exam Flashcards
What percentage of fluid milk is comprised of water?
87-89%
Fluid milk is made up of water and?
- Carbohydrates
- Lactose
- Fat
- Protein
- Minerals (calcium, phosphorus, magnesium,
potassium, sodium, chloride & sulphur) - Water-soluble vitamins
(thiamine & riboflavin)
What is included in the term Solids-not-fat
lactose, caseins,
whey, proteins & minerals
What nutrients are found in milk?
Carbohydrate Protein Calcium Potassium Magnesium Zinc Phosphorus Vitamin A Vitamin B12 Riboflavin
Milk Composition as a % total volume (fats, non-fat-solids, water)
4%, 9%, 87%
What nutritional factors effect milk composition
- Type of feed
- Quality of feed
What non-nutritional factors effect milk composition (6)
- Breed
- Stage of lactation
- Season & temperature
- Age & size
- Disease
- Milking frequency
Milk Composition affects pricing of milk?
- No legislative control
- Milk prices based on the milkfat and protein solids
- “Farm gate” prices can vary between manufacturers, between states, &
among individual farmers - A range of incentive/penalty payments related to milk quality, productivity
and out-of-season supplies
What is the pyhisical appearance of milk?
- Opacity = due to suspended particles of fat,
proteins and certain minerals - Colour = white to slight yellow (carotene
content)
What is the osmotic pressure, freezing point, and pH of milk?
- isotonic
- -0.512°C to -0.59°C
- pH of fresh milk = 6.6 to 6.8
True or False?
Raw milk fresh from cow is almost sterile
True
True or False?
Most cows milked twice a day
True
What temperature is fresh raw milk immediately cooled to?
Below 5°C
What quality assurances of raw milk are taken?
- Standard temperature
- flavour & odour
- Composition
- Antibiotics
- Freezing point depression
- pH/ Acidity
How is Butterfat (BF) and solids-non-fat (SNF) analysed in raw milk?
-Amounts of BF & SNF in milk vary according to
time of year, breed of cow & feed supply
- BF & SNF content, and volume are used to
determine amount of money paid to produce
How do modern cream separators operate ?
using centrifugal separation by separating cream & skim portions of milk
What the are two streams produced during
separation or whole milk?
- fat-depleted stream = produces the beverage
milks; skim milk for evaporation & drying - fat-rich stream = cream = fat content of 35-
45%
What is “Plastic” cream (~80% fat content)
Remains an oil-in-water emulsion (= fat is still in
globules & skim milk is the continuous phase of emulsion…
unlike butter = also has 80% fat, but been churned, so fat
occupies continuous phase & skim milk is dispersed
throughout in the form of tiny droplets, i.e. a water-in-oil
emulsion)
How can protein be added to milk?
maybe done by adding permeate
filtrate/liquid passing through membrane
What is Pasteurisation?
- A process of heating raw milk to kill all pathogenic microbes that may be present - Its NOT sterilisation (= eliminates all viable, life-forms)
All milk must be pasteurised within how many hours?
72 hours
Some harmless bacteria may survive heating process in pasteurisation, what is done to slow the milk from going “sour”?
keeping milk refrigerated slows
growth of these bacteria
What is involved in Low-temperature longer time (LTLT)
pasteurisation?
- A batch method of pasteurisation
- Heats milk to at least 63°C & holds at this
temperature for at least 30 min OR 65°C for 15
min - Can cause a “cooked” flavour, so not always
used for fluid milk products
What is involved in High-temperature/short time (HTST) pasteurisation?
-A continuous method (a plate heat ex hanger) heating milk to 72°C for
at least 15 sec (commercially my be up to 75°C for 15 sec (for cream)
- Milk immediately cooled to below 4°C & packed into plastic bottles or
plastic-coated cartons
What is involved in Ultrapasteurisation?
Milk heated to above 135°C for 2 to 5 sec,
followed by rapid cooling to 7°C or lower
How is milk sterilised?
ultrahigh temperature (UHT) processing is used heating the milk up to 137°C - 150°C for 2 to 6 sec
If milk is un-homogenised will cream portion from a
layer at the top of milk in carton?
True
How is milk homogenised?
•Milk is forced under high pressure through
narrow gap
- Breaks up the butterfat globules to small sizes
- Such small globules will not coalesce (stick together)
•Nutrition or quality of milk NOT affected
In beverage milk, how much milk fat is in Regular or full-fat?
- contains on average between 3.2% to 3.8% milk fat
- a.k.a. full-cream or whole milk & has a rich & creamy
texture (~3.4% fat)
In beverage milk, how much milk fat is in Reduced-fat?
- contains ~2% milk fat
In beverage milk, how much milk fat is in Low-fat?
- contains >1.5% milk fat
In beverage milk, how much milk fat is in Low-fat?
Skim/no-fat:
- contains no more than 0.15% milk fat
- Milk solids (which are produced when water is removed
from liquid milk), are added to optimise the taste
What vitamins may be added to full fat &
reduced fat milks and why?
- Vit A & D (fat-soluble) often added
- Vit A lost during fat separation & heating, while
Vit D not present
What are some concentrated milk products that are obtained through partial water
removal?
