Hello, and welcome to this festive edition of
the Physics World Weekly podcast.
I'm Hamish Johnston.
December might be dark and chilly
here in the northern hemisphere,
but it's summer south of the equator.
And for many people, that means eating ice
cream.
And it turns out that the physics of
ice cream is rather remarkable.
As I discovered when I traveled to Canada's
University of Guelph, and met a leading expert
on the science of frozen desserts.
Here is that conversation
with the food scientist,
Douglas Gough.
Hi, Doug. Welcome to the podcast.
Hi, Hamish. It's a pleasure to be here.
And, yeah, I'm really looking forward to, to
talking about ice cream with you. And, I
have to say for the benefit of our
listeners, it is October
in Ontario but it is an ice cream
day out there. It's absolutely beautiful
outside, and I'm so pleased that I've come
up to the University of Guelph.
So
the first question, and I suppose Doug this
is a question for all our listeners who
are physicists,
how would you describe the material properties of
ice cream to a physicist?
Is it a solid for example? Is it
crystalline?
Is it amorphous or maybe a bit of
both?
Is its melting point
0 degrees celsius? What what what is ice
cream from a materials point of view? Well
the
the the first
part of the response would have to be
to say that it's a very complicated system.
It's really all about surfaces.
And so I think when we talk about
the physics,
we're talking about mostly the particles
that would be present in it. And believe
me, there's lots of particles there. So it's
a multiphase
system.
It starts off being an emulsion. So we
have the fat, which is emulsified
into the water phase, the aqueous phase.
So we start off with an emulsion
and then
in the manufacturing
of ice cream, we whip the emulsion
to incorporate an air phase into it. So
in a frozen tub of ice cream, about
half of the volume is air,
but that air is present in the form
of of tiny bubbles that are distributed through
the the product.
And then we partially freeze the aqueous phase
and turn
at least half or 3 quarters of the
water into ice crystals.
And we do that in such a way
that, again, we end up with microscopically
small ice crystals
distributed
it in that unfrozen phase.
And the unfrozen phase is the part that
makes it soft and scoopable and chewable,
and it remains
unfrozen as a solvent because of all the
sugar that's dissolved in it, which acts as
a solute,
depresses the freezing point according to Raoult's law.
So you end up with this multi phase
system that is,
fat droplets in the form of an emulsion,
air bubbles in the form of a foam,
and a partially
crystalline
solvent in the form of ice crystals
and a freeze concentrated
sugar solution
that remains unfrozen because of Raoult's law. So
it really becomes a very complicated system.
Right.
And and so if you were to do
some sort of, I don't know, let's say
neutron scattering
study of ice cream,
would you, would there be a characteristic
length
in there? You know, the separation
between
areas of of different phases? Or is it
all sort
of I'm just trying to get an idea
of the microscopic.
Right. So
we've done a lot of
electron microscopy research in my lab. In fact,
I have to go back to my early
days and say, you know, our research was
some of the very first that was, that
utilized electron microscopy techniques for looking at the
structure of ice cream.
So our fat droplets would be in the
order of about 1 micrometre in size after
homogenization.
Air bubbles, again, depending on the equipment that's
used, would be in the order of 20
to 30 microns in size.
And
ice crystals start off in that
10 to 20 micrometre
in size range.
But
one of the things that happens to both
the air phase and the ice phase over
time is is some recrystallization,
austral ripening and so on.
So it's not uncommon to find ice crystals
up into the 30, 40 micron size.
And
then, you know, when you think about all
that surface area, of course, that
that unfrozen phase remains, you know, distributed around
all of that and so we end up
with these lamellae kind of plateau borders that
can be on the order of again
microns in size.
So it's a it really is a beautiful
thing to look at under an electron microscope
depending on the technique that you use
And we might chat about our techniques a
little later.
But that's typically where we're going to see
all 4 phases: the ice, the air, the
fat, and the unfrozen phase. Right, I see.
So it sounds like ice cream is a
really complex and and beautiful
material.
Is it very difficult to make?
