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.     

牦牛“曲拉”精制干酪素工艺研究

由传统牦牛“曲拉”制得的干酪素品质不佳的主要原因是脂肪氧化、杂质过高，该文用改良的工艺流程，通过L₉(3⁴)正交试验，研究酶制剂和离心条件对“曲拉”所制干酪素品质的影响。结果表明：酶制剂最佳应用条件为料液温度38℃，pH值4.2，胰蛋白酶浓度1.0 g/kg(处理时间5 min)，脂肪酶浓度0.01 g/kg，乳糖酶浓度0.03 g/kg；最佳离心工艺参数为，转速16000 r/min、时间10 min、温度50℃。高速离心法和酶处理过程，既能除去料液中脂肪、乳糖、尘埃等杂质，又使制品溶解黏度、色泽、气味等明显改善。红外光谱检测，制品质量优于传统产品。     

Oxygen and substrate availability interactively control the temperature sensitivity of CO2 and N2O emission from soil

Biology and Fertility of Soils - We investigated how oxygen availability, substrate amount, and quality affect the temperature dependency of enzymatic processes involved in the production of carbon...     

Development and characterization of biodegradable films made from wheat gluten protein fractions

Gliadins and glutenins were extracted from commercial wheat gluten on the basis of their extractability in ethanol and used to produce film-forming solutions. Films cast using these gliadin- and glutenin-rich solutions were characterized. Glycerol was used as a plasticizer, and its effect on the films was also studied. Films obtained from the glutenin fraction presented higher tensile strength values and lower elongation at break and water vapor permeability values than gliadin films. Gliadin films disintegrated when immersed in water. The GAB isotherm model was used to describe the equilibrium moisture sorption of the films. The glycerol concentration largely modified mechanical and water vapor barrier properties of both film types.     

Functional properties of bioplastics made from wheat gliadins modified with cinnamaldehyde

Cinnamaldehyde is a naturally occurring α,β-unsaturated aldehyde. Its potential as a natural cross-linker to improve the physical performance of cast wheat gliadin films was evaluated. The cross-linking reaction was found to be dependent on the pH of the reaction medium, with pH 2 as the optimum. The water resistance (weight loss after immersion), mechanical properties (Young's modulus, tensile strength and elongation at break), thermal properties (T(g) and decomposition behavior), optical properties and morphology of films were evaluated. Cross-linked films showed high transparency, maintained their integrity after immersion, and displayed significant improvements in tensile strength and Young's modulus without impairment of their elongation properties. These effects, which were proportional to the amount of cinnamaldehyde added, highlight the possible formation of intermolecular covalent bonds between "monomeric" gliadins, leading to a polymerized network. Thus, this treatment could provide a new alternative to the toxic cross-linkers commonly employed and so extend the use of gliadin films.     

稻壳粉/改性脲醛树脂模压成型材料的力学性能

为了研究成型材料对模压花盆力学性能的影响,该文以改性脲醛树脂为基体树脂,稻壳与稻壳粉为增强材料,经混炼、热压、成型工序,制备出一种环保花盆。探讨了脲醛树脂改性、改性脲醛树脂用量、稻壳与稻壳粉比例以及湿循环处理对花盆力学性能的影响,采用热重分析仪(thermo-gravimetric analysis,TGA)及扫描电子显微镜(scanning electronic microscope,SEM)分析了秸秆花盆湿循环处理前后的热稳定性及微观结构。结果显示:改性脲醛树脂和稻壳粉有利于改善秸秆花盆的力学性能,当增强填料与基体树脂的比例为1:0.5,稻壳占稻壳粉的质量分数为30%时,花盆的静曲强度(modulus of rupture,MOR)、弹性模量(modulus of elastic,MOE)及拉伸强度(tensile strength,TS)分别达75.48 MPa、16.06 GPa、17.44 MPa;湿循环处理试验中,以稻壳为增强材料为例,当基体树脂为改性脲醛树脂时,其MOR、MOE及TS分别降低21.97%、24.91%、15.09%;当基体树脂为大豆蛋白改性脲醛树脂时,其MOR、MOE和TS分别降低9.92%、15.37%、30.10%。热重分析发现湿循环处理后花盆热稳定性有所提高,微商热重出现最大失重率的温度向高温侧偏移29.5℃。扫描电子显微镜分析表明湿循环处理后样品表面粗糙度增加,增强体与树脂发生分离。该研究结果为进一步研究秸秆花盆制作工艺和使用年限的相关性提供理论依据。     

