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Flavor attributes

Figure 1. FPA of sodium saccharin (384 ppm) and sodium cyclamate (5930 ppm) in water.

These temporal effects combine to cause neohesperidin dihydrochalcone to be a substantially less acceptable sweetener than sucrose in most food systems. Thus, it is not sufficient to know only a sweetener's flavor profile to predict viability. The temporal profile must also be known. Ultimately, of course, the taste quality of a sweetener may be appreciated only after consumer acceptability studies in the food category of interest.

Safety

In the United States, the use of sweeteners is regulated by the 1958 Food Additives Amendment to the Food, Drug and Cosmetic Act of 1938. This legislation and its effects on the regulation of sweeteners and other food additives has been reviewed (9,10). By this act, saccharin and cycla-mates were exempted as generally recognized as safe (GRAS) food ingredients. Not all sweeteners are included on the GRAS list, however, which in its original form, listed 675 food ingredients. Surprisingly, even sucrose is not included. However, the omission of sucrose and many other obviously safe food ingredients prompted the following official FDA comment:

It is impractical to list all substances that are generally recognized as safe for their intended use. However, by way of illustration, the Commissioner regards such common food ingredients as salt, pepper, sugar, vinegar, baking powder and monosodium glutamates as safe for their intended use. (11)

In order to achieve GRAS status, a sweetener or any food ingredient may be generally recognized as safe among

. . . experts qualified by scientific training and experience to evaluate the safety of substances directly or indirectly added to food. The basis of such views may be either (2) scientific procedures or (2) in the case of a substance used in food prior to January 1, 1958, through experience based on common use in food. (12)

For the cases of substances not included on the GRAS list, two tracks toward approval for use in foods are defined. First, and somewhat simpler where applicable, is the GRAS Affirmation Process. To qualify for this track, it must be either (2) demonstrated that the substance was in common use in food in the United States prior to 1958 or (2) be based on expert judgment of safety demonstrated by published safety studies. If the available safety data are not sufficient to support the requested uses or increase in projected exposure levels, the FDA may affirm GRAS status but limit levels of use until further safety data are established. Examples of sweeteners for which GRAS affirmation has been requested are discussed in the latter part of this article.

The second track toward approval of a sweetener for use in foods is the food additive petition (FAP) process. The FAP process requires extensive safety studies in test animals as well as studies in humans. One objective of these studies is the determination of the highest dose that may be given without adverse effects. This dose is termed the no observed adverse effect level (NOAEL). The NOAEL, in the most sensitive animal species evaluated, is then used by the FDA to regulate the level at which the food additive may be used in foods. This level, termed the acceptable daily intake (ADI), is defined as 0.01 of the NOAEL in the most sensitive animal species. These NOAEL and ADI exposure levels are given in milligrams per kilogram of body weight. Thus, as an example, if the NOAEL of a proposed new sweetener is determined to be 500 mg/kg in the most sensitive animal species evaluated, an ADI of 5 mg/kg would be allowed. The question then naturally arises as to the meaning of a 5 mg/kg ADI allowance. This level is then employed by the FDA to determine the food categories and levels in those categories in which the new sweetener may be used. The objective of this exercise is to ensure that the 5 mg/kg exposure level is not exceeded on a chronic basis. In order to do this, 90th percentile, 14-day average food category consumption data are employed. Approval of the new sweetener may then be granted for use in food categories where, in the aggregate, 90th percentile, 14-day average consumption data on these categories does not exceed the ADI. Examples of sweeteners that have successfully undergone, or are currently undergoing the FAP Process, are discussed in this article. Marshall and Pollard have comprehensively reviewed the category and level approvals that have been granted in the United States and abroad for many of the sweeteners discussed herein (13). Broulik reviewed the regulatory issues related to new sweetener development in the United States in 1996 (14).

