酶标法测定原料乳中硫氰酸根含量

目的 建立酶标法测定原料乳中硫氰酸根含量的分析方法。方法 用三氯乙酸溶液沉淀原料乳中蛋白质和脂肪, 定量滤纸过滤后取上清液, 硫氰酸根与硝酸铁溶液显色后, 用酶标仪在450 nm波长处测吸光度值, 用原料乳做标准曲线, 定量测定原料乳中硫氰酸根的含量。结果 硫氰酸根浓度在0~16 mg/kg线性关系良好, 相关系数r=0.9991, 方法回收率在95.75%~102.83%之间, RSD≤3.25%, 检出限为0.54 mg/L。结论 本研究的检测方法数据可信度高, 操作简便, 一次性上机读取吸光度值, 节约检测时间, 测定成本相对较低, 适用于批量性检测生乳中硫氰酸根的定量分析。     

感悟好白酒蕴含的曼妙画卷

从白酒产区、酿酒原料、发酵容器、酿造工艺等角度解析了它们对白酒品质的影响,并揭示了好白酒内在品质应该具备的科学特性,进而彰显了“好白酒犹如一副曼妙画卷”的文化之美。     

Mechanistic implications of the solvent kinetic isotope effect in the hydrolysis of NaBH4

The sodium borohydride, NaBH₄, hydrolysis mechanism is studied via the H₂O/D₂O kinetic isotope effect (KIE). This reaction is of importance as NaBH₄ is considered as a hydrogen storage material. Nowadays, hydrogen is thought to be one of the most promising and efficient clean energy carriers. In order to control the rate of the hydrogen evolution reaction (HER), one has to understand the mechanism of its production. The H₂O/D₂O KIE of the reactions of NaBH₄ and NaBD₄ with water was studied in solutions containing a ratio of H₂O/D₂O = 1.00. The separation factor, α, of both reactions is α = 5.0 ± 1.0. The rate of the hydrolysis of BD₄^? in H₂O is faster than that of BH₄^?. The results point out that the rate-determining step in all hydrolysis stages is the H–OH bond scission.     

深圳"十七英哩"

对深圳万科十七英哩项目的设计进行详述,以探索海岸山地住宅的重点问题和解决方案.     

Survey of undeclared egg allergen levels in the most frequently recalled food types (including products bearing precautionary labelling)

Since the number of recalls involving undeclared allergens is commonly associated with bakery and snack foods, we aimed to determine the frequency of egg allergens in a large number of these products using two commercial enzyme-linked immunosorbent assay (ELISA) methods. Samples were chosen that either had no egg identified on the product label or which had an egg precautionary statement. Among all samples, egg protein was detected in 5% of products using a Morinaga (MO) kit and 1% of products using a R-Biopharm (RB) kit. For bakery samples, egg protein was detected in 6% of 363 samples with no precautionary labelling (6% by MO and 1% by RB kit) and 12% of 80 samples which had precautionary labelling. For snack samples, egg protein was detected in 2% of 371 samples with no precautionary labelling (2% by MO and < 1% by RB kit) and 5% of 21 samples which had precautionary labelling. The disagreement rates between two methods were 5.2% for bakery products and 2.6% for snack products. The sample repeatability was at an acceptable level for bakery (< 12.5%) and snack foods (< 7.5%) for each method. The relative standard deviation between test kits was high (103.1%) for bakery foods. Four bakery products without precautionary labelling had a higher level of egg protein per serving compared with the eliciting dose (ED₁₀ of 3.7 mg protein) for egg allergic patients. These results highlight the fact that detection methodology plays a vital role for accurate labelling control and mitigation of risk for egg allergic consumers.     

日本食物过敏原的管理及对我国的启示

随着我国食物过敏问题对消费者和食品企业的影响越来越严重,食物过敏原的管理和控制问题亟待解决。日本是世界上第一个建立强制性食物过敏标识并加以立法保护的国家,现已形成完善的食物过敏原标签管理系统。日本食物过敏原法规的形成过程、约束范围及食物过敏原标签的标注方式、不规范标注的处罚措施和过敏原成分的检测方法,对中国制定符合本国国情的食物过敏原强制性管理法规和建立相关的检测技术具有启示作用。     

Graceful Degradation FEC Layer for Multimedia Broadcast/Multicast Service in LTE Mobile Systems

This paper proposes an additional forward error correction (FEC) layer to compensate for the defectiveness inherent in the conventional FEC layer in the Long Term Evolution specifications. The proposed additional layer is called a graceful degradation (GD)‐FEC layer and maintains desirable service quality even under burst data loss conditions of a few seconds. This paper also proposes a non‐delayed decoding (NDD)‐GD‐FEC layer that is inherent in the decoding process. Computer simulations and device‐based tests show a better loss recovery performance with a negligible increase in CPU utilization and occupied memory size.     

Simultaneous utilization of ammonia,free amino acids and peptides during fermentative growth of Saccharomyces cerevisiae

The efficiency of nitrogen use by yeast is one of the key determinants of the successful completion of alcoholic fermentations. In this work the growth of Saccharomyces cerevisiae S288c in a synthetic medium containing ammonia and free amino acids, supplemented with yeast hydrolysate, was studied. Experiments with ¹⁵NH₄Cl and ¹⁵N‐labelled yeast hydrolysate were carried out to gain insight into which of these three classes of assimilable nitrogen sources yeast cells prefer. Co‐consumption of all three sources was observed; approximately 40% of the total nitrogen in the yeast protein fraction originated from yeast hydrolysate, while free amino acids and ammonia contributed 40 and 20%, respectively. The results indicate that several amino acids are more readily obtained from peptides, most likely when the uptake of their free forms is competitively inhibited and/or repressed. During the second half of each fermentation, a decrease in the incorporation of yeast hydrolysate‐derived nitrogen was observed. These results highlight the nutritional role of peptides in various yeast fermentations. Copyright © 2016 The Institute of Brewing & Distilling     

Warning signal words: connoted strength and understandability by children,elders, and non-native English speakers

Signal words, such as DANGER, WARNING and CAUTION, are commonly used in sign and product label warnings for the purpose of conveying different levels of hazard. Previous research has focused on whether people's perceptions of connoted hazard are consistent with the levels suggested by design standards and guidelines. Most investigations have used college students to evaluate the terms; other populations who may be at greater risk have not been adequately studied. One purpose of the present research was to determine whether young children, the elderly, and non-native English speakers perceive similar connoted hazard levels from the terms as undergraduates and published guidelines. A second purpose was to assess the terms' comprehensibility using various metrics such as missing values (i.e. ratings left blank) and understandability ratings. A third purpose was to develop a list of potential signal words that probably would be understandable to members of special populations. In the first experiment, 298 fourth- to eighth-grade students and 70 undergraduates rated 43 potential signal words on how careful they would be after seeing each term. The undergraduates also rated the terms on strength and understandability. In the second experiment, 98 elders and 135 non-native English speakers rated the same set of terms. The rank ordering of the words was found to be consistent across the participant groups. In general, the younger students gave higher carefulness ratings than the undergraduates. The words that the younger children and the non-native English speakers frequently left blank were given lower understandibility ratings. Finally, a short list of terms was derived that 95% or 99% of the youngest students (fourth- and fifth-graders) and 80% of the non-native English speakers understood. Implications of hazard communication are discussed.