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CHO

Food carbohydrates (CHO) All CHO contain C,H and O. The basic building block of CHO is “simple” sugar, that is also termed organic alcohol. CHO exist as monosaccharide (a single sugar molecule not chemically bonded to other sugar molecules), disaccharides, Oligosaccharides, or Polysaccharides. Monosaccharides 3 carbon atoms (trioses) 5 carbon atoms (pentoses) 6 carbon atoms (hexoses) Important monosaccharides found in foods are hexoses: glucose, fructose and galactose; sharing formula C6H12O6.

Structures of simple sugars.

Although the hexoses share the same formula, slight differences in the location And functional groups cause differences in functional properties (see structure). Fructose, existing as a 5-membered ring structure is sweeter and more soluble Than glucose (6-membered ring; sometimes called dextrose). Monosaccharides are the basic units around which larger CHOs are built. Disaccharides 2 Monosaccharides joined together (via glycosidic bond) to form a disaccharide. The three most important food disaccharides are: a) Sucrose (glucose and fructose), a common table sugar, b) Lactose (glucose and galactose) found in milk, and c) Maltose (glucose and glucose).

Structures of disscharides

Functional properties of sugars Sugar molecules contain 2 important, reactive functional groups: Carbonyl group: reducing and Maillard browning (color and flavor). Alcohol group: readily forms hydrogen bonds with water molecules, thus contribute to solubility. Glucose has 5 OH groups, thus very soluble. OH also contribute to sweetness. Reducing sugars Sugars that contain the aldehyde or ketone carbonyl groups; all monosaccharides and certain disaccharides are reducing sugars. Dextrose equivalent (DE): a measure of % of glycosidic bonds hydrolyzed in disaccharides or polysaccharides, which indicates the level of reducing sugar Present. Pure dextrose: DE value of 100. But, Starch: DE value of 0. The higher the DE, the more soluble and the greater the reducing ability of a sugar.

This is due to sugars

Browning Caramelization: Maillard browning*: Reaction of reducing sugar With amino acids at low (long storage time) to high processing temperatures, producing Brown color pigments (melanoidins) Caramelization: Formation of brown caramel pigments (caramelen, C24H36O18) As a result of applying heat energy to Sugars. Typical Temperature is > 200°C. Desirable: Aroma, brown Surface, flavor Undesirable: Unwanted browning/ Off-odors/polymerization/ Texture toughening/ alleged Free radicals etc Also known as nonenzymic browning because enzyme is not part of the reaction Why “Maillard” name? Flavor, brown color HOT: Dodol? Coke? Roast beef?

Desirable: Undesirable: Crystallization. Sugars can exist in 2 states: crystalline  syrup (soluble). Crystallization: When units of sugar organize in 3-D arrays into a solid form. A crystal: a solid made up of sugar units in a repeating pattern (see figure). Crystalline structure Desirable: Purification of sugar during manufacture of table sugar/ manufacture of hard candy where sugar melts upon heating and recrystallize when cooled into different crystal size and form. Undesirable: Formation of large sugar crystals in ice cream/ condensed milk yielding coarse and gritty texture (or graining)

Boiled at low temperature Under vacuum + seeding Clarified sugar cane Boiled in evaporator Thick syrup Boiled at low temperature Under vacuum + seeding Development of sugar Crystals (with molasses) Growth of sugar Crystals (with molases) Centrifugation Sugar Crystals Molasses

Crystallization: formation of solid crystal precipitating from a solution or melt 2 events: nucleation, and then crystal growth.

Humectancy Humectant?: A substance that has affinity for moisture (and are thus hygroscopic – able to attract and retain moisture). Able to hydrogen bond with water molecules, making water less available for microbial growth, thus help to preserve foods. CHO, especially sugars are used in food to influence the state of water. a) fructose is more hygroscopic than sucrose, and is thus used to reduce Aw in food systems. b) Sucrose is less hygroscopic, and is thus free-flow more easily during dry-mixing or packaging (of dry products) compared to fructose. Inversion The hydrolysis of sucrose to its component monosaccharides or invert sugars that are sweeter than sucrose alone. Sometime an enzyme invertase is added to invert sucrose.

Oligosaccharides: Polysaccharides: Polysaccharides and their functional properties (general) Size and Complexity Of their structures Complex CHO are composed of joined sugar units Oligosaccharides: 10 or fewer sugar units; Non-reducing. Example: raffinose, stachyose. Poorly digested, and thus fermented In large intestine (yielding gas And may cause flattulence). Beans, soybeans, peas. Polysaccharides: 40 or more sugar units. Potentially hundreds more! May contain reducing and Non-reducing ends (susceptible To enzyme attack). Occur more frequently than Oligosaccharides. Important food polysaccharides: Beta-glucan, cellulose, dextrins, FOS, maltodextrins, pectic substances, Starch, vegetable gums. Will be covered More In depth in food chemistry

HOT Differences between Nutrition facts and Ingredients Find complex CHO: