Chapter 1: food and nutrition Flashcards
Factors that affect food choices (9)
culture nutritional awareness families lifestyle Finance food availability sensory aspects health status marketing
Culture(3)
Food traditions of a country
Religious beliefs and values
Travel and immigration
Nutritional awareness(3)
People are more nutritional conscious due to the work of Bord Bia and the Health Promotion Unit
People check the nutritional labelling of products in order to avoid certain foods
Companies now place specific nutritional information on packaging
Families(3)
children’s food choices are influenced by watching what their family eats so parents should set a good example
Parents should cook with kids and show them how to read nutritional labels to teach them good nutrition
Children’s food choices depend on what is provided at home, processed foods should be avoided and fresh fruit and veg should be provided
Lifestyle(3)
Influenced by work, school and activities
A busy lifestyle causes greater reliance on convenience foods as they are quick to cook
A busy lifestyle can also prevent families eating together
Finance(3)
Families on low incomes may have to choose highly processed foods or may have to opt for cheaper cuts of meat
Families should plan and shop wisely
Greater income families can spend more money on food
Food availability(2)
Fruit and veg may not be in season so frozen or canned may be used
People in rural places may not have access to the same foods as people living in urban areas
Sensory aspect of food choice(3)
The senses, especially sight, smell and taste have a major role to play in food choice
Consumers have expectations about the temperature, colour, appearance etc of food often established in childhood
If food doesn’t meet these expectations they will not choose the food
Health Status and Food Choices(3)
Some people are on restricted diets e.g diabetic
Medical conditions such as heart disease
Food allergies
Marketing(1)
Marketing strategies e.g sweets at the checkout and advertising on tv influence food choices
Classification of minerals (2)
Macro minerals-
-required in relatively large amounts e.g calcium. phosphorus, potassium and sodium
Trace minerals-
-required in trace amounts e.g iron, zinc, iodine and flourine
Sources of calcium(6)
- Milk
- Cheese
- Sardines
- Yogurt
- Leafy green vegetables
- sesame seeds
Reference intake of calcium
Children/adults
-800mg
Adolescents/Pregnant or lactating women
-1,200mg
Functions of calcium (3)
- Strong bones and teeth
- Assist blood clotting
- Normal muscle contraction
Effects of deficiency (6)
- Osteoporosis
- Osteomalacia
- Rickets
- Tooth decay
- Slow blood clotting
- Muscle spasms
Factors assisting calcium absorption (5)
Vitamin D
-stimulates the production of calcium-binding protein
Parathormone
-a hormone released from the parathyroid gland which controls the levels of calcium in the blood
Oestrogen
-a hormone produced in the ovaries which promotes calcium absorption
Phosphorus
-combines with calcium, creating calcium phosphate which is easier to absorb
An Acid Environment
-an acid environment promotes calcium absorption, consuming foods high in vitamin C provides this
Factors hindering calcium absorption (6)
Tannins
-found in tea and coffee and bind to calcium inhibiting absorption
Excess dietary fibre
-binds to calcium inhibiting absorption
Excess fat
-binds with calcium, creating insoluble and non-absorbable calcium soaps
Excess protein
-as excess protein is burnt it produces sulphate which increases the amount of calcium excreted in urine
Phytic acid
-found in wholegrain bread and seeds and binds to calcium inhibiting absorption
Oxalic acid
-found in rhubarb and spinach and binds to calcium, inhibiting absorption
What three elements make up lipids
- hydrogen
- carbon
- oxygen
Into what two structures are lipids arranged
- Glycerol
- fatty acids
How is a lipid made
A lipid is made when three fatty acids combine with one glycerol
What is the new structure called when a glycerol combines with three fatty acids
Triglyceride
What is released at each join in a triglyceride
Water
What is the chemical structure of glycerol (2)
Glycerol is a structure with three hydroxyl groups
-refered to as a trihydrate alcohol
H | H-C-OH | H-C-OH | H-C-OH | H
What is the chemical structure of a fatty acid (3)
- A chain of carbons with hydrogens attached
- One end is called the carboxyl end
- The other end is called the methyl end
What is the chemical structure of a fat (4)