Evaporated skim or whole milk; sweetened
condensed milk; condensed whey
What are some dried dairy products that have less than 4% water usually?
milk powder; whey power; whey protein
concentrates
What are the benefits of Concentrated & Dried Dairy Products? (4)
increased shelf life
convenience
product flexibility
decreased transportation costs & storage
What is Condensed Whey?
- Whey resulting from cheese making is condensed by
evaporation - Contains lactose, lactoglobulin, lactalbumin & water
- Fat generally removed by centrifugation & churned as
whey cream or used in ice cream
Various ingredients are blended together in mix tank
equipped with powder funnel & agitation system causing fortification of milk to increase milk solids-not-fat, why is this fortification important in yogurt production?
- Improves consistency (viscosity) & flavour
- Total solids ~14-15% for low fat yoghurts = mostly by adding
skim milk powder at 3-6% (can be higher due to added sugar,
fruit, etc) - Can concentrate milk by ultrafiltration to 18-20% solids
- Pectin or starch or gelatine added sometimes to increase
viscosity - Can use fat substitutes = replace milk fat with starch-based &
microparticulate protein-based fat substitutes
In yogurt production, what occurs when pasteurised?
- Varies = 85°C/30 min to 90-95°C/10-20 min
- Helps formation of casein network
- Increases gel firmness and decreases syneresis
(release of whey from gel) - Shortens coagulation time, increases pH at which
coagulation occurs
In yogurt production, what temperature is the yogurt homogenised and why?
At 50-60°C to improve viscosity & firmness of coagulum; Even dispersion of constituents, solids-non-fat & fat
In yogurt production the mixture is cooled to the optimum temperature for culture growth, what temperature is it cooled to?
40-45°C
What is the process of yogurt production?
- Milk receipt
- Adjust milk composition and blend ingredients
- Pasteurisation
- Homogenisation
- Cooled
- Inoculate with starter cultures
- Hold and cool
- Flavours and fruit added
- Packaged
Explain the starter cultures in yogurt production?
- Symbiotic blend of Streptococcus thermophilus (ST) &
Lactobacillus delbrueckii subsp. bulgaricus (LB) = ratio
~1:1 - ST grows faster & produces both acid & CO2 which
stimulates LB growth - Proteolytic activity of LB produces stimulatory peptides &
amino acids used by ST - Microbes ultimately responsible for typical yoghurt
flavour & texture - Streptococci drop initial pH to ~5.5
- Lactobacilli further decrease pH to ~4.5
- Incubated till firm gel forms (5-7 h)
What are the different yogurt types?
Set = incubated in container; additives such as fruit
sink to bottom
• Stirred = incubated in tanks; gel disrupted by
stirring, pumping, filling; additives well suspended
• Drinking type: similar to stirred type, but coagulum
is broken down to a liquid
• Frozen type: incubated in tanks & frozen like ice
cream
• Concentrated: incubated in tanks, concentrated &
cooled before being packed, Eg: Greek yogurt
• Plain/natural, flavoured, fruit
• With Probiotics
- Some now also contain ‘probiotics’ or ‘therapeutic’
starters = e.g. the ABC cultures:
L. acidophilus = a common human gut bacterium;
able to colonise gut (L. delbrueckii subsp. bulgaricus cannot)
Bifidobacteria (Bifidobacterium longum or B. bifidum)
L. casei
What are some common steps included in cheese production?
- Treatment of milk
- Additives
- Inoculation & milk ripening
- Coagulation
Enzyme
Acid
Heat + acid - Curd treatment (visco-elastic gel/coagulum)
- Cheese ripening
True or False:
Homogenisation is not usually done for most cheese milk (esp. for hard cheese)?
True
As it:
- Disrupts fat globules & increases fat surface area
where casein particles absorb
- Results in a soft, weak curd at “renneting” & increased
hydrolytic rancidity
What is the casein:fat ratio for cheddar?
0.7:1
What is the first 2 steps in cheese production?
- First cheese milk must be clarified,
separated & standardised - Pasteurisation follows
Calcium chloride is added in cheese production as an additive, how much is added and why?
- 5-20g/100kg
- To replace calcium lost during pasteurisation
- Aids coagulation & reduces amount of rennet required
Why is Lipases used as an additive in cheese production?
to ensure proper flavour development through fat
hydrolysis
Why are starter cultures added in cheese production?
- Addition of starter cultures = basis of cheese making
- Lactic acid bacteria (LAB) ferment lactose to produce lactic
acid and gas - pH is lowered & assists coagulation, promotes syneresis
(liquid oozing out), helps prevent spoilage & pathogenic bacteria
from growing, contributes to texture & keeping quality - LAB also produce growth factors = encourage growth of
non-starter organisms - LAB provide lipases & proteases necessary for flavour
development during curing - Bacterial starters added = bulk starters, freeze dried =
lactic Streptococci, Lactobacilli, Leuconostoc sp.,
Propionibacteria - After starter culture inoculation, milk held for 45-60 min at 25-
30°C = ensures bacteria are active, growing & producing acid
What are the 3rd and 4th steps in cheeses production?
3rd = addition of starter cultures 4th = coagulation
What is coagulation in cheese production and how is it accomplished?
