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1.
Abstract

A two‐seasonal study was conducted to determine the trace mineral status of goats' grazing forages and soils in southern Punjab, Pakistan. Soil and forage samples were collected fortnightly for two seasons. Sampling period effects were found in soil copper, zinc, and selenium, and all forage minerals except selenium were affected by sampling times. Seasonal effects were observed in iron, manganese, and selenium for soils and in copper, iron, zinc, manganese, and selenium for forages. All soil mineral levels except cobalt and selenium were found to be above critical levels and likely to be adequate for normal growth of plants growing therein, whereas soil cobalt and selenium were severely deficient during both seasons. The levels of iron, zinc, cobalt, and selenium in soil were higher and copper and manganese were lower during winter than during summer. Forages contained marginal to deficient levels of cobalt during the winter, copper and selenium during the summer, and moderately deficient levels of iron and severely deficient levels of zinc, manganese, and cobalt during the summer. Forage copper, iron, zinc, manganese, and selenium during winter were found to be adequate for the requirements of ruminants. Consequently grazing animals at this location need continued mineral supplementation of these elements to prevent deficiency diseases and to support optimum animal productivity.  相似文献   

2.
Abstract

Municipal waste compost can improve the fertility status of tropical soils. The redistribution of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in tropical soils after amendment with solid municipal waste compost was investigated. Four tropical agricultural soils from Mali characterized by poor trace‐element status were amended with compost and incubated for 32 weeks at 35°C. The soil were analyzed at the beginning and the end of the incubation experiment for readily available fractions, organic fractions, and residual fractions as operationally defined by sequential extraction. Readily available Fe increased significantly with compost application in most soils. Readily available Mn was mostly unaffected by compost application. After 32 weeks, readily available Zn had increased, and readily available Cu had decreased. Readily available levels of the elements remained greater than deficiency levels in the compost‐amended soils. Organic fractions of the elements increased after compost addition. The organic fractions and residual forms, depending on the element and the soil, remained constant or increased within the duration of the experiment.  相似文献   

3.
为探明豫中植烟土壤p H和有机质对微量元素有效态含量的影响，在豫中许昌市的建安、禹州、襄城和漯河市的城区、临颍和舞阳6个植烟县(区)采集了191个典型烟田耕层(0～20 cm)土样，测定了微量元素(有效铜、铁、锰、锌、钼)含量、p H和有机质含量，采用Pearson相关分析法与曲线回归方法分析了有效态微量元素含量与pH、有机质之间的关系。结果表明，有效铜、铁、锰、锌和钼的平均含量分别为1.20、49.24、84.80、1.71和0.02mg/kg，有效锰总体上充足，有效钼整体极为缺乏，个别样点有效铜、铁和锌缺乏；p H平均为7.90，总体上偏高；有机质平均为17.78g/kg，总体上适宜；微量元素有效态与pH、有机质之间均存在二次函数关系，随p H升高，有效铜呈增加趋势，有效铁和锌呈先升后降趋势，有效锰和钼呈先降后升趋势；随有机质升高，有效铜、锰、锌和钼呈增加趋势，有效铁呈先升后降的趋势。  相似文献   

4.
Proteolysis of milk proteins can be attributed to both native proteases and the proteases produced by psychrotrophic bacteria during storage of fresh raw milk. These proteases cause beneficial or detrimental changes, depending on the specific milk product. Plasmin, the major native protease in milk, is important for cheese ripening. Milk storage and cheese-making conditions can affect the level of plasmin in the casein and whey fractions of milk. A microbial protease from a psychrotrophic microorganism can indirectly increase plasmin levels in the casein curd. This relationship between the plasmin system and microbial proteases in milk provides a means to control levels of plasmin to benefit the quality of dairy products. This paper is a short review of both the plasmin system and microbial proteases, focusing on their characteristics and relationship and how the quality of dairy products is affected by their proteolysis of milk proteins.  相似文献   

