Masterclass
30 June 2009
Sensory Overload
1
General Introduction
Welcome to the Masterclass – Sensory Overload. This information
pack includes introductions to the people who will be working with
you today, and summaries of the activities you will participate in. It
also contains important information about how to keep safe during
today’s activities.
Table of Contents
PEOPLE INVOLVED
3
SAFETY AND RESPONSIBILITY
4
SENSORY PERCEPTION AND HOW THE SENSES CAN INTERACT
8
MEASURING FOOD FLAVOUR
16
SOIL QUALITY AND EARTHWORM DIVERSITY
22
FURTHER INFORMATION AND LINKS
26
Timetable
Time
Activity
Location
10.50-11.00
Arrival/Housekeeping/Agenda
11.00-11.20
Mini lecture by Dr Joanne Hort
LR9, Food
Sciences
11.20-11.55
Sensory Perception
Sensory Suite,
Main Building
11.55-12.30
Measuring Food Flavour
APCI-MS Lab,
Food Sciences
12.30-1.15
Lunch
Rushcliffe
Restaurant
1.15-2.15
Environment Lab and Field Work Session
Teaching Lab,
Food Sciences
2.15-2.30
Q & A Session
2.30-3.00
Tour of the Arboretum
2
People involved
Dr Joanne Hort is Associate Professor in Sensory Science in the Division of
Food Sciences at the University of Nottingham. Initially, she studied Food
Technology and began her career in teaching. However, she returned to
University to receive her doctorate concerning the modelling of the sensory
attributes of cheese from analytical and instrumental measures in 1998. As
a lecturer at Sheffield Hallam University she carried out sensory
consultancy for local industry, developed a sensory program at
undergraduate level and oversaw the installation of new sensory facilities
before being appointed as Lecturer in Sensory Science at the University of
Nottingham in 2002. She has since established the University of
Nottingham Sensory Science Centre, which is renowned for both its sensory
training and research into flavour perception. She delivers sensory courses
at both undergraduate and postgraduate level and is Course Director for
the Postgraduate Certificate in Sensory Science. Her research interests
focus on the multimodal aspects of flavour perception and she has
published several articles in this area, together with oral presentations and
posters at international Symposia. She is a founder member of the
Professional Food Sensory Group of the Institute of Food Science and
Technology and was on the organising committee of the 6th International
Pangborn Symposium in the UK in 2005.
Dr Amy Rogers is postdoc in ecology. She studied for her BA in Natural
Sciences at Cambridge University and then went travelling for a couple of
years, working on research projects in Australia and America. She did a
PhD on bird songs at Melbourne University in Australia and then returned to
the UK to work as a secondary school science teacher. Whilst she was
teaching she had the opportunity to go on a scientific expedition to
Antarctica and it made her realise she wanted to do more science outreach.
She is now working on an outreach project that aims to encourage people
to go outside and study the environment.
Emily Boothroyd is originally from Leeds, where she completed A levels in
English Literature, Latin, Chemistry and an AS level in Home Economics.
She graduated from Northumbria University at Newcastle with a degree in
Forensic Science. Her passion for food and flavour led her to embark upon a
PhD in Food Sciences here at the University of Nottingham. Based in Sutton
Bonington’s Samworth Flavour Laboratory, she is in her first year of her
PhD research project into the aroma character of malt whisky.
Vicky Whelan is a PhD student in Food Sciences, based at Sutton
Bonington Campus. She is originally from the Wirral and completed A
levels in Biology, Chemistry, Food Technology, General Studies and an AS
level in English Literature. She completed a 4 year undergraduate degree
at the University of Nottingham, studying Food Science with European
Studies, during which she spent 6 months studying in Valencia, Spain.
After completing her degree she then decided to stay to do a PhD on “the
sensory properties of chocolate in different matrices”.
3
Safety and Responsibility
We want to make sure your visit to the University of Nottingham is
as safe and interesting as possible. Please read the notes below and,
while on campus today, please ensure you follow all instructions from
your teachers and the researchers leading the activities.
Please be aware of where you and your belongings are at all times.
In every building you visit, you will be told where the nearest
emergency exit is. If you hear an alarm, please make your way
quickly and calmly to the exit.
