M E A T A N D P O U L T R Y P R E S E R V A T I O N

Question 1

LOW TEMPERATURE PRESERVATION

Answer 1

• Low temperature preservation can be divided into freezing (-18 to -40°C), superchilling (-2 to -4°C), ice temperature (0 to -2 °C) and refrigeration (0 to 4 °C).

• The optimal temperature and technology of low temperature preservation vary depending on meat samples.

Question 2

Definition of chilling

Answer 2

Reducing the temperature of a product to 0°C (melting point of ice)

Question 3

Purpose of chilling

Answer 3

Prolong shelf life by slowing down deterioration processes (enzymatic, bacterial, chemical, physical)

Question 4

Chilling (Micoorganism)

Answer 4

• Pathogenic microorganisms grow rapidly in the
range of 10-37°C, slowly in the range of 3.3-10°C,
and can no longer grow below 3.3°C

• Mesophilic and thermophilic microorganisms are
greatly retarded at chilling temperatures

• Psychotropic microorganisms grow well in the
range of 0-15°C

Question 5

Icing

Answer 5

Chilling with ice is an extremely effective means of reducing the temperature on the poultry.

Question 6

Effective way of chilling (Icing)

Answer 6

• For effective chilling, the ice must be allowed to melt; there are additional advantages in this as melting ice keeps the chicken both moist and glossy, adding to its attractiveness to the consumer.

• The ice melt water also helps to wash away surface bacteria and clean the chicken.

Question 7

Advantages of Ice (Icing)

Answer 7

1) Large cooling capacity for its weight,

2) No health hazards,

3) Easily transported,

4) ) MeIt-water makes good contact with chickens, melt-water keeps chicken moist, and preventing dehydration

Question 8

Disadvantages of wet ice

Answer 8

The use of wet ice has several disadvantages, including driploss, decreased protein extractability, and nutrient loss.

Question 9

Dry-ice

Answer 9

• Dry ice (solid carbon dioxide) is an effective alternative, as it rapidly reduces the temperature, has a bacteriostatic effect, and acts as an insulant.

• The use of dry ice alone is generally not recommended due to its high cost.

Question 10

Advantages of Carbon Dioxide

Answer 10

• Carbon dioxide possesses several advantages as a cooling agent, easy handling, simple transportation, and long-term preservation.

Question 11

Super-chilling

Answer 11

• It is commonly used to preserve meat by lowering the temperature to between -1°C to -3°C.

• This forms a thin layer of ice on the surface that helps keep the food fresh.

• Super-chilled food has a longer shelf life than chilled food, but not as long as frozen food.

• Super-chilling can prevent bacterial growth and
spoilage.

• However, it can also affect enzymes that break down the food.

• May cause dehydration

Question 12

REFRIGERATION

Answer 12

• Chicken cooled in cold air can become dry due to moisture loss from the surface.

• Keep the temperature of the display case at or below 4°C to prevent bacterial growth and ensure the freshness of the product.

• Sale of meat : a refrigerated meat is stored at temperature between -1 to 10 degree C

• Humidity should be over 90% with low air velocity to minimize dehydration.

• Keep the product in its original packaging or airtight container to prevent contamination and drying out.

Question 13

Refrigerants

Answer 13

• Refrigerants are chemicals used in refrigeration and air conditioning systems.

• Halocarbons, which contain chlorine, fluorine, or
bromine, were commonly used but have a negative
impact on the environment.

• Hydrocarbons (HCs) may be used as alternative
refrigerants because they have zero ozone depletion potential and low global warming potential.

• Ammonia is widely used in large industrial refrigeration plants because it’s inexpensive, readily available, and has a high latent heat of vaporization and low boiling point.

• Carbon dioxide is also used as a refrigerant and is non-toxic, non-flammable, and non-explosive.

Question 14

Common problems (Cold Shortening)

Answer 14

1) Quick chilling associated to cold shortening – the most common.

2) Cold shortening can often be seen in beef and mutton, when the meat, still in its pre-rigor phase, reaches temperatures of 10°C or lower.

3) These conditions cause irreversible contractions of the muscle tissue, which toughen the meat even after prolonged ripening.

