groups not readily apparent in either 1D separation. Published by Elsevier B.V.

Bruce R. Hamaker - One of the best experts on this subject based on the ideXlab platform.

  • cellular response to the high protein digestibility high lysine hdhl sorghum mutation
    Plant Science, 2015
    Co-Authors: Mustapha Benmoussa, A. Chandrashekar, Gebisa Ejeta, Bruce R. Hamaker
    Abstract:

    Abstract A high protein digestibility/high-lysine mutant P721Q ( hdhl ) with a multi-folded protein body morphology has been developed, with a 22 kDa α-kafirin single point mutation having also been recently identified. Relatively little is known regarding the resulting cellular response in hdhl endosperm. The aim is to elucidate these biochemical changes. Two-dimentional gel electrophoresis showed an apparent increase of non-kafirin and a decrease in Kafirins content in hdhl endosperm. Mass spectrometry data yielded the identity of differentially expressed non-kafirin proteins in hdhl , wild-type lines such as cytoskeleton and chaperones proteins, and also others involved in amino acids and carbohydrates biochemical synthesis pathways. Western blot analysis showed that chaperone proteins were more highly expressed in the hdhl than the wild-type sorghum and confirmed the non-kafirin proteins proteomic results. Two-dimentional gel electrophoresis showed that the γ-kafirin subunits content had decreased, and the 22 kDa α-kafirin subunit was increased in hdhl without any apparent molecular mass change. The observed differential expression most likely led to proteins interactions between γ- and α-kafirin subunits in particular, which resulted in a Kafirins packing differently to form the protein body’s multi-folded morphology, while also improving its digestibility.

  • grain of high digestible high lysine hdhl sorghum contains Kafirins which enhance the protein network of composite dough and bread
    Journal of Cereal Science, 2012
    Co-Authors: Morgan Goodall, Gebisa Ejeta, Osvaldo H Campanella, Bruce R. Hamaker
    Abstract:

    The aim of this study was to determine whether protein body-free Kafirins in high digestibility, high-lysine (HDHL) sorghum flour can participate as viscoelastic proteins in sorghum-wheat composite dough and bread. Dough extensibility tests revealed that maximum resistance to extension (g) and time to dough breakage (sec) at 35 °C for HDHL sorghum-wheat composite doughs were substantially greater (p < 0.01) than for normal sorghum-wheat composite doughs at 30 and 60% substitution levels. Functional changes in HDHL kafirin occurred upon exceeding its Tg. Normal sorghum showed a clear decrease in strain hardening at 60% substitution, whereas HDHL sorghum maintained a level similar to wheat dough. Significantly higher loaf volumes resulted for HDHL sorghum-wheat composites compared to normal sorghum-wheat composites at substitution levels above 30% and up to 56%, with the largest difference at 42%. HDHL sorghum-wheat composite bread exhibited lower hardness values, lower compressibility and higher springiness than normal sorghum-wheat composite bread. Finally, HDHL sorghum flour mixed with 18% vital wheat gluten produced viscoelastic dough while normal sorghum did not. These results clearly show that kafirin in HDHL sorghum flour contributes to the formation of an improved protein network with viscoelastic properties that leads to better quality composite doughs and breads.

  • a highly digestible sorghum mutant cultivar exhibits a unique folded structure of endosperm protein bodies
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Maria P. Oria, Bruce R. Hamaker, John D Axtell, Chiaping Huang
    Abstract:

    The endosperm of a sorghum mutant cultivar, with high in vitro uncooked and cooked protein digestibilities, was examined by transmission electron microscopy and α-, β-, and γ-Kafirins (storage proteins) were localized within its protein bodies. Transmission electron microscopy micrographs revealed that these protein bodies had a unique microstructure related to high protein digestibility. They were irregular in shape and had numerous invaginations, often reaching to the central area of the protein body. Protein bodies from normal cultivars, such as P721N studied here, with much lower uncooked and cooked digestibilities are spherical and contain no invaginations. Immunocytochemistry results showed that the relative location of α- and β-Kafirins within the protein bodies of the highly digestible genotype were similar to the normal cultivar, P721N. γ-Kafirin, however, was concentrated in dark-staining regions at the base of the folds instead of at the protein body periphery, as is typical of normal cultivars. The resulting easy accessibility of digestive enzymes to α-kafirin, the major storage protein, in addition to the increased surface area of the protein bodies of the highly digestible cultivar appear to account for its high in vitro protein digestibility.

