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This is the complete lecture note for BST511 Quality Control II. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • Course code: BST511 • Course title: Quality Control II • Course credit load: 3 Series 1: Microbial Contamination in Breweries Series outline • Part 1: Sources and Incidence of Microbial Contamination o Sub-Part 1.1: Raw materials contamination o Sub-Part 1.2: Wort fermentation and conditioning contamination o Sub-Part 1.3: Dispensing contamination • Part 2: Types of Microorganisms in Breweries o Sub-Part 2.1: Bacteria o Sub-Part 2.2: Yeasts o Sub-Part 2.3: Moulds • Part 3: Influence of Microbial Contamination on Brewing Processes o Sub-Part 3.1: Effects on raw materials o Sub-Part 3.2: Effects on fermentation and flavour o Sub-Part 3.3: Effects on product stability • Part 4: Non-Microbial Contamination in Breweries o Sub-Part 4.1: Physical contamination o Sub-Part 4.2: Chemical contamination • Part 5: Practices for Minimisation of Microbial and Oxidative Spoilage o Sub-Part 5.1: Preventive measures during brewing o Sub-Part 5.2: Monitoring and corrective actions Introduction
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Brewing is a delicate process that combines science and craftsmanship, yet it is constantly threatened by the presence of unwanted microorganisms. These contaminants, if not properly controlled, can compromise the flavour, stability, and safety of beer. For anyone involved in brewery operations, understanding microbial contamination is essential, as it forms the foundation of quality control and ensures that consumers receive a product that is both enjoyable and safe. The aim of this Series is to equip you with the knowledge and skills to recognise, analyse, and manage microbial contamination in breweries, thereby supporting the production of high-quality brews. We shall commence this Series by examining the sources and incidence of microbial contamination in breweries. Next, we will explore the different types of microorganisms, including bacteria, yeasts, and moulds, that affect brewing processes. Following that, we will analyse how microbial contamination influences raw materials, fermentation, flavour, and product stability. Moving on, we will consider non-microbial contamination such as physical and chemical hazards. Finally, we will conclude by discussing practices for minimisation of microbial and oxidative spoilage, ensuring that you are well prepared to apply preventive and corrective measures in real brewery settings. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define the sources and incidence of microbial contamination in breweries, • SLO 1.2 classify the types of microorganisms that affect brewing processes, • SLO 1.3 analyse the influence of microbial contamination on raw materials, fermentation, flavour, and product stability, • SLO 1.4 explain the nature of non-microbial contamination in breweries, and • SLO 1.5 evaluate practices for minimisation of microbial and oxidative spoilage in brewery operations. 1.1 Sources And Incidence Of Microbial Contamination 1.1.1 Raw materials contamination Brewing begins with raw materials such as malt, hops, and water, all of which can serve as entry points for microorganisms. Microbial contamination refers to the presence of unwanted bacteria, yeasts, or moulds that interfere with brewing processes. These organisms may originate from soil, storage facilities, or handling practices. For example, malt stored in damp conditions can harbour mould spores that later affect beer flavour and stability. Fill in the blank: Malt stored in ______ conditions can harbour mould spores that later affect beer flavour and stability.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Diagram showing pathways of microbial contamination in raw materials. Caption: Figure 1.1 Pathways of microbial contamination in brewery raw materials. 1.1.2 Wort fermentation and conditioning contamination During fermentation, yeast is deliberately added to convert sugars into alcohol. However, unwanted microorganisms can also thrive in this nutrient-rich environment. Wort is the sweet liquid extracted from malt, and it is highly susceptible to contamination if sanitation is poor. Contaminants may cause off-flavours, reduced alcohol yield, or spoilage. Conditioning tanks, if not properly cleaned, can also harbour residual bacteria that compromise product quality. Fill in the blank: ______ is the sweet liquid extracted from malt that is highly susceptible to contamination if sanitation is poor.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Image showing fermentation tanks in a brewery. Caption: Plate 1.2 Fermentation tanks as potential sites of microbial contamination. 