Is it hard to make ice cream when
if I were to set it in my
kitchen to make it, would I be hopeless
at it? Or is it a fairly simple
process? Well,
it it can be a very simple process
right through to being at the commercial scale,
of course, a very
large industrial process
that does become very complicated when you think
about all the equipment involved.
So if I just break it down, we
have the mix making
step, which would be the combination of our
liquid ingredients and dry sugars and stabilizer and
so on to make a liquid mix.
Commercially, that would be pasteurized
to heat it for food safety reasons and
then homogenized
to distribute the fat.
If you were making it at home in
the kitchen, you'd combine your milk and cream
and sugar and and, you know, whisk that
probably heat it
on the stove.
But it wouldn't be homogenized
because you would typically be using homogenized cream
to make it with and so that would
be the homogenization
step.
So we make our mix
and then the mix is whipped and frozen
in that
concomitant
process that becomes the ice cream maker.
So again you can buy kitchen gadgets that
will make ice cream. You can do it
quite simply by just shaking and stirring. We
have some things that we do with kids
where they,
put a small amount of mix in a
ziplock bag and put that in a bigger
ziplock bag with salt and ice and just
shake the heck out of it for for
10, 15 minutes
and you can start freezing it up. So
it can be as simple as that, but
if you were to walk into a big
commercial factory, you'd see equipment that you know
is running at 1,000 of liters per hour
And,
yeah, a lot of engineering that goes into
to to designing that structure.
Making sure the ice crystals are small and
the air bubbles are small and well distributed.
So,
I would say, you know, at the kitchen
level it could be quite simple.
But if you try to extrapolate
that to a commercial scale, then yeah, that
scale up becomes very complicated. I suppose the
mixing bit is the thing, you know, when
people think of my of making ice cream
they think of you have to keep mixing
it. So is that to make sure that
the ice crystals don't get too big? Yes.
Is that the key there?
And the incorporation of the air phase.
So in that,
in that
freezing and whipping that happens at the same
time, whether it be in your ice cream
maker in the kitchen or commercially,
air is being injected.
So air is being whipped from the headspace
or air is being injected into it And
the
the dasher, the whipping action is incorporating the
air to make that small. So that's our
foaming step. But at the same time,
the ice is freezing and you want to
do that under that very rapid dynamic condition
so you keep the ice crystals very small.
I see. So again, your big commercial equipment
would be designed, it would be a scrape
surface type freezer
designed with high high rate of shear in
the barrel
and a high rate of heat transfer in
order
to to to pull the heat out, create
those ice crystals, but under that dynamic condition
to keep them really small. I see. And
the biggest difference between what you do in
the kitchen and what they're going to do
in the factory
is the structure of what you create.
Homemade ice cream is fine for maybe a
day or 2, but it's gonna get start
getting pretty icy pretty quick.
Whereas we want shelf life of
months to a year when ice cream is
made commercially.
And I wanted to ask you about that
sort of degradation process. I mean we all
sort of we defrost our freezers and we
find that ice cream that we bought last
summer, they go, I'm gonna have some, open
up the the container and it's
it's all ice. How
how does that happen?
Is it a very slow phase transition that
occurs within the the ice cream?
It's totally dependent on temperature
and so I just have to describe what
happens when you warm ice cream up a
little bit. Again, go back to Raoult's law
and that freeze concentration of that unfrozen phase.
So if ice cream warms up during its
storage time,
ice is melting in order to maintain that
equilibrium
freezing curve, that balance between solvent and and,
solution.
So that
when the temperature would be lowered again, now
you are freezing more water back into the
ice phase,
but it doesn't create new ice crystals. It
just grows onto existing ice crystals.
So if during the storage time of ice
cream, it's subject to temperature fluctuation,
it's gonna degrade much quicker
than if it was stored at constant temperature.
And likewise, the warmer the temperature,
the faster that rate of recrystallization
process is gonna
be. So we talk about recrystallization.
It can happen at constant temperature, a bit
of Ostwald ripening, but it's very, very slow.