  • in vitro protein digestibility of developing and mature sorghum grain in relation to α β and γ kafirin disulfide crosslinking
    Journal of Cereal Science, 1995
    Co-Authors: M P Oria, Bruce R. Hamaker, J M Schull
    Abstract:

    Abstract Sorghum (P721N, 1992) was harvested at selected days after half-bloom (DAHB) and at maturity, and analyzed for protein and moisture contents, protein digestibility, α-, β-, and γ-kafirin contents, and unextractable disulfide-bound complexes. α-Kafirin synthesis began before 10 DAHB, and β- and γ-kafirin at 20 DAHB. All the Kafirins were as abundant at 40 DAHB as at maturity. Protein digestibilities of uncooked flour were about 90%, and dropped to 73% at maturity. Digestibilities of cooked flour dropped markedly at 35 DAHB, 40 DAHB and maturity. A comparison of 1992 and 1987 data indicates that digestibility decreases with moisture content, not days of development. The amount of disulfide “crosslinked” β- and γ-Kafirins was insignificant at the earlier stages, though increased as the grain matured. Since kafirin synthesis is complete by 40 DAHB, we suggest that the decrease in digestibility in maturing grain is due to the drying effect and formation of disulfide-bound complexes involving β- and γ-Kafirins. Cooking the flour may further promote protein interactions, particularly after kafirin synthesis has ceased.

  • Resistance of Sorghum .alpha.-, .beta.-, and .gamma.-Kafirins to Pepsin Digestion
    Journal of Agricultural and Food Chemistry, 1995
    Co-Authors: Maria P. Oria, Bruce R. Hamaker, Jeannette M. Shull
    Abstract:

    The differences in pepsin digestibility among α-, β-, and γ-Kafirins and the effect of treatment with sodium bisulfite were investigated in uncooked and cooked sorghum flour. Enzyme-linked immunosorbent assay revealed that when the untreated flour was incubated with pepsin, 31.0% of α-kafirin, 15.3% of β-kafirin, and 13.5% of γ-kafirin remained undigested. Transmission electron microscopy (TEM) showed that protein body digestion was initiated at the surface where β- and γ-Kafirins are located. When the flour was treated with sodium bisulfite, the Kafirins in the residue were much less and protein bodies were largely reduced in size. Cooking the flour reduced the digestibility of all three Kafirins, particularly of the β and γ fractions. Some cooked protein bodies appeared unaffected by digestion as revealed by TEM. Sodium bisulfite reversed the effect of cooking, although not completely. It appears that on cooking, disulfide linkage formation is enhanced among β- and γ-Kafirins, or among these and matrix proteins, which delays α-kafirin digestion. A reducing agent enhances the digestion of these cross-linked proteins and facilitates the exposure of α-kafirin to the enzyme.

Peter S. Belton - One of the best experts on this subject based on the ideXlab platform.

  • Kafirin microparticle encapsulation of catechin and sorghum condensed tannins.
    Journal of agricultural and food chemistry, 2009
    Co-Authors: Janet Taylor, John R N Taylor, Peter S. Belton, Amanda Minnaar
    Abstract:

    To exploit the porous nature of previously developed kafirin microparticles, encapsulation of the bioactive polyphenols, catechin and sorghum condensed tannins, was investigated. The antioxidant release profiles of the encapsulated substances were studied under simulated gastric conditions. Kafirin microparticles encapsulating catechin or sorghum condensed tannins were similar in size to control kafirin microparticles (5-6 mum). TEM showed that kafirin microparticles encapsulating catechin had a rough porous surface. Microparticles encapsulating sorghum condensed tannins were irregular in shape, some apparently joined together, with a mixture of rough and smooth surfaces. Over a period of 4 h, catechin and sorghum condensed tannin encapsulated kafirin microparticles showed virtually no protein digestion but released approximately 70 and 50%, respectively, of total antioxidant activity. Thus, the use of kafirin microparticles to encapsulate catechin and sorghum condensed tannins has potential as an effective method of controlled release of dietary antioxidants.

