Formation of bitter peptides in cheese and from casein]

Whereas a slightly bitter taste is desirable in certain foods, it is an off-flavour in cheese which may even lead to unfitness for consumption. Bitter principles from cheese have been found to be peptides with molecular weights ranging from 2000 to 3000. For the purpose of further characterization, bitter peptides were isolated from enzymatic casein hydrolysates as well as from bitter cheese and purified. 30 proteases from different origins proved to be able to form peptides with bitter taste of varying intensity from casein. Present experience shows that the formation of bitter peptides during casein hydrolysis can be inhibited only to a very small measure. Bitter peptides are extrmely resistant to proteases, which is probably attributable to their high contents of hydrophobic amino acids and hydrophobic bonds. The detection of only N- or C-terminal amino acid in each of 11 different bitter peptides shows that peptide chains are present and not cyclic peptides as repeatedly assumed. It must be aimed at avoiding the cheese defect "bitter" by using appropriate starter cultures and rennet substitutes as little disposed as possible to produce bitter peptides.     

Peptides from milk proteins and their properties

This review has attempted to study the literature pertaining to peptides derived from milk proteins. Hydrolysis of milk proteins to generate peptides has been practiced for a long time and it was recognized early on in this process that the taste of hydrolyzates might hinder use of these products in food formulations. Modification of protein is necessary to form a more acceptable or utilizable product, to form a product that is less susceptible to deteriorative reactions and to form a product that is of higher nutritionall quality. Modifications may be achieved by a number of chemical and enzymatic means. This review has considered only enzymatic modification of dairy proteins. Modified proteins contain peptides and some of these peptides have been purified and their functionalities have been compared with unmodified proteins. This paper has examined the literature pertaining to improvement in functionality of enzyme-modified proteins. Improvements in solubility, emulsification, foaming and gelation were examined. There is limited information available on the sequence of the peptides necessary to improve the functional characteristics of proteins. Knowing the sequences of desirable functional peptides can lead to genetic alteration of proteins to improve functionality. Addition of synthetic peptides to intact proteins may be another way in which the functionality of proteins can be augmented. Some of the peptides in milk proteins are capable of affecting biological functions of an organism. These effects can be antimicrobial and probiotic, i.e., prevent the growth and proliferation of undesirable and pathogenic organisms, or they may promote the growth of desirable bacteria in the digestive tract of humans and animals. Peptides derived from milk protein have been shown to exert digestive and metabolic effects as well. They may also influence the immune system. These biological effects may play an important role in the development of medical foods that treat or mitigate the effects of diseases. Proteins are allergens and therefore it is possible that products derived from modification of proteins may also be allergens. The known literature about the allergenicity of peptides derived from milk proteins has been examined in this article. Last, but not the least, the taste attributes of peptides is also considered. Bitterness of hydrolyzates is a common occurrence and the origins of these bitter peptides and possible ways of mitigating this sensory defect has been discussed. Many of the peptides that enhance functionality and exert biological activity are likely to be bitter. Therefore, the bitter taste of hydrolysis products has to be dealt with in boosting the functional or nutraceutical aspects of foods containing these peptides. Analytical techniques for sequencing peptides have become more accessible and purification of peptides is commercially feasible. Computer based modeling techniques have aided the prediction of structures in these peptides. These advances, coupled with the advances in biotechnology, promise to revolutionize the future of nutraceutical and functional foods.     

食品外肽酶的研究进展

外肽酶包括氨肽酶和羧肽酶两大类。当外肽酶催化多肽水解时,产物苦味减轻,同时生成的游离氨基酸和小肽类物质能够形成食品良好风味,或作为风味前体物质。外肽酶能够在食品后熟阶段起作用,如水果成熟、种子萌发和肉类陈化,也能够在食品加工处理过程中起作用,如干燥、热处理和发酵,从而决定终产品品质的优劣。外肽酶在食品中的重要应用主要体现在能够水解疏水性苦味肽,并去除苦味。本文较为系统地综述近年来外肽酶及其在食品中的研究现状,主要包括外肽酶的分类、结构、反应特性,以及在食品加工过程中对蛋白质水解产物的最终产品良好风味的贡献机制。     

苦味传递机制与苦味肽研究进展

味觉是人类的重要生理功能之一。人类能够识别五种基本味:苦味、咸味、酸味、甜味和鲜味。由食物蛋白水解产生的苦味肽成为研究热点。本文主要从苦味的信号传递机制、苦味肽结构特点、苦味肽消除或降低的方法等三个主要方面综述了苦味肽的研究进展,以期为低苦味食品开发研究提供参考。     

