Arsenic in cooked seafood products: study on the effect of cooking on total and inorganic arsenic contents

Total and inorganic arsenic contents were analyzed in cooked seafood products consumed in Spain during the period July 1997-June 1998: hake, meagrim, small hake, anchovy, Atlantic horse mackerel, sardine, bivalves, crustaceans, squid, and salted cod. Various cooking treatments were used (grilling, roasting, baking, stewing, boiling, steaming, and microwaving). The results obtained were compared statistically with those found previously in the same products raw, and they showed that after cooking there was a significant increase in the concentration of total arsenic for salted cod and bivalves, and in the concentration of inorganic arsenic for bivalves and squid. The mean content of inorganic arsenic was significantly higher in bivalves than in any other type of seafood. For the Spanish population, the mean intake of total arsenic estimated on the basis of the results obtained in this study is 245 microg/day. The intake of inorganic arsenic (2.3 microg/day) represents 1.7% of the World Health Organization provisional tolerable weekly intake (PTWI), leaving an ample safety margin for this population, which has a very high consumption of seafood.     

Organoarsenical species contents in cooked seafood

The organoarsenical species arsenobetaine (AB), arsenocholine (AC), tetramethylarsonium ion (TMA+), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) were determined in 64 cooked seafood products (fish, bivalves, squid, crustaceans) included in a Total Diet Study carried out in the Basque Country (Spain). For cooking, various treatments were employed (grilling, roasting, baking, stewing, boiling, steaming, microwaving). The results obtained show that in cooked seafood AB is the major species, followed by DMA and TMA+. AC and MMA are minor species. The results in cooked seafood were compared with the arsenic species contents obtained for the same product raw. After cooking there was an increase in DMA for sardines and bivalves and an increase or appearance of TMA+ for meagrim, anchovy, Atlantic horse mackerel, and sardine. The data provided add to the very scant information available about organoarsenical species contents in cooked seafood.     

蒸煮工艺和化学成分对米饭应力松弛特性的影响

用4种工艺制作米饭，用质构仪测定米饭的应力松弛曲线，并分析米饭的主要化学成分，研究米饭的应力松弛参数与化学成分的关系，为米饭蒸煮工艺的优化和新型炊具的开发提供基础数据。结果表明，不同工艺蒸煮的米饭的应力松弛参数有较大的差异性，较低温度下蒸煮的米饭的硬度较大，较高温度下蒸煮米饭的黏性较大。米饭的平衡弹性系数E₀为15.754～89.323 Pa；衰减弹性系数E₁为34887.528～35213.051 Pa；松弛时间τ为0.130～0.179 s；松弛非线性指数n为0.019～0.054，黏度系数η为4538.085～6248.998 Pa·s。米饭为具有一定交联程度的黏弹性体，其松弛参数与米饭的化学成分有较大关系，蛋白质含量较高的米饭的E₀、τ和η较大；脂肪含量较高的米饭的E₀较小；直链淀粉含量较高的米饭的E₁和τ较小。建立的基于米饭的化学成分与米饭松弛参数的多元幂函数式方程具有较高的拟合精度。     

有机肥与无机肥在提高土壤肥力中的作用

以在山东禹城试验区持续近20年的定位试验为依据，对长期施用有机肥、无机肥、有机无机结合等不同施肥条件下的土壤养分演变进行了系统总结。结果表明，在同等施肥情况下，有机肥不但在增加土壤有机营养，改善土壤有机质质量等方面具有极其显著的作用，而且随着年限的增长，在增加土壤速效养分方面，有机肥的效果也逐渐超过无机肥。     

Organoarsenical species contents in fresh and processed seafood products

A study was carried out to determine organic species of arsenic in the main varieties of seafood consumed in the Basque country (Spain). The concentrations of arsenobetaine (AB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenocholine (AC), and tetramethylarsonium ion (TMA(+)) in 64 samples corresponding to different food items are presented. The study provides information about a possible distribution pattern of organoarsenical species in seafood products. AB was detected in all of the samples [0.3-104.1 microg g(-1) dry weight (dw)]. DMA was detected in all of the samples except squid and salted cod (0.027-1.757 microg g(-1) dw). MMA was detected only in certain fatty fish (0.004-0.028 microg g(-1) dw) and bivalves (0.031-0.047 microg g(-1) dw). AC was only present in some samples of lean fish (0.014-0.089 microg g(-1) dw), and TMA(+) was detected only in anchovy (0.039-0.169 microg g(-1) dw) and crustaceans (0.044-0.966 microg g(-1) dw).     