No bags or coats should be taken into laboratories. In laboratories,
please do not touch any equipment unless you are specifically invited
to do so. You may be asked to wear a lab coat, gloves and/or
goggles for some of the activities. If you fail to do so, you will not be
allowed to participate.
If at any point in the day you are injured, you must inform the
researcher you are working with or another member of staff
immediately. Certified First Aiders will be available to help you.
Thank you very much. With your cooperation we can have a safe
and productive day. A full risk assessment has been completed for
today’s activities. If you would like to see a copy, please ask.
Laboratory Safety
The laboratories are equipped and run so that with appropriate care,
you can work without risking the health and safety of yourself and
others. Accidents are unexpected or undesirable events, but they
are avoidable with due care and attention.
You have a duty of care to work in a way that will not harm
the health and safety of yourself and/or others.
All experimental procedures are assessed for risks, any necessary
safety measures put in place, and documentary evidence kept. All
containers in the laboratory are labelled with their relevant hazards
and any equipment that may present a hazard or needs instruction
before use will carry clear notices.
Ensure that you read any methods before and during the practical
class, listen to instructions from staff and watch carefully any
demonstrations of experimental procedures.
4
REMEMBER: Any mishap with a chemical (or apparatus) MUST be
reported to a member of staff IMMEDIATELY so that they can deal
with the problem and remove any hazards correctly.
Safety is an integral part of good laboratory practice. Even LOW
HAZARD chemicals may be hazardous if misused.
Risks from
hazardous chemicals are minimised by handling them correctly.
HAZARDOUS chemicals require careful handling at all times because
of one or more of the following characteristics:
(a) flammability
(b) explosive nature
(c)
toxic, hazardous, irritant, etc:
with effects on or through the skin.
with effects on or through the respiratory tract.
with effects on or through the eye.
with effects following ingestion.
(d) reactive with water.
(e) reactive with air.
(f)
detrimental effect on the environment – especially to
aquatic life.
Containers of hazardous chemicals
indicating the type of danger.
Toxic
Highly Flammable
carry
Explosive
a
pictogram
Biological Hazard
(Yellow with black border/text)
Corrosive
Harmful, Irritant
Oxidising
(Orange with black text)
Ensure that you know how to deal with any spillage BEFORE you
embark on an experiment.
Do not ignore the warning signs displayed in the School. They are
there for your protection. The British and European standard safety
signs are used:
5
Prohibitory Signs: e.g. “No Smoking”, are circular with a
red border and crossbar over a black symbol on a white
background.
Warning Signs: e.g. “Caution, risk of ionising radiation”,
are triangular with a black border on a yellow background.
Mandatory Signs: e.g. “Eye Protection”, are circular on a
blue background with symbols in white; used when there is
an obligation to wear safety equipment.
Emergency Signs: e.g. “Emergency Shower”, square or rectangular,
on a green background with symbols in white.
Fire doors must be kept closed at all times. Know where the firefighting, first-aid equipment, eye-wash and emergency showers are
situated.
Ensure that you know the location of fire exits.
In the event of a FIRE ALARM or an EMERGENCY EVACUATION of the
laboratory, turn off all your equipment as you leave the laboratory
and follow staff to the fire assembly point.
Working Safely in the Masterclass
Before commencing any operation in the laboratory give due care
and attention to how the procedure can be carried out without risk to
yourself or fellow workers. If you are in doubt, consult a member of
staff before you start.
Containers should be opened with caution and away from the face.
Take care not to ingest or breathe in vapours or powders.
Wear nitrile gloves when handling hazardous chemicals.
Open wounds, e.g. cuts on hands should be protected by a wound
dressing / band aid.
• Turn back over-long cuffs on clothes and laboratory coats to
reduce the chances of knocking over equipment or contaminating
cuffs / sleeves.
• Do not put pens / fingers etc in mouths and do not eat or drink
anything, including sweets or gum.
• Do not rub eyes / face with contaminated hands /nitrile gloves.
•
•
•
•
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• Risks are minimised by working tidily, cleanly and avoiding
spillages.
• All spillages must be wiped up immediately.
