糖汁的氧化镁-亚硫酸法清净工艺及其机理

以赤砂糖回溶糖浆为研究对象,以氧化镁和亚硫酸为清净剂,探究氧化镁-亚硫酸法对糖汁清净新工艺,发现氧化镁-亚硫酸法对糖汁具有高效的清净效果。最佳工艺条件为:氧化镁用量(以镁计)400 mg/L,亚硫酸用量(以硫计)400 mg/L,反应pH 11.3,反应温度60℃,反应时间10 min。在此条件下,糖汁脱色率81.71%、除浊率85.65%,絮凝物体积35 mL。通过zeta电位、絮凝物形成过程的动态图像对氧化镁-亚硫酸法清净机理进行探讨。     

响应面优化饮料中咖啡因的前处理方法

以咖啡因的回收率为评价指标,在单因素试验基础上,通过Box-Behnken设计-响应面法考察超声时间、超声温度和氧化镁用量对咖啡因回收率的影响。结果表明,超声温度38℃,超声时间18 min,氧化镁用量0.2 g时,咖啡因回收率96.91%。Box-Behnken设计-响应面法优化饮料中咖啡因前处理方法,使前处理方法合理,方法简便,精确度高,可预测性好。     

纳米氧化镁制备方法与进展

介绍了用机械粉碎法、流动液面真空蒸发法、固相反应法、直接沉淀法、均匀沉淀法和醇盐水解法、水热法、气相氧化法、溶胶-凝胶法、微乳液/反向胶束法等方法制备纳米氧化镁原理,并对个别方法进行简要评价。针对目前纳米氧化镁研究中存在的问题,提出未来研究方向。     

药用氧化镁的研制

根据医药及食品行业对氧化镁的要求,提出用卤水—氨水法生产药用氧化镁,对卤水中影响产品质量的杂质离子用简单方法除去,所得氧化镁各项指标均达国标。     

水热合成法制备高纯度氧化镁

用水热合成法制备了高纯度氧化镁，实验发现，这种方法是一种分离镁和钙的非常有效的方法，与气相氧化法、液相滴下法、Ｓulman法、Ａman法相比，本方法简单、产品质量稳定，氧化镁含量可达９９．９５％－９９．９８％，。适应于工业化生产。     

氧化钙、氧化镁协同氧化铝留硅蒸煮工艺研究

针对麦草浆黑液中SiO2引起的＂硅干扰＂问题,对氧化钙、氧化镁协同氧化铝留硅的烧碱-蒽醌法制浆工艺进行了研究。结果表明：当氧化铝∶氧化镁∶氧化钙为0.5∶0.5∶2时留硅作用最明显,成本最低。相应工艺条件为：用碱量14%,蒽醌0.05%,氧化铝用量0.5%,氧化镁用量0.5%,氧化钙用量2%,液比1∶5,温度160℃,保温30min。在此工艺条件下,纸浆的灰分含量增加了2.54%,SiO2含量增加了1.39%。     

氧化镁铵盐法制备高纯过氧化镁

在氯化铵溶液体系中,以氧化镁,过氧化氢为原料,制备高纯过氧化镁。研究表明采用氧化镁活性大于100,氯化铵/氧化镁不小于10%,过氧化氢∶氧化镁不小于4∶1,反应温度大于40℃情况下,反应时间不小于30 min,可制备出纯度大于90%的过氧化镁。     

外电场对氧化镁分子(X1∑+)结构及性质的影响

对氧化镁分子基态进行几何优化,使用B3P86法结合6-311++g基组进行理论计算,得到氧化镁分子在外电场(-0.015~0.015 AU)作用下的基态电子结构,并讨论外电场对氧化镁分子键长、能量、能级分布、频率及偶极矩的影响。结果表明,外电场对MgO分子结构及其性质影响较为明显,可为氧化镁在医药、饲料和食品等领域的进一步应用提供参考。     

冷冻干燥法制备纳米氧化镁条件的研究

较详细地介绍了以卤水和工业氨水为原料,以冷冻干燥法制备纳米氧化镁的方法,对其影响条件作了研究,并对产品作了表征。结果表明,冷冻干燥法能有效地改善凝胶干燥过程中粒子间的团聚性能,制备出的纳米氧化镁粒子的平均粒径为20nm,粒子分布均匀,分散性好。     

