Thermal Degradation of Flavor Enhancers, Inosine 5'-monophosphate, and Guanosine 5'-monophosphate in Aqueous Solution

The mechanism of thermal degradation of inosine 5′-monophosphate (IMP) and guanosine (GMP) was investigated kinetically in aqueous solution as a function of pH and temperature. The degradation of IMP and GMP followed first order kinetics. The rate constants were considerably affected by pH and temperature. The half-life times at 100°C were: IMP, 8.7 hr (pH 4.0), 13.1 hr (pH 7.0), 46.2 hr (pH 9.0); GMP, 6.4 hr (pH 4.0), 8.2 hr (pH 7.0), 38.5 hr (pH 9.0). These times were shortened to about one-third by raising the temperature 10°C. The predominant degradation products were nucleosides and phosphoric acid, indicating that the main reaction of the thermal degradation was the hydrolysis of the phosphoric ester bond in the nucleotides.     

热风微波联合干燥过程中南美白对虾滋味物质变化研究

为研究热风微波联合干燥过程中南美白对虾滋味物质的变化,测定了其呈味核苷酸与游离氨基酸含量,同时根据干燥过程中虾肉水分含量计算两者的干基含量变化,并计算虾肉味精当量.研究结果表明:虾肉干燥过程中,呈味核苷酸中肌苷酸含量最高,干制虾肉肌苷酸含量为405.96 mg/100 g,且始终高于阈值,对干制虾肉的鲜味形成有显著贡献;相比鲜样,干制南美白对虾中肌苷酸与单磷酸腺苷干基含量均显著下降;在虾肉中谷氨酸对鲜味形成有显著贡献,甘氨酸、丙氨酸与精氨酸对甜味形成有贡献,苯丙氨酸、赖氨酸与组氨酸能产生苦味;而在干燥过程中鲜、甜味氨基酸相对含量不断上升,分别从3.77％和17.03％上升到4.29％和35.84％;游离氨基酸总干基含量始终下降,但甘氨酸、丙氨酸、精氨酸与脯氨酸4种可以形成良好滋味的游离氨基酸干基含量上升;虾肉中肌原纤维蛋白与肌浆蛋白的干基含量均不断下降,部分分解为游离氨基酸;虾肉味精当量整体呈显著上升趋势,但在微波干燥初期(前40 s)显著下降,干制南美白对虾味精当量为3.50 g/100 g,远高于鲜虾(0.53 g/100 g),且虾肉味精当量始终远高于阈值.研究结果表明,由热风微波联合干燥引起的水分挥发与物质变化能够促进南美白对虾滋味形成.     

Concentration of Umami Compounds in Pork Meat and Cooking Juice with Different Cooking Times and Temperatures

This study examined the concentrations of umami compounds in pork loins cooked at 3 different temperatures and 3 different lengths of cooking times. The pork loins were cooked with the sous vide technique. The free amino acids (FAAs), glutamic acid and aspartic acid; the 5′‐nucleotides, inosine‐5′‐monophosphate (IMP) and adenosine‐5′‐monophosphate (AMP); and corresponding nucleoside inosine of the cooked meat and its released juice were determined by high‐performance liquid chromatography. Under the experimental conditions used, the cooking temperature played a more important role than the cooking time in the concentration of the analyzed compounds. The amino acid concentrations in the meat did not remain constant under these experimental conditions. The most notable effect observed was that of the cooking temperature and the higher amino acid concentrations in the released juice of meat cooked at 80 °C compared with 60 and 70 °C. This is most likely due to the heat induced hydrolysis of proteins and peptides releasing water soluble FAAs from the meat into the cooking juice. In this experiment, the cooking time and temperature had no influence on the IMP concentrations observed. However, the AMP concentrations increased with the increasing temperature and time. This suggests that the choice of time and temperature in sous vide cooking affects the nucleotide concentration of pork meat. The Sous vide technique proved to be a good technique to preserve the cooking juice and the results presented here show that cooking juice is rich in umami compounds, which can be used to provide a savory or brothy taste.     

