“厚味”γ-谷氨酰-缬氨酸增味作用差异性机制

γ-谷氨酰-缬氨酸（γ-Glu-Val）具有多变的呈味特性,在水溶液中呈现涩味,可以增强基本味觉物质的味感强度,赋予奶酪、鸡汤、酱油等食物厚味味感。目前对于γ-Glu-Val呈味特性的机理研究甚少,尤其是鲜见它对于味觉增强效果的差异性机制的研究。本实验利用感官实验和分子模拟对γ-Glu-Val增味作用的差异性机制进行研究。感官实验结果显示,γ-Glu-Val对于基本味感（鲜味、甜味、咸味和酸味）均有一定的提升作用,而对于鲜味的提升效果最为明显。分子模拟实验的结果表明,γ-Glu-Val对基本味感受体（T1R1、T1R2和T1R3）均有一定的亲和力,其中对于鲜味受体T1R1的亲和力最强、结合自由能最高,与此相反,γ-Glu-Val对甜味受体T1R2的亲和力最弱、结合自由能最低,暗示其增鲜作用强于增甜作用。分子动力学结果显示,在味精存在的前提下,γ-Glu-Val可通过氢键和疏水键与鲜味受体T1R1上的氨基酸残基（Phe-274、Ser-275、Ser-300、Trp-303、Ala-147、Ala-170）相互作用,激活鲜味受体,以实现其增鲜作用。本实验解析了γ-Glu-Val增味作用差异性分子机制,为进一步验证其呈味机理提供理论支撑;同时为小分子物质的增味作用研究提供了思路。     

Sweet and bitter constituents of Wilbrandia species

Two novel cucurbitane glycosides, wilbrandisides A and B were isolated as sweet-taste substances from the root of Wilbrandia species (Cucurbitaceae) along with seven known cucurbitane glycosides. Their structures were determined by spectroscopic means, including two-dimensional NMR experiments. Their sweet-taste properties were evaluated by a human sensory panel test. Consequently, wilbrandiside A was shown to be 28 times sweeter than sucrose and was the compound having the most potent sweet taste of all the cucurbitane glycosides isolated from this plant.     

Sweet Taste in Man: A Review

ABSTRACT:  A greater understanding of the molecular mechanisms of sweet taste has profound significance for the food industry as well as for consumers. Understanding the mechanism by which sweet taste is elicited by saccharides, peptides, and proteins will assist science and industry in their search for sweet substances with fewer negative health effects. The original AH-B theories have been supplanted by detailed structural models. Recent identification of the human sweet receptor as a dimeric G-protein coupled receptor comprising T1R2 and T1R3 subunits has greatly increased the understanding of the mechanisms involved in sweet molecule binding and sweet taste transduction. This review discusses early theories of the sweet receptor, recent research of sweetener chemoreception of nonprotein and protein ligands, homology modeling, the transduction pathway, the possibility of the sweet receptor functioning allosterically, as well as the implications of allelic variation.     

新甲基橙皮苷二氢查耳酮及合成前体药理作用研究进展

新甲基橙皮苷二氢查耳酮（Neohesperidin dihydrochalcone,NHDC）是一种无毒、高甜度、低热量的甜味剂,具有增甜、增香、掩盖苦味、修饰风味的功能与抗氧化、抗炎、降血脂等药理活性,在食品及医药领域具有一定的开发潜力。当前NHDC的合成前体主要包括橙皮苷（Hesperidin,HSD）、新橙皮苷（Neohesperidin,NHP）和柚皮苷（Naringin,NRG）,具有抗氧化、保护肝肾、抑菌和改善胃肠道等多种生物学活性。NHDC的药理研究相对具有发展进程缓慢、研究系统欠缺、机制深度缺乏等特点。本文以NHDC及其合成前体为关键词在SciFinder、Web of Science、CNKI等科学数据库中进行检索,综述了NHDC的药理作用和机制,并对其合成前体的药理研究进展进行总结,以期为NHDC的进一步综合利用和开发高附加值产品提供参考。     

Correlation between in vitro binding activity of sweeteners to cloned human sweet taste receptor and sensory evaluation

Food Science and Biotechnology - The human sweet taste receptor is a TAS1R2/TAS1R3 heterodimer. To investigate the correlation between the in vitro affinity of sweeteners with stably expressed...     

