L2 FOOD COMPONENTS AND THEIR CHEMISTRY Flashcards
What are all the physical properties of food?
shape,colour,,size,surface condition,texture
What are the microbiological properties?
Microbial Load.Microbiological load refers to food safety. Any food product should not exceed its legally defined limits of microorganisms.
What are the sensory properties and explain them?
Flavor is a combination of taste and smell.
Aroma is detection of volatile components (smell)
The taste of a food is a combination of five major tastes—salt, sweet, sour, bitter, and umami
Texture refers to those qualities of a food that can be felt with the fingers, tongue, palate, or teeth.
Appearance includes its size, shape, color, structure, transparency or turbidity, dullness or gloss, and degree of wholeness or
damage.
What are Carbohydrates?
The term carbohydrate often means any food that is particularly rich in the complex carbohydrate starch (such as cereals, bread, and pasta) or simple carbohydrates, such as sugar (found in candy, jams, and desserts).
Two types based on functional groups – ketoses and aldoses
What are the classification of carbohydrates with eg?
Monosaccharide 1 unit (glucose,fructose,galactose)
Monosaccharides are water-soluble crystalline compounds. They are aliphatic aldehydes or ketones which contain one carbonyl group and one or more hydroxyl groups.
Disaccharide 2 unit (sucrose lactose)
Oligosaccharide 3-20 units
Polysaccahrides >20 (chitin,cellulose)
Which monosaccharides are hexoses and which are pentoses?
Hexoses:Glucose,Frucotse,Galactose
Pentoses:Arabinose,Xylose
What are the 2 types of polysaccharides(give eg) and explain the bond of the bond that joins the monomers.
Polysaccharides containing all the same monosaccharides are called homopolysaccharides (e.g., starch, cellulose and glycogen are formed from only glucose), whereas those which contain more than one type of monomer are known as heteropolysaccharides (e.g., pectin, hemicellulose and gums).
Glycosidic Bond
• Formed between the free carbonyl group of one monosaccharide and a hydroxyl group of another monosaccharide
What are the 5 functions of carbohydrates and explaiun.
Macronutrient- calories provider Sweeteners and preservatives Body and mouthfeel Fermentation Preservatives
Carbohydrates are energy provider and are counted as macronutrient. Each gram of carbohydrate provides 4 Cal of energy. Three macronutrients are lipids, proteins and carbohydrates.
The most obvious sensory property of sugars such as glucose, fructose, and sucrose is their sweetness, which varies depending on the specific sugar. Lactose (milk sugar) is the least sweet, whereas fructose is the sweetest sugar. Sugars are used as sweeteners in candies and many other food products.
Sugars contribute body and “mouthfeel” to foods. In other words, the addition of sugar makes a food more viscous or gives it a less runny consistency.
If sugar is replaced by a non-nutritive or high intensity sweetener such as aspartame or saccharin, the consistency of the food will be watery and
thin.
They are also metabolized by microorganisms.
This property is important in bread making, where sugar is fermented by yeast cells. The yeast feeds on the sugar, producing carbon dioxide,
which is the leavening agent and causes bread dough to rise before and during baking
At high concentrations, sugars prevent growth of microorganisms, because they reduce the water activity of food to a level below which bacterial growth cannot be supported. Sugars can, therefore, be used as preservatives. Examples of foods preserved in this manner include jams and jellies.
What are reducing sugars?
Sugars that contain a free carbonyl group are known as reducing sugars.
All monosaccharides are reducing sugars.
Disaccharides are reducing sugars only if they contain a free carbonyl group.
Involved in Maillard Reaction.
Which disaccharides are reducing sugars and which are not?
Sucrose is not a reducing sugar because it does not contain a free carbonyl group. The carbonyl groups of glucose and fructose are both involved in the glycosidic bond and are, therefore, not free to take part in other reactions. Maltose, on the other hand, has one carbonyl group involved in the glycosidic bond, and the other carbonyl group is free; thus, maltose is a reducing sugar.
What is sugar inversion?
During the digestive process the sucrose molecule is broken down into the two monosaccharides, glucosee and fructose, which can be easily absorbed.Invert sugar: An equimolar mixture of glucose and fructose, formed by hydrolysis of sucrose, either by acid and heat, or by enzymes such as invertase or sucrase.
