Aroma–taste interactions between a model cheese aroma and five basic tastes in solution

The flavour perception of cheese results from complex sensory interactions between tastes and aromas. Using a model cheese solution, this study investigated perceived interactions between each of five basic tastes and a cheese aroma mixture containing ten volatile compounds commonly found in cheese. The five tastes – sucrose (sweetness), sodium chloride (NaCl) (saltiness), monosodium glutamate (MSG) (umami), lactic acid (sourness), and caffeine (bitterness) – were individually mixed with cheese aroma in water using a 5 taste level (0.2 log series) by 3 aroma level (0.5 log series) design. Aroma controls with no added taste were also included. This resulted in 18 samples for each single taste–aroma combination. An additional 18 samples were produced using a mixture of all 5 tastes with the 3 aroma levels. A panel of trained assessors (n = 10) evaluated cheese flavour intensity and taste intensity using 100 point line scales. Evaluation was carried out in duplicate, with samples grouped by taste type; 1 evaluation session per taste per replicate. Within type, order of presentation was balanced, and taste type order was randomised between replicates. Cheese flavour intensity was enhanced by sucrose and NaCl, while being suppressed by lactic acid. NaCl enhanced cheese flavour intensity the most at high aroma level, while lactic acid suppressed the most at low aroma level. When MSG level was increased, cheese flavour intensity was enhanced at both low and medium aroma levels, but was suppressed at the high aroma level. The greatest enhancement of cheese flavour intensity was found with the mixture of 5 tastes. Aroma significantly enhanced umami and bitterness, but did not enhance sweetness, saltiness, or sourness. This study showed that the perceived interaction between taste and cheese aroma depended on taste type and on the concentration levels of both taste type and aroma. The mixture of tastes was more effective at enhancing cheese flavour intensity than single tastes. This study provides knowledge that will underpin further study of taste–aroma interactions in a model cheese that aims to optimise cheese flavour intensity and character.     

“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。     

Study of taste-active compounds in the water-soluble extract of mature Cheddar cheese

The chemical composition of the water-soluble extracts of mature Cheddar cheese were identified, with the emphasis on understanding the interplay of compounds contributing to the savoury taste in Cheddar. The ultra-filtered water-soluble extracts of two mature Cheddar cheeses were fractionated by gel permeation chromatography (GPC). By sensory evaluation, two taste-active GPC fractions were identified from each cheese. On the basis of chemical profiling of these fractions, aqueous model tastant mixtures were prepared and sensory omission tests carried out. Glutamic acid, organic acids and mineral salts were the main tastants, whereas the other amino acids had a limited impact on taste. The characteristic umami taste was explained by a synergistic effect of glutamic acid and salts. Matching umami taste intensities were obtained from different concentrations of glutamic acid and salts. Unmasking of a bitter or sweet taste from mixtures of sub-threshold concentrations of amino acids without glutamic acids was also observed.     

Umami peptides: assessment of their alleged taste properties

 In the literature there are reports that 31 di-and tripeptides elicit umami (i.e. monosodium L-glutamate-like or MSG-like) or savoury tastes. However, the occurrence of “umami peptides” is questioned with regard to the high specificity of those that give an umami taste. A total of 12 dipeptides and 4 tripeptides were selected for a re-examination of their taste properties. Criteria were that: (1) their taste has been described as umami, savoury or brothy; (2) they have a threshold value; and (3) they should fit into the theoretical framework of L-glutamyl peptides discussed. The peptides – in aqueous solutions, at room temperature, at pH 6.0 and 4.0, and at concentrations well above the reported threshold values – were tasted. Panel members were selected on the basis of their ability to perceive the umami taste of 2.67 mM MSG at pH 6.0. None of the peptides tested was found to elicit an umami taste. The taste of L-glutamic acid in the peptides was lost and furthermore the taste of bitter amino acids in the peptides was no longer perceivable. Within the range of Glu-X peptides, even Glu-Glu and Glu-Asp, which have previously been reported to elicit umami tastes, did not taste MSG-like either in pure solution or in the presence of sodium chloride. The tripeptide Ala-Glu-Ala, reported to have an “umami threshold” value as low as 0.8 mM, was found not to have an umami taste or any other specific taste up to 10 mM. The general occurrence of umami peptides appears to be highly unlikely. Received: 6 December 1996     

Analysis of binary taste-taste interactions of MSG,lactic acid,and NaCl by temporal dominance of sensations

Temporal dominance of sensations (TDS) is a relatively novel sensory evaluation technique that measures the temporal evolution of sensory perception. The sensory properties of food or drink products have been described by TDS; however, basic sensory data on TDS are still lacking. We analyzed TDS data for solutions of three basic tastes (umami, salty, and sour) and their binary combinations. The duration of TDS for the main taste of each type of solution (monosodium glutamate [MSG] for umami, sodium chloride [NaCl] for saltiness, and lactic acid for sourness) increased in a concentration-dependent manner. In addition, the duration of the umami taste of MSG was longer than that of MSG/inosine 5′-monophosphate solution with an umami taste of equivalent intensity. The duration of NaCl saltiness was increased by coexistence with MSG and decreased by coexistence with lactic acid. On the other hand, the duration of the umami taste of MSG was suppressed by coexistence with NaCl but not lactic acid, while the duration of the sour taste of lactic acid was suppressed by MSG but not NaCl. These findings provide novel insight into the temporal sequence of basic taste perception during food consumption.     