- Gel is formed by destabilising casein micelles causing them
to aggregated & form network that partially immobilises
water & traps fat globules in newly formed matrix - This is done by enzymes, acid treatment or heat-acid
treatment
What are the two main categories of butter?
- Sweet cream butter
- Cultured or sour cream butter made from
bacteriologically soured cream (fermented product)
What is the composition of ice cream?
• Is greater than 10% milkfat by legal definition & as high
as 16% fat in some premium products
• Contains 9-12% milk solids-not-fat (aka serum solids):
- Proteins = caseins & whey proteins
- Carbohydrates = lactose
• Contains 12-16% sweeteners = combination of sucrose
& glucose-based corn syrup
• Contains 0.2-0.5% stabilisers and emulsifiers
• 55-64% is water that comes from milk
What are emulsifiers in ice cream?
Include: egg yolk solids, glycerol monostearate (GMS)
- Help in developing appropriate fat structure & air
distribution for smooth eating & good meltdown
characteristic desired during freezing
each molecule contains a hydrophilic portion & a lipophilic portion
= reside at interface between fat & water
Act to reduce interfacial tension or force that exists between two
phases of emulsion
- Also controls excess churning of fat during the freezing
process (Note: commercial mixes of stabilisers and emulsifiers
are available, & ~ 0.5% of this mix used)
Define food science?
the scientific study of raw food materials and their behaviour during formulation, processing, packaging, storage and evaluation as consumer food products.
What are the dimensions of food science
- Food processing and manufacture
- Food preservation and packaging
- Food wholesomeness and safety
- Food quality evaluation
- Food distribution
- Consumer food preparation and use
What distinguishes food science and nutrition?
Food Science
- Concerned with all quality and safety aspects of food before human consumption
- A combination or application of other traditional sciences, e.g. biology, microbiology, chemistry, engineering, nutrition and physics
Nutrition
- Relates to how the body uses foods after eaten to promote and maintain health
What are the four major parts of the food industry?
- Production: includes farming, ranching, orchard management, fishing and aquaculture as well was the technologies in involved such as cultivation; growth; harvest; slaughter; storage and handling of raw materials
- Manufacturing/processing: Conversion of raw agricultural products to more
refined or finished products. This requires many unit operations and processes which are at the core of food technology - Distribution: deals with aspects beneficial to product sales, including: product form; weight and bulk; transportation; storage requirements; storage stability.
- Marketing: the selling of foods -> involves wholesale, retail, institutions and restaurants.
List the 4 major and 3 minor classes of food components
- Major components= those needed in diet in greater amounts o Water o Carbohydrates o Lipids o Proteins - Minor components = though critically important, less is required o Vitamins o Minerals o Phytonutrients
What is the composition of fluid milk?
- Composed primarily of water (87-98)%
- Remaining 12-13% = milk solids
o CHO, lactose, fat, protein, minerals and water-soluble vitamins - Solids-not-fat is a term; excludes fat, includes lactose, caseins, whey, proteins and minerals
- A colloid dispersion of the protein casein & the whey proteins
- An emulsion with fat globules suspended in the water phase of milk
What is the general composition of meat (beef, pork, lamb)?
- General composition o 70% water o 21% protein o 8% fat o 1% minerals (ash)
What are the 3 most common forms of pigments that appear in meat?
- Myoglobin = protein that is the primary colour pigment of meat
- Oxygen present = meat is bright red colour
- Oxygen absent = meat is purplish in colour
How many eggs are consumed every day in Australia?
How many eggs are produced every year in Australia?
- Australians consume 17 million eggs every day’
- 6.22 billion eggs produced by Australian farms every year
Is pasteurisation equivalent to sterillisation?
no - milk sterilisation is not sterilisation, sterilisation = eliminates all viable forms of life
Braising of meats results in tenderising of meat due to: myoglobin breakdown. glycogen breakdown. collagen breakdown. gelatine breakdown.
collagen breakdown
Braising is a method of long and slow cooking at low temp which results in converting tough collagen into tender gelatine
Which could not be an example of a processed food developed with the aid of technology? peas dried pineapple slices bottled pickled vegetables frozen microwave scrambled eggs
peas
During the process of evaporated whole milk
A. production, salt is balanced to:
speed up the vacuum evaporation process.
B. improve the stability of milk under intensive heat treatment.
C. ensure that the fat in the milk does not oxidise.
D. ensure that the milk does not develop a cooked flavour during intensive heat treatment.
B
reasoning salt balance is important for milk withstanding intensive heat treatment
Bacteria not usually used to ferment dairy products include: A. Streptococcus thermophilus. B. Lactobacillus delbrueckii. C. Streptococcus lactis. D. Lactobacillus casei.
C.
remember A and B are yogurt started cultures
Fruits are generally grouped into divisions usually based on:
A. colour, shape and chemical composition.
B. acid content, sugar content and growth conditions.
C. botanic structure, acid content and sugar content.
D. climate requirements, botanical structure and chemical composition.
D.
Which statement is true?