开垦对黑土有机质化学结构的影响

基于傅里叶红外光谱研究东北黑土开垦对土壤有机质化学结构特征的影响,探明各粒级团聚体及密度组分中有机质化学结构变化特征,为开垦黑土农田土壤有机质结构变化提供理论参考。依托中国科学院海伦农业生态试验站长期定位试验研究平台,以试验开垦前自然草地土壤为对照,选取开垦8年、没有有机物料投入的耕层（0～20 cm）土壤为研究对象,采用湿筛法、密度分组将土壤有机质分成不同组分,用傅里叶红外光谱仪测定原土及各组分有机质红外光谱,分析开垦对土壤有机质化学结构的影响。结果表明：开垦前后,有机质红外结构特征峰相似,均以多糖C—O和醇酚—OH为主。全土芳香族C C含量较开垦前显著减少4.77%,有机质稳定性下降6.32%。在>0.25 mm团聚体中芳香族C C和羰基C O相对强度较开垦前分别显著降低29.91%和27.16%,醇酚—OH相对强度显著增加15.60%;0.25～0.053 mm团聚体中,多糖C—O相对强度增加4.57%,脂肪族—CH相对强度显著减少23.85%。<0.053 mm团聚体中,脂肪族—CH相对强度显著减少16.33%。有机质游离态轻组（LF）、闭蓄态组分（OF）中多糖C—...     

有机无机肥配施对烟叶化学成分和品质的影响

通过饼肥与化肥不同比例配施研究得出,河南烟区中等肥力的褐土上以50%芝麻饼肥氮 50%化肥氮处理与单施化肥相比,提高了下、中、上3个部位烟叶饱和脂肪酸相对含量,降低了不饱和脂肪酸含量,表现为豆蔻酸和月桂酸相对含量增加,而亚麻酸和亚油酸含量降低。中部叶、上部叶石油醚提取物含量也得到提高,烟叶糖碱比适宜,化学成分较协调,烟叶品质得到改善,并缩小了不同部位间质量差异。     

Assessment of changes in soil organic matter after invasion by exotic plant species

Invasive exotic plants can modify soil organic matter (SOM) dynamics and other soil properties. We evaluated changes in particulate organic matter (POM) and carbon (C) mineralisation in adjacent plots invaded by Solidago gigantea, Prunus serotina, Heracleum mantegazzianum and Fallopia japonica, and non-invaded control plots on different soils in Belgium. Litter decomposition of S. gigantea and P. serotina was compared to that of the native species Epilobium hirsutum, Betula pendula and Fagus sylvatica. Disregarding the differences in site characteristics (soil texture, parental material and plant species), we argued that the invasion by S. gigantea and P. serotina enhance SOM dynamics by increasing C mineralisation in 2 out of 3 sites invaded by S. gigantea and in 1 out of 3 sites invaded by P. serotina; C in coarse POM (cPOM, 4,000–250 μm) and fine POM (fPOM, 250–50 μm) in 1 site invaded by S. gigantea and C content in total POM (tPOM, 4,000–50 μm) and the organo-mineral fraction (OMF, 0–50 μm) in 1 site invaded by P. serotina. H. mantegazzianum and F. japonica slowed down SOM dynamics by reducing C mineralisation in three out of four sites; C and nitrogen (N) of fPOM in the invaded compared with the non-invaded plots at one site invaded by H. mantegazzianum. However, N content of cPOM (4,000–250 μm) was higher in the invaded sites by F. japonica compared with the non-invaded plots. Our results indicated that the effects of invasion by exotic plant species were not species-specific but site-specific.     

长期施用化肥和有机肥对土壤有机碳和容重的影响

在长期定位试验的基础上,探讨了施用化肥和作物秸秆对土体土壤容重和有机碳空间变异的影响.研究结果表明,化肥的施用不仅影响耕层肥力性状,而且会使耕层以下的土壤容重降低和有机碳增加,从而立体地促进土壤肥力的提高,而施用秸秆则只能改善耕层范围的土壤肥力.不同施肥措施造成土壤肥力性状的立体差异主要是由于不同施肥对作物生长和土壤根系的影响差别造成的.化肥对土壤根系的促进作用要比作物秸秆大许多倍,从而使耕层以下有大量残根分布,这些残根促进了深层土壤容重的降低和有机碳的提高.     