4) Solution: delay chilling or chill at 15-16°C

Question 15

FREEZING

Answer 15

• Freezing involves lowering the temperature to -18ºC or below - no water is available to promote enzymatic reactions or bacterial growth.

• Poultry and meat starts freezing at -1°C to -3°C

Question 16

Three Stages of Freezing:

Answer 16

Stage 1: Temperature decreases just below 0°C, removes sensible heat

Stage 2: Thermal arrest period at around -1°C, removes latent heat

Stage 3: Temperature decreases sharply, allowing freezing of remaining water

Question 17

Disadvantages of freezing

Answer 17

✓lower customer demand
✓difficulty in identifying whether product has been abused.
✓Bone darkening
✓Freezer burn

Question 18

Bone darkening

Answer 18

This occurs due to leaking of the pigment from
bone marrow during freezing. Commonly, it is seen in the drumstick and thigh bone.

Question 19

Freezer burn

Answer 19

A term for the moisture lost from frozen food. It’s
what happens when meat left in your freezer for a long time loses moisture and begins to look discolored , spongy, or soft edges, surrounded by ice crystal and with slight off and rancid smell.

Question 20

Air-blast Freezer

Answer 20

• Air blast freezing freezes food products using
circulated cold air.

• There are two types of air blast freezing: tunnel
freezing and fluidized bed freezing.

Question 21

Tunnel freezing

Answer 21

Involves slowly moving the product on a belt through a tunnel with very cold air, either in parallel or opposite direction of the product flow.

This method creates a temperature difference between the air and the evaporator, leading to frost build-up

Question 22

Fluidized bed freezing

Answer 22

Involves placing the product on a mesh belt and exposing them to forced air moving upward through the bed. This method is ideal for individually quick-frozen products.

Question 23

Advantages & Disadvantages of Air-Blast Freezer

Answer 23

• Air blast freezing is fast, flexible, and can freeze a wide range of products.

• However, it can cause problems such as dehydration and freezer burn due to high-velocity air.

• Dehydration can be controlled by pre-cooling products with high humidity air and applying a thin layer of ice or “glazing” to exclude air from the surface.

Question 24

Plate or Indirect Contact Freezer

Answer 24

• Usually used for individual meat patties and patties packaged in wrapped trays.

• Products are placed in direct contact with very cold (e.g., -12°C to -35°C) metal freezer plates or shelves

• Plate freezing can also be used for thinly packed meat (fillets).

Question 25

Plate or Indirect Contact Freezer (Mechanism)

Answer 25

• Heat transfer is by conduction.

• The thermal conductivity of the freezer plates is much higher than circulating air and therefore, used to quickly freeze meat.

• Using plates from both sides as well as colder plates can increase the freezing rate.

Question 26

Immersion Freezer

Answer 26

• Direct contact with low-freezing-point liquid leads to rapid freezing and high-quality end product.

• Used for smaller products (e.g., cut up meat, cubes, nuggets) and, sometimes, larger trims.

• Immersion solutions are limited and include propylene glycol, glycerol, mixtures of salt and sugar, and combined solutions.

• Sodium chloride brine is the most widely used
immersion solution but may cause meat to absorb salt.

• For large meat parts, it’s common to form a crust on the outside before freezing. The meat is transferred to an air blast freezer to complete the process.

Question 27

Cryogenic Freezers

Answer 27

• The term of “cryogenic” simply means very low temperatures; and in food freezing, it refers almost exclusively to liquid nitrogen and liquid carbon
dioxide systems.

• Cryogenic freezing promotes uniform and rapid nucleation, formation of smaller ice-crystals, and minimizes cell damage, resulting in better product
quality.

• However, in current costs per kilogram frozen product, freezing with liquid cryogenic is more expensive than mechanical refrigerated freezing due to the high cost of the fluids.

Question 28

Liquid Nitrogen (LN)

Answer 28

• Liquid nitrogen at atmospheric pressure
vaporizes at -196°C.

• Typical liquid nitrogen freezer is designed as a
tunnel, with liquid nitrogen spray heads located
near to the exit end.

• The food product is placed in a container or on a
tray, and liquid nitrogen is poured or sprayed
over the product until it is fully submerged.

