FOOD CHEMISTRY

Module 7. Food additives

Lesson 19
SUGAR SUBSTITUTES-SORBITOL, SACCHARIN, CYCLAMATE

19.1 Introduction

Sugar substitutes are those substances that are used like sugars for sweetening, but are metabolized without the influence of insulin. Important sugar substitutes are sugar alcohols sorbitol, xylitol and mannitol and to acertain extent fructose.

19.2 Classification of Sweeteners

Sweeteners can be divided into two main groups: bulk and intense sweeteners:

Bulk sweeteners conferring body and texture to foods, are completely metabolized by the body and provide an important part to our energy. They are also referred to as nutritive or calorie sweeteners.

Intense sweeteners are generally not metabolized by the body, and are excreted unchanged and used at very low levels in foods, hence are referred to as non- nutritive or non-calorie sweeteners. Unlike bulk sweeteners, these are generally not metabolized by the body and are excreted unchanged.

19.2.1 Bulk sweeterns (Nutritive)

• Sugars (refined sugars, sucrose, fructose, glucose, dextrose, maltose, etc.)
• Sugar replacements/ polyols/sugar alcohols (sorbitol, mannitol, xylitol, etc.)

19.2.2 Intense sweeteners (Non-nutritive)

• Natural of plant origin (glycyrrhizin, steviosides, thaumatin)
• Synthetic(aspartame, acesulfame-K, saccharin, sucralose, cyclamate, etc.)

19.2.3 Nutritive sweeteners

They are defined as the products that have greater than 2% of the calorific value of sucrose per equivalent unit of sweetening capacity. Typical of this food additive class is high fructose corn syrup. Not only it is sweeter than sucrose, it also adds body or thickness liquid preparations. In addition it acts as humectants in semimoist food systems.

Polyols (known as sugar alcohols or polyhydric alcohols) are produced by hydrogenating corresponding reducing sugars. These nutritive sweeteners provide the bulk and texture ofsucrose but can be labeled as fewer kcal /g. Members of this group include sorbitol(2.6 kcal/ gm), mannitol (1.6 kcal /gm), erythritol (0.2 kcal/g), lactitol (2 kcal), isomalt (2 kcal) and maltitol (3 kcal/g). Polyols do not provide browningin foods when baked. Polyols can combine with other alternative sweeteners foruse in chewing gums, candies, frozen desserts and baked goods as well as in thedevelopment of new products, particularly those that offer neutraceutical benefits.

a) Sorbitol

Sorbitol, a polyalcohol, is approximately one half sweet ascompared to sucrose. It is hygroscopic in nature and also known as alcoholsugars. It is used as a sweetener for diabetics and in food canning. Sorbitolcan be commercially prepared by catalytic hydrogenation of glucose. Acid-catalyzed elimination of water yields a mixture of 1,4-sorbitan (85%, I)and 3, 6-sorbitan (15%, II). Under more drastic conditions (action ofconcentrated acids), 1, 4:3, 6-dianhydrosorbitol (isosorbid III) is formed.

19.2.4 Non-Nutritive Sweeteners

These include both naturally occurring and synthetic compounds that have elevated sweetness or sweetening power as compared to sucrose. As a result, they are usually incorporated at lowlevels into various foods as a replacement for sugar. These compounds make possible the manufacture of a wide range of low or reduced-calorie foods to serve the needs of people who have a need or desire to reduce their calorie intake. Although, the use of potentially useful non-nutritive sweeteners is growing, only a few are currently available for food application.

1. Saccharin: the primary non nutritive sweetener available currently is saccharin. Both the sodium and calcium salts of ortho benzosulfimide are used. Sodium saccharin is the most commonly used because of its high solubility and stability. The level of use depends on the intensity of sweetness desired. In higher concentration, the compound has a light bitter after taste. It is about 300 times sweeter than sucrose in concentrations up to the equivalent of a 10 % sucrose solution. The present stipulated ADI value is15 mg / kg of body weight.

2. Cyclamates: it is marketed as sodium or calcium salt of cyclohexanesulfamic acid. The sweetening strength is substantially lower than of saccharin and is 30-40 times sweeter than sucrose. It has no bitter after taste. Overall,the sweet taste of cyclamate is not as pleasant as that of saccharin. Cyclamates were approved for use in US in 1950 but were later prohibited because ofevidence suggesting they were carcinogenic. It has been approved in more than50 countries as a tabletop sweetener, and in sugar free beverages, baked good sand other low calorie foods. However, its use is banned by PFA.

3. Sucralose: it is high intensity, non caloric sweetener made from sugar. Sucralose is a free flowing, water-soluble white crystalline powder. It is a chlorinated sucrose derivative. It is said to be on average 600times sweeter than sucrose. It is formed by a process wherein three hydrogen-oxygen groups on the sugar molecule are replaced with three chlorine molecules. The small amount that is absorbed is not metabolized for energy. It is also said to have excellent stability under a broad range of processing, pH and temperature conditions. It is also highly soluble in water and ethanol.Sucralose carries no health warnings. More than 100 studies have been conducted over 20 years to support safety claims, and no population subgroup has been excluded from using it. ADI is 5 g / kg body weight / day.

4. Ace sulfame potassium (Ace-K): Ace-K, a non-caloric sweetener that is around 200 times sweeter than sucrose was approved by FDA for use in non alcoholic beverages. Ace-K is not metabolized, so it contributes no calories. It has sweet, clean taste, and it remains stable under high temperatures. Beverages containing it can be pasteurized under normal pasteurizing conditions with out loss of sweetness. One major advantage is its synergy with other sweeteners, including nutritive and non-nutritive types.

19.3 Characteristics of an Ideal Sweetener

An analysis of the organoleptic and functional properties of each single sweetener clearly shows that none of the currentlyknown sugar substitutes comes close to the taste and functional properties of sucrose. Most exhibit one or more differences like taste properties, e.g.: sweetness lag, lingering aftertaste or bitterness, lack of bulking properties,stability problems during storage and competitive prices. The characteristics of an ideal sweetener are:

Table 19.1 Characteristics of an ideal sweetener