FOOD2000 End of Sem Exam Revision

What is fluid milk?

• Composed of:

  • 87% water

  • 13% milk solids

    • Milk solids-non-fat = 9%

    • Fat = 4%

• Fluid milk is a colloidal dispersion of casein and whey proteins.

• in the water phase of milk, we observe an emulsion of suspended fat globules.

What are milk solids and milk solids-non-fat?

Milk solids:

• CHO

• Lactose

• Fat

• Protein

• Minerals

• Vitamins

Milk solids-non-fat:

• Lactose

• Casein

• Whey proteins

• Minerals

What are the factors affecting milk composition?

• Nutritional factors:

  • Type of feed

  • Quality of feed

• Non-nutritional factors

  • Breed

  • Stage of lactation

  • Season and temperature

  • Age and size

  • Disease

  • Milking frequency

What are the physical properties of milk?

1. Appearance

   1. Opacity - due to suspended particles of fat, proteins, and minerals

   2. Colour - white/yellow due to carotene content

2. Density

3. Osmotic pressure (isotonic)

4. Freezing point (-0.5ºc)

5. pH and acidity

   1. pH = 6.4-6.8

What is the practice of milk production?

1. Most cows are milked 2x a day.

2. Raw milk is immediately cooled from cow’s body temp to below 5ºc.

3. Raw milk is stored at farm under refrigeration until picked up by insulated tanker trucks.

4. Raw milk is pumped into the tanker, and a small sample is collected for later lab analysis.

5. Raw milk, arriving at milk processing plant, is tested for quality.

6. Milk is pumped into large refrigerated silos of processing plants.

7. Modern cream separators separate cream and skim portions of milk on a centrifugal separation.

8. 2 streams of milk are produced during separation:

   1. Fat-depleted stream (produced beverage milk)

   2. Fat-rich stream (used for butter and ice cream)

What is the quality assurance of raw milk?

• Standard temperature

• Flavour and odour

• Composition

• Antibiotics

• Freezing point depression

• pH / acidity

What is pasteurisation?

The process of heating raw milk to kill all pathogenic microbes that may be present.

What are the 2 types of pasteurisation?

1. Low-temp long-time (LTLT)

2. High-temp short-time (HTST)

What is low-temp long-time (LTLT) pasteurisation?

A batch method of heating milk to 63ºc for 30 mins.

Or 65ºc for 15 mins.

Can produce a “cooked” flavour, so is not always used for fluid milk products.

What is high-temp short-time (HTST) pasteurisation?

A continuous method of heating milk to 72ºc for 15 secs.

Milk is immediately cooled to below 4ºc and is packed into plastic bottles or plastic-coated cartons.

What is ultrapasteurisation?

Heating milk to above 135ºc for 2-5 seconds, followed by rapid cooling to 7ºc or below.

What is ultra-high temperature (UHT) processing?

Sterilisation of milk by heating to 137-150ºc for 1-4 seconds.

Milk is then aseptically packaged (sterilised packaging and sterilised milk are combined in a sterilised environment).

This milk does not require refrigeration until opened.

What is milk homogenisation?

• Milk is forced through a narrow gap under high pressure to break up butterfat globules to smaller sizes.

  • Small fat globules will not coalesce (stick together).

• This prevents the cream portion of milk from rising to the top of the package.

  • Cream rises to the top because it is lighter than milk.

• This doesn’t impact the nutrition or quality of milk.

What are the fat contents of different types of milk?

Raw milk = 4%

Regular/full-fat milk = 3.2-3.8%

Reduced fat milk = 2%

Low-fat milk = <1.5%

Skim/no-fat milk = 0.15%

What nutrients are added to milk to improve the nutritional quality?

1. Vitamin A

   1. Added bc it is lost during fat separation and heating.

   2. Added to reduce vision and immune system issues.

2. Vitamin D

   1. Wasn’t present to begin with.

   2. Added to support bone mineral density and Ca absorption.

3. Milk solids

   1. Added to to achieve the natural mineral (Ca and Fe), protein (casein), and sugar (lactose) portion of non-fat dry milk.

What are concentrated milk products?

Concentrated milk products = Evaporated milk, sweetened condensed milk, condensed whey.

Made through partial water removal.

What are dried dairy products?

Dried dairy products = milk powder, whey powder, whey protein concentrate.

They have less than 4% water.