1.1.3 Dispensing contamination Even after brewing and packaging, contamination can occur during dispensing. Dispensing contamination refers to microbial growth in beer lines, taps, or storage vessels used in pubs and restaurants. If cleaning schedules are irregular, biofilms of bacteria and yeasts can develop, leading to sour or stale flavours in beer served to customers. This stage highlights the importance of hygiene beyond the brewery itself. Fill in the blank: Irregular cleaning schedules in beer lines and taps can lead to the formation of ______ that spoil beer flavour. Box 1.1: Common sources of dispensing contamination • Beer lines not cleaned regularly • Taps exposed to air and moisture • Storage vessels with residual beer Pilot questions 1.1 1. Which raw material is most likely to harbour mould spores if stored in damp conditions? 2. What is the sweet liquid extracted from malt that is highly susceptible to contamination? 3. Name one effect of microbial contamination during fermentation.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 4. What term describes microbial growth in beer lines and taps? 5. Why is sanitation important during conditioning? 1.2 Types Of Microorganisms In Breweries 1.2.1 Bacteria Bacteria are single-celled microorganisms that can multiply rapidly under favourable conditions. In breweries, they are often introduced through contaminated raw materials, water, or poor sanitation practices. Some bacteria produce lactic acid, leading to sour flavours, while others generate unwanted compounds that spoil beer aroma and stability. Common bacterial contaminants include Lactobacillus and Pediococcus. Fill in the blank: Common bacterial contaminants in breweries include ______ and ______. Diagram showing bacterial contamination pathways in breweries. Caption: Figure 1.3 Bacterial contamination pathways in brewing processes. 1.2.2 Yeasts Yeasts are fungi that play a central role in brewing by fermenting sugars into alcohol and carbon dioxide. However, not all yeasts are beneficial. Wild yeasts are unwanted strains that can cause off-flavours, poor fermentation, and instability. Some yeasts may also mutate into respiratory-deficient mutants, which fail to ferment properly and reduce beer quality. Fill in the blank: ______ are unwanted yeast strains that cause off-flavours and instability in beer.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Image showing yeast cells under a microscope. Caption: Plate 1.4 Yeast cells observed under a microscope. 1.2.3 Moulds Moulds are multicellular fungi that grow as filaments and produce spores. In breweries, mould contamination often arises from damp storage conditions or poorly maintained equipment. Moulds can impart musty flavours and compromise product safety. Their spores are resilient, making them difficult to eliminate once established. Preventing mould growth requires strict control of humidity and regular cleaning of storage areas. Fill in the blank: Preventing mould growth requires strict control of ______ and regular cleaning of storage areas. Box 1.2: Key characteristics of mould contamination • Growth in damp conditions • Production of resilient spores • Contribution to musty flavours Pilot questions 1.2 1. Name two common bacterial contaminants in breweries. 2. What type of yeast strains are considered unwanted in brewing? 3. What are respiratory-deficient mutants, and why are they problematic?
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 4. How do moulds typically enter brewery environments? 5. Which environmental factor must be controlled to prevent mould growth? 1.3 Influence Of Microbial Contamination On Brewing Processes 1.3.1 Effects on raw materials Microorganisms can alter the quality of raw materials before brewing even begins. Raw materials such as malt and hops may lose their desirable properties if contaminated. For instance, mould growth on malt can reduce starch content, while bacterial contamination in water can introduce off-flavours. These changes compromise the efficiency of brewing and the consistency of beer quality. Fill in the blank: Mould growth on ______ can reduce starch content and compromise brewing efficiency. Diagram showing microbial effects on malt, hops, and water. Caption: Figure 1.5 Microbial effects on brewery raw materials. 1.3.2 Effects on fermentation and flavour Fermentation is the stage where yeast converts sugars into alcohol and carbon dioxide. However, contamination by bacteria or wild yeasts can disrupt this process. Fermentation contamination refers to the presence of unwanted microorganisms that compete with brewing yeast. This may result in sour flavours, reduced alcohol yield, or undesirable aromas. The flavour profile of beer is highly sensitive, so even minor contamination can lead to rejection by consumers.
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