Organoleptic perception

For the detection of groundwater contamination it is important that MTBE is organoleptically perceptible by humans at low concentrations, so that in many cases a chemical analysis is initially not necessary for further investigations. The odour threshold of humans varies between 2.5 and 190 xgL and the taste threshold between 2.5 and 690 xgL [10]. 

Table 22.9. Compounds present in spices causing a hot burning organoleptic perception...

Organoleptic A material that influences a sensory organ, as in the perception of odor by the human nose. 

This article contains a detailed summary of the experiments carried out by LCA Coates Lorilleux aimed at evaluating the sensorial perception thresholds of ethyl acetate (and other solvents) used in rotogravure printing of flexible packaging for food. The methodological approach applied in the present study can be deemed a valid tool of study for the organoleptic behaviour of solvents and/or volatile compounds other than ethyl acetate that may be present inflexible materials. 8 refs. 

Physical Properties. The eight optically active menthols differ in their organoleptic properties [77]. (-)-Menthol has a characteristic peppermint odor and also exerts a cooling effect. The other isomers do not possess this cooling effect and are, therefore, not considered to be refreshing. ( )-Menthol occupies an intermediate position the cooling effect of the (-)-menthol present is distinctly perceptible. 

ORGANOLEPTIC. A term widely used to describe consumer testing procedures for food products, perfumes, wines, and the like in which samples of various products, flavors, etc. are submitted to groups or panels. Such tests are a valuable aid in determining the acceptance of tlie products and thns may be viewed as a marketing technique, They also serve psychological purposes and are an important means of e valuating the subjective aspects of taste, odor, color, and related factors, The physical and chemical characteristics of foods are stimuli for the eye, ear, skin, nose, and mouth, whose receptors initiate impulses that travel to the brain, where perception occurs. 

The first molecular event in odor perception is an interaction of an odorant with a receptor. Evidence exists that these receptors are proteins, i.e. chiral, so this first interaction should be enantioselective, meaning that these receptors react differently with the two enantiomeric forms of a chiral odorant leading to differences in odor strength and quality. In many cases, this fact has been observed.This paper describes the enantioselective syntheses of some known odorants of multiple chemical classes and discusses the differences of the organoleptic properties of their enantiomeric forms. 

The organoleptic properties of the two compounds are distinct. Striking is the difference in perception thresholds, which were found to be 1.5 ppb for the (-)-(S)-, and 100 ppb for the (+)- flJ-form. Qualitatively, the is described as more floral, reminiscent of rose petals, also having a winy character without the cork and the green apple note that are the characteristics of the (+)-( fl>form as well as of the racemic mixture. 

The sense of smell challenges chemical understanding. On the one hand, given the structure of a new molecule a chemist can predict its spectroscopic properties over a wide domain of electromagnetic frequencies. A mixture ordinarily displays a spectrum that superimposes the spectra of its individual components, unless they physically interact with each other. In the chemical senses, on the other hand, perceptions of mixtures often cannot be inferred from their constituents, even though the components do not interact at the molecular level. Moreover, no one can reliably predict the organoleptic properties (taste or smell) of a new molecule from its structure. Even if... 

The resulting polyether, after water elimination by vacuum distillation, does not have any perceptible organoleptic odour. 

The overall organoleptic impression is based on a harmonious balance between these two types of sensations, directly related to the type and concentration of the various molecules, such as anthocyanins, and especially tannins. One of their properties is to react with glycoproteins in saliva (mucine) and proteins in the mouth wall, modifying their condition and lubricant properties. A study of the reaction of the B3 procyanidins with synthetic, proline-rich proteins showed that three dimers were strongly bonded to the protein chains (Simon et al., 2003). According to the type and concentration of tannins, they may produce a soft, balanced impression or, on the contrary, a certain aggressiveness that is either perceptible as... 

The organoleptic role of 4-mercapto-4-methyl-pentan-l-ol, which smells of citrus zest, is more limited. Concentrations in wine are rarely over the perception threshold (55 ng/1), but this value may be reached in a few wines. 

