Lecture 3 - Sensory Evaluation PDF

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Food, Nutrients and The Consumer:Sensory Evaluation:The five senses: Sight (appearance) – visual senses often the first to be used e. colour, glossiness of chocolate, and visual composition of prepared meals – think about packaging Texture – the feel, appearance or consistency of a surface or substa...

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Food, Nutrients and The Consumer: Sensory Evaluation:

The five senses: 1. Sight (appearance) – visual senses often the first to be used e.g. colour, glossiness of chocolate, and visual composition of prepared meals – think about packaging 2. Texture – the feel, appearance or consistency of a surface or substance 2 major components: - Somesthesis – surface response from skin - Kinesthesis/proprioception – deep response from muscles and tendons - Not just in the mouth – manipulation with fingers/hands can generate textual responses with visual information – also information arising from sounds related to handling/chewing 3. Flavour – a combination of sensations derived from several distinct types of chemical stimuli, detected by receptors on the tongue and other oral surfaces A) B) C) D) E)

Bitter Salty Sour Sweet Umami – savour

All 5 basic tastes detected by taste buds 50-100 taste receptor cells in each taste bud Type 1: -

Most abundant taste cell in taste buds Detection of salt taste

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Most extensively studied taste cells Sense either sweet, bitter or umami tastes

Type 2:

Types 3: -

Detection of sour taste

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Not well understood

Type 4:

Sometimes extended to include:  

Odours/aromas – detected by receptors in nasal cavity Burning/cooling – chemical sense that stimulates trigeminal nerves

Odour:       

Food odours shape the way taste and texture are experienced Signal the near presence of edible and inedible foods Often, we are able to smell food before we can see food Smell of pleasant foods can stimulate appetite and influence consumption Ortho-nasally we perceived to originate from the external environment Retro-nasally we perceived to originate from the mouth But this all depends on texture and food form, bite, size, eating rate and chewing efficiency

Sound:   

Many researchers and even consumers rate sound as the least important sense for food perception and consumption Sound plays an important role in our multisensory perception of flavour For example, the crispness, crunchiness or crackliness

What is sensory evaluation?    

Scientific discipline used to analyse reactions to stimuli perceived through the senses The process of determining how a consumer reacts to a product or retail setting using the 5basic sense It is a vital tool for the food industry It can be used in; - New product development - Quality control/assurance - Taint identification - Recipe/process change investigation - Shelf life evaluation - Competitor benchmarking

Types of sensory evaluation:

1.    2.   

Analytical – objective Aims to be neutral and unbiased Comparable to data yielded by chemical or physical measuring apparatus Use specifically trained panels Hedonic/Affective – subjective Consumer testing Subjective impression, such as the popularity of or preference for a product Uses untrained consumers – large panels or small focus groups

(Subjective and Objective sensory evaluation also often linked with chemical and physical study data of the foods) Analytical testing – Objective  Basic discrimination testing – Do two or more products differ from each other?  Descriptive analysis – What are the characteristics of two or more products?  Napping – rapid sensory profiling technique - Products placed on a “map” according to their sensory difference/similarities - Used with large sample sets (10+) - Descriptive terms applied to each sample

Sustainability of profiling techniques:    

Cancer survivors commonly experience taste and smell changes. As well as this their food preferences may alter and their relationship with food may alter Food product development is rarely focused on cancer survivors Not all types of sensory analyses suitable for cancer survivors, also due to potential mental fatigue and other confounders (many individuals might be elderly) Important considerations for the development of nutrient fortified food products

Analytical testing -Subjective

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Hedonic scale Simple comparative e.g. which do you prefer A or B? Structured questioning – e.g. please rate the fruity aroma – like, dislike, or neither Napping

Hedonic Scale:   

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Most widely used scale for measuring food acceptability Developed in 1955 in the armed forces to measure food preferences of soldiers - Quickly adopted by the food industry Now used for measuring the acceptability of foods and beverages, personal care products, household products and cosmetics 9 intervals = more discriminating than shorter scales

Resources needed in sensory evaluation: 

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Subjects – consumers (need to be trained in how to use their senses, how to take a test and familiarise themselves with products) – this can be a lengthy process and not many people can be trained in this way Methods Sample, test plans and analyses – need to take into consideration which test to used and must reflect behavioural and physiological elements in the design e.g. replications of food servings. Try to prevent the risk of bias and different statistical methods used to analyse results from the sensory evaluation sessions Facilities and support services – all panel members in separate booths or controlled environments – limit visual contact between testers and servers for foods. Use paper-based ballots and also can be web-based applications so the analysis is in real time and there is no risk of transcription errors

The importance of the eating environment:  

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Sensory evaluation of foods takes place in a controlled environment usually However, growing recognition that this is not reflecting environment in which end consumers will consume particular foods e.g. samples might be more liked when consuming in home settings rather in a central location In a controlled setting description of eating occasion might “set scene” – also impacts how food liked Alternatively, recreation of natural setting (e.g. coffee shop) More “immersive” context, means that the panels response may be closer to the real-world experience

What are the 6 steps in sensory evaluation?