What are the benefits of concentrated and dried dairy products?

Increased shelf-life

Convenience

Product flexibility

Decreased transportation and storage costs

How do you make evaporated milk?

1. Concentration at low temps by vacuum evaporation to 30-40% total solids.

   1. Lowers boiling point to 40-45ºc, resulting in little to no “cooked” flavour.

2. Second standardisation to balance salts.

   1. Important for milk withstanding intensive heat treatment.

3. Evaporated milk is packed into cans.

4. Continuous flow sterilisation.

5. Packaging under aseptic conditions.

Evaporated milk has a light-brown colour and can be stored for up to a year.

How do you make sweetened condensed milk?

1. Heat treatment (85-90ºc for several seconds).

2. Vacuum evaporation

3. Sugar is added before and after evaporation to avoid undesirable viscosity changes during storage.

4. Milk is cooled and lactose crystallisation is induced.

5. Milk is inoculated with powdered lactose crystals, then cooled with agitation.

6. Product is packed into small cans for retails sales and bulk containers for industrial sales.

How do you make condensed whey?

1. Made from the whey resulting from cheese-making.

   1. Whey contains lactose, lactoglobulin, lactalbumin, and water.

2. Whey is condensed through evaporation.

3. Fat is removed by centrifugation.

   1. Then can be churned to whey cream or used in ice cream.

How do you make milk powder?

1. Standardisation

2. Heat treatment (more severe than pasteurisation) to destroy all pathogenic and spoilage microbes.

3. Evaporation

4. Homogenisation (to decrease free-fat content)

5. Spray-drying

6. Milk powder is packed to protect from moisture, air, and light.

How do you make whey powder?

1. Standardisation

2. Heat treatment (more severe than pasteurisation)

3. Concentration through reverse osmosis

4. Vacuum evaporation

5. Homogenisation

6. Lactose crystallisation (to decrease hygroscopicity)

7. Spray-drying

8. Packaging

How do you make whey protein concentrate (WPC)?

1. Clarification of whey

2. Pasteurisation

3. Whey is cooled and held til calcium phosphate complexes stabilise

4. Ultrafiltration (or reverse osmosis, microfiltration, demineralisation)

5. Low molecular compounds are removed.

6. Concentration of proteins in retentate.

7. Retentate undergoes pasteurisation and evaporation.

8. Spray-drying (at lower temps to avoid large amounts of protein denaturation.

What is yoghurt?

A semi-solid fermented milk product.

How do you make yoghurt?

1. Clarification

   1. Removal of impurities

2. Separation into cream and skim milk

3. Standardisation

   1. Various ingredients are blended together in a mix tank. Fortification of milk to increase milk solids-non-fat.

4. Pasteurisation

   1. Formation of casein networks

   2. Increases gel-firmness and decreases syneresis

   3. Shortens coagulation time by increasing pH at which coagulation occurs.

5. Homogenisation at 50-60ºc

   1. Improves viscosity and firmness of coagulum.

   2. Results in even distribution of constituents, SNF, and fat.

6. Cooled

   1. To optimum temp for starter culture growth (40-45ºc).

7. Starter culture

   1. Incubated til firm gel forms (5-7 hours)

   2. Symbiotic blend of Streptococcus thermophilus (ST) and Lactobacillus delbrueckii subsp, bulgaricus (LB)

8. Stir (for stirred yoghurt)

9. Add fruit (if required)

10. Pack, store, dispatch

What are the 2 cultures used for yoghurt production and what is their role?

Symbiotic blend of:

1. Streptococcus thermophillus (ST)

2. Lactobacillus delbrueckii subsp. bulgaricus (LB)

• ST grows faster and produces acid and CO2, stimulating LB growth.

• Proteolytic activity of LB produces simulatory peptides and AAs used by ST.

• These microbes are responsible for the typical yoghurt flavour and texture.

• ST drops initial pH to 5.5, LB further decreases pH to 4.5.

What are the different types of yoghurt?

1. Set

   1. Incubated in containers.

   2. Additives (e.g. fruit) sink to the bottom

2. Stirred

   1. Incubated in tanks

   2. Gel is disrupted by stirring, pumping, and filling.

   3. Additives are suspended

3. Drinking

   1. Similar to stirred, but coagulum is broken down to a liquid.

4. Frozen

   1. Incubated in tanks and frozen like ice cream.

5. Concentrated

   1. Incubated in tanks, concentrated, and cooled before packing.

   2. E.g. greek yoghurt

6. With probiotics

   1. Contain probiotics or “therapeutic” starters (e.g. ABC starters)

   2. These produce acid slowly (compared with normal yoghurt starters) so are usually added in addition to ST and LB.

   3. It is common to add ingredients known as prebiotics (e.g. inulin) which will (after digestion) aid in growth of probiotics in the colon.