- A fat is formed when a hydrogen atom from the carboxyl end of a fatty acid joins with the hydroxyl group of a glycerol
- This happens for each of the three fatty acids
- The water is released at each join
- This is a condensation reaction
Classify fatty acids (3)
- saturated fatty acids
- monounsaturated fatty acids
- polyunsaturated fatty acids
List the characteristics of saturated fatty acid (6)
-Each carbon atom has its full quarter of hydrogens
-There are no double bonds present between the carbon atoms
-They are generally solid at room
-They are generally from animal sources
Contribute to the buildup of cholesterol on the arteries
-High melting points
-Examples include butyric acid in butter and stearic acid in meat
List the characteristics of monounsaturated fatty acids(7)
- Each carbon atom has not got it’s full quota of hydrogens
- There is one double bond present
- These fatty acids are soft or liquid at room temperature
- The originate from plant sources
- They don’t contribute to the buildup of cholesterol on the arteries
- They have a low melting point
- Examples include oleic acid found in olive oil
List the characteristics of polyunsaturated fatty acids(7)
- Each carbon atom has not got it’s full quota of hydrogen
- There is more than one double bond
- These fatty acids are soft or liquid at room temperature
- They originated from plant or marine sources
- They do not contribute to the buildup of cholesterol on the arteries
- They have a low melting point
- Examples include linoleic acid found in corn oil linolenic acid in vegetable oil and seeds and arachidonic acid found in oily fish
What are essential fatty acids (2)
These cannot be manufactured in the body and must be supplied by the diet
Examples include linoleic acid in corn oil
List the functions of the essential fatty acids(4)
- Build cell membranes
- Counteract the hardening effect of cholesterol on the arteries
- Helps prevent coronary heart disease as they raise raise hdl cholesterol in the blood
- Sources include nuts, seeds and fatty acids
List the characteristics of Omega-3 fatty acids (4)
- They are polyunsaturated fatty acids
- Omega-3 related to the positioning of the double bond
- The double bond is between the third and fourth carbon counting from the methyl end
- Sources include oily fish, salmon, herring, mackerel, nuts, soya beans, supplements
Benefits of Omega-3 fatty acids(3)
- reduces the risk of heart attack, stroke, circulatory diseases and formation of blood clots
- increases hdl cholesterol levels
- it is also associated with healthy brain activity and fetal brain development
What are cis and trans fatty acids
Cis and trans fatty acids are based on the position of the hydrogen atoms at the double bond of an unsaturated fatty acid
Describe cis fatty acids(3)
- Cis fatty acids occur when the hydrogen atoms on either side of the double bond are both above or below the carbons
- All naturally occurring unsaturated fatty acids are cis fatty acids
- Cis fatty acids do not cause cholesterol to build up on the arteries
Describe trans fatty acids (4)
- Trans fatty acids occur when the hydrogen atoms on each side of the double bond are on opposite sides
- This structure makes them behave like a saturated fatty acid
- They don’t occur naturally but are formed from cis fatty acids when they are heated and during processing of cis fatty acids
- Tests have shown that they raise the level of the LDL lipoproteins and reduce HDL or good cholesterol
Functions of fats(5)
- Heat and energy
- Protection of delicate organs
- Provision of the fat soluble vitamins A,D,E and K
- Essential fatty acids- formation of cell membranes and counteracts the hardening effects of cholesterol on the arteries
- Omega 3-improves brain activity, prevents certain cancers, prevents against coronary heart disease and strokes etc
Ill effects of fats (3)
- Excess fat is stored as far which can lead to obesity
- Excess fat can inhibit calcium absorption leading to osteoporosis
- Blocks arteries which can lead to heart attack, stroke or coronary heart disease
Properties of lipids - Solubility (2)
- Lipids are insoluble in water
- Lipids are soluble in solvent e.g ether or benzene
Properties of lipids - hydrogenation (3)
- The process of forcing hydrogen through the double bond of an unsaturated fatty acids (nickel catalyst)
- The unsaturated fat now becomes saturated (liquid to solid)
- This property is evident in the production of margarine (culinary application)
Properties of lipids- plasticity (2)
- Lipids can have properties of both a solid(saturated) and a liquid(unsaturated) fat.