At the same time, acetic bacteria are capable of esterifying the acetic acid that they form, producing ethyl acetate. The latter is responsible for the organoleptic characteristics of acescence, characterized by a very unpleasant, suffocating odor and an equally nasty impression of harshness and burning on the finish. The perception threshold of ethyl acetate (150 mg/1) is much lower than that of acetic acid (750 mg/1). 

Fig. 8.5. Wines classified according to their volatile phenol concentrations. Organoleptic effect. Percentage of phenol wines with a concentration S above the perception threshold (Chatonnet et ah, 1993b)...

The 2-mercaptoethanol concentrations of some wines with reduction odors may also be in the vicinity of the perception threshold. This compound, produced by yeast from cysteine in must (Rapp et al., 1985), may also contribute to the unpleasant odors in certain wines. At concentrations over 90 p.g/1, 2-methyl-tetrahydro-thiophenone tends to mask other flavors. The organoleptic impact of the other heavy sulfur compounds identified in wine is negligible. Indeed, although concentrations are higher in wines with reduction defects, they rarely reach the perception threshold. 

Organoleptic Properties. Stereochemical differences of enantiomeric excipients may influence perception by sensory organs. Kutti [17] reported as early as 1886 that the interaction of stereoisomer with chiral receptors led to chiral discrimination as a consequence of the formation of diastereomers. He observed that the dextrorotatory asparagine has a sweet taste whereas the levorotatory form is tasteless. Greenstein and Winitz [18] and Solms et al. [19] reported such differences for many amino acids. Shallenberger et al. [20] reported that for some monosaccharides, both isomers have similar sweetness. In contrast, aspartame (A-aspartylalanine methyl ester) is marketed as the l,l isomer because it is more than 100 times as sweet as sucrose. However, the l,d diastereomer of aspartame is bitter [11], It should be noted that the individual differences of perception of these properties could vary. 

Studies are carried out at three different storage conditions, that is, in refrigerated condition (RF 5°C 3°C), room temperature (RT 25°C 2°C/60% 5% RH), and elevated temperature (HT 40°C 2°C/75% 5% RH) for a period of 6 months. Active content assay, gel strength, PTT, viscosity, extrusion force, pH value, and organoleptic characters are measured at different predetermined time points (i.e twice in first month, and every month afterward) during the stability period of 6 months. Physical stability is noted by microscopy or by visual inspection at periodic time intervals (i.e., twice in first month, and every month afterwards) for any perceptible change in physical appearance, that is, odor, color, consistency, phase separation, etc. 

Water as a main constituent of most foods affects food stability, microbial as well as chemical, and is responsible for the consumer perception of many organoleptic attributes, i.e., juiciness, elasticity, tenderness, and texture. It is generally accepted that it is not the quantity of water in food but its thermodynamic state that is responsible for its influence on food stability and texture. The thermodynamic state of water in food is expressed by its activity, which is 0 for absolutely dry material and 1 for pure water. The lower the water activity the more stable is the food, and the texture changes from juicy and elastic to brittle and crunchy. 

Among organoleptic properties used for quality assessments of wines, astringency deserves particular attention. This complex sensation in the mouth occurs after tasting red wines, which are known for their characteristic high concentration of polyphenolic compounds called tannins. Neither the perception of astringency nor its molecular basis is understood fully, but it is accepted... 

Besides nutrients, foods contain many substances that influence the food sensory impression and its organoleptic properties. These food constituents are known as sensoriaUy active compounds. They determine the sensory value (quality) of foods, inducing an olfactory sensation (perception), which is described as the aroma, odour and smell, gustative perception, which is the taste, visual perception, which is the colour, haptic (tactile) perception, which is the touch and feel, and auditorial perception, which is the sound. The olfactory sensation is derived from odour-active compounds and the gustative perception from taste-active compounds. Flavour is the sensory impression determined by the chemical senses of both taste and smell and is caused by flavour-active food components. Haptic sensation is the texture, which is affected mainly by high molecular weight compounds, such as proteins and polysaccharides, often referred to collectively as hydrocoUoids. Geometric aspects of texture that evoke both haptic and visual sensations symbolise the terms appearance and shape. 

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