氧化镁法与石灰石-石膏法脱硫技术方案比较

文章简要介绍了几种湿法脱硫的方法,对石灰石-石膏法、氧化镁法脱硫工艺进行详细介绍和比较。通过文章的比较,希望为相关工作提供参考。     

Dietary magnesium oxide interactions with sodium bicarbonate on cows in early lactation

Thirty-six Holstein cows were fed a diet of 50% concentrate and 50% corn silage (dry matter) for 12 wk postpartum. Treatments were 0, .4, and .8% magnesium oxide with or without .8% sodium bicarbonate in a 2 X 3 factorial arrangement. Dry matter intake was not different among treatments although the combined buffers had higher intake. Milk production was higher for the .4% magnesium oxide treatments either alone or with sodium bicarbonate as compared with either the 0 or .8% magnesium oxide treatments. Ruminal pH was increased with addition of sodium bicarbonate either alone or together with magnesium oxide. Dietary addition of .4% magnesium oxide either alone or with sodium bicarbonate increased total volatile fatty acid in ruminal fluid. Propionate and valerate were depressed in both of the combined buffered diets. Fecal pH was increased with magnesium oxide addition either alone or with sodium bicarbonate. Increasing magnesium oxide increased magnesium in plasma. No interactions in animal performance were significant for the two buffers.     

Assay and use of magnesium ferrite as a reference in absorption trials with cattle.

Magnesium ferrite, an inert ferrimagnetic material, was introduced as reference substances in absorption trials with ruminants. A method for assaying magnesium ferrite was based upon the difference between the weight of the test material on an analytic balance and that of the same material weighed below a permanent magnet. Four heifers in two pairs were in a feeding experiment lasting for 6 wk divided into two 3-wk periods. Each animal received once daily 12 g magnesium ferrite and, as control, 12 g shredded paper impregnated with 4.2 g chromium oxide. The rations were composed of chopped wheat straw and concentrates, given twice daily, with a different straw-concentrate ratio for each group. The treatments were reversed after the first experimental period. Mean recoveries of magnesium ferrite and chromic oxide in total collection of feces were 103 and 90.2%. Mean absorption coefficients of organic matter calculated by total collection and by the ratios of magnesium ferrite and chromic oxide in feces taken from the rectum were 68.1, 70.1, and 65.7%. The method is simple and accurate and may replace methods involving time consuming chemical determinations.     

Poured feed blocks using distillery by-products as supplements for ruminants

A technique was developed in this study for preparing solid poured feed blocks as supplements for ruminants. Blocks containing liquid condensed solubles and dried distillers grain with solubles as the base material and protein source were prepared with different cementing agents. A method for testing the hardness of blocks, an index of the physical durability, was also developed. The hardness of blocks was positively related to the concentration of magnesium oxide and to the length of storage time. Ferrous sulphate, on the other hand, had a synergistic effect with magnesium oxide which accelerated the setting of blocks after 24 h. A feeding trial revealed a negative relationship between daily intake by cattle and hardness of blocks. Blocks prepared with about 4% magnesium oxide and 3% ferrous sulphate provide a dry, weather-resistant supplement with a degree of hardness that allows an optimum rate of intake.     

Dietary sodium bicarbonate and magnesium oxide for early postpartum lactating dairy cows: effects on production, acid-base metabolism, and digestion

In two experiments with cows in early lactation fed 40% corn silage and 60% concentrate diets (dry basis), we examined effects of 1.0% dietary sodium bicarbonate and .8% magnesium oxide in a 2 x 2 factorial arrangement on performance, acid-base metabolism, and digestion. In Experiment 1 with 20 Holstein and 4 Jersey cows, intake and milk production were not affected by treatment through 12 wk postpartum. In digestion trials at 3, 6, 9, and 12 wk postpartum, addition of magnesium oxide increased digestibility of dry matter 1.8% units by sodium bicarbonate whereas acid detergent fiber digestion increased 9 to 12% units with addition of either buffer. In Experiment 2, with four fistulated Holstein cows in a Latin square design, intake per unit body weight was increased .18% units by dietary sodium bicarbonate while milk production was unaffected. Dry matter and acid detergent fiber digestion were increased slightly by sodium bicarbonate plus magnesium oxide addition whereas nitrogen balance increased 23 g/day in cows fed magnesium oxide alone. Because of the low fiber content of the ration, milk fat percent increased .5 to .9% by addition of either buffer in both experiments and resulted in corresponding increased in fat-corrected milk. Sodium bicarbonate and magnesium oxide prevented rapid declines in rumen pH associated with feeding in Experiment 2, which related to changes in acid detergent fiber digestion. Blood acid-base metabolites were relatively unchanged by treatment in either experiment. Urinary bicarbonate and net acid excretion rates were changed on the average by +41 and +43 meq/h by sodium bicarbonate or magnesium oxide but could not be related to changes in intake and production.     

