采用HS-SPME-GC-MS分析棕榈油热处理过程中挥发性成分变化

采用顶空固相微萃取与气相色谱质谱联用技术(HS-SPME-GC-MS)对棕榈油(24℃)热处理过程(180℃)中挥发性成分变化进行分析。结果表明:热处理前后的棕榈油中共鉴定出63种挥发性化合物,包括醛类、醇类、酸类、酮类、烃类和杂环类;棕榈油中挥发性成分种类随加热时间的延长呈先增多后减少趋势;经热处理后,棕榈油中挥发性成分种类以醛类和烃类为主,且醛类物质含量最高,加热12 h后达80.413%;此外,1-辛烯-3-醇、己酸、2-十五烷酮和2-戊基呋喃的检出表明棕榈油中亚油酸发生了氧化分解,其变化趋势表明棕榈油随加热时间延长氧化劣变程度加深,油脂品质劣变加重。     

LCMS-IT-TOF测定不同脂肪酸结构食用油中的羰基化合物

为研究高温加热过程中食用油脂肪酸组成与羰基化合物形成的关系,先将三种食用油(油茶籽油、玉米油和亚麻籽油)在180 ℃高温加热24 h,然后采用气相色谱仪(GC)测定加热后油样中脂肪酸组成,采用高效液相色谱-离子阱-飞行时间质谱仪(LCMS-IT-TOF)测定油样生成羰基化合物组成。结果表明:油茶籽油(含有79.08%油酸)中特征羰基化合物为辛醛、壬烯醛、壬醛、癸烯醛、十一烯醛;玉米油中(含有55.05%亚油酸)特征羰基化合物为戊醛、戊酮、己醛、庚烯醛、癸二烯醛;亚麻籽油中(含有56.57%亚麻酸)特征羰基化合物为丙醛、丙酮、丁醛、丁酮、庚二烯醛。该结果表明脂肪酸组成对油脂加热所产生的羰基化合物种类起决定性作用,油酸氧化主要在8、9、10、11号碳位产生氢过氧化物,亚油酸主要在9、12、13、14号碳位产生氢过氧化物,亚麻酸主要在12、15、16号碳位产生氢过氧化物。氢过氧化物继续裂解产生不同的羰基化合物。     

发酵小麦粉加热过程中挥发性成分分析

热加工是面食制品风味形成的主要过程。该文以发酵小麦粉为主要原料应用气质联用技术探究了其在热加工过程中挥发性物质的形成规律。结果表明,发酵小麦粉在加热过程中,共发现88种挥发性化合物,分别为醛类19种、醇类15种、酮类11种、含苯衍生物15种、呋喃类11种、酸酯类10种和杂环类化合物7种。当加热温度高于110℃时,挥发性物质的种类开始明显增加,温度达到120℃时,各挥发性物质的构成和含量变化最为显著。该文测定了各挥发性成分的形成温度,在60～100℃时,挥发性风味成分主要由C6～C10挥发性醛类和醇类组成。而在超过100℃,特别是在120℃时,形成了许多长碳链的醛类和醇类、呋喃类、酸类、酯类和含氮化合物。     

薏米贮藏过程中异味产生的机理

以薏米为原料,研究了薏米贮藏过程中脂肪含量、脂肪酸值、脂肪酸组成、常见氧化指标(过氧化值、茴香胺值、总氧化值、丙二醛含量)和醛类化合物的变化情况,并分析了薏米的异味变化与上述指标的关系。研究结果表明:随着薏米贮藏时间的延长,薏米的脂肪含量和不饱和脂肪酸相对含量均显著降低,脂肪酸值、饱和脂肪酸相对含量、过氧化值、茴香胺值、总氧化值、丙二醛含量均显著增加,醛类的"相对内标含量"也显著增加。薏米贮藏过程中其总氧化值、丙二醛含量和挥发性醛类化合物含量与薏米的异味程度间呈显著正相关(p0.01),不饱和脂肪酸含量与薏米异味程度间呈显著的负相关(p0.01)。说明薏米贮藏过程中异味主要是由于薏米油脂氧化产生的,薏米油脂的二级氧化产物醛类化合物为薏米贮藏过程中产生异味的主要原因。     

