Science of senses

The science of SensesL7 : The science of SensesL7

Learning objectives : Learning objectives The sciences of the 5 basic senses as relate to product development Appearance Taste Smell Touch Hearing

Appearance : Appearance Sight describe and evaluate appearance and colour differences between products the assessors for these tasks needs minimum level of visual acuity Some cases the appearance of a product may not be of interest, but it can influence the perception of the flavour and texture characteristics.

Sensory Properties Measured by Sight : Sensory Properties Measured by Sight Shape Size visual texture colour can all be assess by looking at a sample.

Sight: Sensory Attributes : Sight: Sensory Attributes Hue/Colour – the actual colour hue can be defined for sensory testing. Depth of Colour – helpful to discriminate between different levels of saturation or depth of colour, ranging from light to dark. Light colours are less saturated than dark one. Brightness – refers to the intensity of purity of the colour. Clarity – an assessment of the amount of light that will pass through a substance. Shine – the amount of light that is reflected from the surface of a product. Evenness – of colour can be sometimes to be important e.g. Evenness of browning on a sponge cake (blotchy to very even) Other assessment – can refer to distribution of particles within an area – e.g. the evenness of distribution of raisins within a cake. Size/Shape – many sensory attributes have been used in attempts to describe and quantify the shape and size of the product and the preferred vocabulary will be quite dependent on the type of product. Visual Consistency/Texture – many descriptors that can be used to determine the visual texture and consistency of a product. Consistency: "the property of holding together and retaining it's shape." Thick, Thin, Drop, Drippy, Flows

Factors Affecting Colour/Vision Assessments : Factors Affecting Colour/Vision Assessments Lightning correct lightening is important when assessing appearance, especially if assessment of colours is involved Lightning should be uniform in colour and intensity across the entire assessment area and the same for each assessor area should be as far as possible free from shadows artificial daylight conditions are usually recommended for sensory assessments For consumer testing products are usually assessed in similar conditions in which they would be eaten. Decoration an area for appearance assessment should be decorated in natural colours such as light gray or off-white and should be free from colourful distractions such as bright pictures. Portion Size/Shape the actual amount of product or the shape of the cut portion can affect the visual appearance, so uniform portion size and cut is important for consistency of results.

Taste- tongue : Taste- tongue The tongue has four types of papillae: filliform (no taste buds) fungiform foliate Circumvallate These are innervated by three crainal nerves: Fungiform:chorda tympani branch (VII)Circumvallate:glossopharyngeal (IX)Throat:vagus branches (X) The greater superficial petrosal nerve also innervates the soft palate. Papillae consist of many taste buds, and the buds consist of taste receptor cells (each taste bud contains 30-50 cells which are regenerated about once a week). The cells come into contact with fluids in the mouth via hair-like cilia that protrude through pores.

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Slide 10 : Taste or flavour qualities Sweet:carbohydrates with AH,B system (sugar) Salty:elementary monovalent cations (e.g., sodium, lithium) Sour:acids (both inorganic and organics); specific anions affect sensation, pH Bitter:lipophilic molecules. Others Astringency – desirable characteristic of fruit, cider and most important to wine and tea (due to polyphenolic substances) Pungency – describes “hotness” in chillies or capsicum Meatiness Temperature Hot Cold Warm

Science of taste function : Science of taste function Adaptation: Requires stable stimulus (spatial control, no temp or tactile);Has decaying exponential and inverse recovery. After adaptation, water takes on various tastes. This raises questions of sequential effects in triangle and other tests, and indicates that pre-rinses and inter-stimulus rinses are important. Cross Adaptation: The effect of adaptation of one substance to another. In theory, if two substances cross-adapt, they use the same taste receptors.

Slide 12 : Mixture Suppression: Mixture suppression is the rule! Suppression defined: Tastes are weaker in mixtures than they are in equimolar unmixed solutions; Mixtures are less intense than the sum of their components. Exceptions: NaCl in low concentrations enhances the sweetness of sucroseMSG and IMP enhance many different flavors in mixturesMany sweeteners act synergistically with one another (e.g., aspartame and acesulfame-K)

Slide 13 : Release from Suppression: Following adaptation to one component of a mixture, the other component seems to be more intense. It is "released" from suppression.

Slide 14 : Various Taste Modifiers: (weird but true) Gymnea sylvestre (Indian vine): inhibits sweetness Synsepalum dulcificum (miracle fruit): makes sour things taste sweetArtichoke compounds: make water taste sweet.

Factors affect predicting taste reactions : Factors affect predicting taste reactions A juice manufacturer like to achieve a certain level of sourness in the product by acidifying the juice. two acidulants to choose from: How does she go about deciding how much of either acidulant is required to achieve a given level of sourness? 1) Weight may predict sourness: (The more weight of acidulant added, the greater the sourness). HOWEVER: Acids have different molecular weights and different protonations and thus will elicit different sourness reactions at the same weight per volume concentration due to the different number of protons that are released into solution by each acid. 2) Molarity may predict sourness: (The more molecules of acidulant per unit volume, the greater the sourness). HOWEVER: Acids have different dissociation constants and thus will elicit different sourness reactions at the same molar concentrations due to the different number of protons that are released into solution by each acid.

