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The mathematics of replacing sugar.

Sucrose is the standard sweetener to which all other sweeteners are compared. The relative sweetness of sucrose is set to one or 100 per cent. The only way to measure the sweetness of a substance is to taste it. When it is placed on the tongue, the taste buds decipher the chemical configuration and a signal of the taste is sent to the brain. Bulk sweeteners can be classified into sucrose (sugar), non-sucrose sweeteners (glucose, fructose, maltose, lactose, trehalose, isomaltulose, oligofructose) and sugar alcohols (xylitol, sorbitol, maltitol, isomalt, erythritol), to name just a few.

Glucose is always less sweet than sucrose (74 per cent), whereas the sweetness of fructose is higher (173 per cent) dependent on temperature (sweeter than sucrose at low temperatures, whereas the sweetening effect decreases as the temperature rises). A growing number of alternative sweeteners exist on the market; all with different sweetness compared to sucrose. The sweetness of many sweeteners depends on concentration, pH, temperature and the use of other ingredients. Psychological effects can also influence the taste sensation: green jelly is perceived as less sweet than red jelly, although they contain exactly the same amount of sweetener.

Oligofructose and isomaltulose are two unique non-sucrose sweeteners that are not typically associated with sugar replacements. The differences are:

Oligofructose is extracted from chicory roots. It is not digested in the stomach or small intestine and reaches the large intestine intact. It is selectively fermented by the intestinal flora, acting as a prebiotic. The sweetness level compares 30 per cent to that of sucrose and works synergistically with high intensity sweeteners as it masks bitter notes to produce a rounded sweetness profile (see fig. 3). Popular applications are sugar reduced fruit preparations, nutritional powders, bars, cereals, and baked goods.

Isomaltulose is commercially produced from food-grade sucrose by enzymatic rearrangement, resulting in the new molecular linkage, which is a lot more stable compared to sucrose. It is the only non-sucrose nutritive sweetener that is fully digestible yet slowly absorbed in the small intestine resulting in balanced blood sugar levels. It compares 50 per cent in sweetness to sucrose and, although it has the same energy value as sugar, its the ideal choice for diabetic- and sustainable energy products.

Defining bulk sweeteners (USE H4 HEADER OR WHATEVER MAKES SENSE AND LOOKS NICE)

Sugar alcohols are also called polyols and are chemical derivatives of sugars that differ from the parent compounds in having an alcohol group (CH 2 OH) instead of the aldehyde group (CHO); thus xylitol from xylose and maltitol from maltose.

Sugar alcohols occur naturally in a wide variety of fruits and vegetables, but are commercially produced from other carbohydrates such as sucrose, glucose, and starch. There are many different polyols available today, but all except one is less sweet than sucrose. The relative sweetness of polyols appears from figure 1. All polyols have a more or less pronounced cooling effect due to negative heat solubility, which may add value to some products but cause problems in others.

Along with adding a sweet taste, polyols perform a variety of functions such as adding bulk and texture, inhibiting the browning that occurs during heating and retaining moisture in foods.

Fig. 1 Relative sweetness of selective sugar alcohols (polyols)

Sugar alcohols are slowly and incompletely absorbed from the small intestine into the blood. Once absorbed they are converted to energy by processes that require little or no insulin, which is well tolerated by diabetics. Some of the sugar alcohol is not absorbed into the blood. These pass through the small intestine and are fermented by bacteria in the large intestine. Overconsumption may produce abdominal gas and discomfort in some individuals. Total daily consumption should be considered since it is the total intake that may primarily drive gastro intestinal disturbance or laxative effects. As a result, foods that contain certain sugar alcohols and that are likely to be eaten in amounts that could produce such an effect must bear the statement: Excess consumption may have a laxative effect.

Isomalt is a polyol manufactured in a two-stage process in which sugar is first transformed into isomaltulose and then hydrogenated to isomalt. It is 50 per cent as sweet as sucrose and doesnt produce an aftertaste or cooling effect. The greatest technological advantage of isomalt is its low hygroscopicity absorbing virtually no moisture at a temperature of 25C and relative humidities up to 85 per cent, resulting in highly stable products during storage. Isomalt is a popular choice for use in sugar free confectionery products i.e. hardboiled candy, chewing gum, soft chew candy and chocolate as well as sugar reduced or sugar free bakery products. Isomalt is considered tooth friendly.