油脂氧化产生的氧化ɑ,β不饱和醛的研究进展

氧化α,β不饱和醛是油脂氧化过程中产生的一类有毒有害物质,广泛分布于油脂加热挥发物及各类油脂热加工食品中,也能内源性地在人体内产生,对人体健康造成重大威胁。本研究综述氧化α,β不饱和醛的结构、性质、生成途径、检测方法等内容,为提升公众对这类有毒化合物的认识,减少对人体的危害提供参考。     

基于油脂氧化的食品加工伴生危害物形成研究进展

热加工过程对食品的风味、色泽以及危害物的形成具有重要影响。美拉德反应和油脂氧化是热加工中发生的最重要的两类反应,彼此独立且相互影响,尤其是油脂氧化产生的羰基化合物能与氨基化合物发生反应,从而对丙烯酰胺、杂环胺、晚期糖基化末端产物、5-羟甲基糠醛等多种危害物的形成具有重要作用。本文以油脂氧化产生的活性羰基化合物为关注点,综述了油脂氧化对食品加工伴生危害物的影响,以期为抑制食品中危害物的生成提供理论参考。     

不同加热处理对牦牛肉风味组成和质构特性的影响

取西藏种萨牦牛肉,研究不同热处理方式(微波加热、高压炖煮和常温水煮)对牛肉风味和质构特性的影响。结果表明：这3种热处理得到的牦牛肉产品风味化合物主要包括脂肪烃、脂环烃、脂肪醛、脂肪酮、芳香烃、含硫化合物和脂肪醇6大类,其中醛类化合物(己醛、壬醛和辛醛等)为熟牦牛肉的特征风味。微波加热形成的风味种类最高,达137种,高压炖煮次之(133种),常温水煮最差(128种),微波加热形成的醛类化合物达10种,高压炖煮形成的醛类化合物为5种,而常温水煮形成醛类化合物为4种。对微波加热、高压炖煮和常温水煮3种加热方式形成的牛肉进行质地剖面分析,表明微波加热形成的牛肉硬度低、弹性高等最佳质感效果。综合风味指标、质构指标和感官评价指标,确认微波加热牦牛肉品质最优。     

烹饪解疑

为什么黄酒是一种重要的调味品?绍兴黄酒,又称料酒,主要成分是乙醇、糖、氨基酸、有机酸、醛、脂类等挥发性物质。调味时之所以要用料酒,是由于它具有特殊香气,并能溶解生物咸苦味物质、无机盐、油脂等,在加热过程中还能发生许多化学反应。1．呈色、提香作用。料酒中含有糖、醛类、氨基酸,烹调时,糖发生焦化反应,醛类与氨基酸发生美拉德反应,产生有色物质,同时又分解出多种挥发性的香味物质。     

玉米油加热过程中挥发性物质形成机制

利用真空辅助顶空固相微萃取-气相色谱-质谱联用技术对玉米油在加热过程中挥发性物质组成进行分析,以揭示玉米油加热过程中风味形成机制,此过程中检测并鉴定了52种挥发性化合物,其中包括醛(21种)、酮(8种)、醇(9种)、呋喃(3种)、酸和酯(共8种)和芳香族的化合物(3种)。同时,确定了各组分的形成温度。结果表明,温度对挥发性化合物的形成和含量有较大的影响,在30~100℃的低温范围内,玉米油的风味成分主要由C6~C10挥发性醛类和醇类组成;温度超过100℃,特别是在150℃时,形成了许多长碳链的醛类和醇类、呋喃类、酸类、酯类,从120℃到150℃,大多数挥发性化合物的含量在加热过程中都较大幅度增加。     

6种食品专用油脂的风味特征研究

旨在为食品专用油脂的风味提升提供参考,采用顶空固相微萃取-气相色谱-质谱联用(HS-SPME-GC-MS)技术和感官评定分析黄油、椰子油、全氢化棕榈仁油、全氢化棕榈仁油硬脂、部分氢化大豆油和全氢化大豆油6种代表性食品专用油脂的挥发性成分和感官特征,并结合相对气味活度值(ROAV)及其聚类分析确定关键风味化合物。结果显示：椰子油的挥发性成分最为丰富,共鉴定出13个关键风味化合物,主要为内酯类、醛类化合物,椰子香和奶油香风味浓郁;黄油共鉴定出8个关键风味化合物,主要为内酯类、酮类和醛类化合物,具有果香、奶油香和青香;部分氢化大豆油共鉴定出6个关键风味化合物,主要为醛类和酮类化合物,主要呈果香、蜜蜡香、脂肪气味和奶油香;全氢化棕榈仁油、全氢化大豆油和全氢化棕榈仁油硬脂检出的关键风味化合物种类较少,分别为5个、2个和4个,主要为醛类和甲酯类/酸类化合物,主要呈果香风味和脂肪气味;感官评价结果和关键风味化合物分析结果存在一定联系。综上,6种食品专用油脂中,黄油、椰子油和部分氢化大豆油风味化合物较为丰富,具有突出的感官特征。     

