Hi @irma-hinahon
-Liquid sourdough or liquid natural ferment is a natural yeast, since it is achieved with the natural fermentation of flour mixed with water and the capture of bacteria from the air. Cooling or feeding this mixture and maintaining a cold temperature.
Liquid sourdough serves to make our breads much tastier, with a good crispy and toasted crust, a spongy crumb and a wonderful aroma, as well as a longer shelf life for the bread.
-Solid sourdough or solid natural ferment is a dough composed of wheat flour, water, salt, dough (bread dough from the previous day, with yeast). This dough undergoes a natural acidifying fermentation, which aims to give greater acidity to the bread dough.
Solid sourdough can be manipulated with your hands precisely because it has a solid texture. When we cool it we make a ball with it which then grows during cooling until it doubles its volume.
The same cannot be said for liquid sourdough, which, being completely liquid, must be handled in containers and with utensils (not with your hands).
This type of solid sourdough provides more rigidity to the final dough. It will take longer to ferment than the liquid. It is generally used for breads that need a certain rigidity, such as a panettone.
In this case for Chef Xavi Ramon’s course, the liquid natural ferment is Poolish and the solid natural ferment would be the sourdough.In chapter 3 you have the preparation of the sourdough or solid natural ferment and in chapter 4 you have the preparation of the poolish or liquid natural ferment.
We hope this information is useful.
Greetings.