Why is an ice cube rock solid whereas a scoop of Italian gelato is almost liquid like? Even a ‘simple’ popsicle isn’t as tough as a pure water ice cube. Instead you can bite some off rather conveniently. Isn’t that interesting?

We’ve made quite a lot of ice creams already, fairly complex ice creams entailing custards, a super straightforward ice cream via only two ingredientsor an Italian style semifredcarry out. In all instances we’ve type of taken it for granted that the ice cream didn’t turn out rock solid. Part of that is due to the development of air. The ice cream was either made airy by incorporating whipped cream or thanks to the continuous stirring of the ice cream machine. But simply presenting air doesn’t execute the trick. Freezing pure whipped cream will still offer quite a solid icy framework.

You are watching: What are some practical applications of freezing point depression

In comes the importance of sugar (or alcohol) and a phenomenon dubbed the freezing allude depression!

What is freezing allude depression?

The freezing allude depression states that the freezing suggest of a mixture of 2 components is reduced than that of individual components. It requires a solvent (e.g. water) and a solute which you’ll mix through the solvent.

A very prevalent example of this phenomenon in everyday life is salting of the roads in water. Pure water freezes at 0°C. However, by mixing in salt the freezing suggest of this mixture of water and also salt will drop well listed below zero. This is why salt is supplied to save roadways complimentary from ice. Even at temperatures listed below zero tbelow won’t be sheets of ice on the road.

So why is the freezing point of the solvent readjusted by disresolving somepoint else in it? Well, if you just have actually pure water (or any other solvent) these water molecules deserve to organize themselves nice and tight. When the temperature lowers and the water freezes they deserve to create a nice crystal amongst themselves (read even more around phase transitions). However, by mixing in a solute (e.g. salt or sugar) this nicely ordered framework is disturbed. Instead, they might only develop these crystals at a lower temperature. This is what happens bereason of the freezing suggest depression.

The freezing suggest depression in ice cream

In ice cream the freezing point of the water in the ice cream is modified. Water is the major components of many ice cream given that it renders up the majority of of the milk or cream you can be making use of. The freezing point is greatly lowered through the enhancement of sugar. Sugar dissolves in the water and this means interferes via the crystal development.

You could likewise mean the fat in ice cream to affect the freezing point. However before, that is not the case. Water and also oil execute not mix instead little bubbles of oil float roughly in the ice cream, yet they never before interfere in the very same way as sugar does.

Alcohol and also ice cream

In various recipes alcohol is supplied for making ice cream. Acomponent from the flavour and alcohol it contributes to the ice cream it is likewise offered for lowering the freezing suggest of water! Theoretically you might make ice cream without sugar and also simply alcohol, yet, not certain whether that would certainly taste as good…


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Ice cream through plenty of sugar

Calculating the freezing allude depression

You can calculate the adjust in freezing allude of water in ice cream rather easily. The freezing allude depression is a so called colligative residential property. This means that the temperature drop, so how much the freezing point lowers, does not depend on the form of component added, the solute. Instead, it only relies on the number of pposts added and also the original properties of the solvent to which they are included.

In other words, if we would include 10.000 sugar molecules, this would certainly have the same effect on the freezing suggest as 10.000 salt pwrite-ups. Only once the amount of solute becomes exceptionally high the type of solute becomes essential.

Because of this simple connection the freezing point depression deserve to be calculated via a simple formula:

ΔTF= – KF· m ·i

Where:

ΔTF= The readjust in the freezing temperature in°CKF= the cryoscopic constant, this value depends on the solvent you’re looking at, for water it’s 1,853 °C·kg/molm = the molality of the solute, in various other words, the number of pposts per kg of solvent, in mol/kgi = the van ‘t Hoff consistent if your pposts splits in 2 or 3 parts after it’s been added to the solvent you have to take that into account, this is many common for salts. For sugars and the choose which don’t break apart, this consistent is one, for sodium chloride (salt) it’s 2.Calculating the readjust in freezing suggest for ice creamVanilla ice cream

Let’s have actually a look at the change in freezing suggest for an easy vanilla ice cream. This ice cream includes roughly 600g (rough assumption: 300 + 0.65* 300 + 4 * 25) of water and 75g of sugar.

