Fish Microbiology and Quality Assurance

Unit 9 - Assurance and management quality of fish

9.1.1. Sensory methods
Sensory evaluation has been defined as a scientific discipline used to evoke, measure, analyze and interpret reactions to those characteristics of foods and materials as they are perceived by the senses of sight, smell, taste, touch and hearing. These are also referred to as organoleptic methods.

Categories of sensory evaluation
Sensory evaluation tests can be divided into two general categories
1. Affective or subjective evaluation tests
The affective tests help to evaluate preference and / or acceptance of products. In these tests, the spontaneous personal reaction of the panelist is evoked in order to determine preference or acceptance. These are subjective tests designed to obtain the original and spontaneous impressions of the panelists.
2. Analytical or objective evaluation tests
Analytical or objective tests help in evaluating the sensory characteristics of products such as similarities or differences, quality and / or quantity. The analytical tests consider only some aspect of sensory quality of the product itself and not the personal reaction of the panelist. The panel serves as the analytical tool. The International Organization for Standardization (ISO) defines an objective method as "a method in which the effects of personal influence are minimized".

Advantages of sensory evaluation of quality

• Sensory or organoleptic methods are fully dependent upon the human senses for assessing the quality. All the senses except hearing are used in fish industries to judge quality by sight (appearance), touch (texture),,smell (odour) and taste (flavour).
• Considered as a best method since the consumer can decide what he/ she likes only based on his/ her senses.
• Sensory methods have the great advantage as human beings are very adaptable and assess quality attributes such as odours, appearance, defects etc simultaneously.
• Human senses are better than instruments in discriminating and recognizing complexities involved in assessing product quality.

Factors involved in assessing sensory quality
Quality factors assessed by sensory methods include sight and touch, and odour and flavour.
Sight and touch
This involves evaluating the quality by sight and touch for quality parameters such as size, colour, defects and spoilage. This can be accomplished with minimum trainng by fishermen to segregate catch by species and size. Testing with fingers and eyes remains the only effective way for detecting the bones in the fish flesh and matching of colour. The sense of touch in fingers or mouth are useful in assessing textural attributes such as firmness, softness, mushiness, rubberiness, woodiness, mealiness, succulence and dryness
Odour and flavour
Odour and flavour of a product is assessed by smelling through nose and tasting through tongue. Any one with some practice can distinguish the whole pattern of changes in odour between very fresh and very spoiled fish easily and rapidly thereby enabling accurate determination of degree of freshness. Similarly, the intensity of off-odours, taints and unusual intrinsic odours can be readily detected.
Judges or panelists
A judge or panelist is an experienced or trained person who carries out sensory assessments of products. One or more judges assessing the quality of same product independently eliminates the the risk of major mistakes through prejudice or bias. The average results of a panel of judges for a product give a correct measure of the attribute in question than is possible with a single judge. A group of judges involved in quality testing is often called as a taste panel when their judgements involve tasting the product.

Precautions to be taken fo conducting sensory tests

• Sensory tests should be conducted in a separate area or room isolated from processing and other industrial operations.
• Standardized lighting conditions should be used for carrying out colour comparisons as colour of a product appears different under different types of lighting.
• Interference from external sources should be avoided or minimized.
• Identical heating or cooking process should be carried out on every occasion when samples are to be tasted.
• Distractions to the panelists should be avoided as sensory assessments require a certain amount of concentration.