Essential Requirements for Conducting Sensory Evaluation in Dairy

Sensory evaluation has long been the most direct way to assess whether a dairy product is truly good – before any laboratory instrument confirms it. A trained human nose can detect rancidity in butter. A practiced palate can identify subtle off-flavors in cheese that may signal a processing problem. But for this kind of evaluation to be reliable, it cannot be done casually. It requires a properly designed laboratory, a qualified panel of evaluators, representative samples, and a structured process. This post walks through the essential requirements for conducting sensory evaluation in dairy – what the environment must look like, who should be doing the evaluation, and how samples should be prepared and assessed.

Why structured sensory evaluation matters in dairy 🔗

Sensory evaluation is the oldest method of checking dairy product quality, using the five basic senses – sight, smell, touch, hearing, and taste – to assess product characteristics. It is used not only to verify the quality of finished products before they reach market, but also to monitor shelf life, evaluate raw materials, support new product development, and benchmark against competitors. Because human perception is the instrument, the conditions under which evaluation takes place have a direct impact on the accuracy and repeatability of results.

A successful sensory evaluation programme in dairy rests on three core pillars: proper laboratory facilities, a qualified sensory panel, and a rigorous training programme. Each component plays a role that cannot be compensated by the others.

The sensory evaluation laboratory: layout and rooms 🔗

The physical design of the sensory laboratory is the foundation of reliable evaluation. A well-designed sensory lab generally includes four core areas: a briefing room, testing booths, a preparation room, and an office for the sensory leader. The most critical design considerations are location, ventilation, lighting, traffic flow, sample preparation and presentation, evaluator communication, and overall comfort.

The briefing room 🔗

The briefing room is where all evaluators assemble before a session begins. Here, the panel leader explains the purpose of the evaluation, reviews the scorecard, and issues instructions for the session. It should be adjacent to the testing booths and offer comfortable seating. In smaller facilities, the briefing room can double as the panel leader’s office.

Testing booths 🔗

The testing area is where panel members carry out the actual evaluation. It is divided into individual booths – typically between 5 and 10 – so each evaluator works independently without being influenced by others. Each booth should be large enough to hold samples, utensils, a sink, rinsing agents, and a scorecard; a working area of 0.9 m wide and 0.6 m deep is considered standard. Sliding windows or pass-through openings allow samples to be delivered from the preparation side without the evaluator seeing the operator, and a signal light lets the evaluator indicate readiness for the next sample.

The following environmental conditions must be maintained inside the testing area:

• Temperature and humidity: A temperature of approximately 20°C and 62% relative humidity are considered optimum for sensory testing of dairy products. The room used for evaluation should have walls of a light cream colour, with a room temperature between 18 and 20°C and relative humidity between 60 and 70%.
• Noise control: Noise levels must be kept to a minimum, and movement of personnel within the testing area should be restricted during evaluation sessions.
• Odour-free environment: The testing area must be kept free from foreign odours. A slight positive air pressure can be maintained to prevent odorous air from entering from other areas of the facility.
• Lighting: Lighting must be uniform, shadow-free, controllable, and of sufficient intensity for evaluating the colour and appearance of samples. Lights with a correlated colour temperature of 6500 K are generally preferred. Special lighting devices such as dimmer switches, coloured filters, or sodium vapour lamps may be used when evaluators need to mask appearance differences and focus solely on taste or texture.

The preparation room 🔗

The preparation room – a dedicated kitchen or laboratory – must be located adjacent to the testing booths but positioned so that evaluators do not pass through it before the session. It must be well-ventilated to prevent odours from prepared samples from drifting into the testing area. Essential equipment includes a working surface, sink, cooking range, oven, refrigerator, deep freezer, blender, balance, dishes, and appropriate utensils. A critical rule: all utensils and cutlery used for sample preparation must be made of materials that do not transfer any odour or flavour to the product.

The sensory panel: who evaluates and how they are selected 🔗

The people conducting the evaluation are just as important as the physical setup. The panel must be composed of experts with sound knowledge of dairy production and experience in sensory evaluation. A panel must include a minimum of three evaluators, one of whom is designated as the panel chairperson, responsible for coordinating the session and ensuring professional conduct throughout.

ISO 8586:2023, the internationally recognised standard for sensory assessor selection and training, outlines a clear progression from screened trainees to trained assessors and ultimately to expert sensory assessors. Candidates are assessed for sensory acuity and descriptive ability before being accepted onto the panel.

Physical fitness and pre-evaluation conduct 🔗

Evaluators must be in good physical condition with fully functional senses of smell and taste. Basic taste recognition screening tests – using solutions of sucrose, sodium chloride, citric acid, caffeine, and monosodium glutamate – help confirm normal taste sensitivity before panel selection is finalised.

