Biochemical and functional properties of Atlantic salmon (Salmo salar) muscle proteins hydrolyzed with various alkaline proteases

Protein hydrolysates (5, 10, and 15% degrees of hydrolysis) were made from minced salmon muscle treated with one of four alkaline proteases (Alcalase 2.4L, Flavourzyme 1000L, Corolase PN-L, and Corolase 7089) or endogenous digestive proteases. Reaction conditions were controlled at pH 7.5, 40 degrees C, and 7.5% protein content, and enzymes were added on the basis of standardized activity units (Azocoll units). Proteases were heat inactivated, insoluble and unhydrolyzed material was centrifuged out, and soluble protein fractions were recovered and lyophilized. Substrate specificities for the proteases was clearly different. Protein content for the hydrolysates ranged from 71.7 to 88.4%, and lipid content was very low. Nitrogen recovery ranged from 40.6 to 79.9%. The nitrogen solubility index was comparable to that of egg albumin and ranged from 92.4 to 99.7%. Solubility was high over a wide range of pH. The water-holding capacity of fish protein hydrolysates added at 1.5% in a model food system of frozen minced salmon patties was tested. Drip loss was on average lower for the fish protein hydrolysates than for egg albumin and soy protein concentrate, especially for Alcalase hydrolysates. Emulsification capacity for fish protein hydrolysates ranged quite a bit (75-299 mL of oil emulsified per 200 mg of protein), and some were better than soy protein concentrate (180 mL of oil emulsified per 200 mg of protein), but egg albumin had the highest emulsifying capacity (417 mL of oil emulsified per 200 mg of protein). Emulsification stability for fish protein hydrolysates (50-70%) was similar to or lower than those of egg albumin (73%) or soy protein concentrate (68%). Fat absorption was greater for 5 and 10% degrees of hydrolysis fish protein hydrolysates (3.22-5.90 mL of oil/g of protein) than for 15% hydrolysates, and all had greater fat absorption than egg albumin (2. 36 mL of oil/g of protein) or soy protein concentrate (2.90 mL of oil/g of protein).     

Oxygen permeability and mechanical properties of films from hydrolyzed whey protein

The effects of whey protein hydrolysis on film oxygen permeability (OP) and mechanical properties at several glycerol-plasticizer levels were studied. Both 5.5% and 10% degree of hydrolysis (DH) whey protein isolate (WPI) had significant effect (p 0.05) occurred for film OP between unhydrolyzed WPI, 5.5% DH WPI, and 10% DH WPI films at the same glycerol content. Hydrolyzed WPI films of mechanical properties similar to those of WPI films had better oxygen barrier. Therefore, use of hydrolyzed WPI allowed achievement of desired film flexibility with less glycerol and with smaller increase in OP.     

Structural and functional properties of amylose complexes with genistein

Complexes of amylose or high-amylose corn starch (HACS) with genistein were prepared by the acidification of an alkali solution to yield a V 6IotaIotaIota structure. The amylose-genistein complexes exhibited significantly higher genistein content (11 mg/100 mg of complex) than HACS-genistein complexes (9 mg/100 mg of complex). The effect of genistein on the amylose complexes was examined in different genistein-amylose ratios, and a model for genistein organization in the amylose complexes was suggested. The complexes were stable at different pH values, with <10% of the complexed genistein released, and were stable at 30 and 50 degrees C. Lower stability was observed at 80 degrees C as shown by the extensive release of genistein. All complexes showed high retention of genistein in simulated stomach conditions and released genistein upon digestion in pancreatin solution. It is therefore suggested that the complexes can be used as carriers for the slow release of genistein.     

Comparative evaluation of the emulsifying properties of phosphatidylcholine after enzymatic acyl modification

