Depleting methyl bromide residues in soil by reaction with bases

Despite generally being considered the most effective soil fumigant, methyl bromide (MeBr) use is being phased out because its emissions from soil can lead to stratospheric ozone depletion. However, a large amount is still currently used due to Critical Use Exemptions. As strategies for reducing the postfumigation emissions of MeBr from soil, Ca(OH)(2), K(2)CO(3), and NH(3) were assessed as means of promoting MeBr degradation. Ammonia aqueous solution (NH(4)OH) was the most effective, because MeBr can be degraded by both hydrolysis and ammonolysis. At 20 °C, the half-lives (t(1/2)) of MeBr were 18.0, 2.5, and 1.3 h in 0.1, 1.0, and 2.0 M NH(4)OH, respectively. In 1.0 M NH(4)OH, increasing the solution temperature to 40 °C reduced the half-life of MeBr to 0.23 h. Ammonia amendment to moist soil also promoted MeBr transformation, and the MeBr degradation rate increased with increasing soil temperature. NH(4)OH (30%, 16 M) very effectively reacted with MeBr that was contained under plastic film. Under Hytibar (a virtually impermeable film, VIF), over 99.5% of the MeBr could be destroyed by 30% NH(4)OH in 8 h at 20 °C. On the basis of these results, good management practices (i.e., VIF plus NH(4)OH) could be developed for continued use of MeBr as a soil fumigant under Critical Use Exemptions, without significant emissions.     

Mitigating 1,3-dichloropropene, chloropicrin, and methyl iodide emissions from fumigated soil with reactive film

Implicated as a stratospheric ozone-depleting compound, methyl bromide (MeBr) is being phased out despite being considered to be the most effective soil fumigant. Its alternatives, i.e., 1,3-dichloropropene (1,3-D, which includes cis and trans isomers), chloropicrin (CP), and methyl iodide (MeI), have been widely used. High emissions of MeI from fumigated soil likely put farm workers and other bystanders at risk of adverse health effects. In this study, two types of constructed reactive film were tested for their ability to mitigate emissions of 1,3-D, CP, and MeI using laboratory permeability cells. Before activation, these films act as a physical barrier to trap fumigants leaving soil. After activation of the reactive layer containing ammonium thiosulfate solution, the films also act as a sink for the fumigants. Over 97% of trans-1,3-D and 99% of the cis-1,3-D, CP and MeI were depleted when they passed into the reactive film. Half-lives (t(1/2)) of cis-, trans-1,3-D, CP and MeI under activated reactive film were 1.2, 1.4, 1.6, and 2.0 h respectively at 40 °C.     

Thiosulfate and manure amendment with water application and tarp on 1,3-dichloropropene emission reductions

Reducing fumigant emissions is required for minimizing bystander risk and environmental impact. Effective and economic field management methods including commonly used surface sealing technique and soil amendments are needed for achieving emission reductions. This research determined the effectiveness of ammonium thiosulfate (ATS) and composted manure amendments to surface soil in combination with water application or high density polyethylene (HDPE) tarp on reducing emissions of 1,3-D from soil columns. Surface treatments included an untreated control, water seal (single water application at time of fumigant injection), ATS amendments at 1:1 and 2:1 molar ratio of ATS:fumigant, composted steer manure at 3.5 kg m(-2), and HDPE tarp over 1:1 ATS or the manure amendment. Cumulative 1,3-D emission loss over two weeks was greatest for the control (52% of applied). The HDPE tarp over ATS and manure treatments had the lowest 1,3-D emissions at 24 and 16%, respectively. Treatments with ATS or manure alone reduced 1,3-D emissions (29-39%) more effectively than water seal (43%) and further benefit was gained with the addition of HDPE tarp. Amendment of surface soil with organic materials shows greater potential in minimizing fumigant emissions than with chemicals with the need for a better understanding of the organic-fumigant reaction mechanism.     

