Lesson 6 - Beer Flavour and Stability
In this lesson we will discuss beer flavour and beer flavour stability. This will include the effects raw material has on beer flavour, followed by a discussion on common taints, their flavours and consumer reaction. We will examine the flavour changes that occur during beer storage: focussing on oxidation reactions, the species of oxygen involved, and how we can utilise antioxidants to protect against aged beer flavour change. Finally, we will summarise the selection of raw materials and process optimisations available to improve beer flavour stability.
Taints from Cleaning Materials
Included in this category are taints from caustic, acid and sanitisers. These different classes of cleaning agents produce diverse taints ranging from descriptions such as ‘alkaline’ or ‘soapy’, ‘acid’ or ‘sour’, and ‘medicinal’ or ‘disinfectant.’
Phenolics
Phenolic taints constitute some of the most flavour-active taints in beer. Chlorophenols are formed from the interaction of chlorine from water treatment or cleaning agents, and the phenols derived from water or brewing raw materials. They produce an unpleasant hospital or disinfectant flavour in beer, often accompanied by consumer rejection.
2-6-Dichlorophenol is a flavour standard described as ‘antiseptic mouthwash’.
Iodophors
Iodophors are made by mixing iodine with a solubilising agent.
These solutions were used as the active ingredient in sterilant baths as well as a sterilising agent for vessel CIP.
Iodophors are extremely flavour-active and give beer a metallic or inky taint.
Peracetic acid
Peracetic acid can oxidise components of beer and form the reactive hydroxyl radical, which catalyses oxidation reactions (we will cover this later in the lesson). It will spontaneously break down to water and oxygen.
Alkaline cleaning agents
Caustic soda, or sodium hydroxide, is a common cleaning agent across all parts of the brewery, used for the cleaning of vessels, pipework, packaging containers, and filling equipment. It is amongst the most common contaminants of beer; therefore, it is essential that it is checked at each stage of the brewing and packaging process.
Contamination produces soapy, alkaline, or detergent taints. They are often associated with an increase in beer colour and sodium ion concentrations in addition to an undesirable flavour change.
Acid cleaning agents
Contamination with cleaning acids and peracetic acid sanitiser produces acidity or sourness in beer – described as like lemon juice or vinegar. pH is reduced, and gross contamination results in consumer rejection.