FDSCI 3.1 Cold Preservation of foods

Why is proper cold storage important for food?

Incorrect or inconsistent temperatures cause changes in taste, texture, appearance, nutrients, and safety.

How much is storage life reduced for every 5°F above desired freezer temp?

It is cut in half.

What percentage of consumers use refrigerator thermometers?

Only about 20%.

When was refrigeration first used in the U.S.?

Mid-1800s.

Who pioneered food freezing processes in the 1920s?

Clarence Birdseye.

What percentage of foods are refrigerated during processing?

Over 85%.

What percent of supermarket energy costs come from refrigeration?

About 50%.

How much of global energy use is from refrigeration systems?

About 15%.

At what temperature range should household refrigerators be set?

4.5–7°C (40–45°F), with 3.5°C (38°F) as optimal.

What temperature should freezers be set at?

0°F (-18°C) or below.

What temperature range is considered the “danger zone”?

40–140°F for over one hour.

What is the ideal temperature range for storing meat, poultry, and fish?

31–35°F (just above freezing).

What are psychrotrophic microorganisms?

Microbes that grow slowly at refrigeration temperatures.

Name two psychrotrophic pathogens.

Listeria and Yersinia.

Does freezing completely destroy microorganisms?

No, it only stops most activity; microbes can grow after thawing.

What temperature does pure water freeze at?

0°C (32°F).

Why do foods freeze below 0°C?

Solutes in the food cause freezing point depression.

What is the most common commercial freezing method?

Air-blast freezing.

What is plate-type freezing?

Food is placed between cold metal plates at about -28°F for 1–4 hours.

What is cryogenic or immersion freezing?

Foods are frozen with liquid gases like nitrogen (-320°F) or dry ice (-110°F).

What does IQF stand for?

Individually Quick Frozen.

What is dehydrocooling?

Cooling foods by evaporation of water under vacuum.

What is brine cooling used for?

Chilling seafoods and processed meats with cold saltwater.

Name two refrigerants once used but later regulated or banned.

Ammonia and Freon (CFCs like R-12).

What international treaty banned CFCs?

The Montreal Protocol (1996).

What is freezing point depression?

Lowering of a liquid’s freezing temperature due to dissolved solutes.

What are some unfavorable changes in refrigerated foods?

Color loss, oxidation, nutrient loss, microbial spoilage, and flavor absorption.

What is one benefit of refrigeration for food quality?

It slows microbial growth and enzymatic reactions.

What is dehydrofreezing?

Evaporative cooling before freezing to reduce water and freezing time.

What are the FDA’s three safe methods for thawing frozen foods?

In the refrigerator below 40°F, under running water below 70°F, or during cooking.

How does slow freezing affect product quality compared to rapid freezing?

Slow freezing forms large ice crystals and causes more damage to texture.