Naturally

Keeping natural yeast needs regular refreshing in the initial stage.  Discarding half of the culture and refreshing with the same amount always seems so wasteful.  Nevertheless, this is a procedure needed to ensure the strength of the yeast.

After receiving some starter from Chef William, I refreshed the portion which supposed to be discarded and use it to make Blueberry Muffins from the recipe by Sanjin Ko.

To test if the refreshed yeast, which turned bubbly, is ready for use, simply scoop some from the lot and drop it onto a container of water.  If it floats, means it is ripe for using. Mine is ready and the container which has the culture felt so light.

I wasn't sure about the texture of the baked muffins so I brought some for Chef William to determine.
Chef confirmed on the texture and added that crumbs made with natural yeast culture would never be similar to commercial yeast.  Whilst the latter will be more crumbly, those that are made with natural yeast will be moist and bread-like.  I prefer those made with natural yeast.