不同包装材料对草莓贮藏品质和保鲜期的影响

在4℃贮藏条件下,采用不同的塑料包装材料(LDPE、HDPE和OPP膜)对草莓进行保鲜包装,测定不同贮藏时间下草莓的失重率、好果率、VC含量、果实硬度和可溶性固形物。结果表明:塑料包装膜能明显抑制草莓变质;具有较低透气率的HDPE薄膜保鲜效果最好,其次是OPP膜,再次是LDPE膜。      

可食包装膜与合成包装膜综合性质的对比研究

研究了几种可食包装膜和合成包装膜的综合性质。结果表明:明胶膜、海藻酸钠复合膜和甲基纤维素复合膜综合性质较好。明胶膜的直角撕裂强度和断裂伸长率高于低密度聚乙烯膜(LDPE膜)和高密度聚乙烯膜(HDPE膜),但其抗拉强度稍低于HDPE膜而高于LDPE膜;海藻酸钠复合膜和甲基纤维素复合膜的抗拉强度高于HDPE膜和LDPE膜,海藻酸钠复合膜的直角撕裂强度和断裂伸长率以及甲基纤维素复合膜的断裂伸长率低于LDPE膜和HDPE膜,但甲基纤维素复合膜的直角撕裂强度却高于LDPE膜和HDPE膜;这3种膜都具有热封性,其热封强度接近HDPE膜,并具较高的阻气、阻油和阻湿性能,可以满足一些食品的包装要求。     

Effect of surface tarp on emissions and distribution of drip-applied fumigants

Soil fumigants are used to control a wide variety of soil-borne pests in high-cash-value crops. Application of soil fumigants through drip irrigation systems is receiving increasing attention as a method to improve the uniformity of fumigant application. Little information is available on the emissions and soil distribution of fumigants following subsurface drip application, or the effect of plastic tarp on fumigant emissions in these systems. In these experiments, the fumigant compounds 1,3-dichloropropene (1,3-D), Vapam (a methyl isothiocyanate (MITC) precursor), and propargyl bromide (PrBr) were applied to soil beds via drip irrigation at 15 cm depth. Beds were tarped with either standard 1-mil high-density polyethylene (HDPE) or a virtually impermeable film (VIF), leaving the furrows bare. Cumulative emissions of 1,3-D, MITC, and PrBr in these tarped bedded systems was very low, amounting to <10% of the applied mass. These experiments were conducted in the winter months, with average air temperatures of 12-15 degrees C. Cumulative emissions of MITC and 1,3-D from a sandy loam field soil were decreased by > or =80% by tarping the bed with VIF rather than HDPE. A large fraction of the 1,3-D and PrBr flux was from the untarped furrows in VIF-tarped plots, indicating that inhibiting volatilization from the furrow will be important in further reducing emissions in these systems. Monitoring the fumigant distribution in soil indicated that tarping the bed with VIF resulted in a more effective containment of fumigant vapors compared to use of a HDPE tarp.     

Effect of environmental conditions on the permeability of high density polyethylene film to fumigant vapors

Soil fumigation in greenhouses or agricultural fields often includes tarping the soil surface with polyethylene (PE) films to contain the fumigant in the soil and reduce emissions to the atmosphere. Previous research has demonstrated that PE films are permeable to methyl bromide and other fumigant compounds. In these experiments, the effect of temperature, fumigant mixtures, condensed water, and field aging on the permeability of high-density polyethylene (HDPE) was determined. Mass transfer coefficients (h, a measure of permeability) of the fumigants methyl bromide, 1,3-dichloropropene, propargyl bromide, and chloropicrin across HDPE films were determined. In these studies, temperature and HDPE film type had the largest impact on the h of fumigant compounds across HDPE films. Other factors investigated, including fumigant mixtures, condensed water on the film, and field aging of UV-stabilized film, did not have a significant impact on h. The results of these experiments suggest that the permeability of an intact piece of an agricultural film will increase with increasing temperature but is relatively constant despite changes in other environmental conditions.     

