Lesson 9 - Yeast Management SAQ

1.         *What is the difference between viability and vitality testing when applied to yeast? What is the value of a vitality test over a simple measure of viability?

2.         * Answer both parts of this question.       

a)     Draw a diagram showing a vessel suitable for storing pitching yeast cropped from the base of a cylindroconical fermenter. Describe the key features of the vessel.

b)      How might you change the storage method if your brewery introduced very high gravity brewing?

3.         **A yeast handling plant requires extensive cleaning, using various detergents and sanitisers. It also requires a CIP plant to ensure the yeast vessels and pipework remain clean to prevent the contamination of the brewery culture yeast. Do you think that if all the yeast is disinfected with acid prior to pitching, it is possible to save money by reducing the frequency and rigour of cleaning regimes of brewery yeast handling plant?

4.         ** Your brewery is upgrading its fermentation facilities. Currently, you use top-cropping open square fermenters, but these are old and are suspected of being a major cause of recent microbiological spoilage problems. It has been decided to replace these with fewer and bigger cylindroconical vessels. At the same time, it has been decided to introduce high gravity brewing. You have been asked to write a report which highlights the potential gains of this plan but also to identify potential problems. In addition, you have been asked to indicate the what the likely impact on the current yeast handing system will be. What would your report contain?

5. **Answer all three parts of this question.

a)    With the aid of a suitable diagram, describe the elements of a system suitable for the automatic control of yeast pitching using a sensor which utilises the dielectric properties of cells.

b)    Describe how the sensor works?

c)    What are the advantages and disadvantages of this automatic system?