• Dispose of all products, by-products and surplus chemicals
correctly.
• IF IN DOUBT – ASK
• Wash hands at the end of your laboratory session.
Spillages / accidents / FIRST AID
• Spillages / splashes on the skin should be rinsed off immediately
with plenty of cold running water, then washed with soap and
warm water.
• Any splashes in the eye(s) should be washed out immediately with
an eye wash bottle and / or with plenty of cold running water.
• All cuts and scrapes on hands should be rinsed with cold running
water.
• Any burns should be held under cold running water for at least 10
minutes.
Seek advice from a member of staff if you have an accident or if you
feel unwell. A trained first aider will give advice, ensure any injuries
are treated and that relevant documentation is completed.
Glassware
• Do not use any glassware that has chips or cracks – hand it to a
member of staff for disposal.
• Take care when rinsing out glassware for reuse or to send for
washing – if there are any chipped edges or cracks – hand to a
member of staff – do not rinse out.
• In the event of breakages, do not pick up the pieces of glass. Ask
a member of staff to sweep up the pieces with a brush and
dustpan.
Risk is associated with glassware, electrical, mechanical and high/low
pressure apparatus. Be aware of potential risks before using any
equipment.
7
Sensory perception and how the senses can interact
Victoria Whelan
What is sensory analysis?
Sensory analysis is basically getting people to assess things, for example by taste
or smell, or by looking at the appearance of things. They are then asked to give
their opinion about certain aspects. This could be giving their opinion about how
much they like something or whether they think something is sweet enough for
example. This type of sensory analysis is commonly associated with consumer
studies when you want to know people’s liking for a product and which product
they prefer.
Alternatively sensory analysis could involve asking people to rate samples for an
attribute or set of attributes. For example they may be rating bitterness and would
give a score out of 10 for how bitter they find the sample to be. In this case they
give no mention about how much they like the sample and instead are purely
rating the sample on a scale for the attribute in question. This involves using
people as an “instrument” to gain information about the samples.
Sensory tests often take place in booths, as you will see today in the sensory suite.
When panellists come to take part in the tests they are asked not to wear perfume
or lipstick because this could interfere with their perception. In addition they are
asked not to eat or drink strong foods before attending a panel. These include for
example curries, which could also interfere with their sensory perception. When
they are in the booths they are asked to sit quietly and not discuss the samples
with others because this could change their opinion.
The tests can take place on a computer or can be done on paper. The samples are
provided to the panellists labelled with a 3 digit code, for example 289. This is to
prevent any biased answers. For example presenting samples labelled A, B, C or
1, 2, 3 suggests that there is an order and could affect the way that people assess
the samples, particularly if asked to put them in the order they like them. But
what you want is for them not to be influenced by the label of the sample, so a
random code helps prevent this.
Flavour
Flavour is very important to us because it is what gives us our enjoyment of food.
For this reason flavour is very important to companies, which therefore makes
sensory analysis very important because it tells us what people like and want and
how people perceive a product.
How would you define flavour?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
8
What is flavour?
Flavour is the result of integration of information from our
senses, or modalities, within the brain. All of the modalities
are important, not only taste and smell but also
touch/texture, sight and sound.
SOUND
Think about how the sound
when you bite into an apple
or a cracker influences
perception
AROMA
If your nose is blocked (if you
have a cold) the aroma volatiles
can’t interact with the odour
receptors – try holding your
nose when you drink the banana
solutions – what difference does
it make?
SIGHT
The sight of a beautifully presented dish can
certainly get us salivating and vision was once
considered the overriding sense but would you
eat a lovely looking fish if it smelt rancid? Smell
the coloured solutions – can you tell what
flavour they are?
TASTE
Some tastants can increase flavour
intensity when paired with a congruent,
or harmonious aroma – try the banana
flavoured drinks and notice the
difference between those with and
without sugar
TOUCH/TEXTURE
The characteristic mouthfeel of chocolate, the smoothness of icecream. Often texture can be similar, try holding your nose when
you eat chunks of apple and turnip – can you tell a difference?
