aids, particularly fining agents, contain milk or egg products, which are allergens. For wines marketed in the EU, allergen labelling was made compulsory from 25 November 2005 under a European Commission Directive. Initially only the presence of sulfites/sulfur dioxide had to be declared on the label, for concentrations at or exceeding 10 mg/l. This threshold remains applicable. Most wines will contain in excess of this figure even if no SO2 is added during the production process. In 2007 European Directive EC 2007/68 was issued, which provided for the mandatory labelling of further allergens – this directive has since been incorporated into EU Regulation No. 1169/2011 [9]. Due to objections from the wine industry this did not generally come into force until 2012. Insofar as wine is concerned, the only further allergens to be declared on the label are milk or egg products, if the concentration of either exceeds 0.25 mg/l. The current EU wine labelling regulations (EC) No: 2019/33 state the wording and form of allergen labelling information [10]. Wine marketed in the European Union remains exempt from the compulsory ingredients listing that was introduced for food products in 2011: EU Regulation No.: 1169/2011 [9].
1.6 Faults and Taints
Generally in the food and drink industries, a distinction is conventionally made between the terms ‘fault’ and ‘taint’. A taint may be defined as an ‘unwanted and unacceptable odour or flavour; a contaminant derived from an external source including the environment and packaging’. Equipment used in wine production processes, additives, and processing aids (e.g. bentonite), the winery atmosphere, transport containers, and packing materials including cork bottle closures can be sources of taints. Rather simplistically, the ISO defines a taint as a ‘taste or odour foreign to the product originating from external contamination’ [11]. Conversely, a fault may be considered to be an internal chemically or microbiologically produced off‐odour, off‐flavour, or cause of product deterioration. Oxidation and the off‐flavours from fermentative sulfur compounds are examples of faults. Biological and enzymatic degradation of compounds such as fatty acids frequently result in off‐flavours. Whilst faults may be due to poor or careless winemaking, care and diligence throughout the production, and packaging processes are also necessary to minimise the risk of taints.
However, the technical distinction between ‘faults’ and a ‘taints’ is not always clear, and restricting the use of the words in a such narrow manner makes little sense. For example, so‐called ‘smoke taint’ affects grapes, being adsorbed onto the skin of berries and translocated to grapes via leaves. However, it is the compounds that are created (metabolised) during winemaking that give smoke‐taint associated off‐odours and flavours. The so‐called ‘rogue’ yeast Brettanomyces produces compounds that may give off‐odours and flavours, and the words contaminant and taint are often used in this regard. For example Manuel Malfeito‐Ferreira talks of the ‘horse sweat’ taint when reviewing the impact of Brettanomyces [12]. In a restaurant, the diner rejecting a wine that exudes the damp, musty odours of the TCA compound, always derived from an external source such as a cork closure or even the cellar atmosphere, will inform the sommelier or waiter that it is faulty (or corked), and is most unlikely to use the descriptor ‘tainted’. In fact, at low levels, TCA compounds will not actually taint a wine, but will strip it of fruitiness and result in tasting very flat. Accordingly, a wine contaminated with TCA, other than at miniscule levels of concentration, will not always be tainted, but will always be faulty. Further, many researchers use the word ‘taint’ in papers when discussing what are technically faults, as do many professional wine writers and authors. David Bird MW, speaks of ‘reductive taint’ in his book Understanding Wine Technology (3rd Edition), which is used by many wine students worldwide studying for the internationally recognised Diploma examination of the Wine and Spirit Education Trust [5]. Dr Eric Wilkes of the Australian Wine Research Institute (AWRI) refers to reduced aromas, oxidation, and Brettanomyces as taints [13]. Accordingly, I consider that the word ‘fault’ should be regarded as an all‐encompassing descriptor for something that is wrong with a wine (to include any taint or other contamination) that results in a significant off‐odour or flavour, a marked reduction of quality, or is adverse to human health. For the sake of both clarity and simplicity, it is generally used as such in this book.
1.7 Distinguishing Between Faults and Flaws
In a tasting assessment, the condition of a wine may be described as
Fault‐free (sound);
Flawed (showing minor defects);
Faulty (showing one or more serious defects).
As stated, the use of the word ‘fault’ should be reserved for major defects, including those off‐odours and off‐flavours that have a significant organoleptic impact upon a wine, or for compounds that may cause accelerated deterioration, or are harmful to human health. Where the impact is minor, including defects that result in a reduction of typicality (the word tipicité is often used amongst wine lovers and critics), or a modest reduction in quality or ageing potential the term ‘flaw’ is generally more appropriate, although some authors do regard a lack of typicality of style as a fault [14]. The level, or concentration, of causal compounds is obviously key here, but whilst the physical level is generally relatively easy to quantify by laboratory analysis, the sensory impact upon wines of differing styles and aroma and flavour matrices may be less easy to qualify: much will depend upon the style and matrix of the wine. So the boundaries between faulty, flawed, and ‘in good condition’ may, on occasions, be somewhat blurred. However, there are some compounds which, even if present at a low level, cause a such a reduction in organoleptic attributes and a loss in quality, that affected wines must always be regarded a faulty. TCA and other haloanisoles (see Chapter 3) are classic examples.
Whilst there is little doubt that a wine contaminated from an external source should always be regarded as faulty, the internally produced ‘off’‐aromas and flavours may be subject to dissent as to the concentration at which they become unacceptable and are considered to be flaws or faults. When tasting a wine, the judgments made are, to a large degree, subjective. Individuals have varying sensitivities, responses and reactions to aromas, odours and flavour compounds based on their culture and education [15], experience, and age [14]. Members of a panel of professional tasters and critics may be unanimous in their judgements when assessing a wine or there may, on occasions, be out and out dissent. There can also be disagreement between professionals and consumers as to what constitutes a fault or flaw, for example, the acceptability or otherwise of sediments. Precipitated crystals of potassium bi‐tartrate or calcium tartrate are sometimes found in the bottom of wine bottles and, of course, these will often appear in glasses of wines when poured. They are most likely in high acidity wines from cool climates, but can appear in reds too. The crystals are harmless and have no negative organoleptic impact, but to the consumer they may be cause for concern and even rejection of the bottles in question. Accordingly, although many industry professionals are unconcerned by tartrates, some do consider them to be an ‘appearance’ fault (see Chapter 15).
1.8 Sensory Detection (Perception) Thresholds and Sensory Recognition Thresholds
1.8.1 Sensory Detection Thresholds
There are many compounds that may give rise to faults but, with the notable exception of TCA and other haloanisoles, their presence usually only becomes important when their concentration is at or above, or has the potential to reach, their individual sensory detection thresholds. To complicate matters, there are also some compounds which, even if below their individual sensory detection thresholds, may produce off‐odours or‐off‐tastes if present with other compounds, which may also be below their individual sensory detection thresholds.
Sensory perception thresholds may be divided into odour detection thresholds
