Sensory Analysis of Beer

Gayatri Mehta, Jakob Frenzel & Patricia Diniz Fischer

Research Institute of Beer & Beverage Analysis

“It’s my beer, it suits my pallet, I like it, it sells, is that not all that matters?” This thought process changed in the early 1900’s. It became the industry norm to achieve a certain quality and consistency with regards to their sensory properties. Sensory analysis for a long time was not given its due recognition. The interplay of the olfactory, gustatory, and visual sensory influences encompasses a wealth of useful technical information. These sensory factors are also a major driving force in the potential success or failure of a product on the market. Rather aptly put by Randy Mosher author of Tasting Beer: An Insider’s Guide to the World’s Greatest Drink “Much like any aspect of a consciously lived life, enjoying beer to the fullest takes education, experience and a proper frame of mind”.

The brewing of beer in its most simplistic form represents one of mankind’s oldest uses of biotechnology. Whether the discovery of the pleasant beverage can be ascribed to the accidental contamination of grains or the natural curiosity of humans remains a mystery. It is one of the most enjoyable beverages in the world. The taste and aroma of this product is the result of the interaction and sum of several hundred flavour active compounds some of which originate in the raw materials used in production, but which are mostly the result of the products fermentation. All these flavour active components must be kept in a certain balance or a single compound might dominate the sensory experience and destroy this flavour balance. Thus, the objective evaluation of beer’s sensory attributes is a skill that many breweries cannot afford to be without.

Sensory evaluation is defined as a scientific method used to evoke, measure, analyse and interpret those responses to products perceived through senses of sight, smell, touch, taste and hearing. Sensory tests have been conducted for as long as there have been human beings evaluating food, water and goods for consumption. The rise in trade inspired a more formal sensory testing. This, in turn, resulted in prices based on the quality of the goods. This grading of good based on quality resulted in professional tasters and consultants for the food beverage and cosmetic industries in the early 1900’s which set the stage for sensory analysis as we know it today. Over the years these methods were refined formalized, structured and codified into the sensory methodology of today’s time. However sensory analysis still had a major drawback, its measurements are performed by human beings and we are fallible. Thus, the next big leap in the sensory analysis was seen when multivariate statistics were used to analyse the data collected. Suddenly all this data was now statistically significant.

Sensory analysis can provide a qualitative measurement (is beer A sweeter than beer B) as well as a quantitative measurement (on a scale of 1 to 5, beer A is a 4 while beer B is 2 with regards to sweetness). This measurement could be made by trained personnel (a sensory panel) or by consumers, depending on the aim of the study. The aim of the study can further be divided into objective analytical quantity such as flavour intensity or a subjective value such as preference. This basic principle along with asking the right question to the correct sample group at the right time allows breweries to make key decisions about their products and the responses of their consumers to their product.

Sensory analysis can provide a qualitative measurement (is beer A sweeter than beer B) as well as a quantitative measurement. The aim of the study can further be divided into objective analytical quantity such as flavour intensity or a subjective value such as preference. This basic principle along with asking the right question to the correct sample group at the right time allows breweries to make key decisions about their products and the responses of their consumers to their product.

Sensory analysis answers questions in relation to quality under three main headings: discrimination, description and preference. While the scope of this article does not allow for an in-depth look at each of these headings a short overview is presented below.

Discrimination:

Even though the word in carries a negative connotation, it means to recognize and understand the difference between one thing and the other. To glean a better understanding let us take the following example. A brewery has a flagship hefeweizen however, they have decided to use a new yeast supplier due to monetary reasons. They could use discrimination analysis to pose and answer the following questions. Is the new hefeweizen different from the old one? Would people notice the difference?

Description:

By dictionary definition, means discourse intended to give a mental image of something experienced. Using the same example as above the following questions can be asked and answered inferred. How does the change in yeast supplier affect the sensory quality of the beer (are their more fermentation byproducts or less, does the body of the beer remain the same)? Or simply what does the new beer taste like?

Preference:

By dictionary definition, means the act, fact, or principle of giving advantages to some over others. Using the same example as above the following questions can be asked to assess the beer. Is the new beer acceptable? Is it as good as the older one? Is this beer preferred?

What can sensory analysis tell us?

The complex mixture of volatile compounds varying in chemical structures and concentration levels generates the beer aroma which has a key role in beer quality. With the help of a trained panel sensory analysis allows a brewery to produce a sensory fingerprint of their product. In order to generate this fingerprint, a number of descriptors which the brewery deems as the most relevant attributes are selected for sensory evaluation (Figure 1). These fingerprints can be a versatile tool. The fingerprint allows brewers to detect changes over time in the sensory profile and thus prevents flavour shifts over time, allowing the brewery to maintain consistency. They can also be used when a new product is being developed allowing brewers to track the changes made. This sort of analysis has been adopted by malt supplier such as Weyermann and yeast supplies such as Fermentis to help the brewer make more informed decisions regarding the raw materials used.

Figure 1: Descriptive sensory profile of fresh beer production over time

The sensory analysis allows brews to monitor the sensory quality of their product thereby allowing brewers to make key decisions about the quality of the product. The event the beer falls below the set standard, the product can be rejected or rectified.

By establishing a certain quality standard, it allows customers to build a preference and thus, in turn, a brand loyalty. In the past beers had been known to have flavours known as “house flavour”. These were several flavour defects that were tolerated by the consumer. Today’s consumers are more demanding than ever with regards to the quality of the product. Information about the product is available at the touch of a button. Due to the number of choices consumers have the assurance that the product delivers to the expectation of the consumer is one of paramount importance. So much so that attitude and beliefs about a product influence consumer preference and the closely related concept of purchase intent, as concluded in a study conducted by Smythe et al. The researchers tested how consumers form three different countries respond to beers with supposedly different reported history. It was found the less trained panel assigned a preference based on this reported history, while the more trained panel did not.

