TG-SPME-GC-MS研究谷氨酸和葡萄糖的固相美拉德反应

为了进一步研究无溶剂条件下的美拉德反应,自行设计热重-固相微萃取-气相色谱-质谱(TG-SPME-GC-MS)联用系统,建立谷氨酸-葡萄糖固相美拉德模式体系。采用划分温度段取样的方法,比较葡萄糖纯品和谷氨酸-葡萄糖体系自热解起始温度起在200℃范围内的热解行为差异,并对谷氨酸和葡萄糖在进行美拉德反应过程中各阶段热解产物的逸出规律进行研究。结果表明：固相美拉德模式体系中,即使在谷氨酸和葡萄糖质量比为1:10的情况下,美拉德体系的热解起始温度均比葡萄糖纯品提前55℃;反应初期(130～170℃)主要表现为葡萄糖热解产物的逸出;美拉德体系(谷氨酸-葡萄糖质量比1:4)的含氮热解产物自170℃开始生成,包括2-吡咯烷酮、L-焦谷氨酸甲酯、乙酰胺吡咯烷酮、5-甲基吡咯-2-甲醛。     

反应型可可香料的氨基酸和还原糖的Plackett-Burman设计筛选

本研究采用Plackett-Burman试验设计,选取缬氨酸、甘氨酸、苯丙氨酸、亮氨酸、酪氨酸、苏氨酸、丝氨酸、谷氨酸、精氨酸、葡萄糖、果糖11个可能的可可风味相关因子进行筛选。统计分析结果表明:苯丙氨酸、丝氨酸、亮氨酸、谷氨酸、精氨酸、甘氨酸对美拉德反应的可可风味产物中的几种重要的致香成分具有最显著的影响。未发现葡萄糖和果糖对可可风味有任何差异贡献。选择这5种氨基酸和两种还原糖制备反应型可可香料,产物进行感官分析,并用GC-MS分析其中的致香成分和含量,鉴定出52种成分。     

谷氨酸美拉德反应在金华火腿挥发性风味物质形成中的作用

为了研究谷氨酸参与美拉德反应在金华火腿挥发性风味物质形成中的作用,模拟金华火腿成熟环境,建立了金华火腿成熟条件下谷氨酸与葡萄糖和乙醛的反应,采用固相微萃取技术(SPME)气相色谱-串联质谱(GC-MS)分析方法研究了挥发性反应产物的组成。结果表明:谷氨酸与葡萄糖、乙醛美拉德反应产物中分别有9种和25种挥发性产物属于金华火腿中常见的风味物质,表明谷氨酸参与的美拉德反应,尤其与乙醛参与的美拉德反应产生的挥发性物质对金华火腿独特风味的形成具有重要贡献。     

对-香豆酸和绿原酸对美拉德反应体系中5-羟甲基糠醛形成的影响

以谷氨酸、赖氨酸、甘氨酸、半胱氨酸分别与葡萄糖反应构建美拉德反应体系,研究5-羟甲基糠醛(5-HMF)的形成量随时间的变化规律及对-香豆酸和绿原酸对5-HMF形成量的影响。结果表明:在相同反应时间内,模拟体系中5-HMF形成量由高到低排列依次是:谷氨酸-葡萄糖模拟体系>赖氨酸-葡萄糖模拟体系>甘氨酸-葡萄糖模拟体系>半胱氨酸-葡萄糖模拟体系;对-香豆酸、绿原酸对美拉德反应中5-HMF形成均表现出抑制和促进的"双重作用";不同质量浓度的对-香豆酸、绿原酸对5-HMF的影响趋势不同,相同质量浓度的同种酚酸对不同模拟反应体系中5-HMF的影响也有差异。     

模式体系谷氨酸-葡萄糖美拉德反应程度研究

为研究反应温度和反应时间对模式体系美拉德反应程度的影响,配制D-葡萄糖(0.02 mol/L)与L-谷氨酸(0.06 mol/L)浓度比为1∶3的美拉德反应液,分别置于10～40℃反应不同时间(10,20,30,40,50,60 d),通过测定不同条件下美拉德反应产物(MRPs)的pH值、吸光度值(A_(294nm)和A_(360nm))、挥发性成分、葡萄糖残余含量等,探讨模式体系的反应进程。结果表明,谷氨酸与葡萄糖发生美拉德反应的介质环境基本稳定,吸光度与反应温度、时间整体呈正相关,葡萄糖浓度随温度、时间变化遵循Boltzmann模型,符合动力学方程y=A_2+(A_1-A_2)/(1+exp(x-x_0)/d_x),且拟合效果较佳(R~2均大于0.90)。     

