Amylose and amylopectin in starch by asymmetric flow field-flow fractionation with multi-angle light scattering and refractive index detection (AF4–MALS–RI)

The rheological and functional properties of starch are influenced by the size and molar mass distribution of the polymer, the ratio of amylose (AMY) to amylopectin (AMP), and branching characteristics. Asymmetric Flow Field-Flow Fractionation (AF4) was applied to fractionate five different maize hybrids of varying AMY:AMP ratio. When coupled to detection by multi-angle light scattering and refractive index (MALS–RI), it was possible to determine mass percentage and the average weight-average molar mass (M_w) without the need for calibration standards. Sufficient resolution of amylose and amylopectin was achieved by applying a gradient cross-flow on a 17 cm trapezoidal channel with a 350 μm spacer. The observed M_w ranged from about 2 × 10⁵ to 4 × 10⁵ for amylose and from 1 × 10⁸ to 4 × 10⁸ for amylopectin. The corresponding z-average root-mean-square radii (R_z) for AMP ranged from 145 to over 300 nm. Low recoveries from the AF4 channel were found to be due primarily to the focusing step. The calculated mass percent of AMY and AMP from integrated RI peak areas agreed well with nominal values for the individual starch hybrids. Both qualitative and quantitative data were reproducible. The results show the AF4–MALS–RI method to be well suited for routine molecular characterization of starch.     

Starch fine structure and physicochemical properties of specialty rice for canning

The long-grain, specialty rice cultivars, Bolivar, Cheniere, Dixiebelle, and L-205 are used for wet-pack canning. These cultivars have similar apparent amylose content but showed differences in canning, pasting, and gelatinization properties. Starch fine structures were analyzed to rationalize observed differences in functionality. Cheniere amylopectin had the lowest weight-average molar mass (M_w), shortest average chain length (CL), smallest z-average radius of gyration (R_z), lowest proportion of long chains (DP 37–65), and highest polydispersity; while its amylose had the largest M_w and R_z. These structural features were associated with more leached solids in the canning broth, lower volume expansion, lower peak and final viscosity, and lower gelatinization temperature and enthalpy. Bolivar amylopectin had the largest M_w, longest average CL, largest R_z, highest proportion of long chains (DP 25–65), and lowest proportion of short chains (DP 6–12); while its amylose had the smallest M_w and lowest polydispersity. These structures were associated with lower levels of leached solids, higher volume expansion, and higher peak and final viscosity. L-205 was similar to Bolivar in most structural and functional properties; those of Dixiebelle were either comparable to Bolivar or intermediate to Bolivar and Cheniere. These findings point to the importance of the molar mass of amylopectin and the proportion of long and short chains on the canning stability of rice.     

Field assessment of coffee (Coffea arabica L.) cultivars in Meloidogyne exigua-infested or –free fields in Rio de Janeiro State,Brazil

A five-year field assessment of Meloidogyne exigua-susceptible and –resistant coffee cultivars was conducted in two fields, nematode-infested or –free, in Rio de Janeiro State, Brazil. The nematode-susceptible cultivars ‘IAC Catuaí Vermelho 144’, ‘Obatã’ and ‘Tupi’, own-rooted or grafted onto the nematode-resistant ‘IAC Apoatã 2258’, were compared in their vegetative development (plant height, number of plagiotropic branches and collar diameter) and productivity (during four harvests) with the nematode-resistant ‘Acauã’, ‘Catucaí 785/15’ and ‘Iapar 59’. In the infested field, the high nematode population drastically reduced the vegetative development and productivity of all cultivars, regardless of their nematode-resistance. This indicates that measures aimed to reduce the M. exigua population must be taken prior to planting any of the currently available resistant genotypes to avoid enormous yield losses. In the nematode-free field, the susceptible cultivars (own-rooted) achieved higher productivity, followed close by ‘Catucaí 785/15’ and ‘Iapar 59’. Therefore, these M. exigua-resistant cultivars should be recommended for nematode-free areas to prevent severe yield loss in the event of field infestation during the plantation's life span.     

Composition and molecular structure of polysaccharides released from barley endosperm cell walls by sequential extraction with water,malt enzymes,and alkali