The ability of enzymatically synthesized structured phosphatidylcholine (PC) containing caprylic acid to form and stabilize oil-in-water emulsions prepared with different triglycerides [medium chain triglycerides (MCT), soybean oil, and enzymatically synthesized structured lipids] was examined and compared with natural soybean PC and deoiled lecithin. Emulsions were prepared with varying oil and emulsifier concentrations. The particle size distribution, creaming stability, and viscosity were measured for the evaluation of the emulsifying properties. With an increase in the oil concentration, there was an increase in particle size, viscosity, and creaming layer. With an increase in the phospholipid (PL) concentration, there was usually a decrease in particle size and an increase in viscosity, where the emulsion stability was increased. General emulsions prepared with structured lipids resulted in smaller particle sizes as compared to MCT and soybean oil. Deoiled lecithin was able to increase the viscosity more significantly and give smaller particle sizes as compared to the other emulsifiers, thus producing more stable emulsions. However, in certain cases, structured PC was superior to deoiled lecithin and soybean PC. This observation was made for emulsions prepared with soybean oil or structured lipid at an oil/water ratio of 10:90. At an oil/water ratio of 30:70, the deoiled lecithin performed better as compared to the other PLs with all oil types. However, structured PC produced more stable emulsions as compared to natural soybean PC in MCT and soybean oil.     

Stability and kinetic properties of humus-urease complexes

We have determined the kinetics and stabilities of various humus-urease preparations, extracted and purified from soil (Ceccanti, Nannipieri, Cervelli and Sequi, 1977). K_m, values of five different fractions in phosphate buffer ranged from 8 to 40 mM and were similar to those of urease extracted from various other sources. However, the optimal pH for urease activity of the soil fractions ranged from 7.5 to 8.8, in contrast to a pH optimum of about 7.0 for urease from sources other than soil. The shift in the optimal pH towards the alkaline region may be due to the influence of the negative charge of the humus matrix localized around the enzyme.Urease organo-complexes of mol. wt. < 10⁵ were slightly more resistant to thermal denaturation and to proteolysis than free urease. However, complexes of mol. wt. > 10⁵ were even more resistant, due probably to the occurrence of molecular arrangements similar to that proposed by Burns, El-Sayed and McLaren (1972a) and Burns, Pukite and McLaren (1972b). Thus although each of the five urease-active organic matter fractions exhibited different characteristics, they could be grouped into two distinct classes, according to mol. wt. and resistance to thermal denaturation and proteolysis.     

Thermal properties of typical chernozems in Kursk Oblast

Thermal diffusivity and heat capacity of virgin and plowed heavy loamy typical chernozems of Kursk oblast were studied. Thermal diffusivity was determined in the course of step-by-step drying of the initially capillary-saturated samples to the air-dry state. Specific heat capacity was determined for absolutely dry samples. Volumetric heat capacity was calculated according to the de Vries equation. Thermal diffusivity varied within the ranges of (1.15–3.46) × 10^–7 m²/s in the Ap horizon, (1.14–3.35) × 10^–7 m²/s in the А1 horizon, (1.49–3.70) × 10^–7 m²/s in the АВ horizon, (1.49–3.91) × 10^–7 m²/s in the В1 horizon, and (1.60–3.80) × 10^–7 m²/s in the Вса horizon. The thermal diffusivity vs. water content dependencies had distinct maximums and were flattened in the range of low water contents. The maximums were most pronounced for the mineral B1 and Bca horizons; for the A1 and Ap horizons, the curves were rather S-shaped. Volumetric heat capacity of the air-dry soils varied from 0.96 J/(cm³ K) in the A1 horizon to 1.31 J/(cm³ K) in the Bca horizon; in the state of capillary saturation, it varied from 2.79 J/(cm³ K) in the А1 horizon to 3.28 J/(cm³ K) in the Вса horizon. Thermal properties of topsoil horizons were higher in the plowed chernozem compared with the virgin chernozem, which is explained by an increase in the bulk density and a decrease in the organic matter content in the plowed soil.     

Physical and sensory properties of dairy products from cows with various milk fatty acid compositions

Dairy products from milk of cows fed diets rich in polyunsaturated fatty acids have a more health-promoting fatty acid composition and are softer but often have oxidized flavors. Dairy products made from cow's milk that has more- or less-unsaturated fatty acid compositions were tested for differences in texture and flavor from those made from bulk-tank milk. The milk was manufactured into butter, vanilla ice cream, yogurt, Provolone cheese, and Cheddar cheese. The products were analyzed for fatty acid composition, physical properties, and flavor. Milk of cows with a more monounsaturated fatty acid composition yielded products with a more monounsaturated fatty acid composition that were softer and had a satisfactory flavor. Thus, selection of cows for milk fatty acid composition can be used to produce dairy products that are probably more healthful and have a softer texture.     