5.
Lacey  E. M.  King  J. W.  Quinn  J. G.  Mecray  E. L.  Appleby  P. G.  Hunt  A. S. 《Water, air, and soil pollution》2001,126(1-2):97-120
Surface samples and cores were collected in 1993 fromthe Burlington Harbor region of Lake Champlain. Sediment samples were analyzed for trace metals(cadmium, copper, lead, nickel, silver and zinc),simultaneously extracted metal/acid volatile sulfide(SEM-AVS), grain size, nutrients (carbon and nitrogen)and organic contaminants (polycyclic aromatichydrocarbons (PAHs) and polychlorinated biphenyls(PCBs)). The concentrations of cadmium, copper,silver and zinc from the partial sediment digestion ofthe surface samples correlated well with each other(r 2>0.60) indicating that either a commonprocess, or group of processes determined the sedimentconcentrations of these metals. In an analysis of thespatial distribution of the trace metals and PAHs,high surficial concentrations were present in thesouthern portion of the Harbor. The trace metal trendwas strengthened when the concentrations werenormalized by grain size. A sewage treatment plantoutfall discharge was present in the southeasternportion of the Harbor at the time of this study and isthe major source of trace metal and PAH contamination. Evaluation of sediment cores provides a proxy recordof historical trace metal and organic inputs. Thepeak accumulation rate for copper, cadmium, lead, andzinc was in the late 1960s and the peak silveraccumulation rate was later. The greatestaccumulation of trace metals occurred in the late1960s after discharges from the STP began. Subsequentdeclines in trace metal concentrations may beattributed to increased water and air regulations. The potential toxicity of trace metals and organiccontaminants was predicted by comparing contaminantconcentrations to benchmark concentrations andpotential trace metal bioavailability was predictedwith SEM-AVS results. Surface sample results indicate lead,silver, ΣPAHs and ΣPCBs are potentially toxicand/or bioavailable. These predictions were supportedby studies of biota in the Burlington Harborwatershed. There is a clear trend of decreasing PAHand trace metal contaminant concentrations withdistance from the STP outfall.  相似文献   

6.
为探明白银市平川区土壤硒分布规律和影响土壤中硒含量的因素,为保护和开发富硒土壤资源提供理论依据。我们在白银市平川区共采集土壤样本59个、农作物可食部分样品36个,通过检测分析土样全硒含量、土壤化学性状(铅、汞、镉、pH、有机质、有效硅、有效硼、有效铜、有效锌、有效铁、有效锰)与农作物可食部分全硒含量,研究了白银市平川区土壤与农作物全硒含量特征及其影响因素。结果表明:平川区土壤全硒平均含量为0.29 mg/kg,高出甘肃省土壤全硒平均含量45.0%,且富硒土壤母质均为冲洪积物。土壤全硒含量与土壤有机质(R2=0.32*)、有效硅(R2=0.35**)呈显著或极显著正相关。平川区各农产品全硒含量大小依次为胡麻、枸杞、藜麦、菊芋、玉米、马铃薯。平川区土壤硒含量有区域差异,西北部高于东南部,且灌区高于旱作区。土壤母质、有机质含量、有效硅含量是决定土壤富硒的主要因子,富集系数是各农产品全硒平均含量产生较大差异的主要原因。  相似文献   

7.
Selenium is an essential element in the human diet. Interestingly, there has been an increased consumption of dietary supplements containing this element in the form of either inorganic or organic compounds. The effect of using selenium as a dietary supplement in yogurt has been evaluated. For this purpose, different concentrations of inorganic Se (ranging from 0.2 to 5000 microg g(-1)) have been added to milk before the fermentation process. Biotransformation of inorganic Se into organic species has been carefully evaluated by ion-exchange, reversed-phase, or size-exclusion chromatography, coupled to inductively coupled plasma mass spectrometry (ICP-MS). Yogurt fermentation in the presence of up to 2 microg g(-1) of Se(IV) produces a complete incorporation of this element into proteins as has been demonstrated applying a dialysis procedure. Analysis by SEC-ICP-MS showed that most of them have a molecular mass in the range of 30-70 kDa. Species determination after enzymatic hydrolysis has allowed the identification of Se-cystine using two different chromatographic systems. The biotransformation process that takes place during yogurt fermentation is very attractive because yogurt can act as a source of selenium supplementation.  相似文献   

8.
The effects of heat treatment and limited kappa-casein hydrolysis on the micelle/serum distribution of the heat-induced whey protein/kappa-casein aggregates were investigated as a possible explanation for the gelation properties of combined rennet and acid gels. Reconstituted skim milk was submitted to combinations of 0-67% hydrolysis of the kappa-casein at 5 degrees C and heat treatment at 90 degrees C for 10 min. The protein composition of the ultracentrifugal fractions was obtained by reverse-phase high-performance liquid chromatography (RP-HPLC). The aggregates contained in each phase were isolated by size-exclusion chromatography and analyzed by RP-HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Upon heating only, 20-30% of the total kappa-casein dissociated, while 20-30% of the total whey protein attached to the micelles. When heated milk was renneted, little changes were observed in the distribution and composition of the aggregates. Conversely, the heat treatment of partially renneted milk induced the formation of essentially micelle-bound aggregates. The results were discussed in terms of the preferred interaction between hydrophobic para-kappa-casein and denatured whey proteins.  相似文献   