Question 29

Liquid Nitrogen (LN) Characteristics

Answer 29

• Liquid nitrogen is non-toxic, inert, protects
against oxygenic reactions, and ensures quick
freezing at very low temperatures

Question 30

Carbon Dioxide (CO2)

Answer 30

• Carbon dioxide at atmospheric pressure vaporizes
at -78 °C.

• As liquid carbon dioxide vents to the atmosphere,
it appears as “snow” in the freezer cabinet.

• If compressed into blocks, this snow would
become as “dry ice”.

• The solid snow then converts into a vapor as it
absorbs the heat of sublimation from the freezing
product.

Question 31

Common problems

Answer 31

• Slow freezing causes water to move out of muscle cells and form large ice crystals during freezing.

• Frozen storage can result in poor taste and texture of the meat, including changes in texture, granular fat, and discoloration.

• Freezer burn is a dry, porous area that can occur on packaged meats with loose packaging, leading to rancidity and flavor transfer.

• Solution: vacuum package

Question 32

Thawing

Answer 32

• Thawing is a critical phase in the freezing process, as it can cause microbial reactivation and change ice
crystals to melted water, which must be efficiently reabsorbed.

• Thawing should be done at low temperatures below 5°C to reduce the risk of microbial growth and with a low level of air circulation.

• Thawing of beef carcasses lasts about four to five days, and smaller carcasses take one to three days.

Question 33

HEATING

Answer 33

• Heat treatment causes physical-chemical alterations in meat that result in beneficial sensory
and hygienic effects on processed products.

• When bacteria are exposed to heat, the number of survivors decreases logarithmically with heating time at a constant temperature.

Question 34

Pasteurization

Answer 34

• It is a moderate heating process at 60-90°C, designed to inactivate some of the spoilage and most of the pathogenic bacteria.

• The shelf life of the product is extended but the product must be refrigerated.

Question 35

Sterilization

Answer 35

• Food products are prepared using a temperature of more than 100°C.

• The aim is to create “commercially sterile” food products.

• These products can be stored at room temperature for an extended period of time.

• The process aims to kill all spoilage microorganisms, food poisoning bacteria, and spores.

• However, this process alters the meat in terms of texture, flavor, and odor.

Question 36

Canning

Answer 36

• Canned meat products are sealed in tin coated steel cans and heat processed to destroy microorganisms (hermetically sealing).

• There are two categories of canned meat products: sterilized and pasteurized.

Question 37

Sterilized products (Canning)

Answer 37

• Sterilized products are heated to an internal temperature of at least 101°C (heating temperature of 121 °C) and are shelf stable.

• In commercially sterile canned meat, all microorganisms, including spores, are destroyed or made dormant.

• Canned products are processed in a retort cooker that operates under 12-15 psi pressure.

Question 38

Retort pouch

Answer 38

• Retort pouch is a heat-resistant laminated plastic package used for processed food products.

• It’s sterilized at high temperatures up to 121°C to make the product shelf-stable.

Question 39

Characteristics of Retort pouch

Answer 39

• The pouch can be made from aluminium foil-based plastic laminates or foil-free plastic laminate films.

• Most pouches are made of three or four-ply laminates with an inner food contact heat-seal layer, a barrier layer, an optional nylon layer, and an outer polyester layer.

• All components, including inks and adhesives, must withstand high temperatures during retort processing.

Question 40

Thermal Death Time

Answer 40

• Sterilization means destroying or deactivating
microorganisms, especially Clostridium botulinum in food.

• This is done by heating the food to a high temperature of 121.1°C for a certain amount of time, which is measured by the sterilizing value, F0.

• The goal is to achieve a 12D sterilization criterion, which means reducing the initial number of microorganisms by 12 orders of magnitude.

Question 41

Recommended Fo Value

Answer 41

• The FDA recommends a minimum F0 value of 3 minutes for commercial sterilization of low-acid foods to ensure safety.

• If the total F value so found is below 2.8 min, then
sterilization is not sufficient.

Question 42

Critical factors in ensuring food safety in the canning and retort pouch:

Answer 42

i. Container seal integrity: the lid and container must be of good quality to prevent air, moisture, and contaminants from entering

ii. Adequate thermal process lethality: achieved through heating or pasteurization, must be done properly to destroy harmful microorganisms in the food

iii.Scrupulous post-process hygiene: including cleaning and sanitizing equipment, utensils, and surfaces to prevent contamination and ensure the product remains safe for consumption.

iv.Headspace: The headspace for most products processed in cans at 116-121° C, should be no less than 6% and no more than 10%.