食品中的呈味肽及其呈味机理研究进展

呈味肽因其不同链长度和结构序列具有不同的滋味特征,包括甜味、苦味、酸味、咸味和鲜味。目前国内对于呈味肽的研究主要集中在其种类和数量的发掘阶段,关于呈味肽与味觉感受器相互作用而呈味的机理还不是十分清晰;而国外对于呈味肽的降血压、降血糖等生物活性功能以及5类呈味肽的相应呈味机理研究有相关新报道。本文阐述了食品中的呈味肽以及其在食品中的作用,并综述了其呈味机理的研究新进展,以期为食品风味研究及调味品的开发提供参考依据。     

Exopeptidases and their application to reduce bitterness in food: a review

When exopeptidases catalyze hydrolysis of peptide bonds, the product(s) may have a less bitter taste, and the free amino acids or small peptides formed may function in food as pleasant-tasting flavor compounds or as flavor precursors. There are several classes of exopeptidase based on specificity for hydrolysis of synthetic substrates. Exopeptidases in food-stuff may be of natural origin or may be extrinsic, that is, produced by microorganisms or parasites. Exopeptidases used to modify foods are also becoming increasingly available in the industrial enzyme market. Exopeptidases contribute to a variety of quality changes in postharvest fruit, meats, and food fermentations. Foodstuff impacted by these enzymes during processing include cocoa, beer, aged and cured meat products, koji, fish sauce, ripened cheeses, and protein hydrolysates. An important role of exopeptidases in food is the hydrolysis of hydrophobic, bitter peptides. The relationship between peptide structure and sensory transduction/receptor models is discussed. Research on the use of exopeptidases to reduce bitterness is reviewed.     

2,5-diketopiperazines in food and beverages: Taste and bioactivity

2,5-Diketopiperazines (2,5-DKPs) have been found to occur in a wide range of food and beverages, and display an array of chemesthetic effects (bitter, astringent, metallic, and umami) that can contribute to the taste of a variety of foods. These smallest cyclic peptides also occur as natural products and have been found to display a variety of bioactivities from antibacterial, antifungal, to anthroprotective effects and have the potential to be used in the development of new functional foods. An overview of the synthesis of these small chiral molecules and their molecular properties is presented. The occurrence, taste, and bioactivity of all simple naturally occurring 2,5-DKPs to date have been reviewed and those found in food from yeasts, fungi, and bacteria that have been used in food preparation or contamination, as well as metabolites of sweeteners and antibiotics added to food are also reviewed.     

Modelling relationship between angiotensin-(I)-converting enzyme inhibition and the bitter taste of peptides

Relationships between angiotensin-(I)-converting enzyme inhibition and the bitter taste of peptides were studied. In cases where ACE inhibition or bitter taste had not been experimentally determined, their activity was estimated using several different peptide quantitative structure–activity relationship (QSAR) models. Significant correlations between increased ACE inhibition and bitterness were found for dipeptides using both observed and QSAR-predicted values. The relationship between ACE inhibition and bitter taste was attributed to the importance of hydrophobicity for both properties. Limited structural variations for dipeptides could make it difficult to have features that limit the effect of C-terminal hydrophobicity, necessary for ACE inhibition, on bitter taste. A similar modelling approach was also done on data from observed bitter oligopeptides derived from milk proteins. The relationship between QSAR-predicted ACE inhibition and observed bitter taste was not as strong as that found for dipeptides. Larger structural variation possibilities for oligopeptides than for dipeptides may thus make it, more feasible to find a highly efficient ACE inhibitory oligopeptide with a negligible bitter taste than a dipeptide.     

Kokumi肽的特性及其制备研究进展

食物呈味特性十分复杂,无法用单一的基本味觉来进行描述,因此,习惯上用kokumi来形容食物中的浓厚感、丰富度、持续性、协调性和饱满圆润等一种综合性味觉感受。kokumi肽广泛存在于动物、植物和发酵食品中,其本身没有味道或味道较淡,但少量添加便能增强复合溶液或肉汤的基本味觉,并能赋予其浓厚感、持续性和协调性等特性。本文概括了kokumi肽的来源、结构特性、味觉特性和呈味机制等方面的研究进展,并结合其制备方法进行综述,以期为kokumi肽的深入研究和新型调味品的研究开发提供依据和参考。     

罗非鱼副产物蛋白水解肽的呈味分析

为了探究罗非鱼副产物蛋白水解物中滋味活性物质的来源,该研究以罗非鱼的鱼皮、鱼头和鱼骨为原料,采用中性蛋白酶、菠萝蛋白酶、风味蛋白酶、复合蛋白酶、木瓜蛋白酶和碱性蛋白酶分别对三种副产物进行酶解,分析比较水解度、分子量、前体蛋白与滋味活性物质的关系。结果表明：三种罗非鱼副产物经过风味蛋白酶水解酶水解8 h后获得最高水解度,分别为14.29%、23.7%和31.86%。经过木瓜蛋白酶水解的副产物酶解液均呈现出显著苦味或酸味,而鱼头经过碱性蛋白酶酶解得到的水解产物具有鲜味,鱼骨则经过菠萝蛋白酶水解得到鲜味,鱼皮经过中性蛋白酶水解表现出鲜味和酸味,但鱼头却呈现出苦味。通过LC-MS/MS鉴定,胶原蛋白、肌原纤维蛋白以及肌浆蛋白是罗非鱼副产物酶解液滋味活性肽的重要味觉活性前体,这些滋味肽的分子量大部分小于1500 u,肽段中疏水性氨基酸残基对罗非鱼副产物滋味的形成具有重要作用,其中蛋氨酸在酶解液的鲜味的形成中起重要贡献。     

