FOOD2000 END OF SEM Flashcards
What is the general composition of meat?
- 70% water
- 21% protein
- 8% fat
- minerals (ash)
What does the quality of meat depend on?
- breed
- heredity
- sex
- feeding
- pre-slaughter & slaughtering conditions
- dressing
- carcass cooling
- storage conditions
What is the purpose of meat grading?
Establishes & maintains uniform trading standards & aids in determination of value of various meat cuts
What is used to determine the class and grading of meat?
Dentition (number of teeth), weight & fat depth
What are the steps in slaughtering?
- Stunning: renders animal unconscious, prevents pain/distress
- Sticking: severs major blood vessels in neck or thorax and animal bleeds to death (exsanguination)
- Skinning/Dehairing & Evisceration: minimises microbial contamination
- Inspection: done ASAP after slaughter to identify abnormalities or disease
- Washing & grading: fine spray of water to remove surface blood & bone dust, sometimes done using hot (water or by including low concentrations of organic acids)
- Refrigeration: done after being bled, skinned & eviscerated (removal of internal organs). Carcases are chilled for 24-48h before grading & processing
What happens after slaughtering?
Chilling and aging
What does chilling cause?
- Muscle contract & stiffen = rigor mortis
- as rigor mortis begins, meat becomes progressively less tender until rigor mortis completed
- Chilling done immediately after slaughter to prevent spoilage.
- Cold shortening = occurs when muscle chilled to <16°C before rigor mortis completion (meat becomes tough). Same result if carcase frozen before rigor mortis completion “thaw rigor”
What does meat aging cause?
- Holding meat in refrigerator
- Increased tenderness due to natural enzymatic changes taking place in muscle.
- Beef held at higher temperatures tenderises faster BUT may also spoil
- Pork & lamb rarely aged = as already tender as relatively young
What are Livestock marketing & prices affected by?
weather, feed prices, government import policies & consumer demands
What is meat curing?
- preservative method
- flavour & colour enhancement
Some curing agents:
- Salt = preserve & add flavour.
- Sodium nitrate & sodium nitrite = fix red colour of meat, acts as a preservative & prevent microbial contamination
- Sugar = colour stability & flavour
- Spices = produce desired flavour
What is meat smoking?
- Smoke protects fat from rancidity
- Contributes to colour characteristics
- Creates unique flavours in processed meats
- Smoke most effective microbial growth inhibitor when used with other preservation techniques
What does meat colour indicate?
- Myoglobin = protein that is the primary colour pigment of meat (store oxygen in muscle tissue)
- Exposed to air/heat, goes from red to brown
- Oxygen present = meat is bright red colour
- Oxygen absent = meat is purplish in colour
What are the Factors affecting milk composition?
- Nutritional factors: Type of feed and Quality of feed
- Non-nutritional factors:
- Breed
- Stage of lactation
- season & temperature
- Age & size
- Disease
- Milking frequency
What are the by-products of milk?
- Concentrated & dried products
- Whey products
- Yoghurt
- Cheese
- Butter
- Ice cream
- Other fermented products
What is yogurt?
- A semisolid fermented milk product
- Flavour varies but basic ingredients & manufacturing essentially consistent
- uses milk from cows
- Whole milk, partially skimmed milk or cream (GREEK) used
What is the cooking function of eggs?
- Bind ingredients
- Leavening agent
- Thickening agent
- Emulsify mayonnaise, hollandaise sauce
- Glaze on breads & cookies
- Clarify soups & coffee
- In boiled candies & frostings = retard crystallisation
- Hard cooked & used as garnish
What are the codes on eggs?
- After cleaned & checked for quality, every egg is stamped with unique code that identifies farm where it was laid = allows eggs to be traced back to farm of origin if necessary
What is the composition of the egg yolk?
- Up to 35% liquid weight of egg
- Contains all the fat & just less than 1⁄2 the protein
- Contains higher proportion of egg’s vitamins and minerals
- Contains all the zinc
What is the composition of the egg white?
- Contains more than half the egg’s total protein, niacin, riboflavin, and major inorganic compounds like chlorine, magnesium, potassium, sodium & sulphur
- protein containing all essential AA
- More opalescent than white
- More transparent in older eggs than fresher eggs
What are the steps in egg quality control?
- Inspection: Eggs inspected by series of machines
- Dry Cleaning: using a soft bristled sanitised brush or by gentle rubbing with sanding sponge, cloth or paper towel (visibly dirty eggs segregated away from clean eggs)
- Washing: Some farms wash eggs in warm water & gentle sanitiser liquid as soon as collected = washing process is very fast & are dried immediately
- Light disinfectant: Many farms run eggs through UV light disinfectant system to kill any bacteria
- Internal quality: Bright lights to inspect egg’s internal quality = process called ‘candling’
- Candling: If any internal defects noticed, eggs removed & sent separate from first quality eggs
- Height and thickness: Tiny cracks not visible to human eye are checked & measuring height of egg white & shell thickness done
- Crack detector: Automatic acoustic crack detectors containing lots of small probes gently tap eggs at very fast speeds as they pass through machine = if cracks in eggshell, no matter how small, tapping energy will be absorbed, resulting in duller sound
What does the egg structure contain?