Xylitol is considered to be a natural polyol, but depends on the manufacturing process. Xylitol is naturally found in low concentrations in thefibres of manyfruits andvegetables, and can be extracted from variousberries, oats, andmushrooms, as well as fibrous material such ascorn husks and birch. However, industrial production starts fromxylan(ahemicellulose) extracted from hardwoodsor corncobs, which is hydrolysed intoxylose and catalytically hydrogenated into xylitol. It is the only polyol that matches the sweetness level of sucrose with 33 per cent fewer calories, making it ideal for use as a table top sweetener or in sugar free bakery and cereal products. Xylitol gives a cooling effect and is considered tooth friendly.

Erythritol is a natural occurring sugar alcohol and found in foods such as wine, melons and honey. It is produced by ayeast-based fermentation process commercially. The sweetness level is 70 per cent compared to that of sucrose. Due to its molecular structure, it doesnt undergo fermentation by human gut flora and doesnt cause digestive stress. Erythritol can be effectively combined with a high intensity sweetener such as stevia to obtain the desired sweetness level making table top sweeteners a popular application.

Sorbitol / maltitol are both syrups with 50 per cent and 90 per cent the sweetness level of sucrose. Its humectant properties make it ideally suitable for binding syrups in bars in cereal clusters.

Unpacking high intensity sweeteners

High intensity sweeteners (HIS) are what the name implies; sweeteners with an intense sweetness level much higher than that of sucrose. The relative sweetness of all HIS products is highly dependent on concentration and pH. Stevia, sucralose and aspartame are all well-known HIS. Here, part per million (ppm) is considered when dosing unlike spoon for spoon as with bulk sugar replacers. Factors that challenge successful applications are undesirable aftertastes such as bitter notes that often require masking. Synergies with other HIS and bulk sugar replacers are useful to consider in such instances.

Steviol glycosides are extracted from the stevia leaf, filtered and purified. This process is similar to how other plant ingredients, such as sugar, are obtained. The sweet molecules in the stevia plant are extracted by steeping its dried leaves in water (like tea) and then separating and purifying the best tasting steviol glycosides. It is 200 to 300 times sweeter than sugar (the sweetness of about three stevia leaves can replace the sweetness of sugar in a 330ml can of 25 per cent sugar-reduced carbonated soft drink). Stevias core advantage remains that its a natural sweetener for calorie reduction and it synergises especially well with sugar, allowing partial calorie and sugar reductions.

Aspartame is a low-calorie sweetener composed of two amino acids (building blocks of protein), aspartic acid and phenylalanine components found naturally in protein containing foods, including meats, grains and dairy products. Aspartame is 200 times sweeter than sugar and works synergistically well with other high intensity sweeteners. It is not heat stable and degrades more rapidly as the heating temperature increases. It is also affected by pH being most unstable at pH 7 and stable at pH 4.

Sucralose is produced from sugar through a multistep manufacturing process. During this process a small amount of chlorine (naturally found in many foods) is added, which changes the structure of the sugar molecule. This change produces a sweetener that has no calories, but is 600 times sweeter than sugar with the closest natural sweetness profile. Fig. 2 depicts how the sweetness of sucralose is influenced by pH.

Fig 2. Dependence on pH and concentration

Synergies: Applying a combination of oligofructose with sucralose in low fat strawberry yoghurt reinforces textural and taste effects. This also results in an increase in body, creaminess and thickness, while the lingering taste characteristic of sucralose is suppressed. Compared with sugar, the respective profiles are matched very closely.

Fig. 3 Spider diagrams: Sensorial profiles of sucralose, sugar and sucralose/oligofructose combinations in low fat strawberry yoghurt

In order to establish which alternative sweetener to choose when replacing or reducing sugar, it is important to consider the functional properties of sugar:

Flavour: Sugar interacts with other tastes and flavours. In many food systems sweeteners are used to balance the basic tastes and to enhance and modify flavours. The time-intensity curves of different sweeteners vary greatly. The sweetness of, for instance, aspartame and sucralose lasts longer than that of natural sugars. Sugar is often used in fruit preparations because of its ability to enhance the flavour of the fruit. This ability varies for different types of sweeteners.