What is cheese?

The fresh/ripened product obtained after coagulation and whey separation of milk, cream, buttermilk, or a mixture of these products.

Essentially, it is the product of selective concentration of milk (casein, fat, and water).

How do you make cheese?

1. Treatment of milk

   1. Clarification, separation, standardisation - this is carried out to reduce high initial bacterial counts before storage.

   2. Pasteurisation - high-temp short-time (HTST)

2. Additives

   1. To improve nutrient loss, add colour and flavour, improve texture, bacterial growth etc.

3. Inoculation and milk ripening

   1. After starter culture inoculation, milk is held at 25-35ºc for 45-60 mins to ensure bacteria are active, growing, and producing acid.

4. Coagulation

   1. Gel is formed by destabilising casein micelles. This causes them to aggregate and form networks that partially immobilise water and trap fat globules in a newly formed matrix.

5. Curd treatment

   1. Milk gel reaches desired firmness after 30-60 mins.

   2. Gel is cut into small pieces with knife blades. Cutting shortens distance and increases available area for whey to be released. This helps determine cheese moisture content.

   3. Curd pieces immediately begin to shrink and expel whey.

   4. When curd reaches desired moisture and acidity, it is separated from whey.

   5. Curd washing

   6. Salting (done through brine, surface salt, or vat salt)

6. Cheese ripening

   1. Temp, relative humidity, and time are closely controlled.

   2. Ripening is carried out until characteristic flavour, body, and texture profile is achieved.

   3. Cheese are dipped in wax and vacuum packed.

   4. Degradation of lactose, proteins, and fat are carried out by ripening agents.

Why do we not homogenise cheese-milk?

Homogenisation disrupts fat globules and increases fat surface area where casein particles absorb.

This results in a soft, weak curd at “renneting” and increases rancidity.

What additives are added in the cheese-making process?

1. Calcium chloride (2-5g/100kg)

   1. Added to replace Ca lost during pasteurisation.

   2. Aids coagulation and reduces amount of rennet required.

2. Colours (e.g. annatto, beta-carotene, paprika)

   1. Standardises colour of cheese throughout the year as milk colour varies from season to season.

3. Hydrogen peroxide

   1. Sometimes added as an alternative treatment for full pasteurisation.

4. Lipases

   1. Ensures proper flavour development throughout fat hydrolysis.

5. Starter cultures

   1. Basis of cheese-making

   2. Lactic acid bacteria (LAB) ferments lactose → lactic acid + gas

   3. Decreases pH to help coagulation, promotes syneresis, prevents spoilage and microbial growth, contributes to texture, and maintains quality.

   4. LAB produces growth factors, encouraging growth of non-starter organisms.

   5. LAB provides lipases and proteases which are necessary for flavour development during curing.

What are the 3 types of coagulation treatment?

1. Enzyme treatment

   1. Rennet - fermentation produces chymosins.

   2. pH of milk lowers, causing aggregation.

   3. Makes cheddar, parmesan, swiss, mozarella.

2. Acid treatment

   1. Achieved naturally (with starter cultures) or artificially (with gluconeodeltalactone)

   2. Acid curd is more fragile than rennet curd - this is due to loss of calcium.

   3. Makes cottage cheese, quark, and cream cheese.

3. Heat and acid treatment

   1. Heat causes denaturation of whey proteins.

   2. Denatured proteins interact with caseins.

   3. Addition of acid causes caseins to precipitate with whey proteins.

   4. Makes paneer, ricotta, and queso blanco.

What is the purpose of curd washing?

• Increase moisture content

• Reduce lactose content

• Reduce final acidity

• Decrease firmness

• Increase openness of texture

What are some ripening agents?

• Bacteria and enzymes of milk

• Lactic culture

• Rennet

• Lipases

• Added moulds or yeast

• Environmental contaminants

What is an emulsion?

An emulsion is a dispersion of one fluid into another.

The fluids are immiscible (one fluid is dispersed as small spherical droplets into the other).