The biggest thing that that exacerbates recrystallization
or the growth of ice crystals is temperature
abuse.
I see. And so you you mentioned that
commercial ice creams can be stored for a
very long time. Is that just because they've
got very very good freezers that maintain
an exact temperature or is there something else
that they can do to the to the
ice cream to stop it? So I'd have
to say there's maybe again 3 different things
I want to comment on there. That yes,
low and constant
temperature storage is what everybody strives for. And
so the lower the temperature and the more
constant it is, then the longer your shelf
life before changes start occurring.
There's another
element that comes into that and that's that
as part of the structure of ice cream,
when that
unfrozen phase
gets concentrated
enough
it goes through a glass transition.
And so that that what we consider that
unfrozen phase that makes it soft and scoopable
when it's warm enough,
if it undergoes a glass transition and itself
becomes an amorphous solid,
then there will be no movement of water,
no movement of of solute within the system,
and it can be it can remain,
you know,
unchanged for years.
And that glass transition temperature is around
-twenty 8 to -thirty 2 degrees C.
So if you want long term storage
you have to get down below that
that tg that glass transition. Is that reasonable
from a cost point of view? Well, it's
expensive. You're right. We maintain a storage freezer
here at the university,
about minus 32 degrees.
And
we had ice cream that went in there
just before the pandemic and then,
of course it was 2 or 3 years
before we got back to it again.
And it was it was just as good
as the day it was manufactured.
So you know when people say to me,
what's the shelf life of ice cream? I
say, well what's the temperature? Because
it can be 2 or 3
years or it can be 2 or 3
days if you start getting up into those
abusive temperature conditions. Right. And and what about
the opposite? I mean I would imagine for
ice cream
manufacturers
there's always
a danger that somewhere in their supply
chain the temperature will go up Yes. And
that could cause them a problem. Is there
anything that that they can do to
ensure stability of their ice cream at high
temperatures, you know, just to guarantee?
Right. And that so that brings me to
point number 3,
And that's that,
the addition of stabilizers
to to an ice cream formulation.
Those are things like locust bean gum, guar
gum,
cellulose gum,
and there are some novel ones as well.
Well. And what those do is to increase
the viscosity in that unfrozen phase. And so
it slows down the rate of ice recrystallization
just because of a very viscous system
that then,
has an impact on on diffusion,
of of water
and, growth of ice.
So,
if you compare an unstabilized
ice cream to one that would contain guar
gum, for example,
the guar would give you
a much
slower rate of recrystallization
and longer shelf life.
There are some other novel
ice recrystallization
inhibition agents.
One of them is propylene glycolmonosteriate,
and it is really unique in that it
can adsorb onto the surface of an ice
crystal very much the same way that these
ice structuring proteins do, or the antifreeze proteins
in nature. And and,
really block the growth of of ice crystals
and keep them very very small.
So for commercial
recipes that need
long shelf life in the presence of potential
temperature abuse,
there are some special agents that they can
add to the to the recipe to try
to give them that longer shelf life. Right.
So so these
those would be natural antifreezes. I mean, try
imagining a fish that lives in very cold
water.
It might have something in its body that
prevents it from freezing. Yeah, and that's again
a very very interesting subject. And
and both both insects and fish and plants,
they all have means of controlling,
the the development of ice that could be
harmful to tissue structures.
And and what we typically say is antifreeze,
there are,
agents certainly that prevent the formation of ice.
But in many cases it's actually anti growth
that a lot of fish swim around with
minute ice crystals in their,
in their body tissues.
But these
these, types of of ice structuring proteins prevent
those ice crystals from getting big enough to
cause harm.
So it could be antifreeze or it could
be antigrowth.
Right. And it's really,
what we want in ice cream is the
is to prevent the growth. You don't want
to prevent the formation of ice because that's
a given. What
we want is to prevent those ice crystals
from growing. I see. And what you
talked about sort of the basic ingredients of
ice cream, but of course today you can
get lots of different flavours. I mean when
you start putting
chocolate or coffee or maybe fruit juice
into your ice cream, do those
additions change
the nature of how you, so would you
have to make a strawberry ice cream in
a different way to a chocolate ice cream
to accommodate
the the chemical and physical properties of the
flavouring? Again, very good question. And
because when you think about ice cream around
the world, there are literally 100 and 100
of different flavors.
