What is the history of the microwave? How does it work ?
Magnetron generates microwave radio signals In WWII - used in tracking the enemy Post War - used for heating food
What are microwaves ? (1/3)
Nonionizing waves of energy that create thermal changes
What are microwaves ? (2/3)
Do not cause dangerous chemical changes (as do ionizing rays)
What are microwaves ? (3/3)
Absorbed, transferred or reflected depending on the composition of the material with which it is in contact
How do microwave ovens work ?
Transfer of heat via electromagnetic radiation Waves Magnetron Dielectric heating
What is a magnetron ?
Vacuum electron tube that converts household electricity into microwaves. -emits microwaves set in motion by a fan -turntable helps cook evenly - different power outputs
What are the two different power outputs of a magnetron?
Général: 500-750 watts Commercial: 1000-1300
How do waves function in microwaves ?
Emitted from an opening in the metal case Reflected off the sides and penetrate food in the process
How does dielectric heating work in microwaves ?
-High frequency and alternating electromagnetic field heats a dielectric material -polarity reversals
What are the two major interactions in dielectric heating ?
1) dipolar rotation molecules (with positive and negative pokes) 2) ionic conduction (electrically charged ions) BOTH types generate heat by friction and transfer to other molecules by conduction
Recommended containers for microwaving ?
- must be able to TRANSFER microwaves (not absorb or reflect) -round -shallow No recycled paper or brown bags No metals dishes
Why round containers ?
Fan is circular - even heating. Microwaves enter only 1 inch into food.
Why no metals dishes ?
Arching Accumulation of electrons Not « terrible » why?
What are some guidelines for using metal ?
- reasonably large -Kept away from walls - metal/foil is grounded along the bottom of the microwave
Why should you stir food in microwave?
Since food is only heated writhing 1in, stir to endure thorough cooking
Can you microwave spoons or forks?
Spoons are a better choice - don’t build up charge, rather spread charge around the spoon = less sparking
How should you arrange containers in a microwave ?
-foods cook from the OUTSIDE ! Position heavier / denser portions on the outside Whenever heating multiple items - the center should be left empty
Name some ways to prepare food for the microwave
-Pierce foods encased in skin/peel -Shield portions that may be over cooked Cover foods to hold moisture, avoid spattering and retain heat
How can you cover food in microwave ?
-paper towels -wax paper -microwavable covers -cover loosely to let steam escape
What is the microwave cooking concept ?
Microwaves penetrate the food unevenly
What are the 3 things about the microwave cooking process ?
1) stirring 2) rearranging / rotations 3) standing time
What determines standing times ?
1) the amount of time it takes for food molecules to stop vibrating after microwave process ends 2) cooking continues during this period of time, so it is factored into the recipes time requirement
What are the factors affecting microwave cooking process ?
Density Volume Starting temps Shape of food Composition of food
Why cook vegetables in the microwave ?
Retains vitamins and minerals
Name some cooking tips about vegetables in the microwave
-cooked quickly, covered and a little water added to prevent moisture loss -cut pieces into similar sized thin pieces, arranged in a single layer or loose pile -some items best cooked with conventional methods
When is it okay to cook meat in microwave ? When is it not okay? Is it ideal ?
NOT ideal Ok for thawing / reheating leftovers Not Ok for large cuts of meat
Why is cooking meat in microwave not ideal ?
Dries out meat, no browning (flavour not developed) temps not high enough to kill pathogens
What’s a pathogen not killed in microwaving Meat?
What are some cooking tips when microwaving meat ?
-tender cuts produce better results - should be covered with added liquid -shutdowns not be salted until end of cooking period to avoid a toughening effect
Is cooking fish in the microwave ideal? why ?When is it not ideal?
IS Ideal -thin dimension/tenderness of fillets and steaks Not ideal -deep fried fish, live lobster, reheating fish.
What are some cooking tips when microwaving fish?
1) Food should be covered (so surface doesn't dry and toughen) 2) prevent overcooking of thin portions by using foil, or overlap pieces to yield a consistent thickness.
How can you cover fish in the microwave ?
1) Wrap fish in parchment 2) Wrap container in plastic wrap 3) use 2 inverted plates
Can eggs be cooked in microwave? when can they not?
can be cooked very quickly, so must be careful. Works well for shambles, poached, omelet. Does not work for fried or whole.
Are cakes, cookies and breads recommended to be cooked in the microwave ?
Why aren't cakes and cookies recommended to be cooked in the microwave ?
-Cake crust does not brown -Angel food cakes, chiffon caked, meringue are too heat sensitive Look for cookies and cake mixes available for microwave.
Why are breads not recommended to cook in the microwave?
No dry heat for dextrinization , maillard reaction and caramelization.
Are cereals recommended to cook in the microwave ?
yes, if instant hot cereals. Other grains have no significant decrease in cooking time.
Do foods brown in the microwave ?
No, and do not crisp either.
What are some additional ingredients that can be added to create a browning effect?
-Teriyaki/soy sauce -BBQ sauce -Worcestershire/steak sauce -bread crumbs -shredded cheese -brown sugar -nuts -jellies, preserves and glazes.
What are some safety concerns regarding microwaves ?
1) Do not operate when empty to prevent overheating 2) Prevent burns by: -Using oven mitts -lifting lids/wrap away from you -using microwave safe dishes
What is microbiological safety ?
-Destruction of microorganisms by heat depends on TEMP and TIME of food is heated. -Quick and uneven increase in them and short maintenance time = greater survival of bacteria and parasites Microwave cooking NOT recommended for home canning.
What are some advantages to microwave cooking?
1) Speed of cooking is 3-4 x faster 2) Absence of cookingheatin kitchen 3) Energy saving 4) Quick & easy clean up
What are some disadvantages of microwave cooking ?
-Lack of browning -May dry out food items' (esp meat) -Lack of slow cooking -Not usually practical for large quantities