低值小杂鱼风味成分磁性超滤膜分离技术

为建立一种风味成分提取分离新方法,提高低值小杂鱼附加值,实现小杂鱼资源深度开发利用。采用生物酶解技术和磁性超滤膜分离技术得到低值小杂鱼中的风味成分,基膜为截留相对分子质量2000的聚砜超滤膜经原位生成法制备得磁性超滤膜。超滤分离实验结果表明:利用此膜在压力0.4MPa、磁场强度0.6T条件下可实现对小杂鱼酶解液中呈鲜味小肽的选择性分离;以目标产物中呈鲜味的氨基酸占总氨基酸的百分比为指标,比较胰蛋白酶、木瓜蛋白酶、中性蛋白酶、碱性蛋白酶分别与风味蛋白酶复合酶解所得风味成分的差异,结果显示碱性蛋白酶和风味蛋白酶的复合效果较好;由正交试验优化得到最佳酶解工艺条件为碱性蛋白酶用量2350U/g、风味蛋白酶用量700U/g、酶解温度55℃、酶解时间6h、料液比1:10(g/mL),由此工艺制备出富含鲜味肽和鲜味氨基酸的目标产物,得率为6.43%。磁性超滤膜技术可实现风味成分的选择性分离。     

Umami Taste Enhancement of MSG/NaCl Mixtures by Subthreshold L-α-Aromatic Amino Acids

l ‐Phenylalanine (l ‐Phe) and l ‐tyrosine (l ‐Tyr) are L‐α‐aromatic amino acids that have recently been discovered to be important components of the savory fractions of soy sauce in addition to l ‐glutamate. Their effects are evaluated on the umami or savory taste of monosodium L‐glutamate (MSG), with or without sodium chloride (NaCl). Because l ‐Phe at subthreshold concentration (1.0 mM) significantly enhances an umami taste of a MSG/NaCl mixture (P= 0.000), combinations of 4 subthreshold concentrations (0, 0.5, 1.5, and 5.0 mM) of l ‐Phe with a weakly suprathreshold MSG (4.0 mM) and NaCl (80 mM) mixture were then rated for salty and umami intensities relative to those of standard solutions. L‐Phe was found to significantly enhance the umami tastes of the MSG/NaCl mixtures when it was added in a concentration range of 0.5 to 5.0 mM (P= 0.000). However, neither the umami taste of MSG alone nor the salty taste of NaCl alone was intensified. In a further experiment, l ‐Tyr at the 3 subthreshold concentrations (0, 0.5, and 1.5 mM) studied was shown to have the same activity as L‐Phe. The phenomenon of umami or savory enhancement by subthreshold aromatic amino acids in the soy sauce system has been established.     

不同地域特色熏鸡非盐呈味物质比较分析

为探明市售熏鸡的滋味呈味物质差异,对我国不同地域特色熏鸡产品的滋味物质进行综合评价。选取6种具有不同地域特色的代表性品牌熏鸡为研究对象,对其游离氨基酸和核苷酸进行分析,利用滋味活性值和等鲜浓度(equivalent umami concentrations,EUC)值评价滋味物质的呈味作用和鲜味强度,通过电子舌评价不同熏鸡间的滋味轮廓差异。结果表明:6种不同地域特色熏鸡的游离氨基酸、核苷酸含量及味觉特征存在显著差异(P<0.05);谷氨酸和5’-肌苷酸(5’-inosinic acid,5’-IMP)是熏鸡中主要的鲜味物质;6种熏鸡的EUC值在0.56%~16.08%范围内;电子舌结果表明鲜味和丰富性是熏鸡重要的味觉特征,其中,聊城熏鸡的丰富性特征最强,藤桥熏鸡的鲜味特征最强。综上,谷氨酸和5’-IMP是熏鸡中主要的鲜味物质,鲜味是熏鸡最主要的呈味特征,鲜味物质的差异可能与当地饮食文化和消费习惯有关。     

食品中鲜味物质研究进展

鲜味作为五大基本味觉之一,对食品滋味具有重要贡献。食品中的鲜味物质(包括鲜味肽、有机酸、氨基酸、核苷酸以及复合鲜味剂等)以其营养、安全等特点,近年来逐渐成为食品鲜味科学领域以及鲜味调味品方面的研究热点,为相关食品风味的改善提供了理论参考及研究方向。本研究介绍了鲜味物质的发展过程,并对鲜味及鲜味物质的研究现状进行了综述。同时对鲜味物质的种类进行概述,并对食品中主要的鲜味物质检测方法研究进展进行总结,最后对食品中鲜味物质的发展进行展望,以便于为食品中仪器检测鲜味物质相关研究提供参考和依据。     

UMPred-FRL: A New Approach for Accurate Prediction of Umami Peptides Using Feature Representation Learning