Determination of neohesperidin dihydrochalcone in foods

An HPLC method was developed for the determination of neohesperidin dihydrochalcone (NHDC) in foods. A solid sample was extracted with methanol. The extract was evaporated and the residue was dissolved in methanol-water (2:8) mixture. In the case of fluid sample, the sample solution was prepared by dilution with methanol-water (2:8) mixture. The sample solution was cleaned up on a C18 cartridge. The cartridge was washed with water and methanol-water (3:7) mixture, and NHDC was eluted with methanol-water (7:3) mixture. NHDC in the eluate was separated on an ODS column and determined with a UV detector (282 nm). The identity of NHDC in foods was confirmed by means of HPLC with a photodiode-array detector. The recoveries of NHDC added to various kinds of foods were 75.2-134%. The determination limit of NHDC was 1 microgram/g.     

Residue mutations in the sweetness loops for the sweet-tasting protein brazzein

To identify critical residues, important for sweetness, of the sweet protein brazzein, 11 mutants of the residues in three loops of brazzein were constructed by site-directed mutagenesis. We found that mutations of Glu41 to Ala, Lys, or Arg at position 41 in loop 40–43 made the molecules significantly sweeter than brazzein, while mutations at two distant residues (changing Arg43 to Lys or Glu) decreased sweetness. A similar pattern occurred at loop 30–33, where mutation of the His31 to Arg significantly increased sweetness, while mutations at positions 30 or 33 in the immediate vicinity of this region significantly decreased sweetness. In addition, a Gln17 residue in the loop 9–19 was necessary for structural integrity. From these results, we suggest that the loops containing His31 and Glu41 are critical regions of the molecule for eliciting sweetness, and the charge and/or structure of the side chain of these residues play an important role in the multi-point interactions between brazzein and the sweet-taste receptor.     

Physicochemical and psychophysical characteristics of binary mixtures of bulk and intense sweeteners

Correlating psychophysical characteristics with physicochemical properties of sweeteners is of relevance to the understanding of the origin of sweetener synergy, an essential parameter for the food manufacturer. Psychophysical evaluation was carried out on bulk sweeteners (sucrose and maltitol) and intense sweeteners (aspartame, sodium cyclamate, acesulfam-K, alitame) in mixtures. The concentrations of mixtures were calculated to be equisweet to 10% sucrose and sweetness intensity was evaluated by reference to sucrose solutions using a “sip and spit” method. While a positive synergistic phenomenon is observed for sugar/sodium cyclamate and maltitol/acesulfamK mixtures, a significant suppression effect is obtained when aspartame is added to sugars. Additivity is observed for sucrose/alitame and sucrose/acesulfamK mixtures. The origin of these differences lies in the influence of the two molecules on water structure and in the nature of their hydration. From physicochemical properties (intrinsic viscosity, Huggins coefficient, apparent specific volume, hydration number, surface tension and contact angle), alitame and aspartame seem characterised by hydrophobic hydration; sodium cyclamate, as well as the bulk sweeteners, appear more compatible with water structure and possess hydrophilic hydration. ACK is differentiated from other sweeteners by a negative hydration. Synergy occurs when components with identical types of hydration are mixed. This phenomenon is accompanied by an increase in the mobility of water molecules in the proximity of bulk sweeteners (maltitol and sucrose) and a reduction of volume of the hydrated solute molecule. Inversely, suppression and additivity occur when constituents of the mixture possess different natures of hydration, as in sucrose/aspartame mixtures, and when physicochemical properties show a reduction of the mobility of water around the sweeteners. For suppression effects, an increase in volume of the hydration sphere is also observed. Interpretation of the sweetness of mixtures of sugars and artificial sweeteners, in terms of their compatibility with water structure, is of relevance at an economic level in food formulations.     

Towards an improved understanding of sweetener synergy

Sweetener synergy is of vital practical importance to the food manufacturer but its mechanistic explanation is impossible given the current limited understanding of sweet taste chemoreception. All current psychophysical models of response to sweet stimuli are probably incomplete, but some fit the experimental data better than others and can thus be used to predict the taste of sweetener mixtures. Some sweetener mixtures have been unequivocally reported as synergistic but such observations do not in themselves constitute evidence for the existence of multiple sweet taste receptors, and the interpretation of synergy demands analysis at the molecular level.     