Trout skin gelatin-based edible film development

Edible biopolymer films were developed from gelatin extracted from trout skin (TSG) using thermal protein denaturation conditions and plasticizer (glycerol) concentration as variables. The amino acid composition of the TSG, elastic modulus, viscous modulus, and the viscosity of film-forming solutions, and tensile properties, water vapor permeability, solubility in water, and color of TSG-based films were determined. A 6.8% (w/w, wet basis) trout skin-extracted gelatin solution containing 9, 17, or 23% (w/w, dry basis) glycerol was heated at 80, 90, or 100 °C for 30, 45, or 60 min to prepare a film-forming solution. TSG can be characterized as a gelatin containing high contents of methionine and aspartic acid. The gelation temperature of the film-forming solution was 7 °C and the solution was subjected to heating to form a stable matrix for a film. Increased heating time of the film-forming solution reduced the film solubility (P < 0.05). Heating at 90 °C for 30 min was suggested as the requirement for film formation. As the concentration of glycerol in the film increased, film strength and moisture barrier properties decreased, while film stretchability increased (P < 0.05). Trout skin by-products can be used as a natural protein source for fabricating biopolymer films stable at ambient conditions with certain physical and moisture barrier properties by controlling thermal treatment conditions and glycerol concentrations. Practical Application: The fishing industry produces a significant amount of waste, including fish skin, due to fish processing. Trout skin waste has potential value as a protein source that can be used to form biopolymer edible films for packaging low and intermediate water activity food products, and thus may have practical applications in the food industry, which could be one way to cut waste disposal in the trout processing industry.     

METHYL BROMIDE, TIME and TEMPERATURE of EXPOSURE ON APPLE QUALITY

ABSTRACT. The use of methyl bromide (MeBr) as a fumigant to control codling moth in 'Delicious'apples resulted in a loss of firmness, internal color and therefore a reduction in the amount of acceptable fruit. Time and temperature of MeBr exposure were directly related to firmness and internal color loss. As the exposure time was increased beyond 2 h and exposure temperature above 6°C firmness and internal color loss were accelerated. an 8-day ambient storage period exacerbated firmness and internal color loss as time and temperature of MeBr exposure were increased. A fumigation regime of 56 g MeBr/m³ at 6°C for 2 h resulted in acceptable fruit during a 60 day refrigerated storage period. Increased exposure times or temperatures beyond 56 g MeBr/m³ at 6°C for 2 h resulted in unacceptable firmness and internal color loss, coupled with a major loss in acceptable fruit.     

Moisture Loss and Lipid Oxidation for Precooked Ground-Beef Patties Packaged in Edible Starch-Alginate-Based Composite Films

Edible films of starch‐alginate (SA), starch‐alginate‐stearic acid (SAS), SA‐tocopherol, SAS‐tocopherol, tocopherol‐coated SA film, and tocopherol‐coated SAS film were evaluated for their effectiveness in maintaining quality of precooked beef patties stored at 4 °C. Patty weight loss, moisture loss, 2‐thiobarbituric acid‐reactive substances value, the formation of hexanal, pentane, and total volatiles of samples differed with film composition. SAS‐based films were more effective (P < 0.05) in controlling moisture loss than lipid oxidation. Tocopherol‐treated films were more effective (P < 0.05) in inhibiting lipid oxidation than were nontocopherol films. Most of the tested edible films were not as effective as polyester vacuum bags in retarding moisture loss and lipid oxidation.     