- Margarine is used in the creaming method as it has shape and structure but are soft and spreadable
Properties of lipids (affected by heat) (melting point) (2)
- Solids melt when heated
- Fats melt at 30-40°C
Properties of lipids (affected by heat)(smoke point)(5)
- Lipids begin to decompose and the glycerol separates from the three fatty acids
- A blue haze emerges
- An acrid smelling compound known as acrolein is present
- Fats reach smoke point at 200°C
- Oils reach smoke point at 250°C
Properties of lipids (affected by heat)(flash point)(4)
- The decomposition of the lipids continues
- Lipids spontaneously burst into flames
- Fats reach flash point at 310°C
- Oils reach flashpoint at 325°C
Properties of lipids (rancidity) (6)
- This is the term used to describe lipids when they “go off” (results in an unplreasant odour and taste)
- There are two types of rancidity (oxidative and hydrolytic)
- To prevent rancidity, store food correctly (fats in the fridge and oils in a cool dark place) and manufacturers of fatty foods use an anti-oxidant
- Anti-oxidants occur naturally in vitamins A,C and E and artificially in BHA and BHT
- Anti-oxidants are widely used in the food industry to prolong shelf life
- They are found in foods like biscuits, cooking fats, dairy spreads, stock cubes and oil
Oxidative rancidity (3)
- This form of rancidity occurs when oxygen is forced through the double bond of an unsaturated fatty acid
- It is the most common form of rancidity
- Examples include oil solidifying on a pan
Hydrolytic rancidity (4)
- This form of rancidity occurs when enzymes and bacteria react with the lipid
- It results in the triglycerides breaking down(glycerol separates from the fatty acids)-flavour is altered
- This occurs most commonly in freezers when enzymes are not destroyed
- Occurs in both saturated and unsaturated fats
Properties of lipids (emulsions) (3)
- When two immiscible liquids are forced together, an emulsion is formed
- The emulsion can either be permanent or temporary
- There are two types of emulsions: oil in water e.g. milk and water in oil e.g butter
A permanent emulsion (1)
Occurs when oil and water are forced together permanently in the presence an emulsifier, e.g. mayonnaise (oil and vinegar and emulsifier (lecithin in egg yolk equals an emulsion)
A temporary emulsion (1)
Occurs when oil and vinegar are forced together, e.g. french dressing - this is caused by shaking and will separate again when standing
Emulsifiers (3)
- An emulsifier has two parts: a water loving head (hydrophilic) and a water hating tail (hydrophobic)
- The hydrophilic head attaches to water/vinegar while the hydrophobic tail attaches to the oil
- The oil and vinegar/water will not separate
Culinary application of emulsifiers (5)
- The making of mayonnaise
- Mayonnaise is made from oil and vinegar which don’t mix
- An egg yolk is added in because it contains lecithin a natural emulsifier
- The vinegar sticks to the head and the oil sticks to the tail
- As a result they don’t separate
Digestion of lipids- what happens in the mouth (1)
-Food is chewed
Digestion of lipids- what happens in the stomach (1)
-The heat of the stomach melts the fats which increases the surface area for digestion
Digestion of lipids- Duodenum (2)
- This contains bile from the liver which emulsifies the fats
- It also contains pancreatic juice from the pancreas which contains an enzyme called lipase. This lipase starts to break fats into fatty acids and glycerol
Digestion of fats- Ileum (1)
- Contains intestinal juices which also contain lipase which finishes the breakdown of fats into fatty acids and glycerol
Absorption of lipids(4)
- The fatty acids and glycerol pass through the walls of the villi
- From here they pass into the lymph system
- The fatty acids and glycerol are then carried in the lymph up as far as the neck and are then deposited into the blood stream up at the left side of the neck in the subclavian vein
- The blood now brings the digested fat back to the liver
Utilisation of lipids- oxidisation in the liver and muscles (2)
- In the liver and muscles lipids are oxidised to;
- produce heat and energy
- form cell membranes
Utilisation of lipids- storage of excess fat in the adipose tissue under the skin
- Excess fat is removed out of the liver and is stored as adipose tissue underneath the skin, this;
- insulates the body
- acts as an energy reserve
- protects the delicate organs
What are proteins made up of?
2
- they are made up of amino acids
- joined together
How many amino acids are there?
1
-twenty
What four main elements make up an amino acid?
4
- carbon
- hydrogen
- oxygen
- nitrogen
What three elements are only sometimes found in amino acids?
3
- iron
- phosphorus
- sulphur
What is the structure of an amino acid?
