All berries can be ‘pulped’, mashed, squashed, squished (insert your preferred word here!) to remove the seed from the skin and flesh.
At the same time, non-viable seed – often empty – can be removed.
Aim to get the balance between squashing too hard (you risk breaking the seeds) and too gently. Err on the side of caution until you get used to how much pressure you can apply.
The berries are ‘de-bunched’ (removed from the stalks) and placed about 1/3 full in a bucket and crushed to a pulp using a tool with a flat bottom.
If the fruits are not soft enough, they can be left for a while to ripen further or soaked in cold water for a few days, changing the soaking water each day.
Separating seed from fruit
Once reduced to a pulp, it is a simple matter of separating the viable seed from the skin and flesh of the fruit and the empty seeds by sieving.
A jet of water is directed onto the pulp until the bucket is almost full. The first few times you do this may produce a lot of froth. This is reduced by pouring all the contents of the bucket (water and seeds) through a sieve two or three times until it clears.
Pour off the waste (and pop it on the compost heap)
Once clear, more water is added. Make sure everything is thoroughly mixed. The heavy, viable seeds sink reasonably quickly (depending on their size) and the waste can be carefully poured off with the water through a sieve, leaving the viable seed in the bottom of the bucket. This can be repeated as many times as necessary to remove as much waste as possible.
It is not necessary, or practical, to aim for completely clean seed.