Taste, acid bitter

The enzymatic hydrolysates of milk casein and soy protein sometimes have a strong bitter taste. The bitter taste is frequently developed by pepsin [9001 -75-6] chymotrypsin [9004-07-3] and some neutral proteases and accounted for by the existence of peptides that have a hydrophobic amino acid in the carboxyhc terminal (226). The relation between bitter taste and amino acid constitution has been discussed (227). 

Benzoyl-e-aminocaproic acid-bitter compound mixtures, tasting behavior, 33,34f... 

Figure 9(a) shows the response patterns to typical amino acids, each of which elicits different taste quality in humans [23]. Each channel responded to them in different ways depending on their tastes. L-Tryptophan, which elicits almost pure bitter taste, increased the potentials of channels 1, 2 and 3 greatly. This tendency was also observed for other amino acids which mainly exhibit bitter taste L-phenylalanine and L-isoleucine. L-Valine and L-methionine, which taste mainly bitter and slightly sweet, decreased the potential of channel 5 the responses of channels 1 and 2 were small. 

A white or almost white, crystalline powder, platelets or thick birefringent rods (from alcohol + acetone) odorless, with a slightly bitter saline taste, acid. 

Wine is one of the most complex and interesting matrices for a number of reasons. It is composed of volatile compounds, some of them responsible for the odor, and nonvolatile compounds which cause taste sensations, such as sweetness (sugars), sourness (organic acids), bitterness (polyphenols), and saltiness (mineral substances Rapp and Mandary, 1986). With a few exceptions, those compounds need to be present in levels of 1%, or even more, to influence taste. Generally, the volatile components can be perceived in much lower concentrations, since our organs are extremely sensitive to certain aroma substances (Rapp et ah, 1986). Carbohydrates (monosaccharides, disaccharides, and polysaccharides), peptides, proteins, vitamins, and mineral substances are among the other wine constituents. 

As mentioned previously, acids and bases can be defined in a number of ways. One way to define an acid or base is by what you see when an acid or base reacts with other substances. For example, your senses can help you identify an acid or base because acids taste sour and bases taste bitter. The sour taste of lemons can be attributed to the citric acid found in the lemon juice. In addition, bases have a slippery feel to them (please, do not touch or taste acids or bases). 

Properties The monohydrate crystallizes in plates from dilute acetic acid. Bitter taste with sweetish aftertaste. Anhydrous form. Mp 198C. Not precipitated by digitonin. Soluble in glacial acetic acid, acetone, and alcohol slightly soluble in chloroform practically insoluble in water and benzene. 

Properties Crystals from alcohol or acetic acid sweet taste with bitter aftertaste. Mp 132C (decomposes). 

It is a yellow or light-brown syrup, which cannot be dried without decomposition, bitter and disagreeable to the taste, acid in reaction, and soluble in water, alcohol, and ether. 

To Biatinguisb. Oxalic Acid from Epsom Salts. Oxalic acid has occasionally been mistaken for Epsom salts, with fatal results. They may be easily distinguished. Epsom salts taste extremely bitter and mme its oxalic acid tastes extremely sour. It is safer to taste a wea solution in apply-... 

Dihydrate, yellow needles from dil alcohol. Becomes anhydr at 95-97. When anhydr dec 314. uv max (ale) 258. 37S nm (log 2.75, 2.75). One gram dissolves in 290 ml abs ale, in 23 ml boiling ale. Soluble in glacial acetic acid in aq alkaline solns with yellow color. Practically insol in water. Alcoholic solns taste very bitter. LDW orally in mice 160mg/kg (Sullivan). 

The parent compound of the secoiridoids is secologa-nin (see secoiridoids), the most important intermediate in the biogenesis of alkaloids that are not derived from an amino acid. This includes most indole alkaloids, the ipecac, the Cinchona, and the pyrroloquinoline alkaloids as well as simple monoterpene alkaloids The best known biological property of the I. is their bitter taste. However, bitter principles are mostly not used as pure substances, instead alcoholic extracts are preferred to stimulate appetite (increased secretion of gastric juice). Furthermore, bitter substances are used to modify the taste of pharmaceutical products. Some I. exert various effects on the central nervous system as a consequence of their volatility and lipophilicity, e.g., nepetalactone, iridodial, teucrium lactones, and valepotriates. 

Under the action of phenylalanine ammonia lyase (EC 4.3.1.5) Phe is transformed to rrans- cinnamic acid. This plays an important role in plants as a precursor of numerous phenolic secondary products such as flav-onoids, lignin, etc. D-Phe is a component of grami-cidin S and tyrocidines. L-Phe tastes weakly bitter, D-Phe tastes sweet. 

The properties of acidic solutions are quite different from those of basic solutions. Acids have a sour taste, whereas bases have a bitter taste. Acids change the colors of certain dyes in a way that differs from the way bases affect the same dyes. This is the principle behind the indicator known as litmus paper ( FIGURE 4.8). In addition, acidic and basic solutions differ in chemical properties in several other important ways that we explore in this chapter and in later chapters. 

In human nutrition, free amino acids play an important role in aromatisa-tion, as flavour enhancers, and as sweeteners. Monosodium glutamate, in concentrations of 0.1-0.4%, is probably the most prominent flavour enhancer for spices, soups, sauces, meat and fish. (L)-Cysteine amplifies the flavour of onions. Glycine is used to mask the aftertaste of saccharin. Whereas (L)-amino acids may taste slightly bitter, the (D)-enantiomers have a sweet taste. This is in general also true for the corresponding di- and oligopeptides - except for the methyl ester of (L)-aspartyl-(L)-phenylalanine (Aspartame). 

Texture smoothness/thickness/stickiness Taste sweetness/acidity/bitterness Aroma global dairy notes/acetic acid/cheesy aroma... 

PMTh-, PANI-, aud PPy-modified electrodes includiug different anions Standard solutions Discrimination between soluticms containing chemical species representative of different tastes sweet, bitter, acid, salty, and astringcmt PCA [130]... 

Bases have a bitter taste. There are very few foods that are basic, but those that are, such as baking soda, taste bitter rather than sour. Do not taste a substance to see if it is a base unless your teacher or a lab chemist tells you that it is safe. Tasting bases can be even more dangerous than tasting acids because of the damage a base could do to the proteins on your tongue and in your mouth. 

Like acids, bases can be identified by their properties. When washing your hands with soap, you experience one of the properties of bases, their slippery feel. Soap is basic and, like all bases, feels slippery on the skin. If you have ever tasted soap, you know another property of bases, their bitter taste. The bitter taste of coffee, milk of magnesia, and some medicines is due to their base content. 

Elimination of the bitter taste from a protein hydrolysate is also possible without incorporation of hydrophihc amino acids. Bitter-tasting peptides, such as Leu-Phe, which are released by partial hydrolysis of protein, react preferentially in the subsequent plastein reaction and are incorporated into higher molecular weight peptides with a neutral taste. 

The coated can is filled with a bottled or draught lager beer, left to stand, and then compared against a standard. Points of reference are changes in acidity, bitterness, and any metallic flavour compared to the standard. A trained and skilled flavour (taste) panel is normally used to assess this property. 

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