Isolated and purified endosperm cell walls (CW), used in this study, were derived from a Canadian malting barley variety, AC Metcalfe, grown in three different environments in Canada in 2003, and varying in grain protein and β-glucan contents, as well as in grain hardness. The CW were initially extracted with water at 45 °C and subsequently digested with barley malt crude enzyme extract resulting in two fractions designated CW-WE45 and CW-MD, respectively. The remaining non-digested cell wall material (CW_ND) was further fractionated by sequential extraction with water at 95 °C (CW_ND-WE95), saturated barium hydroxide (CW_ND-BaE), and 1 N sodium hydroxide (CW_ND-NaE) at 25 °C. Composition and molecular structure analyses were carried out for all fractions including the remaining cell wall residue (CW_RES). Extraction of CW with water followed by digestion with malt crude enzyme extract solubilized the majority of β-glucans (∼55–70%) and glucomannans (∼60–80%) but only a small portion of arabinoxylans (∼20–30%) present in the intact CW. The CW-WE45 and CW_ND-WE95 fractions consisted mostly of β-glucans exhibiting high average molecular weights (M_w) (2–3 × 10⁶), whereas the CW_ND-BaE consisted mainly of arabinoxylans with M_w about 1–1.5 × 10⁶. The CW_ND-NaE contained almost equal amounts of β-glucans and arabinoxylans and a small amount of glucomannans, whereas the CW_RES contained approximately equal proportions of β-glucans, arabinoxylans and glucomannans. β-Glucans in CW_ND-WE95, CW_ND-NaE, and CW_RES exhibited a higher ratio of 3-O-β-d-cellobiosyl-d-glucose to 3-O-β-d-cellotriosyl-d-glucose (DP3/DP4) compared to β-glucans in CW-WE45 and CW-MD. β-Glucans in CW_ND-NaE showed the highest level of long cellulosic oligosaccharides with DP ≥ 5, whereas those in the CW_RES had the highest DP3/DP4 ratio. The CW-MD was fractionated by ultrafiltration into high (CW-MD_HMW) and low-molecular weight (CW-MD_LMW) sub-fractions, with weight-average M_w of ∼150–350 × 10³ and <10 × 10³, respectively, as confirmed by size-exclusion chromatography. The monosaccharide composition of the sub-fractions indicated a more extended enzymic degradation of β-glucans and glucomannans than arabinoxylans. Some differences in composition and molecular structure of the cell wall constituents among the three barley samples were related to their solubility and enzymic digestibility.     

Macromolecular Features of Starches Determined by Aqueous High-performance Size Exclusion Chromatography

Starches from various botanical sources, having different amylose–amylopectin levels, were treated with 95% (v/v) dimethylsulphoxide and then dissolved by microwave heating in a high pressure vessel (MWHPV). This procedure led to an almost complete dissolution of the starch sample when it was subsequently taken up in water. Various treatment times were tested, and optimal conditions corresponded to 35 s heating time in MWHPV (maximum temperature 143 °C). Under these conditions, degradation of the polymers was not noticeable and the degree of solubilisation of starch in the samples was in the range 87 to 100%. High-performance size exclusion chromatography (HPSEC) in tandem with multi-angle laser light scattering and refractive index detection was used to investigate apparent weight-average molar mass ( _w) and z-average gyration radius ( _G) of the starch components. Apparent _wand _Gvalues for samples with different amylose contents (between ≈0 and 65·8%) were between 2·2±0·2×10⁸and 2·4±0·2×10⁷g/mol and between 250±10 and 163±5 nm, respectively. These values were higher than those reported previously^1,2probably due to our more complete but less severe solubilisation procedure. When the heating time was increased from 35 to 90 s (maximum temperature 211°C), the _wand _Gdecreased, demonstrating possible polymer degradation due to temperature. Partial precipitation of high amylose samples after 24 h storage was detected by modifications in chromatograms, compared with freshly prepared samples.     

Efficacy and effects on yield of different fungicides for control of wet bubble disease of mushroom caused by the mycoparasite Mycogone perniciosa

Carbendazim, iprodione, prochloraz-Mn, thiabendazole and thiophanate-methyl were tested in vitro and in vivo for their effect on Mycogone perniciosa, the mycoparasite that causes wet bubble disease of white button mushroom. In vitro experiments showed that prochloraz-Mn (ED₅₀ = 0.006–0.064 μg ml⁻¹) and carbendazim (ED₅₀ = 0.031–0.097 μg ml⁻¹) were the most effective fungicides for inhibiting the mycelial growth of M. perniciosa, while iprodione (ED₅₀ = 1.90–3.80 μg ml⁻¹) was the least effective. The resistance factors calculated for the five fungicides were between 1.4 and 2. The results obtained suggest that there is very little risk that M. perniciosa will develop resistance to the fungicides assayed. The in vivo efficacy of fungicides for control of wet bubble was studied in two mushroom cropping experiments, which were artificially infected with two doses of M. perniciosa, 10⁶ and 10⁷ spores m⁻², respectively. There was, in the low dose inoculum experiment, a very high degree of effectiveness (96.5–100.0%) with all the fungicides assayed. However, iprodione performed poorly (20.5–24.4%) compared with the other fungicides (88.7–100.0%) in the high concentration inoculum experiment. The most effective treatments for controlling wet bubble did not improve the biological efficiency of Agaricus bisporus.     

Improvement of Hanseniaspora uvarum biocontrol activity against gray mold by the addition of ammonium molybdate and the possible mechanisms involved

The efficacy of Hanseniaspora uvarum against gray mold by adding ammonium molybdate (NH₄–Mo) and the mode of actions were evaluated. The results showed that H. uvarum at 1 × 10⁶ CFU ml⁻¹ plus 1 mmol l⁻¹ NH₄–Mo greatly reduced gray mold in grape fruits. NH₄–Mo at concentrations of 1, 5, 10 and 15 mmol l⁻¹ significantly inhibited spore germination and mycelium growth of Botrytis cinerea. Population growth of H. uvarum was markedly inhibited by NH₄–Mo at 5 mmol l⁻¹in vitro and not affected by addition of NH₄–Mo at 1 and 5 mmol l⁻¹ in wounds combination of NH₄–Mo and H. uvarum induced higher activities of peroxidase (POD), polyphenoloxidase (PPO), phenylalanine ammonialyase (PAL), superoxide dismutase (SOD), catalase (CAT) and β-1,3-Glucanase than individual application of H. uvarum or NH₄–Mo. The enhancement of disease control may be directly because of the inhibitory effects of NH₄–Mo on spore germination and mycelial growth of B. cinerea in vitro, and indirectly because of the induced defense reactions by NH₄–Mo in grape berries.     