A. Black tea leaves, unlike green tea leaves, are not heat treated before drying.
B. Black tea leaves and green tea leaves are sieved.
C. Black tea leaves, unlike green tea leaves, are hot airdried.
D. Black tea leaves, unlike green tea leaves, contain caffeine and tannins
A.
green tea leaves are heated before rolling to destroy enzymes
What is Antemortem inspection of chickens is:
the spot inspection of each group of birds before slaughter
Antemortem is the first step in chicken processing
Which statement is false?
A. Fermentation removes the carbohydrates around the coffee beans.
B. Fermentation removes pectinolytic bacteria around the coffee beans.
C. Fermentation removes the mucilage around the coffee beans.
D. Fermentation adds flavour to the coffee beans.
C Fermentation removes the mucilage around the coffee beans.
Coffee bean acid fermentation by lactic acid removes the mucilage
________heats the milk up to at least 72°C for at least
15 sec. ________ eliminates all viable life-forms. What
are the two missing words from the options below?
High-temperature/short time pasteurisation,
ultrapasteurisation
HTST pasteurisation involves heating milk to 72 for at least 15 sec
When commercial plant-derived milks are made,:
A. they are not subjected to heat treatment.
B. all of the choices mentioned.
C. they are UHT treated.
D. no additives are included
C. they are UHT treated
When cooking rice, accidentally adding excess oil will:
A. coat the starch granules and raise the gelatinization temperature.
B. coat the starch granules and help in accelerating their gelatinization.
C. coat the starch granules and protect them from bacterial contamination.
D. coat the starch granules and hinder gelatinization
D. coat the starch granules and hinder gelatinization
Within plant cells, carotenoids are generally found
within:
A. vacuoles and the endoplasmic reticulum.
b. chloroplasts.
C. chromoplasts and chloroplasts.
D. chromoplasts.
C. chromoplasts and chloroplasts.
Non-alcoholic carbonated beverages made with natural fruit juices do not contain: A. synthetic colour. b. water. c. carbon dioxide. d. fumic acid.
D
The _______ is the large central portion of the kernel
containing most of the starch, while the _______is the
structure at the end of the kernel rich in fats, proteins
and minerals. What are the two missing words
Endosperm and embryo/germ
Endosperm = large central portion
- 82% of the kernel
- mostly starch
- contains protein
- contains minimal fibre and minerals
Germ = small lower end
- rich in fat, minerals and protein
- contains most of the riboflavin content
When flavouring ice creams, which statement is false?
A. Strawberries are added after freezing and hardening.
B. Cookie dough is added before freezing and hardening.
C. Vanilla flavour is added before freezing and hardening.
D. Chocolate is added before pasteurisation and homogenisation.
A.
hardening is done after packaging
Which statement about homogenisation of milk
is false?
A. Cream does not form at the top of milk in the package.
B. The nutritional value of milk is not affected.
C. Milk fat globules are broken down.
D. Shelf life of milk is affected.
D
homogenisation does not affect nutrition or quality
A by-product of corn refining is: trypsin. vitamin A. lysine. dextrin.
Dextrin Dextrins are byproducts from the hydrolysis of cron and other starches Other corn refining by products include: - dextrose - citric acid and lactic acid - lysine and tryptophan vit C and E
Post-harvest, strawberries will continue to gradually soften due to changes in:
the pectins.
Pectins - decrease the water insoluble and increase in water soluble. this contributes to gradual softening of F and V
Why are eggs gathered and refrigerated frequently? List the two specific storage conditions required.
Eggs are gathered frequently and refrigerated frequently and stored in holding rooms that are between 5 and 7 degrees with relatively high humidity to prevent moisture loss
Give three examples of health problems that could arise when consuming a low protein plant-based milk compared with cow’s milk
Based on 2009 data cows milk accounts for 8% of dietary energy, 16 % of dietary protein and is a good source of highly bioavaliable calcium (makes up 52 -67% of RDI) . Lactose in bovine milk also aid digestion of vit D and phosphorus
Thus health problems that could airse from consuming low protein plant based milk compared to cow’s milk include:
- low dietary intake of protein
- calcium deficiency
- reduced absorption and possible deficiency of Vit D and phosphours
Which components can be extracted from soybean oil, and
give two examples of its uses?
Lectin is extracted from soy bean oil and is used as emulsifier in products that are high in fat and oil and promotes stabilisation and antioxidation in products
What are the three factors that contribute to the flavour of coffee?
- length of roasting time of green coffee beans
- growing region
- method of processing - wet vs dry
What internal structure dominates parenchyma cells?
Name two of its chemical components.
Parenchyma cells = plant cells
Vacuole contains water with soluble substances dissolved with in it such as sugars and acids
Name three plant cell wall carbohydrates referred to as
dietary fibre.
cellulose
hemicellulose
pectic substances
Why does sweetened condensed milk have a longer shelf life compared to evaporated milk? How is its microbial
contamination prevented, and how many heat treatments are carried out in condensed milk processing?
The addition of sugar extends the shelf life
- sucrose increases the osmotic pressure of the liquid which prevents microbial growth
- heat treatments destroy osmiphohic and thermophilic microbes and inhibit oxidation
A cake recipe asks for the addition of water. What would be
the purpose of this ingredient?