6
- a carbon(C)
- connected to a
- hydrogen(H)
- amino end (NH2)
- carboxyl end (COOH)
- and a variable (R)
What is the structure of the amino acid glycine?
6
- a carbon(C)
- connected to
- hydrogen (H)
- amino end (NH2)
- carboxyl end (COOH)
- and a second hydrogen (H)
What are essential amino acids?
5
- these are amino acids
- that cannot be made naturally by the body
- they have to be obtained by food
- foods which provide them are called high biological value foods
- there are eight essential amino acids
What are non-essential amino acids?
3
- these are amino acids that the body can make
- they do not have to be obtained from food
- there are twelve of them
List the essential amino acids
8
- Valine
- Lysine
- Leucine
- Isoleucine
- Phenylalanine
- Methionine
- Threonine
- Tryptophan
List the non essential amino acids?
12
- Alanine
- Aspartic acid
- Cysteine
- Ornithine
- Serine
- Asparagine
- Proline
- Tyrosine
- Glycine
- Glutamic acid
What are the structural functions of proteins?
6
- production of cell membranes,
- muscle tissue
- and skin
- cell repair
- and replacement
- growth
What are the physiologically active functions of proteins?
5
- hormonal proteins: help to coordinate bodily activities e.g. production of insulin
- enzymes: speed up chemical reactions, e.g. pepsin speeds up the breakdown of proteins into food
- antibodies (Immunoglobulins): defend the body from harmful substances, e.g. viruses
- blood proteins: move molecules around the body e.g. haemoglobin transports oxygen through the blood
- nucleoproteins (DNA): make up the hereditary material in chromosomes
What are the nutrient factors of proteins?
- provide the body with essential amino acids
- excess can be used as a source of energy when carbohydrate and fat reserves are used
How is a protein formed?
6
- proteins are formed when two or more amino acids join together
- this join is called a peptide bond
- a water is lost at each join
- the carboxyl end of one amino acid joins with the amino end of the next with the loss of a water
- the carboxyl end loses an OH where as the NH2 amino end loses a H
- the resulting bond(the peptide bond) is CONH
Explain the primary structure of a protein
3
- this is the number and sequence of amino acids in the polypeptide chain
- each of these are held together by a peptide bond(next you explain how a peptide bond is formed)
- e.g. insulin has 51 amino acids
Explain the secondary structure of a protein
4
- this is the further linking of the polypeptide chain with extra bonds or links
- it gives the protein a definite 2 dimensional shape (normally spiral)
- the links are called cross links or cross bonds
- two specific examples of cross bonds are disulfide bonds and hydrogen bonds
Explain a disulfide bond of a protein
4
- this is where two amino acids containing the elements sulphur link together
- an example of an amino acid that contains sulphur is cystine
- the two sulphurs in the two cystines link together with a bond called a disulphide bond
- as a result of these disulphide links the chain coils into a two dimensional spiral shape
Explain a hydrogen bond in a protein
3
- these bonds occur when a hydrogen from one amino acid joins with an oxygen of another amino acid
- this can occur on the one chain or between two neighbouring chains
- a spiral shaped protein also results
Explain a tertiary bond in a protein
5
- this is the further folding and linking of the secondary structure
- to give the protein a three dimensional shape
- (normally fibrous or globular)
- more cross links form to hold it in place
- it is only now that it starts to function as a protein
Deficiencies associated with protein
5
- retarded growth
- delayed healing of wounds
- susceptibility to disease and infection
- lack of energy
- kwashiorkor and marasmus in severe cases
Classification of proteins
2
- simple proteins
- conjugated proteins
What are simple proteins
2
- these consist of only amino acids along the chain
- they can be further broken down into amino and plant proteins
What are the two groups of simple proteins
2
- animals
- plant
What are the animal simple protein subgroups
2
- fibrous
- globular
What are the plant simple protein subgroups
2
- glutenins
- prolamines
What are examples of fibrous simple proteins
2
- elastin
- collagen
What is a source of the fibrous simple protein elastin
1
-meat connective tissue
What is a source of the fibrous simple protein collagen
1
-meat connective tissue
What are examples of globular simple proteins
2
- ovalbumin
- lactalbumin
What are sources of the globular simple protein ovalbumin
1
-egg whites
What are sources of the globular simple protein lactalbumin
1
-milk
What are examples of glutenin simple proteins
2
- glutenin
- oryzenin
What are examples of prolamine simple proteins?