Determination of antioxidant properties of aroma extracts from various beans

Aroma extracts from fresh soybeans, mung beans, kidney beans, and azuki beans were prepared using simultaneous steam distillation and solvent extraction (SDE) under mild conditions (55 degrees C and 95 mmHg). Extracts were examined for antioxidative activities in two different assays. The aroma extracts isolated from all beans inhibited the oxidation of hexanal for nearly one month at a level of 250 microL/mL. Mung bean and soybean extracts inhibited malonaldehyde (MA) formation from cod-liver oil by 86% and 88%, respectively, at the 250 microL/mL level. Azuki and kidney bean extracts inhibited MA formation from cod-liver oil by 76% and 53%, respectively, at the 250 microL/mL level. The antioxidative activities of mung bean and soybean extracts were comparable with that of the natural antioxidant, alpha-tocopherol (vitamin E).     

Thermal and physicochemical properties of rice grain, flour and starch

Three types of rices, namely, Thailand rice (Indica), Nipponbare (Japonica), and Himenomochi (Japonica waxy), in grain, flour, and starch forms have been studied for their thermal and physicochemical properties. In grain form, Indica was slender and Japonica rices were bold and thick. Indica had the highest protein and amylose equivalent. Protein contents in isolated starches varied from 0.2 to 0.9%. Cooked Indica grain was hardest and waxy rice was softest; stickiness was highest in Japonica rice. Glass transition temperature (T(g)) was highest in Indica rice flour (approximately 222 degrees C) and almost the same in Japonica rice flours. Melting point was highest for Japonica (approximately 264 degrees C) and almost the same for Japonica waxy and Indica rice flours. T(g) values of starches were almost the same in Indica and Japonica waxy (approximately 237 degrees C); defatting caused reduction in this property in all of the starches. Highest melting point was shown by Indica starch (approximately 276 degrees C) and was almost the same for the other two starches. Protein and fats play a critical role in glass transition and melting points of rice flours and their respective starches. Viscosities of the cooked pastes of flour and starch during cooking in an RVA instrument and their gel and other properties have been discussed.     

马铃薯糊化过程中介电特性和热特性的分析(简报)

该文采用介电特性测定仪(DES100)和示差扫描量热仪(DSC120)对马铃薯片(含水率80.7%,淀粉含量16.5%)介电特性和热特性进行了比较研究,以确定马铃薯淀粉糊化过程中各特征参数值之间的关系。由介电特性曲线得出:在1～100kHz频率范围内的,65～80℃温度范围内,介电常数e′随温度的升高出现跃变型变化,67℃时变化速率最大,之后逐渐下降;由热吸收曲线得出热焓值的变化与e′变化规律相同,其糊化的3个特征温度(糊化起始、峰值、结束)分别是65、67和80℃,从两曲线得到的各特征值基本一致,说明利用马铃薯的介电特性和热特性的综合分析可以更准确地掌握其糊化过程,为进一步利用和控制马铃薯的糊化作用提供参考。     

Manufacture of fermentable sugar solutions from sugar cane bagasse hydrolyzed with phosphoric acid at atmospheric pressure

Sugar cane bagasse, a renewable and cheap bioresource, was hydrolyzed at 100 degrees C using phosphoric acid at different concentrations (2, 4, or 6%) and reaction times (0-300 min) to obtain fermentable sugar solutions, which have a high concentration of sugars (carbon source for microorganism growth) and a low concentration of growth inhibitors (acetic acid and furfural). Xylose, glucose, arabinose, acetic acid, and furfural were determined following the hydrolysis. Kinetic parameters of mathematical models for predicting these compounds in the hydrolysates were obtained. Derived parameters such as efficiency of hydrolysis or purity of hydrolysates were considered to select as optimal conditions 6% phosphoric acid at 100 degrees C for 300 min. Using these conditions, 21.4 g of sugars L(-)(1) and <4 g of inhibitors L(-)(1) were obtained from the hydrolysis with a water/solid ratio of 8 g of water g(-)(1) of sugar cane bagasse on a dry basis.     