It has become imperative for breweries to maintain clean beers i.e. must not have process flaws and must also be true to style. A good example is Diacetyl (2,3-butanedione) which has a butterscotch flavour which is the result of an improper fermentation management. It is a process flaw in a German pilsner, however, a desirable flavour in a bohemian pilsner. These off-flavours can arise not just form the brewing process but also form raw material, such as dimethyl sulphide (DMS) which originates from the malt with a high level of the precursor S-methylmethionine (SMM), or as a result of microbial contamination. With help of sensory analysis process control problems can be identified and rectified. As beer ages, its sensory characteristics deteriorate and off-flavours such as Trans-2-nonenal (which has a papery, cardboard flavour) can be detected in beer that is stored improperly.

Flavour threshold of these off-flavours vary based on the taster ability to detect the substance. Some of the factors that affect a taster’s ability to identify the off-flavour are geographical background, ethnicity and diet. However, constant training ensures that these biases are limited. The basis of an effective sensory regimen is well-trained staff, which is able to detect changes and potential problems throughout the production process and the shelf-life of a product.

The VLB offers a course called “VLB Beer Taster Certification Program”, a seminar that prepares the attendee to sit for the VLB taster’s exam and become officially certified for the ability to detect characteristics and off-flavours in beer and get a better understanding of beer styles. The course is three days long and takes place in Berlin. It also covers different sensory testing schemas and how they can be effectively applied to address various quality questions or uncover potential problems. A final session will present a short sensory excursion into the ever-popular world of craft beer. This course is designed for those who deal with sensory evaluation as a part of their normal responsibilities. The same course can be provided on site in any country as well. Sensory analysis is also part of the syllabus in some of the other courses the VLB has to offer, such as in the Certified Brewmasters Course, as well as Craft Brewing in Practice.

The role of sensory analysis does not solely begin at the end of the product alone. For example, Sierra Nevada brewery in Chico, California, taste and smell-test the water daily, using a minimum of four people, at six different points in the brewing process.  The water is tasted for anything unexpected that might make its way into the final product. They also test non-product process water such as water used for the boiler or any off flavours to ensure proper functioning of the system.

Sensory analysis can also be used to allow brewers to correct recipes for seasonal variation in raw materials. Discriminatory sensory analysis can assess in what way a new raw material supplier will impact the final product early on thus resulting in consistent quality all year round.

When a new product is developed or a recipe is changed sensory analysis tracks that change and allows for key decisions such as preference. Sensory analysis can also be used by a company to understand what the market preferences are. This kind of analysis is not carried out by a trained panel but consumers. This can help breweries to make an economic decision about their product. In addition to single evaluation of a product, the VLB offers periodic final product quality control in the following models

Brand Consistency Control:

To detect unwanted oscillations of the product between different batches (Figure 2). This analysis can be carried out periodically from one brewery, or as a simultaneous comparison between different production sites.

Figure 2: Descriptive sensory profile of fresh beer production over time.

Brand Staling Control:

Here the aim is not only to detect consistency in the fresh sample, but also to determine the rate at which the product becomes stale. This method can also give an indication of the impact of any modifications to the production materials/process on shelf-life. In this evaluation, a combination of sensory analysis along with laboratory analysis can be used. The following case study serves as example:

The sensory profiles of an unpasteurized (craft) and pasteurized (industrial) India Pale Ales (IPA) were studied over a period of time. (ART represents unpasteurized beer, while IND represents pasteurized beer, 0 is fresh beer while 4 is the oldest sample). The principal component analysis (PCA) shows a clear distinction between the two types of production process (second component). In the first component, there is a clear association of positive sensory attributes with younger samples (on the left of the diagram) and negative attributes with the older samples (right side of the diagram).

Another application of the same method is the study of shelf – life. In warm countries such as India, maintaining the shelf-life of a beer is a challenge. A number of factors result in oxidation flavours in the beer.

Figure 3: Sensory profiles of unpasteurized and pasteurized IPAs

At the VLB we carry out (on a regular basis) long-term studies during which beers are either naturally or force-aged and a descriptive sensory analysis is performed to compare aged and fresh beer. Samples are analysed over a prolonged period of time to determine their turning point, the point at which their quality is no longer acceptable. Thereby allowing the brewery to set a quality standard and set a more defined shelf-life to their product.

Comparative Brand Characterisation:

With the help of descriptive analysis our tasters generate a fingerprinting of the product that aids in building a profile for the brand. This fingerprint can then be used to compare with the brand’s competitors. It can also be used to develop recipes as well as the reformulation of a product.

Let us look at the following case study. More than 300 German beers were rated by intensity (1-5;1 being lowest,5 being the highest) for the following attributes bitterness, hop aroma, palate fullness, fruitiness, and maltiness (Figure 4). Following which the style ranges for each style of beer was added as a category (Figure 5). Based on these five attributes it was possible to identify the same style of beer in the cluster. The same way of presenting results is can be used for brand characterization. Through these maps it is possible to conclude if a certain beer passed or failed its sensory evaluation based on style.

Figure 4: Sensory attributes of over 300 German beers

 

Figure 5 Beer styles based on sensory attributes

Current research in the field is focused on the development of the electronic nose. The applications for which can range from authentication of a beverage to denoting its sensory attributes. There has been some progress in this direction; however, it will be a long time before the electronic nose makes a sensory panel redundant. Until then, sensory analysis will remain an important quality control parameter that can provide a wealth of technical data that can be the driving force to the success or failure of a product.