Einige physikochemische Eigenschaften des Kartoffel-virus M

Zusammenfassung Die Sedimentationskonstante S _20.w ^° des Kartoffelvirus M (KVM) betr?gt 167±1 S. Die Konzentrationsabh?ngigkeit ergibt sich aus der Beziehung s _20.w ^c =(167−33×c) S. Die Schwebedichte des KVM in C?siumchlorid (⌕ _C5C1 ²⁵ ) betr?gt 1,321 bis 1,322 g/ml. Mit Hilfe der SDS-Polyacrylamid-Gelektrophorese fanden wir zwei Proteine mit Molekülmassen von 35 700 und 33 000 Dalton. Die Nukleins?ure des KVM ist eine einstr?ngige RNS mit einer Molekülmasse von 2,38×10⁶ Dalton (nicht denaturierende Bedingungen) bzw. 2,14×10⁶ Dalton (nach Formaldehydbehandlung). Damit ist das KVM ein typischer Vertreter der Carlavirus-Gruppe.

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Summary Particles of potato virus M (PVM) were purified by the method of Proll & Richter (1979). After sugar density gradient centrifugation, preparations had a high level of purity and were homogeneous when examined under the electron microscope and in the analytical ultra-centrifuge. The sedimentation constant of particles (s°) is 167±1 S and the concentration relation s _20.w ^c =(167−33×c)S, where c is in mg/ml. The density of the PVM particles in caesium chloride (⌕ _C5C1 ²⁵ ) is 1.321 to 1.322 g/ml, with tobacco mosaic virus particles (density=1.325 g/ml) as a standard. In SDS-polyacrylamide gel electrophoresis, PVM protein sub-units migrated as two compounds with apparent sizes of 35 700 and 33 000 daltons, respectively. PVM nucleic acid is single stranded RNA, as shown by its positive orcinol and negative diphenylamine reactions, its degradation by RNase and its temperature melting curve. The RNA comprised 5.4% of the particle weight and its estimated molecule size was 2.38×10⁶ daltons (undenatured) and 2.14×10⁶ daltons (treated with formaldehyde). Physicochemical data on PVM are summarized in Table 1. The cryptogram of PVM is R/1: 2.4/5.4: E/E: S/Ap, carlavirus group.

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Résumé é virus M de la pomme de terre (PVM) a été urifié selon la méthode Proll & Richter 979). Après deux centrifugations selon la chnique du gradient de sucrose, nous avons btenu des préparations purifiées qui se sont firmées très homogènes au microscope ectronique, ainsi qu’avec l’ultracentrifugeuse analytique. Nous avons observé un effet de concentration de la valeur S et avons éterminé la constante de sédimentation (s^O) à aide de distribution de S dans une zone de concentration de 0,5 à 0,1 mg de virus/ml à 57±1 S. L’effet de concentration peut être obtenu ar la relation s _20.w ^c =(167−33×c)S, dont c at à utiliser en mg/ml. La densité spécifiquedu PVM dans le aloride de césium (⌕ _C5C1 ²⁵ ) est de 1,321 à 322 g/ml avec le virus de la mosa?que du abac comme marqueur, dont la densité est de 1,325 g/ml. Les masses moléculaires des capsomers ont été déterminées à l’aide de la SDS-polyacrylamide-gel-electrophorèse. Nous avons observé deux zones de protéines dont la masse moléculaire calculée fut de 35 700 et 33 000 dalton. L’acide nucléique du PVM comprend une spirale ARN; ceci a été obtenu avec la réaction positive d’orcine, des essais de catabolisme avec la RNase et de la courbe de fusion. Le poids représente 5,4 % de celui de la particule. La masse moléculaire est de 2,38×10⁶ dalton (conditions non dénaturantes) 2,38×10⁶ (après traitement au formaldéhyde). Dans le tableau 1 sont résumées les données physicochimiques du PVM selon Proll & Richter (1979). Le cryptogramme suivant a été obtenu: R/1: 2,4/5,4: E/E: S/Ap, ce qui permet de classer ce virus dans le groupe Carla.

     