Before each evaluation session, there are strict behavioural requirements. Evaluators must not smoke, drink coffee, or consume strongly flavoured food within one to two hours before the session. They must also avoid using strongly scented personal care products such as perfume, aftershave, toothpaste, or mouthwash before sensory analysis, as these can interfere with smell and taste perception.

Panel training 🔗

Training is not a one-off event. ISO 8586 defines the objective of panel training as equipping assessors with foundational knowledge of sensory analysis procedures and developing their ability to perceive, recognise, describe, and discriminate sensory stimuli. Ongoing performance monitoring – checking for repeatability, discrimination ability, and inter-evaluator consistency – is also required to ensure panel reliability over time.

Sample preparation and presentation 🔗

How samples are prepared and presented has a direct bearing on the validity of results. Representative samples must be collected from each batch. All labels, markings, and manufacturer declarations must be removed or covered from the original packaging before coding, ensuring that evaluators remain completely unaware of the product’s origin. The code list is kept inaccessible to evaluators throughout the session.

Temperature at evaluation 🔗

Temperature affects how volatile compounds are released and therefore how accurately aroma can be assessed. Most dairy products are evaluated at 16 to 18°C, while fermented milk and dairy drinks are assessed at a lower temperature of 11 to 13°C. Samples must be brought to the appropriate evaluation temperature before the session begins.

Minimum sample quantities 🔗

Sufficient quantities of each product must be available for a meaningful assessment. As a reference, a minimum of two packaging units is required for products such as pasteurised milk, fermented milk, cream, and butter, while hard, semi-hard, and soft cheeses require one whole cheese per evaluation session.

Order of evaluation 🔗

The sequence in which samples are evaluated matters. Products with milder flavours should always be presented first, as evaluating strongly flavoured samples early can dull sensitivity and make it difficult to assess subtler products afterward. During sessions, evaluators are provided with water, apple pieces, and white bread to neutralise the palate between samples. A maximum of 50 samples may be assessed per day.

The scorecard: structuring the evaluation 🔗

A standardised scorecard is essential for objective, consistent evaluation across panel members and sessions. Each sensory attribute – appearance, colour, odour, and taste – is assigned a defined point value. In official dairy evaluations, a maximum of 20 points can be scored for a single product. Products are then classified by quality class based on total score:

• Extra quality class: 19.0 – 20.0 points
• Quality Class I: 17.0 – 18.9 points
• Quality Class II: 15.0 – 16.9 points

Each panel member scores independently and records their assessment on the sheet. The final score is calculated by averaging the marks of all panel members. If two evaluators differ by more than one point on a single attribute, the panel must re-evaluate that attribute before a final score is recorded.

The sensory evaluation sequence for dairy products 🔗

Within each session, evaluation follows a defined sequence – from the most observable attributes to the most subjective. The sequence is: visual appearance (sight), odour (olfaction), consistency (touch), sound (hearing), and finally taste (flavour). Taste carries the most weight in the final assessment and is always the last attribute evaluated to avoid any bias from prior tasting affecting the appraisal of other attributes. Evaluators assess characteristics such as aroma using structured reference wheels and apply consistent vocabulary – for example, describing milk aroma as clean, grassy, or caramelised – to ensure that findings can be compared across sessions and facilities.

The role of sensory evaluation extends beyond a routine quality check. Sensory perception of finished dairy products – whether cheese, ice cream, or fluid milk – is often the final and most decisive step in quality verification. No instrumental measurement can fully replace the trained human response to what a product looks, smells, and tastes like. When done under properly controlled conditions, with a trained and disciplined panel, sensory evaluation provides dairy producers with one of the most reliable tools available for maintaining product consistency and consumer confidence.

What do you think? If you were setting up a sensory evaluation programme for a small dairy operation, which requirement do you think would be hardest to get right – the physical lab setup, the selection of evaluators, or maintaining consistent sample preparation? And how much do you think evaluator training affects the reliability of results compared to having good lab infrastructure?

References

1. https://milk-ed.eu/sensory-analysis/
2. http://dairy-technology.blogspot.com/2014/01/requirements-for-sensory-evaluation.html
3. https://milk-ed.eu/wp-content/uploads/2022/06/Sensory-evaluation-of-dairy-products_EN.pdf
4. https://blog.ansi.org/ansi/iso-8586-2023-training-of-sensory-assessors/
5. https://foodsafety.institute/food-fundamentals-chemistry/organoleptic-panels-sensory-evaluation/
6. https://www.dlg.org/en/mediacenter/dlg-expert-reports/food-sensory-technology/dlg-expert-report-07-2017-practice-guide-for-sensory-panel-training-part-1
7. https://sensory.ncsu.edu/evaluation/
8. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sensory-evaluation