Influence of polysaccharides on the rate of coalescence in oil-in-water emulsions formed with highly hydrolyzed whey proteins

The objective of this study was to examine the effects of added xanthan gum, guar gum, or kappa-carrageenan on the formation and properties of emulsions (4 wt % corn oil) formed with an extensively hydrolyzed commercial whey protein (WPH) product under a range of conditions. The rate of coalescence was calculated on the basis of the changes in the droplet size of emulsions during storage of the emulsions at 20 degrees C. Compared with the emulsion made without the addition of polysaccharides, the rate of creaming and coalescence in emulsions containing xanthan gum, guar gum, or kappa-carrageenan was markedly enhanced with increasing concentration of polysaccharides during storage for up to 7 days. At a given concentration, the rate of coalescence was highest in the emulsions containing guar gum, whereas it was lowest in the emulsions containing kappa-carrageenan. All emulsions containing xanthan gum, guar gum, or kappa-carrageenan showed flocculation of oil droplets by a depletion mechanism. This flocculation was considered to enhance the coalescence of oil droplets. The different rates of coalescence could be explained on the basis of the strength of the depletion potential, which was dependent on the molecular weight and the radius of gyration of the polysaccharides.     

Field hydraulic properties of an Alfisol under various fallow systems in southwestern Nigeria

Abstract. The effects of various fallow management systems and cropping intensities on water infiltration were measured on an Alfisol at Ibadan in southwestern Nigeria. The objective was to determine the influence of the land use systems (a combination of crop–fallow sequences and intercropping types) on soil hydraulic properties obtained by disc permeameter and double-ring infiltration measurements. The experiment was established in 1989 as a split-plot design with four replications. The main plots were natural fallow, planted Pueraria phaseoloides and planted Leucaena leucocephala . The subplots were 1 year of maize/cassava intercrop followed by 3-year fallow (25% cropping intensity), or 2-year fallow (33% cropping intensity), or 1-year fallow (50% cropping intensity), or no fallow period (100% cropping intensity). Water infiltration rates and sorptivities were measured under saturated and unsaturated flow. Irrespective of land use, infiltration rates at the soil surface (121–324 cm h⁻¹) were greater than those measured at 30 cm depth (55–144 cm h⁻¹). This indicated that fewer large pores were present below 30 cm depth compared with 0–30 cm depth. Despite some temporal variation, sorptivities with the highest mean value of 93.5 cm h^−½ increased as the cropping intensity decreased, suggesting a more continuous macropore system under less intensive land use systems. This was most likely due to continuous biopores created by perennial vegetation under long fallow systems. Intercropped maize and cassava yields also increased as cropping intensity decreased. The weak relationship between crop yields and hydraulic conductivity/infiltration rates suggests that the rates were not limiting.     

Chemical properties and reactivity of manganese chelates and complexes in solution and soils

Commercial fertilizers containing synthetic manganese (Mn) chelates and complexes are currently used to alleviate Mn deficiency in crops. However, studies conducted on Mn sources in order to evaluate their behavior maintaining Mn soluble in nutrient solution and soil have not been done. In this work, representative commercial Mn fertilizers based on chelates and complexes were characterized and their chemical stability in solution and interaction with soils has been evaluated. Fertilizers studied were two ethylene diamine tetraacetic acid (EDTA) Mn chelates, one N‐(1,2‐dicarboxyethyl)‐D,L‐aspartic acid (IDHA) Mn chelate, two lignosulfonates, one carboxylate, one fulvate, one gluconate, and one heptagluconate‐based Mn complex. Characterization consisted of the determination of the soluble and chelated or complexed Mn, and the ligand identification by nuclear‐magnetic resonance (NMR). Stability study included batch experiments in Ca solution at different pH and three batch experiments with soil comparing with MnSO₄. Results indicate that most of the Mn fertilizers comply with the declared “soluble and chelated or complexed” metal content. At a usual pH range of calcareous soils (7.5–8.5), both chelates and complexes maintain more Mn in solution than MnSO₄ in the presence of Ca. Several factors affect the Mn remaining in solution after the interaction with the soil, especially, the soil‐to‐solution ratio. All chelates and complexes are better alternatives to the use of MnSO₄ in agronomical practices such as fertigation and soil application. Mn‐IDHA as chelate and Mn‐HGl or Mn‐Carb as complexes can be efficient, economical, and environmental friendly fertilizers for foliar application and hydroponic cultures. In soil application, Mn‐EDTA or Mn‐LS would be the best options. In this case, lignosulfonic acid represents a sustainable and low‐cost solution.     