2 phases:

1. Continuous phase - the substance that makes us the surrounding fluid.

2. Discontinuous phase - the substance that is broken up and suspended in the other.

An emulsion is formed when oil, water, and emulsifier are mixed.

The emulsifier coats the emulsion droplets, preventing them from coalescing or recombining with each other.

What are the 2 types of emulsion?

1. Oil in water emulsion (O/W) - oil droplets are dispersed in an aqueous phase.

2. Water in oil emulsion (W/O) - water droplets are dispersed in an oil phase.

What is butter?

Butter is an unfermented dairy product made by churning pasteurised cream (40% fat) at cooled temps (<10ºc).

Churning breaks the fat globule membranes. This breaks the emulsion, causing fat to coalesce, and water escapes.

Contains 80% milk fat.

What are 2 types of butter?

1. Sweet cream butter

2. Cultured or sour cream butter

What are 3 types of butter?

1. Unsalted

2. Salted

3. Extra-salted

What is the composition of butter?

Fat = 80% fat

Water = 16% (dispersed in fine droplets, so butter looks dry)

Salt = 1.2%

Protein, calcium, phosphorous = 1.2%

Fat soluble vitamins A, D, E, K

What are the physicochemical characteristics of butter?

Colour should be uniform

Dense and taste “clean”

Smooth consistency (easy to spread and melt readily on tongue)

How do we make butter?

1. Pasteurisation

2. Chilling at 5ºc for 2 hours

   1. Induces growth of fat crystals

3. Heat treatment in ageing tank

   1. Provides fat with crystalline structure when it solidifies upon cooling.

4. Chilling for 12-15 hours

   1. So fat can crystallise

      1. Rapid cooling = many small crystals

      2. Gradual cooling = fewer larger crystals (gives softer texture)

5. Pumped into the churn

   1. Cream is whipped with air - violent agitation breaks down fat globules.

   2. Phase-inversion - changing from a fat-in-water emulsion (cream) to a water-in-fat emulsion (butter).

   3. Churning stops and drainage of buttermilk when butter grains have reached a certain size.

6. Butter is kneaded and worked

   1. Breaks up embedded pockets of buttermilk or water into tiny droplets that are evenly dispersed in the fat. This also prevents bacterial growth.

7. Salting

   1. To improve flavour and shelf-life.

   2. Batch production - salt is spread over surface of butter.

   3. Continuous production - salt slurry is added to the butter.

8. Butter is worked again

   1. To ensure salt is evenly distributed.

   2. Influences product characteristics (e.g. aroma, taste, keeping quality, appearance, colour.

What is ripened butter?

A fermented dairy product made from cream cultured with LAB.

Cream is ripened to pH 5.5 at 21ºc and then pH 4.6 at 13ºc before churning.

Butter isn’t washed or salted.

What is ice cream?

An unfermented dairy product, composed of:

• Milk fat >10%

• Milk solids-non-fat = 9-12%

  • Proteins - casein and whey

  • Carbs - lactose

• Sweeteners = 12-16%

  • A combination of sucrose- and glucose-based corn syrup

• Stabilisers and emulsifiers = 0.2-0.5%

• Water (from milk) = 55-64%

What are the components of ice cream?

1. Fat

   1. Provides creaminess and improves melting resistance by stabilising air structures.

2. Milk solids-non-fat

   1. Stabilises structure of ice cream due to water-binding and emulsifying effect.

3. Sweeteners

   1. Provides a level of sweetness that consumers prefer.

   2. E.g. sugar, glucose syrups, honey, chemical sweeteners (e.g. aspartame)

4. Stabilisers

   1. Increase viscosity of mix and creates body and texture.

   2. Controls growth of ice crystals and improves melting resistance.

   3. E.g. gelatin, carboxymethylcellulose, locust bean gum, guar gum.

5. Emulsifiers

   1. E.g. egg yolk, glycerol monostearate

   2. Develops appropriate fat structure and air distribution for smooth eating and meltdown.

   3. Controls excessive churning of fat during the freezing process.

6. Flavours

   1. Essences (e.g. vanilla) added before freezing

   2. Solids (e.g. nuts, fruit, etc) are added after freezing.

   3. Chocolate is added to mix before pasteurisation as it often contains undesirable bacteria.

How do we make ice cream?