9.
硒的土壤环境化学研究进展   总被引：26，自引：3，他引：26  
李永华  王五一 《土壤通报》2002,33(3):230-233
本文概述了土壤环境中硒的赋存形态和生物有效性 ,阐述了影响环境中硒的形态、有效性和转化的因素 .并对今后硒的土壤环境化学研究应关注的问题提出了建议  相似文献   

10.
Abstract

The distribution of zinc in some major Zimbabwean soils was studied using 120 profiles taken from 22 different locations. The total zinc status (TL‐Zn) of the horizons of soils studied was low (8 ppm), and the range was narrow (3.7 to 16.3 ppm). The residual zinc (RS‐Zn) fraction was about 65 percent of the total zinc found in the soils, while 15 percent was organically bound zinc (OG‐Zn), 14 percent was available zinc (MG‐Zn), and 6 percent was zinc associated with hydrous metal oxides (OX‐Zn). The total zinc status of the soils was related to parent material. Generally, texture had a significant effect on zinc distribution with heavier textured soils having more zinc in most fractions than the lighter textured soils. A decrease in zinc down the profile was observed for available, residual, and total zinc. If cropped intensively, 32 per cent of the soils with less than 1 ppm available zinc have the potential for zinc deficiency. Multiple stepwise regression analysis showed that organic matter, silt and clay contents, available copper, and resin P2O5 contents were important for predicting the available zinc content of the soils, while texture and organic matter content were important in predicting total zinc content.  相似文献   

11.
The trace metal content of municipal solid waste (MSW) compost affects the quality and potential end uses of the finished product. The impact of typical contaminants found in the organic fraction of MSW on the trace metal content of compost was investigated. Contaminants including alkaline batteries, galvanized nails, zinc-plated screws, copper wires, and electronic cables were exposed to a thermophilic composting process for three weeks. The increase in trace metal content in the compost product was measured at the end of the composting process. The results showed that low-quality alkaline batteries, galvanized nails, zinc-plated nails, and copper wires had a significant impact on the zinc, copper, arsenic, lead, and cobalt contents of compost. Copper wires showed the highest impact on copper content, which was 52% of the Canadian Council of Ministers of the Environment (CCME) Category A limit in the final compost. Galvanized nails contributed to final levels of zinc reaching 30% of the CCME Category A limit. To ensure that CCME Category A criteria can be achieved, it is recommended that contaminants made from bare copper or coated with zinc be removed from the composting feedstock.  相似文献   

12.
氮锌配施对石灰性土壤锌形态及肥效的影响   总被引：13，自引：1，他引：12  
通过分析石灰性土壤上施用锌肥后土壤中锌的形态变化,研究锌肥的有效性及后效,为指导合理施用锌肥提供理论依据。结果表明在潜在性缺锌的石灰性土壤施锌肥没有明显的增产效果,可增加小麦籽粒锌含量,但不同基因型反应差异很大;土壤中的锌主要以矿物态存在,占全锌91.5%~97.6%,其次为松结有机态锌(1.34%~5.53%)、碳酸盐结合态锌(0.47%~1.55%);施入土壤中的锌增加了交换态、松结有机态、碳酸盐结合态、氧化锰结合态锌含量,但大部分转化为矿物态;种植小麦可以使土壤中的锌向有效态转化;施氮增加了小麦对锌的吸收,也增加了锌矿化的比例;主成分分析结果表明,交换态、松结有机态和碳酸盐结合态均能不同程度反映土壤锌的有效性,石灰性土壤中碳酸盐结合态和有机结合态锌含量占有较为可观的比例,因此增加这两种形态储备容量是调节和控制土壤锌营养状况的重要措施。  相似文献   

13.
有机物中氮的简易测定   总被引：1，自引：0，他引：1  
官自元 《土壤学报》1964,12(1):91-93
在有机物中测定氮,应用得较多而普遍的是克氏法。但该法中的蒸镏是一项冗长的操作。为了避免蒸馏步骤,有些研究者提出了一些不用蒸馏的测定方法。其中最筒易的是先将消解液中和,再加入过量的碱液以分解铵盐,而后用酸回滴剩余的碱。但此法不甚严密,干扰离子较多,若操作不善,误差也较大[1]。目前应用得较多的是甲醛法。由于硒、汞、铜等离子对本法有干扰,故消解时不能加入这些接触剂以缩短消解时间。因而,此法虽避免了冗长的蒸馏操作,但却带来了消解的困难。  相似文献   

