空调控温储藏稻谷品质变化规律的研究

针对北方地区夏季稻谷储藏期间存在仓温高、上层粮温上升快易发热、品质陈化速度快等突出问题,在平房仓内采用空调进行控温储粮工艺研究,分析粮堆上层稻谷的温度、水分以及品质指标变化规律。结果表明:随着储藏时间的延长,实验仓和对照仓粮堆上层稻谷的水分、发芽率、品尝评分值均逐渐降低,与储藏时间呈线性负相关关系。脂肪酸值逐渐增高,与储藏时间呈线性正相关关系,直链淀粉与储藏时间呈现先上升后下降的趋势。整个储藏期内,实验仓的粮堆上层稻谷各品质指标的变化幅度均明显小于对照仓,储藏至第19个月时,实验仓稻谷品质好于对照仓。实仓应用后,上层粮温始终保持在20℃以下,无储粮害虫发生,且减少了储粮水分损失,并有效延缓了夏季粮食劣变速度,实现了稻谷准低温绿色安全储藏,具有明显的经济效益和社会效益。     

Changes in texture,cellular structure and cell wall composition in apple tissue as a result of freezing

Apple texture is one of the critical quality features for the consumer. Texture depends on several factors that are difficult to control and which change with freezing. To better understand the mechanisms involved in the texture degradation of apple tissues following freezing/thawing, our approach was to combine mechanical properties, cellular structure and cell wall composition measurements on fresh and thawed apples (Granny Smith) after three different freezing protocols (at ?20 °C, ?80 °C and ?196 °C). This work highlighted the interest of applying macrovision and image texture analysis to quantify the freezing effects on cellular structure and ice crystal size. Freezing at ?20 °C and after immersion into liquid nitrogen were the protocols affecting the most fruit texture leading to cell membrane breakage resulting in cell wall collapse and tissue breakage, respectively, which accounted for the mechanical behaviour of the samples. All freezing protocols induced vacuole burst showing that the turgor pressure preservation remains critical during the freezing process.     

Evaluation of a biologically active cover for mitigation of landfill gas emissions

Landfills are the third largest source of anthropogenic CH4 in the United States, and there is potential for reduction in this source of greenhouse gases and other contaminants. The objective of this work was to contrast emissions of CH4 and non-methane organic compounds (NMOCs) from landfill cells covered with soil or a biologically active cover consisting of yard waste compost. On the basis of four field campaigns over 14 months, CH4 emissions from the biocover (BC) varied from -1.73 to 1.33 g m(-2) d(-1), with atmospheric uptake measured in 52% of tests. BC emissions did not increase when the gas collection system was turned off. Uptake of atmospheric CH4 was measured in 54% of tests on the soil cover (SC) when the gas collection was system active and 12% when the gas collection system was off. Many (26%) relatively high fluxes (>15 g m(-2) d(-1)) were measured from the SC as were some dramatic effects due to deactivation of the gas collection system. In tests with positive emissions, stable isotope measurements showed that the BC and SC were responsible for oxidation of 55% and 21% of the CH4 reaching the bottom of the respective cover. Seven of the highest 10 NMOC emissions were measured in the SC, and 17 of 21 fluxes for speciated organic compounds were higher in the SC. The relationship between CH4, NMOC, and individual organic compound emissions suggested a correlation between CH4 and trace organic oxidation. BCs can reduce landfill gas emissions in the absence of a gas collection system and can serve as a polishing step in the presence of an active system.     

Field application of partitioning gas tracer test for measuring water in a bioreactor landfill

Two field-scale partitioning gas tracer tests (PGTTs) were performed to evaluate the utility of the PGTT method for measuring water saturation and moisture content in a full-scale bioreactor landfill, where waste biodegradation resulted in elevated temperatures and significant landfill gas production. The average water saturation and moisture content were measured for waste volumes of approximately 20 m(3) and results were compared to gravimetric measurement of moisture content made on samples collected from the landfill. In the center of the landfill, the moisture content estimated from the PGTT was Mc = 0.26 +/-0.03, which was nearly identical to the gravimetric measurement of waste samples taken from the same region (Mc = 0.28). PGTT-estimated moisture contents in a dry area of the landfill were much smaller (Mc = 0.10+/-0.01) and consistent with available gravimetric measurements. Biodegradation of tracers and temporal variations in landfill gas production were minimal and did not influence the tests. These field experiments demonstrate the utility of the PGTT method for measuring water saturation and estimating moisture content in bioreactor landfills with active waste degradation and generation of landfill gases. However, use of the PGTT to estimate the in situ moisture content requires estimates of the refuse porosity, dry bulk density, and temperature, which might limit its application.     

