September 1, 2003
Alternatives to sugar are gaining a higher profile as bulking sweeteners mix formulator functionality with nutritional benefits that go far beyond the traditional sucrose. Michael G. Lindley, PhD, reports
Sucrose in the pure state—sugar—is produced more widely and normally at a lower price than any other pure chemical substance in the world.1 It is a broadly useful food ingredient, delivering a range of important physical functionalities to a wide range of everyday foods and beverages. It delivers a taste generally described as high-quality sweetness, and this taste influences the palatability of many foods and drinks in which it is formulated.2
However, and not without paradox, sucrose is the subject of much criticism on health grounds. In fact, the commercialisation of food ingredients that substitute for sucrose by delivering key functionalities lost with its removal from foods and drinks has been a primary focus of research and development activity for food-ingredients supplier companies for years. Such activities receive additional impetus when they conform to dietary guidelines that recommend, along with other proposals, that individuals should seek to maintain a healthy weight and should moderate sugar intake.
Alternatives to sucrose have been an integral part of Western diets for very many years. Corn syrups prepared by the acid hydrolysis of starch began to be produced in the middle of the 19th century, and the high-potency sweetener saccharin became a commercial sugar substitute during the mid-1880s. Interestingly, the key driver for commercialisation of these alternatives to sugar was not nutrition but their individual abilities to replace some of the functionalities of sucrose at a reduced cost-in-use.
Many recent sugar-replacer ingredient developments are also of high-potency sweeteners. These are essentially mono-functional ingredients capable of delivering only sweetness; they do not provide any of the textural or bulking properties of sugar. Although their application in foods and drinks confers sweetness without calories, they do not provide any intrinsic nutritional benefits. It is a case of addition by subtraction—removing sugar may lead to a real or perceived nutritional benefit, not the consumption of the high-potency sweetener itself.
To exemplify the scale of the problem with sucrose and nutritive sweeteners derived from starch (sugar), in the United States the annual per capita consumption of caloric sweeteners has risen by 20 per cent since 1970, and per person consumption of sugars now averages 500 calories/day, as opposed to a recommended maximum of 200 calories/day.3 In other words, we are consuming more caloric sweeteners than is good for us.
Today, however, alternative ingredients to sugar are being developed and commercialised on the grounds of the positive health and nutrition benefits they can confer in addition to the physical functionalities they can contribute for food technologists.
Sugar Alcohols Or Polyols
Sugar alcohols have been part of the food supply for many years, and may be categorised as 'old' ingredients. They include sorbitol, mannitol and isomalt. Most food applications for these ingredients are found in hard candy, pressed mints and chewing gum that are marketed as 'sugar free.' In other words, although these sugar alcohols will not contribute to the development of dental caries, and in many instances are reduced in calories (in common with high-potency sweeteners), a major rationale for their inclusion in foods is that they are 'not sugar.'
Xylitol is one sugar alcohol whose use may be accompanied by positive health benefits. Its caloric delivery is accepted by the US Food and Drug Administration (FDA) to be 2.4kcal/g (compared to sucrose at 4kcal/g), but a more interesting aspect of xylitol concerns the positive effect that it has on oral health. In both clinical and field studies, consuming xylitol between meals has been correlated directly with significantly reduced formation of new dental caries, even when participants are already practising good oral hygiene.4
Erythritol is the newest commercially available sugar alcohol. This is a four-carbon polyol and delivers the lowest energy of all the sugar alcohols (0.2kcal/g). Unlike other sugar alcohols that pass into the large intestine where they are fermented, erythritol is largely absorbed and then excreted via the kidneys. It is this different metabolic route that explains the low-energy delivery of erythritol. Therefore, with its high solubility, sweetness intensity similar to glucose (dextrose) and low calorie delivery, erythritol should in theory function as a broadly versatile bulking agent replacer of sugar.5 In practice, of course, things are not quite as straightforward as might be anticipated, largely because of the extreme cooling sensation imparted when erythritol crystals dissolve in the mouth. Thus, it is not obviously suitable for use in applications such as cookies and chocolate, although blends of erythritol and inulin have been formulated successfully and are used commercially in sugar-free chocolate.
In summary, erythritol may be considered to be the bulk equivalent of a high-potency sweetener in that it provides physical and sensory functionalities to foods and beverages with minimal caloric delivery. In this way, it can become an important contributor to the preparation of sugar-free, low- and reduced-calorie foods, although, in common with the potent sweeteners, its use will not confer intrinsic health benefits.