14.
Reconstituted skim milk was adjusted to pH values between 6.5 and 7.1 and heated (90 degrees C) for up to 30 min. The skim milk samples were then readjusted to pH 6.7. Acid gels prepared from heated milk had markedly higher G ' values, a reduced gelation time, and an increased gelation pH than those prepared from unheated milk. An increased pH at heating decreased the gelation time, increased the gelation pH, and increased the final G ' of acid set gels prepared from the heated milk samples. There were only small differences in the level of whey protein denaturation in the samples at different pH values, and these differences could not account for the differences in the G ' of the acid gels. The levels of denatured whey protein associated with the casein micelles decreased and the levels of soluble denatured whey proteins increased as the pH at heating was increased. The results indicated that the soluble denatured whey proteins had a greater effect on the final G ' of the acid gels than the denatured whey proteins associated with the casein micelles.  相似文献   

15.
Heat treatment of milk induces a reaction between the milk proteins and lactose, resulting in lactosylated protein species. The lactosylation of the two major whey proteins alpha-lactalbumin and beta-lactoglobulin was investigated by reversed phase liquid chromatography-mass spectrometry (LC-MS). Three sample series, consisting of aqueous model solutions of each whey protein separately and in mixture and whole milk, were heated for different time periods, and the progression of the lactosylation reaction was monitored. The observed degrees of lactosylation and the reaction kinetics showed that the lactosylation of beta-lactoglobulin was not influenced by the presence of other components, whereas the lactosylation of alpha-lactalbumin was enhanced in whole milk compared to the aqueous model systems. An in-depth evaluation of the LC-MS data yielded information regarding changes of physicochemical properties of the whey proteins upon lactosylation. Whereas retention time shifts indicated changes in hydrophobicity for both alpha-lactalbumin and beta-lactoglobulin, changes in the charge state distribution denoting conformational alterations were observed only for beta-lactoglobulin. The analysis of different liquid and solid milk products showed that the lactosylation patterns of the whey proteins can be used as indicators for the extent of heat treatment.  相似文献   

16.
Abstract

The analysis of extractable trace elements was carried out on 434 soils using 0.1 N HC1 as the extractant for copper, manganese, iron, zinc and cobalt, 0.2 M ammonium oxalate at pH 3.0 for molybdenum and boiling water for boron. Results indicated that on the average from about 1 to 20 percent of the total element content of the soil uas extractable, the percentage varying with the element. Comparing the amount of extractable elements in the 0–15 cm and 15–30 cm layers indicated that only manganese, zinc and boron were significantly different.

Correlation studies showed that the pH significantly influenced the quantity of manganese, iron, zinc and boron extracted, while organic matter influenced copper, manganese, zinc, cobalt and boron and clay content the copper, manganese, iron, zinc, cobalt and boron.  相似文献   

17.
Isoflavones are novel nutraceutical constituents of soybeans, but considerable amounts are lost in the whey during conventional tofu manufacturing. In this study, in a small-scale process, 2 mL of koji enzyme extract (soybean koji/deionized water, 1/3, w/v) was combined with 600 mL of soy milk, and 30 mL aliquots were incubated at 35 degrees C for 0, 30, 60, 120, and 300 min, for enzyme pretreatment. After each treatment time, soy milk was heated to 85 degrees C, CaSO4 was added to aggregate protein, and the mixture was centrifuged to separate the solids (tofu) from the whey. The tofu yield and moisture contents from soy milk treated for 30 or 60 min were higher than those from soy milk treated for 0 (control), 120, or 300 min. The protein content of freeze-dried tofu varied in a limited range, and native PAGE and SDS-PAGE patterns revealed slight quantitative and qualitative variations among products. Soy milk daidzein and genistein contents increased while daidzin and genistin contents decreased as the time of enzyme pretreatment of the soy milk increased. After 30 min of pretreatment, daidzin, genistin, daidzein, and genistein contents recovered in tofu products were higher than those of the control. In a pilot-scale process, aliquots (3 L) of soy milk were enzyme-treated for 30 min, aggregated with CaSO4, and hydraulically pressed to remove the whey. As in pretreatments, soy milk daidzein and genistein contents increased while daidzin and genistin contents decreased. In a comparison of the control and enzyme-treated tofu products, the total recoveries of daidzin, genistin, daidzein, and genistein in the tofu products increased from 54.9% to 64.2%. When the tofu products were subjected to a sensory panel test, both products were judged acceptable.  相似文献   