Changes in free amino acids during chilled storage of hake (Merluccius merluccius L.) in controlled atmospheres and their use as a quality control index

This paper examines the evolution of FAAs in hake stored in ice and kept in controlled atmospheres for 33 days with four different gas mixes (CO₂/O₂/N₂): M1 (60/15/25), M3 (40/40/20), M4 (60/40/0), and M5 (40/60/0). The most abundant FAAs in hake muscle are threonine, glutamic acid, glycine, alanine, #-alanine, tryptophan, 1-methylhistidine, and anserine. Anserine was the compound initially present in the highest concentration (61.65 mg/100 g of fish wet weight). As storage progressed, anserine concentrations fell, the smallest decrease being found in the lot kept in M1. At the end of storage the lot with the lowest level of anserine was M5C, which contained the highest O₂ levels. The levels in the other lots were very similar. This fall in anserine coincided with an increase in 1-methylhistidine and #-alanine, the two amino acids to which it becomes hydrolyzed. As well as the fall in anserine, there was a progressive increase in muscle tryptophan during storage of the hake. This increase became more pronounced from day 12 of storage and was greatest in the control and lots M1C and M3C, which relates to the results of the other biochemical indexes. Both anserine and tryptophan could be used as quality control indexes for chilled hake. In general, no clear relationship was found between the effect of the atmosphere and the behavior of the FAAs.     

Emissions reductions as a result of automobile improvement

Remote sensing of light duty vehicle on-road tailpipe exhaust has been used to measure on-road mass emissions of automobile fleets in Denver for 13 years and in two other U.S. cities for 5 years. Analysis of these fleets shows that newer automobiles, during a period of fairly constant new car standards, have become continually less polluting independent of measurement location. Improving emissions control technology spurred by federal regulations is thought to have brought about these trends.     

Bayesian analysis of a reduced-form air quality model

Numerical air quality models are being used for assessing emission control strategies for improving ambient pollution levels across the globe. This paper applies probabilistic modeling to evaluate the effectiveness of emission reduction scenarios aimed at lowering ground-level ozone concentrations. A Bayesian hierarchical model is used to combine air quality model output and monitoring data in order to characterize the impact of emissions reductions while accounting for different degrees of uncertainty in the modeled emissions inputs. The probabilistic model predictions are weighted based on population density in order to better quantify the societal benefits/disbenefits of four hypothetical emission reduction scenarios in which domain-wide NO(x) emissions from various sectors are reduced individually and then simultaneously. Cross validation analysis shows the statistical model performs well compared to observed ozone levels. Accounting for the variability and uncertainty in the emissions and atmospheric systems being modeled is shown to impact how emission reduction scenarios would be ranked, compared to standard methodology.     

Captan residue reduction in apples as a result of rinsing and peeling

Apples, treated with captan for disease control in a commercial orchard in Quebec, Canada, were collected and sorted into post-harvest preparation types (no preparation; rinse; rinse and peel). Captan residues were greatest (25.5–5100 ng/g) in apples with no post-harvest preparation and lowest (0.146–136 ng/g) in apples that had been rinsed and peeled prior to extraction and analysis. Residues were significantly lower (p = 0.003) in apples that had been rinsed prior to extraction than in apples with no post-harvest preparation. Similarly, apples subjected to rinsing and peeling had significantly lower captan residues than had apples that had been rinsed alone (p < 0.0001). Although captan residues in rinsed apples were approximately 50% lower than those in apples that received no post-harvest preparation, the reduction associated with peeling of apples was much greater (98%). Estimated mean captan intakes resulting from consumption of raw apples were established and single day intakes, based on apples with no preparation, ranged from 2.58 μg/kg in females >70 years to 9.48 μg/kg for individuals aged three years (at this age no distinction is made between males and females). Mean intakes estimated using rinsed and peeled apples were approximately two orders of magnitude lower than intakes estimated using apples with no post-harvest preparation, demonstrating the effect of post-harvest preparation on captan intakes. Mean captan intake estimates from all post-harvest preparation types were well below the World Health Organization acceptable daily intake of 100 μg/kg/day, based on raw apple consumption.     

Changes in quality characteristics of fresh-cut jujubes as affected by pressurized nitrogen treatment

When fresh-cut jujubes are subjected to pressurized nitrogen treatments, the nitrogen gas dissolves into water and forms clathrate hydrates which ultimately lead to restriction in water mobility. Fresh-cut jujubes were, respectively, treated with 1.0 MPa nitrogen, 1.5 MPa nitrogen, 1.9 MPa nitrogen and 1.9 MPa air for 30 min at 4 °C and without pressurized treatment(control) and then stored at 4 °C and 80 % relative humidity (RH) for 12 days. Physiological, textural, chemical, and microbial attribute were determined every 2 days. Results indicated that pressurized nitrogen treatments carried out at 1.5 MPa successfully inhibited respiration, water loss, softening, chlorophyll degradation, and color change. The treatments also significantly reduced loss of ascorbic acid and soluble solids. Treated fresh-cut jujubes carried significantly less microbial population. Thus, it was concluded that pressurized nitrogen treatment was beneficial to preserve quality of fresh-cut jujubes.     