扇贝裙边酶解过程中呈味组分的变化规律研究

本研究以扇贝裙边为原料,利用复合蛋白酶对扇贝裙边进行酶解,在确定扇贝裙边最佳酶解温度的基础上,探索了扇贝裙边酶解液在不同酶解时间下的呈味特点,并探讨了不同酶解液中呈味分子的变化规律,探明不同酶解时间下扇贝裙边酶解液的呈味规律。结果表明不同酶解时间制备酶解液的滋味存在显著性差异,其中8 h的扇贝裙边酶解液鲜味强度最高(9.32分),而12 h酶解液的苦味(7.33分)和饱满度(8.33分)最强。主要是因为酶解时间对酶解液鲜味氨基酸和苦味氨基酸的含量及比例存在较大影响,当酶解8 h时,扇贝裙边酶解液中鲜味氨基酸比例最高(46.80%),而苦味氨基酸比例最低(51.67%);此外,肽分子分布结果显示8h酶解液中5000 u的肽段(对呈味贡献小)和180 u的肽段(苦涩味明显)比例较低,可能是8 h扇贝裙边酶解液取较好的鲜味和饱满度,较低苦味的主要原因。本研究通过研究扇贝呈味组分在酶解过程中的变化规律,为工业上利用扇贝裙边制备高品质呈味基料提供理论基础和指导。     

Enzymatic hydrolysis of soy proteins and the hydrolysates utilisation

Soy proteins are very important protein source for human being and livestock. Enzymatic hydrolysis of soy protein can enhance or reduce its functional properties and improve its nutritious value. Soy protein hydrolysates were primarily used as functional food ingredients, flavour and nutritious enhancers, protein substitute, and clinical products. Conditions for hydrolysis were usually mild, whereas recently high pressure treatment attracted more interest. Degree of hydrolysis (DH) was usually between 1% and 39.5%. The main problem associated with proteolytic hydrolysis of soy protein was production of bitter taste, hydrolysates coagulation and high cost of enzymes. Bitterness reduction can be achieved by control of DH, selective separation of bitter peptides from hydrolysates, treatment of hydrolysates with exo‐peptidases, addition of various components [adenosine monophosphate (AMP), some amino acids, monosodium glutamate (MSG), etc.] to block or mask the bitter taste, and modification of taste signalling. Hydrolysates coagulation can be resolved by selecting appropriate enzymes and by applying immobilisation technology the production cost can be reduced. Enzymatic hydrolysis also enhances bioactivity of soy proteins through conversion of glycosides to aglycones, increasing antioxidant and immunoregulatory properties. Finally, future works have been discussed.     

The role of sour and bitter perception in liking,familiarity and choice for phenol-rich plant-based foods

Among factors influencing food preferences and choices, individual differences in taste perception play a key role in defining eating behaviour. In particular, sour and bitter responsiveness could be associated with the acceptance and the consumption of phenol-rich plant-based foods recommended for a healthy diet. The aim of this study was to investigate, in a large population sample, the associations among sour and bitter responsiveness and liking, familiarity and choice for plant-based foods characterized by these target tastes. Adults aged 18 to 60 years (n = 1198; 58% women) were tested for their sour and bitter responsiveness both in water solutions and in food models (pear juice-based beverages modified in citric acid content to induce different levels of sourness: 0.5, 2.0, 4.0 and 8.0 g/kg; chocolate pudding samples modified in sucrose content to induce different levels of bitterness: 38, 83, 119, 233 g/kg). Familiarity, stated liking and choice for fruit juices and vegetables varying for sour/bitter taste (high in bitter/sour taste: e.g. grapefruit juice and cauliflower; low in bitter/sour taste: e.g. zucchini and pineapple juice) were measured. Results showed a significant positive correlation between bitter and sour taste perception in water solutions and model foods, as well as a positive correlation between the perceived intensity of the two taste stimuli. Subjects characterized by high responsiveness to the two target stimuli were found to give lower liking scores to foods characterized by sour/bitter tastes and tended to choose less sour/bitter foods compared to less responsive subjects.Thus, food choice for phenol rich plant-based products could be associated with a reduced responsiveness to bitter and sour tastes and a consequent higher acceptance of food products characterized by these taste qualities.     