If sugar dissolves in water it will certainly not separation so i in the formula over is 1 and we also know the worth for the cryoscopic continuous of water (1,853 °C·kg/mol).We then need to recognize how many kind of sugar crystals we have. From literature we discovered that 1 mole of sugar molecules weighs 342,3g. As such 75g of sugar is 75 / 342,3 = 0,22 mol. Since we have actually 600g of water, the molality of the sugar is: 0,22 / 0,60 = 0,37 mol/kg.

Now it’s a issue of filling in the formula:

ΔTF= – KF· m ·i = -1,853· 0,37· 1 = -0,68°C

The freezing allude dropped much less than 1 level. This is actually really bit, so this ice cream have the right to be made lot softer by including more sugar.

Soft two-ingredient ice cream

Let’s perform another instance to practice these calculations, currently looking at a super simple 2-ingredient ice cream. This ice cream has 245g water (0,7 * 230 + 0,55 * 150) and 70g sugar (0,45 * 150), for simplicity we’ve rounded of the numbers.

You have the right to usage many the very same numbers as in the previous calculation, yet you’ll need to calculate the molality of sugar for this new ice cream recipe. Using the exact same approach we discover it is: 70 / 342,3 = 0,20 mol and 0,02 / 0,245 = 0,83 mol/kg,

Let’s fill in the formula again:

ΔTF= -KF· m ·i = -1,853· 0,83 · 1 = -1,55°C

Phase diagrams

Just this readjust of freezing allude doesn’t tell the finish ice cream story yet, it’s just the begin. Instead, when you’ve got these brand-new temperatures you should have a look at a phase diagram. In a phase diagram you can view specifically exactly how a lot ice and liquid will certainly be present at each different temperature. This is a little too a lot comprehensive for this article, however luckily there’s a separate article on the topic of phase diagrams for you.

A note on frozen fruits

Ever noticed that frozen fruits frequently aren’t rock solid? Apart from the impact of the fruit’s texture this is additionally because of the freezing allude depression. The fruits contain rather most sugar which proccasion all the water from freezing!


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A video for more explanation

A more standard explacountry can be discovered in this excellent video from the Khan Academy.


Resources

A more in-depth explacountry of the thermodynamics behind the freezing point depression have the right to be found on the websites of:UC Davis&Bristol University.


Great write-up.

You say “If you prefer you have the right to also calculate exactly how a lot ice crystals have actually developed and you deserve to calculate what the new freezing temperature of your sugar solution is. If you like you have the right to even calculate how a lot ice crystals have actually formed and you have the right to calculate what the new freezing temperature of your sugar solution is.” Please tell me more. I guess, I might simply meacertain the temperature of some frozen ice cream to determine the freezing suggest.

For conmessage, I ‘m making home low-calorie ice cream, frozen yogurts, and also sorbets. Over the months the batches are enhancing, but I am bedeviled by ice crystals, had texture after freezing, and excess coldness on the tongue. Pure erythritol was excellent for calories and taste, however yielded tough and also cold product. Presently, I am utilizing a mixture of erythritol and also sucincreased (50% each). It’s much better, yet still as well hard and not creamy. I arrangement to attempt an additional fruit alcohol with even more freezing suggest depression next.


Hello Mark,

Thank you for this fascinating comment and also question. It took me some time to come up with an correct answer, however below it is, I hope it’s advantageous.

To begin via your first question, calculating the concentrations of ice crystals versus sugar solution. This question needs an answer longer than simply a comment so I determined to finish a blog article I had actually been functioning on which talks about this specific topic. Using so-dubbed phase diagrams have the right to tell you more about just how to calculate these values: https://nlinux.org/phase-diagrams.There is also a method to calculate the freezing allude depression of a pure solution. It uses the molality of the sugar (or sugar substitute) to calculate the freezing allude depression. This molality describes the number of molecules in a particular mass. Therefore the more molecules tbelow are and thus the smaller they are, the more reliable they are. Aget, it’s a tiny little bit too a lot for just a comment.

