Educational

The sensory analysis laboratory

Written by admin1 April 15, 2020 0 comment

The ideal operating conditions for the panel

Having a laboratory dedicated to sensory analysis, perhaps built ad hoc, is a luxury that only research centres and large companies can afford. Sensory labs can have different layouts, but most of the times they are divided in three large areas: one dedicated to the preparation/transformation of the samples, one for the analysis sessions, whether collective or in a cabin and one reserved for offices and services.

Most of the time, in a company environment, a sensory testing area is adapted in existing premises, maybe shared with other activities. This solution can act as a valid alternative provided that some fundamental requirements are met in order to guarantee that the testing sessions are carried out rigorously. Here we describe the most important ones.

Isolation from external factors: it is essential that judges concentrate on the sensory characteristics of the product without being distracted or influenced by the external environment. The noise of a bottling machine or the smell of milk that permeates the premises of a dairy factory can irreparably compromise the result of the analysis. It is a good idea to take all precautions so that the judge is not distracted by the presence of external sensory stimuli. This is why it is advisable to carry out the tests in rooms far from any production areas or sufficiently isolated from them, in which noises, smells or other stimuli are eliminated or mitigated to the maximum. In order to solve permanently the presence of unwanted odours, for example, the most advanced laboratories maintain a constant positive air pressure inside the rooms dedicated to the evaluation, so as to prevent the entry of odours (volatile molecules) from the adjacent rooms.

If a collective evaluation session is carried out and it is required for the judges to communicate with each other, they are generally seated at the same table. This is not the case of individual evaluations. Here, it is essential that the single judge is not influenced/disturbed by the evaluations of the other panellists. For this reason, it is necessary to provide additional isolation from the external environment. This is achieved through the sensory booths or cabins. Sensory booths are closed or semi-closed cubicles fitted with a desk, a chair, lights and other items designed to offer a neutral environment in which perform sensory analysis. The samples can be introduced in the booth through a sliding window in front of the desk, communicating with the kitchen or preparation space.  

Sensory booth can be expensive or there may not be a dedicated space available in the premises. In these cases, the use dividing panels that can be mounted on a table, or to arrange the judges in such a way as to reduce their interactions as much as possible.

Lighting: especially in cases where the visual characteristics of the products are taken into consideration, such as in the case of wines, the tests must be carried out under standard lighting conditions. It is therefore necessary to ensure that a constant condition of artificial lighting is maintained and that this is not modified by variations in the intensity of the natural light coming from the outside. In order to prevent this, the windows of the test room should be made light-tight with blinds, cardboard panels or heavy tents. 

Sensory cabins generally have their own lighting system, which is why it is important to avoid this being altered by other lighting sources. Similarly, special attention should be paid to lighting during collective assessments that are performed outside the sensory booths.

Air conditioning: the external temperature is an important factor during sensory evaluation, because it affects both the physical state of sample and the perception of the judge. Furthermore, a room temperature that is too warm or cold would prevent the judge from maintaining a comfortable physiological state and hinder his concentration. We must therefore maintain constant temperature conditions in the premises dedicated to the analysis and make sure that this is as homogeneous as possible in the room, for example by avoiding direct drafts of cold or warm air from the AC vents on the judges. In the same way, it is important to keep under control the temperature of the samples that require certain service conditions, such as cheeses or drinks. If thermostats are not available, it is recommended to prepare the samples just before the evaluation session and to consider the time necessary for them to acclimatise in the tasting room. It is however suggested to record the temperature of the sample and the room during each analytical session, and to make available this information during the processing of the results.

Area for sample preparation: this area is particularly important and should be separate from the testing area, especially in the case of products that require preparation, such as cooking meat or gutting fish, or in case of samples that are “intrusive” for the sense of smell such as some cheeses. In this way it is possible to carry out the preparation without “contaminating” the area dedicated to the evaluation and to keep up the standards of hygiene and food safety. It is important that this area is located nearby to the laboratories, so that the samples can quickly reach the evaluation area, but that it is also sufficiently isolated from it to prevent the presence of unwanted odours or stimuli.

For this reason, the preparation area is generally equipped with vents or extraction systems. In the best scenario, the preparation area is an equipped kitchen with stoves, fridges, working areas etc.)

Since most of the times several samples are submitted to the judges at once, each one in a special container and served according to a precise order, it is good to have large working surfaces in order to facilitate sample set up, service operations and to avoid errors. To highlight how much this can be critical, even in simple test designs let’s think of a triangle test. To carry out a triangle test with 30 judges, 90 samples in six different presentation combinations must be served. It is therefore essential to have a good organizational skills and the appropriate work premises to avoid errors that could compromise the analysis results.