Neutralization of acid in the rumen by magnesium oxide and magnesium carbonate

Two reagent and two feed grade magnesium oxides and reagent grade magnesium carbonate, sodium bicarbonate, and calcium carbonate were evaluated to ascertain their ability to neutralize acid in the rumen. Rumen fluid pH was increased in vitro, compared to the control, by antacid compounds, and their increased ranked: calcium carbonate less than feed grade magnesium oxide A less than light magnesium oxide and feed grade magnesium oxide B less than heavy magnesium oxide less than magnesium carbonate less than sodium bicarbonate. Titrations at constant pH's ranging from 3.0 to 7.5 indicated that these magnesium compounds were reactive at pH's normally in the rumen although reactivity decreased with increasing pH. Intraruminal doses of feed grade magnesium oxide A and calcium carbonate did not change rumen fluid pH for other compounds ranked: feed grade magnesium oxide B less than magnesium carbonate less than heavy magnesium oxide. Feeding of heavy magnesium oxide or magnesium carbonate increased rumen fluid pH as compared to the control diet. Feeding feed grade magnesium oxide B in three quantities to cattle resulted in proportional increased in fecal pH and fluidity of feces. Two feed grade magnesium oxides differed in their ability to neutralize acid in the rumen.     

半微量定氮法中三氯乙酸提取挥发性盐基氮的改进

目的 提高三氯乙酸提取挥发性盐基氮效率。方法 研究了提取剂三氯乙酸和水的提取效果、结果稳定性,并考察了三氯乙酸做提取剂时氧化镁的添加量和判别指示剂,同时添加氯化铵做回收率实验。结果 按照标准方法用三氯乙酸浸泡的样品检测结果明显偏低,通过研究发现其样品溶液碱度未能达到方法要求,经优化后的方法加标回收率为94.0%～95.9%,相对标准偏差（RSD）为 0.57%;用水做提取剂的样品结果偏高,浸泡30min过程中,pH值中性环境样品持续腐败。结论 经优化后三氯乙酸提取法样品可以直接蒸馏无需过滤,从而简化检验流程;三氯乙酸给样品提供足够的酸性环境,抑制样品进一步腐败;通过方法学考察,优化后的检验方法满足实验要求。     

Extension of Postharvest Life of Oyster Mushroom by Modified Atmosphere Packaging Technique

ABSTRACT: Mushrooms were packaged in polypropylene, low-density polyethylene, linear low-density polyethylene (LLDPE) packages after washing with 0.5% calcium chloride and 0.5% citric acid (CA), and based on off-color and off-odor development, suitable packaging material and washing solution were selected. Effectiveness of magnesium oxide in modifying the in-package gaseous atmosphere and thereby extending the postharvest life was tested by monitoring the physicochemical properties. Oxygen concentration was 5.5% and 9.9% and carbon dioxide concentration was 8.1% and 4.5%, in the control and packages containing 3 g of magnesium oxide, respectively, on day 12 in storage. Packaging mushroom in 0.015 mm LLDPE packages with 3g of magnesium oxide after washing with 0.5% calcium chloride and 0.5% CA was successful in extending the postharvest life at 8°C and 70% RH from 6 d in commercial samples to 12 d.     

原子荧光光谱法测定虾粉中总砷的分析方法

利用原子荧光光谱法测定虾粉中的总砷,比较了硝酸+高氯酸,硝酸+硫酸湿法消解及氧化镁和硝酸镁存在下的干法消解,发现只有干法消解测定结果与标准物质吻合。采用干法消解对虾粉中砷的测定方法进行多次测定,得出本法的平均回收率为95.9%,相对标准偏差为0.75%~2.20%。实验证明本法的精密度、准确度、灵敏度均能满足分析要求。