41. Although " preheating " makes some sense, as you are heating the oven before putting the dish in it. 42. Some preliminary tasks, such as preheating ovens and bringing water to a boil, are done in advance of each round. 43. 4 . Space evenly apart on a parchment-lined cookie sheet and chill for 15 minutes while preheating oven to 400 degrees. 44. Cooking with light as opposed to microwaves or raw heat provides maximum flexibility and versatility _ and there's no preheating required. 45. Its lead-acid rechargeable battery was sensitive to shock, required frequent maintenance before use, and required preheating for best performance. 46. *Preheating is useful if you are cooking something based strictly on time, for example, at 300 degrees for an hour. 47. By preheating the oven you create the pocket of hot air desired for baking and then the burners turn themselves down / off. 48. Like a microwave oven, it requires no preheating , and it cooks food in about a third the time of a standard oven. 49. Additional material and heat balances can be made to quantify the thermal advantage from preheating the combustion air, or enriching it in oxygen. 50. One could also replace L-glutamic acid with L-glutamine without preheating it in an oil bath and then add phosphoric acid.