Then there’s your problem using erythritol for ice cream. I have to say that I have actually never used erythritol but I did some digging on the internet. Erythirtrol is a so referred to as sugar alcohol as you might understand. One of the characteristics of erythritol is that it crystallizes even more quickly than consistent sugar, which might be one of the reasons of your hard ice cream. This doesn’t necessarily have actually anything to do through the freezing suggest depression. At the exact same time, erythritrol does have completely different freezing point depression then continual sugar because of the different dimension of the molecule. Maybe this pdf file can assist you: http://www.jungbunzlauer.com/fileadmin/content/_PDF/JBL_AR_Erythritol_makes_a_difference_2015-104.pdf.

Hope that helps and also many thanks for the questions!


Thank you very a lot. I look forward to reading your fascinating write-up and also finding out. It may be a little of an obstacle as I didn’t pay sufficient attention in high school chemisattempt and also was tossed out after I set off a potassium permanganate and also sugar bomb. I guess I have the right to always foracquire my pride and ask my high school kids.

Nonetheless, I thrived to be an epidemiologist and also one day was faced by a hospital where the water system was contaminated through ethylene glycol antifreeze as a result of a cross connection in the pipes. the contamination had happened at night and we required to decide easily if the water was safe to drink and also for the hemodialysis devices (one patient had died during the night as the molecules of ethylene glycol passed the semipermeable membrane.

My team went to the chemistry laboratory wbelow we learned they were unable to meacertain levels of ethylene glycol. the head technology had an principle. He filled a beaker through distilled water and one more via ethylene glycol. He put both in an ice bath and we watched in fascicountry as the water started to ice over and he inserted a thermometer and also it proved 0 C. Soon afterword, the contaminated tap water froze well below 0. Hence, we didn’t permit human being to drink the water.

the hospital toxicologist told us that he air conditioning liquid was marked via uridene green so human being would certainly know if tright here was contamicountry. Alas, he explained that uridene green is a reasonably huge molecule so it didn’t pass the dialysis semipermeable membrane so nobody thought the fluid was contaminated until the patient slipped off into a deep sleep and also passed away.

This was in New York City, where the city lab might test for anypoint and also they provided us via hourly tests as we fluburned out the building, which took about 12 hrs.

Forgive an old male for his stories. Based on the post you attached I have adhered to its referral to usage 1/3 erythritol to 2 parts sucincreased. Erythritol is good stuff. It is took in right into the body, so it doesn’t reason osmotic diarrhea prefer various other sugar alcohols. Also, is cannot be metabolized by the body, so it is excreted unchanged in the urine and also contributes 0 calories to the body. Also, it can’t be metabolized by dental bacteria, so it is not associated through dental caries.

Since my goal is create the lowest possible calorie ice cream, erythritol seems great for the job.

If I may, I’ll let you understand how my freezing point determinations on commercial commodities functions out and also use this as a tarobtain for my home brew ice cream. If I deserve to figure out just how to usage the formula in your posting, I’ll compare this through my speculative results.

Best Wishes,Mark


Hi Paing,

Thank you for coming by! In order to calculate the freezing allude of milk you should use the cryoscopic continuous for water and also then usage the formula to calculate the new freezing suggest. However before, this isn’t right forward given that tright here are both salts and also sugars in milk. You would certainly need to know the concentrations of all solutes in your milk and this varies per breed kind and also the diet of the cow.That shelp, tbelow is rather many published information on the freezing suggest of milk. Generally, the freezing point depression of milk is a little even more than 0,5C (so the brand-new freezing allude is -0.5c). Milk is mainly water with just some salts and sugar, so the lowering of the freezing allude is not that much. This short article might help you additionally.


Thanks you and please answer what’s tha van ‘hof constant for milk? Is that 1 or somepoint else. and you must mentioned this formual outcome of freezing suggest depression have to be in minus,i’m entirely confused via the 0.62 level celsius of freezing allude depression of water added via sugar while original water freezing suggest is 0 degree celsius.need to be Tfi – Tfs = Kf*m*i


Hi Paing,

I added some clarification in the article that will certainly hopecompletely assist you. Adding sugar to water lowers the freezing point by 0.62C. So the new freezing suggest is -0.62C.

There exist no van ‘t Hoff constant for milk. Instead, watch milk as water via solutes such as sugar and also salts dispersed throughout. Use the cryoscopic consistent for water and also then discover the molality and also Van ‘t Hoff consistent for the solutes that are existing in the milk.

Hope that helps!


Hello,

I am assuming sucincreased, yet not milk fat, lowers the freezing suggest of ice cream (around minus 20 degrees C) .