Interactions between umami and other flavor characteristics

Our understanding of the taste transduction mechanisms of umami substances is still in its infancy. However, evidence is now emerging that suggests that umami taste is perceived according to a receptor-mediated mechanism similar to those for sweet and bitter tastes. The synergistic interactions between glutamate and nucleotides appear to arise from an allosteric effect of nucleotides on a glutamate receptor. In some foods, umami substances appear to enhance the perceived sweetness or saltiness, or other flavor characteristics such as thickness and complexity, which may contribute to the ability of umami substances to improve overall palatability in certain foods.     

蛋白质酶解物苦味形成机理及控制研究

蛋白质酶解后产生不同程度苦味主要是由产物中含疏水性氨基酸低分子肽所形成,这些苦味严重影响蛋白质水解产物在食品工业中应用。该文综述不同食物蛋白质酶解物中苦味肽形成机理及蛋白质酶解物苦味的降低、去除及控制方法研究最新进展,主要包括选择性分离、苦味掩盖、酶法及微生物脱苦等。     

发酵食品源功能活性肽及其应用研究进展

随着老龄化人口加剧、亚健康人群增多和慢性疾病发病率的持续攀升,人们的健康意识不断增强,消费者对天然、营养、功能性食品的诉求日益凸显,呈现多元化和个性化发展趋势。活性肽是由氨基酸组成的小分子多功能化合物,具有显著的呈味、抑菌、抗氧化、降血压、调节免疫等功能,是功能食品、调味料、药品中的重要活性成分,是当前国际食品领域最热门的研究课题和极具发展前景的功能因子。发酵食品具有独特的风味品质和显著的益生功能,是活性肽的天然宝库,已从中挖掘出各种具有良好营养功能、呈味特性和生理活性的功能肽。本文综述了发酵食品源活性肽的分类、产生机制、呈味功能肽和生理活性肽的研究进展,展望了其在食品工业中的应用前景,以期为发酵食品源活性肽的进一步研究与开发利用提供参考。     

Use of enzymes to elucidate the factors contributing to bitterness in rye flavour

In spite of the health-beneficial character of whole grain rye its use may be limited because of bitter taste. The impact of non-volatile chemical compounds on the bitter taste of rye was analysed by the aid of enzymatic hydrolysis, releasing potentially flavour-active compounds from the rye matrix. Whole grain rye flour–water suspension was treated with hydrolytic enzymes, whereafter portions of the rye suspensions were baked into crackers, assessed for their sensory profile as well as solubilised hydrolysis products. Heat treatment reduced the perceived bitterness. The treatment with enzyme preparation with high protease activity increased the bitterness of rye and also wheat flour both as suspension and as crackers. Other enzymes tested (with high polygalacturonase, endo-glucanase, xylanase or amyloglucosidase activity) had no significant impact on the perceived bitterness. Thus, small molecular weight peptides were considered to be a significant contributor to the bitter note of rye.     

蛋白质水解物与苦味的构效关系及脱苦研究

蛋白质水解物具有多种生理活性,但呈苦味限制了其在食品工业中的应用.本文论述了蛋白质水解物与苦味的构效关系,简介了苦味的评价方法,并对蛋白质水解物的脱苦方法研究进展进行了综述,包括有选择分离法、掩盖法、酶法及联合脱苦法等.     

肉品中的寡肽及其呈味机制研究进展

呈味肽是从食物中提取或由氨基酸合成的,能够丰富、改善、掩盖肉品感官特性的肽类组分。呈味肽分为多肽和寡肽两类,其中赋予肉品滋味的主要是分子质量小于3000 Da的寡肽。此外,寡肽还具有多种生理功能,在参与人体免疫调节和生理代谢等方面具有重要意义。本文介绍了几种寡肽在肉品中的作用,综述了其在味觉生理学和受体等呈味机制的新进展,并从pH、加工方式、微生物和其他因素等角度阐述了影响寡肽呈味的因素,以期为肉制品滋味研究、新型健康食品的开发提供参考依据。     

实用类蛋白反应的作用机制及其对海洋源蛋白修饰的研究进展

类蛋白反应作为一种可以修饰生物活性肽的新方法,已经成为蛋白质食品研究的热点。海洋生物含有丰富的生物活性成分,其含有的蛋白肽具有多种人体代谢和生理调节功能。然而蛋白肽存在生物利用度有限、酶解液味苦等问题。本文在阐述类蛋白反应过程和机制的基础上,对类蛋白反应修饰提高海洋源活性蛋白肽的生物活性、改善蛋白的加工特性及减少蛋白酶解液苦味等研究进展进行了详细的介绍,以期为海洋源蛋白的深度利用以及高值化研究提供理论参考。