Reduced height alleles (Rht) and Hagberg falling number of wheat

Near-isogenic lines varying for alleles for reduced height (Rht) and photoperiod insensitivity (Ppd-D1) in cv. Mercia (2005/6–2010/11; rht (tall), Rht-B1b, Rht-D1b, Rht-B1c, Rht8c+Ppd-D1a, Rht-D1c, Rht12) and cvs Maris Huntsman and Maris Widgeon (2007/8–2010/11; rht (tall), Rht-B1b, Rht-D1b, Rht-B1c, Rht-B1b+Rht-D1b, Rht-D1b+Rht-B1c) were compared at one field site, but within different systems (‘organic’, O, 2005/6–2007/8 v. ‘intensive’, I, 2005/6–2010/11). Further experiments at the site (2006/7–2008/9) compared 64 lines of a doubled-haploid (DH) population [Savannah (Rht-D1b) × Renesansa (Rht-8c+Ppd-D1a)]. Gibberellin (GA) insensitive dwarfing alleles (Rht-B1b; Rht-B1c; Rht-D1b; Rht-D1c) could reduce α-amylase activity and/or increase Hagberg falling number (HFN) but effects depended greatly on system, background and season. Only Rht-B1c increased grain dormancy despite producing plants taller than Rht-D1c. The GA-sensitive Rht8c+Ppd-D1a in Mercia was associated with reduced HFN but analysis of the DH population suggested this was more closely linked with Ppd-D1a, rather than Rht8c. The GA-sensitive severe-dwarfing allele Rht12 was associated with reduced HFN. Instability in HFN over season tended to increase with degree of dwarfing. There was a negative association between mean grain weight and HFN that was in addition to effects of Rht and Ppd-D1 allele.     

Lateral growth of a wheat dough disk under various growth conditions

Numerous studies have tried to understand and model bubble growth inside dough. Experimental studies are inconvenienced by the methods’ inability to capture the dynamic phenomena. In this paper, a versatile experimental method was developed to allow for macroscopic expansion of wheat dough. The study evaluates expansion of a dough disk under varying: moisture content (40, 41, 42, 43, and 44% wb), leavening acid concentration (30, 40, and 50% db), pressure schemas, pressurizing gas (compressed air and CO₂), and lubrication (Teflon^® film coating and Pam^® aerosol lubricant). Dough expansion increased 22.6% by increasing moisture content from 40 to 44%. Increased baking powder formulation (40% db) was used to enhance initial growth conditions and CO₂ production. ‘Pressure pulse’ and ‘pressure vacuum methods’ added pressurization alternatively with full vacuum. The former method included a rest period before vacuum application, and increased expansion by 10.8%. Teflon^® and Pam^® reduced friction between the dough and acrylic plate and increased the final expansion by 14.7% compared to no lubricant following the ‘standard pressurization method’. ‘Pressure pulse’ and ‘pressure vacuum’ experiments decreased expansion by 28.4 and 38.2%, respectively compared to ‘standard pressurization’ while using Teflon^® and Pam^®.     

Partial-degradation and heat-moisture dual modification on the enzymatic resistance and boiling-stable resistant starch content of corn starches

Normal corn, Hylon V and Hylon VII starches were partially degraded by acid-ethanol treatment and applied to heat-moisture treatment (HMT) for improving the enzymatic resistance of starch. The weight-average degree of polymerization (DP_w) of acid-ethanol-treated (AET) corn starches ranged from 6.75 × 10⁵ to 181, 4.48 × 10⁵ to 121, and 1.94 × 10⁵ to 111 anhydrous glucose units for normal corn, Hylon V and Hylon VII starches, respectively. Starch retained its granular structure after AET and HMT, recovery of starch granules after modifications were higher than 92%. Resistant starch (RS) content and boiling-stable RS content of corn starch increased after dual modification, and the increment increased with increasing duration of AET. The boiling-stable RS content of dual-modified starch increased from 1.5 to 9.2, 12.2 to 24.1, and 18.0 to 36.2% for normal corn, Hylon V and Hylon VII starches, respectively. Increments of RS content and boiling-stable RS content of dual-modified starches were significantly correlated (r² > 0.700) with DP_w of starch, revealing that the enzymatic resistance of dual-modified corn starch granules increased with decreasing molecular size of starch. Result also suggested that starch granules partially degraded with AET could improve the molecular mobility and ordering during the consequent HMT.     

Biodegradable foam tray from cassava starch blended with natural fiber and chitosan

This work developed biodegradable foam trays from cassava starch blended with the natural polymers of fiber and chitosan. The kraft fiber at 0, 10, 20, 30 and 40% (w/w of starch) was mixed with cassava starch solution. Chitosan solution at 0, 2, 4 and 6% (w/v) was added into starch/fiber batter with 1:1. Hot mold baking was used to develop the cassava starch-based foam by using an oven machine with controlled temperature at 250 °C for 5 min. Results showed that foam produced from cassava starch with 30% kraft fiber and 4% chitosan had properties similar to polystyrene foam. Color as L^*, a^* and b^* value of starch foam tray was slightly increased. Density, tensile strength and elongation of the starch-based foam were 0.14 g/cm³, 944.40 kPa and 2.43%, respectively, but water absorption index (WAI) and water solubility index (WSI) were greater than the polystyrene foam.     