Chemesthesis is responsible for the ‘burn’ of chilli
peppers, the ‘tingle’ of a fizzy drink and the ‘sting’ of
horseradish
9
A matter of taste
Non-volatile compounds in food dissolve in saliva and are carried into the
taste pore to interact with receptors. The receptors are housed in taste buds
which are located on papillae on the tongue’s surface, the soft palate,
pharynx and epiglottis.
Currently thought to be 5 primary tastes; sweet, salty, bitter, sour, and
umami.
Each taste bud contains between 50-150 TRC’s
representative of the 5 taste sensations
SALTY
SWEET
SOUR
BITTER
(Chandrashekar, Hoon
et al. 2006)
UMAMI
Did you know?
The sense of taste is known as
gustation. We have ~10,000
taste buds and taste cells
regenerate every 2wks or so
Many factors can affect taste
sensitivity such as composition of
saliva, age (no’s of taste buds can
start to decline >60yrs), illness,
drugs, genetics, hormones and even
how hungry we are!
‘UMAMI’ means ‘deliciousness’ and is a
savoury, meaty taste characterised by foods like
parmesan, dark mushrooms and soy sauce
Did you know?
Cats can’t taste ‘sweet’ as they
lack part of the sweet receptor
We are born with an innate liking for ‘sweet’ and disliking for ‘bitter’. Sweet tasting
foods are usually energy rich whilst a bitter taste may indicate toxins. Experience and
learning shape taste preferences.
Current research is investigating whether there
may be other taste receptors specifically
sensitive to calcium and fat
10
Therefore flavour is the combination of all of the senses and you need all of
the information in order to come to a conclusion. For example you might say that
something tastes like banana but it is actually the combination of smell and taste
that makes you come to this conclusion, and if you take away the aroma then you
won’t taste the banana. It has also been shown that if you present banana aroma
without the sugar then you won’t taste the banana. This shows how both aroma
and taste interact to give banana flavour.
Task 1 – Banana Experiment to demonstrate taste-aroma
interactions
You will be presented with 3 banana flavoured samples to taste and you should
follow the protocol and write down what you think about the samples in terms of
how they taste.
Protocol: 1.
Sample 1 (½ of the sample) – Don’t drink all of sample 1 (save some for
later).
When you consume the sample pinch the
nose.
After swallowing unpinch the nose.
What did you notice when you had your nose pinched?
__________________________________________________________
What did you notice when you unpinched your nose?
__________________________________________________________
2.
Sample 1 (the other ½ of the sample) – Consume the rest of sample 1
Sample 2 – Consume Sample 2 straight after (There is no need to pinch your
nose when consuming this sample).
How did you find this sample?
__________________________________________________________
3.
Sample 3 - Consume Sample 3 (There is no need to pinch your nose when
consuming this sample).
How did you find this sample?
__________________________________________________________
11
Explanation of the results
Sample 1 (Banana flavour + sugar) – You probably will have noticed that when
you had your nose pinched you couldn’t taste banana but once you unpinched your
nose then you could taste the banana. This is because when you had your nose
pinched, the banana aroma couldn’t get to the receptors in the nose, so you were
relying on taste alone. Once you unpinched the nose then the banana aroma could
get to the receptors in the nose and combined with the taste of sugar, the brain
recognises it as banana flavour. This highlights that the sense of smell is required
in order to taste banana flavour.
Sample 2 (Sugar alone) – You will probably have found that you could still taste
banana. This is because by tasting sample 1 before sample 2, you will still have
banana aroma reaching the nose receptors. And then by having the sugar sample
you have reactivated the brain to recognise the banana flavour. This highlights
how banana flavour is driven by sugar. However, if you waited a while before
tasting sample 2 then you may only taste sugar and not taste banana flavour. This
is because you have no banana flavour to reactivate.
Sample 3 (Banana flavour alone) – You will probably have found that this
sample tasted like water but smelt like banana. This is because there is no sugar
in the sample, and you associate banana flavour with sugar and therefore don’t
recognise banana flavour unless sugar is present. This highlights that we associate
banana flavour as being with sugar because most banana flavoured things that we
all know are sweet. Therefore both sugar and banana flavour need to be present
to taste banana.