- shell
- white
- yolk
- air cell
- chalaza
- germinal disc & membrane
What are the three main egg farming systems?
free range, caged, barn-laid
What are the Chicken meat processing steps?
- Inspection; classifying and grading
- Suspension and shackling of each bird by legs
- Stunned immediately with electric shock
- Bleeding
- Scalding to loosen feathers
- Feathers picked off by machine
- Removing of pinfeathers
- Evisceration
- Chilling in ice water
- Postmortem inspection
- Grading
- Packing
What is the classification of butter?
Usually divided into two main categories:
- Sweet cream butter
- Cultured or sour cream butter made from bacteriologically soured cream (fermented product)
Butter can also be classified according to salt content:
- unsalted
- salted
- extra salted
How are meat carcases sold?
- Sides
- Quarters
- Wholesale cuts
In dried meats, what is the purpose of fermentation?
encouragement of lactic acid bacterial growth = useful as meat preservative & tangy flavour
What are textured protein products?
- at least 50% protein
- Contain eight essential AA & vitamins + minerals found in meats
- Soybean protein most commonly use
- Other proteins used = wheat gluten, yeast protein = used singly or in combination
What is the storage of eggs?
- Can be stored in shell at -1°C for up to 6 months
- Can be frozen out of shell for extended storage
- Eggs may be frozen as whole egg minus shell, separately as white & yolk
- For food manufacturing needs = eggs minus shell, can be dehydrated (dried) as whole eggs, whites, yolk using spray drying, tray drying , foam drying & freeze drying
What are blood spots on eggs?
- Occasionally found on egg yolk
- Don’t indicate a fertilized egg = caused by rupture of blood vessel on yolk surface during egg formation or by similar accident in oviduct wall
What is the composition of milk?
- primarily of water
- Carbohydrates
- Lactose
- Fat
- Protein
- calcium, phosphorus, magnesium, potassium, sodium, chloride & sulphur
- thiamine & riboflavin
- Solids-not-fat: lactose, caseins, whey, proteins & minerals
Fluid milk is; A colloidal dispersion of the protein casein & the whey proteins and An emulsion with fat globules suspended in the water phase of milk
What are meat substitutes?
Plant protein products
- Spinning vegetable proteins into fibres
- protein dissolved in alkaline solution then extruded & coagulated to form fibre bundles
- flavour & colour compounds and binders are added such as egg albumen or vegetable gum, emulsifiers
- Fibres then processed into shapes & textures
What are Physical properties of milk?
- Opacity = due to suspended particles of fat, proteins and certain minerals
- Colour = white to slight yellow (carotene content)
- isotonic
- pH and Acidity - important indicator of microbial quality of raw milk: pH of fresh milk = 6.6 to 6.8 (0.13% lactic acid)
What is the air cell in an egg?
- The empty space between the white & shell at large end of egg
- When egg first laid, its warm; contents contract as it cools = inner shell membrane separates from outer shell membrane = air cell formed
What is the chalaza in the egg?
- Ropey strands of egg white that anchor yolk in place in centre of thick white
- More prominent = fresher the egg
What does the colour of egg shell show?
Has nothing to do with egg quality, flavour, nutritive value, cooking characteristics or shell thickness
What is the effect of milk composition?
- Milk prices based on the milkfat and protein solids
What are the steps in cheese production?
- Treatment of milk
- Additives
- Inoculation & milk ripening
- Coagulation; Enzyme, Acid, Heat + acid
- Curd treatment (visco-elastic gel/coagulum)
- Cheese ripening
What is cheese?
- fresh or ripened product obtained after coagulation & whey separation of milk, cream or partly skimmed milk, buttermilk, or a mixture of these products
- Essentially the product of selective concentration of milk = casein, fat & water (10% cheese yield from milk)
What is butter?
- Represents about a 20-fold concentration of fat to milk
- Made by churning pasteurised cream at cool temperatures (< 10°C)
- Churning breaks fat globule membrane = emulsion breaks, fat coalesces & water (buttermilk) escapes
- Contains 80% milkfat
What are the membranes in the egg?
- Two shell membranes just inside shell; inner & outer; after egg laid = cools & air cell forms between two layers at large end of egg
- Vitelline membrane; covers yolk and protects from breaking = weakest at germinal disc & gets more fragile as egg ages
What is the germinal disc in the egg?
- The channel leading to yolk centre
- When egg is fertilised, sperm enter by way of germinal disc & travel to centre & embryo chick starts to form
What does the colour of the egg yolk depend on?
- diet of hen
- Pigments not changed during cooking
What are the types of emulsion?