Development of a continuous process to make casein films

A semicontinuous pilot plant process was developed to make films from calcium caseinate plasticized with glycerol. Calcium caseinate/glycerol solutions were wetted and spread on polyethylene or Mylar belts and were readily removed after forming films. A Meier rod was used to spread the solution onto the belt. Feed rates were 3.3 and 5 g/cm. The resulting films using the polyethylene belt had a tensile strength of 5 MPa and 30% elongation with thickness of 0.14 mm. When the glycerol concentration was adjusted, the process produced films with properties similar to those previously reported for a batch process. It is anticipated that this process will apply to other proteins.     

Oxygen and CO2 Profiles and Methane Formation During the Maturation Phase of Composting

Several different composts were examined both at bench-scale and on-site. The samples were taken from full-scale windrow composting plants at different stages of maturation. Oxygen, carbon dioxide and methane profiles within the material matrix for each sample were monitored and values for specific oxygen uptake rate (SOUR), moisture content (MC), and volatile solids (VS) were also determined. Methane was detected inside some of the composting piles (with values higher than 10% by volume) and in one of the bench-scale systems (with values up to 0.9% by volume) but never within the upper 0.20 meters of material. The profiles indicated that the methane was probably oxidized within the mass and consequently methane release during the maturation stage of the composting process was probably not common.     

纳米氧化锌改性LDPE食品包装薄膜中锌粒子的迁移规律

为探究纳米氧化锌改性(low-density polyethylene,LDPE)薄膜中纳米锌粒子的迁移规律,依照欧盟法规(EU)No.10/2011,分别采用蒸馏水、30 g/L乙酸溶液、体积分数10%的乙醇溶液、体积分数95%的乙醇溶液作为中性、酸性、脂肪性和酒精性食品模拟物,研究在不同温度条件下(40、70℃)纳米锌粒子的迁移情况,同时探究微波和紫外处理对迁移结果的影响。研究发现,纳米锌粒子在4种食品模拟物中的迁移量从高到低依次为:酸性食品模拟物、中性食品模拟物、酒精性食品模拟物和脂肪性食品模拟物,并且随温度的升高,纳米锌粒子的迁移量增大。此外,微波处理能促进纳米锌粒子的迁移,而紫外处理则没有促进效果。纳米锌粒子的迁移量范围为0.52~14.17 mg/kg。根据欧盟规定所允许的最大迁移量5 mg/kg,迁移试验表明纳米氧化锌改性LDPE薄膜还需要进一步开展减少纳米粒子迁移的研究工作,以确保其在食品包装中的安全使用。     

Short-term CO2 emissions from planted soil subject to elevated CO2 and simulated precipitation

Carbon dioxide emissions from soils beneath canopies of two Mediterranean plants, Artemisia absinthium L. and Festuca pratensis Huds. cv. Demeter, were monitored over a 7-day period that included an artificial precipitation event of 4 cm. The experiments were conducted using 0.2 m³ soil microcosms inside greenhouses with CO₂ concentrations of either 360 or 500 μmol mol⁻¹. Carbon dioxide flux from the soil surface, as calculated using a diffusive transport model agreed well with CO₂ flux measurements made using a dynamic flow system. Soil CO₂ emissions did not differ significantly between the 360 and 500 μmol mol⁻¹ CO₂ treatments when soils were dry (volumetric soil moisture content ≤9%). A simulated precipitation event caused an immediate exhalation of CO₂ from soil, after which CO₂ emissions declined slightly and remained constant for approximately 36 h. CO₂ emissions from soil microcosms with F. pratensis plants growing in 500 μmol mol⁻¹ CO₂ then rose to levels that were significantly greater than CO₂ emissions from soils in the microcosms exposed to 360 μmol mol⁻¹ CO₂. For A. absinthium growing in 500 μmol mol⁻¹ CO₂, the rise in soil CO₂ emissions following the wetting event was not significantly greater than emissions from soils with A. absinthium growing under 360 μmol mol⁻¹ CO₂. A. absinthium above ground biomass increased by 46.1 ± 17.9% (mean ± S.E., n = 4, P ≤ 0.05). Above ground biomass did not significantly increase for F. pratensis (14.4 ± 6.5%, P ≥ 0.10). Root biomass, on the other hand, increased for both species; by 50.6 ± 17.9% (P ≤ 0.05) for A. absinthium and by 55.9 ± 12.7% (P ≤ 0.05) for F. pratensis. Our results demonstrate two events following precipitation onto dry soils, an immediate release of CO₂ followed by a gradual increase from enhanced biological activity The gradual increase was greater for the herbaceous ruderal perennial F. pratensis under elevated CO₂.     