And so the biggest question is
is that flavoring
either material
or or
flavor addition itself,
is that impacting
on the
the nature of the solution
or emulsion that's in there? For example, a
chocolate chip. It's going to be totally inert.
It's not going to interact
at all with the rest of the matrix.
So no problem to throw something like chocolate
chips or nuts or something that would be
totally inert.
Nuts might be a little difficult because if
they start absorbing water,
changes the balance of the things that are
in that unfrozen phase.
Strawberries
would be a good example of really impacting
on the system
because of the high sugar content that's in
the fruit preparation.
We need to add sugar to the fruit
to make sure the fruit is softer than
the ice cream itself. You don't wanna bite
into ice cream and have a hard frozen
berry in there.
So most of the fruit would be sugared.
Now the problem is that some of that
sugar is gonna diffuse
into
the unfrozen phase
and lower the freezing point of it. So
if you don't do anything to the formulation,
then strawberry ice cream would be softer
overall than something like vanilla,
because of
the the addition of sugar,
that comes with the fruit.
So if scooping,
for example, is one of the things that's
critical for your operation,
as it would be for, you know, people
running the scoop shop, then they might have
to make a base mix for their fruit
flavors that had less sugar in it
to offset the sugar that would come from
the fruit and give you the same level
of scoopability once it went into the freezer
cabinet.
I see. And are there any additives,
well additives that's a sort of a harsh
word, any you know sort of flavors
or
stuff I suppose that you can that you
that people have tried to put into ice
cream but
it just doesn't work for whatever reason. You
can't make a, I don't know, pineapple ice
cream for you know various reasons. Or can
you make ice cream with any flavour? Well
I think you can try to make ice
cream with just about anything. The question is
whether anybody's gonna
either buy it once or more importantly buy
it twice. You know, they might buy it
once to try it.
So gosh, we've seen everything from, you know,
hot jalapeno peppers and, you know, that kind
of a thing to to the
the floral fragrant flavors and, you know, the
alcohol based flavors. So that would be a
good example. You think of anything from rum
to
to,
Bailey's Irish cream or or Frangelico
or any of those. They're very very popular.
Wine based and beer based flavors.
Very popular. But the alcohol is going to
depress the freezing point. And you're going to
get to the point where,
you know, if you added enough alcohol to
give you the flavor intensity that you want,
then your product wouldn't freeze.
So in that case, you might need to
add less of the alcohol and a little
bit more of like a flavouring, a dealkalized
flavouring
to get both the flavour combination
and,
and having some real,
you know, bourbon in there or whatever the
the case is.
So
I would say you can try to make
ice cream with just about any flavor but
you you certainly have to look at what
that flavouring is going to do to the
structure and
the things like shelf life and balance and
so on that that would be present in
there. Right. And I suppose in in standard
ice cream it is made for milk,
but I'm guessing that you can buy vegan
ice cream these days. Was was that very
difficult to do to make an ice cream
that didn't have any cream in it. Right,
is that hard?
So a lot of it is going to
be pretty similar because we're going to have
an emulsified fat source. Typically it,
would be something like coconut oil or palm
kernel oil.
I didn't really mention that when I talked
about the structure of ice cream, but that
fat
itself has to be crystalline.
If it was liquid oil at the time
of of the
whipping process,
then the oil would coalesce and separate out.
And so our fat phase is also crystalline.
I failed to mention that when I was
talking about structure.
So that means that you're limited to the
type of fat that can go in there.
It really has to be a solid crystalline
fat. So you've got, you know, your fat
phase. You've got of course all the sugar
and stabilizer and so on that you would
have in a normal ice cream.
The difference is the protein.
So if we take away milk protein, milk
protein by the way is both a very
good foaming agent and a very good emulsifying
agent, then we need to replace the functionality
of the protein.
