Absolutely! While it may not have a pleasant texture (usually tough/dry compared to the outer flesh), it's still entirely edible and can 100% be juiced or blended (though it may struggle more in the latter). In fact, the core contains several minerals (and fiber, which you can take advantage of when using the leftover juice pulp). Just note that the pineapple core can be more irritative to the tongue/mouth, so enjoy it in moderation.