Pre-harvest glyphosate application effects on properties of β-glucan from oat groats

Pre-harvest glyphosate is applied to cereal grains to control weed growth. However, it has been claimed that oat (Avena sativa L.) composition is affected by pre-harvest glyphosate application. The research was conducted to evaluate differences in properties of β-glucan in grains of pre-harvest glyphosate treated versus untreated oat plants. Two oat cultivars (Rockford and Souris) were grown at Minot and Prosper, ND, in 2015, and glyphosate was sprayed during the soft dough stage, hard dough stage, or not applied. β-glucan viscosity was not significantly (p > 0.05) affected by treatment at soft dough (1082 cP) or mature (1166 cP) stages compared with untreated (1150 cP) controls. Applying glyphosate at the soft dough stage significantly (p < 0.05) reduced the content and solubility of the β-glucan versus untreated samples. β-glucan content and solubility in oat treated at soft dough were 4.35% and 52.1%, respectively, while in untreated samples were 4.65% and 60.6%, respectively. Treatment at soft dough and hard dough stages significantly (p < 0.05) increased weight average molecular weight (M_w) of the high molecular weight fraction of soluble β-glucan (4.4 × 10⁶ and 3.8 × 10⁶, respectively), compared with untreated controls (3.5 × 10⁶). The M_w of the low molecular weight fraction of soluble β-glucan fraction significantly (p < 0.05) increased at soft and hard dough treatments (5.5 × 10⁵ and 3.3 × 10⁵, respectively), versus untreated samples (3.0 × 10⁵). Therefore, glyphosate can be applied when the grain has reached physiological maturity or thereafter.     

Expansion profiles of wheat doughs fermented by seven commercial baker's yeasts

Commercial baker's yeast consists of Saccharomyces cerevisae, however the strain can vary in each baker's yeast, which might influence the dough fermentation time. The scope of this research was to investigate the dough expansion of wheat doughs fermented by seven commercial baker's yeasts at different yeast concentrations (2.88·10¹¹, 5.76·10¹¹ and 8.64·10¹¹ colony forming units/kg flour) and fermentation temperatures (5 °C, 15 °C, 25 °C and 35 °C). Dough expansion was investigated by monitoring the dough height and it was found to be described well by a first order kinetic model. Doughs fermented with four of the seven yeasts generally had higher kinetic rate constants and hence shorter fermentation times compared to fermentation with the other three yeasts. The shortest fermentation times were found for doughs fermented at 25 °C and the highest yeast concentration, a trend found for all the yeasts tested. The differences in the kinetic rate constants indicate a differentiation in yeast strain among the commercial baker's yeasts emphasising the great importance of the choice of baker's yeast for the dough fermentation time.     

The oxygen uptake,in air and in 5% O2, and the carbon dioxide output,of stored potato tubers

Summary Oxygen uptake at harvest varied from c. 40 ml kg⁻¹h⁻¹ at 10°C, in very immature, to c. 3–5 ml kg⁻¹h⁻¹ in mature tubers. The O₂ status of the tuber normally would allow uptake by a low-affinity oxidase (K _m =1.5×10⁻⁴ M) as well as by cytochrome-c-oxidase (suggestedK _m =7×10⁻⁸ M). Separation was attempted by measuring uptake in air and 5% O₂, oxygen status being derived from internal atmosphere analyses or periderm permeability. At harvest, low-affinity uptake was probably c. 20–30% of the total in mature and tentatively c. 10% in immature tubers. it fell almost to zero and then re-appeared during storage. Total uptake fell to c. 1.5–2.5 ml kg⁻¹h⁻¹ at 10°C, irrespective of maturity, then rose during sprout growth. The mid-storage temperature-coefficient, 20°C/10°C, was c. 1.2–1.3, but uptake at 2°C (sweetened tubers) could be higher than at 20°C. Later, increased respiration accompanying sprouting changed this pattern. CO₂ production was on average similar to O₂ uptake but at certain periods diverged. This is discussed. It also showed a delayed response to changed conditions with consequent temporarily aberrant RQ's.

