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1.
Controlled environments were used to define the manner in which temperature, water and fertilizer affect the timing of key transition points during grain development and to investigate the effects of combined environmental factors in a US spring wheat (Triticum aestivum (L.)). When plants were subjected to very high temperature regimens (37/17  or 37/28 °C day/night) during grain development, the times to maximum kernel water content, maximum dry weight and harvest maturity were shorter than in plants maintained under a 24/17 °C day/night regimen. Starch accumulated at similar rates, but the onset and cessation of starch accumulation occurred earlier. Apoptosis in endosperm tissue also occurred earlier under high temperatures and coincided with physiological maturity. The addition of drought to the 37/17 °C regimen further shortened the time to maximum water content and dry weight and reduced the duration of starch accumulation, but did not influence the timing of protein accumulation or kernel desiccation. Post-anthesis fertilizer had little effect on time to maximum water content, dry weight, apoptosis, or harvest maturity under any of the temperature regimens and did not influence the timing of starch accumulation. However, both the rate and duration of protein accumulation were reduced when post-anthesis fertilizer was omitted.  相似文献   

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《Field Crops Research》2006,96(1):48-62
In order to quantify the effects, at different stages during grain filling, of alternating day/night high temperature regimes on sunflower grain yield and quality, heads were exposed to high temperatures during 7 or 6 days starting either 10–12 days after anthesis (daa, HT1), 18 daa (HT2) or 24 daa (HT3). Also, heads were exposed to high temperatures for periods of 2, 4 or 6 days in each of HT1 and HT2. Temperatures covered a range of mean daily grain temperature of 20–40 °C and peak grain temperatures (i.e., those prevailing during the central 5 h of the daylight period) of 26–45 °C. High temperature stress for periods of 4 days or longer produced significant (p < 0.05) reductions in grain yield and grain quality. Early (HT1) exposure to stress reduced yield by 6%/°C above a mean grain temperature threshold of 29 °C; later (HT2 + HT3) exposures reduced yield by 4%/°C above a threshold of 33 °C. These reductions in yield were attributable to reductions in unit grain weight at all positions (periphery, intermediate, central) on the head, and an increase in the proportion of very small (10–30 mg) grains, termed half-full (HF) grains in this paper. In both full and HF grains, stress in either HT1 or HT2 reduced final pericarp weight, associated with fewer number of cell layers and thinner cell walls in the schlerenchyma. High temperatures reduced both the rate and duration of oil deposition in the grain, with the greatest effects being found with early (HT1) exposures. The unsaturation (oleic acid/linoleic acid) ratio of oil from mature grain was altered only when exposure to heat stress overlapped with the cessation of deposition of storage lipids. The effects of duration and intensity of heat stress on relative (to control) grain yield and oil content could be reasonably summarized using a linear response to cumulative hourly heat load calculated with a base temperature of 30 °C. We conclude that: (i) 4 days of alternating day/night temperatures resulting in mean daily grain temperatures of >30 °C can reduce sunflower grain yield and quality; (ii) the magnitude of these effects is strongly dependent on the timing of exposure and their nature on the grain growth processes active at the time of stress; and (iii) an hourly heat load (base = 30 °C) provides a useful integrative estimator of the effects of exposure to heat stress on grain yield and oil content for a given phase of grain filling.  相似文献   

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Various post-harvest processes of rice are commonly employed, especially during the off-season, to ensure its consumption feasibility, which often affect the grain quality. Different forms of drying, storage and processing of rice are evaluated to identify their effects on grain quality. Microwave drying has emerged as an alternative to the widely-used intermittent-drying and fixed-bed-dryer methods of drying paddy rice. Control of drying-air temperatures (between 40 °C and 60 °C) according to the rice variety can improve quality, especially for exotic varieties. Keeping stored grain in hygroscopic balance, with water content between 11% to 15%, at temperatures between 16 °C and 20 °C and with intergranular relative humidity near 60%, allows 12 months of storage in a controlled environment without significant deterioration. Other innovations, notably the application of artificial refrigeration to grain stored in bulk in vertical cylindrical silos and the use of impermeable packaging for storage, ensure the conservation of grain mass. The different stages and equipments used to obtain polished, brown and parboiled rice result in significant changes in the nutritional value of rice because of the removal of the outermost layers of the grains. Polishing reduces the nutritional value and physical homogeneity of rice. Brown rice retains more bioactive compounds and nutrients because it does not lose the outer layer of the grains in the polishing processes. Parboiled rice, although less nutritious than brown rice, has better grain integrity and milling yield and less loss of nutrients than white rice.  相似文献   

