Lesson 8: Refrigeration as a Food Preservation Method

Refrigeration (chilling and freezing)

Drying

Heating

Fermentation

Additives (salt, sugar, vinegar)

What are the traditional methods for food preservation

Refrigeration

What preservation causes the least physical and chemical changes in foods that is referred for fresh, high-value foods.

Microorganisms

Environmental

Refrigeration Considerations:

• Does not eliminate _______ → so it is sensitive to the_______ conditions.

Chilling
Freezing
Cold storage
Refrigerated transport
Retail display
Domestic storage

Refrigeration includes this type

Initial

Refrigeration retards spoilage but cannot improve _____ quality

• That's why it is important assuring particularly high microbial quality in starting material 
  

temporary

Is refrigeration a temporary or permanent preservation?

Storage temperature

Shelf life depends on what temperature?

Maintained

Cold preservation works only if temperature is ___________.

Importance of maintaining reliable cold chain all along the commercial life of the product

Hurdle principle

What principle happen in refrigeration where it is combined with other method since it is temporary?

Microbial growth

Biochemical changes

Refrigeration is the process of lowering food temperature to slow:

• A

• B
  

Household

Industry

Refrigeration is used in _____ and _____.

Tropical climate

Why is refrigeration crucial in Ph?

Meat
Fish
Dairy
Fruits (mango, banana)

Refrigeration is common in these foods

Chilling: 0°C to 8°C (above freezing point)

Freezing: Below −18°C (well below freezing point)

Temperature used for chilling and freezing?

Chilling

0°C to 8°C (above freezing point)?

Freezing

Below −18°C (well below freezing point)

Ancient & Pre-Industrial Practices

Ice Harvesting & Iceboxes (17th–19th Century)

Industrial Revolution

Freezing Technology

What are the 4 parts of history of refrigeration

Ancient China (~1000 BCE)

When was mountain ice/snow was used

Ancient Egypt & India

When was evaporative cooling technique
was used

Persia (modern Iran)

When was Yakhchals (ice houses) invented

Romans & Greeks

When was stored snow/ice in pits invented

1600s-1800

When was ice cut from lakes, stored in icehouses or insulated cellars happened

Early 1800’s

When was ice trade grew in the U.S, where ice was shipped internationally. 

1834

When was Jacob Perkins built the first working vapor-compression refrigeration machine

1851

When was James Harrison of Australia – developed mechanical refrigeration using ether, alcohol, or ammonia (for breweries and meat packing)

1859

When was Ferdinand Carré, French engineer – invented first refrigeration machine

1861

When was first U.S. ice-making machine

1873

When was cold storage warehouses appeared in the UK, U.S.

1918

When was William C. Durant started Frigidaire Company 

1920s

When was Clarence Birdseye, American inventor observed Inuit freezing techniques

1920s

When was Clarence Birdseye Developed quick freezing using cold brine and air blast freezing

1925

When was Birdseye innovation led to founding frozen food industry with improved texture, taste, and shelf life 

Jacob Perkins

He built the first working vapor-compression refrigeration machine in 1834

James Harrison of Australia

They developed mechanical refrigeration using ether, alcohol, or ammonia (for breweries and meat packing)

Ferdinand Carré

A  French engineer that invented first refrigeration machine

William C. Durant

He started Frigidaire Company 

 Clarence Birdseye

An American inventor observed Inuit freezing techniques

• Developed quick freezing using cold brine and air blast freezing

Cool cellars/pits

Iceboxes

Imported ice

What are the examples of “Before” equipment’s for refrigeration

Cold Storage Warehouses

Blast Chillers/Freezers

Freezers

Refrigerators

What are the examples of “Before” equipment’s for refrigeration

Cool cellars/pits

They were among the earliest forms of food refrigeration 

Iceboxes

Early domestic appliances used before electric refrigerators that functioned as insulated cabinets

19th

Imported ice un ____ century, large blocks of natural ice were harvested during winter and stored or transported

Cold Storage Warehouses

Modern equipment for storing frozen chicken, pork, and imported beef

Ports

Commercial facilities often located in ____ (e.g., Navotas Fish Port or agricultural industrial zones)

Blast Chillers/Freezers

Modern equipment used by food processing companies like San Miguel, Monterey

• For rapid freezing (e.g., hotdogs, chicken cuts)

Freezers

Modern equipment used to store tocino, longganisa, ice cream

Refrigerators

Modern equipment used in homes, restaurants, carinderias, sari-sari stores

• Brands: Panasonic, LG, Haier

Enhanced insulation
Energy efficiency
Smart temperature controls

Solar-powered cold storage (e.g., Mindanao remote parts)

Improvement highlights for modern equipment?