1. Blending of mix ingredients

   1. Mix is heated to 50-60ºc to effect good mixing.

2. Pasteurisation

   1. 80-85ºc for 15-30s

3. Homogenisation

   1. Occurs at 75ºc.

   2. Essential for smooth texture and even dispersion of ingredients.

   3. Reduces size of fat globules, thus increasing surface area.

   4. Controls whippability and churning during freezing.

4. Chilling and ageing the mix

   1. 2-5ºc for 4-24 hours

   2. Ageing allows for:

      1. Fat to cool down and crystallise

      2. Proteins and polysaccharides to fully hydrate and stabilise gel formation.

5. (soft) Freezing (50% of water is frozen)

   1. Occurs at -1 to -9ºc.

   2. Beating to incorporate air and freezing in scraped surface heat exchanger.

   3. A fine, even foam is required.

6. Packaging

   1. Addition of particulate matter (e.g. fruits, nuts, candy, etc)

   2. Consistency is the same as soft serve.

7. Hardening (90% of water is frozen)

   1. Ice cream is cooled to -35ºc in a blast freezer.

      1. Should be rapid to ensure small ice crystals

      2. Must store ice cream at <-18ºc after hardening.

How to maintain shelf-life of ice cream?

1. Formulate ice cream properly

   1. Sugar considerations

   2. Stabilisers bind free water

2. Freeze ice cream quickly

3. Harden ice cream rapidly

4. Avoid temp fluctuations during storage and distribution

What are ultra-processed foods?

Formulations of ingredients that result from a series of industrial processes.

What are the 4 NOVA food classifications?

1. Unprocessed or minimally processed foods

   1. Foods which did not undergo processing or underwent minimal processing techniques, such as fractioning, grinding, pasteurisation.

   2. E.g. legumes, vegetables, fruits, starchy roots and tubers, grains, nuts, beef, eggs, chicken, milk.

2. Processed culinary ingredients

   1. Obtained from minimally processed foods and used to season, cook, and create culinary dishes.

   2. E.g. sugar, salt, vegetable oils, butter.

3. Processed foods

   1. Unprocessed or minimally processed foods or culinary dishes which have added processed culinary ingredients.

   2. E.g. canned vegetables or meat in salt solution, fruit in juice/syrup or candied, bread, cheeses, purees, pastes.

4. Ultra-processed foods

   1. Food products derived from foods or parts of foods, they have cosmetic food additives not used in culinary.

   2. E.g. breast milk substitutes, infant formulas, cookies, ice cream, ready-to-eat meals, soft drinks, hamburgers, nuggets.

What makes food ultra-processed?

• Contains industrial formulations of substances derived from foods with little or no whole food (fractioning of whole foods).

• Low nutritional quality

• Made palatable or hyperpalatable by adding:

  • Colouring, flavourings, emulsifiers, thickeners, etc.

What are some common ingredients in ultra-processed foods?

• High fructose corn syrup

• Hydrogenated fats

• Modified starches

• Artificial sweeteners

What are some typical processes used for making ultra-processed foods?

1. Extrusion

   1. Subjecting raw materials to extreme pressure, friction, and heat.

   2. Used for breakfast cereals, instant noodles, corn chips, plant-based meat.

2. Hydrogenation

   1. Pumping H2 through liquid oil (saturated fat) to convert it to solid fat (saturated fat).

   2. Used for making margarine, certain peanut butters, commercial baked goods.

3. Hydrolysation

   1. Using enzymes to break large proteins into peptides and AAs, and starches and fibres into simple sugars.

   2. Used for protein powders and shakes, infant formula, instant soups.

4. Moulding

   1. Raw ingredients are broken down into molecular compounds, recombined with additives, and then pumped into moulds.

   2. Used for production or chocolate, bread, biscuits, pies.

5. Pre-processing for frying

   1. Raw foods are stripped of natural fibre and nutrients, mixed with additives, extruded, and moulded, and then flash-fried or par-fried to partially cook it and set its shape.

   2. Used for french fries, shaped potato snacks, processed meat products (e.g. chicken nuggets and fish fingers).

What are the health concerns of consuming ultra-processed foods?

UPF consumption is associated with:

• Increased overweight and obesity

• High waist circumference

• Low HDL cholesterol

• Metabolic syndrome

• Increased risk of CVD

• Cerebrovascular disease

• Depression

What are some foods you may not realise are ultra-processed foods?