水溶性有机碳在各种粘土底土中的吸附：土壤性质的影响

Clay-rich subsoils are added to sandy soils to improve crop yield and increase organic carbon (C) sequestration; however, little is known about the influence of clay subsoil properties on organic C sorption and desorption. Batch sorption experiments were conducted with nine clay subsoils with a range of properties. The clay subsoils were shaken for 16 h at 4 ^oC with water-extractable organic C (WEOC, 1 224 g C L^-1) from mature wheat residue at a soil to extract ratio of 1:10. After removal of the supernatant, the residual pellet was shaken with deionised water to determine organic C desorption. The WEOC sorption was positively correlated with smectite and illite contents, cation exchange capacity (CEC) and total organic C, but negatively correlated with kaolinite content. Desorption of WEOC expressed as a percentage of WEOC sorbed was negatively correlated with smectite and illite contents, CEC, total and exchangeable calcium (Ca) concentrations and clay content, but positively correlated with kaolinite content. The relative importance of these properties varied among soil types. The soils with a high WEOC sorption capacity had medium CEC and their dominant clay minerals were smectite and illite. In contrast, kaolinite was the dominant clay mineral in the soils with a low WEOC sorption capacity and low-to-medium CEC. However, most soils had properties which could increase WEOC sorption as well as those that could decrease WEOC sorption. The relative importance of properties increasing or decreasing WEOC sorption varied with soils. The soils with high desorption had a low total Ca concentration, low-to-medium CEC and low clay content, whereas the soils with low desorption were characterised by medium-to-high CEC and smectite and illite were the dominant clay minerals. We conclude that WEOC sorption and desorption depend not on a single property but rather a combination of several properties of the subsoils in this study.     

Partially carboxymethylated feather keratins. 2. Thermal and mechanical properties of films

Free cysteine thiol groups of keratin extracted from chicken feathers were partially carboxymethylated with iodoacetic acid (25-76% cysteine modification). Stable dispersions were used for the preparation of films by solution casting. Glycerol was used as a plasticizer (0.05-0.47 g/g of keratin), and films were stored at a constant relative humidity (20, 30, 50, 70, or 90%). The degree of crystallinity in the films was higher when more cysteine residues were carboxymethylated. The films displayed an optimum in mechanical properties at approximately 50% cysteine carboxymethylation. The tensile strength at this optimum was 25 MPa, the E modulus, 350 MPa, and the elongation at break, 50%. Probably, this optimum was the result of both a decreasing amount of disulfide bonds and an increasing degree of crystallinity for higher degrees of cysteine modification. The influences of a higher amount of glycerol and of different storage conditions on the mechanical properties of films from keratin with a defined degree of cysteine modification were also investigated.     

Fluorescence properties of humic acid interaction products with s-triazine and bipyridilium herbicides and their Cu complexes: a multivariate approach

Purpose

Excitation–emission matrices spectroscopy (EEMS) of soil humic acids (HAs) contains large amount of information on their properties, as well as on the dynamics related to their intra- and inter-molecular interactions. The objective of this research was (i) to show that EEMS represents a useful tool to investigate the molecular and mechanistic aspects of HA adsorbing capacity towards atrazine (A) and paraquat (P) with or without Cu²⁺ ions and (ii) to evaluate if additional information on these mechanisms can be obtained by combining EEMS with principal component analysis (PCA).

Materials and methods

HAs have been isolated from soil samples collected in a citrus field at three locations, within the plant rows (HAa); between the rows (HAb) and in a adjacent, control soil (HAc). Interaction products were obtained between each HA and A and P, with or without Cu ions. Elemental analysis and Fourier-transorm Infrared Spectroscopy were applied to support fluorescence data. Fluorescence spectra were recorded on aqueous solutions, and fluorescence intensity (FI) values were normalized using a quinine sulphate standard. PCA analysis was performed using the software STATGRAPHICS Centurion XV.I.

Results and discussion

The EEM spectra of the three unreacted HAs are characterized by the presence of two fluorophores α and β, in the region of longer wavelengths pairs (EEWP). The EEM spectra of the HA-A interaction products are featured by the same two fluorophores, with FI values decreased of about 50%, whereas those of the HA-P interaction products show a unique peak, γ, at intermediate EEWP. Finally, the EEM spectra of HA-A-Cu²⁺ show, with respect to HA-A samples, a blue shift of the α peak with an additional decrease of FI values (about 60%) and the disappearance of the peaks β, whereas those of HA-P-Cu²⁺ feature, in comparison with those of HA-P, a small red-shift of the peak γ. PCA data suggest that Cu ions do not affect the interaction mechanism between HA and P, whereas it appears to exercise a strong influence on interaction between HA and A.