A non container sea, road and rail transport equipment

A non container sea, road and rail transport equipment or Air transport

• In addition to intermodal refrigerated containers, which may be used across sea, road and rail transport

  • There are also equipment specifically for each mode of transport

Air transport

A non container sea, road and rail transport equipment or Air transport

• Used for high value products

• Uses special insulated containers that are smaller than ship containers and may be cooled by phase change materials, dry ice, or battery powered mechanical refrigeration units

Special insulated containers

Air transport uses ___________ that are smaller than ship containers and may be cooled by phase change materials, dry ice, or battery powered mechanical refrigeration units

Sea Transport

Road Transport

Rail Transport

What are three equipment for food transport (modern)

Sea Transport

Examples for sea transport equipment

Refrigerated wagons

Examples for rail transport equipment?

Refrigerated panel vans

Examples for road transport equipment road Transport

Chilling

0C to 5C or 32F to 41F 

A short term food preservation method that slows down microbial growth and enzymatic activity by lowering temperature

• what temp?

Freshness, texture, and nutritional value

Chilling helps retain ___ ____ ____ without freezing the product

Air Chilling

Blast Chilling (Forced-Air Cooling)

Hydrocooling (Water Cooling)

Vacuum Cooling

Contact Plate Chilling

Cryogenic Chilling

Types of chilling methods

Microbial safety

Nutritional value
Organoleptic properties (appearance, flavor, texture)

Refrigeration and freezing are critical steps in post processing handling of foods. These processes help to:

• Maintains:

  • a

  • b

  • c

Organoleptic properties

What properties are appearance, flavor, texture

Cured & packaged

Cooked, packed

Blanched & pureed

Cleaned, vacuum-sealed

Heat treated

What are the processing methods for these products?

• Tocino / Longganisa

• RTE Meals

• Fruit Purees

• Vacuum-packed fish

• Pasteurized milk

Stored at -18°C

Blast frozen

IQF to preserve

Chilled at 0–2°C

Stored at 4°C

What are the processing role or temp for these products?

• Tocino / Longganisa

• RTE Meals

• Fruit Purees

• Vacuum-packed fish

• Pasteurized milk

Pampanga products

Adobo for OFWs

Guimaras mango

Tuna from GenSan

Carabao milk (Nueva Ecija)

Complete the table

Product	Processing Method	Role	Philippine Example
Tocino / Longganisa	Cured & packaged	Stored at -18°C
RTE Meals	Cooked, packed	Blast frozen
Fruit Purees	Blanched & pureed	IQF to preserve
Vacuum-packed fish	Cleaned, vacuum-sealed	Chilled at 0–2°C
Pasteurized milk	Heat treated	Stored at 4°C

Stored at -18°C

Blast frozen

IQF to preserve

Chilled at 0–2°C

Stored at 4°C

Product	Processing Method	Role	Philippine Example
Tocino / Longganisa	Cured & packaged		Pampanga products
RTE Meals	Cooked, packed		Adobo for OFWs
Fruit Purees	Blanched & pureed		Guimaras mango
Vacuum-packed fish	Cleaned, vacuum-sealed		Tuna from GenSan
Pasteurized milk	Heat treated		Carabao milk (Nueva Ecija)

Complete the table

Cured & packaged

Cooked, packed

Blanched & pureed

Cleaned, vacuum-sealed

Heat treated

Product	Processing Method	Role	Philippine Example
Tocino / Longganisa		Stored at -18°C	Pampanga products
RTE Meals		Blast frozen	Adobo for OFWs
Fruit Purees		IQF to preserve	Guimaras mango
Vacuum-packed fish		Chilled at 0–2°C	Tuna from GenSan
Pasteurized milk		Stored at 4°C	Carabao milk (Nueva Ecija)

Complete the table

Ice Crystal Formation

Moisture Migration

Viscosity and Texture

What are the physical changes of freezing and chilling?

