Technical talk: Use of sugars in baking
February 18, 2009 By John Michaelides
Sugar is one of the major ingredients used in the baking industry. In
some cases, sugar use exceeds that of flour. It provides sweetness but
Continuing our series examining new developments in the basic ingredients of baking, and their effect on the baking industry, what are the types of sugars and syrups normally used in baked goods and what is their functionality?
Sugar is one of the major ingredients used in the baking industry. In some cases, sugar use exceeds that of flour. It provides sweetness but also functionality.
Sugars belong to one of the major classes of organic chemical compounds – carbohydrates. The other two are fats and proteins.
Carbohydrates consist of carbon, hydrogen and oxygen, and are classified into three major types: monosaccharides (single units that can not be hydrolyzed or broken down further), oligosaccharides (a few units, usually two to three) and polysaccharides (many units). Single units of sugars are further characterized by the number of carbon atoms in their structure.
The normal sugars we use contain six carbon atoms and are called hexoses. Pentoses (sugar units in cellulose, for example) contain five, while heptoses contain seven carbon atoms. For the purpose of this article, when we refer to sugars we will mainly deal with hexoses.
The main monosaccharides we encounter in baking are glucose, fructose and galactose. The disaccharides (two sugar units) are derived from each of these single sugar units as follows: sucrose = (glucose + fructose), maltose = (glucose + glucose) and lactose = (glucose + galactose). An example of polysaccharide with many glucose units is starch.
Sugars in the baking industry are used in dry, liquid or syrup form. Most of the dry sugar used in the baking industry is refined sucrose from sugarcane or sugar beet, whose raw sugar is produced by extraction into liquid molasses and further processed into basic and other forms of brown or raw sugar.
Refined sugar is produced by first transforming the raw sugar into pure sucrose. Further refining into different types is determined based on the final application in different products.
Commercially refined dry sugars are categorized into two major groups: granulated and powdered sugars. Granulated sugars include fine-grained coating sugars, bakers’ special coarse granulated, medium, medium fine, extra fine, etc. All these grades are produced by careful control of the crystallization process and separation into different sizes by sieving.
Powdered sugars are produced by grinding coarse granulated sugar and passing it through fine bolting cloths. They are available in various degrees of fineness ranging from fondant to ultra-fine. Their fineness is categorized by a series of Xs indicating their particle size distribution. For example, a 6X powder sugar has a particle size that will allow 90 per cent passage through a 200-mesh screen, whereas a 10X will allow the same percentage to pass through a 325-mesh screen.
Other types of sugars are available commercially. These include transformed sugar, which is obtained by a special flash-drying process, resulting in irregular particles that cause the sugar to be highly aerated, easily crumbled and dissolve almost instantly in water. Other types include soft sugars, in which the crystals are basically coated with leftover mother liquor (molasses), resulting in higher moisture content (two to four per cent). These soft sugars are assigned grade numbers from one to 15 and range from pure white to extremely dark colour.
Many liquid sweeteners are available for baking. These can be simple blends of sucrose or inverted sugar in water. The majority of liquid sugars are, however, produced from raw sugar through a series of purifications, removal of adhering molasses to crystals, and further treatment with lime and phosphoric acid resulting in the liquid sugar.
Inverted sugar results from heating this solution with a diluted acid, hydrolyzing it to its constituent monosaccharides to form a mixture of glucose and fructose. The different liquid sweeteners have specifications based on their solids composition, ash content, pH, colour and ratio of the individual sugars.
High-fructose corn syrups (HFCS) are among the most widely used syrups in the food industry. These are manufactured by the enzymatic conversion of glucose in the corn syrup to fructose. The enzyme is called glucose isomerase. The commercially available HFCS contain amounts of fructose ranging from 42 to 90 per cent.
In the baking industry, the most widely used HFCS are those containing about 42 per cent fructose. Normally HFCS containing fructose at a higher level than 50 per cent are used in other foods and beverages. A typical 42 per cent HFCS will contain 50 per cent dextrose (D-glucose), 42 per cent fructose, three per cent maltose and five per cent other sugars.
Other natural liquid sweeteners include honey, maple syrup, molasses, malt and malt syrup, and maple and sorghum syrups. Honey resembles the HFCS and the different types are categorized according to colour and flavour obtained from the nectar source.
In yeast-leavened baked goods, sugars provide the food for the yeast that produces carbon dioxide for the leavening action. The yeast secretes enzymes that split the sucrose into simpler sugars, which can be more easily fermentable. When glucose and fructose are present in dough the yeast ferments glucose first. Different sugars and syrups play different roles in different baked goods, such as improving texture crumb and grain. They also provide a tenderizing effect. Certain sugars such as fructose, inverted sugar and honey will retain water and thus extend shelf life.
There are many choices of sugars with different characteristics and different functionalities, so it’s important to choose the proper sugar for each type of baked good we are formulating. It is also important to keep in mind that changes in the properties of sugar may occur during storage and handling in the food manufacturing facility.
Concern is growing about the amount of sugar in our diets. Obesity, diabetes, heart disease and other chronic ailments are becoming more predominant in developed and developing countries, and sugar contributes to these increases. Thus, attempts are being made to develop foods, including baked goods, using alternative low-calorie sweeteners.
In addition to artificial sweeteners, there is also demand for baked goods made with more natural unrefined sugars. Recent research indicates that unrefined sweeteners may contribute certain antioxidant health benefits to our diets. / BJ
Funding for this report was provided in part by Agriculture and Agri-Food Canada through the Agricultural Adaptation Council’s CanAdvance Program. For more information, or fee-for-service help with product or process development needs, contact the Guelph Food Technology Centre at 519-821-1246, by fax at 519-836-1281, or by e-mail at email@example.com.
Dr. John Michaelides is GFTC’s director of research and technology.
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