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Zusammenfassung Die Atmung von unreifen Knollen wurde w?hrend der Lagerung bei 10°C über fünf Lagerperioden sowie bei 2 und 20°C für eine Periode studiert. Die Aufnahme von Sauerstoff im Zeitpunkt der Ernte schwankte zwischen ca. 40 ml kg⁻¹h⁻¹ bei 10°C in sehr unreifen und ca. 3–5 ml kg⁻¹h⁻¹ in reifen Knollen. In früheren Arbeiten wurde im Knollensaft eine Sauerstoffkonzentration zwischen 3.2×10⁻⁴ M bei 5°C und 2×10⁻⁵ M bei 37°C festgestellt (siehe auch Tabellen 4 und 5). Dies würde bedeuten, dass bei normalen Lagertemperaturen ein Endoxydationssystem mitK _m =1.5×10⁻⁴ M, wie früher angenommen, f?hig w?re, sich zu einem betr?chtlichen Teil seiner H?chstrate mit Sauerstoff, zus?tzlich zu der Sauerstoffaufnahme durch Cytochrom-c-Oxydase, zu verbinden. Hierfür wirdK _m =7×10⁻⁸ M auf der Rechnungsbasis früherer Ergebnisse angenommen. Die Trennung des Oxydase-Systems mit geringer von jenem mit hoher Affinit?t wurde durch Messung der Sauerstoffaufnahme in Luft und in 5% O₂ vorgenommen; der Sauerstoffstatus für ?hnliche Knollenmuster wurde durch Messungen der Zusammenh?nge der inneren Atmosph?re oder der Periderm-Durchl?ssigkeit errechnet. Bei der Ernte betrug die Aufnahme bei geringer Affinit?t wahrscheinlich 20–30% des Totals in reifen Knollen (Tabelle 1) und, versuchsweise, ca. 10% in unreifen Knollen (Tabelle 3), obwohl sie kurz nach der Ernte wahrscheinlich über 25% in unreifen Knollen ausmachte (Tabelle 2). Die Ursache des sehr starken Rückganges in der Sauerstoffaufnahme bei unreifen Knollen unmittelbar nach der Ernte lag beim fast vollst?ndigen Rückgang der Aufnahme von Cytochrom-c-Oxydase (das heisst Aufnahme in 5% O₂—Tabelle 3). Sp?ter jedoch, w?hrend der Lagerung, fiel die Aufnahme bei geringer Affinit?t fast auf Null (Abb. 2 und 3), obwohl sie w?hrend des Keimwachstums wieder einsetzte. Die Gesamtaufnahme war also in der Mitte der Lagerungsperiode unbeeinflusst durch die Ver?nderungen im Sauerstoffverh?ltnis im Bereich 5–100% O₂, obwohl sie zu Beginn und am Ende der Lagerung beeinflusst war (Tabelle 6). Die Gesammtaufnahme fiel, unabh?ngig von der Reife, auf ein Minimum von ca. 1,5 bis 2,5 ml kg⁻¹h⁻¹ vor Beginn des Keimwachstums und stieg dann wieder w?hrend des Aufwuchses (Abb. 2 und 3). Die oben beschriebenen, übereinstimmenden Trends wurden durch kurze Schwankungen in der Aufnahme bis zum Ausmass von ungef?hr ±10% des mittleren Wertes bei nicht bewegten Knollen überlagert, aber Manipulation der Knollen k?nnte bedeutende Erh?hungen in der Aufnahme verursachen, besonders wenn die Knollen welk sind (Abb. 1). Die Erzeugung von Kohlendioxyd war im Mittel gleich wie dei Sauerstoffaufnahme, aber in gewissen Perioden wich sie konsequent ab (siehe zum Beispiel Abb. 3, 20°C). M?gliche, darin verwickelte Mechanismen wurden in Betracht gezogen. Es ergab sich auch eine Versp?tung von mehreren Studen als Reaktion auf ver?nderte Bedingungen mit nachfolgend zeitweilig abweichenden RQ's. Der für die Mitte der Lagerungszeit gültige Koeffizient für die Temperatur 20°C/10°C betrug 1,2–1,3 (Tabelle 8), aber Aufnahme bei 2°C (süsse Knollen) konnte h?her sein als bei 20°C. Die die Keimung—früher und kr?ftiger bei 20°C als bei 10°C—begleitende Atmung ?nderte sp?ter dieses Bild, und der Koeffizient für die Temperatur 20°C/10°C war über 3 (Tabelle 8). W?hrend der ersten zwei Wochen der Lagerung bei 2°C stieg die Atmung merklich an und fiel dann wieder (Abb. 3 und 4) trotz der Tatsache, dass der Gehalt sowohl an Saccharose wie an reduzierenden Zuckern für einige Zeit weiter anstieg (Tabelle 7)—Atmung ist ein Index für den Umsatz, der nicht notwendigerweise mit dem Zuckergehalt in Beziehung steht. Es gab einen Hinweise auf die ?nderung im Grad, bis zu welchem die Aufnahme bei geringer Affinit?t zu der anf?nglichen Erh?hung in der Sauerstoffaufnahme bei 2°C beitrug, von der vollst?ndigen Abwesenheit in Knollen, die unmittelbar nach der Ernte bei 2°C gelagert wurden (Abb. 3) bis zur gr?ssten Mitwirkung in Knollen, die einige Monate nach der Ernte zwischen 2°C und 10°C gelagert wurden (Abb. 4). Wenn süsse Knollen nach Lagerung bei 2°C wieder bei 10°C aufgestellt wurden, stieg die Sauerstoffaufnahme sofort zu einem H?chstwert an (ungef?hr das Doppelte vom Wert bei 2°C; Abb. 4), gefolgt von einem Rückgang.