7.
Lesquerella is a developing hydroxy oilseed crop suitable for rotation in the arid Southwestern United States. The hydroxy oil of lesquerella makes it suitable for esterification into triglyceride estolides. The estolide functionality imparts unique physical properties that make this class of materials suitable for functional fluid applications. Lesquerella and castor hydroxy triglycerides were converted to their corresponding estolides by reacting the oils with saturated fatty acids (C2–C18) in the presence of a tin 2-ethylhexanoate catalyst (0.1 wt.%) and utilizing the condensation of hydroxy with corresponding anhydride or heating under vacuum at 200 °C. Two homologous series of estolides for each triglyceride were synthesized for comparison, mono-capped (one hydroxy functionality per triglyceride molecule) and full-capped (all hydroxy functionalities per triglyceride molecule). Physical properties (pour point, cloud point, viscosity, and oxidative stability) were compared for this estolide series. The longer chain saturate capped estolides (C14–C18) had the highest pour points for both mono-capped (9 °C, C18:0) and full-capped (24 °C, C18:0) lesquerella estolides. Castor mono-capped (9 °C) and full-capped (18 °C) triglyceride estolides gave similar properties. However, pour points improved linearly when the shorter saturated fatty acid capping chain lengths were esterified with the hydroxy triglycerides. Lesquerella capped with a C6:0 fatty acid had pour points of −33 °C for the mono-capped and −36 °C for the full-capped and castor had −36 and −45 °C, respectively. Oxidative stabilities of the estolides were compared for oleic, lauric and lauric-hydrogenated mono- and full-capped materials by rotating bomb oxygen test (RBOT). RBOT times for oleic and lauric capped estolides were low and similar with times centered around 15 min. However, when antioxidant (4 wt.%) was added the RBOT times increased to 688 min for the hydrogenated full-capped lesquerella lauric estolide. The antioxidant had little effect on RBOT times when 2 wt.% or less antioxidant was added for all the estolides except those that were hydrogenated. The hydrogenated estolides showed improvements in oxidative stability at all concentrations of antioxidant tested. Viscosity index ranged from 130 to 202 for all estolides with the shorter chain length capped estolides gave the lower viscosity index values. Viscosity at 100 °C ranged from 13.9 to 26.6 cSt and the 40 °C viscosity ranged from 74.7 to 260.4 cSt where the longer chain length capped estolides gave the highest viscosities.  相似文献   

8.
Effect of pressing time on physical and mechanical properties of phenolic-impregnated bamboo strips was evaluated. Bamboo strips (Gigantochloa scortechinii) were impregnated with low molecular weight phenol formaldehyde (LMwPF) resin. Samples were submerged in LMwPF resin using a vacuum chamber of 750 mmHg for 1 h before it was released within 1.5 h. Treated strips were dried in an oven with a temperature of 60 °C within 6–9 h. It was hot pressed at 14 kg m?2 and a temperature of 140 °C for 5, 8, 11, 14 and 17 min. The physical and mechanical properties of the test indicated that the properties of phenolic-treated strips have significantly increased as compared to control samples. Dimensional stability (water absorption, thickness swelling and linear expansion) of the phenolic-treated properties were significantly lower than control after 5-min pressing time. The antishrink efficiency (ASE) of phenolic-treated strips increased when pressing time were extended from 5 to 17 min. The mean value of modulus of rupture (MOR) for the control samples (177 N mm?2) showed a significant difference with phenolic-treated strips after 17-min pressing time (224 N mm?2). However, there is no significant difference in compression parallel to grain. The MOE of phenolic-treated strips was 21,777 N mm?2 and for control was 18,249 N mm?2, whereas the compression parallel to grain values for phenolic-treated and control samples were 94 and at 77 N mm?2, respectively.  相似文献   