Hypoxanthine Ratio Determination in Fish Extract Using Capillary Electrophoresis and Immobilized Enzymes

Fish freshness was assessed using capillary electrophoresis and an immobilized enzyme procedure to monitor degradation of inosine-5′-monophosphate (IMP), inosine (HxR) and hypoxanthine (Hx). The enzymatic method used an amperometric probe at + 0.7 V (platinum vs silver/silver chloride) with immobilized xanthine oxidase, catalase, nucleoside phosphorylase, and nucleotidase for converting Hx, HxR or IMP to uric acid. Capillary electrophoresis resolved IMP, inosine and Hx by migration rates resulting from an applied electric field (416 V/cm, 50 μA). Components were detected at 250 nm. The H ratio of Hx/[IMP + HxR + Hx] and simplified K value of [HxR + Hx]/ [IMP + HxR + Hx] were determined in cod, salmon and trout stored on ice (0-4°C) and at 20°C. The two procedures agreed and for all species H ratio and K values increased with storage time.     

Characterization of Quality Deterioration in Yellowfin Tuna

The spoilage pattern of thawed yellowfin tuna carcasses was examined. After five days storage at 10° and 18°C, bacterial counts were low (< 10³) although visible softening of the flesh was apparent. Direct measurement of ethanol as an indicator of pre-process spoilage also failed to reflect differences among carcasses which were aged for up to five days. Analysis of nucleotides by high performance liquid chro-matography suggested that the ratio of inosine monophosphate (IMP) to other nucleotides may be a valuable indication of spoilage time where the IMP ratio decreased linearly with time after thawing. Average recoveries of adenosine monophosphate, inosine monophosphate, inosine and hypoxanthine were 50%, 75%, 64% and 92%, respectively, from spiked tuna which had been cooked at 122°C for 67 min.     

呈味核苷酸及其在食品调味中的应用

以5′-肌苷酸和5′-鸟苷酸为代表的5′-核苷酸及其一些衍生物,已逐渐应用于食品的调味中.本文综述了5′-核苷酸及其一些衍生物呈鲜味特点、呈味性质与化学结构的关系以及在食物调味中的运用情况.以便为进一步开发和利用5′-核苷酸类鲜味调味剂提供资料.     

利用1H NMR分析小龙虾的特征性滋味组成

为深入研究小龙虾的非挥发性滋味活性物质,利用1H核磁共振（nuclear magnetic resonance,NMR）对小龙虾中游离氨基酸、核苷酸、有机酸、可溶性糖和生物碱等滋味成分进行定性定量分析,并采用味道强度值（taste activity value,TAV）分析其味觉活性成分,以及通过味精当量（equivalent umami concentration,EUC）评价鲜味。结果表明,使用1HNMR共检测到小龙虾中33种滋味化合物,其中精氨酸、组氨酸、谷氨酸、丙氨酸、赖氨酸、甘氨酸、5’-单磷酸腺苷二钠、5’-单磷酸肌苷二钠、琥珀酸和乳酸的TAV大于1,它们对小龙虾的滋味有重要影响。EUC值以谷氨酸钠质量计,发现小龙虾样品的EUC值为9.1 g/100 g,说明小龙虾具有非常强烈的鲜味。     

南美白对虾虾头自溶产物主要呈味成分分析

以南美白对虾虾头为原料,制备风味良好的自溶产物。采用高效液相色谱法、原子吸收光谱等方法分析其主要的呈味物质。结果表明：游离氨基酸含量丰富,总量达9300mg/L,其中天门冬氨酸、谷氨酸、甘氨酸、丙氨酸4 种呈鲜味氨基酸的总含量达2130mg/L,占总游离氨基酸的22.9%;核苷酸及其关联化合物中,与鲜味有着密切联系的肌苷酸(IMP)含量为6.12mg/L;无机质离子Na+、K+、Cl －含量分别达663.7、182.1、417.2mg/L;甜菜碱、乳酸和琥珀酸含量分别达2400、15.27、13.32mg/L。这些成分都影响着南美白对虾虾头自溶产物的鲜味、甜味及整体的滋味。     