茶叶中挥发性成分对映异构体研究进展

茶叶香气是多种挥发性化合物以不同的浓度存在的混合体,是评价茶叶品质的重要因素之一。茶叶中多数 挥发性化合物都具有一个或多个立体中心,存在香气特征与香气阈值迥异的对映异构体,其不同组成比例引发的致 香效果对茶叶香气的形成有着重要的影响。本文围绕近些年国内外关于茶树等植物或食品的挥发性成分对映异构体 的研究,比较分析不同挥发性成分对映异构体的香型特性,阐述了手性挥发性成分的研究现状及分析方法,并对未 来研究及发展趋势等进行展望,以期从对映异构体的角度更深层次了解茶叶香气品质的化学实质。     

Aroma values — a useful concept?

Rapidly increasing knowledge about the high complexity of food aromas requires selection or ranking procedures as to the importance of the particular components for flavour impression. For this purpose the concept of aroma values has been discussed which calculates quantitative data in connection with aroma effectiveness of the compounds. The simplification of the concept with respect to the practical application, however, can change the natural system and lead to erroneous conclusions. There are not only interactions between aroma substances of sensoric-physiological character which may not be ignored. Physical conditions like lipid content, distribution of aroma compounds between aqueous and lipid phase or the sorption of volatile substances to the polymer nutrients in foodstuffs are of influence, too.     

Metabolism of vicine and convicine in rat tissues: absorption and excretion patterns and sites of hydrolysis

The objectives of this study were to determine whether dietary vicine and convicine were absorbed by rat tissue, and to determine their excretion patterns and/or sites of degradation. Orally administered vicine and convicine were excreted in relatively low amounts via the kidney and faeces. However, no vicine or convicine was detected in the blood, liver, kidney or muscle tissue of rats which had been fed these compounds. In-vitro studies demonstrated that vicine and convicine were not hydrolysed in liver, kidney, muscle, caecal wall or intestinal wall homogenates. In contrast, digesta samples from the large intestine and caeca were able to rapidly hydrolyse these compounds, with the concomitant formation of new compounds. Digesta from the stomach and small intestine promoted the slow hydrolysis of these compounds, as did fresh faecal samples. These results would suggest that vicine and convicine are absorbed by the rat in only limited amounts, are not hydrolysed by rat tissues, and are rapidly cleared from tissue via the kidney. The bulk of the dietary vicine and convicine are hydrolysed in the large intestine and caecum.     

Digestion and bioavailability of bioactive phytochemicals

There are many scientific reports on determination of the content and biological activity of compounds found in food. However, these analyses are not sufficient to determine their effect on the human body. During digestion of food ingredients, many changes can modify their structure and this may affect their absorption and bioactivity. Many phenolic aglycones are hydrophilic and can be absorbed through biological membranes by diffusion. However, most polyphenols occur in the glycosidic form, which undoubtedly affects their absorption in the intestine. Oligopeptides are also absorbable via secondary active transport but based on the hydrogen ion gradient or with transporter PepT1. The bioavailability of phytochemicals is determined by their molecular weight or chemical structure and the food matrix. Accordingly, the aim of this work was to present the novel scientific reports related to the influence the many factors on digestibility, bioaccessibility and activity of selected bioactive compounds of plant origin.     

食品作用于肠黏膜免疫系统可能的信号途径

树突状细胞是体内最强的抗原呈递细胞,也是介导机体先天免疫和获得性免疫的桥梁。当食品中的不同生理活性成分作用于肠黏膜免疫系统时,会被肠黏膜中的树突状细胞吞噬加工呈递,也可以直接结合到DC细胞表面的模式识别受体上,如TLRs、CLRs以及NLRs等,然后启动相应的信号传递途径,从而调节肠黏膜免疫系统中细胞因子网络的变化。本文主要目的是在现有的研究结果的基础上,尽量详尽地判断和揭示食品中的生理活性成分如何与DC相互作用,激发DC可能的信号传导途径,而后如何影响肠黏膜系统中细胞因子的变化。理解这一因果关系,对食品如何发挥其生物功能具有十分重要的指导意义。     

