Carbohydrates Flashcards
__________ is the most common hexose found in foods and the major sugar in the blood
Glucose
A derivative of __________, galacturonic acid, is a component of pectin, which is very important in the ripening of fruits and the gelling of jams
Galactose
TRUE or FALSE?
Saccharide nomenclature uses D or L to describe the chemical spatial arrangement of certain saccharides
TRUE
__________ also called fruit sugar and levulose, if found primary in fruits and honey
Fructose
Sucrose is commonly known as __________ sugar, and consists of one glucose molecule and one fructose molecule linked together
Table
A glucose molecule bound to a galactose molecule forms __________, one of the few saccharides derived from an animal source
Lactose
The majority of starchy foods in their natural state usually contain a mixture of about 70-85% amylopectin and 15-30% __________
Amylose
In foods, heat, enzymes and __________ are used to break starches down into smaller fragments called dextrins
Acid
Why do starches from different plant sources differ in their ability to gel?
Because of the differences in concentration of amylose and amylopectin in various plant sources
- Corn starch: high amylose (forms gel)
- Potato starch: high amylopectin (no/poor gel)
Pectic substances are found between and within the cell walls of fruits and vegetables include protopectin, pectin and __________
Pectic acid
TRUE or False?
Gums are used in many frozen products because they control crystal growth, yield optimal texture, and make the food more stable in the freezing and thawing process
TRUE
Starches that have been changed structurally by chemical or mechanical means are called __________ starches
Modified
What are the effects of salt and sugar on starch gelatinization?
They compete for water and interfere with the gelling ability of the starch
How are retrogradation and syneresis related?
Syneresis is the term used for water leaking from the gel and is the result of retrogradation
List the following sugars in order of decreasing sweetness. (1 = sweetest, 5 = least sweet)
Glucose, Maltose, Lactose , Fructose, Sucrose
1) Fructose
2) Sucrose
3) Glucose
4) Maltose
5) Lactose
What are the effects (increase or decrease) of sugars on: Water activity Microorganisms Chemical reactions Stability
Water activity: DECREASES
Microorganisms: DECREASE
Chemical reactions: DECREASE
Stability: INCREASES
What are the by-products of sugar fermentation in the following cases?
Bread-making
Pickles/sausages
Wine/Beer
Bread-making: CO2
Pickles/sausage: Acid
Wine/Beer: Alcohol
Direct heating of sugar is called __________
Caramelization
What type of reaction cause colour change in the following foods? Potato chips, bread crust, roasted meat, roasted nuts
Maillard Browning
Define sugar crystallization
Process of evaporating excess water from a sugar solution by heating and formation of sugar crystals upon cooling
Define hygroscopic
Ability to absorb water
Modified starches are widely used in the food industry. Give 2 examples of products where the use of modified starches contributes to desired characteristics
1) Pre-gelatinization of starch in INSTANT PUDDING (only requires addition of cold water)
2) SAUCES IN FROZEN MEALS (addition of phosphate linkages in modified starch increase freeze stability)
Reactions involving carbohydrates include
Caramelization, Maillard browning, Gelatinization, Hydrolysis
The __________ and __________ fractions of starch provide the necessary substrates for enzymes to specifically hydrolyze alpha 1-4 or alpha 1-6 linkages between glucose units to release smaller maltose or dextrins
Amylose; amylopectin
If you hold an unsalted cracker in your mouth for several minutes, you may notice a slight __________ taste as your saliva breaks down __________ from the cracker
Sweet; starch
Starch molecules are not very soluble in __________ water. As temperature increases, starch molecules vibrate more, break intermolecular bonds, and increase _________ bonding to water
Cold; hydrogen
Upon cooling of the starch solution and subsequent storage, starch gels are formed, whereby polysaccharide molecules tend to associate with one another due to __________ bonding
Hydrogen
Although water control reactions and physical behaviour in foods, it is not the total amount of water that is important, but rather, the __________
Water activity
__________ are long-chain polysaccharides primarily found in the spaces between the cells of fruits and vegetables
Pectin
Direct heating of sugars will result in a reaction called __________
Caramelization
Name 2 plant gums and 2 seaweed polysaccharides
1) PLANT GUMS: Guar Gum and Locust Bean Gum
2) SEAWEED GUMS: Alginate and Carrageenan
Important properties of starches in foods include
1) Poorly soluble in cold water
2) High water holding capacity (important to increase viscosity)
3) Digestible
4) Not sweet
