Nucleotides, taste enhancers

Salt is the best known taste enhancer for a variety of foods. Monosodium glutamate (MSG) and nucleotides, such as inosine monophosphate (IMP) and guanosine monophosphate (GMP), are known to enhance flavor and are recognia as the "umami taste" in Oriental cuisine. They have longer aftertastes than the "basic... 

By market volume the most important flavour molecule is L-glutamic acid. In 2004, the worldwide annual MSG production was estimated to be amount 1,500,0001 [21]. The amino acid is extensively used as taste enhancer, frequently in conjunction with nucleotides, a flavour impression which is also referred to as umamf, a term derived from the Japanese meaning deliciousness or a savoury or palatable taste. MSG is manufactured by aerobic cultivation of Coryne-bacterium glutamicum on starch hydrolysates or molasses media in large-scale bioreactors (up to 500 m ). Production strains with modified metabolic flux profiles and highly permeable cell walls for an improved product secretion are... 

The chemical structure of the nucleotides is shown in Figure 7-21. They are purine ribonucleotides with a hydroxyl group on carbon 6 of the purine ring and a phosphate ester group on the 5 -carbon of the ribose. Nucleotides with the ester group at the 2 or 3 position are tasteless. When the ester group is removed by the action of phos-phomonoesterases, the taste activity is lost. It is important to inactivate such enzymes in foods before adding 5 -nucleotide flavor enhancers. 

For the composition of vegetable flavourings it is essential to distinguish the flavour from the taste part this taste is a balanced composition of harsh, slight bitter acids with salt, some taste enhancers (nucleotides) and sugar to impart a slight sweetness. 

POTENTIATOR. A term used in the flavor and food industries to characterize a substance that intensifies the taste of a food product to a far greater extent than does an enhancer. The most important of these are the 5 -nucleotides. They are approved by the FDA. Their effective concentration is measured in parts per billion, whereas that of an enhancer such as MSG is m parts per thousand. The effect is thought to be due to synergism, Potentiators do not add any taste of their own, but intensify7 the taste response to substances already present in the food. 

Some 51-nucleotides have been implicated as flavor modifiers, and orange juice is known to contain relatively large quantities of certain 5 -nucleotides, with a total level of about 40 ppm (25, 26). In a study of the influence of six 5 -nucleotides at the 10 ppm level on the taste threshold of octanal in water (Table II), two of the 5 -nucleotides (GMP and ADP) significantly lowered the threshold of octanal (23). GMP is known to enhance flavor in foods, but ADP had been reported to have little or no modifying effect on food flavors (23). Analysis of variance showed that GMP, ADP and GDP enhanced the flavor of octanal in aqueous... 

Taste compounds and flavour enhancers are raw materials used in process flavourings and can also be added to the final product. Current examples are sodium and potassium salts, organic acids, monosodium glutamate (MSG) and the 5 -nucleotides 5 -inosine monophosphate (IMP) and 5 -guanosin monophosphate (GMP). 

Like MSG, salt has a generally unfavorable status with the consumer. Salt is associated with hypertension in some individuals, which contributes to stroke and some types of cardiovascular disease. There has been substantial research effort directed at finding salt substitutes, but other than K+ chloride, little has been found that elicits a true salty taste. Unfortunately, K+ is bitter and thus not well received. Some research has shown that the addition of MSG and/or 5 -nucleotides reduces the need for salt. There are other reports of L-lysine and L-arginine [39], L-omithine-P-alanine [40,41], and trehalose [42] enhancing salt perception (thereby reducing usage level). 

Lipid oxidation products and their reaction products with amino acids (proteins) have a considerable influence on the typical odour and taste of meat. Particularly significant aminocarboxylic acids include glutamic acid, alanine, threonine and lysine, guanidine compounds (creatine and creatinine), quaternary ammonium compounds (choline and carnitine), peptides (P-alanylhistidine peptides and some products of proteolysis), free nucleotides, nucleosides and their bases (especially inosine 5 -monophosphate, IMP), proteins, carboxylic acids (especially lactic acid), sugars (mainly glucose, fructose and their phosphates, ribose formed by hydrolysis of free nucleotides) and some vitamins (especially thiamine). Some of these compounds, such as glutamic acid and IMP, are additionally used as food additives, namely as flavour enhancers. 

The organoleptic properties of food are one of the characteristics that define food quality and govern food selection. Between the food additives that are added to increase its taste and palatability, free L-glutamic acid, as its sodium salt monosodium glutamate (MSG), imparts an intrinsic taste of its own, termed umami, the fifth taste. Umamt means delicious in Japanese, and it is attributed to the sensory properties of MSG and some nucleotides, such as sodium 5 -inosinate (IMP) and sodium 5 -guanyl-ate (GMP). MSG enhances the flavor of certain foods such as meat, poultry, seafood, and vegetables. 

Inosine monophosphate and GMP are synthesized in the human body and play diverse roles in cellular metabolism [3]. Dietary nucleotides are energetically useful to fulfill the liver s need for nucleotides [4], although people with high levels of uric acid (UA) in their blood and urine must avoid foods with these compounds, because degradation of purine nucleotides leads to the formation of UA [3]. In addition, these flavor enhancers are added by food manufacturers to improve the taste of food. Therefore, monitoring these compounds in foods or food seasonings is very important in food-quality or foodprocessing control. 

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