Development of a methyl bromide collection system for fumigated farmland

Recent research has indicated that up to 73% of the methyl bromide (MeBr) applied to agricultural farmland is ultimately emitted to the atmosphere despite the practice of complete coverage of the fields with polyethylene (PE) tarp. To reduce the emission of MeBr, several techniques have been investigated. An alternative that has received little consideration is the collection and recycle or treatment of MeBr emissions. We investigated the potential of using a two-layer tarp system for collecting the MeBr. Laboratory experiments with a small two-layer diffusion reactor were conducted to determine the mass transfer coefficient (K) of MeBr through tarps and to validate a model of the collection system. For PE tarps K was 1.15 x 10(-6) m s-1 at 20 degrees C and 5.2 x 10(-6) m s-1 at 60 degrees C. K for so-called virtually impermeable films ranged from 4.6 x 10(-10) m s-1 to 1.3 x 10(-8) m s-1. The mathematical model was then used to simulate a full scale fumigant field application. Results indicate excellent agreement between the model, laboratory experiments, and previous field studies. Total emission from the field was a function of the air exchange rate through the swept volume between the two layers, the length of time the field is covered by the collection system, and the mass transfer coefficient of MeBr though the tarps. The results indicate that the proposed two-layer system can be very effective in collecting MeBr emissions from fumigated farmland.     

Formulation, characterization, and efficacy of an adenosine-containing dissolvable film for a localized anti-wrinkle effect

A water-dissolvable film was developed to topically deliver adenosine for a localized anti-wrinkle effect. The polymers used to produce the film were cellulose derivatives. An aqueous mixture of the film components was made, coated on a liner, and then dried to form a solid film. No preservatives were added and the film was shown to be stable over time. The film quickly dissolves in water to form a uniform layer at the surface of the skin, as shown by scanning electron microscopy. The film layer can still be visualized on the wrinkle 6 h after being applied on the skin. A randomized, placebo-controlled, investigator-blind study was conducted in female volunteers to assess the efficacy of the 1% adenosine-containing dissolvable film. After 3 weeks and 8 weeks, a twice daily application led to a significant decrease in the skin roughness parameters as observed using fast optical in vivo topometry (FOITS). These results demonstrate that water-dissolvable films may be used as novel, preservative-free, cosmetic delivery systems.     

Soy protein – Poly (lactic acid) bilayer films as biodegradable material for active food packaging

The preparation and characterization of biodegradable bilayer films from isolated soy protein (SPI) and poly (lactic acid) (PLA) were carried out in this work. The films showed high transparency and strong adhesion between layers without adding an extra component, or without chemically modifying the film surfaces. The application of the PLA layer largely increased the mechanical properties of the films with respect to those of pure SPI films. Furthermore, the hydrophobic characteristics of the PLA layer improved film performance under conditions in which water was involved, markedly decreasing the amount of total soluble matter, the swelling index and the water vapor permeability. The biodegradation under soil burial conditions was evaluated measuring weight loss as a function of time, showing a two-step degradation and a faster degradation rate for the protein component compared to those of PLA layer. The films prepared were evaluated as active packaging by incorporation of an antifungal and an antibacterial agent (natamycin and thymol, respectively) to the SPI layer, showing a marked growth inhibition of mold, yeast and two strains of bacteria by in-vitro microbiological assays.     

IRRADIATION AS AN ALTERNATIVE TO METHYL BROMIDE FOR QUARANTINE TREATMENT OF STONE FRUITS1

Irradiation can be used with cherries, apricots, or peaches as a quarantine treatment at 300gy's or less with little quality loss. Either irradiation or methyl bromide (MeBr) can be used as a quarantine treatment for ‘Bing’‘and ‘Rainier’ sweet cherries with acceptable results and similar fruit quality. Difference in stem condition and bruising were more evident for irradiated ‘Rainier’ cherries than for MeBr treated ‘Rainier’ cherries, but these differences were small. Use of irradiation results in some firmness loss, for ‘Bing’ cherries when compared with MeBr, but irradiation treatment of cherries does not result in a loss of fruit and stem color, where the use of MeBr doses result in both fruit and stem color loss. Apricots (‘Perfection’ and ‘Rival’) and peaches (‘Regina’) are tolerant to irradiation at 300 gy with little quality loss. Loss of firmness, color changes and increased internal breakdown are evident in both apricots and peaches at irradiation dose above 600 gy. If irradiation dose above 600 gy is required to meet quarantine requirements unacceptable qualidy loss will occur in cherries, apricots and peaches.     