液相色谱串联质谱法同时测定白酒中4种甜味剂方法研究

用液相色谱串联质谱法同时测定白酒中甜蜜素、阿斯巴甜、糖精钠、安赛蜜4种人工合成甜味剂,排除了液相色谱、气相色谱等仪器测定时存在的假阳性的可能.样品只需简单前处理即可直接导入测定.采用多反应监测模式进行测定,4种人工合成甜味剂的回收率在86%～106%之间,定量检出限为5μg/L～12.5μg/L,在获得较高灵敏度的同时,大大缩短了样品检测周期,具有广阔的应用前景.     

不同抑制剂对苦瓜粉味觉的修饰效果

以苦瓜粉浸泡液为对象,分别添加乳酸锌、新甲基橙皮苷二氢查尔酮、γ-氨基丁酸、酪朊酸钠、全脂乳粉、阿魏酸、聚葡萄糖、三氯蔗糖、新地奥明、单磷酸腺苷,采用感官评定结合标签量值评估（general labeled magnitude scale,gLMS）法评价不同抑制剂对苦瓜粉浸泡液苦味、后苦味、甜味、后甜味、涩味以及特征风味的影响;通过模糊评判筛选抑制效果最佳的3?种抑制剂进行正交试验,评价复合抑制剂对苦瓜粉浸泡液苦味及后苦味的影响。结果表明,10?种抑制剂对苦瓜粉浸泡液的苦味、后苦味、涩味均有显著抑制作用。其中新甲基橙皮苷二氢查尔酮对苦味、后苦味抑制作用最强;乳酸锌对后苦味、γ-氨基丁酸对苦味也有较好的抑制作用;酪朊酸钠对涩味的抑制作用最为明显;三氯蔗糖、聚葡萄糖、酪朊酸钠、全脂乳粉会增加整个体系的甜味及后甜味。以乳酸锌、新甲基橙皮苷二氢查耳酮、γ-氨基丁酸3?种抑制剂进行正交试验,结果表明1?g苦瓜粉添加0.60?mg新甲基橙皮苷二氢查耳酮、3.98?mg?γ-氨基丁酸、4.46?mg乳酸锌时,苦瓜粉浸泡液苦味和后苦味可以从明显降低到基本察觉不到,且苦瓜特征风味保留较好,无其他异味存在。     

Sweet taste receptor expression in ruminant intestine and its activation by artificial sweeteners to regulate glucose absorption

Absorption of glucose from the lumen of the intestine into enterocytes is accomplished by sodium-glucose co-transporter 1 (SGLT1). In the majority of mammalian species, expression (this includes activity) of SGLT1 is upregulated in response to increased dietary monosaccharides. This regulatory pathway is initiated by sensing of luminal sugar by the gut-expressed sweet taste receptor. The objectives of our studies were to determine (1) if the ruminant intestine expresses the sweet taste receptor, which consists of two subunits [taste 1 receptor 2 (T1R2) and 3 (T1R3)], and other key signaling molecules required for SGLT1 upregulation in nonruminant intestines, and (2) whether T1R2-T1R3 sensing of artificial sweeteners induces release of glucagon-like peptide-2 (GLP-2) and enhances SGLT1 expression. We found that the small intestine of sheep and cattle express T1R2, T1R3, G-protein gustducin, and GLP-2 in enteroendocrine L-cells. Maintaining 110-d-old ruminating calves for 60 d on a diet containing a starter concentrate and the artificial sweetener Sucram (consisting of saccharin and neohesperidin dihydrochalcone; Pancosma SA, Geneva, Switzerland) enhances (1) Na⁺-dependent d-glucose uptake by over 3-fold, (2) villus height and crypt depth by 1.4- and 1.2-fold, and (3) maltase- and alkaline phosphatase-specific activity by 1.5-fold compared to calves maintained on the same diet without Sucram. No statistically significant differences were observed for rates of intestinal glucose uptake, villus height, crypt depth, or enzyme activities between 50-d-old milk-fed calves and calves maintained on the same diet containing Sucram. When adult cows were kept on a diet containing 80:20 ryegrass hay-to-concentrate supplemented with Sucram, more than a 7-fold increase in SGLT1 protein abundance was noted. Collectively, the data indicate that inclusion of this artificial sweetener enhances SGLT1 expression and mucosal growth in ruminant animals. Exposure of ruminant sheep intestinal segments to saccharin or neohesperidin dihydrochalcone evokes secretion of GLP-2, the gut hormone known to enhance intestinal glucose absorption and mucosal growth. Artificial sweeteners, such as Sucram, at small concentrations are potent activators of T1R2-T1R3 (600-fold > glucose). This, combined with oral bioavailability of T1R2-T1R3 and the understanding that artificial sweetener-induced receptor activation evokes GLP-2 release (thus leading to increased SGLT1 expression and mucosal growth), make this receptor a suitable target for dietary manipulation.     