• Breakfast foods

• Protein and muesli bars and balls

• Plant-based milks

• Packaged breads

• Yoghurts

• Meal bases and sauces

What is meat grading?

Carcasses are given a quality grade.

This establishes and maintains uniform trading standards and aids in the determination of various meat cuts.

Dentition (no. of teeth), weight, and fat depth are used to define the animal’s meat class and grading.

What factors determine meat quality?

• Breed

• Hereditary

• Sex

• Feeding

• Pre-slaughter and slaughter conditions

• Dressing

• Carcass cooling

• Storage conditions

What is the general composition of meat?

70% water

21% protein

8% fat

1% minerals

What is the Human Slaughter Act (1960)

Requires that, prior to slaughter, animals must be rendered completely unconscious with minimal excitement and discomfort, by mechanical, electrical, or chemical methods.

What is the slaughter process?

1. Stunning

   1. Rendering the animal unconscious, preventing them from feeling any pain or distress during exsanguination.

2. Sticking

   1. Severing major blood vessels in neck or thorax, causing the animal to bleed to death (exsanguination).

3. Skinning/dehairing and Evisceration

   1. Removing skin (and hair/feathers), gut, and non-edible body parts in such a way to prevent/reduce contact with dirt.

4. Inspection

   1. Identifying abnormalities or disease that would make the meat and edible offal unfit for human consumption.

5. Washing and Grading

   1. Spraying water to remove surface blood and bone dust.

   2. Effectiveness may be improved by using hot water or by including low concs of organic acids, chlorine, or other agents.

6. Refrigeration

   1. Carcasses are chilled for 24-48 hours before grading and processing.

What changes take place in muscle immediately after slaughter to convert it to meat?

1. Muscle contracts and stiffens (rigor mortis)

2. As rigor mortis begins, muscle becomes progressively less tender until RM is complete.

   1. Beef = 6-12 hours for RM to complete

   2. Pork = 1-6 hours for RM to complete

3. Chilling should occur immediately after slaughter to prevent carcass spoilage

What is cold-shortening?

If carcass is chilled too quickly before rigor mortis completes, causing subsequent toughness.

What is thaw rigor?

If carcass is frozen before rigor mortis completion, causing extremely tough meat.

What happens in the meat ageing process?

After rigor mortis completion, changes take place resulting in beef becoming more and more tender.

The ageing process involves holding the meat in the fridge.

During this time, tenderness increases due to natural enzymatic changes taking place in the muscle.

Tenderness increases continue for 7-10 days post-slaughter.

Beef should be held at ~2ºc.

If held at higher temps, the beef will tenderise more rapidly but may also spoil and develop off-flavours.

What are the components of meat palatability?

1. Tenderness (varies significantly from one cut to the next)

2. Juiceness (limited variation)

3. Flavour (limited variation)

What are different methods of tenderising meat?

1. Genetics

2. Species and age

3. Feeding (indirect effect)

4. Muscle type

5. Carcass suspension

6. Electrical stimulation

7. Chilling rate

8. Mechanical tenderising

9. Chemical tenderising

10. Marinading

11. Freezing

12. Thawing

13. Cooking

14. Carving

How does genetics influence meat tenderness?

Genetics account for 45% of observed variation in cooked beef tenderness.

How does species and age influence meat tenderness?

Species:

• Tenderness variation: beef < lamb < pork < veal (most tender)

Age:

• Chronological age of animal at the time of slaughter.

• Tenderness decreases as animal gets older (due to collagen)

How does feeding influence meat tenderness?

Animals “finished” with grain reach slaughter-weight sooner than animals “finished” with pasture (grain-fed) to same slaughter weight.

Thus, grain-fed animals are more tender because they are slaughtered at an earlier/younger age.

How does muscle type influence meat tenderness?

There is considerable variation among muscles within species.

E.g. tenderloin is more tender than the fore shank or heel of beef round.

How does carcass suspension influence meat tenderness?

Muscle stretching during chilling affects tenderness.

How does electrical stimulation influence meat tenderness?

Done to “hot” carcass immediately after slaughter to increase tenderness.

1 minute of high-voltage electrical current improves tenderness of many carcass cuts.

How does chilling rate influence meat tenderness?

If carcass is rapidly chilled (cold shortening) it will decrease tenderness.

Instead, we want a more slow/gradual chilling process.

How does mechanical tenderising influence meat tenderness?

