Course: BFM 201 Ethanol Production

Unit 5 Readings and Lecture

To Do:
Read Textbook: Ethanol Process Fundamentals – Chapter 4 pages 4.4 – 4.11
Cook and Liquefaction

From the Slurry Tank the slurry is passed through a jet cooker that heats the slurry to 220^o F utilizing steam. This helps to liquefy the starch and it also sterilizes the slurry to reduce levels of bacteria. The high heat in the jet cooker deactivates the first dose of alpha amylase enzyme that was added in the slurry tank. The slurry is sent from the jet cooker to a holding column for 5 – 10 minutes. From the holding columns, the slurry is passed into a liquefaction tank and is now called “mash." The remaining 2/3rds of the enzyme alpha amylase are added to the mash which is kept in the liquefaction tank for approximately 8 hours at 185^0 F and at a pH of 5.6 – 6.0. The purpose of the cook and liquefaction process is to break down the long starch polymers to shorter length polymers called dextrin. The mash should now have a low viscosity, a dextrose level of 2-3% and have 29 -30% solids. We will look at determining dextrin equivalent and solids content in the lab.

A second enzyme called gluco-amylase is used to further breakdown the dextrin polymers to individual glucose (sugar) molecules referred to as dextrose or fermentable sugars. Some facilities add the gluco amylase during the cook and liquefaction phase before the fermentation tank. This is called “saccharification." Some ethanol facilities have started adding the gluco amylase directly to the fermentation tank. This is called simultaneous saccharification.

Key Terms |
Enzymes | A substance produced by microorganisms that acts as a catalyst to promote chemical processes without it being altered or destroyed.
pH | A measure of the acidity or alkalinity of a solution, where 7 is neutral; lower numbers are acid; higher numbers are alkaline.
Liquefaction | The change in the phase of a substance to the liquid state; in fermentation, the conversion of water-insoluble carbohydrate (starch) to water-soluble carbohydrate (dextrin).
Yeast | A microscopic fungus consisting of single oval cells that reproduce by budding that can change sugar into alcohol and carbon dioxide by fermentation.
Hydrolysis | The cooking of mash; the chemical breakdown of organic materials through the use of water.
Saccharification | The process of hydrolyzing a complex carbohydrate into a simpler soluble fermentable sugar, such as glucose or maltose. This is also referred to as conversion.
Temperature | It is important to control temperatures during the cook and liquefaction process for effective preparation, maximized enzyme action, and strong fermentation.
Dosage | It is important to learn correct dosages to use and how to measure the amount of enzymes, yeast, pH (acid or alkali) and additional nutrients to use in the process.
Sugar content | The key to knowing how much alcohol fuel you are going to get in a batch is its sugar content. You will measure sugar content with a refractometer.
Nutrition | Yeast need additional nutrition to thrive.
Gelatinization | An effect that can occur during the process of making starches soluble in water, using heat or a combination of heat and enzymes. “The starch grains swell and rupture; the outer layers absorb water and lose their crystalline structure; the outer layers become adhesive and form a sticky gel. During the cook process, the long chains of starch granules are broken down through the use of water, heat, and enzymes. The longer chains are broken down to smaller chains which allow the enzymes to work on greater surface area of starch.
Denaturation | The process of proteins losing their structure.
References:

Jacques, K. A., Lyons, T. P., & Kelsall, D. R. (2003). Chapter 2. In The alcohol textbook: A reference for the beverage, fuel and industrial alcohol industries. Nottingham: Nottingham University Press.

Chapter 4. (2006). In Ethanol process fundamentals: An introduction to ethanol processing. Granite Falls, MN: Minnesota Energy Enterprise Center.

Blume, D., Fuller, R. B., & Winks, M. (2007). Chapter 7. In David Blume's Alcohol can be a gas!: Fueling an ethanol revolution for the 21st century. Santa Cruz, CA: International Institute for Ecological Agriculture.