The liquid in a baked product
- hydrates protein and starch in flour
- serves to moisten or dissolve ingredients
- assist in the dispersion of all colloids
The first milk that a cow produces after calving is colostrum.
True
pH of fresh milk is 4.6-4.7.
Flase
the ph of fresh milk is 6.6 to 6.8
Monoacylglycerols are the main classes of lipids in milk. True or false
False
Plant-based foods are gaining popularity and the market is developing fast. T or F
True
Caseins have larger particles than whey proteins. T or F
True
The filtrate, the liquid passing through the membrane is the permeate. TRUE/FALSE
true
The shelf-life of ESL (Extended Shelf Life) milk is as long as UHT (Ultra High Temperature)
milk. T or F
False
Provide two examples of healthful drink beverages
Gatorade - provides body with fluids, minerals and energy during exercise. Formulated to stimulate rapid fluid absorption, assure rapid rehydration, provide carbohydrate energy to working muscles and encourage individual to drink more
Bottled water
What are non-nutritive sweeteners and why might they be used in carbonated beverages
Non-nutritive sweeteners
o Have no calories & include saccharin and aspartame
o Aspartame = 150-200 x sweeter than sucrose = very little needed though contains same number of calories/gram as sugar (4 kcal/g)
o Sometimes non-nutritive carbohydrates (carboxymethyl cellulose or pectin) added to give soft drink mouthfeel
what are the compnents of carbonated non alcholoic beverages?
- sweetners
- non nutritive sweeteners
- flavours
o Synthetic, natural flavour extracts and fruit juice concentrates used
o Synthetic flavours very complex and many easily contain >100 distinct compounds
E.g. cola flavours - Colours
o Synthetic agents that are certified food colours
o Meet strict purify requirements
o Soft drinks using natural fruit juices or extracts are supplemented with synthetic colours - Acid
o Phosphoric, citric, fumaric, tartaric and malic are the main used
o Carbon dioxide also contributes to acidity
o Act as preservatives and enhance flavours
o Lower the pH - Water
o The major ingredient of carbonated soft drinks
o Makes up as much as 92% (v/v)
o Must be colourless, odourless, tasteless & free of organic matter
o Near pure water or chemically pure water essential = as trace impurities may react with soft drink chemicals - Alkalinity, iron & manganese must be low - Chlorine cannot be present
o Bottling plants condition water used so it will have high standard - Carbon dioxide (CO2) gas
o Provides “zest” & sparkle
o Sources include carbonates, limestone, burning of fuels & industrial fermentation
o Used from high-pressure cylinders of strict food purity grade
o Amount varies in each beverage & measured in terms of vol. gas/vol. liquid
o Range of 1.5 – 4 vol. in most carbonated beverages
o Carbonator = equipment for carbonating soft drinks
o Carbonation takes place at lower temperatures = CO2 solubility is greater
describe then process of canning or frezzing of fruits
- Need to harvest fruits at proper ripeness stage for good texture and flavour preservation
- Processing done by automated equipment with minimal handling by plant workers
- Assured of wholesome, sanitary products with god flavour & quality
- initial preparation work similar for both
- Mechanical peeling or coring if needed by automatic equipment & prepared in various styles (halves, slices, pieces)
- Before canning/freezing, plant workers remove undesirable portions
- Fresh fruit sorted into size by machine
- Washed in continuously circulating water or under sprays of water
What are some post-harvest factors needing consideration during storage of fruits and veges
Most important factor during storage influencing quality = Temperature reduction & maintenance
- reduces metabolic activity of produce
- reduces metabolic activity of spoilage microorganisms
- general rule: for every 10°C temp rise from optimum = metabolic rate increases 2- to 3-fold
Commercial use of natural or synthetic chemicals:
- To maintain quality through prolonged storage life
- Overcome effects of 3 primary gasses (water vapour/humidity; CO2; ethylene) on Fruits & Vegetables
o Edible coatings = lipid-based waxes; polysaccharide/ protein-based materials; chitosan, cellulose; Aloe vera gels
o Chemicals = chlorine-based solutions; peroxyacetic acid (PAA); organic acids; hydrogen peroxide (H2O2)
o Gases = nitric oxide; sulphur dioxide fumigation
Modified atmosphere
- Attempt to control level of those gases influencing respiration
what are some changes that occur to fruits and vegetables post harvest
Flavour and texture quality attributes affected by changes occurring in
- CHO
o Starch and sugar
E.g. ripe sweet corn = sugars decrease quickly and starch increases soon after harvesting
E.g. ripening of fruit = apples and pears: starch decreases quickly and sugar increase post-harvesting
- Pectin
o Decrease in water-insoluble and increase in water soluble
o Contributes to gradual softening of fruits and vegetables
o Further decrease in water-soluble pectin by pectin methyl esterases (long term)
- Organic acids
o Generally, decrease during storage and ripening affects juice quality
o Oranges = long ripening period on tree
Senescence = quality decline in stored respiring fruits and vegetables after harvesting
- Result from continued enzymatic activity
- Affected by temp and storage atmosphere
Explain climacteric & non-climacteric fruits with examples
Climacteric = fruits producing ethylene gas during ripening e.g. Apple, banana, mango, tomato Non-climacteric = fruits don’t produce ethylene (don’t ripen after harvesting and are ethylene sensitive e.g. cherry, cucumber, grape, orange
Difference between ripeness and maturity of F & V
THEY ARE NOT THEY SAME
Ripeness = the optimum or peal condition of flavour, colour and texture
Maturity = the condition of a fruit or vegetable when picked
- some are picked when mature but not yet ripe
- some fruit also continue to ripen after picked = become overripe if picked at peak ripeness
Respiration and its influence on harvested F & V
continue to respire after harvest
- respiration = the produce take in oxygen and give off carbon dioxide, moisture and heat
o influences storage, packing and refrigeration
o resulting moisture and heat cause growths of moulds
What is harvesting (f and V)
Harvesting = collecting fruit and veges at the specific time of peak quality in terms of colour, texture and flavour in order to market them
- can be by hand or machine
- mechanical harvesting machines exert more impact and damage
- tomatoes have been developed to be firm, high solid and high ph types to withstand impacts of mechanical harvesting
- changes to fruit and vege post-harvest are important influence on safety and quality
what are some factors affecting F and V production
Production
Affected by many factors up to harvesting point:
- soil
- watering and fertiliser
- actual days available for plant to grown and ripen is critical
- some don’t have adequate time at appropriate temp to grow to maturity
What are the major groups of pigments in F and Vs?