Structural and chemical changes in pyrogenic organic matter aged in a boreal forest soil

biochar;charcoal;chronosequence;porosity;prescribed burning;soil amendment;X-ray microtomography     

作物营养从有机肥到化肥的变化与反思

二十世纪前,农业生产主要靠施用有机肥为作物提供营养,维持地力不衰,这一时期一般称为“有机营养”阶段。之后,化肥逐渐取代有机肥,成为作物养分的主要来源,农业生产进入以化肥养分供应为主的“无机营养”阶段。化肥的连续大量施用在作物增产方面发挥了巨大作用,也带来了不少问题,以致近年来出现了怀疑或否定农业生产中施用化肥的思潮。为此,本文回顾了植物营养学科的发展历程和我国化肥使用的历史,指出仅靠施用有机肥、种植豆科作物等传统的营养作物的方式难以满足农业生产对养分的需求,化肥与有机肥配合施用是我国农业发展的正确道路。目前生产中,化肥施用存在不合理和过量问题,有机肥施用方面,主要是集约化养殖业与种植业的不合理布局,存在种养分离,难以农业利用等养分管理问题。同时解决这两个问题,除采取已有的合理施肥技术及方法外,还应改变从植物营养角度只重视氮磷钾等无机养分的供应,拓宽为重视碳、氮、磷及钾等不同元素间的时空平衡关系;以农业生态系统养分资源高效循环利用为核心,采取不同方式实现有机–无机营养的结合,应避免陷入有机与无机营养的争论;从生物地球化学循环角度看待养分利用与管理问题,关注养分在田块、流域及区域尺度的流向及对土壤、水体及大气的影响;将科技与政策等有效结合,提高养分利用效率,减少养分损失,保障我国农业的健康持续发展。     

Effect of organic matter on changes in soil zinc fractions found in wetland soils

Abstract

Zinc fractions occurring in five wetland soils as a function of organic matter application and soil redox potential were studied under laboratory conditions. The results indicate that a large portion of native or added Zn is bound to the soil mineral component. Exchangeable and organic complexed Zn and Zn bound to amorphous and crystalline sesquioxides were found to be in dynamic equilibrium. Exchangeable and complexed Zn were positively correlated with both native and/or added organic matter, while Zn bound to the amorphous and crystalline sesquioxides were negatively correlated with added organic matter. As soil redox potential decreased, the amount of exchangeable and organic complexed Zn decreased, while Zn bound to the amorphous and crystalline sesquioxides increased. Zinc fractions examined varied, depending upon soil cation exchange capacity, clay and organic carbon content.     

Effect of cooking on banana and plantain texture

The effect of temperature and duration of cooking on plantain and banana fruit texture and cytpoplasmic and cell wall components was investigated. The firmness of both banana and plantain pulp tissues decreased rapidly during the first 10 min of cooking in water above 70 degrees C, although plantain was much firmer than banana. Cooking resulted in pectin solubilzation and middle lamella dissolution leading to cell wall separation (as observed by SEM). Dessert banana showed more advanced and extensive breakdown than plantain. Although dessert banana had a higher total pectin content than plantain, the former had smaller-sized carboxyethylenediaminetetraacetic acid (CDTA) soluble pectic polymers which are associated with plant tissues that have a propensity to soften. Plantain had higher levels of starch and amylose than banana but this was associated with a firmer fruit texture rather than a softening due to cell swelling during starch gelatinization. Different cooking treatments showed that cooking in 0.5% of CaCl(2) solution and temperatures below 70 degrees C had significant effects on maintenance of pulp firmness.     

Effect of pressure cooking on aflatoxin B1 in rice

The effect of pressure cooking on aflatoxin residues in polished rice was conducted to determine reduction of aflatoxin and mutagenic potentials. Three rice lots consisting of naturally contaminated, A. parasiticus-infested, and aflatoxin-spiked rice were steamed by ordinary and pressure cookers after they were washed with water. They were chemically analyzed for aflatoxins using a silica solid phase extraction tube and high-performance liquid chromatography (HPLC)-fluorescence detection (FD), and the presence of aflatoxin residues was confirmed using HPLC-electrospray ionization (ESI)-mass spectrometry (MS). An in vitro mutagenicity test with Salmonella typhimurium TA100 was employed to verify the results based on chemical analyses. The aflatoxin loss (78-88%) was notable after pressure cooking, and the reduction of aflatoxin-induced mutagenic potential (68-78%) was in good agreement with the HPLC results. It can be concluded that Koreans are safe from the aflatoxin-related risk if a pressure cooker is employed for cooking rice. The average Korean daily intake of aflatoxin through the consumption of staple rice would fall to 0.15 ng/kg bw/day, which would not exceed the established tolerable daily intake (0.40 ng/kg bw/day).     

Effect of cooking conditions on creatinine formation in cooked ham

The aim of this study was to evaluate the effect of different cooking procedures on the concentrations of creatine and creatinine and the ratio of creatinine/creatine in cooked ham. Two cooking methods (constant temperature and increasing temperature, constant T and DeltaT, respectively) were tested on different locations in porcine longissimus dorsi muscle and ham (semimembranosus, biceps femoris, and gluteus muscles). The results showed larger creatine conversion into creatinine in the surface layer than in the core as well as higher creatinine/creatine ratio values when applying the DeltaT in comparison to the constant T method. A correlation between the creatinine/creatine ratio and the heat treatment was established, and 15 samples of commercial cooked hams were analyzed to support these results. This creatinine/creatine ratio analyzed in the surface of the ham could be used as a rapid and nondestructive indicator to determine the effectiveness of the heat treatment in cooked ham processes.     