And plant proteins aren't very good
foaming agents,
or emulsifying agents.
Eggs are, but again they are not
vegan. So if you start looking at these
cashew or almond or soy based products, you'll
often find on the ingredient list some ingredients
that are in there to deliver that functionality
that we would have gotten from the milk
protein.
So I think that the big considerations
are going to be flavour and texture that
are coming from the plant source itself,
but then
the delivery of the functionality that you need
to make a you know a good product.
I see. And
what about
desserts like
gelato
and sorbet?
Are they ice creams or are they
similar to ice creams? Are they made in
roughly the same way? Are they completely different?
More similar than different I would have to
say.
Gelato doesn't really have
a standard of identity as such. It's really
just Italian style ice cream. So there's some
unique
things about it that make it a little
bit different. Typically lower in fat and higher
in sugar compared to a standard ice cream
recipe. And that gives it more of that
soft sticky texture that you typically get from
a gelato.
Typically, it's not hard,
hardened or hard frozen the way an ice
cream would be. And so it can be,
you know, paddled rather than scooped kind of
thing.
Sorbet is,
has no dairy in it at all.
Typically just fruit juice, sugar,
and water. And,
it's so it's it's whipped and frozen. So
you have the ice phase and you have
the
ice crystal, ice crystals in the air phase,
but you don't typically have any fat in
there.
And because you don't have any protein neither,
it makes it very hard to get much
air incorporated into it. So sorbets can be
really good but they're they're tricky to make
on a commercial scale just because the overrun
needs to be or the air content needs
to be quite low. I see. And Doug
you mentioned earlier
electron microscopy.
Can you talk a bit about the techniques
that you use to study ice creams?
I mean is it I would have naively
thought that your electron beam would melt
your ice cream,
but maybe that isn't the case. How do
you so maybe if you could first talk
about electron?
So I would say the work courses of
of instrumentation for research, not necessarily at the
factory level, but for research
would be particle size analysis.
So laser light scattering, and that's gonna tell
you everything you need to know about your
your fat globules and fat structure.
Then we do use a lot of microscopy
techniques. Light microscopy,
with a cold stage. That's the critical
part there. So you either need to put
your microscope in a freezer
or in a cold box with a with,
you know, gloves to to use it, or
have a cold stage where you mount your
your ice cream on a slide
inside of a chamber with with that's cooled
with with liquid nitrogen.
So,
on the
electron microscopy side we've done we've done a
lot of cryo
scanning electron microscopy.
So having a
a low temperature unit on the SEM.
And we've also done a lot of transmission
electron microscopy.
And there the technique is to fix the
sample with some sort of a of a
fixative
and then dry it.
Critical point drying typically.
Then you can thin section it and and
look at it with a transmission electron microscope.
Now there are some cryo TEM instruments available
as well, but we're talking, you know, the
real high end of technology.
But cryo SEM and
then TEM with cryo fixation,
would both be excellent techniques. Or light microscopy
with the cold stage for examining the structural
elements that are there.
And then rheology. Of course, we do a
tremendous amount of rheology.
Both
small deformation rheology. Looking at things like mix
viscoelasticity,
G prime, G double prime and so on.
And then,
large deformation rheology.
Things like a instrailing machine where you're going
to measure force deformation
sorts of and that's going to give you
an idea of hardness
measurements on on the ice cream.
So I would that would be the the
toolkit would be particle size analysis, rheology, and
microscopy. I see. And what about computational techniques?
Are there some sophisticated
computer models of ice cream out there? There
have been some papers published.
It's not really an area that,
I don't think is going to really get
us very far, to be honest.
Is it just too complicated of a system?
Yeah. It is. Just too complicated of a
system to to try to model it.
And then and then to get anything meaningful
out of your model that you could relate
back to, you know, to something that would
happen in the factory.
There might be computational
design,
utilized in the engineering of some of the
equipment particularly,
looking at the barrel freezers, the scrape surface
heat exchangers.
