Yeast is extracted primarily through a process called autolysis, where yeast cells are broken down and separated into their constituent components. This process allows for the extraction of valuable yeast extracts, often used as flavor enhancers and nutritional supplements. Here's a breakdown of the extraction process:
Autolysis: Breaking Down the Yeast
-
Heating: The process begins by heating the yeast cells. This heat treatment serves two main purposes:
- Cell Rupture: The heat causes the yeast cells to rupture, releasing their internal contents.
- Enzyme Activation: The heat activates the yeast's own digestive enzymes (proteases).
-
Enzymatic Breakdown: Once the cells are ruptured, the activated enzymes start to break down the complex proteins within the yeast cells into simpler compounds such as amino acids and peptides. This enzymatic self-digestion is the core of autolysis.
Separation and Purification
-
Centrifugation: After autolysis is complete, the mixture contains soluble components (amino acids, peptides) and insoluble cell walls. Centrifugation is used to separate these components. The insoluble cell walls are heavier and form a pellet at the bottom of the centrifuge tube, while the soluble extract remains in the liquid supernatant.
-
Filtration: The supernatant liquid, now rich in yeast extract, may undergo further filtration to remove any remaining particulate matter and improve its clarity and purity.
-
Drying: Finally, the filtered yeast extract is typically spray-dried to create a concentrated powder. This powder form is easier to handle, store, and incorporate into various food products and applications.
In Summary: The extraction of yeast involves heating the yeast to rupture cells and activate enzymes for self-digestion (autolysis), followed by centrifugation and filtration to separate and purify the soluble yeast extract. The extract is often spray-dried for ease of use.