Question 43

CHEMICALS

Answer 43

• The most common additive has been salt, which, at a high enough level, can reduce water activity such that microorganisms can not grow.

• Other chemical preservatives, such as smoke, have been used for centuries in conjunction with drying to produce shelf stable products.

Question 44

Salt

Answer 44

• Sodium chloride (NaCl) is used to preserve meat by
lowering water activity and reducing the water
available for microbial growth.

• High salt concentrations can interfere with cell
metabolism, draw water from the cell, and cause
plasmolysis, which inhibits growth and can kill the cell.

• A concentration of 10-15% salt should be used to make a food product shelf stable, which is much higher than the 1.0-2.5% salt commonly used in most meat products.

Question 45

Phosphate

Answer 45

• Phosphates, such as tripolyphosphate (TPP), can alter pH, cause a salt imbalance outside bacterial cells, and emulsify fat.

• Phosphate rinses and dips can be used for decontaminating fresh meat and have been successfully used as antimicrobial agents for removing bacteria from meat, including poultry skin.

Question 46

Nitrite

Answer 46

• Nitrite, as sodium nitrite (NaNO2), sodium nitrate (NaNO3), or potassium salts, is used in the curing process of different meat products.

• Nitrite is added to inhibit the growth of harmful microorganisms such as Clostridium botulinum and other spoilage microorganisms.

• Nitrite also stabilizes the pink meat color in cured meats by forming the nitrosohemochrome complex and contributes to flavor development while
inhibiting oxidation.

Question 47

Acids

Answer 47

• Marinating meat cuts with ingredients such as lemon juice and vinegar is inhibitory to many pathogens and can also help extend shelf life.

• Lactic acid is produced within the product by lactic acid bacteria or added as an encapsulated acid to help reduce pH and preserve the product in
fermented/acidified meat products.

Question 48

Sorbic acid

Answer 48

• Sorbic acid is a preservative used as a fungal inhibitor and, more specifically, as an inhibitor of mold growth on products such as meat and bread.

• Meat – uncooked manufactured other than meatburger, sorbic acid maximum permitted proportion 400 mg/kg

• Sorbic acid can be used as a spray on fermented sausages as it works best below pH 6 and is not effective above pH 6.5.

Question 49

Smoke

Answer 49

• Smoke has been used for centuries to preserve meat and other foods due to the antimicrobial compounds released when wood is burned

• The concentration of these compounds in smoke depends on the type of wood used and the burning temperature.

• Most smoked meat products are only lightly smoked to enhance exterior color, contribute special flavor notes, and provide some antimicrobial inhibition, resulting in a surface-level bacteriostatic/bactericidal effect.

Question 50

The four main groups of compounds that have a
bacteriostatic and/or bactericidal effect in smoke

Answer 50

1) Phenols
2) Ketones
3) Aldehyde
4) Organic Acids

Question 51

DRYING

Answer 51

• The scientific principle of drying is to reduce water activity (Aw) to a level that inhibits microorganism growth.

• Dried foods typically contain ≤ 25% moisture and have an Aw of 0.05 to 0.60, while intermediate-moisture foods have 15 to 50% moisture and Aw between 0.60 and 0.85

Question 52

Basic principles of drying

Answer 52

• Different types of dryer are used for different methods of heating: convection, radiation, dielectric, or conduction.

• The most common driers used in the food industry are convective or air driers, which work either continuously or in batches.

• In drying: (a) the latent heat of vaporization must be supplied
(b) the moisture must be transported out from the food.

Question 53

The variables that determine the time of drying of a food product are related to

Answer 53

i. the drying (temperature, velocity, humidity, flow characteristics, etc.) and

ii. the product (moisture, size, shape, structure, etc.)

Question 54

MECHANICAL DRYING

Answer 54

• Mechanical drying involves the use of electricity to
operate heaters and fans.

• Although more expensive than natural methods,
mechanical drying allows fine control of temperature, humidity and air flow

Question 55

Cabinet drying

Answer 55

A cabinet dryer is a type of dryer that uses forced
convection to remove moisture from the meat.