Task 2 – Demonstrating Colour-Aroma Interactions
The colour of food is very important to our perception of a foods’ flavour. The
appearance is what provides us with our first impression of the food, so that we
already have a pre-conception of what we think it will be like. It is very difficult to
override this initial idea that we have and if something is flavoured differently to
what the colour suggests then we can get confused and still think that it is the
flavour the appearance suggests. This has been demonstrated with wine, where
white wine that has been coloured red has been described by wine tasters using
red wine descriptors because they are expecting it to be red wine.
In this task I hope to highlight how colour impacts on flavour.
You have been provided with 6 different coloured solutions. You need to SMELL
(not taste) each of the samples and write down on the following page what flavour
you think the sample is.
12
What flavour do you think the bottles are?
Write what you think in the boxes below.
A
B
C
D
E
F
13
Task 3 – Are you a Supertaster???
There are 2 commonly used tests to find out whether you are a non-taster, taster
or supertaster. These are papillae counting and PROP sensitivity testing. Today
we are just going to carry out papillae counting to establish an idea of what sort of
taster you are.
WHAT ARE YOU? – TAKE THE TASTE TEST!
•
Papillae Count
- Paint the tip of your tongue with blue dye using a cotton bud (not too much!)
- Use a mirror to decide if you have few, some or many taste buds (see below).
The fungiform papillae are
small pinkish dots. They
have the least number of
papillae.
The fungiform papillae are
larger and more rounded.
The fungiform papillae cover
the tongue and there are
cracks caused by lots of taste
buds. They have a greater
densit y of taste buds.
The pink dots are your fungiform papillae - they don't take up the food colouring.
These papillae are the tiny bumps on your tongue that house your taste buds. The
more papillae you have, the more taste buds you have and the more sensitive to
taste you are. On average, non-tasters have fewer than 15 papillae in this area, while
supertasters have over 30.
If there are many taste buds then it would be expected that you are a supertaster,
which means it would be expected that you would be more susceptible to
bitterness and could dislike bitter foods or spicy foods because they are found to be
too intense for you. Non-tasters would have very few papillae.
How many fungiform papillae can you count?
__________________________________________________
Are you a non-taster, taster or supertaster?
__________________________________________________
14
What Makes a Supertaster?
•
Homozygous for the dominant PROP gene (PAV:PAV)
•
Taste of PROP is intensely bitter.
•
Numerous fungiform papillae
Taster status and diet selection: implications for health
•
SUPERTASTERS tend to have extreme likes and dislikes. They avoid bitter
tasting foods, such as cruciferous vegetables (like broccoli), which contain
many substances linked to cancer prevention.
•
NON-TASTERS eat a wide range of foods and may have increased
acceptance of fat and sweet foods.
Could taster status act as a marker for those at risk of diet related disease?
Some Facts!
•
Women are more likely to be tasters and are more sensitive to the bitter
taste of PROP than men.
•
25% Caucasians, 10% Asians and 5% Africans are non-tasters.
•
All populations currently studied have non-tasters except a small group of
Brazilian Indians.
•
The distribution of Non-tasters/Tasters/Supertasters in Western population
is around 25/50/25.
•
Children are more sensitive to bitterness, which may explain why they are
more fussy eaters.
15
Measuring Food Flavour
Emily Boothroyd
What do you think is the difference between flavour and aroma?
Flavour Perception
Have you ever had a bad cold with a blocked nose, and found you
were unable to taste your food? Or pinched your nose to eat
something you didn’t like the taste of, only to let go and find that you
could still taste it?
This is because when you eat, volatile compounds from the food you
are chewing are released into your nose, where they bind with
olfactory receptors in the nasal membrane. A chemical signal is then
passed on via neurons to the olfactory bulb in the brain. Here the
signal is processed and memories are recalled which identify the
smell. This is called retronasal olfaction, because the volatiles travel
from your mouth into the back of the nasal cavity where it is
detected by the receptors.
1
2
3
4
1. Olfactory bulb
2. Olfactory receptors
3. The pathway of
orthonasal olfaction
4. The pathway of
retronasal olfaction
Depending on their molecular structure, some odour compounds bind
to the olfactory receptors more than others, which results in a
stronger smell, even when the odours may be present at the same
concentration.