1. 2. 3. 4. 5.

Appearance of the food Texture of the food Flavour of the food The odour of the food The sound of the food – e.g. crispness

What are potential future sensory studies on gluten-free bakery products? There are more advanced sensory tools to allow further understanding to enhance the development of gluten-free food and ingredients. Some of the ideas proposed include: more research on the acceptance and perception of the sensory properties of gluten-free product options by both coeliac and non-coeliac consumers. The future of the studies will look at consumers at different life-stages; and evaluation of the sensory properties of gluten-free products in combination with other products, accompaniments and within meals. This sensory profiling of the unique properties of naturally gluten-free bakery products, this will optimise the acceptance of these in wider consumer markets.

Which strategy of salt reduction was more successful? And why?        

Institute of Medicine – mandate salt reduction at the food industry level via a strategy of gradual decline Compares the acceptability of different paths to look at of a gradual to an abrupt salt reduction strategy of a high sodium food Looking to see if these trajectories were impacted by individual’s hedonic sensitivity to salt and the motivation to reduce dietary salt intake 83 subjects in a 3-part study Initial taste test 16-week longitudinal study Final taste test At each taste test the subjects indicated liking of tomato juice at 4 salt concentrations ranging from 136mg sodium/serving to 640mg

The most effective strategy of salt reduction was the gradual salt reduction strategy due to the abrupt reduction was paired with an immediate drop in liking the tomato juice, whereas the gradual reduction-maintained likeability throughout the process.

What difference did hedonic sensitivity make to the responses to the salt reduction strategies? Subjects with low hedonic sensitivity responded favourably to both salt reduction strategies and would likely have no difficulty in adjusting to the taste of reduced salt foods. However, subjects with high hedonic sensitivity disliked reduced salt juice at some point during the study, regardless of strategy, and would likely have difficulty in adjusting to the taste of reduced salt foods.

What is the overall “take home” message?

Overall, it is best to gradually reduce the amount of salt in a diet, so its less likely to be noticeable to the participants. It is less likely to have a decreased likeability of a food product if the salt content is reduced gradually.

PTC The Genetics of Bitter Taste:     

PTC = Phenylthiocarbamide A chemist, Arthur Fox, was pouring some powdered PTC into a bottle Some of the powder accidentally blew into the air and a colleague standing nearby complained that the powder tasted bitter Fox tested the PTC powder on his friends and some people tasted nothing, some found it intensely bitter, and others thought it tasted only slightly bitter Dark chocolate and coffee are common bitter tasting foods

The PTC Gene:     

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The tongue is covered with bumps called papillae Each papilla contains multiple taste buds Taste buds are filled with gustatory cells – the cells that do the tasting. The tip of each gustatory cell protrudes through a pore on the surface of the tongue Nerves carry signals from the gustatory cells to the brain The tip of each gustatory cell is covered with an assortment of bitter taste receptors, which can detect a wide variety of compounds. Stimulation of any of these receptors sends a signal to the brain = bitter! Soon after the discovery of PTC research – geneticists determined that there is an inherited component that influences how we taste PTC. The ability to taste PTC (or not) is conveyed by a single gene that codes for a taste receptor on the tongue. The PTC Gene = TAS2R38 There are two common forms (or alleles) of the PTC gene One of the common forms is a tasting allele and the other is a non-tasting allele Each allele codes for a bitter taste receptor protein with a slightly different shape The shape of the receptor protein determines how strongly it can bind to PTC

Natural Selection At Work:

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Its not found in nature The ability to taste it correlates strongly with the ability to taste other bitter substances that don’t occur naturally, many of which are toxins Plants produce a variety of toxic compounds to protect themselves from being eaten The ability to discern bitter taste evolved as a mechanism to prevent early humans from eating poisonous plants We have 30 genes that code for bitter taste receptors Each receptor can interact with several compounds, which allow people to taste a wide variety of bitter substances

To Taste or Not To Taste:  

Some scientists believe that non-tasters of PTC can taste another bitter compound. This scenario would give the greatest selective advantage to heterozygotes, or people who carry one tasting allele and one non-tasting allele

Not so Simple After All:  

PTC sensitivity is often used as an example of a simple Mendelian trait with dominant inheritance The PTC gene has about 85% of the total influence over whether someone is a taster or a non-taster – there are many other things that affect PTC tasting ability – e.g. having a dry mouth, what you ate or drank before and peoples sensitivity may change overtime or on specific days

Potential Health Applications:    

Studies indicate that individuals with the “strong tasters” PTC gene variant were less likely to be smokers This may indicate that people who find PTC bitter are more likely than non-tasters to find the taste of cigarettes bitter and may be less likely to smoke However, other studies suggest that there may be correlations between the ability to taste PTC and preferences for certain types of foods E.g. may be why some people think that broccoli is just too bitter to eat...