Umami ingredients have been identified as important factors in food seasoning and production. Traditional experimental methods for characterizing peptides exhibiting umami sensory properties (umami peptides) are time-consuming, laborious, and costly. As a result, it is preferable to develop computational tools for the large-scale identification of available sequences in order to identify novel peptides with umami sensory properties. Although a computational tool has been developed for this purpose, its predictive performance is still insufficient. In this study, we use a feature representation learning approach to create a novel machine-learning meta-predictor called UMPred-FRL for improved umami peptide identification. We combined six well-known machine learning algorithms (extremely randomized trees, k-nearest neighbor, logistic regression, partial least squares, random forest, and support vector machine) with seven different feature encodings (amino acid composition, amphiphilic pseudo-amino acid composition, dipeptide composition, composition-transition-distribution, and pseudo-amino acid composition) to develop the final meta-predictor. Extensive experimental results demonstrated that UMPred-FRL was effective and achieved more accurate performance on the benchmark dataset compared to its baseline models, and consistently outperformed the existing method on the independent test dataset. Finally, to aid in the high-throughput identification of umami peptides, the UMPred-FRL web server was established and made freely available online. It is expected that UMPred-FRL will be a powerful tool for the cost-effective large-scale screening of candidate peptides with potential umami sensory properties.     

酵母抽提物在热反应中鲜味的变化及肽的鉴定

通过不同温度热处理酵母抽提物后测定核苷酸、鲜味氨基酸的浓度变化趋势及肽分布变化,利用电子舌对感官特性进行评价。发现在相同浓度下不同温度热处理后酵母抽提物的鲜味强度不同,处理温度为110?℃时鲜味最强。选择鲜味较强的样品进行感官评价,结合超滤、凝胶渗透色谱、超高效液相色谱-四极杆-飞行时间-串联质谱技术对鲜味肽进行分离纯化,鉴定出Gln-Leu、Pro-Glu-Thr、Ala-Pro-Ala和His-Val 4?种鲜味肽段。     

Non-volatile taste components of Agaricus blazei, Agrocybe cylindracea and Boletus edulis

Three species of dried mushrooms are commercially available in Taiwan, namely Agaricus blazei (Brazilian mushroom), Agrocybe cylindracea (black popular mushroom) and Boletus edulis (king bolete), and their non-volatile taste components were studied. All mushrooms were high in contents of carbohydrate, crude fiber and protein but low in contents of crude ash and fat. Arabitol, myo-inositol, mannitol and trehalose were detected in these three mushrooms, whereas glucose was not found in B. edulis. Contents of total soluble sugars and polyols ranged from 150.33 to 225.08 mg/g. Total free amino acid contents were low in these three mushrooms and ranged from 8.97 to 14.91 mg/g. The contents of MSG-like components ranged from 1.24 to 4.40 mg/g were in the descending order of the A. blazei, A. cylindracea and B. edulis. Total 5′-nucleotides contents of A. blazei and A. cylindracea were higher than that of B. edulis whereas flavor 5′-nucleotides content of A. blazei was higher than those of A. cylindracea and B. edulis. Equivalent umami concentrations values in three mushrooms ranged from 10.46 to 135.90 g per 100 g. Overall, these three mushrooms possessed highly umami taste.     

Prediction,molecular docking and identification of novel umami hexapeptides derived from Atlantic cod (Gadus morhua)

This paper investigated umami hexapeptides derived from myosin of Atlantic cod (Gadus morhua) using homology modelling, molecular docking, taste evaluation and e-tongue verification. After hydrolysing and prediction in silico, potential bioactivity, toxicity and physicochemical properties of 48 hexapeptides were predicted. Five hexapeptides were selected to dock with the T1R1–T1R3 homology model which was built with SWISS-MODEL. Docking results showed that the five hexapeptides could enter the docking region, and INKPGL, SDSCIR and GPDPER had the lowest CDOKER_ENERGY. E-tongue result showed that the umami and richness value of all the three hexapeptides in 0.4 mg mL⁻¹ were higher than a 0.1% MSG solution. Sensory evaluation result showed that INKPEL had the strongest umami taste among the three hexapeptides and the umami threshold value was 0.25 mg mL⁻¹. These results suggested that homology modelling can be used for predicting umami peptides, and three umami hexapeptides were identified by in silico screening.     

In silico identification of novel small molecule umami peptide from ovotransferrin

Umami ingredients are the important components of seasoning in food and widely used in food production. However, few novel umami peptides were isolated and identified. Here, the purpose of this research is to identify small molecule umami peptides derived from ovotransferrin by molecular docking. Based on the virtual enzymatic hydrolysis and molecular docking analysis, the tripeptide DEK with the lowest CDOCKER-ENERGY (−99.50 kcal mol⁻¹) was identified, which could occupy the extracellular venus flytrap domain (VFTD) of T1R1/T1R3 (taste receptor type 1, member 1 and 3). Furthermore, the electronic tongue was used to measure the umami taste of DEK. The results showed that the umami value of DEK was 2.31, which was higher than that of monosodium L-glutamate via electronic tongue analysis. The docking results showed that virtual screening and molecular docking may be a more reliable and rapid method to substitute for classical methods for screening and identification of small molecule umami peptides.