Successful brews require intelligent yeast management. Saccharomyces cerevisiae var., the brewing yeast, is the most important microorganism in beer production. Yeast decisively impacts the fermentation and maturation processes and the quality of the beer. Brewers must understand yeast to consistently produce beer with reliable characteristics.

Popular in Germany, The Yeast in the Brewery, Second Edition, by Gerolf Annemüller, Hans-J. Manger, and Peter Lietz, is now available in English. Relying on fundamental science, the authors describe technical aspects of the industrial application of yeast in the brewing process.

Contents include:

• The history of pure yeast culture development

• The importance of pitching yeast regeneration and the demands of this process on breweries

• Microbiological and biochemical fundamentals of yeast multiplication and how they inform pure yeast culture and yeast propagation

• Overview of the machinery, equipment, and plants needed for pure yeast cultivation

• Recovery of barm from surplus yeast

Gaining both scientific and historical knowledge, readers will receive a complete education in yeast management and learn to apply this information to their own brewing operations.

The Yeast in the Brewery, Second Edition

List of Abbreviations

Introduction and basic concepts

Some historical facts about the development of the pure yeast culture

The discovery of the yeast as a living microorganism
The development of the different yeast strains and their pure culture

The microflora of beer
     Saccharomyces cerevisiae Meyen ex Hansen (1883)
     Bottom fermenting beer yeast
     Top fermenting beer yeast
     Brettanomyces bruxellensis
     Beer spoilage microorganisms
     Sacch. pastorianus Hansen
     Sacch. cerevisiae var. ellipsoideus (Hansen) Stelling-Decker
     Sacch. cerevisiae var. diastaticus
     Saccharomycodes ludwigii
     Schizosacch. Pombe
     Aerobic “wild yeast” as accompanying flora
     Candida mycoderma (Rees) Lodder et Kreger van Rij
     Pichia farinosa (Lindner) Hansen
     Pichia membranaefaciens
     Hansenula anomala (Hansen) H. et P. Sydow
The history of yeast pure cultures

Why it is necessary to regenerate the pitching yeast and what are the demands in the brewery?

Signs of yeast degeneration
Possible causes of the yeast degeneration
Stress factors
Why it is necessary to change (renew) the yeast
Advantages of using a yeast produced in a propagation plant
Requirements for a pitching yeast

Important microbiological and biochemical fundamentals of the yeast multiplication and their significance for the pure yeast culture and for the yeast propagation

The chemical composition of the yeast

The relationship between moisture and dry matter of the yeast
The chemical composition of the yeast dry matter

Some physical reference figures of yeast cells and yeast suspensions of use in designing yeast treatment equipment and for technological calculations

Size of a yeast cell, cell number and biomass concentration
Surface of the yeast cell
Density of the yeast cell
Density and dry matter values of yeast suspensions and of yeast products
Rheological parameters of yeast slurries
Calculation of the pressure drop of yeast suspensions during pumping through pipes
Physical heat data of yeast products
Surface charge
Osmotic pressure
Sedimentation velocity of yeast
Example of how to calculate the influence of the solid volume share of the crop yeast on the attainable yield of barm-beer

The structure of the yeast cell and the functions of its organelles

The cytoplasm (cell plasma)
Cell wall and plasmatic membrane
The cell nucleus
Mitochondria
Vacuoles
Endoplasmic membranes
Ribosomes
Storage components of the cell
The mechanics of material transport across the yeast cell wall

Foundations of the yeast multiplication and its kinetics

Vegetative and sexual multiplication
Deoxyribonucleic acids and ribonucleic acids-carriers of the genetic code of the yeast cell
The growth curve of yeast populations in a batch culture and the cell cycle in the vegetative reproduction of a single cell
Multiplication kinetics of yeast
Factors influencing the speed of the yeast multiplication and standard figures of the generation time during the logarithmic growth phase
Designing a yeast propagation plant with the indicated figures and equations: calculation examples

Metabolic pathways and regulatory mechanisms of yeast

Energetic and anabolic metabolism
Metabolic pathways of the yeast cell
Regulatory mechanisms of the yeast metabolism
Fermentation by-products in yeast metabolism