Applications of Polarography for Assessment of Fish Freshness

Fish freshness was assessed with an enzymatic method using a polarographic probe at 0.7 volt (platinum vs silver) to monitor degradation of inosine monophosphate (IMP), inosine (H × R), and hypoxanthine (Hx). The K-value, a ratio of H × R + Hx/IMP + H × R + Hx, was determined in Sockeye salmon, Pacific cod and Pacific herring in ice and at 12°C. Results were compared with those from HPLC and sensory scores. K-values by polarography correlated well with HPLC. Loss of freshness accompanied rise in K-value in all studies. Sensory scores correlated relatively well with K-values in Sockeye salmon and Pacific herring but less with Pacific cod. K-value did not reflect eating quality of Pacific cod.     

暂养净化及无水保活中太平洋牡蛎活力品质与呈味物质分析

为探明太平洋牡蛎(Crassostrea gigas)采捕后不同流通阶段活力品质与呈味物质的变化规律，模拟产业流通实际，将活体太平洋牡蛎进行暂养净化、诱导休眠和无水保活，并在不同时间段取样，以腺苷三磷酸(adenosine triphosphate,ATP)关联物、核苷酸能荷值(adenylate energy charge,AEC)及游离氨基酸变化分析牡蛎活力品质的变化；以呈味化合物含量结合呈味强度值评价流通过程中牡蛎风味品质变化。结果显示，采捕后运输及环境胁迫对其活力、呈味物质有显著影响，通过24 h暂养净化，牡蛎活力品质均呈明显恢复，其中ATP、AEC、游离氨基酸总量较净化前明显上升(P<0.05)，机体活力达到新水平；诱导休眠至保活流通阶段，牡蛎受到低温、缺氧胁迫需调动更多能量物质以维持机体平衡，各项活力品质指标较净化前明显降低(P<0.05)，处于稳定的较低水平。呈味化合物中，牡蛎在暂养净化后鲜甜味氨基酸增加，苦味氨基酸下降，随着保活时间的延长，呈味氨基酸缓慢下降；鲜甜味核苷酸肌苷5’-单磷酸(inosine 5’-monophosphate,IMP)、单磷酸腺苷...     

两种饲养方式下苏尼特羊肉中鲜味物质含量及相关调控基因表达量

为研究不同饲养方式下羊肉的风味特性,以舍饲、放牧两种方式饲养的12 月龄苏尼特羊股二头肌、背最长肌、臂三头肌3 个部位为实验材料,分别测定味觉指标、鲜味物质含量以及相关调控基因表达量并进行比较分析。结果表明：放牧饲养羊肉鲜味和咸味高于舍饲饲养,苦味和涩味低于舍饲饲养;放牧饲养羊肉中的肌苷酸（inosinic acid,IMP）和肌苷（inosine,INO）含量显著高于舍饲饲养（P＜0.05）;放牧饲养羊背最长肌的腺苷一磷酸脱氨酶（adenosine monophosphate deaminase 1,AMPD1）基因表达量显著高于舍饲饲养（P＜0.05）,股二头肌的腺苷酸琥珀酸裂解酶（adenylosuccinate lyase,ADSL）和次黄嘌呤核苷酸环水解酶（aminoimidazole carboxamide ribonucleotide transformylase,ATIC）基因表达量显著高于舍饲饲养（P＜0.05）;放牧饲养羊肉AMPD1表达量与ADSL表达量之间呈极显著正相关（P＜0.01）;通过分析鲜味物质含量与调控基因表达量的相关性,发现放牧饲养羊肉IMP含量与AMPD1基因表达量之间呈极显著正相关（P＜0.01）,与ATIC基因表达量之间呈显著正相关（P＜0.05）;舍饲饲养羊肉IMP含量与ATIC基因表达量之间呈显著正相关（P＜0.05）。综上,当鲜味物质调控基因的表达量高时,肉中的鲜味物质含量也随之提高。     

Umami Increases Consumer Acceptability,and Perception of Sensory and Emotional Benefits without Compromising Health Benefit Perception

