Food Preservation Techniques: Dehydration

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Questions and Answers

What is one purpose of dehydration in food preservation?

Increases the need for preservatives

Prevents all nutrient loss

Extends shelf life by reducing water activity (correct)

Enhances flavor substantially

What does food irradiation primarily reduce or eliminate?

Flavor compounds

Nutritional value

Chemical additives

Disease-causing microorganisms (correct)

Color changes like browning during drying can be prevented with proper treatment.

True (A)

What is the ideal drying temperature for food?

65–70°C Signup and view all the answers

Food treated with irradiation becomes radioactive.

False (B) Signup and view all the answers

Which food items typically require a drying time of 6–16 hours?

Vegetables (D) Signup and view all the answers

The process of removing water from food through heat application is called __________.

dehydration Signup and view all the answers

What is the maximum energy level achieved by accelerated electrons in food irradiation?

10 MeV Signup and view all the answers

High moisture foods such as lettuce are suitable for drying.

False (B) Signup and view all the answers

Match the following dried foods with their categories:

Coffee = Commercial dried food Egg powder = Dried ingredient Raisins = Commercial dried food Yeasts = Dried ingredient Signup and view all the answers

Irradiation can be described as '________ pasteurization' as it achieves similar safety objectives without high temperature.

cold Signup and view all the answers

What effect does drying have on microbial spoilage?

It reduces microbial spoilage. Signup and view all the answers

Which of the following factors does NOT affect the drying process?

Type of food packaging (A) Signup and view all the answers

The primary objective of drying is to reduce _____ content in food.

water Signup and view all the answers

Which of the following is NOT a characteristic of the electron beam irradiation method?

Requires frequent replenishment (B) Signup and view all the answers

Match the following food items with their type of radiation treatment:

Potatoes = Ionizing radiation Onions = E-Beams Cereals = Cold pasteurization Poultry = Thermal pasteurization Signup and view all the answers

Match the food types with their typical drying times:

Vegetables = 6-16 hours Fruits = up to 48 hours Grains = 10-15% moisture content Lettuce = unsuitable for drying Signup and view all the answers

Dehydrated food contains more than 2.5% water.

False (B) Signup and view all the answers

What is a disadvantage of using Co60 pencils in food irradiation?

Requires frequent replenishment Signup and view all the answers

What happens to the drying rate if the size of food particles is smaller?

Drying time decreases (B) Signup and view all the answers

What is the oldest method of preserving food through dehydration?

Solar/sun drying Signup and view all the answers

Lower atmospheric pressure during drying allows for evaporation at higher temperatures.

False (B) Signup and view all the answers

Irradiation serves as an effective technology for preventing foodborne diseases.

True (A) Signup and view all the answers

What is the impact of temperature on the drying process?

Low temperatures encourage microbial growth. Signup and view all the answers

Study Notes

Food Preservation Techniques

Dehydration: Removing water from food to extend shelf life. Foods dehydrated to less than 2.5% water are considered dried.
Dehydration Theory: Heat application combines with moisture removal to extend shelf life. Examples include dried foods like coffee, milk, raisins, pasta, beans, and spices.
Dehydration Process: Oldest method is solar drying, followed by pre-treatments to preserve color and flavor, and drying the food whole or transforming it into powder (e.g., powdered milk, dried fish).
Dehydration Principles: All organisms need water, dehydration stops spoilage by decreasing water activity and enzyme activity, and reduces microbial spoilage, concentrating sugars in fruits.
Factors Affecting Drying: Drying temperature (65-70°C initially, dropping to 60°C), moisture content (less than 20% for fruits, 10% for vegetables, 10-15% for grains), relative humidity, airflow velocity, drying time, tray loading, food particle size, and atmospheric pressure and vacuum.
Advantages of Dehydration: Intermediate step in creating retail products, inhibits microbial growth, cost-effective packaging and storage, and ready-to-eat foods (no refrigeration needed).

Other Preservation Techniques

Freezing: The process of converting a substance from a liquid to a solid state by removing heat.
Freezing Principles: Low temperatures inhibit reaction rates and microbial growth, and reduce moisture for growth. This also preserves taste, texture, and nutrients compared to other methods.
Freezing Methods & Equipment: Uses air blast, plate, or cryogenic freezing, and fluidized bed or spiral freezers.
Freezing Quality: Fast freezing creates small ice crystals for better texture; slow freezing creates larger crystals, causing loss of quality. Storage temperature needs to be maintained at low temperatures to prevent recrystallization. Food preparation methods like blanching are used to inactivate enzymes and packaging to prevent freezer burn.
Freezing Point Depression: Solutes lower the freezing point and causes water expansion, affecting volume and texture.
Irradiation: Exposing food to controlled ionizing radiation for preservation.
Irradiation Techniques: Gamma rays, electron beams, and X-rays. Gamma rays and X-rays penetrate deeply, useful for packed food, while electron beams have lesser penetration, suitable for thin products.
Irradiation Mechanism: Damages microbial DNA, preventing reproduction, and altering cell membranes. It affects food quality by breaking chemical bonds, impacting vitamins and proteins.
Contemporary Preservation Techniques: High Pressure Processing (HPP) uses pressure up to 900 MPa in liquid-submerged products to inactivate microorganisms. Pulsed Electric Field (PEF) uses high-voltage pulses for inactivation of pathogens in liquid foods. Ultrasound waves use sonic waves to damage membranes and cause bacterial death. Pulsed light uses high-energy light pulses for surface decontamination.

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Description

Explore the various food preservation techniques with a focus on dehydration. Learn about the processes, principles, and factors affecting drying, along with examples of dehydrated foods. This quiz delves into the science behind extending shelf life through moisture removal.