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Food Science.


1.     Carbohydrates should be 55-60% of energy

Plants by photosynthesis (monosaccharide-glucose, polysaccaride, disaccarides malt-lact-sucrose)

Starch - main food reserve, 2 types of glucose polymer - amylose linear+amylopectin-branched

Cellulose - 10k glucose units

2.     Fats 30%

Belong to lipids, glycerol esters

Essential fatty acids - linoleic, linolenic, unsaturated

It dissolves vitamins, protects thermally and physically

Hydrogenating with Ni cat. 180C, H2 bubbled through, makes harder and stable

Degree of unsaturation iodine value (g to saturate 100g), Wij solution - ICl

3.     Proteins 10-15%

a.     Primary structure - amino acids linked by peptide bonds, 8 essential

b.     Secondary structure - a-helix with H-bonds

c.     Tertiary structure

i.      Fibrous - insoluble in H2O, resistant to pH+t

Elastic - mycosine(muscle),wool

inelastic - cross links, e.g. fibrin (collagen)

ii.     Globular - soluble, affected by pH, e.g. egg albumin, casein, gelatine

Functions - structure (collagen in bones), food store(albumen), oxygen carrier, enzymes, buffers

Enzymes - destroyed on heating, inactive in extreme pH

4.     Mineral elements

a.     Part of body structure (CA in bones)

b.     Fluids in the tissues, buffers

c.     Component of enzymes

5.     Water - 60%

a.     Transport nutrients

b.     Take part in chemical changes in the tissues and during digestion

c.     Maintains tissue rigidity

6.     Vitamins

Retinol (A)               nicotinic acid(B), thiamin(B1), riboflavin(B2)

Ascorbic acid(C)      cholecalciferol (D)         Tocopherol (E)              (K)


Energy supply - CFP

Growth and repair of body - PMW

Control of body processes - PMWV

Body needs oxygen and energy, of basal metabolism 6700kJ/day

Experiment 2.7a Glucose content of drinks


1.     Fill a burette with 0.5% glucose soln.

2.     Put 25cm3 Benedichts with pipette to wide-mouth conical flask

3.     Add 10g anhydrous Na2CO3+ boiling stones

4.     Heat until NaCO3 has dissolved

5.     Titrate first rapidly then drop per 20sec until blue colour disappears, solution must boil, 1%methylene blue as indicator

6.     Repeat with liquid being investigated

0.5% Glucose



starting amount (A)

finishing amount (B)

amount needed to titrate(B-A)







Glucose drink

starting amount (A)

finishing amount (B)

amount needed to titrate(B-A)







Glucose is a reducing sugar and Benedichts reagent tests for organic reducing agents.

On average 12cm3 of Benedichts was used for 0.5%Glucose

9cm3 must be 25% more conc, so 0.675%

To measure sucrose we must boil with HCl for a while to convert sucrose to glucose.

Experiment 2.7 Vitamin C in cooked cabbage

Procedure 1 standardise indicator DCPIP

1.     Fill a burette with 0.04% DCPIP (0.4gdm-3)

2.     Put 25cm3 C(0.2gdm-3) with pipette to wide-mouth conical flask, blue colour of the dye turns colourless because of C, when finished turns red (10sec) because acidic cond.

3.     Blank titration 25cm H3PO4 must give same result

Calculation + result 8cm3

Dye factor F=mg of C per 10cm3 dye = 50mg was 8cm3, 5.125 per 1cm3

Procedure 2 uncooked cabbage

1.     Liquidize 50g of cabbage with 250cm3 5% H3PO4 and make up to 500cm3. H3PO4 is used because it inactivates enzyme and dissolves C better and does not destroy it

2.     Titrate 25cm3 of it.

Calculation Result 5.5cm3

100g contains 5.5x5.125x300x2/25=338.25mg/50g

In cooked cabbage

1.     Simmer 50g in 100cm3 of water(little water to avoid loss, but more C is destroyed, because enzyme is not destroyed fast enough) for 10 mins

2.     Titrate as above - 2cm3, so loss 64%

Eating Qualities

1.     Structural character
a.     water holding capacity

1.     Small amount of water is chemically bonded to polar protein groups

2.     Some held by hydration of Mg2+ Ca2+ in the proteins and in free form

3.     Most is free held immobile by long chains of h-bond linked proteins to form a meshwork. Gels have trapped large amount of water, GEL.

b.     texture
c.     tenderness
d.     juiciness
2.     Chemical Character
a.     taste-bitter(Ca, quinine, caffeine), salt, sour(citric acid), sweet(sucrose, saccharin)
b.     odour - volatile compounds
c.     colour - porphyrins (chlorophyll, fades when heated-NaHCO3 added, haemoglobin), carotenoids(fat soluble long chain yellow to red), anthocyanis(H2O soluble, all colour)


Cells are surrounded by cell membrane - layered structure made up of lipids and proteins - lipoprotein, called plasmalemma. Electrostatic attraction, selectively permeable.