Short communication: Influence of pulsed light treatment on the quality and sensory characteristics of Cheddar cheese

The objective of this study was to examine the effect of pulsed light (PL) treatment on the color, oxidative stability, and onset of molding of Cheddar cheese. Slices of sharp white Cheddar cheese of 2.5 × 5 cm were treated on one side with PL doses from 1.02 to 12.29 J/cm², sealed in polyethylene bags, and stored at 6°C for up to 1 mo. Peroxide value, color parameters, and the onset of molding were evaluated. No significant changes in color or peroxide value were observed for PL-treated samples compared with the untreated controls. Pulsed light was able to significantly delay surface molding during refrigerated storage, with a PL dose of 9.22 J/cm² delaying the onset of molding by 7 d. The effect of PL on the taste, appearance, and acceptability of Cheddar cheese slices treated with a PL dose of 9.22 J/cm² on each side was assessed. In triangle tests, 60 untrained panelists were unable to detect significant differences between the control and PL-treated samples, although PL had a significant effect on overall liking, flavor, and appearance. These findings suggest that although PL can be effective for surface decontamination of cheese, it may have some detrimental effects on sensory properties.     

基于电子舌技术的红茶滋味品质评价

目的研究电子舌技术在红茶滋味品质评价上的应用,探索电子舌评价结果同人工感官滋味审评结果间的关系。方法采用电子舌传感器响应值及滋味分值结合主成分分析、聚类分析等方法进行红茶滋味的评价,并同人工感官滋味结果进行比较;绘制滋味雷达图、酸鲜味等级评价图、滋味分属性间及感官滋味的相关性表。结果利用电子舌测定的数据结合主成分分析和聚类分析对茶样进行的分类结果同感官滋味分类结果一致;不同类别间的茶样滋味特点不同,滋味口感好的茶样鲜味强度值高而苦涩味值低;分属性滋味间的相关性显著。结论电子舌技术在红茶滋味的评价上有较好的应用,可以定性的区分不同滋味等级的茶样,且能定量的给出不同茶样间的酸、甜、苦、咸、鲜滋味的相对强度分值。     

Accelerated Maturation of Cheddar Cheese: Influence of Added Lactobacilli and Commercial Protease on Composition and Texture

The addition of live and heat-shocked Lactobacillus casei-casei L2A and Neutrase© was tested for its ability to accelerate the maturation of Cheddar cheese. An evaluation of physicochemical and rheological properties showed that cheese pH was decreased by bacterial and enzymatic additives, while fracturability and cohesiveness were influenced principally by Neutrase. The integrated process recommended is composed of three parts: first, the addition of live L. casei-casei L2A to control the undesirable microflora, second, heat-shocked cells of the same species at a concentration of 1.0%, and third, Neutrase at a concentration not higher than 1.0 × 10^-5 AU/g of cheese. This process led to a good-quality sharp Cheddar cheese with 60% increase in flavor intensity compared to control cheese.     

滋味物质间相互作用的研究进展

人类的味觉提供了有关食品质量及其组成的必要信息。人类可鉴别出食物的5 种基本味觉,即甜、咸、酸、苦和鲜味,但食物是多种滋味化合物组成的混合体系,因此滋味物质间相互作用是不可避免的。滋味物质间的相互作用发生在3 个层面,即化合物混合时的化学反应、一种物质对另一种物质滋味受体的影响、混合物质在大脑中的综合感知。其中研究较多的是滋味物质在第二层面上的相互作用。二元、三元及多元滋味物质之间的关系是复杂的：当滋味化合物低强度/浓度混合时呈现增强效应;中等强度/浓度往往呈现加和作用;高强度/浓度混合时常呈现抑制作用。另外,滋味感知受很多因素的影响,如温度、pH值、黏度、硬度、受试者生理状况等。滋味物质间相互作用的研究主要聚焦在饮料滋味改良、药品苦味掩盖和口腔护理产品开发等具有广阔研究前景。     

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.     

