There isn’t much that you can’t put into a juicer, and some juicers are different to others, but as a general rule you can’t put Bananas, Mangos or ice into a juicer, these should all be blended.
Now Avocado depends on the juicer. You can’t put avocado through a Centrifugal juicer as it will just get splattered against the inside of the bowl as the blade spins. If you have a centrifugal juicer than you will need to blend the avocado in with the juice that you have made.
With the Optimum 600 masticating juicer, you can put it through, just make sure you take out the stone and remove the skin! It’s a good idea to put the avocado in early so that when you add more juicer fruits or veg, the liquid will help to push the avocado out of the bowl.
Now pineapple is fine to put through either juicer, but with both juicers, it’s a good idea to put it in last as the fibres of a pineapple are very tough and it does seem to clog up most juicers. The Optimum 600 deals with it really well by the way.
Now you can technically juice berries, but because they are so small it’s more beneficial to blend them as you will be getting more of their nutrients. Berries, in my opinion are the best things to make smoothies with anyway!
Now as I mentioned above, juicers do vary in performance, and as you get used to your juicer you will find out what techniques are best to use with it, you may find that putting a certain food in first or last gives better results. For example, when I use The Optimum 600, if I’m making a green juice, I will put spinach or Kale in 2nd to last before the pineapple as I find that as the leaves spin around the auger, it seems to wipe clean any excess food that has risen from the auger…a nice “cleaning cheat”.
Please ALWAYS read the instruction manual that comes with your juicer, it is written by the people that make the thing so they will have a good idea on what works and what doesn’t.