So if you went to some of the
big global suppliers of equipment, you might find
them
trying to do design work
of,
you know, things like residence time and residence
distribution
inside their equipment,
that would be an example I think where
you'd find some some more
design work happening. Right. And so what are
the the hot topics at the moment,
you know in in the academic
study of ice cream? What
what are you interested in, you and your
colleagues?
For a long time we focused on ice
cream structure and understanding,
ingredient functionality.
And so both
things like like emulsifier functionality,
stabilizer functionality,
protein functionality,
to try to understand,
you know, if changes were made in formulations,
what impact were they gonna have on structure.
And then
shelf life is kind of the extension of
structure.
So but I would have to say if
you look at it from an industrial perspective,
the biggest concern of of manufacturers is food
safety and and eliminating pathogenic
presence. So
so pathogen control.
Gosh that that field has evolved
so much in the last few years in
terms of our ability
to understand sanitation and hygiene and prevent contamination.
So I would say that probably
keeps people awake at night more than anything
else.
Besides that,
we talked a little bit about the health
conscious formulations. So sugar reduction is a is
a big one right now,
more so than fat reduction, I think.
But it's interesting, I would say, when I
look at those sort of healthier for you
formulations,
there's a lot of them out there. They
don't have a lot of market share, to
be honest, because
most consumers
really say, you know, don't mess with my
ice cream. I'll eat a good diet all
week long, but at the end of the
week, I just want a nice bowl of
ice cream. So I'm not gonna worry about
the fat or the sugar content. I'm just
going to enjoy it. So we really have
to remember that for many people it is
an indulgent treat. That's that's where it exists
in in the whole scheme of their food
diet.
And
so I think just maintaining that that positioning.
And in terms of health, I would I
would rather suggest to people that they eat
a smaller portion
of a really good product
than a bigger portion of something in which
that would have lower fat. You know, just
portion control.
And again, you see a lot of that
in some of the new novelty,
ice cream products. For example, ice cream bars.
They're a little bit smaller in size.
And so again, really good gourmet bar,
real good ice cream,
a real good chocolate on it, but just
a smaller size. And that way, you're you're
watching your fat and sugar intake. Right. Yeah.
I'm thinking of, the Magnum Mini in the
UK,
which is what we like right because I
mean the magnums
themselves are just over the top but yeah
the Mini is nice.
So Doug we're here at the University of
Guelph which
started out as
the Ontario Veterinary College
and the Ontario Agricultural College.
And I think at the OAC,
there has been a course
running
in ice cream
studies or technology for over a 100 years?
Yes. Is that right? Can you can you
tell us something about that course? Our so
we teach an,
an annual
1 week course
for industry people. This ice cream technology course.
And we started teaching that in that's the
collective we, not me, in 1914.
Here's an interesting fun fact.
In a 110
years,
there's only been 4 instructors of the course.
I've taught the course now for,
36 years,
And my predecessor
taught it for 34 years.
And the gentleman before him taught it for
30 years.
So,
it's amazing
that that sense of of longevity
of of the instructors.
So we get on average about 50 people
a year that come from around the world,
to the University of Guelph. And so it's
very much a science and technology
focused course
on
formulations,
ingredients,
processing
and quality issues. So that would be how
I would divide up the curriculum.
Some people arrive and they think, you know,
wow, can we fill 5 days? And then
at the end of it, they go, wow,
I think we need another 5 days. Because,
it it really at that when you start
moving from the kitchen or the artisanal shop
level to to scale up, you realize, well
it's a very complicated product to make and
we've got lots of potential things that can
go wrong.
And when things go wrong, it can cost,
you know, 1,000,000 of dollars.
So there certainly needs to be great attention
to quality.
And and the people that, that come to
to take the course, are these people who
are developing new
ice cream products? Or are they the people
who run
the factories where the ice cream is made
or is it sort of a mix?
It's a mix. So we get,
from the from the
processing side we get, both processing operations people
and research and development people
and quality assurance people. So
so that quality processing and and product development
side is is all covered.
