Salt taste thresholds

Flavor enhancers are used imiversally in the food and pharmaceutical industries. Sugar, carboxylic acids (e.g., citric, malic, and tartaric), common salt (NaCl), amino acids, some amino acid derivatives (e.g., monosodium glutamate—MSG), and spices (e.g., peppers) are most often employed. Although extremely effective with proteins and vegetables, MSG has limited use in pharmaceuticals because it is not a sweetener. Citric acid is most frequently used to enhance taste performance of both liquid and solid pharmaceutical products, as well as a variety of foods. Other acidic agents, such as malic and tartaric acids, are also used for flavor enhancement. In oral liquids, these acids contribute unique and complex organoleptic effects, increasing overall flavor quality. Common salt provides similar effects at its taste threshold level in liquid pharmaceuticals. Vanilla, for example, has a delicate bland flavor, which is effectively enhanced by salt. 

IMP and GMP are non-hygroscopic salts. They are stable towards heat (up to 120°C) and acidity (optimum pH is 5-7) [2, 8, 9]. Taste thresholds in aqueous solution are 25-120 ppm and 12-35 ppm for IMP and GMP, respectively [2, 8, 10]. Use of IMP and GMP in liquid foods may present some problems. Many vegetable and animal foods contain phosphomonoesterases which can easily split the phosphomonoester linkage of the ribonucleotides and the flavour improving effect is lost. From a practical standpoint, these enzymes should be inactivated by heating to 85°C before the addition of IMP or GMP. 

Last but not least, it must be mentioned that sodium chloride (often referred to as the poor man s flavour enhancer ) has a flavour enhancing effect at usage levels below and above its taste threshold (370 to 5000 ppm). Without salt, many foods (both sweet and savoury) have a flat taste. Salt may enhance sweemess and mouthfeel and decrease bitter, sour and metallic sensations [4, 32]. Even in sweet foods such as cakes, candies and toffees, salt has its place. However, its presence is most critical for... 

The influence of flavor potentiators on the basic taste sensations is controversial. Early studies suggested that MSG intensified the sweetness or saltiness of a food when these tastes were near their optimum level while sourness and bitterness were found to be suppressed in some food systems [24]. However, Lockhart and Gainer [25] found no enhancement of either sweet or salt tastes by MSG. Mosel and Kantrowitz [26] also found no enhancanent of either sweet or salt tastes but substantial reductions in the sensory thresholds of sour (2x) and bitter (30x). Van Cott et al. [27] found the opposite that sweet and salt thresholds were lower, and sour and bitter showed no change. Yamaguchi and Kimizuka [28] found no significant influence of MSG on any of the basic tastes. 

Table 8.3. Taste threshold values of some alicyclic sulfamic acids (Na-salts)...

The corrosive effects to be considered (mainly simple corrosion of metals) are, as would be expected from the edible nature of foodstuffs which are not excessively either acidic or basic but which may contain sulphur, less severe than those often encountered with inedible materials containing reactive substances. The importance of corrosive efiects where foodstuffs are concerned lies not so much in the action of the foodstuffs on the metal involved as in the resultant metal contamination of the foodstuff itself, which may give rise to off-flavours, in the acceleration of other undesirable changes (by the Maillard reaction for example), and in the possible formation of toxic metallic salts. Metal ions generally have threshold values of content for incipient taste effect in different liquid foodstuffs. Except in the case of the manufacture of fruit juices and pickles, process plant failure through corrosion must be rare. Nevertheless all foodstuffs, particularly liquid ones, should be regarded as potentially corrosive and capable of metal pick-up which may be undesirable. 

Experiments in relatively permeable aquifers (i.e., sand) indicate that between 6 and 10 pore volume flushes with clean water will reduce the highly soluble, nonatten-uated salt contamination to a relatively acceptable concentration. This is usually an effective approach because the secondary drinking water standard for chloride is a relatively high value of 250 ppm. This concentration was established because it is the threshold, where one can taste the salt, not because the salt is a hazardous substance. 

Colorless gas characteristic odor of rotten eggs odor threshold Ippm sweetish taste fumes in air flammable gas, bums with a pale blue flame refractive index at 589.3nm, 1.000644 at 0°C and 1 atm density 1.539 g/L at 0°C critical temperature 100.4°C critical pressure 88.9 atm liquefies at -60.7°C solidifies at -85.5°C velocity of sound 289 m/sec in H2S gas slightly soluble in water (0.4% at 20° C) pH of a saturated aqueous solution 4.5 slightly acidic diffusivity in water at 16°C, 1.77x10 cm /sec soluble in carbon disulfide, methanol, acetone very soluble in N-methylpyrrolidinone and alka-nolamines (salt formation occurs salt dissociates on heating) liquid H2S dissolves sulfur and SO2. 

Ottinger el al.2S6 have applied their comparative taste dilution analysis (cTDA) to examine the extractable products from heated aqueous D-glucose and L-alanine that were not solvent-extractable. One HPLC fraction proved to be a strong sweetness enhancer. It was isolated and submitted to LC-MS and NMR, both ID and 2D the results, together with its synthesis from HMF and alanine, unequivocally identified it as the inner salt of /V-( I -carboxycthyl)-6-(hydroxy-methyl)pyridinium-3-ol (alapyridaine, Structure 45). It has no taste on its own, which in many applications would be an advantage. Depending on the pH, it lowers the detection threshold of sweet sugars, amino acids, and aspartame, the... 

Since these compounds are mostly used as weapons or poisons, the bitter taste is generally not a problem in their use so, with few exceptions, it has seldom been studied systematically. One exception is strychnine, which is used as a potent rodenticide and for which the bitter taste is a limitation since it prevents ingestion by the animals. Some studies on the bitter taste of this alkaloid have been done with the aim of masking the taste of strychnine [48]. The threshold for the detection of strychnine in distilled water is 5.4 p,g, in tap water 6.5 p,g. Various substances were added to diluted solutions of strychnine to ascertain whether the bitter taste could be masked. It was masked to some extent by certain salts, sucrose, and extracts of yerba Santa. It was also noticed that the cation was the significant factor in the masking... 

A series of increasing concentrations of a chemically pure stimulus material in a neutral substrate (water or oil) may be used to determine sensory thresholds to those compounds. The assessors have to indicate the concentration at which stimulus is perceived for two successive concentrations. Increasing concentrations of sucrose, sodium chloride, citric acid, and caffeine are used for the basic tastes sweet, salt, acid, and bitter. Likewise, the olfactory threshold is determined by using some odorants in aqueous or alcoholic solutions (absolute ethanol is often used as a solvent), to measure the ability of the panelists to identify an odor impression and evaluate their odor memory. 

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