Firmness is due to turgor pressure (water pushing out), the strength of cell wall, efficiency of adjacent cell placement. Wall is microfibrils embedded by pectin to matrix.

Pectin is most easily affected. It consists of galacturonic acid and little rhamnose. If acid is ester matrix is weaker. When heated pectin becomes H2O soluble.

Animal muscles

Skeletal (normal), cardiac(heart), smooth(surrounds organs)

Connective tissue proteins contributing to structure are collagen(polypeptide chains in triple helix that stand side by side to form fibrils) and elastin(can roll like ball).

Each muscle fibre consist of myofibrils |actin(I) myosin(A) actin|zline|sacromere|

A-thick filaments of myosin polymer(connected to Z by titin), I-thin filaments of actin.

When animal dies rigor mortis occurs, so it is allowed to stand couple of days (tenderisation due to enzyme calpain or added papain (found in fruits))

Experiment 3.7a Ca ions effect on texture

Soak beans in H2O, tap water 2%CaCl2, 4% CaCl2

Boil in 100cm3 for 10mins and taste

Soaked in


Tap water


4% CaCl2





very hard

Experiment 3.7b Taste + 3.7c tongue

Taste NaCl (A), citric acid (B), caffeine (D), sugar (C)

Use straw to put on your tongue

Types of Change

1.    Due to microbiological activity

a.     Moulds - most common, microscopic fungi, bad. Needs little humidity. pH4

b.     yeast - oval-shaped fungi, good. Needs a bit humidity.pH6.5

c.     bacteria - Cocci - spherical, Bacilli - rod shaped. Needs humidity. pH8.5

i.      Spoilage organisms - not harmful, lactobacillus

ii.     Pathogens - disease causing organisms

some pathogens cause food poisoning, other(salmonella) give rise to illness

Growing phases - lag, exponential,stationary & death. Contaminated when 107/g

Temperature division psychrophilic(10-15 H2O born), mesophilic(20-40 salmonella), thermophilic(55-65 spore forming)

Aerobic will grow in the presence of oxygen, anaerobic not.

i.      Salmonella enteritidis - causes diarrhoea, eggs, destroyed by heath.

ii.     Campylobacter jejuni - main UK food poisoning, cramps, diarrhoea. Raw chicken + milk.

iii.    Listeria monocytogenes - only old/young, causes meningitis, soft cheeses, heath sensitive.

iv.    Staphylococcus aureus - carried in the skin, releases heath-proof toxin

v.     Clostridium botulinum - soil+seawater, form spores, 50%mortality.

Cook fast at high t. consume quickly, do not hold long in refrigerator

2.    Biochemical reactions

Depends when harvested. Changes are due to enzymes.

E.g. pectin breakdown makes mushy.

3.    cooking or preserving

Microbiological changes in milk.

1.  Carbohydrate breakdown (souring, fermentation). Lactose to lactic acid+alcohols. Casein coagulates at low pH - Curdling leaving whey. Pasteurized milk spoils differently.

2.  Protein breakdown (proteolysis) - 1st amino acids, unpleasant smelling gas(H2S), "putrid"

3.  Fat breakdown (lipolysis) production of fatty acids+glycerol catalysed by lipases(soapy, rancid)

Beneficial changes - cheese manufacture - Acid production (by rennet), curd is obtained and heated and separated from whey, pressed into blocks and allowed to maturate.

Experiment 4.6a Which substances are involved in the browning reaction.

Wash apples with various benzenediols and water for control and look which goes brown.

Benzene-1,2-diol(A), Benzene-1,2,3-triol(B) do. Benzene-1,2-diol does it.