- chlorophylls : green colour
- carotenoids: range in colour from yellow to red
- anthocyannins: belongs to flavonoid group purple, blue and red (colour depends on pH
- anthoxanthins including tannins
what is turgor
Cell turgor = Rigidity of plant cells resulting from being filled with water
- State of turgor depends on osmotic forces
- Plant cells have cells walls strong/elastic enough to withstand turgor pressure (i.e. pressure of the water in the cell against the wall)
Range of textures encountered in fresh or cooked fruits and vegetables •
- Largely explained by changes is specific plant cell components
- Plant tissues generally contain more than 2/3 water
- Relationship between plant cell components & water = determine texture
Cell turgor = Rigidity of plant cells resulting from being filled with water
- State of turgor depends on osmotic forces
- Plant cells have cells walls strong/elastic enough to withstand turgor pressure (i.e. pressure of the water in the cell against the wall)
- Most important factor responsible for plumpness, succulence, crispness
- Affected when plant tissues are damaged, killed by storage, freezing and cooking
o Denaturation of cell membrane proteins occur = loss of perm-selectivity
o Without perm-selectivity, osmotic pressure in cell vacuoles cannot be maintained
o Water and dissolved substance diffuse out of cells = remaining tissue left in soft and wilted condition
Describe plant tissues & their functions
- Dermal tissues (epidermis and endodermis)
o Layer of protective tissue
o Press compactly together to form skin/peel/rind
o One leaves, stems or fruits:
Secrete waxy cutin, forming water-impermeable cuticle
o On leaves and young stems - Vascular tissue
o Has two clearly defined structures = xylem and phloem
Xylem = used by plant to transfer water
Phloem = transfers food - Supporting tissue
o Varies depending upon F or V
o In addition to parenchyma cells
Collenchyma
Sclerenchyma
describe the structure of a parenchyma cell
Parenchyma cell (plant cell) = structural unit of the edible portion of most fruits and veges
Differ between different fruits and veges in gross size and appearance but essentially have same fundamental structure
Consists of:
- Vacuole
o Contained within the cell wall
o Composed of water and soluble substances e.g. sugars, acids, esters, ketones and pigments)
- Chloroplasts and mitochondria
o Carry out energy conversions in the cell
o Chloroplasts = through photosynthesis
o Mitochondria = through cellular respiration = contain fats, proteins, and enzymes
- Leucoplasts (colourless plastids) also can store starch = energy source for plant cell
- Nucleus
o Embedded within the cytoplasm
o Controls reproducing and protein synthesis
o Needed for continued cell life (together with mitochondria)
- Cells walls
o Consists of primary wall and secondary wall
o Primary walls of two cells joined together by a common layer called middle lamella
o Chief components are cellulose, hemicellulose and pectic substances (complex CHO)
what is the general composition of fruits and vegetables
Depends on
- Botanical variety
- Cultivation practices
- Weather
- Degree of maturity prior to harvest
- Condition of ripeness = continues after harvest and influence by storage conditions
Composition
- High in water (water content of apples and milk is similar)
- Low in protein (no greater than 3.5%)
- Low in fat (no greater than 0.5%; expectations: sweet corn, avos)
- Important sources of digestible CHO and fermentable CHO
- Important source of minerals and vitamins
what are the general properties of fruits
- Generally acid and sugary
- Grouped depending on botanical structure, chemical comp. and climatic requirements
Berries = generally small and quite fragile (grapes are berries growing in clusters)
Melons = large and have tough outer rind
Apricots, cherries, peaches and plums = contain single pits
“Pomes” = apples, pears, quinces = contain many pits
Citrus = high in citric acid = oranges, lemons and grapefruits
Tropical & sub-tropical fruits = require warm climates for growth = bananas, mangos, papayas, pineapples
what are the general properties of vegetables (3)
- Derived from various parts of plants
- Classified according to plant parts which derived from = roots; tubers; stems; leaves; buds
- Some vegetables are genetically close but totally different tissues types
- E.g. kale, cabbage, brussels sprouts, broccoli, cauliflower and kolrabi are all brassica oleracea
botanic definition of fruits and vegetables
Fruit
- The ripened ovary of a plant
- The seed baring structure of a flowering plant
Vegetable
- A herbaceous plant containing an edible portion such as a leaf, shoot root, tuber flower or stem
why are doughs and batters mixed?