Conclusions

The results obtained indicate that EEMS allows direct measurements of the adsorbing capacity of HA towards atrazine and paraquat. Additional information obtained by PCA analysis show that Cu ions behave like a good antagonist in preventing the formation of ionic bonds between HA and atrazine, whereas Cu is not able to affect the prevalent mechanism of HA interaction with paraquat, which is a charge-transfer bond.

     

Enzyme-induced gelation of extensively hydrolyzed whey proteins by alcalase: comparison with the plastein reaction and characterization of interactions

Extensive hydrolysis of whey protein isolate by Alcalase 2.4L produces a gel. The objectives of this study were to compare enzyme-induced gelation with the plastein reaction by determining the types of interactions involved in gelation. The average chain length of the peptides did not increase during hydrolysis and reached a plateau after 30 min to be approximately 4 residues, suggesting that the gel was formed by small molecular weight peptides held together by non-covalent interactions. The enzyme-induced gel network was stable over a wide range of pH and ionic strength and, therefore, showed some similarities with the plastein reaction. Disulfide bonds were not involved in the gel network. The gelation seems to be caused by physical aggregation, mainly via hydrophobic interactions with hydrogen bonding and electrostatic interactions playing a minor role.     

Effects of seedbed properties on crop emergence: 3. Effects of firming of seedbeds with various sowing depths and water contents

Abstract

Extensive experiments were carried out in shallow plastic boxes placed directly on the ground in the field to study the effects of seedbed properties on the emergence of various crops in a cool temperate climate. In a group of experiments with barley (Hordeum vulgare L.), we studied the effects on crop emergence of firming (slight compaction) of the seedbed, simulating the recompacting effects of rolling after sowing or press wheels on the seed coulters. Most of the experiments were carried out without irrigation after sowing. The firming usually had a slightly positive effect on emergence when the water content in the surface layer at sowing was below the wilting point. When the water content in the surface layer was higher, firming often reduced emergence drastically, particularly with deep sowing and in coarse-textured soils. The main reason for negative effects was harmful hardening of the surface layer when the more firm seedbed gradually dried out. When irrigation kept the seedbed continuously moist, the negative effect of firming was almost eliminated. Very high initial water content in the basal layer tended to delay surface layer drying and hardening, and to reduce the negative effect of firming. Firming only slightly influenced the evaporative water losses from the soil. In contrast to the results presented here, previous field trials with cereals have usually resulted in more positive effects of rolling after sowing. This indicates that other effects than firming, such as modification of sowing depth and reshaping of the soil surface, are other important effects of rolling.     

石蜡/ZIF-8@ZIF-67定形相变材料的储热性能

针对固-液相变材料在相变过程中由于体积变化产生的芯材泄漏现象,该研究以ZIF-8@ZIF-67核壳结构为载体,以石蜡（paraffin）为相变芯材,采用溶剂蒸发法制备了质量分数为50%、60%、70%和75%的石蜡/ZIF-8@ZIF-67定形相变材料。通过扫描电镜、透射电镜、X射线衍射、傅里叶红外光谱、BET比表面积、热重分析、差式扫描量热和瞬态平板热源等测试手段对定形相变材料的形貌、结构、热稳定性、相变潜热、热导率进行表征;采用Fluent软件对填充相变材料的相变蓄热供暖系统进行了数值模拟分析。结果表明：ZIF-8@ZIF-67形貌为大小均匀的菱形十二面体,石蜡的最高负载量为70%,且石蜡与ZIF-8@ZIF-67 MOF载体之间没有发生化学变化。质量分数为70%的石蜡/ZIF-8@ZIF-67经50次热循环后,熔化焓为54.36 J/g,与循环前相比无明显下降（循环前熔化焓为59.59 J/g）,说明其具有良好的热循环稳定性。研究表明质量分数为70%的石蜡/ZIF-8@ZIF-67相变材料可以很好的保持整体系统的温度稳定性,具有良好的蓄-放热效果。