Carbohydrates and Sweeteners Flashcards
Characteristics of carbohydrates
sweet taste
solubility
mouthfeel
browning
volume
what is the ratio of hydrogen to oxygen in carbohydrates
C(1):H(2):O(1)
Mono- and disaccharides vs polysaccharides
simple vs complex sugars
What are the key pentoses and hexoses in monosaccharides
pentoses: ribose (0), arabinose (2), xylose (3)
hexoses: glucose (3) (dextrose bcuz it can bend polarized light to the right), fructose (3) (levulose or left-bending), galactose(3,4)
others mannose, gulose, sorbose
How is a disaccharide formed
when two monosaccharides join together by a glycosidic linkage eliminating a molecule of water
What are the disaccharides common in foods that all contain glucose and what are they made of?
Sucrose: glucose and fructose
Maltose: glucose and glucose
Lactose: glucose and galactose
What carbohydrates are used in food products that use alternative sweeteners to replace sugars in order to produce a product lower in calories than comparable items?
carbohydrate gums because they are not digested in the small intestine meaning they are lower in calories
Gums and pectin serve as thickening agents.
❑ Valued for their limited calorie contribution
What are oligosaccharides
composed of 3-10 monosaccharides each joined to the next by the elimination of a molecule of water.
Examples of oligosaccharides
both trisaccharides present in legumes are stachyose and raffinose
can cause flatulence because we cannot digest either due to ack of enzyme in body
What are glucosidic polysacchrides what are the different ones
polysaccharides composed on ly of glucose units linked together by alpha or beta glucosidic linkages
dextrins, dextrans, starch, glycogen, cellulose
dextrin vs dextran
Dextrins (simplest polysaccharides) are distinctly shorter in chain length than starch. They have slight solubility, a barely sweet taste, and limited thickening ability. Formed when flour is browned with dry heat. 1,4 alpha glucosidic linkages.
Dextrans are found in bacteria and yeast made up of glucose linked by 1,6 alpha glucosidic linkages. Branching occurs
what is starch and its components?
starch is a glucose polymer of large dimensions composed of amylose and amylopectin
amylose vs amylopectin
amylose is a large linear molecule of more than 200 glucose units linked by 1,4 alpha glucosidic linkages. It is slightly soluble and does not have a sweet taste
Amylopectin primarily consists of 1,4 alpha glucosidic linages but interrupted occasionally by 1,6 apple glucosidic linages resulted in a branched structure with little solubility and it also does not contribute sweetness. Extremely large
Glycogen vs cellulose
glycogen is the storage form of carbohydrate in animal tissue. Similar structure to amylopectin. BULKY BRANCHING.
Cellulose cannot be digested as an energy source because of the human inability to split 1,4 beta glucosidic linkages
Non-glucosidic polysaccharides
Other polysaccharides in which some simple sugar other than glucose is the building block of the molecule
Ex. Inulin, pectic substances, gums
Inulin vs pectic substances vs gums
Inulin- complex CHO, polymer of fructose, not digested, combined with carrageenan to create creamy texture in low fat food
pectic substances(methylated form: pectin) - building block is a derivative of galactose, galacturonic acid linked in 1,4 alpha glycosidic linkages
Gums- complex polysaccharide found in seeds, plant exudates, seaweed. Most have galactose as main component. Sed gums also have mannose. USED AS STABILIZING AGENTS AND FAT REPLACERS
GUMS and Pectins vs STARCH vs CeLULOSE and Hemicellulose in food
gums and pectins serve as thickening agents and limited calorie contribution
starch is valued for thickening ability
cellulose and hemicellulose modify textures when incorporated in food, somewhat harsh mouthfeel
physical properties of sugar
1) Sweetness- when dissolved all sugars are sweet to the tongue, temperature of solution influences relative sweetness values for sugars,
2) Hygroscopicity- sugar attracts and hold water to varying degrees
useful in maintaining freshness of some baked goods, increased temperature increases absorption of moisture from atmosphere, can be source of texture problems when humidity is high
3) Solubility- The amount of sugar that will go into solution in water varies based on type of sugar and temp of water
Chemical reactions of sugar
Hydrolysis- disaccharides undergo hydrolysis when heated, an acidic medium favors this degradative reaction, as does the presence of water (occurs during preparation of candies)
Degradation- first step is the opening of the ring structure forming aldehyde or ketone depending on whether the original sugar was a pyranose of furanose ring. Can take place in acidic medium but more readily in alkaline
Caramelization- when sugars are heated to melting temperature, chemical reactions can lead to charring or burning. Caramelization can be halted abruptly by rapid addition of boiling water to hot sugar mixture
Mallard reaction- Non enzymatic browning. Series of reaction involving condensation of a reducing sugar and an amine (glucose, fructose, galactose, not sucrose). Colored pigments- melanoidins are formed.