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A response surface method was employed to study the effect of α-amylase concentration, hydrolysis temperature and time on the production of high protein glutinous rice flour (HPGRF). The suspension of glutinous rice flour (15%) that contained 6.52% protein was gelatinized and subsequently hydrolyzed by thermostable α-amylase. The hydrolysis yielded 0.144–0.222 g/g HPGRF with 29.4%–45.4% protein content. Hydrolysis time exerted a significant effect, while enzyme concentration and hydrolysis temperature showed insignificant effect on the protein content and production yield of HPGRF. The result of response surface method showed that the optimum condition for the production of HPGRF that contained at least 36% protein was treating gelatinized 15% glutinous rice flour suspension with 0.90 Kilo Novo α-amylase Unit (KNU)/g α-amylase at 80 °C for 99 min. By carrying out the predicted hydrolysis condition, HPGRF with 35.9% protein and 61.8% carbohydrates was resulted. The process yielded 0.172 g/g HPGRF. HPGRF contained higher amount of essential amino acids compared to glutinous rice flour. HPGRF had higher solubility and lower swelling power, and also showed no pasting peak compared with glutinous rice flour.  相似文献   

10.
Saturated mono-estolide methyl esters and enriched saturated mono-estolide 2-EH esters were synthesized from oleic and different saturated fatty acids under three different synthetic routes. Estolide numbers (EN), the average number of fatty acid units added to a base fatty acid, varied with synthetic conditions. The attempts at obtaining saturated mono-estolide 2-EH esters, EN = 1, via distillation proved to be challenging, which lead to estolide samples with EN > 1 and the pour point values followed the same trend as the high EN estolides. The other synthetic routes provided saturated mono-estolide methyl esters with EN = 1. The resulting pour point values showed a linear relationship between the saturated capping chain length and pour point. As the saturated capping chain length increased the pour points also increased (higher temperatures): C-2 capped ?30 °C, C-10 capped ?12 °C, and C-18 capped 3 °C.The saturated mono-estolide methyl ester viscosities also showed an increase in viscosity at 40 and 100 °C as the saturated chain lengths increased. The viscosities for the C-4 saturated mono-estolide methyl ester was 9.5 cSt at 40 °C and 2.6 cSt at 100 °C, while medium chain length derivations (C-10 saturated mono-estolide methyl ester) were 19.7 cSt at 40 °C and 4.2 cSt at 100 °C, and at the longer chain length derivations (C-18 mono-estolide methyl esters) were 27.6 cSt at 40 °C and 10.7 cSt at 100 °C. In general, a new series of saturated oleic mono-estolide methyl esters were synthesized and physical properties were collected. The physical property data indicated that both chain length and EN affect low temperature properties.  相似文献   

11.
In the present work, thermogravimetric analysis of 17 organosolv lignin samples was carried out to determine their thermal stability and calculate the kinetic parameters of their pyrolysis. The thermal stability has been estimated by the measurement of the degradation temperature (Td), calculated according to the maximum reaction rate. In addition, degradation temperature at 10% of conversion (T10%) has been obtained in order to compare the initial stability of the samples with Td for all samples. The values of Td are comprised between 262 and 389 °C and the average value is 340 °C. The range for T10% is 251–320 °C and the average value is 270 °C. The ashes content of the samples has been analyzed and all the residues presented values lower than 4 wt%. Kinetic parameters of lignin pyrolysis were calculated by Borchardt–Daniels’ method assuming nth order reaction. The activation energy values obtained are comprised between 17.9 and 42.5 kJ/mol and the average value is 28.1 kJ/mol. These results are in agreement with the bibliography.  相似文献   