- Oil in water emulsion (O/W): Oil droplets dispersed in aqueous phase
- Water in oil emulsion (W/O): Water droplets dispersed in oil phase
What is emulsion?
- a dispersion of one fluid into another
- Fluids are normally immiscible (dont mix)
- Substance making up the droplets in emulsion is the discontinuous, dispersed or internal phase
- Substance making up the surrounding fluid is called the continuous or external phase
- Emulsifier coats emulsion droplets, preventing them from coalescing or recombining with each other
What are the basic steps of manufacturing ice cream?
- Blending of mix ingredients
- Pasteurisation
- Homogenisation
- Chilling & Aging the mix
- Freezing
- Packaging
- Hardening
What is ice cream made from?
basic white mix:
- milk
- cream
- skim- or whole milk powder
- buttermilk powder
- condensed milk
- whey powder
- anhydrous milk fat
- unsalted butter
In the ice cream process, what is pasteurisation?
Usually 80-85°C for ~15-30 sec
In the ice cream process, what is homogenisation?
-Essential for good smooth texture & even dispersion of ingredients
- Usually at ~75°C
- Reduces size of fat globules
- Increases surface area
- Forms membrane
- Makes possible the use of butter, frozen cream, etc.
- Controls “whippibility” and churning during freezing
In the ice cream process, what is chilling and aging the mix?
Mix is cooled to 2-5°C
- Then aged at this temperature
- Aging allows time for:
fat to cool down & crystallize,
for proteins & polysaccharides to fully hydrate & stabilise gel formation
- Aging carried out for 4-24 h depending on stabiliser used (gelatine takes 24 h)
In the ice cream process, what is freezing?
- Soft freezing (~50% water is frozen)
- Beating to incorporate clean air & freezing in scraped surface heat exchanger
- Fine even foam required = freezing rapid
- Temperature at outlet of freezer -1 to -9°C
In the ice cream process, what is packaging?
- when soft unless other steps required, e.g.: addition of fruits, nuts, candy, cookies
- At this stage, consistency same as soft serve ice cream
In the ice cream process, what is hardening?
~90% water frozen
- ice cream cooled to ~ -35°C in a blast freezer = should be as rapid as possible to ensure small ice crystals
- Must store ice cream at < -18°C after hardening
- Poor storage conditions are detrimental to ice cream quality
In the ice cream process, what is the blending of mix ingredients?
- Usually heated to 50-60°C to effect good mixing
What is the shelf life of ice cream?
- Only consideration is texture should be smooth
2 main problems: - coarseness due to large ice crystals = slow cooling or melting/refreezing or fluctuating storage temperatures
- “sandiness” due to lactose crystals = can occur if lactose:water ratio is wrong
How do you maintain shelf life of ice cream?
- Formulate the ice cream properly
- sugar considerations
- stabilisers: bind free water
- Freeze the ice cream quickly
- Harden the ice cream rapidly
- Avoid temperature fluctuations during storage & distribution
What are the two main chicken hybrids?
- cobb and ross
- have been selectively bred for their growth, feed conversion (can feed them anything)
Do you want to cross breed chickens?
Yes as this creates stronger, more robust & health of cross is greater than the average of their parents (male parent = good muscling & body weight, while breeder hen = capacity to lay plenty of fertile eggs to be hatched into meat chickens)
- Don’t want inbreeding
What are the 2 main bacteria present that can cause illness in poultry?
salmonella and campylobacter
What are the Physio-chemical Characteristics of butter?
Main constituents (normal salted butter):
- Fat (80-82%; and maybe some milk solids-not-fat)
- Water (15.6-17.6%) = dispersed in fine droplets so butter
looks dry
- Salt
- Protein, calcium, phosphorous
- Fat soluble vitamins A, D & E :
Colour should be uniform
Should be dense and taste clean
Should be of smooth consistency so easy to spread & melt readily on tongue
What is the ice cream mix made up of?
- Fat
- Milk solids-non-fat (MSNF)
- Sweeteners
- Stabilisers
- Emulsifiers
- Flavours
What is the purpose of fat in the ice cream mix?
- Gives creaminess & improves melting resistance by stabilising air cell structure of ice cream.
- Whole milk, cream, butter or anhydrous milk fat (AMF)
- Milk fat can be replace by vegetable fat = refined or hydrogenated coconut oil & palm kernel oil most commonly used
What is the purpose of Milk solids-non-fat (MSNF) in the ice cream mix?
- nutritional value.
- water-binding & emulsifying effect.
- positive influence on air distribution = leading to improved body & creaminess
What is the purpose of sweeteners in the ice cream mix?
Increases solids content. Gives level of sweetness consumers prefer.
What is the purpose of stabilisers in the ice cream mix?
- Increase viscosity of mix & creates good texture.
- Control growth of ice crystals & improve melting resistance = producing firmer product (if not present = product becomes coarse & icy very quickly due to migration of free water & growth of existing crystals).