Sugars relative sweetness, differences

The hypothesis could also account for differences in the relative sweetness of sugars by simple consideration of the way in which configurational differences might affect hydrogen bonding. The sweetness of D-galactose... 

Cameron (S) and others (5, page 48) have found that sweetness is not a linear function of concentration, and that the relative sweetness of different sugars varies with the concentrations at which they are compared. Sweetness is influenced by temperature, pH, and the presence of other substances which need not themselves be sweeteners. For example, a 5% sucrose solution containing 2% urea was found to be equal in sweetness to a 3.1% sucrose solution. Thus, sweetness had been reduced 38% by the presence of urea. 

Though these difficulties must be kept in mind, the quality of bakery products must be controlled, and bakers are prone to flirt with a single numerical score of quality. Doing this, they are also impressed with similar scores of the sweetness of different sugars. Such scores of relative sweetness, with sucrose arbitrarily assigned the value 100, are shown in Table II. 

For a molecule to taste sweet, it must bind to a receptor on a taste bud cell of the tongue. The binding of this molecule causes a nerve impulse to pass from the taste bud to the brain, where the molecule is interpreted as being sweet. Sugars differ in their degree of sweetness. The relative sweetness of glucose is 1.00, that of sucrose is 1.45, and that of fmctose, the sweetest of all sugars, is 1.65. Developers of synthetic sweeteners must consider several factors—such as toxicity, stability, and cost—in addition to taste. 

Although different sugars have different sweetness factors relative to sucrose they are all identical in energy content, on a dry basis. Thus to achieve a high energy content without cloying sweetness, sugars or carbohydrates of low sweetness must be used. This is illustrated in Table 13.2. 

Do these diverse compounds give rise to a common perception of sweetness or to qualitatively different sensations Sweetness does indeed appear to be a unitary percept (Breslin et al. 1994,1996). However, some sweeteners may be discriminable on the basis of their activation of other sensory transduction mechanisms or differences in the temporal properties of their sensory action. For example, the sweetener sodium saccharin activates bitter receptors in some people (Kuhn et al. 2004 Pronin et al. 2007), and also inhibits sweet taste at high concentrations (Galindo-Cuspinera et al. 2006). Sweet proteins such as thaumatin and monellin can have a slow onset or evoke a prolonged sweetness compared with sugars (Faus 2000), likely owing to a relatively high affinity for the sweet taste receptor. 

Xylitol is obtained by hydrogenation of the pentose sugar xylose. It is as sweet as sucrose, and new relatively inexpensive methods have been devised for its production. Xylulose occurs naturally on the pathway by which breakdown products of gluconic acid (page 232) are fed into the pentose phosphate shunt. When administered, xylitol is readily metabolized but differs from glucose in the initial steps prior to the point at which it enters the glycolytic pathway. 

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