18.
Long-term irrigation with municipal wastewater may lead, even in spite of intense farming, to an accumulation of organic matter, nutrient elements, and trace metals in soils. Excessive increases of heavy metals may pose a potential risk to the food chain and provoke restrictions for the further cultivation of sensitive crops. Copper (Cu), zinc (Zn), and lead (Pb) forms in soils under long-term irrigation (for 100–120 years) with treated wastewater of Wroclaw were investigated by using selective seven-step sequential extraction (procedure of Zeien-Bruemmer) for partitioning the metals into operationally defined fractions, likely to be released in solution under various environmental conditions. The largest fraction of Cu, Pb, and particularly Zn in nonirrigated (control) soils was strongly bound in a residual form, while the percentage of exchangeable and the most labile fractions were negligible. Total concentration of metals in irrigated soils was elevated, and significant redistribution of metals among phases was observed. Percentages of residual fraction of Cu and Pb were no more than 25% (Zn < 40%), while significantly increased contribution of fractions occluded on iron (Fe) oxides and organically bound Cu. Exchangeable and readily mobile forms of Zn are predominant zinc fractions in soils irrigated with wastewater.  相似文献   

19.
Skim milk was adjusted to pH values between 6.5 and 6.7 and heated (80, 90, and 100 degrees C) for up to 60 min. Changes in casein micelle size, level of whey protein denaturation, and level of whey protein association with the micelles were monitored for each milk sample. Changes in casein micelle size were markedly affected by the pH at heating. At low pH (6.5-6.55), the casein micelle size increased markedly during the early stages of heating, and the size plateaued on prolonged heating. The maximum increase in size was approximately 30-35 nm. In contrast, at high pH (6.7), much smaller changes in size were observed on heating and the maximum increase in size was only approximately 10 nm. An intermediate behavior was observed at pH values between these two extremes. The rate of denaturation of the major whey proteins, alpha-lactalbumin and beta-lactoglobulin, was essentially unaffected by the pH at heating for the small pH changes involved in this study, and the changes in casein micelle size were poorly related to the level of whey protein denaturation. In contrast, the level of denatured whey proteins associating with the micelles was markedly dependent on the pH at heating, with high levels of association at pH 6.5-6.55 and low levels of association at pH 6.7. Changes in casein micelle size were related to the levels of denatured whey proteins that were associated with the casein micelles, although there was a small deviation from linearity at low levels of association (<15%). Further studies on reconstituted and fresh milk samples at smaller pH steps confirmed that the association of whey proteins with the casein micelles was markedly affected by the pH at heating. These results indicate that the changes in casein micelle size induced by the heat treatment of skim milk were a consequence of the whey proteins associating with the casein micelles and that the level of association was markedly influenced by small pH changes of the milk. It was not possible to determine whether the association itself influenced the casein micelle size or whether parallel reactions involving micellar aggregation caused the increase in micelle size as whey protein association progressed.  相似文献   

20.
The concentrations of trace and non-trace elements were determined in blood and fibers of alpacas (Vicugna pacos) from a north Italian area, as well as in their pasture forages. This is the first investigation regarding this species in Italy, and the first considering alpaca’s fiber as bioindicator worldwide. Metal contents in blood were in the decreasing order: copper?>?zinc?>?aluminum?>?selenium?>?lead?>?nickel?>?manganese?>?chromium?>?arsenic and cadmium, while in fiber, metal levels were in the following order: aluminum?>?zinc?>?copper?>?manganese?>?chromium?>?nickel?>?selenium?>?lead?>?arsenic and cadmium. Antimony, beryllium, mercury, tin, and thallium were below the limit of quantification (0.010 mg kg?1). The analysis of the alpacas’ forage confirmed the same trend found in fiber, suggesting that metal bioaccumulation was affected by diet. These preliminary results have shown that all the trace elements studied bioaccumulated to a greater extent in the fibers of the alpaca than in the blood. Accordingly, we may suggest that alpaca fibers could be used for monitoring exposure especially to non-essential metals like aluminum, cadmium, and lead, and could constitute a suitable non-invasive method for measuring trace and non-trace element exposure in camelids.  相似文献   

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