计算流体力学技术在粮食储藏中的应用

计算流体动力学(computational Fluid Dynamics,简称CFD)是通过计算机数值计算和图像显示,对包含有流体流动、热量和质量传递等相关物理现象所做的分析、计算和优化的数值模拟工具。通过CFD技术在储粮通风工程中的应用实例,对CFD技术进行了介绍,并对采用CFD技术模拟储粮中的通风过程中流动、热湿传递过程和生态系统的研究现状进行了综述,探讨了采用CFD对储粮中的流动、传热传质过程进行数值模拟的优势以及未来发展趋势。     

The efficacy of sieving, filth flotation and Tullgren heat extraction for detecting various developmental stages of Tribolium castaneum and Ephestia kuehniella in samples of wheat grain, flour and semolina

A prerequisite for effective pest risk management in food is the unbiased interpretation of results obtained by various detection methods. In this study we compared the sensitivity of filth flotation tests, sieving and heat extraction in Tullgren–Berlese funnels for detecting insect contaminants. Samples of wheat grain, flour and semolina were contaminated with eggs, juveniles and adults of Tribolium castaneum, and eggs or larvae of Ephestia kuehniella. Calibration methods were applied for every detection method, and total and sample recoveries and detection limits were calculated for each method, food substrate and contaminant type. The tested contaminants were not detected on a qualitative level by any single technique, instead a combination of techniques was necessary for detection. Sieving was the method with the highest total recoveries, ranging from 90 to 100%. Filth flotation was a uniquely effective for egg detection, with total recoveries ranging from 65 to 95%. The extraction of adults and larvae of both species in Tullgren–Berlese funnels failed in semolina and flour, and was of very limited success in grain. The detection limits for sieving were from 1 to 16 contaminants/kg commodity. The detection limits for filth flotation were from 224 to 508 eggs, and 58 to 507 adults or larvae/kg commodity. The sample recoveries were usually influenced by sample size, species, stadium and their interactions, and indicated how to optimize method protocols. The calibration of methods provided estimates of contaminant densities different from those obtained without calibration. Our work revealed that some currently used methods are not sensitive enough to detect all stages of insect pests, or in some cases, low levels of pest infestation. This lack of sensitivity potentially enables the infested cereal food product to continue down the food processing chain even after laboratory inspection.     

坨首站直馏柴油非加氢改质工艺的技术研究

优选出坨首站直馏柴油的最佳非加氢精制工艺.根据坨首站原油之直馏柴油的理化性质,制备SD化学精制剂及SD01络合捕集剂,并采用此项非加氢技术对原料油进行精制.通过考查精制后柴油的主要理化性质,并进行储存实验,确定直馏柴油的最佳精制工艺.得到最佳工艺条件:加剂量为1∶300,在温度为20～50℃下搅拌反应10 min,在此精制条件下,直馏柴油各项理化性质可达到国家标准GB252-2000的要求.与加氢精制相比,此方法适用于没有加氢能力的中小型炼厂.     

甜菜含水率与还原糖含量间的相关性及对贮藏的影响

试验证明:收获期甜菜含水量与还原糖含量成正相关,含水量和还原糖含量高的甜菜不耐贮藏。生产上可以通过收获前限制灌水及施氮肥等栽培措施,降低收获前甜菜的含水量和还原糖含量。贮藏中随着时间的推移甜菜的含水量下降,而还原糖含量增加,二者成负相关,实践中采取相应减少贮藏甜菜失水的措施,使含水量下降速度缓慢,适当的大堆贮藏效果好于小堆贮藏。     

Effect of the absence of lipoxygenase isoenzymes on the storage characteristics of rice grains

Three varieties of paddy rice with and three varieties without lipoxygenase (LOX) isoenzymes were stored at room temperature, in dark conditions for 42 months. Insect damage and viability were investigated during that time. Varieties without LOX-1,2 and their offspring were screened with a rapid method of estimating LOX isoenzymes, and subjected to an accelerated-ageing experiment. The results indicated that in varieties without LOX-1,2, after long storage, rice quality was normal, but for varieties with LOX-1,2, rice quality deteriorated. With increase of storage time, the germination rate of the seed of most varieties decreased greatly except for varieties without LOX-1,2 where there was almost no change in the germination rate. In varieties without LOX-1,2 and their offspring, after an accelerated ageing experiment the germination rate of some varieties changed slowly, but with others, the germination rate changed quickly. This indicated that a definitive factor, which influenced the life of seeds, may be the loss of LOX-1,2. During storage, there was also a significant difference in the degree of insect damage. In varieties without LOX-3 insect damage was lower, but in varieties with LOX-3 insect damage was higher. Therefore, the absence of LOX-3 may be very important in insect resistance in rice grain.     