Plasticizer effect on oxygen permeability of beta-lactoglobulin films

Plasticizer effect on oxygen permeability (OP) of beta-lactoglobulin (beta-Lg) films was studied. Propylene glycol (PG), glycerol (Gly), sorbitol (Sor), sucrose (Suc), and polyethylene glycol at MW 200 and 400 (PEG 200 and PEG 400, respectively) were studied due to their differences in composition, shape, and size. Suc-plasticized beta-Lg films gave the best oxygen barrier (OP < 0.05 cm3 x microm/m2 x day x kPa). Gly- and PG-plasticized films had similar OP values, and both had higher OP than Sor-plasticized films. PEG 200- and PEG 400-plasticized films were the poorest oxygen barriers. Empirical equations including plasticizer efficiencies for OP were employed to elucidate the relationships between OP of plasticized beta-Lg films and plasticizer type and content. Plasticizer efficiency ratios between mechanical and OP properties of beta-Lg films show the relative efficiency of plasticizers in modifying mechanical and OP properties. A large ratio is desirable.     

乙醇胺改性硅胶吸附剂对模拟沼气中CH_4/CO_2的分离性能

沼气的主要成分是CH4和CO2,有效地去除沼气中的CO2是确保沼气成为优质燃气的必要条件。吸附法是去除沼气中CO2的有效方法,研制性能优良的吸附剂是吸附法研究的核心问题。该文以FNG-II型硅胶为载体,乙醇胺(ethanolamine,MEA)为改性剂,制备了MEA改性硅胶吸附剂,表示为FS-MEA(FNG-II Silica-ethanolamine)。用X射线衍射、N2物理吸附脱附法、热重-差热、红外光谱等手段对吸附材料的结构、比表面积、孔结构、改性后结构变化等进行了分析。通过动态吸附分离试验,考察了FS-MEA对CH4/CO2的分离性能。结果表明:改性方法可将MEA附着在载体内孔表面,制得的FS-MEA可有效地分离CH4/CO2,但经过2次使用再生后,FS-MEA对CH4/CO2的分离性能有所下降,因此必须提高乙醇胺改性硅胶吸附剂的再生性能,才有可能使其应用于沼气提纯。     

Antioxidant activity and diffusion of catechin and epicatechin from antioxidant active films made of poly(L-lactic acid)

Active membranes and food packaging containing antioxidants like catechin and epicatechin, combined with the use of materials made of biopolymers obtained from renewable sources, could create a novel alternative to reduce oxidation in food, pharmaceutical, and cosmetic products. Poly(94% L-lactic acid) films containing 1.28% catechin and 1.50% epicatechin were extruded in a pilot plant-scale extrusion machine. The diffusion kinetics of catechin and epicatechin into 95% ethanol at 20, 30, 40, and 50 °C and 50% ethanol at 40 °C displayed Fickian release behavior and diffusion coefficients between 0.5 and 50 × 10(-11) cm(2)/s. According to the Arrhenius equation, the energy of activation for the diffusion of catechin and epicatechin in the films was 110.43 and 98.92 kJ/mol, respectively. The antioxidant activity of the films was measured in methanol extracts containing 46.42 μg/mL of catechin and 57.52 μg/mL of epicatechin as 32.90 and 36.68% of scavenging the 2,2-diphenyl-1-picrylhydrazyl radical, respectively.     

The water vapor permeability of polycrystalline fat barrier films

The water vapor permeability of fat barrier films has been associated with structural characteristics such as polymorphism, crystal size, and chemical composition, among others. However, no mechanistic models have been proposed to describe this relationship. In this study, we have determined the effects of processing conditions on the structure and physicochemical characteristics of four fats and their relationship to water vapor permeability. Results suggest that the solids' volume fraction and the domain size of the fat crystals seem to be the most important factors controlling water vapor migration. Moreover, materials with relatively large crystalline domains will yield malleable films with relatively low storage and loss moduli and strain/stress at the limit of linearity high tan delta values. The structural effects on the permeability of fat films are related to the nanoscale of the material.     