The nutrients required by Saccharomyces cerevisiae for its multiplication

Required carbon and energy sources
Orderly manner of sugar utilisation
Crabtree-effect, aerobic fermentation and their influence on the yield of yeast
Required assimilable nitrogen
The free ?-amino nitrogen content (FAN) and its control
Advantages of using mixtures of amino acids instead of inorganic ammonium ions as sources of assimilable N for the yeast
Dosage of the N source and crude protein content (CP) of the crop yeast
The demand for minerals
The demand for growth promoting substances and of vitamins
Calculation of the yeast reproduction attainable with normal 12 °P beer worts, without addition of nutrients
Requirements on the wort used to multiplication of yeast
How yeast multiplication influences extract losses
Improving the nutrient supply by additions

Oxygen supply to the yeast: technological basics

Preliminary remarks
Concerning some biochemical interrelations from the point of view of the oxygen requirement
The state of our knowledge of the O2 supply required for brewing yeast multiplication
Oxygen demand and oxygen uptake rate of Saccharomyces cerevisiae at higher sugar concentrations
Calculation of the amounts of oxygen and air required for yeast multiplication (yeast propagation, pure culture) in beer wort

Machinery, equipment and plants for yeast pure culture and propagation

Yeast pure culture and propagation as a process
Equipment for the pure yeast culture in the lab
Equipment for the multiplication of the yeast at plant scale

General considerations
Example of a yeast propagation plant
Propagation tanks
Sensors for yeast propagation plants
Devices to inject oxygen
Wort sterilisation
Accessories
Examples of realised plants

Process fundamentals concerning the supply of oxygen to yeast

Laws governing the solubility of gases into liquids
Factor influencing the gas dissolution
Technical solutions for the aeration

Requirements to be met by the equipment

Materials and surfaces
Requirements for pipes and equipment to be operated aseptically
Suggestions for pipeline connections, for the installation of fittings and for the drawing of samples
Fittings for drawing samples
Suggestions for the use of pumps

Wort sterilisation
Plant design
Cleaning, disinfection, sterilisation

CIP-procedure
Sterilisation by steam

Measuring and control technique for yeast propagation plants

Measuring technique
Control technique

Yeast management in the brewery

General remarks and basic concepts
Pure culture and propagation of brewery yeasts

The isolation of brewing yeast strains
How to select a new yeast strain
Propagation of pure culture yeasts in the brewery laboratory
The handling and storage of yeast strain cultures in the lab
The propagation of pure culture yeasts in the brewery

Control methods for dosing the pitching yeast and for determining the yeast concentration

Determination of the yeast cell concentration with laboratory methods
The dosage of the pitching yeast and its control methods

Pitching

The amount of the yeast addition
The addition of yeast: when and how
Technology of yeast addition
The pitching temperature
The duration of pitching and the aeration of wort
Pitching with pure culture or propagation yeast

Steering fermentation

Temperature control
The influence of pressure
Technological measures to influence the ratio between residual fermentable extract and concentration of yeast in suspension
Influence of the agitation of the fermenting substrate
Acceleration of the yeast clarification

Cropping the yeast

The classic yeast crop
Yeast crop from a cylindroconical fermentation tank
The yeast crop by green beer centrifugation

Yeast management

Cooling the yeast
Sieving the yeast
Rousing the yeast
The modern way of rousing: “vitalisation”
Washing the yeast

Storing the yeast
Pressed yeast
Dry yeast

Recovery of barm beer and alternatives of utilization of barm beer and surplus yeast

The recovery of barm beer
Sedimentation
Separation

Barm beer recovery with self-emptying disc separators
Barm beer recovery with a decanter
Clarification separators installed before the filtration
Transport of the yeast after its separation with a separator or a decanter
The use of green beer centrifuges

Yeast press
Membrane separation processes

Crossflow microfiltration
Beer recovery according to Alfa Laval

Evaluation of the alternatives
Quality of barm beer and its processing
Utilisation of surplus yeast

Brewing yeast as fodder
Addition of brewing yeast to the mash
Brewing yeast fractions as pharmaceutical products and food additives
Yeast extracts
Storage of surplus yeast

Surplus yeast and waste water load

Index

Bibliography and sources