Effect of the chemical composition of industrial dusts on forest floor organic matter accumulation

The influence of dusts from aluminium (AP), zinc and lead (ZP1, ZP2), sintering (SP) and power (PP) plants on organic matter accumulation on the forest floor of a mixed oak-pine forest was studied in Niepo?omice Forest near Kraków, Poland. An artificial application of the dusts on experimental plots was used corresponding to 100, 500, 1000, 2000, and 5000 t km^?2. Increased organic matter accumulation was observed 5 yr following the addition of AP, ZP1 and ZP2 dusts, while SP and PP dusts at levels > 100 t km^?2 caused a slight decrease in litter accumulation. Statistical analysis indicated that Cd, Mn, Pb and Zn present in industrial dusts were responsible for the increase in litter accumulation, while some nutrients (e.g. K, Mg, Na) contained in the dusts might decrease organic matter storage to some extent.     

化肥施用量对有机基质栽培番茄养分吸收利用的影响

以番茄为试验材料, 以蛭石︰羊粪=2︰1 为基质配方, 研究了有机基质栽培条件下不同化肥施用量对番茄氮、磷和钾吸收利用规律的影响。结果表明: 适量施用化肥可提高番茄产量, 促进番茄对氮、磷、钾养分的吸收; 氮、磷、钾的吸收量均随施肥量的增加而增加; 基质中氮、钾的利用率均随施肥量的增加而降低, 而磷的利用率则随化肥施用量的增加而增加; 适量施用化肥还可明显促进基质迟效养分转化为速效养分。每形成1 000 kg 番茄果实, 植株需吸收氮 2.540 kg、磷 0.751 kg、钾 4.347 kg。确定了在有机基质栽培下番茄较佳化肥施用量计算方法为: 化肥施用量=(1.5 倍番茄目标产量需肥量－有机基质中速效养分量)/化肥中养分吸收率。     

Bioaccessibility and transport by Caco-2 cells of organoarsenical species present in seafood

Organoarsenical standards and raw and cooked seafood (DORM-2, sole, and Greenland halibut) were subjected to in vitro gastrointestinal digestion to estimate arsenic bioaccessibility (maximum soluble concentration in gastrointestinal medium). The in vitro digestion did not modify the chemical form of the organoarsenic species standards. In seafood, bioaccessibility was 67.5-100% for arsenobetaine (AB), 30% for dimethylarsinic acid (DMA), 45% for tetramethylarsonium ion (TETRA), and >50% for trimethylarsine oxide (TMAO). Cooking induced no changes in bioaccessible contents. In addition, transport by Caco-2 cells, an intestinal epithelia model, was evaluated from organoarsenical standards and DORM-2. For standards, transport ranged from 1.7% for AB to 15.5% for TETRA. In DORM-2, transport was observed for only AB (12%), with far higher efficiency than in the case of the standard solution, thus illustrating the interest of using whole foods for studying bioavailability.     

Effect of organic amendment on amount and chemical characteristics of humic acids in upland field soils

To assess the effect of continuous organic material (OM) application on soil humic acids, the amount and chemical characteristics of humic acids in various types of soils (n = 10) were compared between plots treated with farmyard manure (FYM) or rice straw compost (RSC) plus chemical fertilizer (CF) and plots treated with CF alone. The degree of humification (degree of darkening), molecular size distribution and ¹³C cross polarization/magic angle spinning nuclear magnetic resonance spectra of humic acids from CF‐treated soils showed wide variation among the soils. Humic acid content was generally larger in OM + CF soils than in corresponding CF soils, and the stable C isotopic ratio suggested partial replacement of indigenous humic acids with OM‐derived ones even where no apparent increase in humic acid content was observed. The rate of OM application and the indigenous humic acid content were related positively and negatively, respectively, to the apparent accumulation rate of humic acids among soils. The degree of humification of humic acids was generally smaller in OM + CF soils than in CF soils. Humic acids extracted from FYM and RSC exhibited chemical characteristics typical of humic acids having a smaller degree of humification, which suggested the contribution of OM‐derived humic acids to the differences between OM + CF and CF soil humic acids, such as larger average molecular sizes and smaller and larger proportions of aromatic C and O‐alkyl C, respectively, relative to total C in the OM + CF soil humic acids. Little change was observed in the chemical characteristics of humic acids when the degree of humification of indigenous humic acids was small. The effect of OM application on the chemical characteristics of humic acids was most conspicuous in soils containing humic acids having an intermediate degree of humification, possibly resulting from the combination of accelerated degradation of indigenous humic acids and the accumulation of OM‐derived humic acids.