El por qué de sabores y olores indeseados

Por Juan Luis Peralta

Acidez, malos olores y turbiedad, elementos comunes que podemos identificar en una cerveza contaminada. Asociada principalmente a malas prácticas de elaboración, es un problema que no sólo afecta a los productores caseros, sino que también podría llegar a afectar a grandes cervecerías.

¿Cuántas veces hemos abierto una botella de cerveza en nuestras casas, locales o inclusive compradas en supermercados y nos hemos encontrado con que su sabor difiere mucho de lo que acostumbramos a encontrar en determinada marca o estilo?.  Cuando esto ocurre, más allá de la interpretación poco objetiva que pueda hacer un consumidor con paladar no entrenado, se puede deber a un clásico caso de contaminación o infección de la cerveza.¿Pero qué es una cerveza contaminada?, Paulina Cid, Tecnóloga en Alimentos y productora de cerveza casera afirma que esta denominación se utiliza para “describir las características indeseables que presenta ocasionalmente esta bebida como resultado principalmente de la presencia o acción de microorganismos como bacterias o inclusive levaduras salvajes, que son tan deseadas en las cervezas del tipo Lambic”.

En esa línea, Denise Baxter y Paul Hughes en su libro “Cerveza, Calidad, Higiene y Características Nutricionales”, añaden que la presencia de contaminantes “no sólo compromete el flavor de la cerveza, sino que también genera turbidez a medida que aumenta el número de bacterias”.

Contamination in beer

The reason behind unwanted flavors and odors

By Juan Luis Peralta

Acidity, foul odor and cloudiness are all common elements that can be identified in contaminated beer. Mainly associated to poor manufacturing practices, this is a problem which not only affects home producers, but that could also affect large breweries.

How many times have we opened a bottle of beer in our homes, pubs, or even ones purchased in supermarkets and have found that it tastes very different from what we are used to finding in a particular brand or style? When this occurs, apart from the subjective interpretation that a consumer with an untrained palate can make, it may be caused by a classic case of beer contamination or infection.
But what is contaminated beer? Paulina Cid, Food Technologist and home brewer says that this concept is used to “describe the undesirable characteristics that this beverage occasionally presents as a result mainly of the presence or action of microorganisms such as bacteria or even wild yeasts which are not so desired in Lambic type beers”.

Along these same lines, Denise Baxter and Paul Hughes in their book “Beer: Quality, Safety and Nutritional Aspects”, add that the presence of contaminants “not only compromises the flavor of the beer, but also generates cloudiness as the number of bacteria increases”.

Types of contamination

In either large or small scale production, all brewing processes can be prone to contaminating elements, whether physical (branches, rocks, insects, cardboard, among others), chemical (elements used in the cleaning of equipment) or microbiological, such as bacterial contamination which can cause great damage to production.
“While in some foods like yogurt or vinegar, bacteria may be beneficial, they can be a real problem in the manufacture of beer”, Paulina says. She adds that “thanks to the PH, the alcohol content and hops’ bactericidal effect, beer is resistant to most bacteria, however, there are a number of them which, likewise, affect the final product’s quality”.
The main bacteria that can alter the quality of the beer can be described as lactic, acetic or coliform.
Responsible for the highest economic losses and the most feared in breweries are the lactic, which generate excessive acidity, increased cloudiness and diacetyl aroma (rancid). Some, such as lactobacillus pastorianus, can also – excessively – generate lactic acid, alcohol and carbon dioxide (excessive carbonation). Streptococcus, which generate disorders in acidity, cloudiness and viscosity also exist.

Acetic bacteria are insensitive to hops’ acids; some of its common effects can be the generation of large amounts of acetic acid, carbon dioxide, as well as tastes and odors similar to vinegar, rotten apples or carrots.

Coliforms mainly present aromas of celery, cabbage or cooked vegetables.

On the other hand, wild yeasts “are those which ferment spontaneously and may appear due to inadequate hygiene conditions or yeast storage. It is hard to have control over them, as air is their means of transport and must is their breeding ground. The effects of wild yeasts are associated to beer cloudiness, increase in alcohol, carbon dioxide (gas) and the presence of strange flavors. However, there are many other microorganisms that can affect beer when necessary hygiene and safety measures are not complied with”, Paulina concludes.

Avoiding contamination
According to Wolfgang Vogel, in his book “Beer from your own brewery“: “the best procedure to prevent infection is to maintain thorough cleanliness in all premises where beer is made. Particularly, grounds where beer is cooled or where main fermentation occurs, may not be sufficiently sanitized, therefore they must be thoroughly and often cleaned.”
Hence, it is important that producers prevent this type of situations. Besides cleaning, the expert suggests some recommendations:
- A high acidity level, since acid has a preservative effect.
- The addition of abundant hops, as bitter substances protect against infection.
- A high degree of fermentation, partly due to the fact that unfermented sugars allow for the spread of contaminants and the high alcohol rate exerts a protective effect.
- Bottling avoiding loss of carbonic acid, a potent protector against infection.
- Bottling avoiding contact with air, since microorganisms need more or less oxygen to multiply.
Currently, there are standards that aim at contributing to reduce to the minimum the possibility of contamination; however, this is always a possibility when producers do not pay close attention to the process’ critical stages.
Thus, it is always important for consumers to assume a leading role and carefully evaluate the beer they consume analyzing the product’s flavors, cloudiness and odor.
In turn, producers have the greatest responsibility: “it is important for the artisanal industry to establish greater standardization and more control over the critical variables of its processes. Nowadays, Quality Assurance Systems exist which avoid or minimize all types of contamination”, Paulina Cid says.

Una Respuesta a “Contaminación en la cerveza (Edición 7, marzo – junio 2012)”

  1. gerardo ruiz says:

    seria interesante que tradujeran el articulo completo al español…

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