  • Preparation of free-standing films from kafirin protein microparticles: mechanism of formation and functional properties.
    Journal of agricultural and food chemistry, 2009
    Co-Authors: Janet Taylor, John R N Taylor, Peter S. Belton, Amanda Minnaar
    Abstract:

    A method of preparing free-standing films using kafirin microparticles made by phase separation from acetic acid is described. Film preparation involved the suspension of the microparticles in acetic acid solution containing plasticizer. On evaporation of the acetic acid, a complete, smooth, flexible, transparent film was formed. A minimum concentration of acid was required to form a cohesive film relative to the concentration of kafirin. This was approximately 10.8:1, percent acetic acid to percent kafirin. Film formation appears to be by controlled aggregation of kafirin microparticles, followed by dissolution of the microparticles in acetic acid and drying into a cohesive film. The functional properties of microparticle films were generally superior to films cast directly from a solution of kafirin, at the same protein content. Kafirin microparticle films were very thin (

  • Alteration of kafirin and kafirin film structure by heating with microwave energy and tannin complexation.
    Journal of agricultural and food chemistry, 2006
    Co-Authors: Y. B. Byaruhanga, M. Naushad Emmambux, Peter S. Belton, Nikolaus Wellner, John R N Taylor
    Abstract:

    Heating with microwave energy and tannin complexation of kafirin both increase the tensile strength of cast kafirin bioplastic films. The effects of these treatments on the molecular structure of kafirin and of kafirin in the film were investigated. SDS−PAGE of heated wet kafirin showed an increase in kafirin oligomers. Disulfide groups increased in heated kafirin and in films made from the heated kafirin. Fourier transform infrared (FTIR) spectroscopy of heated kafirin and films made from the heated kafirin indicated an increase in β-sheet conformation. In contrast, kafirin complexation with tannic acid (TA) and sorghum condensed tannin (SCT) resulted in a slight decrease in β-sheet conformation in the kafirin and a larger decrease in the kafirin in the films. Raman spectroscopy showed that, with TA, there was a shift in peak from 1710 to 1728 cm-1 for kafirin−tannic acid complexes, indicating kafirin and tannic acid interaction. The protein conformational changes presumably facilitated cross-linking bet...

  • Kafirin structure and functionality
    Journal of Cereal Science, 2006
    Co-Authors: Peter S. Belton, Ivonne Delgadillo, Nigel G. Halford, Peter R. Shewry
    Abstract:

    Abstract The structural and functional properties of Kafirins are reviewed. Three classes of kafirin: the α , β and γ forms have been identified at the protein level and one, the δ , has been identified only at the gene and transcript levels. All forms show high homology with the equivalent zein proteins. By analogy with the zeins it is believed that the α -Kafirins probably have an extended hairpin structure in solution, comprising elements of α -helix, β -sheet and turns folded back on itself. Kafirins are the most hydrophobic of the prolamins as shown by their solubility, and calculated hydration free energies. The proteins exhibit extensive cross-linking by disulphide bonds and on cooking form indigestible aggregates which are not solubilised by reduction of disulphide bonds. In spite of continuing studies, the reasons for the low digestibility of the protein remain uncertain and there may be several factors involved. Other research has shown that Kafirins may have non-food uses and may be used to form films.

  • Effect of preparation conditions on protein secondary structure and biofilm formation of kafirin
    Journal of agricultural and food chemistry, 2005
    Co-Authors: Chunli Gao, Janet Taylor, Mary L. Parker, Nikolaus Wellner, Yusuf B. Byaruhanga, E. N. Clare Mills, Peter S. Belton
    Abstract:

    Various extraction and drying conditions for the isolation of kafirin from dry-milled, whole grain sorghum have been investigated, with a view to optimizing extraction of the protein for commercial food coatings and packaging films. The addition of sodium hydroxide to an aqueous ethanol extractant increased the yield and solubility of kafirin. Subsequent heat drying at 40 degrees C was shown to cause the kafirin to aggregate as indicated by an increase in intermolecular beta-sheets. Extraction of the flour using ethanol (70%, w/w) with 0.5% (w/w) sodium metabisulfite and 0.35% (w/w) sodium hydroxide at 70 degrees C followed by freeze-drying of the protein was found to produce a yield of 54% kafirin with good film-forming properties. The kafirin films were assessed for their sensory properties, tensile strength, strain, and water vapor permeability. Fourier transform infrared spectroscopy was used to study the secondary structure of the extracted Kafirins. The best films were made with kafirin containing a large proportion of nativelike alpha-helical structures with little intermolecular beta-sheet content as indicated by the Fourier transform infrared reflectance peak intensity ratios associated with these secondary structures. The principal factor affecting the secondary structure of the protein appeared to be the temperature at which the protein was dried. Heat drying resulted in a greater proportion of intermolecular beta-sheets. Any industrial-scale extraction must therefore minimize protein aggregation and maximize native alpha-helical structures to achieve optimal film quality.