4.6b when browns

cut apple to pieces and smash apple, and break a piece, treat with diol. Cut and smashed surface browns quicker than broken or healthy. Pulping increases O supply and mixes enzymes&substrates.

4.6c is browning due to microorganisms

Microorganisms spoil faster. Microorganisms are not found inside apple. Not due to microorg.

Soak apple into phenol (kills microorganisms) and compare - no change in browning.

Temperature destroys enzymes - heated apple doesn't brown.

4.6d does it need air - quinone is formed from oxygen.

Put 3 samples in air, vacuum oxygen. One in O quickest, need oxygen for browning.

4.6e ascorbic acid prevents browning because reduces (antioxidant)

It does it in proportion to its conc. when used up browning occurs fast. C reduces quinone back, enzyme might lose its activity first. Ascorbic acid cannot restore colour, because irreversible reactions have occured.

4.6f controlling browning by inactivating enzyme

A-0.5M HCl, B-2% citric acid. C 3% NaHSO3 D 2% NaCl F boiling H2O. All prevent

Enzyme active pH 6-8. Citric acid occurs naturally and doesn't affect taste. SO2 is an enzy. inhibitor

Browning control:

1.  Reduce concentration of substrate by selecting apples or genetically

2.  Excluding oxygen+adding antioxidant

3.  Inactivating enzyme by heating, adjusting pH, adding inhibitors, altering conc. of reaction soln

4.7a making curd from milk

1.     heat 4 boiling tubes in water-bath to 37C

2.     Add enzymes and measure the time for curd to form






1.50 min





4.7b making whey syrup

1.     2cm lactose enzyme+8cm Na alginate, mix and draw to a syringe

2.     Drop solution into 100cm 0.1M CaCl2 to form beads. Wait 2min

3.     collect and wash beads with water

4.     pour into syringe

5.     Pass whey solution (50cm3) through and test for glucose

Glucose conc. is slowly increasing. I can use column again coz enzyme is not used.

I can make a quantitative determination of the glucose conc by Benedichts.

Food preservation methods

1.    Destroying or inactivating some/all microorganisms/enzymes

a.     Heat processing - effectiveness depends of pH >4.7 5hours, 4.5-3.7 short treatment causes no microorganisms, <3.7 very short.

i.      Sterilisation - kill everything. Inpack and ultrahigh t.(UHT)

For fruit 80C 3min for enzymes, food into clean containers, heated by steam. Long, microwaves cannot go through metal. UHT only for liquid. 140C 5sec, costly.

ii.     Pasteurisation - kill most pathogenic high temp short time(HTST) 72 15sec to avoid cooked flavour.

b.     irradiation - reduces nutritional value, no radiation for food

c.     chemical techniques - preservatives with E

d.     high pressure - acid food, 5000atm, fresh taste

e.     Acid - either by microorganisms or ethanoic acid added(vinegar) weakly dissociated acids are better preservatives (sorbic, benzoic)

f.     Salt (curing) - meat in 25% NaCl, 0.001%NaNO2 1%NaNO3 12 days, also smoked

g.     Antibiotics - bacteria might get resistant, only nisin allowed

h.     Antioxidants - reduce oxidation of fatty acids, vitamin E,C, propyl gallate. Synergists(citric acid) improves action by forming complexes with metals catalysing oxidation.

2.    Creatin conditions that limit deterioration

a.     Freezing - reduces rate of growth, makes H2O unavailable

i.      Blast -30-40C, fast less cell damage

ii.     Immersion - cold salt+glycerol. cyrogenic when liquid N2 used

iii.    Freezing by contact (plate freezer) - costly, only for fish etc.

b.     Dehydration - removal of 90% H2O, popular, freeze dried and heat dried.

c.     Packaging - protects against accidents, physical changes(dehydration), uptake of moisture, oxidation of fats. Material can be impermeable. Modified atmosphere(25%CO2) keeps meat red.

Cereal Science

Wheat grain -  107 tonne/year

1.     moisture - lower moisture grains more expensive, less storages better, before milling conditioning (10-15% moist) limits break-up and improves separation

2.     cellulose

3.     starch - largest, a-glucose polymer. Must be heated to eat(Hbonds break)-gelatisation.

4.     protein(12-14%) - protein quality is the physical characteristics of gluten. High level of protein - good yield of gluten - good for bread, but extensible gluten for cakes. Gluten - gliadins(30%), glutenins(60%, coiled protein subunits linked by disulphide links from oxidised cysteine). They are little ionic and are insoluble. When water is added dough is formed(stronger when more glutein).