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Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for commercial oilseed production. Understanding the minimum temperatures for germination and seedling growth is important for determining potential areas for lesquerella production. The objectives of this study were to determine the cardinal temperatures for germination and seedling growth, and to screen ecotypes for germination and growth characteristics. A temperature gradient table arrangement was used to observe seed germination over a range of temperatures, and time to germination and shoot appearance. Times to 5 mm root length and 5 mm shoot length were also measured to assess cardinal temperatures for seedling survival and growth. Two different species were examined, L. fendleri and a species we refer to as ‘L. pallida aff.’ because it differed from typical L. pallida plants in chromosome number and in oil quality. We concluded that both germination and growth of L. pallida aff. occurred fastest at 22 °C, whereas L. fendleri germinated earlier at 18 °C, but grew faster at 22 °C. L. pallida aff. also had lower germination than L. fendleri over the range studied. Non-dormant seeds of improved lines of L. fendleri had better performance at temperatures above 22 °C than did unimproved accessions. Lines of L. fendleri selected for high oil content and salt tolerance had similar temperature requirements for germination except for improved line WCL-LO3, the current line being used in production. This line had optimal temperatures 6 °C higher for germination and growth than the other improved lines. Accessions of L. fendleri collected from elevations above 2000 m performed better at warmer temperatures, whereas those collected from elevations below 2000 m tended to perform better at cooler temperatures. Dormant seeds of L. fendleri germinated more quickly at low temperatures and had lower base (<3 °C) and optimal (22 °C) temperatures than non-dormant seeds (>7 °C and 28 °C, respectively). We speculate that this partial dormancy trait allows populations of L. fendleri to exploit a wider range of temperature conditions in the wild in order to thrive in extreme environments.  相似文献   

13.
In this work, the forward extraction of defatted wheat germ protein (DWGP) by reverse micelles was studied. The reverse micellar systems were formed by sulphosuccinic acid bis (2-ethylhexyl) ester sodium salt (AOT), isooctane and KCl solution. The effects of AOT concentration, pH, KCl concentration, extraction time, the amounts of defatted wheat germ flour (DWGF), W0 (the molar ratio of water to surfactant, i.e. W0 = [H2O]/[AOT]) and temperature on the forward extraction efficiency of DWGP were tested. On the basis of single-factor experiments, the optimum extraction was achieved by response surface methodology (RSM). The experimental results lead to the conclusion that the highest forward extraction efficiency of DWGP was reached at the AOT concentration 0.06 g/mL, pH 8, KCl concentration 0.1 mol/L, time 30 min, the amounts of DWGF 0.500 g, W0 25 and temperature 36 °C. Under these conditions, the forward extraction efficiency of DWGP achieved 37%.  相似文献   

14.
The color (L*, a*, b* parameters), the total phenols content and the global chemical composition (moisture, protein, fat, carbohydrates and ash) of four fresh varieties of olive leaves (Chemlali, Chemchali, Zarrazi and Chetoui) were determined. Fresh olive leaves are characterized by a green color (greenness parameter, a*, varying from ?5.01 ± 0.26 to ?9.14 ± 1.21), an intermediate moisture content (0.85 to 1.00 g/g dry matter, i.e. 46 to 50 g/100 g fresh matter) and a variable amount of total phenols according to the olive leaf variety (from ≈2.32 to ≈1.40 g caffeic acid/100 g dry matter).Fresh leaves were submitted to blanching and/or infrared drying at 40, 50, 60 and 70 °C in order to be stabilized by reducing their moisture contents. The impact of IR drying temperature on some quality attributes (color, total phenols and moisture rate removal) was evaluated. Nevertheless, the effect of prior blanching treatment on the quality attributes of dried leaves is less significant and it depends on the olive leaf variety. The infrared drying induces a considerable moisture removal from the fresh leaves (more than 85%) and short drying durations (varying from ≈162 at 40 °C to 15 min at 70 °C). IR drying temperature showed a significant effect of on total phenols content and the color of the leaves whatever the leaf variety. In fact, total phenols content of dried olive leaves increased if compared to fresh ones. For example, total phenols of Chemlali leaves increased from 1.38 ± 0.02 (fresh leaves) to 2.13 ± 0.29 (dried at 40 °C) and to 5.14 ± 0.60 g caffeic acid/100 g dry matter (dried at 70 °C). IR drying allows preserving the greenness color of fresh leaves and enhancing their luminosity. It could be suggested for preserving olives leaves before their use in food or cosmetic applications.  相似文献   