proceeds quickly at high temperatures also room temp during extended storage
functional properties of sugar
flavor, color, texture, stabilizes egg white meringues, tenderizing
color when heated to high temperature or for an extended period- caramel
What are crystalline candies
-made by?
-what happens as candy boils?
-final temperature is associated with?
-common ingredient?
-what promotes inversion aka (???) of sucrose producing ???
-extent of inversion is related to?
-extensive inversion causes?
-what interferes with aggregation of sugar crystals?
1-candies that are easy to bite and have large areas of organized sugar crystals
2-Made by boiling sugar and water to concentrate the sugar syrup to form a firm, crystalline structure when cooled.
3-water evaporates while the candy is boiling gradually increasing the sugar concentration which causes decreased vapor pressure-raising the boiling point slowly
4-The correct final temperature is
correlated with the concentration of sugar.
5-acid is common ingredient (cream of tartar usually)
6-during boiling acid promotes inversion(hydrolysis) of some sucrose molecules producing invert sugar (equal parts glucose and fructose)
7-Extent of inversion by acid during boiling is directly related to the rate of heating
8-extensive inversion causes crystalline candies to be softer than anticipated
9-Fat and crystal shape of different sugars interfere with aggregation of sugar crystals useful for smooth texture- fudge
Crystallization in crystalline candies
-what happens when boiling candy is removed from heat?
-when ______ is reached, _____ is initiated to the sugar crystals?
-An agitated viscous solution at about __°C(___°F) results in?
-the finished product’s texture?
When boiling candy is removed from the heat, the solution is
saturated—all the sugar is in solution.
A stable arrangement.
As the solution cools, the amount that theoretically can be in
solution is reduced.
–When the desired degree of supersaturation is reached, beating
is initiated.
Provides constant disruption of the crystals as they attempt to
aggregate.
Excess sugar will start to crystallize promptly if any nuclei for crystallization are provided.
—An agitated viscous solution at about 45°C (113°F), results in
crystallization of excess sugar in very small aggregates.
The finished product has a
smooth, almost velvety feel
on the tongue.
Ripening of crystalline candy
-what occurs to the sugar crystals in products during storage?
-how does the texture of the candies change during storage?
-What causes this change?
-what helps retard undesirable ripening changes?
-ripening produces a ___ product?
Continual dissolution and recrystallization of sugar crystals
occur in these products during storage.
Referred to as the ripening of the candy.
The texture of ripening candies gradually becomes coarser
during storage.
Due to the increasing size of the crystal aggregates.
-Adequate amounts of interfering substances in the recipe helps
retard undesirable ripening changes.
Chocolates with cream centers require several days of ripening
before reaching optimum texture.
Ripening produces a creamier, smoother texture.
factors in creating smooth texture in crystalline candies and interfering substances
Supersaturation and adequate beating are two factors in creating smooth-textured crys- talline candies
-the presence of a variety of sugars and other interfering agents promote a smooth texture.
-Cream of tartar promotes an appropriate amount of inversion of sucrose when the solution is boiled at a moderate rate;
-fat-containing ingredients also help ensure successful crystalline candy products.
Evaluation of crystalline candies
what should texture be like?
mouthfeel?
what cause candy to be too soft?
slow rate of boiling may cause?
gritty texture can result from?
–>Crystalline candies should hold their shape when cut—yet be bitten
easily.
Mouthfeel should be velvety smooth.
Failure to obtain the correct final temperature is often a problem.
–>The hygroscopic (water-attracting) nature of sugar can cause a
candy to be too soft.
An excessively slow rate of boiling can result in too much
hydrolysis when acid is present
–>Gritty texture may result from:
Addition of too few interfering substances.
Premature crystallization; improper beating.