Reduced-fat cheddar cheese manufactured using a novel fat removal process

Normally, reduced-fat Cheddar cheese is made by removal of fat from milk prior to cheese making. Typical aged flavor may not develop when 50% reduced-fat Cheddar cheese is produced by this approach. Moreover, the texture of the reduced-fat cheeses produced by the current method may often be hard and rubbery. Previous researchers have demonstrated that aged Cheddar cheese flavor intensity resides in the water-soluble fraction. Therefore, we investigated the feasibility of fat removal after the aging of Cheddar cheese. We hypothesized the typical aged cheese flavor would remain with the cheese following fat removal. A physical process for the removal of fat from full-fat aged Cheddar cheese was developed. The efficiency of fat removal at various temperatures, gravitational forces, and for various durations of applied forces was determined. Temperature had the greatest effect on the removal of fat. Gravitational force and the duration of applied force were less important at higher temperatures. A positive linear relationship between temperature and fat removal was observed from 20 to 33 degrees C. Conditions of 30 degrees C and 23,500 x g for 5 min removed 50% of the fat. The removed fat had some aroma but little or no taste. The fatty acid composition, triglyceride molecular weight distribution, and melting profile of the fat retained in the reduced-fat cheeses were all consistent with a slight increase in the proportion of saturated fat relative to the full-fat cheeses. The process of fat removal decreased the grams of saturated fat per serving of cheese from 6.30 to 3.11 g. The flavor intensity of the reduced-fat cheeses were at least as intense as the full-fat cheeses.     

Sensory and mass spectrometric analysis of the peptidic fraction lower than one thousand daltons in Manchego cheese

A total of 107 different peptides, all derived from α_S1-, α_S2-, and β-casein, were identified in different fractions of artisan or industrial Manchego cheese at 4 and 8 mo of ripening, and their sequences were examined. Most of these peptides are described for the first time in Manchego cheese. Taste characteristics (umami and bitter) were assigned based on their AA sequence and the position of these AA within the sequence. The umami taste was predominant in all fractions analyzed by the panelists, and the peptides EQEEL, QEEL, and EINEL, containing a high number of glutamic residues, were found within the fractions. However, in several fractions described as having umami characteristics, no peptides responsible for this taste were detected. Therefore, compounds other than peptides seem to be involved in the umami properties of water-soluble extracts lower than 1,000 Da of Manchego cheese.     

Impact of nisin producing culture and liposome-encapsulated nisin on ripening of Lactobacillus added-Cheddar cheese

This study aimed to evaluate the effects of incorporating liposome-encapsulated nisin Z, nisin Z producing Lactococcus lactis ssp. lactis biovar. diacetylactis UL719, or Lactobacillus casei-casei L2A adjunct culture into cheese milk on textural, physicochemical and sensory attributes during ripening of Cheddar cheese. For this purpose, cheeses were made using a selected nisin tolerant cheese starter culture. Proteolysis, free fatty acid production, rheological parameters and hydrophilic/hydrophobic peptides evolution were monitored over 6 mo ripening. Sensory quality of cheeses was evaluated after 6 mo. Incorporating the nisin-producing strain into cheese starter culture increased proteolysis and lipolysis but did not significantly affect cheese rheology. Liposome-encapsulated nisin did not appear to affect cheese proteolysis, rheology and sensory characteristics. The nisinogenic strain increased the formation of both hydrophilic and hydrophobic peptides present in the cheese water extract. Sensory assessment indicated that acidic and bitter tastes were enhanced in the nisinogenic strain-containing cheese compared to control cheese. Incorporating Lb. casei and the nisinogenic culture into cheese produced a debittering effect and improved cheese flavor quality. Cheeses with added Lb. casei and liposome-encapsulated nisin Z exhibited the highest flavor intensity and were ranked first for sensory characteristics.     

Effect of galactose metabolising and non-metabolising strains of Streptococcus thermophilus as a starter culture adjunct on the properties of Cheddar cheese made with low or high pH at whey drainage

Cheddar cheese was made using control culture (Lactococcus lactis subsp. lactis), or with control culture plus a galactose-metabolising (Gal⁺) or galactose-non-metabolising (Gal⁻) Streptococcus thermophilus adjunct; for each culture type, the pH at whey drainage was either low (pH 6.15) or high (pH 6.45). S. thermophilus affected the levels of residual lactose and galactose, and the volatile compound profile and sensory properties of the mature cheese (270 d) to an extent dependent on the drain pH and phenotype (Gal⁺ or Gal⁻). For all culture systems, reducing drain pH resulted in lower levels of moisture and lactic acid, a higher concentration of free amino acids, and higher firmness. The results indicate that S. thermophilus may be used to diversify the sensory properties of Cheddar cheese, for example from a fruity buttery odour and creamy flavour to a more acid taste, rancid odour, and a sweaty cheese flavour at high drain pH.     

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.