1-MCP处理对采后中华寿桃品质的影响

以中华寿桃为试材,研究了1-甲基环丙烯(1-MCP)对采后桃果实品质的影响。结果表明,在20℃下,以0.1μL/L的1-MCP处理桃果24h,能有效地延缓贮藏期间(贮藏温度2℃)桃果实硬度的下降。以浓度0.5～1μL/L的1-MCP处理桃果24h,可显著地抑制果实硬度和可滴定酸含量的下降,同时也延缓了可溶性果胶含量的上升。以浓度1μL╱L的1-MCP处理桃果12、24或48h,其结果显示,处理桃果24h的效果明显优于12或48h的处理。     

The influence of storage practices on aflatoxin contamination in maize in four agroecological zones of Benin, west Africa

Aflatoxin level in 300 farmers’ stores in four agro-ecological zones in Benin, a west African coastal country, were determined over a period of 2 years. At sampling a questionnaire was used to evaluate maize storage practices. Farmers were asked what storage structure they used, their storage form, storage period, pest problems in storage and what was done against them. Beninese farmers often changed their storage structures during the storage period, transfering the maize from a drying or temporary store to a more durable one. Most of the farmers complained about insects damaging stored maize. Often, storage or cotton insecticides were utilized against these pests. Regression analysis identified those factors that were associated with increased or reduced aflatoxin.

Maize samples in the southern Guinea and Sudan savannas were associated with higher aflatoxin levels and the forest/savanna mosaic was related to lower toxin levels. Factors associated with higher aflatoxin were: storage for 3–5 months, insect damage and use of Khaya senegalensis-bark or other local plants as storage protectants. Depending on the agroecological zone, storage structures that had a higher risk of aflatoxin development were the “Ago”, the “Secco”, the “Zingo” or storing under or on top of the roof of the house. Lower aflatoxin levels were related to the use of storage or cotton insecticides, mechanical means or smoke to protect against pests or cleaning of stores before loading them with the new harvest. Fewer aflatoxins were found when maize was stored in the “Ago” made from bamboo or when bags were used as secondary storage containers.     

芦笋MAP保鲜研究

对芦笋ＭＡＰ贮藏保鲜进行了研究,结果表明,初始气体浓度比例对失重影响不明显,而对感官评价值,ＶＣ含量、纤维素含量,叶绿素含量等影响较大,温度对芦笋ＭＡＰ劳苦的品质影响很大,特别是当温度超过５℃时,这种影响更为明显。对六种不同薄膜的研究表明,以低密度聚乙烯（ＬＤＰＥ）ＭＡＰ保鲜效果最好。在各种初始气体浓度比例中以５％Ｏ２＋５％ＣＯ２和１０％Ｏ２＋１０％ＣＯ２的ＭＡＰ贮藏保鲜效果最好,５℃下贮藏１８ｄ     

Chemical,enzymatical and textural changes during marination and storage period of sardine (<Emphasis Type="Italic">Sardina pilchardus</Emphasis>) marinades

In this study frozen fillets of sardine (Sardina pilchardus) were used to make marinades. The marinating process was performed in 7% acetic acid and 14% sodium chloride in barrels. The fish:solution ratio was (1.5:1). After the marination process, sardine fillets were packed in glass jars in two different formulations fish:solution ratio of (1.5:1); the first formulation contained 2% acetic acid and 4% sodium chloride with tomato sauce and spices and the other was 2% citric acid and 4% sodium chloride with lemon and also the same spices. Pasteurization process had been applied on half of the jars at 70 °C for 20 min. Chemical, enzymatical and textural changes during marination and 6 months storage period of sardine marinades were determined. The results obtained in proteolytic activities correlated well with the observed texture measurements according to time of storage. A decrease in the histidine content and an increase in glutamic acid and aspartic acid contents of marinated sardines were determined. Histamine levels were lower than the toxic limit (100 mg/kg) during the marination and storage period of sardine marinades.     

Analysis of isoflavone concentration and composition in soybean [<Emphasis Type="Italic">Glycine max</Emphasis> (L.)] seeds between the cropping year and storage for 3 years

The objective of this study was to examine the relation between storage period and isoflavone concentration and composition in soybean [Glycine max (L.) Merrill] seeds. Total isoflavones varied from 470.0 to 878.1 µg g^–1 over the three cropping years and there were significant differences between the soybean cultivars. Generally, the malonyl conjugates were in higher concentrations than were the other compounds, and the individual isoflavones varied with each cropping year. The Myeongjunamul (1998: 936.7 µg g^–1, 1999: 727.0 µg g^–1, 2000: 807.8 µg g^–1) cultivar had the highest concentration, on average. Regarding changes in isoflavones with storage period, the concentration decreased by 91.7 to 171.1 µg g^–1. Malonyldaidzin and malonylgenistin concentrations also decreased, and the concentration of glucosides increased slightly over the 3 years. Acetyldaidzin, acetylglycitin and glycitein could not be detected or were only found in very small concentrations. Pureun (–66.2 µg g^–1) and Myeongjunamul (–77.4 µg g^–1) cultivars showed little variation in isoflavone levels, whereas the concentration in Muhan (–295.4 µg g^–1) decreased markedly on average over the three storage years. There were also significant differences between the cultivars. Our study suggests that it might be feasible to improve the storage methods of soybeans to preserve them for longer periods, which would have benefits for both their import and their export.S.H. Kim and W.S. Jung contributed equally to this work.