Angelia Butler
HSCI 345/Dr. Hughes
23 April 2013
Mini Lecture Outline
Chapter 7
I. Microwave Cooking
A. Food-Related Uses
1. Home: microwave ovens used most frequently in the home to boil water, heat
frozen foods, defrost frozen foods, or make popcorn.
a) Speed and convenience
b) Younger members of family also use microwave ovens.
c) Considered safer for older children than oven.
2. Food Service: Heavy duty commercial microwave units primarily used
for reheating.
3. Food Industry: Uses microwave processing largely for meat tempering,
bacon precooking, and sausage cooking.
a) Equipment used to temper 4 billion pounds of meat a year.
b) Tempered by being brought to a temperature just below freezing point
of water where they are not frozen but still firm
II. Action of Microwaves in Heating
A. What are Microwaves?
High-frequency electromagnetic waves of radiant energy
Radio waves of very short wavelengths
Microwaves are generated in a magnetron which converts electric current
into electromagnetic energy radiation.
FCC assigned certain frequencies: 915 and 2,450 megahertz
III. How Do Microwaves Work?
A. Intro
Microwaves interact electrically with polarized molecules in the food.
Polarized molecules (dipolar molecules) act like tiny magnets and align
themselves in the microwave electromagnetic field.
Heat is produced by friction that is created between rapidly moving
molecules.
Positive and negative ions of dissolved salts in the food also migrate toward
oppositely charged regions of the electric field and generate additional heat by
their movement.
Within a microwave oven, the microwaves reach the food that is to be cooked
both directly from the magnetron unit and indirectly by reflection from the metal
walls.
A. Safety and Regulation
Since 1971, FDA has regulated manufacturing of microwave ovens.
Limit of 5 milliwatts of microwave radiation per square centimeter at a
distance of 5 centimeters from the oven surfaces.
B. Microwave Ovens
Designed to function as both a microwave oven and ventilation cooking hood
above a range, thus conserving space.
IV. Advantages of Microwave Cooking
A. Speed of Cooking and Reheating Foods
Cooking is ten times faster than with conventional methods.
Reheats precooked foods more rapidly and avoid reheated or warmed over
flavor.
B. Reduction in Nutrient Loss
Microwave blanching of vegetables compared to blanching in water
resulted in less nutrient loss.
C. Energy Conservation
Can cook up to about six servings at one time.
Do not contribute to the warmth in the home during the hot seasons of the
year.
V. Limitations of Microwave Cooking
A. Surface Browning of Foods
Foods that require cooking for a relatively long time would be greatly
overcooked before browning would occur.
Due to cool air temperature inside the microwave oven and to the cooling
effects of moisture evaporation at the surface of foods cooked with
microwaves.
B. Other Quality Limitations
Dried pasta and rice do not cooks more quickly in the microwave oven
because rehydration must occur.
Sauces and meats do not have an opportunity to develop in the short
cooking periods.
Bread reheated often becomes tougher.
Hydrocolloids (such as xanthan gum)
These and microcrystalline cellulose which have water binding
capabilities help stabilize many microwavable products and prevent dry
spots.
C. Overcooking
Superheated water
Slight movement or addition of instant coffee may cause severe burns or
violent eruptions.
D. Unevenness of Heating and Food Safety
Lack of uniformity in heat distribution
Hot and cold spots
May not destroy Salmonella organisms in chicken or Trichinella spiralis.
Check final temperature of food in several locations of the product.
Voltage being fed in microwave must be consistent at all times that the
oven is operating.
VI. Packaging Materials and Cooking Utensils
A. Microwave Usable Dishes
Use microwave safe plastic, ceramic and glass containers.
Metal or glass containers are generally not acceptable for microwave use.
In some products packaging is already provided when purchased.
Protects the product in storage and distribution, controls heating of product.
Functions as a serving dish and helps to sell product.
VII. General Cooking Suggestions
A. Browning
Smaller quantities of food cooked for short periods must be browned using
other methods other than microwave oven.
Optimum time for cooking should not be extended to increase likelihood
of browning.
B. Stirring and Turning
Power is unevenly distributed so foods must be turned around, stirred,
relocated.
Most come equipped with rotating turntable that distributes power.
C. Standing Time
Food continues to cook several minutes after it’s removed from microwave
oven.
Heat continues to be conducted from hotter parts of food to cooler ones.
D. Defrosting
Heat produced in food is distributed throughout.
Ground meat, stew meat, whole poultry, or whole fish should be turned.
Break apart and separate in over while defrosting is completed.
E. Combining Microwave and Conventional Cooking
Foods can be cooked efficiently if cooked partly by microwave and partly by
conventional methods.
For example, bread can be toasted conventionally and fillings can be
prepared using microwave.
F. Heating Meals
Dielectric (and thermal) properties
Since different foods have properties, uneven heating may occur in meals
with several different components.
Temperatures at edge of plate or tray of food tend to be higher than in the
center.
The edge of the food seems to act as an antenna in the microwave field, absorbing
energy.