Week 2 Factors Affecting Sensory Responses.pptx

FDSC 20040 Sensory Analysis Factors Affecting Sensory Responses Dr. Amalia Scannell Module Co-ordinator 1 Factors affecting Sensory Judgements A number of issues can affect the judgments made by a person at a given time. These may be  Food related  People Related  Environment related 2 Some...

FDSC 20040 Sensory Analysis Factors Affecting Sensory Responses Dr. Amalia Scannell Module Co-ordinator 1 Factors affecting Sensory Judgements A number of issues can affect the judgments made by a person at a given time. These may be  Food related  People Related  Environment related 2 Some Food-related Issues • Food components may interact causing variations/ unexpected changes in the sensory profile. Examples of these include:  Enhancement ; presence of one substance increasing perceived intensity of second substance  Synergy ; presence of one substance increasing the combined intensity of two substances. Intensity of mix is greater than the sum of intensities of components.  Suppression; presence on one substance decreasing the perceived intensity of a mix of 2 or more substances 3 Some Food-related Issues • Increasing the viscosity of a product can decrease the perception of some tastes. • Use of incongruent colours (e.g. colouring a strawberry flavoured drink green, or Skittles Randoms) can alter flavour perception./ • Flavour profiles are temperature dependent since the concentration of volatiles released increase with increasing temperature.  Food should be assessed at the temperature it will be consumed at e.g. soup should be the same temperature for all assessors and should not he hot held so long that the sensory profile perceived by the last assessors has changed from the soup tasted by the first assessors. 4 Some People-related Issues • General well being • Mood • Illness Medication Suffering from fever or cold Skin or nervous system disorders for a tactile panel • Hunger/ fullness  Plan sensory tests to be at ~ 2 hr after a major meal • • • • Pregnancy/ Menstruation Dentition (e.g. wearing dentures) Emotional upset Physiology (e.g. of taste/smell)  Adaptation [decrease in or change in sensitivity to a given stimulus due to continued exposure to that or a similar stimulus] of the chemical senses can occur. Saturation of taste/ olfactory receptors • Variability in thresholds and intensity ratings between assessors 5 Some People-related Issues • Psychological Errors can occur when making sensory judgements – these include Expectation error Error of habituation / anticipation Stimulus error Logical error Halo effect Mutual suggestion / distractions Lack of motivation Capriciousness versus timidity Order of sample presentation (these include Contrast effects, Group effects, Error of central tendency, Pattern effects, Time error / positional bias, Session effect and carry -over) 6 Some Environment-related Issues • Poor concentration due to  Excessive noise (e.g. building works, noisy pipes)  Mutual distraction (able to see neighbours answer sheet)  Discomfort, due to fluctuating temperature/ air humidity poor seating/ desk design). • Residual smell in the air  dump outside, blocked drains, cleaning agents etc. • Non-uniform / inadequate lighting ISO Standards give excellent guidance on how to design a facility to eliminate environmental effects. 7 Design of Test Rooms for Sensory Analysis Constant controlled conditions Minimum of distractions Requirements:  Preparation area  Testing area with individual booths  Discussion area ISO 8589 – 1988 BS 7183 - 1989 8 Design of Test Rooms for Sensory Analysis Temperature and RH  Constant,  Controllable  Perceived as comfortable 20 – 22 °C 50 – 55% Odour  Air conditioner with activated carbon filters  Slight positive pressure  All fixtures + fittings odour free and odour resistant  Avoid cleaning agents that leave odours on surfaces 9 Design of Test Rooms for Sensory Analysis Decoration  Neutral – off white or grey Lighting  Uniform / Even  Shadow free  Controllable 300 – 500 lux at surface  Coloured light source (red / green) 10 Testing booths  As many as resources / needs allow  Permanent / Temporary  Ideally adjacent to prep room  0.9m X 0.6m (wxd)  Desk (~76cm) or counter (~92cm) height  Lateral dividers extending 0.3 m beyond counter  Hatches (sliding door / bread box) flush with countertop  Counter on serving area  Communication – light /coloured card/ intercom  Numbered  Comfortable seat (0.35m from working surface) 11 TESTING BOOTH 0.6m 0.75m 0.3 m 0.9m 12 TEMPORARY SENSORY SET UP Table with Removable Dividers Mobile Individual booth 13 Group Work Area  Discussion between assessors and Panel leader  Training sessions  De-briefing  Focus groups etc.  5 – 10 assessors  Comfortable chairs  Table 14 Preparation Area  In vicinity of test area  Well ventilated / good odour extraction  Work surface  Sink  Storage units  Sample containers/ trays  Balance  Fridge / Freezers / Cookers / Microwave  Wash up facility  Adequate water  Bottled water / Double distilled H2O for rinsing 15 Test Protocol Considerations  By using appropriate facilities and employing good experimental designs, all these effects can be minimised.  It is generally recommended where possible to use a balanced randomised order of presentation.  This is important for statistical analysis of results and avoiding the impact of bias over the whole experiment.  Balanced means that each of the possible combinations is presented an equal number of times. If samples are large then a balanced incomplete block design can be used.  Randomised means that order of selected combinations was chosen by chance.  Coded samples: Use of random 3digit codes for each sample removes expectation error from the experiment 16 Test Protocol Considerations Treat all samples identically! Consider the effects of the following on the evaluation of products: Sample size and shape (regular vs irregular)  Visual appearance of sample Serving temperature Serving containers Use of carrier (used to assist he tasting of a product e.g. blotters for perfume; crackers for dairy spreads, milk with cereal) . Use of palate cleansers Should panellists rinse mouth between samples Should samples be expectorated or swallowed How many samples per session Randomisation + Blind labelling 17 Sensory Test booth set-up for Olive Oil testing Carrier = bread Communicating hatch u rat pe Tem trol n co www.olive-tourism.com re Answer sheet & pen 18 Sensory Test Methods SELECTING A TEST: The test we choose is dependent of the question we need to answer. Objective Test : Give Objective Data Is there a difference? - Difference/ Discrimination tests :Use trained panel How are they different? – Descriptive Tests: Use a trained panel Subjective Test : Give data on degree of liking/ acceptability Is the difference Acceptable? Hedonic/ consumer tests: Use untrained panel 19 SENSOR Y METHO DS Analytical Trained/ selected panel Objective Quantitative Descriptive Tests Affective Consumer/ user groups Subjective/ Hedonic Quantitative & Qualitative Discriminatio n/ Difference Tests Acceptability/ preference tests 20