2
- gliadin
- zein
What are sources of the glutenin simple protein?
1
-wheat
What are sources of the oryzenin simple protein?
1
-rice
What are sources of gliadin the simple protein?
1
-wheat
What are sources of zein the simple protein?
1
-maize
What are conjugated proteins?
2
-somewhere along the chain of amino acids -there is a non protein molecule attached
What are lipoproteins?
1
-chain of amino acids with a lipid attached
What is an example of a lipoprotein?
1
-lecithin is a protein found in egg but it has fat present too
Explain the denaturation property of proteins.
5
-it is a change in the nature of a protein
-it causes the protein chain to unfold
-which leads to an irreversible loss in structure
-over this happens the protein often sets or becomes hard (coagulation)
-it is caused by;
Heat
Agitation
Chemicals
Explain how heat causes the denaturation of a protein
2
- causes the protein to harden and set
- e.g eggs
Explain how agitation causes the denaturation of a protein.
2
- whipping a protein food brings about partial coagulation
- e.g. an egg white becomes foam
Explain how chemicals cause the denaturation of a protein
2
- such as acids, alkalis and enzymes cause change in protein structure
- e.g. addition of lemon juice to eggs cause it to coagulate
What are the culinary applications of the denaturation property of proteins?
(1)
-useful in the making of sponges and quiches
Explain the mallard reaction property of proteins.
3
- this is the non-enzymic browning of protein foods
- it occurs when an amino acid reacts with a carbohydrate
- under dry heat
What are the culinary applications of the mallard reaction property of proteins.
(2)
- it gives a nice brown colour
- to roast potatoes, roast meat and shortbread biscuits
Explain the gel formation property of proteins
4
- a gel is a semi-solid, viscous solution in which water molecules are trapped
- gelatine is made from the protein collagen and it can absorb large amounts of water to form a gel
- if this is heated it forms a sol and on cooling the sol becomes semi-solid
- this process is called gel formation
What are the culinary applications of the gel formation property of proteins?
(1)
-the setting powder is used in making cheesecakes and souflees and jellies
Explain the foam formation property of proteins
4
- when an egg white is whisked the 3-D protein structure unfolds(denatures)
- air bubbles become trapped within the unfolded chains creating a foam
- the whisking action also generates a little heat which sets the egg white slightly (temporary foam)
- to hold it in this state it needs to be put into an oven
What are the culinary applications of the foam formation property of proteins?
(1)
-the making of meringues
Explain the elasticity property of proteins
1
-some fibrous proteins e.g. gluten in wheat, are quite elastic
What are the culinary properties of the elasticity property of proteins?
(1)
-gluten makes yeast dough elastic enough to trap the CO2 gas produced by yeast, helping it to rise
Explain the solubility property of proteins
3
- most proteins are insoluble in water,
- apart from collagen in meat (soluble in hot water)
- and egg albumin (soluble in cold water)
What are the culinary applications of the solubility property of proteins?
(1)
-moist heat tenderises meat by converting collagen to elastin
What is the biological value of a protein?
4
-it is the measure of the quality of protein
-it is expressed as a percentage
-it is determined by the number of essential amino acids present in the food
-there are two groups;
high
low
What is a high biological value protein?
4
- contains nearly all the essential amino acids in the correct proportions
- e.g. eggs have 100 percent
- also known as complete proteins
- generally come from animal sources but also the soya bean
What is a low biological value protein?
4
- contains only some of the essential amino acids
- also known as incomplete proteins
- come from plant sources but also gelatine
- e.g. rice has 67 percent
What is complementary rate/ supplementary value?
6
- consuming two LBV protein foods together, each different essential amino acids are obtained
- e.g. beans and toast
- beans are low in methionine and high in lysine
- toast is low in lysine and high in methionine
- by eating beans and toast together all essential amino acids are got
- useful in the diet of vegetarians
Describe the breakdown of proteins during digestion
4
- protein to
- peptones to
- peptides to
- amino acids
How are proteins broken down in the stomach?
4
- the secretion of gastric juice
- which contains the enzymes rennin and pepsin
- act on caeseinogen proteins(substrate)
- to make casein peptones
How are proteins broken down in the pancreas?