- Uniform distribution of ingredients
- Minimum loss of leavening agent
- Optimum blending to produce characteristic textures
- Optimum development of gluten for various products
Many Different mixing methods and beating utensils exist
why are liquids used in baked products ? (6)
- e.g. milk, buttermilk, water or juice ect, which function differently
- hydrates protein and starch in flour
o helps with gluten development
o starch must absorb water to gelatinize during baking - serves to moisten or dissolve ingredients (salt, sugar and baking powder)
- assists in dispersion of all colloids and suspensions
- contributes to leavening (when covered to steam) during baking
why is sugar used in backed products? (5)
- adds sweetness
- tenderises crusts
- aids in browning
- in yeast breads, serves as food for yeast
- too much sugar = less rising, resulting in gummy texture
why are fats used in baked products
- facilitates air incorporation by shortening/inhibiting
o gluten development
o starch gelatinization
o trapping formed air bubbles during beating of batter and holding them - elevates temperature at which egg, and flour proteins heat denature
- tenderises baked products
o fat coats flour particles, causing dough structure to separate into layers
why is salt used in baked products ? (3)
- adds flavour to baked
- in yeast breads, regulates action of yeast and inhibits actions of certain enzymes
o if yeast breads contain no salt, they will produce carbon dioxide too quickly and be sticky and difficult to handle and have poor appearance
why are eggs used in baked products
- incorporates air into product
- adds colour and flavour
- contributes to structure
o during baking, the egg proteins coagulate
purpose of leaving agents in baked products
- ingredients that produce gases in batter and doughs
- make products rise and become light and porous
- baking soda (sodium bicarbonate) = an alkaline ingredient
o bake immediately
o used in recipes containing acidic ingredients
o acids balance the alkali preventing bitter taste - baking powder = contain dry acid, baking soda and cornflour
o using too much produces too much CO2 abd baked goods will collapse becoming small and compact
o single acting = reacts in presence of moisture
o double acting = works at room temp (in bowl with moisture) and reacts again with heat (in oven)
o keep containers tightly closed and watch expiry date
o measure carefully
purpose of yeast in baked products
o Living organisms producing carbon dioxide by fermenting
o Available in different forms & classified based on activity = active (refrigerate/freeze after opening) VS inactive (foil sachets) yeasts
o Using too much gives undesirable flavour, texture & appearance
purpose of steam and air in baked products
- Steam
o Produced when liquid ingredient reaches high temps during baking - Air
o Incorporated into baked goods when beating eggs and creaming fat and sugar, beating batter
o All baked products contain some air
what is gluten
- insoluble proteins in wheat flour
- comprised of fractions = glutenin and gliadin
- forms when flour is moistened with water and kneaded
- glutenin provides elasticity and gliadin provides strength
- can be extracted from dough by thorough washing with water
explain the grades of wheat flour
- White flour graded based on the four streams used to make them
- Straight grade = should contain all flour streams resulting from the milling process = but 2-3% of the poorest streams containing fine bran particles and outer endosperm layers withheld (very little of such flours on market)
- Patent flours = flour from interior endosperm, extracted during first stream of milling
o More refined portion of endosperm
o Divided into following, in order of quality
First patent
Second patent
First clear
Second clear
Red dog
what are the three classes of wheat?