15.
Cuphea (Cuphea viscosissima Jacq. x C. lanceolata W.T. Aiton; PSR23) is a new oilseed crop rich in medium-chain fatty acids similar to tropical palms. Agronomic studies suggest that temperature is a key determinant of cuphea seed yields. However, little is known about the growth and photosynthesis response of cuphea to temperature. The following study is the first of its kind to evaluate cuphea's growth and photosynthesis response to temperature. Cuphea was grown under day/night temperature regimes of 18/12, 24/18, and 30/24 °C and regression analysis was used to assess its responses of growth and photosynthesis and determine their optimum temperature range. Vegetative growth and leaf photosynthesis adapted well over the temperature range studied. However, reproductive growth was more sensitive showing a decline with increasing temperature. Reproductive growth rate was greatest under the lowest (18/12 °C) temperature treatment and declined by 43% at the highest growth temperatures. In contrast, vegetative growth, which was greatest under the 24/18 °C treatment, declined by just 25 and 10% at the lowest and highest temperatures, respectively. Photosynthesis acclimated to temperature by up-regulation of in vivo Rubisco activity with declining growth temperature. Maximum Rubisco activity (Vcmax) in leaves under the 18/12 °C treatment was 76% greater than that of leaves grown at 30/24 °C. Photosynthetic acclimation permitted cuphea to vegetatively grow well over a wide temperature range, but does not explain the sensitivity of reproductive growth to temperature, which will require further research to elucidate.  相似文献   

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An experimental design was performed to study the influence of process variables (135–175 °C for temperature, 60–120 min for pulping time and 15–25% for active alkali) on the properties of pulps (yield, Kappa index, viscosity, 1% NaOH solubles, alcohol–benzene extractives holocellulose, lignin and α-cellulose contents and brightness) and paper sheets (stretch index, burst index, and tear index) obtained from olive trimming residues. Obtaining pulps with acceptably high physical and chemical properties entails operating at a temperature of 175 °C for 90 min and 25% of active alkali. The paper sheets obtained from olive trimming residues pulps that were produced in different degrees of refining are characterised for their stretch index, burst index, and tear index. An increase in the different parameters for the paper sheet upon increasing the degree of refining is found. All pulps reached between 33 and 39 kN m/kg in the stretch index, between 1.5 and 2 kN/g for the burst index and 0.7–2.5 N m2/g for the tear index and not in excess of the refining degree (<45 °SR).  相似文献   

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The impact of the oxidants potassium bromate and potassium iodate and the reducing agent dithiothreitol (DTT) on the rheological behaviour of 20% (w/v) gluten-in-water suspensions during thermal treatment was monitored with the rapid visco analyser (RVA). The suspensions were subjected to a linear temperature increase from 40 to 95 °C in 14 min, a holding step of 40 min at 95 °C, a cooling step (7 min) with a linear temperature decrease to 50 °C, and a final holding step at 50 °C (13 min). Potassium iodate (1.18 and 1.77 μmol/g protein) and potassium bromate (1.52 and 15.2 μmol/g protein) decreased RVA viscosities in the holding step and increased sodium dodecyl sulphate (SDS) protein extractabilities suggesting a greater heat resistance and decreased gliadin–glutenin cross-linking. In contrast, in the presence of DTT (1.65 and 3.30 μmol/g protein) RVA viscosity increased at lower temperatures and lowered SDS extractabilities. It is postulated that low concentrations of reducing agent facilitate gliadin–glutenin cross-linking during heating while oxidants hinder gluten polymerization due to decreased levels of free sulphydryl groups and less flexibility of the glutenin chains.  相似文献   

18.
A large number of spelt wheat genotypes (ranging from 373 to 772) were evaluated for grain concentrations of protein and mineral nutrients under 6 different environments. There was a substantial genotypic variation for the concentration of mineral nutrients in grain and also for the total amount of nutrients per grain (e.g., content). Zinc (Zn) showed the largest genotypic variation both in concentration (ranging from 19 to 145 mg kg−1) and content (ranging from 0.4 to 4.1 μg per grain). The environment effect was the most important source of variation for grain protein concentration (GPC) and for many mineral nutrients, explaining between 37 and 69% of the total sums of squares. Genotype by environment (G × E) interaction accounted for between 17 and 58% of the total variation across the minerals. GPC and sulfur correlated very significantly with iron (Fe) and Zn. Various spelt genotypes have been identified containing very high grain concentrations of Zn (up to 70 mg kg−1), Fe (up to 60 mg kg−1) and protein (up to 30%) and showing high stability across various environments. The results indicated that spelt is a highly promising source of genetic diversity for grain protein and mineral nutrients, particularly for Zn and Fe.  相似文献   

