Although it is permissible to cook and bake on Yom Tob, not everything necessary for food preparation is allowed. For example, the Sages enacted a prohibition against plucking fruits and vegetables on Yom Tob, even if one plans on eating them that day. Another exception is squeezing fruits to prepare fruit juice. On Shabbat, as we know, squeezing fruits is forbidden, and squeezing certain fruits (grapes and olives) is forbidden on the level of Torah prohibition. This prohibition applies on Yom Tob, as well. Although food preparation is generally allowed on Yom Tob, squeezing fruits for juice marks an exception. And thus it would be forbidden to use a juicer on Yom Tob to squeeze fruits, even if one wants to drink the juice that day. The Helkat Yaakob (Rav Mordechai Yaakov Breish, Zurich, 1895-1976) suggested allowing the use of a juicer on Yom Tob, because the apparatus extracts both the juice and the pulp from the fruit, such that no actual separation is being done. Hacham Ovadia Yosef, however, in Hazon Ovadia Yom Tob (pp. 73-74), disputes this ruling, and rules that juicing fruits on Yom Tob is forbidden. This Halacha is codified in Yalkut Yosef (p. 131).
Summary: Although food preparation is generally allowed on Yom Tob, one may not squeeze fruits on Yom Tob to extract juice, even if one wishes to drink the juice that day.