4
- pancreatic juice is secreted into the duodenum
- along with the enzyme trypsin
- act on peptones(substrate)
- to make peptides
How are proteins broken down in the small intestine (ileum)?
4
- the secretion of intestinal juice
- along with the enzyme peptidase(erypsin)
- act on the substrate peptides
- to make amino acids
What are hormonal proteins?
2
- these help to coordinate bodily activities
- e.g. production of insulin
What are enzymes?
2
- these speed up a chemical reaction
- e.g. pepsin speeds up the breakdown of proteins in food
What are antibodies?
3
- also called immunoglobulins
- they defend the body from harmful substances
- e.g. viruses
What are blood proteins?
2
- these move molecules around the body
- e.g. haemoglobin transports oxygen through the blood
What are nucleoproteins
2
- also called DNA
- these make up the heredity material in chromosome
What are the effects of dry heat on proteins?
2
- maillard reaction
- e.g. roast beef
What are the effects of moist heat on proteins?
4
Tenderising Meat
- collagen in meat converts to gelatine
- causing the fibres to tenderise
- e.g. pulled pork
What are the effects of both dry and moist heat on protein?
3
Coagulation:
-e.g. egg whites coagulate at 60 degrees Celsius and egg yolks at 68 degrees Celsius
Colour Change:
-e.g. myoglobin (red pigment) in meat changes to haematin (brown pigment)
Overcooking:
-causes proteins to become indigestible
Describe the absorption and utilisation of amino acids
5
- amino acids pass through the walls of the villi
- the villi past them into the portal vein and are brought to the liver
- in the liver they are used to maintain and repair liver cells
- summer released back into the bloodstream again and they brought around the body to form new cells, repair damaged cells and manufacture hormones enzymes antibodies in DNA
- the excess is deaminated to produce heat and energy
Describe protein deamination
4
- the breakdown of excess protein in the body and using it as a source of energy
- 16 occur in the liver
- the amino end is removed from the amino acid and is changed into ammonia and then into urea and is excreted by kidneys as urine
- the carboxyl end is removed and oxidized to produce heat and energy
Classify Vitamins
2
- fat soluble vitamins
- water soluble vitamins
What are fat-soluble vitamins?
2
- normally found in food that contains fat
- can be stored in the liver for several months
List the fat-soluble vitamins
4
- vitamin A
- vitamin D
- vitamin E
- vitamin K
What are water-soluble vitamins?
3
- found in a wide variety of foods
- not stored in the body
- the excess is excreted
List the water soluble vitamins
2
- vitamin C
- B group vitamins
What are the two forms of vitamin A?
2
- retinol (pure vitamin A)
- beta-carotene (pro-vitamin A)
What is retinol (pure vitamin A)?
2
- easily absorbed
- stored in the liver
What is beta-carotene (pro-vitamin A)?
2
- not easily absorbed
- converted to retinol in the lining of the intestine
What are the properties of retinol (pure vitamin A)?
5
- a yellow, fat-soluble alcohol
- insoluble in water
- soluble in organic solvents, e.g. acetone
- heat stable, but affected by prolonged high temperatures
- destroyed by oxygen
What are the properties of beta-carotene (pro-vitamin A)?
6
- a yellow or orange fat-soluble oil
- insoluble in water
- soluble in fat solvents, e.g. alcohol
- heat stable, but affected by prolonged high temperatures
- unaffected by oxygen
- a powerful antioxidant which counteracts the damaging effects of free radicals and can prevent certain cancers, aging of the skin and heart disease
List some sources of retinol (pure vitamin A)
8
- fish liver oils
- milk
- eggs
- butter
- offal
- cheese
- margarine
- oily fish
List some sources of beta-carotene (pro-vitamin A)
6
- carrots
- tomatoes
- red peppers
- leafy green vegetables
- apricots
- sweet potatoes
What food sources provide retinol (pure vitamin A)?
1
-found in animal food sources
What food sources provide beta-carotene (pro-vitamin A)
2
- found in yellow, green and orange fruit and vegetables
- carotenoids
List the functions of vitamin A
5
- manufactures the pigment rhodopsin
- healthy skin and mucous membranes
- healthy skin and hair
- aids growth and development of children
- powerful antioxidant