Plant-derived CO2 flux from cultivated peat soils

Abstract

Methods used to estimate the CO₂ emission from soil commonly measure the total CO₂ flux. To be able to quantify the net CO₂ emission from cultivated peat soils there is a need to distinguish between soil organic matter-derived CO₂ respiration and plant-derived respiration. In this investigation we used the root exclusion method to separate the plant-derived respiration from total CO₂ emission. The plant-derived contribution was estimated to be between 27 and 63% of total CO₂ emission depending on soil type and season. We also found a relationship between soil temperature, biomass growth and CO₂ efflux, which can be used to estimate plant-derived respiration. Due to the priming effect the root exclusion method is less reliable late in the season.     

CO2-emissions from agriculture: Sources and mitigation potentials

In 1991/92, the subgroup “Agriculture and Forestry” of the IPCC Working Group III developed an update of its earlier statements in the first IPCC-Report, concerning the release of greenhouse gases from agriculture. The present paper is an extract from this updated IPCC Supplement, concentrating on the CO₂ emissions from agriculture and its potentials for mitigation.     

Laboratory experiments on nematodes from natural CO2 springs reveal species-specific tolerance to extreme CO2 concentrations

This study focuses on the CO₂-tolerance of soil nematodes from natural CO₂ springs (mofette fields). In laboratory experiments, we compared survival, reproduction, activity and reactivation of a CO₂-sensitive species with a CO₂-tolerant species. Both species survived even 100% CO₂, but in an inactive state. The higher the CO₂ concentration the more individuals entered inactivity. We found significant differences between the two species: more adults of the CO₂-tolerant species maintained activity and reproduction at higher CO₂ concentrations. Moreover, reactivation after inactivity was faster. Together with a higher juvenile mortality of the CO₂-sensitive species, these interspecific differences are conclusive to explain the niche separation of the two species that was observed in the mofette field.     

High-pressure homogenization lowers water vapor permeability of soybean protein isolate-beeswax films

Soybean-protein isolate (SPI) has excellent film-forming capacity. However, the water vapor permeability of SPI film is high, which will cause the moisture lose of packaged products. The effect of high-pressure homogenization (HPH) on the water vapor permeability of SPI-beeswax films was evaluated. The HPH was effective at lowering the water vapor permeability of SPI-beeswax films to about 50% of the control. The HPH reduced the particle size of films and made their matrix more compact. The HPH improved the hydrophobicity of SPI-beeswax films. For the first time, we proved that the HPH improved the bound-beeswax content in SPI-beeswax films. The bound beeswax was effective at lowering the water vapor permeability of films rather than the free beeswax in the film matrix. In summary, the HPH lowered water vapor permeability of SPI-beeswax films by reducing their particle size and raising their hydrophobicity and bound-beeswax content.     

Mechanical properties and water-vapor permeability of soy-protein films affected by calcium salts and glucono-delta-lactone

Edible films were prepared from solutions of soy protein with calcium salts and glucono-delta-lactone (GDL). Calcium salts cross-linking interactions with soy-protein isolate (SPI) could result in the formation of films with rigid three-dimensional structure. GDL contributed to the formation of a homogeneous film structure due to increased protein--solvent attraction. Tensile strength (TS) of calcium sulfate treated SPI film (8.6 MPa) was higher than the TS of calcium chloride treated SPI films (6.4 MPa) and the control SPI film (5.5 MPa). Puncture strength (PS) of calcium sulfate treated SPI film (9.8 MPa) was higher than the PS of calcium chloride treated SPI films (8.5 MPa) and the control SPI film (5.9 MPa). SPI film formulated with GDL had larger elongation at break (39.4%) than that of SPI control film (18.2%). Calcium salts and GDL-treated SPI films had lower water-vapor permeability than the SPI control film.     

超临界CO2流体萃取槟榔中的槟榔碱

为了优化超临界CO2萃取槟榔碱的工艺参数,通过三元二次通用旋转组合设计实施试验,考察了萃取温度、萃取压力和萃取时间因素对槟榔碱萃取量的影响.试验结果表明:超临界萃取的温度对槟榔碱萃取量有极显著的影响,萃取时间和压力的影响较小.同时确定了槟榔碱萃取的最佳工艺参数为萃取温度72°C,压力57 MPa,时间26 min.在此条件下,槟榔碱的萃取量为6143.71/μg/g,达到理论最大萃取量的95.3%,所得萃取物中槟榔碱的百分含量晕为(25.85±0.41)%.