Kjeldahl method determines protein content-grain digested in H2SO4, N2 leaves and is measured.

5.     some fat

6.     vitamins+minerals.

Processing wheat

Wheat to flour

1.     Conditioning to uniform moisture by adding H2O and leaving

2.     Gristing by blending together different wheats to adjust protein

3.     Milling and blending to produce required protein+colour(endosperm colour, particle size, bran contamination). Flour is broken by rolls to bran and endosperm.


1.     CaCO3 to increase Ca content in diet

2.     Vitamins and Fe

3.     Improvers (KBrO3) to control cross-linking

Flour to bread

1.     On heating starch granules in the flour swell and take up large amounts of H2O

2.     Soluble starch leaks out of granules and the suspension becomes more viscosious.

3.     Added yeast converts glucose>CO2+ethanol, that escapes, but CO2 is traped, makes to rise

Bread making properties improve with standing(unsaturated acids get oxidised by peroxides), whiter and more elastic(SH>SO3H). Nowadays flour is bleached with Cl or ClO2.

Good dough holds gas,  made by kneading(glutein is stretched linearly to break molecules, cystein exchanges disulphide). Improving agents become active when water is added(vit,C, oxidises SH). Ca is added.

In dough amylase is hydrolysed to maltose. Starch on heating will dissolve and take up H2O. Gelatinised starch is more readily hydrolysed by our body enzymes. Yeast is added to produce CO2 that is trapped by gluten, that later in high t coagulates. Salt is added to control rate of fermentation.

In UK Chorleywood Bread Process (instead of fermentation, high speed vacum, starch damage, soft crumb, fast, cheap)

6.7a Gluten test is SDS sedimentation

1.     50cm H2O into stoppered 100cm cylinder and add 6g of flour

2.     50cm SDS into a cylinder

3.     add flour to H2O + start timing

4.     shake after 2min for 15sec

5.     At 6 min add SDS and invert

6.     at 10 min leave safely till 30 min and look sedimentation - 36ml above 60 is strong

6.7b gelatisation temp.

10cm H2O + 0.5g starch into a test-tube

Heat in 50C, 60C, 65C, 70C 80C water-bath

investigate under microscope for breaks by taking samples by pipette and cooling.











yes, thick gelatin


6.7C flour colour and comparative test for flour improving

In Petri dish background slightly brown with dark dots. More brown when damp

Colour difference is due to phenol oxidase in the bran. Darkening is faster in warm because enzyme works better

Biscuits flour has no vitamins or iron, bakers' one does.

Pour 2%iodine solution over wet flour. Blue with white spots, because ascorbic acid reduces iodine to iodide.

Add thiocyanate to flour, red spots appear where iron is.

Food Legislation

1.     Necessary to prevent adulteration and contamination of food/food sources

2.     Prevent sale of low quality food

3.     establish and maintain compositional and nutritional standards

4.     prevent the use of nonbeneficial additives

5.     prevent misleading labeling and to promote informative labeling

a.     Adulteration of food and drink act 1860 - no impure or injurious food was allowed.

b.     Food Act 1938 - bad food was seized, misleading labelling and selling was an offence.

c.         Food safety Act 1990

1.     rendering food injurious to health(adding smth to food, using it as ingredient, abstracting anything from food, subjecting food to any treatment). If hypothetical customer might be affected.

2.     selling food failing to comply with requirements (injurious, contaminated, unfit)

3.     selling food other than demanded - if not the standard

4.     falsely presenting the food

Was made to comply with EU law. Ministers can issue codes under it. Enforcement responsibility of local food authorities. Act was made to take account changing technology.

Food Advisory Committee and EU help government continuously:

1.     Use of additives is closely monitored(must have advantages and no other way)

2.     Irradiation must bee said in label

3.     Claims are controlled

4.     Labeling is required

5.     Contact material

The hungry world

1.     Population growth

2.     inefficient production in some parts

a.     Water-3% is useable, unevenly distributed. Only 15% is irrigated, produces 30%.

b.     Farming methods - more literacy and knowledge. Pesticides and fertilizers (Integrated pest management).

c.     Biodiversity has decreased with bigger farms.

3.     unequal distribution - erosion

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