Although individual countries assume responsibility for the regulation of food additives within their boundaries, there has been an attempt at international standardization of food additive regulation. Vettorazzi reviewed this process in 1989 (15). In 1956, the Food and Agriculture

Organization of the United Nations (FAO) and the World Health Organization (WHO) established the Joint FAO/ WHO Expert Committee on Food Additives (JECFA). The fundamental objective of JECFA is the establishment of ADIs for food additives following the assembly and interpretation of all relevant biological and toxicological data. It is important to recognize that ADIs provide a wide margin of safety. According to JECFA, "an ADI provides a sufficiently large safety margin to ensure that there need be no undue concern about occasionally exceeding it provided the average intake over longer periods of time does not exceed it" (16). Over its lifetime, more than 700 intentional food additives have been evaluated by JECFA.

Solubility

Many sweeteners are insufficiently water soluble to be of general utility. Commonly, sweetness intensity levels at least equivalent to 10% sucrose are required. In some systems (eg, frozen desserts), soluble sweetener levels are required that match the sweetness of 15 to 20% sucrose. In addition, for many food systems, manufacturers may require that sweeteners dissolve sufficiently rapidly so as to not interfere with current manufacturing processes. A particularly relevant illustration of requirements imposed by manufacturing processes is that for CSD products. In this case, it is necessary that a concentrate solution of the sweetener-flavor system complex be rapidly attainable. Thus, high solubility and rapid dissolution rates are very desirable properties for nonnutritive sweeteners.

Stability

Tb be commercially viable, a sweetener must be stable to the intended conditions of use. Degradation may be from hydrolytic, pyrolytic, or photochemical processes depending on the food application. Stability is required for two reasons. First, the sweetener must not degrade such that the level of sweetness of the food product would be substantially reduced during the product lifetime. Also, the sweetener must not break down to cause any off taste. The second reason for the stability requirement relates to sweeteners that are defined as food additives. By the FAP process, degradation products must be shown to be safe. Currently, for most organic compounds, if exposure to the degradation product may reach or exceed 0.0063 mg/kg, then the requisite safety assessment studies would be equal to those mandated for the sweetener itself (17). As such, a sweetener's stability is a very important factor when assessing its viability for development as a new food additive.

Cost

Nonnutritive sweeteners are always compared to sucrose, the consumer's standard. With sucrose in plentiful supply, presently at 36 cents/lb, potential replacements must either be cost-competitive or present sufficient advantages to justify a premium (18). The effective cost to the food product manufacturer of an alternative sweetener is equivalent to the wholesale price divided by the potency of the alternate product in delivering the desired property. In most cases, the desired property is sweet taste intensity. Thus, the effective cost or cost per sucrose equivalent (CSE) is the quotient of wholesale price and sweetness potency (P). P is generally expressed as a multiple of the P of sucrose, which we define to be 1. Although sometimes P is expressed on a molar basis, most commonly P is expressed on a weight basis (Pw). It is important to recognize that although Pw is not constant for high-potency sweeteners, it often is for sugars and other polyol sweeteners of low potency (19). Pw for a high-potency sweetener varies according to the sucrose reference concentration. Concentration/response (C/R) functions demonstrating saccharin's and cyclamate's nonlinear dependencies of Pw on sucrose reference concentration are illustrated in Figure 2. DuBois et al. demonstrated that the law of mass action hyperbolic function R = RmC/(kd + C) provides a good fit for high-potency sweetener C/R function data and that the simple linear function R = PWC + b provides a good fit for most sugar and polyol sweetener C/R function data (20). When sweetener C/R data are fit to these equations, the constant terms provide very useful information. If a sweetener's C/R data are well modeled by R = P„C + b, then Pw for the sweetener is a constant and is determined to be the slope of the line. On the other hand, if a sweetener's C/R data are well modeled by R = RmC/(kd + C), then Pw is not a constant and is dependent on sucrose reference concentration. It is important to note, however, that the parameters Rm (maximal response) and kd (apparent sweetener/receptor dissociation constant) in this equation

Saccharin C/R function

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