Slide 16 : 3) pH may predict sourness: (The more protons that are released into solutions, the greater the sourness). HOWEVER: Oral tissues and salivary milieu are also reactive and titrate protons off anions in equilibria. Therefore, not all acids are equally sour at equal pH. 4) Titratable Acidity may predict sourness: (The concentration of available protons, down to a level at which the oral tissues may remove them is important). Titratable acidity to a pH of about 4.0 is a good predictor of sourness. However, there are still residual differences in sourness at equal titratable acidities. Other potential factors: Electrostatic interactions (e.g., anion binding near sour, proton receptors) Taste properties of the anions themselves.

Factors Affecting Tasting Ability : Factors Affecting Tasting Ability Adaptation and Fatigue Adaptation – is the physiological change that the taste buds undergo on repeated exposure to a particular stimulus. Fatigue places a limit on the maximum number of products that can be assessed before the quality of the information starts to deteriorate. Genetic Predisposition “Supertasters” who are genetically endowed with a greater than normal number of taste buds. Smoking does not seem to impair assessor performance with respect to the basic tastes But same precautions are taken as with assessors who have just had a meal by allowing a reasonable interval of time.

Best Way to Taste : Best Way to Taste Liquid Food It is recommended that tasters should take small sips of solutions and retain them in their mouth for 2-3 seconds A gap of at least 15 seconds (or longer for strong stimuli) should then elapse before the next product is presented. Solid Food It is more difficult to define exact timings because individuals display very different chewing and swallowing behaviour It may be advisable to allow them to eat in their own natural style A suitable palate recovery period between products should again be observed.

Do Taste and Smell Interact? : Do Taste and Smell Interact? Of course they do But sometimes under controlled conditions e.g. in a psychophysical laboratory, simple mixtures of sucrose (a tastant) and citral (an odorant) show almost complete (90%) addition, and no influence on the intensity ratings of each other when mixed.

Flavor : Flavor

Smell : Smell Olfaction Sense of smell can detect many different odors when sniffed through the nose Also important for detecting volatiles given off by food items in the mouth as part of the flavour perception. The sense of smell is a key input to sensory analysis. Odor Herbs and spices Vegetables Fruit Meat Synthetic flavoring OFF-flavors Taints

Factors Affecting Odor Assessments : Factors Affecting Odor Assessments 1. Location the area set aside for odor assessment needs to be free from smells and also requires a form of air extraction to remove the odor from the vicinity during assessment necessary because adaptation to one odor may have an effect on the perception of other odors. 2.Health/Colds cold and similar blockage of the respiratory system will affect the perception of odors Other factors such as hunger, mood, concentration may all affect the perception of odors. 3.Volatility Temperature influences the strength of an odor by affecting the volatility of the odourant molecules It may therefore be important to asses odors and hence flavors at temperatures at which they are to be served or used Humidity has an effect on the perception of odors.

Touch : Touch Texture “the attributes of a substances resulting from a combination of physical properties and perceived by the senses of touch (including kinaethesia and mouthfeel), sight and hearing”. Physical properties may include size, shape, number, nature and conformation of constituent structural elements. Rough Smooth Hard Soft Dry Moist Heavy Light

Role of texture : : Role of texture : in determining the quality of product depends on the food type, with three main grouping being given: Critical where texture is the dominant quality characteristic e.g. celery Important where texture is a significant but not dominant characteristic and is on an equal level with flavour and appearance e.g. most fruits Negligible where texture makes little contribution e.g. thin soup.

Classification of Texture : Classification of Texture Mechanical characteristics related to the reaction of food to stress Geometrical properties related to the size, shape and orientation of the particles within the food Other characteristics related to the perception of moisture and fat content.

The mechanical characteristics are separated into: : The mechanical characteristics are separated into: Primary parameters – hardness, cohesiveness, viscosity, elasticity and adhesiveness Secondary parameters – brittleness, chewiness and gumminess.

A 3-stage sequence for assessing texture : A 3-stage sequence for assessing texture Initial phase the textural qualities perceived on the first bite, before saliva dissolves or modifies the shape or arrangement of particles Masticatory phase perceived during chewing Residual phase textural change that occurs during mastication and effects that causes mouth coating (usually after the sample has been swallowed).

Variables Affecting the Sensory Assessment of Texture : Variables Affecting the Sensory Assessment of Texture Standardization of test samples is important to ensure that reliable results are given: the size and shape of test sample the form in which any uncooked food is presented i.e. peeled, sliced or ground the cooking conditions and serving temperature the humidity (important for some products) the implements and containers used.

Other parameters : Other parameters Viscosity Thick Thin Liquid Runny Temperature – food safety issues Hot Cold Warm Irritation

Hear : Hear Sound Crispy Crunchy Silent

Altogether: HOW DO THE SENSES INTERACT : Altogether: HOW DO THE SENSES INTERACT Three main sensory characteristics of foods are appearance, texture and flavour. Appearance assessments are usually carried out using the sense of sight alone The perceptions of both texture and flavour involve a number of different sense modes

Conclusion : Conclusion The five senses are critical in any sensory evaluation test. Senses need to be in good health to perform functions well and to reduce bias The success of the product developed depends much on the sensory evaluation data