基于烟草水提物的Maillard反应产物影响因素

为充分利用烟叶资源,提高其使用价值,以亚临界萃取后的烟叶残渣为原料制备了烟草水提物,利用GC-MS法对Maillard反应产物进行定量分析,系统探讨了氨基酸种类及用量、反应时间对Maillard反应产物化学组成及卷烟感官质量的影响;并探讨了Maillard反应产物中的18种成分与卷烟感官指标的相关关系。结果表明:①谷氨酸和天冬氨酸的Maillard反应产物与水提物自身的Maillard反应相似,以5-羟甲基糠醛为主,其次为羟基丙酮、2-乙酰基吡咯;脯氨酸参与的反应产物则以羟基丙酮、糠醇和5-羟甲基糠醛为主。②以感官作用为依据,基于烟草水提物Maillard反应的最佳条件为还原糖（以葡萄糖计）与谷氨酸的摩尔比n_还原糖:n_谷氨酸=1:0.5、反应温度110 ℃、反应时间2 h。③18种成分中,2-甲基四氢呋喃-3-酮与烟气浓度相关关系密切,糠醛、5-甲基糠醛、2-呋喃基羟基甲基酮和5-羟甲基糠醛与透发性关系密切,羟基丙酮和3-甲基-1, 2-环戊二酮与烘焙香关系密切。      

葡萄糖-谷氨酸二肽模型体系中5-羟甲基糠醛形成的动力学分析

为了研究糖-肽模型体系中5-羟甲基糠醛形成的动力学规律,以葡萄糖-谷氨酸二肽为研究对象,对糖-肽体系中反应物(葡萄糖、谷氨酸二肽)消耗及反应产物(5-羟甲基糠醛)形成的动力学进行分析。结果显示:在加热温度90～110 ℃,加热时间0～6 h过程中,一级动力学对样品中反应物葡萄糖和谷氨酸二肽的消耗拟合效果较好,且消耗速率均随温度的升高而增大。在试验温度90～95 ℃(0～6 h)条件下,零级动力学对葡萄糖-谷氨酸二肽样品中5-羟甲基糠醛的拟合效果良好;100～110 ℃(0～6 h)条件下,一级动力学对其拟合效果较好。     

牛骨酶解物制备特色调味料的研究

本实验研究了以牛骨酶解液为反应基液,添加氨基酸、还原糖,经美拉德反应制备生成牛骨香汁,并进一步添加香辛料制备生成香骨酱的工艺条件,利用感官评定及美拉德反应产物进行分析,结果表明:在酶解液中添加0.2%的半胱氨酸与2%的木糖,在120℃下美拉德反应4 0 min形成香骨汁效果最佳,并将其浓缩4倍后风味更佳。在浓缩香骨汁中添加2%的食盐,4%的淀粉,各0.1%的干辣椒、白胡椒、黑胡椒、干生姜、花椒,各0.05%八角、孜然、咖喱粉,形成香骨酱风味最佳。     

氨基酸对葡萄糖-天冬酰胺模拟体系中丙烯酰胺形成的抑制作用研究

研究4种氨基酸对已建立的葡萄糖-天冬酰胺模拟体系中丙烯酰胺生成的影响。方法 以葡萄糖-天冬酰胺组为对照组, 在此基础上分别加入半胱氨酸、甘氨酸、赖氨酸和谷氨酸4种氨基酸为实验组, 于140 ℃反应5~30 min, 测定反应后模拟体系的褐变程度、色差值、生成丙烯酰胺含量和剩余葡萄糖含量。 结果 4种氨基酸中, 半胱氨酸和谷氨酸对模拟体系中的褐变度和色差值的抑制作用较好; 半胱氨酸和赖氨酸对底物葡萄糖的消耗作用较快; 半胱氨酸对丙烯酰胺的抑制效果最好, 抑制率为(76.00±0.73)%, 其他氨基酸的抑制率分别为甘氨酸(38.39±0.44)%、赖氨酸(51.03±3.09)%和谷氨酸(28.76±2.43)%; 进一步研究发现, 当添加4.2 mmol半胱氨酸时, 丙烯酰胺抑制率达(95.32±0.47)%。结论 4种氨基酸相比, 半胱氨酸对丙烯酰胺形成的抑制效果最好, 且对于降低葡萄糖-天冬酰胺模拟体系的褐变度、色差值、葡萄糖含量有较好的效果。     

不同氨基酸和糖对美拉德反应产物的影响

利用半胱氨酸、甘氨酸、谷氨酸3 种氨基酸和木糖、葡萄糖2 种还原糖作为反应底物,模拟美拉德反应制备香精,并对其香气成分和有害物质进行综合分析。结果表明：参与反应的氨基酸种类越多,所测得的挥发性物质种数也越多,反应产物的风味越丰富;甘氨酸参与的美拉德反应中丙烯酰胺的生成量较少,而谷氨酸的参与反应中丙烯酰胺的生成量较多;还原糖种类对丙烯酰胺的产生影响不大;谷氨酸参与的美拉德反应产物中,5-羟甲基糠醛（5-hydroxymethylfurfural,5-HMF）含量高,而半胱氨酸和甘氨酸参与的反应产物中,5-HMF的含量较低;木糖可减少产物中的5-HMF的含量。利用本实验条件制备香精,产物中的丙烯酰胺和5-HMF含量在安全范围内。     