Image analysis of microstructural changes in almond cotyledon as a result of processing

Release of oil from nuts due to damaged cellular structures can degrade the quality of products incorporating nuts. The aim of this study was to investigate the effects of different processing conditions on microstructure of almond tissue and to quantify these changes using image processing. Spinning disk confocal fluorescence microscopy was used for imaging changes in microstructure of almonds as a function of different thermal processing of almonds. Multiple staining of Nile Red and Calcofluor White was applied to differentiate cell wall structures and oil bodies within individual almond cells without chemical fixation. An algorithm for image processing, included image preprocessing, segmentation, and determination of morphological features of segmented objects, was developed. Oil-roasting processes (140 °C and 150 °C) were found to have a significant impact on microstructure of almonds when compared to the hot air-roasting and blanching processes. Oil-roasted almond at 150 °C had a greater cellular damage due to cell wall and membrane rupture. These changes in microstructure of almonds would make them slightly more susceptible to release oil during storage. The image analysis presented allows quantitative evaluation for the effect of different processing on almond microstructure.     

热风黏结机喷风口喷风均匀性分析

提出热风黏结机喷风口喷风均匀的条件,介绍喷风口形式。以ZW2784系列和ZW2785系列热风黏结机为例,分别对两种类型的热风黏结机的喷风口喷风均匀条件进行计算,结果满足喷风口均匀送风条件,并指出圆孔形喷风口下方放置匀风板及变截面风道中采用弧形导流板的设计能进一步改善喷风均匀性。     

Aflatoxin accumulation in whole crop maize silage as a result of aerobic exposure

BACKGROUND: Most of the maize silage stored in horizontal silos is exposed to air and can be spoiled by fungi. Potentially toxigenic fungi have been found in maize silage, and about 300 mycotoxins have been detected. Among these mycotoxins, the most harmful for feed and food safety are aflatoxins. The aim of the study was to set up a specific method to detect aflatoxins in maize silage, and to investigate whether aflatoxin contamination in maize silage depends on the level of field contamination of the crop, and whether the occurrence of aerobic spoilage during ensiling has any effect on the final contamination of the silage. RESULTS: A method for the determination of aflatoxin B₁, B₂, G₁ and G₂ in maize silage using high‐performance liquid chromagraphy with fluorescence detection has been developed and validated. Recoveries of aflatoxin B₁, B₂, G₁, and G₂ spiked over the 0.25 to 5 µg kg^?1 range averaged 74–94%. The results of laboratory scale and farm scale ensiling experiments indicated that aflatoxins could increase when silage is exposed to air during conservation or during the feed‐out phase. CONCLUSIONS: The method here proposed to detect aflatoxins in silages has proved to be sensitive and is able to detect levels of 0.1 and 0.5 ng mL^?1 for AFB₁ and AFG₁, and between 0.025 and 0.125 ng mL^?1 for AFB₂ and AFG₂. This study also provides evidence of aflatoxin accumulation in whole crop maize silage as a result of aerobic exposure. Copyright © 2011 Society of Chemical Industry     

Hydrogen sulphide production in eggs and egg products as a result of heating

The nature of the reaction by which H₂S is produced from eggs and egg products during heating was investigated. The possibility of an enzymic reaction, as supposed by others, was examined by using inhibitors for the enzyme mentioned and by heat-inactivation. In both cases the H₂S production was not inhibited. From the stabilities of cysteine, glutathione and egg white determined by H₂S production at different temperatures, it was concluded that the production from egg white must be the result of a non-enzymic reaction from the protein(s). The influence of various factors was investigated. Both ionised SH— and S—S groups are involved in the reaction, since the pH and the S—S/SH ratio are the main factors determining H₂S production. H₂S production increases at higher temperatures and more alkaline pH values. It was shown that in addition to H₂S, lanthionine and NH₃ were present as reaction products.     

Changes in water quality during heating in electromagnetic and gas heated pans and the relationship between water quality changes and temperature increase rate

Relatively large changes in the indicators of water quality, such as pH, hardness, and bicarbonate content, were observed during electromagnetic heating of pans of different tap waters and compared with pans heated by liquid natural gas (LNG) or liquid petroleum gas (LPG). For example, the pH and hardness of Hiroshima tap water were increased from 7.35 to 9.27 and from 19.0 to 35.7 mg L^?1, respectively, during 20 min of electromagnetic heating. When tap water from Tokyo was subjected to electromagnetic heating, the water hardness of 74.2 mg L^?1 was increased by 52% after 20 min of heating. Such water quality changes were observed consistently in several tap water samples across Japan. These changes showed a close correlation with rates of temperature increase. It was suggested that mineral components (Ca and Mg), which were attached on the stainless steel surface of the pans might be released into the tap water with high calorific heating.