毛细管柱气相色谱法测定乳制品中的甜蜜素

采用Rtx-1非极性毛细管柱对乳制品中的甜蜜素的检测方法进行了探讨,改进了样品处理方法,建立了应用Carrez试剂沉淀蛋白,毛细管柱分离检测乳制品中甜蜜素的方法.经方法验证,方法检出限为5.16μg,定量下限为15.48μf,在0.0～1.0μg浓度范围内线性关系良好,相关系数R2为0.9999,回收率在94.2%～1...     

钯碳对合成新橙皮苷二氢查尔酮的影响

在碱性条件下,以新橙皮苷为原料、钯碳(Pd/C)为催化剂合成新橙皮苷二氢查尔酮(NHDC),研究新橙皮苷与催化剂的投放比例、催化剂的循环次对产率的影响。结果表明,新橙皮苷与催化剂比例为4∶1时,该条件下NHDC的产率最大,产率接近99%;循环次数与产率成反比,循环1~5次时,产率始终在80%以上,循环次数为1时产率最高。     

味觉受体研究热点分析

味觉是重要的感知反应，基本的味觉包括甜、酸、苦、咸、鲜5 种。味觉受体是用于感知各种味觉的蛋白质。本文对味觉受体热点关键词、来源、研究手段、受体类型、研究人员等进行分析概述，为开展味觉受体相关研究提供参考。通过文献分析发现，苦味、甜味、酸味、鲜味、大鼠、人类、小鼠、细胞、表达、蛋白质、诱导、基因、信号、神经元和分子等是味觉受体研究的热点关键词，Proceedings of the National Academy of Sciences、Journal of Neuroscience、American Journal of Physiology-Regulatory, Integrative and Comparative Physiology和Journal of Comparative Neurology是味觉受体研究领域的重点期刊。鼠类味觉受体是大多数实验的研究对象，然而鼠类和人类的味觉受体之间仍然存在较大差异，为更准确地探索人类味觉受体，还需对人类本身的味觉受体进行深入的研究。目前对味觉受体的研究已经进入结构生物学和神经生物学水平，主要采用分子生物学实验和计算机模拟技术等手段对受体结构进行探索。研究人员已经解析了青鳉鱼T1R2/T1R3配体识别结构域、斑马鱼Otop1和鸡Otop3的结构以及各味觉受体的信号传导通路，但大多数受体的精确结构还未解析出，也难以区分不同特点的味觉神经刺激。采用蛋白质表达纯化、蛋白质结构解析和信号传导等技术获得G蛋白偶联受体（G protein coupled receptors，GPCRs）的单晶体并解析晶体结构以及阐明各受体间的相互作用机理是目前重点的研究方向。美国目前在味觉受体研究领域处于领先地位，Ryba N. J. P.、Hoon M. A.和Chandrashekar J.等科学家目前引领了该领域的研究方向。本文明确了味觉受体领域发展现状，预测了味觉受体领域发展趋势，可为科研人员提供研究方向和思路。     

液相色谱-串联质谱法测定白酒中甜蜜素的不确定度评价

目的研究液相色谱-串联质谱法测定白酒中甜蜜素的不确定度评定。方法以白酒为例,对GB5009.97-2016中液相色谱-串联质谱法测定甜蜜素的不确定度进行评定。结果白酒中甜蜜素的含量为0.331 mg/kg时,测定结果的合成标准不确定度为0.0242 mg/kg,取k=2,扩展不确定度为0.0484 mg/kg,其结果可表示为(0.331±0.0484)mg/kg。结论测量结果的不确定度主要来源为试样提取液的测定、标准工作液的测定及配制,因此在实际检测工作中,可通过增加平行样和标准工作液的测定次数,提高检测质量。     