We get some
inspectors, for example, government agency people that would
come that that need to know more about,
how ice cream is made so that they
can, you know, effectively do inspections and certifications.
We get people from the supplier industries.
For example, people that process strawberries that need
to know, well, how is it going to
behave when it goes into ice cream?
So the the ingredient suppliers
would be flavoring people or stabilizer
suppliers
or
milk protein companies, for example.
So the supplier people, the inspector people, but
largely people from the industry. I see and
is it hands on? Do you have a
kitchen and do you have facilities
similar to that in industry where people can
can actually have a go themselves? Yes we
have a full scale pilot plant here at
the University,
with with
the kind of equipment that you'd find commercially,
a little bit smaller in scale.
But our commercial
our ice cream freezer in the pilot plant
can run at 700 liters an hour.
So it's certainly
scalable to to an industry setting.
And we do spend,
a couple of days in the pilot plan.
We also,
do a lot of tasting and evaluations.
We we before the course begins, we make
a lot of products with different levels of
fat, for example, different levels of sugar, different
types of sugar so that people can not
only hear about it in the classroom, but
but we can show them this is what
happens when you modify the formulation in in
these particular ways. I see. And final question
Doug, I'm sure you get this all the
time but I'm I don't think they'd let
me back to physics world if I didn't
ask you: what's your favourite flavor of ice
cream and why?
Well again I have two answers to that.
If if, if I put my professional hat
on it's it's vanilla
and the and the reason why is that
it gives you the the best opportunity to
really evaluate the quality of the ice cream
itself. It's not masked by anything else.
So the flavour that's gonna be there other
than the little hint of vanilla flavouring, but
the flavour is really going to show
how the mix itself,
the ingredients of the mix. So if there's
any particular
off note, you're going to detect that. As
soon as you throw Smarties into it or
chocolate or, you know, butterscotch, it's going to
cover that up. So we always evaluate vanilla
ice creams because it's it's the closest to
the flavor and structure of the ice cream
itself without being masked by anything else.
If I take my professional hat off and
put my my,
fun hat on,
then when I go to an ice cream
shop, I I look for something that I've
never had before, and I would buy that
just to try it to add to my,
you know, collection of stories.
And for example,
my last trip over to Ireland, I found
a fig and blue cheese ice cream. And
I thought to myself,
I don't think I've ever had blue cheese
in an ice cream before, so that's what
I wanna try.
We've had lots of rancid flavors in ice
cream that didn't belong there. But when you
think about actually trying to add blue cheese
to ice cream, you've got wow. That's a
flavor. Did it work?
Well you have to like blue cheese, but
it it did if you're given that caveat.
Right.
And and all this, you know, decades of
work that you've done on ice cream,
do your eyes still light up when you
go into
an ice cream parlor that you've never been
to before? Are you still excited about it?
Oh absolutely.
I've, you know, I've been fortunate enough to
have traveled to many many interesting countries and
and always see what the ice cream market
looks like when I'm there,
either in the grocery store or visit to
an ice cream parlor or a scoop shop
somewhere.
I I enjoy it. I mean, it's not
just a professional thing. I I also like
to know what's going on around the world
so I can share that with with people.
But of course, it's how can you go
wrong with ice cream? It's such a fun
product to be associated with.
That's a great way to end the interview,
Doug. Thanks a lot. Oh, you're most welcome.
It's been fun.
I'm afraid that's all the time we have
for this week's podcast.
Thanks to Douglas Gough for joining me today.
And a special thanks to our producer, Fred
Ailes.
This is the last Physics World Weekly podcast
of 2024.
And I would like to thank all of
the fascinating guests who shared their passions for
physics with us this year
and to our many listeners
for tuning in throughout the year.
Looking to the future,
2025
is the international
year of quantum science and technology
as proclaimed
by the United Nations.
So you can look forward to lots of
quantum coverage in the podcast
next year.
And that kicks off with a conversation
with a physicist
who's developing
new platforms
for quantum
communications.
That's coming up in January.
Until then,
goodbye from the Physics World Weekly podcast.