Food Science L6

Sugars and Fats Lecture

• The lecture covers sugars, sugar substitutes, types of sugars, properties of sugars, importance of sugars in food products, baked products and fats. Also, methods for preserving fats and oils.
• Sugars come from sugar beet and sugar cane.
• Sugars provide sweetness, tenderness, and browning in food products.
• Sugar acts as a separating agent to prevent lump formation in starch-thickened sauces.
• Sugar reduces starch gelatinization.
• Sugar stabilizes egg white foams and raises the coagulation temperature of protein mixtures.
• Sugar adds bulk and body to foods, such as yogurt.
• Sugar helps aerate batters and dough.
• Sugar reduces gluten structure by competing with gliadin and glutenin for water, thus increasing tenderness.
• Sugar acts as a substrate for fermenting to yield CO2 and alcohol.
• Sugar adds moisture retention properties to baked products and slows/prevents crystallization.
• Browning in fruits and vegetables can be enzymatic or oxidative.
• Nonenzymatic browning involves the Maillard reaction and caramelization.
• The Maillard reaction is responsible for the color changes in baked foods like breads, cakes, and pie crusts, and canned foods.
• Caramelization occurs when sugars are heated above their melting point, opening the sugar ring and losing water.
• Common types of sugars include brown sugar, confectioners' sugar, invert sugar, and raw sugar.
• Brown sugar has a molasses film on the sugar crystals and contains approximately 2% moisture.
• Invert sugar is created when sucrose is treated by acid or enzyme to form fructose and glucose.
• Raw sugar has a larger grain than ordinary granulated sugar.
• Types of syrups include corn syrup, high-fructose corn syrup (HFCS), honey, maple syrup, and molasses.
• Corn syrup is a mixture of carbohydrates formed from the hydrolysis of cornstarch.
• High-fructose corn syrup contains approximately 42% fructose.
• Honey is made from flower nectar and contains glucose and fructose.
• Maple syrup is obtained from maple tree sap.
• Molasses is a by-product of sugar making.
• Sugar substitutes include artificial sweeteners like acesulfame K and aspartame, and sugar alcohols.
• Acesulfame K is 200 times sweeter than sucrose and not metabolized.
• Aspartame is a nutritive sweetener containing the same number of calories per gram as sugar (4 calories/gram).
• Saccharin is a noncaloric substance produced from methyl anthranilate.
• Another sugar substitute is cyclamate.

Baked Products

• Quick breads (e.g., pancakes, doughnuts) use baking powder or backing soda as leavening agents
• Yeast bread uses yeast.
• Common ingredients in baking include flour, liquid, starch, fats, sugar, sweeteners, and leavening agents (baking soda and baking powder) to produce CO2, liquid, and flavoring agents (like eggs).
• Gluten is a substance in wheat flour that gives structure to baked goods.
• Flour types include bread flour (highest gluten content, creamy white), cake flour (very low gluten, pure white), pastry flour (very low gluten, creamy white, slightly less delicate), and all-purpose flour (medium gluten content).
• Gluten-free flour is for people sensitive to gluten.
• Liquids are crucial in hydrating proteins for gluten formation and gelatinization. Liquids are the solvents for dissolving ingredients (baking powder, soda, salt, and sugar).
• Liquids produce steam during baking, which leavens and expands air cells.

Fats

• Fats belong to a larger group called lipids, which include fats, oils, and cholesterol.
• Fats are formed by the reaction between fatty acids and glycerol which forms esters called triglycerides.
• Trigylcerides are formed of 3 fatty acids or 3 different fatty acids.
• Fatty acids are chemical chains that contain carbon, hydrogen, and oxygen.
• Saturated fatty acids have as many hydrogen atoms as possible.
• Unsaturated fatty acids have fewer hydrogen atoms than possible.
• Fats and oils are insoluble in water but become emulsions with emulsifiers .
• Fats do not melt at fixed temperatures, but over a range of temps.
• Heating fats and oils causes them to decompose.

Prevention and Uses of Rancidity and Fats

• Some triglycerides react with alkalis to form soap and glycerol (saponification).
• Hydrogenation adds hydrogen to break double bonds, which makes the fat more saturated.
• Fats can be rancid if not handled properly because of oxidation (reaction with oxygen in air) or hydrolysis.
• Oxidation occurs due to oxygen, and is accelerated by heat, light, and metal traces.
• Hydrolysis occurs by enzymes, which break down fats.
• To prevent rancidity, keep fats away from oxygen, light, and metal. Salt speeds up rancidity, while sugar slows it down.
• Antioxidants can be used to preserve fats and prevent rancidity.
• Fats have a wide range of uses in cooking, including frying, shortening, creaming.

Salt and Sugar Function in Baked Goods

• Salt controls yeast growth and speeds up yeast development while contributing flavor.
• Sugar tenderizes baked goods by raising the protein coagulation temperature and gelatinization, which helps CO2 expand.
• Sugar also enhances flavor.

Fat Sources

• Vegetable oils make up a large portion of oil use, and include polyunsaturated fatty acids.
• Margarine is an emulsion of water and fat; and the vegetable fat is hydrogenated.
• Butter is pasteurized cream which is churned.