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Résumé L'auteur a observé la respiration de tubercules immatures et m?rs au cours de la conservation, à 10°C pendant cinq saisons, et à 2 et 20°C pendant une saison. L'absorption d'oxygène à la récolte varie de c. 40 ml kg⁻¹h⁻¹ à 10°C dans les tubercules très immatures à c. 3–5 ml kg⁻¹h⁻¹ dans les tubercules m?rs. Une étude précédente a montré une concentration en oxygène dans le jus de tubercule allant de 3,2×10⁻⁴ M à 5°C jusque 2×10⁻⁵ M à 37°C (voir aussi les tableaux 4 et 5). Ceci indiquerait que, à des températures normales de conservation, un système final d'oxydase avecK _m =1,5×10⁻⁴ M, comme il a été précédement proposé, serait capable de combinaison avec l'oxygène dans une proportion appréciable de sa proportion maximale, en addition à l'absorption d'oxygène par le cytochrome-c-oxydase. Pour celuici,K _m =7×10⁻¹ M est proposé sur la base de calculs à partir des résultats antérieurs. La séparation entre les systèmes d'oxydase de basse et de haute affinité est tentée par mensuration de l'absorption d'oxygène dans l'air et dans 5% O₂, les situations en oxygène étant calculées sur des échantillons semblables de tubercules à partir de mesures de la composition de l'atmosphère interne ou de la perméabilité du périderme. A la récolte, le prélèvement par le système de basse affinité était probablement de c. 20–30% du total chez les tubercules m?rs (tableau 1) et de c. 10%, déterminé expérimentalement chez les tubercules immatures (tableau 3), quoique peu après la récolte, il était probablement supérieur à 25% chez les tubercules immatures (tableau 2). La chute très rapide, immédiatement après la récolte de l'absorption d'oxygène chez les tubercules immatures est due en presque totalité à la chute du prélèvement par le cytochrome-c-oxydase (voir prélèvement dans 5% O₂—tableau 3). Plus tard cependant, le prélèvement par le système de basse affinité tombe presque à zéro pendant la conservation (fig. 2 et 3), quoiqu'il réapparaise au cours du développement des germes. Par conséquent l'absorption totale n'est pas affectée par les modifications dans la tension de l'oxygène, dans les limites 5–100% O₂, dans le milieu de la période de conservation bien qu'il soit affecté au commencement et à la fin de la saison (tableau 6). L'absorption totale tombe à un minimum de c. 1.5 à 2.5 ml kg⁻¹ h⁻¹, indépendamment de la maturité, avant le début de la croissance des germes (fig. 2 et 3). Se situant au-dessus des tendances manifestes décrites ci-dessus, des fluctuations de courtterme apparaissent dans l'absorption dans une mesure de quelque ±10% de la valeur moyenne dans les tubercules non remués, mais les manipulations sont susceptibles de provoquer des augmentations marquées de l'absorption, particulièrement lorsque les tubercules sont flétris (fig. 1). La production d'anhydride carbonique est, en moyenne, correspondante à l'absorption d'oxygène quoique, à certaines périodes, elle s'en écarte considérablement (voir par ex. fig. 3, 20°C). L'auteur considère différents mécanismes possibles impliqués dans ces phénomènes. L'étude montre aussi un retard de plusieurs heures dans la réaction aux changements de conditions, avec comme conséquence un co?fficient RQ's temporairement aberrant. Au milieu de la période de stockage, le co?fficient de température 20°C/10°C est c. 1.2–1.3 (tableau 8). Mais le prélèvement à 2°C (tubercules affadis) pourrait être plus élevé qu'à 20°C. Ultérieurement, la respiration accélérée accompagnant la germination, plus précoce et plus active à 20° qu'à 10°, modifie cet aspect et le co?fficient de température 20°C/10°C est une excès de 3 (tableau 8). Durant les deux premières semaines de conservation à 2°C, la respiration slélève remarquablement et tombe ensuite de nouveau (fig. 3 et 4) en dépit du fait que les teneurs aussibien en sucrose qu'en sucres réducteurs continuent à s'élever pendant quelque temps (tableau 7), la respiration étant l'indication du renversement, qui n'est pas nécessairement lié au niveau des sucres. Une indication se révèle du changement dans le degré auquel le système d'absorption de basse affinité contribue à l'accroissement initial de l'absorption d'oxygène à 2; C, à partir de l'absence complète d'absorption dans les tubercules placés à 2°C immédiatement après la récolte (fig. 3), jusqu'à la participation majeure dans les tubercules placés à 2°C après avoir été à 10°C plusieurs mois après la recolte (fig. 4). Si les tubercules affadis sont placés de nouveau à 10°C, venant de 2°C, il se produit une élévation immédiate de l'absorption de l'oxygène jusqu'à une valeur de pointe qui est approximativement double de celle à 2°C (fig. 4) qui est suivie par une chute.

     

Physico-chemical Characteristics as Indicators of Starch Availability from Milled Rice

The hypothesis was tested that certain physico-chemical characteristics might be used as indicators of total starch availability and rate of starch availability of milled rice. Milled unparboiled (uPB) and parboiled (PB) rice samples (n=93) were characterized using standardized methods of physical tests and chemical analyses and anin vitromethod was used for measuring the rate of starch digestion on a subsample of rice (n=26). The rice varieties were dominated by medium long, bold rice grain with high amylose rice and intermediate gelatinization temperature (GT), but a wide range in all characteristics was measured. Small amounts of resistant starch (RS) were measured in the cooked rice, indicating virtually complete starch availability. The RS of PB rice (0·4 g/100 g rice as eaten) was significantly (P<0·004) higher than the RS of uPB rice (0·1 g/100 g) however. The rate of starch digestion was significantly affected by both variety and parboiling. The starch digestion index (SDI) values of the PB samples (mean value 73·7) were significantly (P<0·001) lower than those of the uPB samples (mean value 79·0). The apparent amylose content (AC) was the strongest determinant for SDI in both uPB and PB rice. The widths and shapes of the raw grains and the elongation after cooking were correlated significantly with SDI values for the uPB rice, while the relatively mild parboiling procedure followed in this study eliminated this correlation. The minimum cooking times were correlated significantly with the SDI values in the uPB samples.     

