In a recipe you might see :
"remuer jusqu'à ce que le mélange blanchisse",
"battre jusqu'à ce que le mélange blanchisse", sometimes also "et fasse le ruban".
It is used to mix eggs and sugar.
When you mix sugar and eggs, you know they are well mixed when the colour turns from a bright yellow into a very clear yellow :
It also changes into a very smooth texture :
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