When preparing hot emulsified egg yolk sauces, make as much as is needed. Although these sauces can be stored overnight in the refrigerator and melted and beaten into a fresh egg yolk the next day, the longer a sauce is kept, the greater the danger of bacterial contamination. Because these sauces are kept warm rather than hot while being held before service, they are a perfect medium for bacteria. If sauce has been kept warm for more than two or three hours, it is best to discard any that is left over. If only a small amount of sauce was prepared and it was not held for more than two hours, it can be stored overnight and reconstituted the next day. Remember, when storing emulsified egg yolk sauces overnight, to date the container with the date the sauce was first made. An emulsified egg yolk sauce should never be reconstituted more than once.