Grinding to increase tenderness

How does chemical tenderising influence meat tenderness?

Addition of salt at certain concentrations to increase meat tenderness.

Salt tenderises meat by softening collagen into a more tender form.

How does marinading influence meat tenderness?

Improves tenderness and adds taste variety.

Ingredients include salt, acid, enzymes, and alcohol.

How does freezing influence meat tenderness?

When meat is frozen quickly, small ice crystals form, decreasing tenderness.

When meat is frozen slowly, large ice crystals form, increasing tenderness.

• This is because the large ice crystals disrupt components of meat muscle forces.

• However, slow freezing increases juice loss upon thawing. Juice loss causes meat to be less juicy upon cooking, causing it to be perceived as less tender.

How does thawing influence meat tenderness?

Thawing done slowly in a refrigerator generally results in greater tenderness, in comparison to cooking from a frozen state.

Slow thawing minimises toughness effect from cold-shortening and reduces amount of moisture loss.

How does cooking influence meat tenderness?

As cooking progresses, contractile meat proteins become less tender and collagen becomes more tender.

How does carving influence meat tenderness?

Consumers should carve cooked meat at right angles to length of muscle fibre (against the grain) to achieve maximum tenderness.

Cutting “with the grain” causes stringiness, so is less tender.

What is meat curing?

Meat curing was originally used as a preservative method.

It is now used for flavour and colour enhancement.

What ingredients act as “curing agents”?

1. Salt - preserves and adds flavour.

2. Sodium nitrate and sodium nitrite - preserves and “fixes” the red colour of meat.

3. Sugar - provides colour stability and flavour.

4. Spices - produces desired flavour

What determines meat colour?

Myoglobin is a protein that acts as the primary colour pigment of meat.

It functions to store oxygen in muscle tissue.

Myoglobin is denatured by prolonged air exposure or by cooking (changes from red to brown).

• Oxygenated = bright-red meat colour

• Deoxygenated = purplish meat colour

How is meat colour influenced by the 3 forms of myoglobin?

3 forms of myoglobin:

1. Deoxymyoglobin

   1. Ferrous iron (Fe2+)

   2. Purplish-red colour

   3. Found in freshly cut meat with little oxygen exposure.

2. Oxymyoglobin

   1. Oxygen bound to ferrous iron

   2. Bright red colour

   3. Preferred by consumers

3. Metmyoglobin

   1. Ferric iron (Fe3+)

   2. Brown colour

   3. Associated with meat ageing and oxidation

What factors determine the interconversion of the 3 forms of myoglobin?

1. Oxygen availability

2. Storage temperature

3. Light exposure

4. Microbial activity

5. Redox potential

What are the benefits of meat smoking?

• Protects fat from rancidity

• Contributes to colour characteristics

• Creates unique flavours in processed meats

• When used with other preservation techniques, smoking is the most effective microbial growth inhibitor.

What is the protocol for freezing meat?

Properly wrapped fresh meat cuts are held at -18ºc.

For fatty meats (e.g. pork), they can only be held in these conditions for months.

• Storage time is limited because, at freezer temperatures, fat gradually oxidises, producing off flavours.

Beef can be held for years.

Once frozen, meat should not be thawed and refrozen.

Few cured meats or sausages are frozen, this is because the salt in their formulation increases rate of rancid flavour development and spice flavours may change during frozen storage.

What cooking method should be used for cuts low in connective tissue (e.g. steaks and chops from rib and loin)?

Dry heat cooking (e.g. pan frying, broiling, roasting, grilling, BBQ)

Dry heat rises temp very quickly, this allows the meat flavour to develop before contractile proteins have had the opportunity to become less tender.

What cooking method should be used for cuts high in connective tissue (e.g. fore shank, heel or round, chuck)?

Long and slow cooking at low temps using moist heat (e.g. braising).

Moist heat application for a long time at low temps (135-165ºc) results in tough collagen converting into tender gelatine - this makes the cut more tender than if they were cooked with dry heat.

What cooking method should be used for lean meats (e.g. chicken, turkey, sirloin steak, pork tenderloin)?

Heating causes contractile proteins to toughen and moisture is lost, decreasing tenderness.

Cooked to rare degree of “doneness”:

• Rare = 60ºc internal temp

• Medium = 68ºc internal temp

• Well-done = 77ºc internal temp

What cooking method should be used for

What cooking method should be used for