Colour: The Maillard reaction is a type of non-enzymatic browning which involves the reaction of reducing sugars and free amino acids. Sucrose is not a reducing sugar, but yeasts or acids can hydrolyse sucrose to glucose and fructose (both reducing sugars). This browning reaction contributes to flavours in bread, crusts, milk chocolates, caramels, fudges and toffees. Sugar has the ability to caramelise under heat to substances ranging in colour from pale yellow to dark brown and in flavour from milk, caramel-type to burnt and brittle.

Volume: Bulk sweeteners not only add weight and volume to the product, they also have a big impact on mouth feel and texture. HIS are used in such small amounts that they affect neither the volume nor the mouth feel of the product. As at low dosages of seven to 10 per cent, bulk sweeteners provide a different mouth feel in beverages or yoghurt than HIS. In products that require even higher amounts of sweeteners, such as mustard and sauces, texturiser is needed to obtain the same texture with a HIS as when using a bulk sweetener. In jams and marmalades, where the sugar content normally is 35-60 per cent, bulk sweeteners not only add weight, volume and mouth feel, they also influence the gelation process and consequently have a big effect on texture.

Solubility: The relatively high solubility of sucrose is an important parameter for its bulking effect in many food and beverages. The dissolved sugar increases the viscosity of water-based solutions or mixtures resulting in enhanced mouth feel. In bakery products, the solubility, or hygroscopicity of sugar makes it compete with flour proteins and starch granules for the available water, minimising gluten formation and decreasing gelatinisation. This makes the final product more moist and tender, improving shelf life.

Freezing point: Sugar lowers the freezing point of ice cream, which slows down the freezing process, resulting in an end product that is softer and easier to scoop.

Texture: Crystallisation of sugars is desirable in products such as fondant, dragees and fudge. Crystallisation occurs when the solubility limit of the sugar has been exceeded, and a supersaturated environment has been created. Gelatinisation is affected when sugar is substituted with other bulk sweeteners since conditions for gelation and the character of the gel differ. Compared to sugar, xylitol forms the lowest gel strength of pectin jelly, followed by sorbitol.

Shelf life: Pure granulated sugar has a very low water activity (a w ) and one of the most significant effects of a w is its impact on shelf life. In foodstuffs such as carbonated beverages, pickles and jams, not only the reduced a w caused by high sugar concentration, but also the low pH of such products contribute to prolonged shelf life. This is in contrast to many bakery and dairy products, sauces and dressings where preservatives must be added to achieve similar shelf life. The importance of being careful when reducing the sugar content of a foodstuff should be pointed out in order to avoid an increase in a w above the critical level (0.90) for growth of pathogenic microorganisms.

What are consumers demanding.

Sugar has replaced fat and salt as the new dietary demon. The presence and amount of sugar is the information most commonly searched for on packaging by consumers. Globally in 2013 to 2014, juice drinks and baby food products led in the use of low sugar claims followed by carbonated soft drinks and confectionery products. The backlash on sugar looks set to encourage use and development of intense sweeteners. In value terms of the overall intense sweetener market, the big movers from 2013 to 2017 are stevia, acesulfame-K and sucralose, while aspartame and cyclamate are predicted to show the greatest decline.

Locally, manufacturers are heeding to reduced sugar trends and consumer expectations. Kim Kruger, managing director of ber Nutrition says, In the nutrition bar snack category, there is a strong and growing trend towards lowering high impact sugars. The challenge is to provide good taste while keeping sugars low. Thus it is a balance between managing the emotional aspect of good taste expected by the customer when having a snack versus the analytical necessity to reduce sugar intake overall. As food manufacturers, we will continue to find those products that fit well into the consumers daily diet as an exciting, enjoyable snack that meets their health expectations.

Challenges facing food and beverage developers when venturing down the path of sugar reduction are vast. The playing field can be daunting if the full spectrum of sweeteners is not well understood and applied. So where does industry go to obtain accurate information. We provide some facts to consider when searching for alternative sweeteners.

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Publication:South African Food Review
Date:Aug 24, 2015
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