完全降解纸基棉质地膜的制备及性能研究

利用废弃棉纤维经湿法造纸工艺制备可完全降解农用地膜.通过正交试验对抄造工艺进行优化设计,抄造制得的纸基棉质地膜小样经石蜡浸溃、聚乙烯醇(PVA)胶液后处理,得到纸基棉质地膜试样,并对试样的主要物理性能进行了测试.结果表明:在面密度35g/m2、胶液PVA质量分数4％、打浆度40°SR工艺条件下制得的纸基棉质地膜具有良好...     

纳米ZnO/HDPE膜对奶酪的抗菌保鲜性

通过熔融共混法制备得到ZnO含量为0.5%纳米ZnO/高密度聚乙烯(HDPE)复合膜,对其进行表征和性能测试,并考察其对奶酪的保鲜性。结果表明,复合膜中的纳米ZnO粒子分散较均匀,相比于HDPE膜,纳米复合膜的力学性能和阻隔性能都得到一定程度的提高。该膜对奶酪包装后进行感官分值、pH值和微生物生长状况的测试发现,与纯HDPE膜所包装的奶酪相比,纳米ZnO/HDPE复合膜所包装奶酪的感官分值由66.0提高到73.0;pH值约为6.167,更接近标准样;奶酪溶液铺平板并培养48h后的菌落数(32×103CFU/mL)少于HDPE膜(82×103CFU/mL),这表明纳米ZnO/HDPE复合膜对奶酪上的微生物生长有很强的抑制作用,具有一定的抗菌保鲜性。     

Round scad protein-based film: Storage stability and its effectiveness for shelf-life extension of dried fish powder

Storage stability of different round scad (Decapterus maruadsi) protein-based films including (1) control film without palm oil and chitosan, (2) film with 25% palm oil (glycerol substitution) and (3) film with 25% palm oil and 40% chitosan (protein substitution) was investigated. During storage (54% relative humidity, 28-30 °C), tensile strength (TS) of the films without and with 25% palm oil or 25% palm oil in combination with 40% chitosan increased continuously, while elongation at break (EAB) decreased markedly when storage time increased up to 8 weeks (p < 0.05). No changes in water barrier properties were observed throughout the storage time up to 4 weeks (p > 0.05). Film solubility slightly increased but protein solubility decreased continuously during storage (p < 0.05). All films became darker and more yellowish as storage time increased. When round scad muscle protein-based films were used to cover dried fish powder, the samples covered with the film containing 25% palm oil and 40% chitosan showed lower thiobarbituric acid reactive substances (TBARS) and yellowness than other samples during the extended storage up to 21 days (p < 0.05). No differences in moisture content of all samples covered with different films were noticeable (p > 0.05), except those covered with HDPE, which had the lowest moisture content. Thus, round scad protein-based film incorporated with palm oil and chitosan could be a promising packaging material to prevent lipid oxidation in oil enriched foods.     