This study was undertaken to understand how consumers in the United States perceive umami‐rich products, specifically low sodium chicken noodle soup. Results suggest that the addition of monosodium l ‐glutamate (MSG) at a concentration of 0.1% to 0.5%, alone or in synergy with 5’‐ribonucleotides of inosine monophosphate (IMP) at 0.1% not only increases consumer acceptance but also positively impacts other aspects of consumer perception. Regardless of concentration of MSG and IMP, samples enhanced in umami compounds were perceived as more savory, flavorful, and less bland while providing a more homemade, fresh, and healthy wholesome taste than a control sample. From a functional and emotional benefit standpoint, when consuming umami‐rich samples, consumers reported feeling significantly higher general satisfaction (they felt more content, relaxed, satisfied, less disappointed, dissatisfied…) and heightened positive emotions (happy, excited, indulgent…) than under the control condition. The feeling of being healthy while consuming the dish was not compromised. Last, when asked how they would feel if serving the soup sample to their family or friends, consumers projected feeling more positively under the umami‐rich conditions (more happy, competent, loving, less dissatisfied or disappointed) compared to the control condition.     

Flavor Compounds of Beef Broth as Affected by Cooking Temperature

Of various cooking temperatures studied, broth from beef obtained on heating at 85°C for 60 min had the most intense brothy flavor. The components of the fractions with brothy flavor were isolated by gel filtration chromatography and characterized. A significant correlation between cooking temperature of the broth and the concentration of certain compounds such as free amino acids (FAA) (r = 0.88, p<0.005), camosine (r = 0.83, p <0.005) and inosine 5′-monophosphate (IMP) (r = 0.94, p<0.005) was detected. Because these results correspond to those of sensory evaluation, it was concluded that a wide mixture of FAA, peptides of low molecular weight (< 300 daltons) and IMP played an important role in the flavor intensity of beef broth.     

通电加热过程中凡纳滨对虾虾肉糜的游离氨基酸和核苷酸含量变化研究

为研究通电加热过程中不同加热温度(40、55、65、75、85和95℃)对凡纳滨对虾虾肉糜中主要非挥发性滋味成分的影响,采用氨基酸自动分析仪和高效液相色谱仪分别检测了虾肉糜中的游离氨基酸和核苷酸及其关联产物含量,并采用味道强度值(TAV)确定其中主要的呈味物质及贡献程度,最后通过味精当量(EUC)分析鲜味氨基酸和呈味核苷酸之间的协同作用,并对其鲜味进行评价。结果表明,与鲜虾相比,通电热处理的虾肉糜中游离氨基酸总量均有不同程度的减少。随着温度的升高,鲜味氨基酸、甜味氨基酸和苦味氨基酸的含量均呈现先减少后增加的趋势,且在65℃达到最小值(鲜味氨基酸、甜味氨基酸和苦味氨基酸的总TAV值分别为0.86、4.40、4.46)。通电加热并不影响ATP的降解途径只是会改变核苷酸及其关联产物的相对含量,尤其是促进Ado的产生。甘氨酸、精氨酸、谷氨酸、AMP和IMP在不同加热温度下其TAV几乎都大于1,是虾肉糜滋味的主要贡献者。味精当量以谷氨酸钠质量计,40℃最能促进虾肉糜鲜味的产生(EUC值为5.54 g MSG/100 g),在85℃处虾肉糜风味损失最小(EUC值为4.02 g MSG/100 g)。     

Degradation of organophosphorus pesticides in aqueous extracts of young green barley leaves (Hordeum vulgare L)

