Can one squeeze the water or oil from an opened can of TUNA ON SHABBOS assuming a person leaves some water or oil remaining? WHAT IS THE BEST WAY IT CAN BE DONE ON SHABBOS? I like my TUNA without the water.
Thank you for your question.
The answer to your question is controversial. Firstly, we have to differentiate between the liquid on the sides of the tuna, between the tuna and the can, and the water that is absorbed inside the tuna. Regarding the water between the can and the tuna- According to some poskim, it is permitted as the water and the tuna ae all considered the same type. is considered. Others say that it is permitted to turn the can so that the excess water pours out is permitted but only while the water is still flowing, but once the amount of liquid is diminished and it will only drip out, it is borer. While others regard all the oil in the can to be a mixture, and don’t allow even pouring the excess liquid off.
Regarding squeezing the water absorbed inside the tuna, regarding sechita, it would not be an issue, because it is permitted to squeeze absorbed water from a cooked or marinated item in order to improve its taste, which is the reason you want to squeeze the water or oil out. However there is controversy regarding meleches borer. According to some poskim it is permitted to squeeze the water or oil out, because it is considered one type and part of the tuna. However a numerous other poskim consider it similar to a peel, which starts off as part of the fruit, but gets separated because you don’t want it, and it is permitted to remove only if the fruit (and in your instance the tuna will be eaten shortly afterwards.
Therefore it is hard for me to give you a definitive answer, and the best thing is to rmove the water or oil before Shabbos
 Ashrei Hoish O:CH 2 chap. 25-26, and Hilchos Shabbos b’Shabbos chap. 9ftnt. 88 quoting R’ Eliyashiv zt”l, Nishmas Shabbos 4-207.
 Halachos of Shabbos pg. 166, The 39 Melachos pg. 439, 519. The reason they rule this way is because they view the water on the sides of the tuna as excess, and not mixed with the tuna.
 Shmiras Shabbos Khilchoso 3-20 (new edition). The reason he rules stringently is because he considers the water as between the pieces of tuna, therefore all of the water is considered a taaroves. Also see Orchos Shabbos chap. 3 ftnt. 40.
 O:CH 320-7.
 Magen Avrohom 119-16. See Orchos Shabbos chap. 3 41 and ftnt. 40 that it is only permitted if you don’t mind the extra water or oil and removing it doesn’t really matter to you, however if you don’t like the tuna with all the excess water, then it should not be squeezed out of the tuna.
 Pri Megadim M:Z 319-6, Ketzos Hashulchan 115-19, Shmiras Shabbos Khilchoso 5-8 and ftnt. 32,33, Chidushei Basra on M:B 319-25, The Shabbos Kitchen pg. 112,122.