hard, sodt and durum
summarise the key points of modern milling
- Flour streams vary in their bran, germ and gluten content
- Flour is bleached because freshly milled flour is yellowish due to presence of carotenoid pigments (carotin)
- When unbleached flour used for bread baking = small and coarse-textured loaf produced
- Kind and composition of flour depends on
o Class of wheat used for flour milling
o Conditions under which the wheat is grown
o Degree of fractionation
what are the function of starches
- Thickeners in gravies sauces and puddings = absorb water and become a gel when cooked
- Colloid stabilisers
- Moisture retainer
- Gel forming agents
- Binders (processed meats)
- Fat subs. In diet yogurts
what us the effect of dry heat on starch (3)
- Starch containing foods:
o change to brown colour e.g. bread toast
o flavour changes
o starch present becomes more soluble & has reduced thickening power
o Process called dextrinization = partial hydrolysis of starches forming dextrin
Dry-heat dextrin form in crust
effects of moist heat on starch
- Starch granules heated in water: -
o swell
o Increase in dispersion & viscosity until peak thickness reached
o translucency of thickened mix increases - process is called gelatinization
describe two types of starch molecules
o Amylose (A) = linear helical structure = a polysaccharide of glucose Contributes gelling characteristics cooked and cooled starch mixtures o Amylopectin (B) = highly branched polysaccharide of glucose Provides thickening properties (does not contribute to gel formation)
describe the general structure of a grain (bran, aleurine, endosperm and germ)
Bran = outer layers - 5% of kernal, mainly cellulose, contains much of the minerals and vitamins
Aleurone = under bran layers- 8% of kernal, rich in proteins, phosphorus and thiamine also contains starch
Endosperm = large central portion - 82% of kernal, mostly starch, contains most pf protein but very little fibre/minerals
Germ = small lower end - rich in fat minerals and protein and contains most riboflavin
what are five food products of soybean extraction
- Hydrolysed Vegetable protein
- lecithin
- meat analogous (tofu)
- soy fibre
- soy flour
- non-dairy soy frozen desserts
define leagumes, pulses and beans
Legume = any plant from the Fabaceae family, including its leaves, stems, and pods Pulse = the edible seed from a legume plant (e.g., peas, lentils, beans) Beans = one type of pulse
what are some important consideratiosn for seafood storage
- Fish & shellfish must never sit unrefrigerated for long
- Should be transported in ice chest
- If have bruises or punctures = will spoil more rapidly
- Finfish = refrigerate as close to 0°C = held twice as long than at 3°C
- Fish & shellfish should be cooked within 2 days of purchase
- Fish sitting in own juices deteriorates more rapidly
what are some fish by-products
- Intestines, heads and gills can be dried, ground up and converted to animal feed = fish meal
- Fish protein concentrated (FPC) or fish flour
- Roe = mass of eggs (e.g. caviar)
- Surimi = high protein, odourless, flavourless by-products can be used to make imitation crabmeat
what are some methods for fish presevation
- Progress keeps being made on irradiation technologies
- Refrigeration, freezing and canning still remain best and most used
- When fish individually frozen = glazed with layers of ice to protect fish surface from oxidation & freezer burn (drying out) –
o glazing done by dipping fish in cold water & then freezing a layer before dipping fish again - prawns are also glazed - Frozen fish need packaging in materials that are airtight & moisture tight
- Pre-breaded, precooked fish sticks & individual portions also frozen
- High-quality, low-fat fish can be frozen at -21°C for up to 2 yrs
- Fish with higher fat content = salmon, tuna & sardines often canned
what are some factors that affect fish grading ?
- Done after inspection and determines quality level
- Only products that have an established grade standards can be graded
- Fish usually graded according to:
o Appearance = over general appearance including flesh consistency, odour, eyes, gills & skin
o Discolouration = refers to any colour not characteristic to species
o Cutting & trimming defects = include body cavity cuts, improper washing, improper deheading & evisceration defects
o Improper boning (for boned styles = fillet only) = refers to presence of unspecified bone or bone piece
spoilage issuses associated with fish
- Fresh fish held at 16°C only good for 1 day or less
- At 0°C = fish may remain good for 14 to 28 days, depending on species (may be less for some)
- Happens quicker than meat = bacteria on skin & in digestive tract attack all tissues once fish killed, & these bacteria often adapted to cold temperatures
- Fish struggle when caught = convert glycogen to lactic acid before death
- Fish fat has phospholipids containing trimethylamine oxide (TMAO) which regulates osmotic pressure in living fish cells when fish die = TMAO converted by bacterial enzymes (from fish) to “fishy” smelling liquid substance trimethylamin
true or false Fresh fish
- If head still on, eyes should be bright, clear, transparent & full-often protruding. Eyes become cloudy, may turn pink & shrink as fish decomposes
true
differences between fish and shellfish
Fish
- Can be referred to as finfish
- Classified into saltwater and freshwater varieties
- Flavour depends on water in which grown
- Also classified on basis of fat content
o Lean = <2% fat
o Fat = >5% fat
- Common edible species = salmon, tuna, trout, flake/shark, cod, mackerel, tilapia, snapper and bream
SHELLFISH
- Include molluscs
o Are soft-bodied and partially or wholly enclosed in hard shell composed of minerals
o E.g. oysters, clams, abalone, scallops, and mussels
- Include crustaceans
o Are covered in crust-like shell and have segmented bodies
o E.g. prawns, lobsters, crabs, cray fish, Morten bay bugs
what some cooking functions of eggs
- Bind ingredients
- Leavening agents
- Thickening agent
- Emulsify mayo
- Glaze on breads and cookies
- Clarify soups and coffee
- In boiled candies
- Hard cooked and used as garnish
describe egg structure and characteristics
- Shell
o Accounts for 9-12% of total egg white
o First line of defence against bacterial contamination
o Composed: calcium carbonate, magnesium carbonate, calcium phosphate and other organic matter - White (thick and thin albumen and inner thin albumen)
o Egg albumin in raw eggs is opalescent and doesn’t appear white until beaten or cooked
o If yellow or greenish = riboflavin present
o Cloudiness = due to presence of CO2 that not had time to escape = indicates very fresh yegg - Yolk
o Colour depends on diet of hen - Germinal disc
o The channel leading to yolk centre
o When egg is fertilised, sperm enter by way of germinal disc and travel to centre and embryo chick starts to form - Membranes
o Two shell membranes just inside shell – inner and outer = after egg laid = cools and air forms between two layers at large end of egg
o Vitelline membrane – covers yolk protects yolk from breaking = weakest at germinal disc and gets more fragile as egg ages