Sucrose+ water= hydrolysis = Glucose + Fructose
This is called sugar inversion.(Convert to Monosaccharides)
Sugar inversion is specific to sucrose.
Explain Enzymatic and Non-enzymatic Brownings
Enzymatic Browning
non-desirable oxidation reaction that occurs in foods mainly fruits and vegetables.
Enzyme Responsible for this reaction is polyphenol oxidase.In the presence of PPO enzyme changes substances known as phenolic compounds through oxidation to quinones.
Non Enzymatic Browning
Maillard Reaction and Caramelization.
What is Caramelization?
Browning reaction that can occur with any kind of sugar.
As sugar is heated, water leaves its molecule in the form of Hydrogen and Oxygen. The new molecules have a higher concentration of carbon, creating the distinctive caramel colour.
Sucrose, galactose, and glucose all caramelize at 170°C.
Fructose on the other hand, caramelizes at 110°C
In the first step of caramelization, water evaporates from the sugar. Next, the sugar starts to break down into smaller compounds. Sucrose, for example — also known as table sugar — breaks down into glucose and fructose. From here, like in the Maillard reaction, there’s a condensation process. During this step, the individual sugar compounds react with one another to form hundreds of complicated aromatic compounds. These compounds are what give caramelized foods their signature sweet and nutty taste.
What does sucrose break down to in Caramelization?
Sucrose breaks down into glucose and fructose first. Then it breaks down further into acetic acid which is sour,maltitol has a caramel taste,furan gives a nutty taste.
Explain Maillard Reaction
The marriage of high heat, amino acids, and sugar is responsible for the Maillard reaction. Although it doesn’t seem as if foods such as bread or meat would have sugar in them, even the most savory foods have these naturally occurring carbohydrates.
In the first stage of the reaction, a reducing sugar, such a glucose, condenses with a compound that contains a free amino group, and a chain of amino acids that make up a protein. From there, the sugar-amino acid reaction forms the Amadori rearrangement product, the beginning of a series of more complicated organic reactions.
The product is then the beginning of a series of more complicated reactions.
Show an example reaction between glucose and a amino group.
LOOK IT UP LMAO.
What are the factors that favour Maillard reaction?
High sugar content • High protein concentration • High temperatures • High pH • Low water content
How does sugar crystallization occur?
Water evaporates, increasing the concentration of sugar in the solvent. When sugar reaches a certain concentration, crystallization occurs.Crystallization from a supersaturated solution begins when particles enter the solution (anything even dust)
The size of the crystals depends on how many particles are present and how quickly the crystals grow around them
Why does sugar dissolve in water?
Sugars form molecular solutions due to
hydrogen-bond interchange. When sugar is placed
in water, the water molecules form hydrogen
bonds with the sugar molecules, thus hydrating
them.
How can a supersaturated solution be obtained?
Solubility increases with temperature; thus, a hot
sucrose solution may contain more solute than a
cold one. If a hot saturated sucrose solution is cooled
without disturbance, it will supercool, and a
supersaturated solution will be obtained.
A supersaturated solution contains more solute
than could normally be dissolved at that temperature.
It is unstable, and if stirred or disturbed, the
extra solute will rapidly crystallize out of solution.
What is sugar hydrolysis and give an eg?
Splitting of a compound into smaller parts by the addition of water
This reaction breaks down carbohydrates until they yield the sugars from which they are formed
Glucose syrup is a food syrup, made from the hydrolysis of starch. Glucose syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor.
Sucrose+ water= hydrolysis = Glucose + Fructose
What is a starch granule?
Starch granules– discrete, spherical aggregates of starch – contain
amylopectin (branched polysaccharaide) + amylose (unbranched polysaccharide)
The arrangement is relatively ordered – crystalline
What is starch gelatinisation?
Starch gelatinisation – when starch is heated with water to the gelatinization temperature, water molecules enter granules, bond between amylose and amylopectin loosened, amylose dissolves out into water, granules swell to produce
a starch paste – thick viscous liquid
Why is starch gelatinisation limited in bread baking?
During the bread baking process, gelatinization of the starch takes place during the oven stage. However, the extent of gelatinization is limited due to the limited amount of water that is present.