It consists of a cabinet or chamber with shelves or trays on which the meats are placed for drying.

A fan or blower circulates hot air through the chamber, and vents or exhaust ports allow the moist air to escape.

Question 56

Vacuum drying

Answer 56

During a vacuum drying operation, the material to be dried is placed in a vacuum chamber, which is then evacuated to a specific level of vacuum using a vacuum pump.

Once the desired vacuum level is reached, heat is applied to the chamber, either through conduction or convection, to transfer heat to the material being dried.

As the material heats up, moisture or other
volatile substances are evaporated and removed from the chamber by the vacuum pump

Question 57

Freeze drying

Answer 57

With freeze drying, meat is placed in a vacuum where moisture from the meat is drawn out under low pressure.

This moisture changes from liquid to gas, using up heat energy from the meat. This results in
rapid freezing as well as drying.

Meat freeze at the point where approximately 15% of the water has evaporated.

Freeze drying requires high energy input, so is only
feasible for valuable products.

Freeze dried meat may be stored indefinitely under natural conditions, provided that the packaging remains impervious to water.

Question 58

Modified Atmosphere Packaging (MAP)

Answer 58

• MAP is a technique that involves changing the composition of the atmosphere surrounding the meat to reduce the rate of microbial growth
and oxidative reactions.

Question 59

MAP Mechanism

Answer 59

• Typically, MAP involves removing air from the package and replacing it with a mixture of gases, such as carbon dioxide, nitrogen, and oxygen, in
specific proportions.

• The gas mixture used in MAP depends on the type of meat, packaging material, storage temperature, and desired shelf life.

• Increased levels of carbon dioxide can inhibit the growth of some bacteria, yeast, and molds, while also reducing oxidative reactions that cause meat
discoloration and rancidity

Question 60

Ohmic heating

Answer 60

• Ohmic heating is a new technique in food processing that uses electricity to generate heat in food.

• It can improve meat quality and safety by reducing
cooking times and bacterial growth.

Question 61

Ohmic heating (Mechanism)

Answer 61

• Electrical current passes through the meat, generating heat, which is evenly distributed due to the meat’s electrical conductivity.

• Ohmic heating generates heat like conventional cooking methods but with faster cooking times and more uniform heating.

Question 62

Ohmic heating (Advantages)

Answer 62

1) Shorter processing times
2) Higher yield
3) Less power consumption

Question 63

Irradiation

Answer 63

• Food irradiation is a process of treating a food to a
specific dosage of ionizing radiation for a predefined
length of time. This process slows or halts spoilage due to the growth of pathogens.

• Sources of ionizing radiation: Gamma rays, x-rays, and electrons beams.

• Low doses radiation (up to 1 kGy) can extend shelf life and reduce bacterial counts, but higher doses can affect texture, flavor, and nutrients.

Question 64

Benefits of irridation

Answer 64

1) Reduced foodborne illnesses

2) Longer shelf life

3) Less waste

4) Reduced needd for preservatives

Question 65

UV Radiation

Answer 65

• Ultraviolet (UV) radiation is not commonly used to treat meat.

• It is a non-thermal technology that minimizes nutrient and sensorial quality loss, leaves no toxic residues, and consumes less energy than other thermal treatments.

• UV is an electromagnetic radiation with an emission spectrum in the wavelength range of 100 nm–400 nm.

• There are numerous devices that can generate ultraviolet light, such as mercury vapor lamps, pulsed xenon lamp, and LEDs

• UV light can penetrate and destroy the DNA of bacteria and viruses, which can help to reduce the risk of foodborne illness

Question 66

Ozonation

Answer 66

• Ozone is produced by passing air or oxygen through a highenergyelectric field or UV-radiation.

• Ozone is effective in destroying bacteria, fungi, viruses, and vegetative cells. Ozone kills bacteria, then transforms into ordinary oxygen.

Question 67

Advantages & Disadvantages of Ozonation

Answer 67

• Ozone treatment of food products results in little or no chemical residues and pollutants in processed products.

• Ozone treatment in meat can lead to discoloration due to the oxidation of myoglobin and oxymyoglobin to metmyoglobin.