19.
Biodegradable, vegetable oil-based lubricants must have better low temperature properties as well as comparable cost to petroleum oils before they can become widely acceptable in the marketplace. The low temperature property usually measured is the pour point (pp), the minimum temperature at which the material will still pour. Viscosity and viscosity index also provide information about a fluid's properties where a high viscosity index denotes that a fluid has little viscosity change over a wide temperature range. Lesquerella oil is a good candidate for its development into a biodegradable lubricant as it is being developed as an alternative crop for the southwestern U.S. The hydroxy site on the fatty acid (FA) makes it a suitable site for esterification to yield estolides. Castor and lesquerella FA esters were combined with different types of saturated, unsaturated, and branched FAs to produce estolides. Castor and lesquerella estolide esters had the best cold temperature properties when capped with oleic (pp = −54 °C for castor and pp = −48 °C for lesquerella) or capped with a branched material, 2-ethylhexanoic acid (pp = −51 °C for castor and pp = −54 °C for lesquerella). As the saturation was increased in the estolide, pour and cloud points also increased. The increased saturation such as in stearic capped estolides allowed for sufficient alkyl stacking of these long saturated chains producing higher pour points. Oxidative stability of the estolides was compared between the oleic-castor estolide 2-ethylhexyl ester and the coco-castor estolide 2-ethylhexyl ester by the rotating bomb oxidation test (RBOT). The RBOT times for both estolides were low with a similar time of about 15 min. However, when the antioxidant package (3.5 wt.%) was added, the RBOT times increased to 403 min for the coco-castor estolide 2-ethylhexyl ester while still retaining its outstanding cold temperature properties, (pp = −36 °C and cp = −30 °C). The viscosity index ranged from 164 to 200 for these new hydroxy FA derived estolide 2-ethylhexyl esters. These oleic-castor and lesquerella estolide esters have displayed far superior low temperature properties (pp = −54 °C) than any other estolides reported to date. Due to the lack of solvent and catalysts, the cost of these estolides should be reasonable and more suitable as a base stock for biodegradable lubricants and functional fluids than current commercial materials.  相似文献   

20.
The demand for diesel fuel far exceeds the current and future biodiesel production capabilities of the vegetable oil and animal fat industries. New oilseed crops that do not compete with traditional food crop are needed to meet existing energy demands. Hybrid hazelnut oil is just such an attractive raw material for production of biodiesel. Hazelnut oil was extracted from hybrid hazelnuts and the crude oil was refined. Hazelnut oil-based biodiesel was prepared via the transesterification of the refined hazelnut oil with excess methanol using an alkaline catalyst. The effects of reaction temperature, time and catalyst concentration on the yield of diesel were examined, and selected physical and chemical properties of the biodiesel were evaluated. The biodiesel yield increased with increasing temperature from 25 to 65 °C and with increasing catalyst concentration from 0.1 to 0.7 wt%. The increase in yield with reaction time was nonlinear and characterized by an initial faster rate, followed by a slow rate. Hazelnut oil-based biodiesel had an average viscosity of 8.82 cP at 25 °C, which was slightly higher than that of the commercial soy-based diesel (7.92 cP at 25 °C). An approximate 12 °C higher onset oxidative temperature and a 10 °C lower cloud point of hazelnut oil biodiesel than those of its commercial soy counterpart indicated a better oxidative stability and flowability at low temperature. The average heat of combustion of hazelnut oil biodiesel was 40.23 kJ/g, and accounted for approximately 88% of energy content of diesel fuel. The fatty acid composition of hazelnut oil-based biodiesel was the same as the nature oil.  相似文献   

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