顶空-气相色谱法快速测定饮用酒类中甜蜜素含量

该实验建立了顶空-气相色谱（HS-GC）快速检测饮用酒类中甜蜜素的方法。样品经加热去除大部分乙醇和挥发性物质,样品提取液经衍生后,用顶空-气相色谱仪分析,以甜蜜素衍生产物环己烯为目标物,外标法定量。结果表明,当甜蜜素在饮用酒类中对应含量为1～100 mg/kg时线性关系良好（R2=0.998 9）,检出限和定量限分别为0.1 mg/kg和0.3 mg/kg,加标回收率为94.3%～107.1%,相对标准偏差（RSD）为2.5%～7.1%(n=6),精密度试验结果RSD为3.1%～4.9%。该方法简单、高效、环境友好、可靠、准确,可用于各种饮用酒类中甜蜜素的快速定量检测。     

A study of the solution properties of selected binary mixtures of bulk and intense sweeteners in relation to their psychophysical characteristics

The solution properties of binary mixtures of two bulk sweeteners (sucrose and maltitol) and three intense sweeteners (acesulfame K, aspartame and sodium cyclamate) were studied. The parameters measured were apparent specific volumes, isentropic compressibilities and compressibility hydration numbers. An attempt has been made to correlate the solution properties of some of the mixtures with their sweetness responses. Both specific volume and isentropic compressibility data have been used to interpret the possibility of synergism or suppression in the mixtures in terms of the affinity of the solutes for the surrounding solvent structure, and hence the effectiveness of transport of the molecules to their appropriate receptor sites. However, an understanding of the nature and stereochemistry of the individual components in the mixtures is necessary for predicting the packing characteristics of molecules in water and their accession to receptor sites. The intense sweeteners seem to play an important role in modifying the structure of water in solution. Although there is no clear proof of how this affects perception, fine differences in solution behaviour can be observed with isentropic apparent specific compressibility measurements. The study supports the idea that receptors lie at different depths in the lingual epithelium, and also that in two-component systems, one species may alter the packing efficiency of the other in solution sufficiently to effect a change in taste quality or intensity.     

甜味分子的多点结合甜味理论

关于甜味分子生甜机理 ,存在 3种理论解释 ,分别为AH/B理论、AH/B/X理论和多点结合理论。实践证明 ,这 3种理论都能合理解释各类甜味物质的生甜机理。其中多点结合甜味理论认为 ,人体受体蛋白包含 8个基本的甜味识别部位 ,分别为B、AH、XH、G1、G2、G3、G4和D ,它们与甜味分子相应的结合部位发生相互作用 ,受体蛋白由紧密的收缩构象改变为开放的展开构象 ,从而产生甜味刺激传导 ,甜味产生后 ,由于识别部位的极性或离子基团之间的静电作用力 ,将驱散甜味分子 ,使受体蛋白恢复原来的收缩构象。根据这一理论 ,可以合理构造各种糖分子及其衍生物的多点结合模型。蔗糖是B1、B2、AH1、AH2、XH1、XH2、G1、E1、G2、E2、G3、E3、G4、E4型甜味剂 ,D 葡萄糖是B1、B2、AH1、AH2、XH1、XH2型甜味剂 ,D 果糖是E1、E2、E3、E4型甜味剂。     

Sensory properties of some synthetic high‐intensity sweeteners in water solutions

BACKGROUND: When sucrose is eliminated from products to meet consumers' demand for calorie‐free products and substitutes are used, sweetness becomes an important characteristic. The objective of this study was to compare sensory properties of four sucrose substitutes: aspartame, acesulfame K, sodium saccharin and sodium cyclamate in water solutions. RESULTS: The lowest concentrations of sweeteners such as 0.35 g kg^?1 for aspartame and acesulfame K showed an equi‐sweet level relative to approx. 55 g kg^?1 aqueous sucrose solution, whereas 2.3 g kg^?1 sodium cyclamate and 0.4 g kg^?1 sodium saccharin relative to approx. 65 g kg^?1. Aspartame had almost the same sweetness potency as acesulfame K, whereas the remaining sweeteners differed completely. The four sweeteners showed their specific sensory profiles. Besides the characteristics of sweetness and bitterness, metallic and astringent attributes plus warming and cooling effects were found. CONCLUSIONS: Of the four sweeteners, aspartame and sodium cyclamate can be considered as the best sucrose substitutes due to their similar sensory profiles to the sucrose. The data showing the interdependence between sweetness intensity of the sweeteners and sucrose are useful as a quick and easy indicator of the sweetener amount having equi‐sweet levels relative to sucrose. Copyright © 2009 Society of Chemical Industry