Amphorus candies
how are they different to crystalline?
basic ingredients?
what causes flavor/color changes?
they are evaluated on basis of what?
boiled to much higher temperatures than crystallin candies, concentration of sugar is far greater
basic ingredients are sugar and water, fat is often included as cream or butter
intense heat involved is destructive to sugar molecules–> flavor/color changes
Amorphous candies are evaluated on the basis of their color, flavor, and
texture.
why does toffee defy the organization of crystals? what type of candy?
what causes the glassy state of candies?
–Toffee has such a high concentration of sugar and is so viscous
when poured that it defies organization of crystals.
–Candies with such a high
concentration are in the
glassy state when cooled.
In yeast leavened breads what happens to the sugar present(what is the sugar) and what is the purpose of this process?
What other sweeteners can be used for this?
In yeast-leavened breads, sucrose is split and inverted by yeast invertase.
To provide glucose and fructose for fermentation.
Corn syrup, HFCS, and dextrose (glucose) are other possible ingredients used for fermentation.
Large amounts of sugar in cakes cause what??
How does sugar extend shelf life?
dilute the protein structure—increasing volume and delaying setting.
Sucrose interferes with microbiological growth.
When does browning of the crust occur most quickly in a cake?
Baking with ____ will cause bakes goods to brown faster because of its ______ content
Cakes made with_____ may brown extremely fast. The syrup can influence crumb color.
-Browning of the crust occurs most quickly when a cake contains monosaccharides due to the Maillard reaction and some caramelizing.
-Baking with honey will cause baked goods to brown faster because of
its high fructose content.
-HFCS
What can be done to batter to help control browning
____, the usual type of sugar in cookies contributes to the ____ of the dough during baking.
Reducing batter pH to slightly less than 7.0 from its probable range
of 7.1 - 7.5 helps control browning.
Sucrose, the usual type of sugar in cookies, contributes to the spreading of the dough during
baking.
Name each sweetener and why they should be chosen for a specific food product.
sucrose: most common
-granulated has most applications
superfine/dessert sugar for meringues due to ease of dissolving fine crystals
-powdered sugar is sucrose pulverized and blended with cornstarch to prevent caking and to help bind moisture in for example icing
-brown sugar is less refined than white impurities contribute to more intense flavor
fructose: available in markets and food industry, sweeter than sucrose
—>HFCS is made by using an enzyme to convert some of the glucose in
corn syrup into fructose.
A dextrose equivalent (DE) of 65 DE.
—.Corn syrup represents a mixture of carbohydrates, ranging from
glucose to oligosaccharides
Molasses is a by-product of the production of sugar from sugarcane—a sulfured/unsulfured liquid.
Final sugarcane boiling yields blackstrap molasses, Most commonly used in animal feeds.
Honey is popular due to its distinctive flavor.
Sorghum syrup is made from grain sorghum.
Juice is boiled down a maximum of 30% water.
Polyls are naturally occurring compounds in food they are absorbed by the body far more slowly than sugars
name them and their applications
Xylitol is used for sweetening chewing gum without the cariogenic properties associated with sugars.
Sorbitol is useful as a sweetener, humectant and bulking agent. Its water-binding capabilities help limit mold growth. Metabolized without insulin
Mannitol can be used as a bulking agent where the hygroscopic nature of sorbitol is a detriment. also anticariogenic, used in chewing gum
Saccharin(non caloric) is an intense swwetener that was important in foods for diabetics. A disadvantage is the distinctive and strong bitter aftertaste evident at comparatively high levels.
cyclamate 30 times as sweet as sucrose, no aftertaste/calories, banned in US since 1970
Sucralose is 600–800 times sweeter than sucrose, is heat stable, and lacks any unpleasant aftertaste
Polydextrose is a randomly bonded glucose polymer used extensively as a bulking agent
an extract from monk fruit (also called Luo Han Guo).
It is about 300 times sweeter than sucrose, but the fruit pulp also contains some unpleasant-tasting compounds that can be removed during processing
Differences in color, flavor and browning will result when using some of the substitutions suggested.
Saccharin is the sweetest of the non-nutritive sweeteners presently in use, being remarkably sweeter than sucrose, but plagued with a bitter aftertaste;
Fructose is the sweetest of the sugars and the most soluble, whereas lactose is the least sweet and least soluble of the common sugars.
All of the sugars are hygro- scopic, with fructose being considerably more hygroscopic than sucrose at room tem- perature,