Ice Crystal Formation

What physical changes where water in food forms crystals during freezing

Slow freezing

• Slow freezing or Fast freezing

  • Large crystals → Cell damage → Texture loss

Fast freezing

• Slow freezing or Fast freezing

  • Small crystals → Less damage → Better quality
    

Viscosity and Texture

What physical changes where cold temperature increases viscosity (thicker texture in dairy) and freezing weakens protein gels (seen in frozen tofu becoming spongy

Moisture Migration

What physical changes where during chilling, moisture may migrate from inside to the surface → dehydration or freezer burn

Is most common from surface drying and oxidation (common in poorly wrapped meat)

Cold

Freezing

Viscosity and Texture

• ___ temperature increases viscosity (thicker texture in dairy)

• ____ weakens protein gels (seen in frozen tofu becoming spongy)

Nutrient Loss

Protein Denaturation

Lipid Oxidation

Carbohydrate Changes

Flavor and Aroma

Enzymatic Activity

What chemical changes where water in food forms crystals during freezing

Yes

Yes or No. When food is stored at low temperature, whether refrigeration (0-4 C) or freezing (-18 C or below), chemical reactions are slowed but not completely stopped. 

Ongoing enzymatic activity (if not inactivated before storage)

Exposure to oxygen and light

Physical disruptions from freezing

Moisture loss or migration

Freeze-thaw cycle

Chemical changes occur due to?

Vitamin C/B complex

In nutrient loss, what vitamins are mostly lost?

Oxygen

Light

Heat

Vitamin C are highly unstable and degrade in the presence of

ascorbic

In chilled fruits and vegetables, ____ acid gradually oxidizes overtime

Oxidizes

In chilled fruits and vegetables, ascorbic acid gradually _____ overtime

Blanching

Freezing slows degradation but _____ (common in vegetables) before freezing may cause some initial loss 

Protein

In chemical changes, it remain chemically intact, but structure changes may happen, especially during freezing and thawing

Ice crystals

In protein denaturation, ________ disrupt muscle fibers in meat and fish

Changes in pH or salt concentration

In protein denaturation, _______ or _________ in frozen processed foods can lead to protein unfolding 

Dry or tough textures

Water loss

Loss of emulsifying/gelation properties

Denatured protein may result in?

Lipid Oxidation

This happens when fats in food, especially unsaturated fats react with oxygen that forms peroxides and aldehydes → causes rancid odors and taste

Peroxides and aldehydes

What factors from unsaturated fat causes rancid odors and taste

Oxidative rancidity

It is slowed but not stopped in refrigeration and even freezing 

Lipolysis

It is breakdown of fats by lipase, also continues to happen unless enzymes are inactivated

Vacuum packing

Antioxidants (e.g., Vitamin E)

Limit light exposure

What are the prevention for lipid oxidation

Starch Retrogradation

Sugar Conversion

What are the two carbohydrate changes

Starch Retrogradation

This happens when chilled starchy foods, starch molecules (amylose and amylopectin) reassociate, causing:

• Hardening or staling

• Loss of softness and palatability 

Common in refrigerated rice, bread, kakanin

Sugar Conversion

This happens when some fruits, like bananas, enzymatic activity continues in the fridge, converting starches to sugar: lading to

• Over ripening

• Darkening of skin and pulp 

Hardening or staling

Loss of softness and palatability 

What are the starch retrogradation effects?

Over ripening

Darkening of skin and pulp 

What are the sugar conversion effects?

Flavor and Aroma

What chemical change is when cold temperature reduce volatility of aroma compounds, making food smell less intense

Lose flavor due to oxidation

Absorb off odors from other foods especially in share fridge and freezer space

Upon thawing, previously frozen food can?

Freeze and thaw cycle

Repeated ________ enhance chemical breakdown of flavor molecules

Blanched

Acid-treated

 Enzymatic Activity:

• Still active at cold temps unless:

  • a

  • b

No

Yes or No. Does refrigeration sterilize food?