The degradation of the organophosphorus pesticides malathion, chlorpyrifos, guthion, diazinon, methidathion and parathion in an aqueous extract of young green barley leaves (Hordeum vulgare L) was monitored by gas chromatography. Aqueous solutions of various amounts of freeze‐dried young barley leaves containing 5.75 mg l⁻¹ of malathion were incubated at 37 °C and pH 7.4 over prolonged time periods. Over 95% of the malathion degraded in 4 h in a 3% (30 g l⁻¹) solution of young green barley leaves. When the barley solution was autoclaved at 120 °C for 25 min prior to the addition of malathion, no degradation of malathion was observed. When 10 mg l⁻¹ each of the above six pesticides was incubated in a 15% (150 g l⁻¹) solution of young green barley leaves for 3 h at 37 °C and pH 7.4, malathion and chlorpyrifos degraded 100%, whereas parathion (75%), diazinon (54%), guthion (41%) and methidathion (23%) showed lesser degrees of degradation. © 1999 Society of Chemical Industry     

加工方式对玉筋鱼干风味的影响

为研究加工方式对玉筋鱼干风味的影响，实验按加工方式分为加盐煮制冷风干燥（boiling in salt solution followed by cold air drying，SCC）组和冷风干燥（cold air drying，CD）组。采用电子鼻技术、气相离子迁移谱（gas chromatography-ion mobility spectroscopy，GC-IMS）技术、氨基酸自动分析技术、高效液相色谱技术测定玉筋鱼干中的风味成分。结果表明，不同加工方式制作的玉筋鱼干在气味、滋味方面存在显著差异。电子鼻、GC-IMS技术均能区分不同工艺制作的玉筋鱼干气味，采用GC-IMS技术共分析出68 种挥发性成分，庚醛、戊醛、3-甲基丁醛对玉筋鱼干独特风味的形成有重要影响，其中3-甲基丁醛源自CD工艺，其区别于SCC工艺气味的关键物质。玉筋鱼干中的主要鲜味氨基酸是Glu，主要呈味核苷酸是肌苷酸；CD组玉筋鱼干中的鲜味氨基酸和甜味氨基酸含量占总游离氨基酸的比重高于SCC组，同时CD组滋味活性值、味精当量值均高于SCC组，所以仅采用CD工艺制作的玉筋鱼干滋味优于加盐煮制后CD工艺制作的玉筋鱼干。     

Effect of Adenosine-Nucleotides and Their Derivatives on the Denaturation of Myofibrillar Proteins in vitro during Frozen Storage at −20°C

To investigate the effect of adenosine-nucleotides and their derivatives on the denaturation of myofibrillar proteins, 235 nmoles/mL adenosine-5′-diphosphate (ADP), adenosine-5′-monophosphate (AMP), inosine-5′-monophosphate (IMP), inosine (HxR), or hypoxantine (Hx), was added to 3 mg/mL actomyosin (AM) solution suspended in 0.10M KC1 solution and stored at ?20°C for 12 wk. The AM was extracted from milktish dorsal muscle. Protein denaturation was evaluated by measuring solubility, Ca-ATPase and Mg(EGTA)-ATPase activity of AM, by analyzing changes in electrophoretic profiles and transmission electron microscopy. Inosine and hypoxanthine accelerated protein denaturation compared to control samples. Infrared spectrum analyses indicated that negatively charged groups of these nucleotides interacted with amino or imino groups on AM after addition. ADP, AMP, and IMP had a protective effect on denaturation of AM during frozen storage at ?20°C.     

Degradation kinetics of anthocyanins from purple sweet potato (Ipomoea batatas L.) as affected by ascorbic acid

Storage (4°C and 25°C, 28 days) and thermal (70°C–90°C, 6 h) stabilities of purple sweet potato anthocyanins (PSPAs) with varying concentrations of ascorbic acid (AA) were investigated in a model soft drink medium. For storage stability, the model drink was sterilized at 85°C for 15 min prior to storage. Zero-order kinetics and first-order kinetics were fitted for storage degradation at 4°C and 25°C, respectively. However, all data for thermal degradation fitted first-order kinetics. The temperature dependence on degradation was modeled after the Arrhenius equation. Storage degradation of PSPAs was increased by the presence of AA (40–360 mg/L). Retarded thermal degradation was be achieved by adding 120 mg/L of AA, while accelerated thermal degradation resulted from 360 mg/L of AA. Heat treatment did not markedly change the DPPH radical-scavenging activity of PSPAs.