Survey of amylose content in Secale cereale, triticum monococcum, T. turgidum and T. tauschii

A standard method for determining apparent amylose content was modified for use with samples of 2–3 cereal seeds. Starch was extracted by soaking the seeds overnight in dilute ammonia solution, grinding in NaCl solution in a microfuge tube with an appropriate pestle and decanting the starch slurry. The starch was then washed successively in acetic acid, ethanol and acetone. The amylose content was determined by dispersing 5·0 mg of the starch in ethanol, adding NaOH solution, heating until a clear gel was formed, diluting, neutralising with citric acid, staining with iodine and reading in a spectrophotometer at 620 nm. The method provided a very strong correlation with a standard method for much larger samples. The apparent amylose content was determined for 1083 accessions of Triticum monococcum (einkorn), T. turgidum (emmer), T. tauschii and Secale cereale (rye). The 10 extreme accessions of each species were re-analysed a further three times and the two most extreme individual lines were selected for genetic studies. Apparent amylose content of T. monococcum ranged from 15 to 28%; that of T. turgidum, 19–31%; T. tauschii, 21–34%; and rye 12–28%. These ranges are considered sufficiently broad to allow amylose content to be further diversified through breeding.     

Aroma profiles of the curry leaf, Murraya koenigii (L.) Spreng. chemotypes: Variability in north India during the year

Murraya koenigii (L.) Spreng. (Rutaceae) is characterized by a large chemical intraspecific variability among the land races. This fact makes it difficult to detect real changes occurring in their essential oil composition during annual cycle. Based on this, variations of essential oil yield and composition in two chemotypes (‘A’ and ‘B’) of M. koenigii were assessed in spring, summer, rainy, autumn and winter seasons under foot hill conditions of northern India. The essential oil yield ranged from 0.15% to 0.18% in chemotype ‘A’, while it varied from 0.12% to 0.14% in chemotype ‘B’. Essential oils of both chemotypes from different seasons were analysed by gas chromatography (GC-FID) and gas chromatography-mass spectrometry (GC-MS). A total of fifty-eight constituents representing 93.7-98.8% of chemotype ‘A’ and fifty-six constituents forming 96.1-98.7% of the total composition of chemotype ‘B’ were identified. Chemotype ‘A’ was characterized by higher percentages of α-pinene (34.6-41.9%), sabinene (26.1-36.1%), (E)-caryophyllene (2.4-5.4%) and terpinen-4-ol (1.5-5.3%), whereas chemotype ‘B’ was dominated by higher amount of α-pinene (52.7-65.3%), β-pinene (10.7-12.9%), (E)-caryophyllene (3.1-10.3%) and limonene (5.1-7.8%). Comparative results showed considerable variations in the essential oil composition of both chemotypes due to season of collection. Present study concluded that the M. koenigii leaves of desired quality may be obtained by selecting suitable chemotype and season.     

Physicochemical Studies on Resistant StarchIn VitroandIn Vivo

Resistant starch (RS), producedin vitroby hydrolysis of retrograded pea starch gels and amylose gels by porcine pancreaticalpha-amylase, was characterised by X-ray diffraction, size exclusion chromatography and methylation analysis. These techniques showed that RSin vitroconsisted of semi-crystalline, mostly linear material that was present in two main molecular size subfractions (DP_n>100 andDP_n20–30) with a third, minor subfraction (DP_n≤5). The extent of retrogradation of amylose was found to be of primary importance in determining the RS content of starch. Analysis ofin vivoRS, recovered during an ileostomy study, produced results that were similar to those obtained from RSin vitro. Anin vitromodel for the structure of resistant starch is proposed.     

Retrogradation and Gel Textural Attributes of Corn Starch Amylose and Amylopectin Fractions

An understanding of relationships between starch molecular structure and function could increase the opportunity to develop additional uses for starch. Using a combined aqueous (aq.) leaching and alcohol precipitation technique, six amylose fractions were obtained from regular and two high amylose (hAM) corn starches (50 and 70%). Five amylopectin fractions were obtained from regular and waxy corn starches. After freeze-drying the fractions, high performance size exclusion chromatography (HPSEC) was used to estimate weight-average (M_w) and number-average (M_n) molecular weights, and to determine polydispersity (M_w/M_n) and purity. Increase in fraction reducing power after pullulanase treatment was determined and expressed as a relative index of branching. Amylose-fractions showed varying but similar (P>0·05) M_w(1·40–5·68E+05), similar polydispersities (2·1–2·9), and branching values (1·93E-04–4·14E-05). Amylose branching increased with decreasing M_w. Amylopectin had varying M_w(2·88–5·43E+07) and similar polydispersities (1·3–1·5), but different branching values (7·30E-04–1·54E-03), that did not follow any M_worder. Fraction melting temperatures, enthalpies, and gel retrogradation behaviours were determined using differential scanning calorimetry (DSC). No enthalpies were observed for amylose fractions. Amylopectin fractions with high branching values that had intermediate to low M_w(3·75–2·88E+07), showed marked retrogradation. Enthalpy was correlated neither to branching nor M_w. Gel textural profile analysis (fracturability, adhesive force, cohesiveness, and springiness) showed that for amylose, intermediate M_wfractions promoted less fracturability, while adhesive force, and stringiness increased with a decrease in M_w. For amylopectin, the intermediate M_wand highly branched fractions reduced fracturability, and promoted adhesive force, and stringiness. Amylopectin fractions of intermediate M_wand high extent of branching underwent increased retrogradation. Amylose gel textural attributes were governed by molecular weight, while molecular weight and branching governed amylopectin gel textural properties.