A number of new, small-molecular-weight carbohydrates have been commercialised recently, including tagatose and trehalose. In contrast to the sugar alcohol examples already discussed, these sugars can deliver some positive nutritional benefits, so their use in foods may be for more than being able to market products as 'sugar-free.'
Tagatose is a structural isomer of fructose and is prepared from lactose-derived galactose by alkaline isomerisation. The structural difference from fructose means that tagatose is not metabolised using the routes whereby fructose is handled. A small amount (15 to 20 per cent) of ingested tagatose is absorbed, but the major portion (80 to 85 per cent) of ingested tagatose passes into the colon where it is fermented. During fermentation, tagatose stimulates the growth of lactic acid bacteria and lactobacilli and promotes the production of butyrate in the colon. 6 Thus, it closely conforms to the definition of a prebiotic. 7 As a consequence of this metabolic route, tagatose is also suitable for use in foods prepared specifically for diabetics. 8
In addition to its prebiotic status, tagatose delivers only 1.5kcal/g while providing about 92 per cent of the sweetness of sucrose. Also, its non-cariogenic status has been demonstrated in appropriate plaque pH telemetry evaluations.6 Thus, it has the capacity to function as a low-calorie bulking agent for broad application in foods, while offering specific benefits in confectionery and dairy products.
Trehalose has recently been commercialised in a range of important markets, including the US, Japan and Europe. Trehalose is a glucose-glucose disaccharide (sucrose is a fructose-glucose disaccharide) bound in an a, a-1, 1 linkage. It is non-reducing and found naturally in a number of foods including mushrooms, shellfish and yeast. In contrast to the other sugar replacers discussed in this article, it is not a reduced-calorie sugar, being hydrolysed by an intestinal trehalase enzyme that releases glucose into the small intestine.9 Nonetheless, trehalose has a number of potentially valuable features. It protects and preserves cell structure in foods and has a remarkable protective effect on protein molecules, which otherwise may be dehydrated through drying or freezing processes. Target applications for trehalose include beverages, nutrition bars, surimi, and dehydrated fruits and vegetables.
Polydextrose, the low-calorie bulking agent, also deserves mention. This, of course, is far from being a new ingredient, having first received mention almost 30 years ago10 and FDA approval in 1981,11 but its marketing continues to develop and evolve as more information accumulates on its nutritional benefits. In fact, polydextrose was initially considered mainly as a reduced-calorie substitute for sugar. Although it was (and still is) used for this characteristic, markets for it have expanded greatly as acceptance of its soluble fibre designation and prebiotic nature have become widespread.
Polydextrose, a random polymer of glucose and sorbitol whose formation is catalysed by acid, delivers 1kcal/g. It has been formulated successfully into a broad range of food and drink applications, in which it is used for one or more of the following nutritional benefits: its low-caloric delivery, its soluble dietary fibre status and its prebiotic character. This latter nutritional functionality has received due attention in recent years, with polydextrose having been demonstrated to produce butyrate during cooling fermentation throughout the length of the colon. Key applications for polydextrose include confectionery, baked goods, beverages and dairy products.
Better Than Sugar
For years, dietary guidelines of many national governments have recommended that individuals should moderate their sugar consumption. In some important market sectors, particularly beverages, such guidelines can be followed through the use of mono-functional potent sweeteners. However, it is not possible to select potent sweeteners for many other food applications when the bulk delivered by sugar must be replaced by another bulk ingredient. This factor has stimulated the development of a number of current sugar replacer ingredients.
Today, a growing range of these ingredients is available for use by food and beverage manufacturers. Importantly, many not only are proving capable of replacing sugar in the preparation of 'sugar-free' versions of mainstream products, but they also deliver additional functional and nutritional benefits, including prebiotic status, glycemic control and soluble fibre definition. This growing understanding of the important positive nutritional benefits that can be conferred is likely to drive the development of the markets for these sugar replacers in the years to come.
Michael G Lindley, PhD, is director of LinTech, a technical consultancy specialising in supporting the development of new functional foods ingredients and the foods and beverages in which they are formulated. He has 30 years of experience providing scientific and technical support to food companies worldwide. [email protected]
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11. 21 CFR 172.841, 46 FR 30080 (June 5, 1981), Food Additive Petition 9A3441.
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