Interactions of phenolic and volatile compounds with yeast lees,commercial yeast derivatives and non toasted chips in model solutions and young red wines

Ageing of wines on lees, the use of commercial yeast derivative products and the addition of oak chips to wine permit the release of different compounds such as mannoproteins and polysaccharides into wines during yeast autolysis. These compounds released can interact with phenolic compounds and/or aromatic compounds, also modifying wine sensory perception. For that reason, the aim of this work was to evaluate the interaction of phenolic and volatile compounds of wines with yeast lees, non-toasted oak wood chips and different commercial yeast derivative preparations in model wine solutions and in a real red wine. The results found in this study have shown that most of the phenolic and volatile compounds studied are adsorbed by wood and bound by lees in model wine solutions. However, in the model wines in general, the commercial yeast derivative products studied only interacted with the volatile compounds but not with the phenolic compounds. The adsorption of the phenolic compounds occurred in the first 15 days of treatment, remaining constant for 2 months; however, in the case of volatile compounds, these compounds initially displayed a retention effect, but after 30–60 days, the release of the previously bound compounds was instigated. The adsorption effect on the phenolic and volatile compounds in the model wine solution was not always the same as in the red wine studied, which highlights the important presence of other wine compounds in these interactions.     

SYSTEM OF WORT ANALYSIS. IV: THE ESTIMATION OF THE TRUE PROTEIN NITROGEN OF WORTS AND BEERS

A method is given in which wort or beer is heated with sufficient sodium nitrite and acetic acid to deaminate the nitrogen compounds present. On cooling a precipitate forms which, the experiments suggest, represents the true protein* present, since it appears to correspond to the albumin and globulin of barley extracts and to include the nitrogen compounds of wort which are coagulable by boiling. It is possible that the amount of this fraction bears a relation to non-biological haze, while a subsequent paper suggests an important effect on fermentation. The results indicate that boiling conditions play an important part in controlling the amount, as also may the amount of tannin in hops and fermentation conditions.     

Study of the photochemical behaviour of sunscreens – benzylidene camphor and derivatives

Benzylidene camphor derivatives have been currently used as ultraviolet filters in sunscreen compositions. When solutions of these compounds are exposed to the light from a solar simulator, a photoinduced cis-trans isomerization is observed. The initial quantum yields of this photochemical isomerization of studied molecules have been determined in several solvents. Their photochemical behaviour depends neither on the concentration nor on the presence or absence of oxygen or other inhibitors such as isopropanol or biacetyl. It means that the lifetime of the precursor states of isomerization is about 10⁻¹²s, that is to say, too short for them to react with neighbouring molecules.
For each compound, the ratio     of the respective concentrations of 'E' and 'Z' forms was also determined by photostationary state. A good agreement between theoretical and experimental values of this ratio shows that the studied compounds are only very slightly photodegradable. This was confirmed by the low values of photodegradation quantum yields.
In case of the studied compounds, the isomerization process observed is totally reversible. During irradiation a photostationary state is quickly reached, each isomer may change into the other form after absorption of a photon which leads to a mixture of isomers. In practice, it is this mixture of E and Z forms which acts as UV filters.
It may be said that a very short lifetime of the excited states, a good light stability and a reaction inertia under light irradiation make these compounds excellent sunscreen agents.
Comportement photochimique des antisolaires. Benzylidène camphre et certans de ses dérivés     

花椒中麻味物质的呈味机理及制备方法研究进展

不饱和烷基酰胺是花椒呈麻味的重要物质,从花椒中鉴定出的麻味物质主要成分有α-、β-、γ-、δ-山椒素 等及其衍生物。麻味物质通过激活瞬时受体电位（transient receptor potential,TRP）V1和TRPA1离子通道或抑制两 孔钾离子通道激发感觉神经元。麻味强度受麻味物质结构的影响,不同结构的麻味物质引起不同的受体激活,产生 不同程度的辛麻感。麻味物质的制备方法主要有两种：利用系列柱层析、制备色谱等进行纯化的常规方法和利用适 当化学反应进行制备的化学合成方法。本文对花椒中麻味物质的主要种类、麻味物质的呈味机理及麻味物质的制备 方法3 个方面的研究现状进行综述,为麻味物质进一步的系统化深入研究提供一定支持。