What percentage of sucincreased (or dextrose?) would should be included to otherwise ordinary milk to proccasion it freezing at minus 22 degrees C.Are tright here other food grade additives which have a similar effect?


Hi Pete,

Succlimbed indeed lowers the freezing point, however, it does not reduced the freezing allude of all the water to listed below -22C in the quantities that you’d use in ice cream. Part of the water will still freeze, just not all of it (so the freezing suggest of that staying percent is indeed exceptionally low). I would certainly not understand the precise concentration of sugar forced to prevent any kind of of the milk from freezing, mainly, at this suggest the mixture becomes extremely viscous and various other components in milk (such as the lactose) also affect freezing so it’s not a basic calculation. I would say you’d need >60w% of sugar (so of 100g of ice cream, more than 60% must be sugar), possibilities are your ice cream won’t taste excellent anyeven more and also you can begin having problems disresolving all the sugar in your ice cream mix.Propylene glycol (which is additionally provided in antifreeze, for the very same reason) is likewise a strong freezing point depressor and is enabled to usage in ice cream, though it relies by area how a lot, certainly at much lower concentrations then sugar.

I think our course on ice cream, especially the area on freezing allude depression can help you out also, it includes a couple of more details than questioned in this post.

Hope that helps!Alcohol likewise lowers the freezing suggest, aobtain, it won’t prevent all freezing, just part of it.


Thanks kindly for the response. I am greatly interested in storing milk (or sweetened milk if needs be) at minus 22 C. Such that it remains both palatable and liquid. .However before, 60% w/w succlimbed is most likely to be more thick syrup fairly than liquid. Probably attempting to execute the impossible.


This is so exciting. How perform you regulate to come up with the water content in each. For instance, in the vanilla. I would certainly have actually just assumed it was 300mL x 2 from the milk and also the cream. Wright here did the additional 50g come from and exactly how deserve to I calculate this for my very own batches?

Thanks extremely much! Gonna be nerding out on your website for the longest time.


Hi Tiffany kind of,

Great question (and also I did notification there was a slight error which I adjusted)! The water in the vanilla ice cream recipe originates from three sources: milk (which we’re assuming is 100% water here), cream (65% water) and egg yolks (we’re assuming 25g water each). Do alert that whether you use 600g of water of 650g the distinction in freezing allude is pretty tiny.

If you’re interested in digging deeper, I’d indicate you have a look at our totally free ice cream course as well where we explain this in also more detail!


Thanks for your reply and also clarification. I actually am enrolled in the course. I did desire to double examine yet. If I obtain one question wrong on the quiz it usually doesn’t let me relocate on and it appears as though I have to reexecute the whole thing until I deserve to get to the next section.

I’m not certain if this is the instance or if I’m just having trouble navigating.

Another question though to clarify. Is it true that many ice creams have about 20% sucincreased and some kind of glucose syrup and therefore the freezing suggest depression of commercial items are commonly -18 deg C? Does this intend that up until -18 deg C the icecream will certainly not freeze rock hard choose water?

Thanks again!


Hi Tiffany,

Thanks for flagging your quiz issue! It shouldn’t execute that and permit you to progress even if you didn’t gain every little thing correct. We’ve updated some settings and it have to now work fine.

See more: Use Complete Sentences To Describe Why Postulates Are Helpful.

For your second question, great question and one that needs a long answer!:The freezing allude of your ice cream mix will certainly mostly not be -18C. For it to be so low, you’d need to add way also much sugar. What happens though is that when you freeze ice cream, some of the water in the mix will certainly freeze and also turn into ice. As a outcomes you’re left with ice + sugar solution (aka water + sugar). Since there’s much less water in the solution now, the concentration of sugar has enhanced. As an outcome, the freezing point will certainly be lower. Aobtain, some water will certainly freeze right into ice and also you’re left through an even more focused sugar solution through an even reduced freezing allude.In reality, this doesn’t go in procedures however is a smooth change. It suggests that at the end you’ve gained ice crystals + sugar solution. The sugar solution makes sure the ice cream is still soft. The ice cream harden the ice cream. Balancing the concentration of sugar will certainly encertain you’ve got your right texture at the finish and remember that this deserve to be affected by various other ingredients in the ice cream as well (e.g. alcohol or salt).