High and low rigor temperature effects on sheep meat tenderness and ageing

Immediately after electrical stimulation, the paired m. longissimus thoracis et lumborum (LT) of 40 sheep were boned out and wrapped tightly with a polyethylene cling film. One of the paired LT's was chilled in 15°C air to reach a rigor mortis (rigor) temperature of 18°C and the other side was placed in a water bath at 35°C and achieved rigor at this temperature. Wrapping reduced rigor shortening and mimicked meat left on the carcass. After rigor, the meat was aged at 15°C for 0, 8, 26 and 72 h and then frozen. The frozen meat was cooked to 75°C in an 85°C water bath and shear force values obtained from a 1×1 cm cross-section. The shear force values of meat for 18 and 35°C rigor were similar at zero ageing, but as ageing progressed, the 18 rigor meat aged faster and became more tender than meat that went into rigor at 35°C (P<0.001). The mean sarcomere length values of meat samples for 18 and 35°C rigor at each ageing time were significantly different (P<0.001), the samples at 35°C being shorter. When the short sarcomere length values and corresponding shear force values were removed for further data analysis, the shear force values for the 35°C rigor were still significantly greater. Thus the toughness of 35°C meat was not a consequence of muscle shortening and appears to be due to both a faster rate of tenderisation and the meat tenderising to a greater extent at the lower temperature. The cook loss at 35°C rigor (30.5%) was greater than that at 18°C rigor (28.4%) (P<0.01) and the colour Hunter L values were higher at 35°C (P<0.01) compared with 18°C, but there were no significant differences in a or b values.     

A new oxygen barrier film reduces aerobic deterioration in farm-scale corn silage

Recently, many studies have focused on the aerobic deterioration of corn silage at the farm level, because a large part of the product stored in horizontal silos is exposed to air and is more prone to spoilage. The most important factor influencing the preservation of forage ensiling is the degree of anaerobiosis that is usually achieved with sheets of polyethylene. A new black-on-white (125-μm) coextruded oxygen barrier (OB) film has been developed for silage sealing and was tested in the present experiment to assess the effects on fermentation quality, dry matter losses, and yeast and mold counts at opening of whole-crop corn bunker silos compared with conventional polyethylene (ST) film. Two trials were carried out on 2 commercial farms. The bunkers were divided into 2 parts along the length so that half of the feedout face would be covered with ST film and the other half with OB film. Eight plastic net bags with well-mixed fresh material were weighed and buried in the upper layer of the bunker, and 4 bags were buried in the central part. The silos were opened for summer consumption and were fed out at different rates (19 vs. 33 cm/d). The bags were unloaded, weighed, and subsampled to analyze the DM content, pH, lactic and monocar-boxylic acids, ammonia, yeast and mold counts, and aerobic stability. The pH of the peripheral silage was different under the 2 films, with a lower value in the OB treatment. The OB film on farm 1 affected the silage dry matter losses, which were reduced 3.7 times in comparison with the ST film sealing. On farm 2, although the dry matter losses were numerically higher in the silage sealed with the ST film compared with OB film (9.0 vs. 5.9%, respectively), the difference was not statistically significant. However, the corn silage sealed with the ST film was less stable than the silage sealed with the OB film. The results indicate that the new OB film is a promising tool to constrain spoilage and dry matter losses under critical farm conditions, when inadequate amounts of silage are removed daily. The OB film further improved the stability of the corn silage in the peripheral areas of the silos even when a proper harvest-to-feedout management was implemented.     

Paste viscosity of rice starches of different amylose content and carboxymethylcellulose formed by dry heating and the physical properties of their films

Starch modified by combination with sodium carboxymethylcellulose (CMC) has been reported to have improved film properties. In this study, rice starches with different amylose content were heat-treated in a dry state after being impregnated with low or medium-viscosity CMC. Noticeable change was found in pasting properties of the starches after dry heat treatment with CMC. It indicated that crosslinkage occurred between the starch and CMC. The waxy starch showed significant change in viscosity throughout pasting after dry heating with CMC, suggesting that the ester bonds were mostly formed between the hydroxyl groups in amylopectin branches of rice starch and carboxylate acid groups of CMC. Particle size also increased after heat treatment with CMC. The modified starch-based films showed improvement in the tensile strength. Both water vapor and oxygen permeability reduced for the modified starch-based films. Dynamic mechanical analysis (DMA) study showed that the values of G′ of modified starch-based film were higher than those of native starch-based film over the temperature range −40 to 60 °C. The heating process with CMC could be used as a modification method for starch and provide desirable properties of starch-based films.