Therefore, if we can measure the profile of volatiles which escape
from the nose while eating, we can get a better idea of the actual
flavours being perceived at the time of consumption.
In the lab, we do this using a technique called Atmospheric Pressure
Chemical Ionisation Mass Spectrometry or APCI-MS.
16
Atmospheric Pressure Chemical Ionisation Mass Spectrometry
This technique analyses the gaseous phase using the differences
between the masses and charges of ionised molecules to separate
the volatiles present in the sample.
2
Sample
Introduced
1
3
1. Introduction of the sample
The sample headspace (the gas phase above a sample) or a person’s
breath is introduced into the inlet port of the machine.
The system works under a vacuum, therefore due to the difference in
pressure it is constantly taking in and sampling the volatiles in the
lab air.
2. Ionisation in the Gas Phase: Corona Discharge
At atmospheric pressure, the sample is heated and sprayed with a
high flow rate of nitrogen gas to create a cloud of gaseous particles.
The ‘cloud’ then interacts with a corona discharge operating at a high
voltage, creating protonated molecular ions (M+H)+.
3. Analysing the ions: Quadrupole Mass Analyser
The quadrupole mass analyser consists of 4 parallel rods with a fixed
electrical current and an alternating frequency applied to them. The
ions pass through the centre (as shown below) and, affected by the
electric fields acting upon them, they are detected according to their
mass to charge ratios (m/z).
17
Other applications of APCI-MS include:
• On-line chemistry – the analysis of cooked flavours
(http://wwwwip.nottingham.ac.uk/biosciences/foodsci/flavour/frg_thermal_
flavour.php)
• Pheromone analysis e.g. parasitic wasps
(http://www.nottingham.ac.uk/biosciences/foodsci/flavour/frg_
research_highlights.php#following)
SNIFFING ACTIVITY: Minty Molecules
Look at the following pairs of compounds.
What differences can you spot between each pair?
18
Carvone displays stereoisomerism, which means that the two
molecules (isomers) share both the same molecular formula and
sequence. More specifically, they are enantiomers, which mean they
are complete mirror images and therefore cannot be superimposed
on each other.
With such similar structures, do you think that the pairs will smell
similar?
You will have an opportunity to find out if you are correct when you
smell these compounds during the activity today.
You can write down what they actually smell like in the table below.
Compound
- Menthone
Aroma Descriptors
- Menthol
R-(-)-Carvone
S-(+)Carvone
19
CHEWING GUM ACTIVITY: Breath-By-Breath Analysis
Last time you ate some mint
chewing gum do you remember:
a) how long it took to
reach its maximum
minty flavour intensity?
b) how long it took for the
gum to lose its flavour?
Breath-by-breath analysis of flavour
volatiles in orange juice
Reference samples of each minty compound will be analysed by the
MS for comparison with breath samples.
You will be given the opportunity to have your breath sampled by the
MS while you chew a sweet.
Bearing in mind what we learnt in the sniffing activity, which
compounds do you expect to find in the different sweets?
You will be shown how to interpret the spectra on the screen.
What happens to the level of minty volatiles when the volunteer can
no longer taste the mint flavour of the chewing gum?
What does this tell us about taste-aroma interactions?
Safety:
• The experiments involving sniffing minty aromas use
concentrations similar to those experienced during eating mint
sweets to mimic the olfactory experience, hence the levels are
not hazardous.
• Equally the eating of samples and breath analysis has been
approved as a technique by the ethics committee and is not
considered hazardous. The students will have the opportunity
to have their breath sampled whilst eating mints, but, we will
also have demonstrators available in case they do not want to.
• Please do not take part if you are aware of any existing illness
or medical condition.
• There is no obligation on anyone to take part and you may
withdraw from an experiment at any time.
• If you have any concerns, or you are not sure whether you
wish to take part, please discuss the matter in confidence with
a member of staff.