Review of techniques to manufacture micro-hydrogel particles for the food industry and their applications

Microgels are ‘soft’ microscopic cross-linked polymeric particles that are being increasingly exploited in a variety of industries for rheology control, encapsulation and targeted delivery. They are valued because of the ability to tune their functionality to address specific applications in oil recovery, coatings, drug delivery, cosmetics, personal care and foods. Food microgels are typically biopolymer hydrogels in the form of microspheres, nanospheres (also called nanogels), spheroids and fibres. The utilisation of engineered microgels in foods has so far been limited, despite their great potential to address several needs in the food industry, including: satiety control, encapsulation of phytonutrients and prebiotics, texture control for healthier food formulations (e.g. reduced fat products), and targeting delivery to specific areas in the digestive tract. We review the scientific and patent literature on the utilisation and manufacturing methods for producing microgels with an emphasis on micro-hydrogels for food applications.     

12—A CRITIQUE OF SOME HYPOTHESES RELATING TO THE HETEROGENEITY OF THE HIGH-SULPHUR PROTEINS OF WOOL

Joubert and Burns prepared a large number of fractions from the high-sulphur proteins of wool and estimated their molecular weights and amino-acid compositions. Their data have been re-examined in order to look for statistically significant interrelations between amino acids and between the proportion of various amino acids and molecular weight. Statistical analysis of the data is also used to examine the credibility of some hypotheses concerning the mechanism of keratin biosynthesis and to provide further evidence for the existence of families of proteins within the high-sulphur fractions of wool.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of     

The Latest Data about Development of Chinese Printing Industry in 2013

In the 2014 China（Shanghai）International Printing Week,Director Wang Yanbin released the latest data about development of Chinese printing industry in 2013.According to statistics,in 2013,the total output value of Chinese printing industry exceeded 1trillion Yuan for the first time,reaching 1.03985 trillion Yuan.There were 105,000 printing enterprises in China,employees were 3.415 million.The total asset was 1.06247 trillion Yuan;     

The State Council Issued "Directory of Government Approved Investment Projects(2013 Edition)"

正On December 2nd,2013,the State Council issued the notification of"Directory of Government Approved Investment Projects(2013 Edition)"(hereafter referred to as"notification").It is pointed out in the"notification"that in order to further deepen reforms in investment systems and administrative examination and approval systems,simplify administrative procedures and delegate powers to lower levels,earnestly     

China textile machinery: taking off in progress

正Among the 1600 exhibitors who take apart in the ITMA ASIA+CITME2014 2/3 are Chinese manufactures.If the numerous figures failed to attract your attention,the increase of quality should draw your focus.To adopt the demand of developing textile machine market,domestic textile machinery enterprises now follow the slogan of"technology drives development"to enhance product competitiveness.Our domestic sellers will showcase product ranging from spinning,weaving,dyeing and printing,     

Top Ten News of China's Paper Industry 2013

On December 24th, 2013, the meeting on the selection of top 10 news of China＇s paper industry 2013 sponsored by 〈China Paper Newsletters〉 was held in Beijing. The yearly selection of the top l0 news, which began in 2000, has become a brand activity widely recognized in the industry thanks to the support from the authorities at all levels and public participation.     

National Development and Reform Commission Issued Announcement for Selection of Major Preliminary Research Projects for the "13~(th) Five-Year Plan"

In Apri Commi major p Plan＂ （h 2014, the National Development and Reform ssion issued an announcement for selection of reliminary research projects for the ＂13th Five-Year ereafter referred to as ＂The Announcement＂）     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the latest scientific     

Contamination of animal feed and food from animal origin with mineral oil hydrocarbons

Oils and fats used for the production of animal feed can become contaminated with mineral oil material originating from gas oils (C₁₈-C₃₅) or synthetic oils (poly alpha olefins, C₂₅ to beyond C₄₅). An important cause is assumed to be the discharge of waste oils, such as motor oil and hydraulic oils. Mineral oil material was analysed by on-line LC-GC-FID directly in the fat or in a raw extract from animal feed or foodstuffs. In Switzerland in summer/autumn 1999 concentrations in oils and fats for feed production were often found to be between 100 and 1000mg/kg. In the feeds, the average concentration was around 100mg/kg with values ranging up to a maximum of 1000mg/kg; few samples were free of contamination. In animal body fat, the average concentration determined in summer 1999 was 25mg/kg, with a maximum of 150mg/kg, although in samples from December 1999, contamination was substantially lower. In the fat phase of eggs, the average concentration was 30mg/kg, with a maximum of 80mg/kg. Paraffin oil is used for feed production, which may account for part of the contamination problem (e.g. eggs).