20
References used
Linforth, R.S.T. (2007) Taste and aroma: Why does chewing gum
lose its flavour? Food Flavour Masterclass, University of Nottingham
Linforth, R.S.T. & Taylor, A.J. (1993) Measurement of volatile release
in the mouth. Food Chem. 48 115
Diagrams
Olfactory: http://winearomas.com/images/nose_diagram.jpg
APCI:
http://en.wikipedia.org/wiki/Atmospheric_pressure_chemical_ionizati
on
Mass Quadrupole: http://www.chm.bris.ac.uk/ms/theory/quadmassspec.html
Menthone & Menthol: Linforth, R.S.T. (2007) Taste and aroma: Why
does chewing gum lose its flavour? Food Flavour Masterclass,
University of Nottingham
Carvone Enantiomers: http://en.wikipedia.org/wiki/Carvone
Breath-By-Breath Analysis of Orange Juice Volatiles: http://wwwwip.nottingham.ac.uk/biosciences/foodsci/flavour/flavour_analyses.p
hp
21
Worm Sense
Not all organisms sense the environment in the same way.
In this session you will:
Explore how worms and other invertebrates sense their environment
Use a microscope to examine external earthworm structures
Investigate ways in which earthworm sensory perception impacts
their behaviour and distribution
Carry out a practical to help scientists determine how earthworms
are distributed in the environment
Do you think earthworms can sense things in their
environment?
How do we know if earthworms can sense things?
What do you think they can sense?
How do you think that earthworms sense things?
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Up Close and Personal
Please don’t touch the specimens with your fingers. Use the forceps
or gloves provided.
Place the worm on a petri dish and then under the microscope. Pour
a little ethanol onto the worm.
Focus using the focusing knob on the side of the microscope. You
may need to move the specimen to view different parts.
Use figure
2 over the page to see if you can find:
the saddle (clittelum),
the saddle pad (tubercula pubertatis) and the
setae (small hairs on each segment that may look like
black spots)
Look carefully at the tip of the head. Compare it with the shapes (a)
–(f) below. Which letter does it look most like?
View from above
View from side
View from above
View from side
Figure 1: Dorsal and lateral views of the tip of the head (prostomium)
23
Figure 2. A typical earthworm (lob worm- Lumbricus terrestris).
The roman numerals show the segment numbers. Not all earthworms
look the same. For example you may not be able to see the male or
female pore on the species that you have.
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OPAL Soil and Earthworm Survey
One person answer questions 1-6 on page 6 of the workbook whilst the
other person digs a hole 20cm x 20cm and 10cm deep (using a spade).
Put the soil from the hole on to a bin liner. Sort carefully through the soil
and remove earthworms gently and put them into a container. Break up any
clumps in the soil. There may be worms inside.
Count any worms you find and decide how many adults and how many
immature worms you have. The immature worms do not have a saddle and
can’t be identified to species level. Record the number of adults and
immature worms in the workbook.
Get a stopwatch. Empty the mustard into a water bottle, replace the lid and
shake to mix thoroughly. Start the stopwatch. Pour the mustard solution
into the pit, time how long it takes to completely drain. If it is less than 3
minutes write the time in your workbook. If it is more than 3 minutes move
on to the next step.
Collect any worms that come up with the mustard and put them into a
separate container. Rinse these worms carefully to get rid of the mustard
water. Don’t mix these worms with the worms from your soil pit.
Count the worms from the mustard water and decide how many adults and
immature worms you have. Write this number in your work book below
where you wrote the time taken for the water to drain.
Test the soil properties by following the instructions on the laminated field
guide (Tasks 7 to 15). Record your results in your workbook.
Identify any adult earthworms you have using the field guide. Ask for help if
you aren’t sure. Don’t forget to measure the length of any adult worms and
write this into the table.
Return any worms to a safe place under some leaves and away from any
mustard. Fill in the hole. Put the grass back on top and stamp down so
there are no traces of you being there.
Make sure all of your observations are recorded in the workbook.
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Further Information and Links
Thank you for coming to the Masterclass! We hope you enjoyed the
day!
For further information on anything you have seen today or details
about studying at the University of Nottingham, please email
[email protected], or go to the project
website at www.nottingham.ac.uk/sop.
For additional information about any of the departments involved in
the Science Outreach Project or today’s event, check out the
following webpages:
School of Biology: www.nottingham.ac.uk/biology
School of Biosciences: www.nottingham.ac.uk/biosciences
OPAL: www.opalexplorenature.org
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