All recipes on the blog are broken into three sections: SECTION 1: The Science of Ice Cream Making and Preparation Tips; SECTION 2: Full Recipe; and SECTION 3: Quick Recipe. To avoid repeating SECTION 1 in each recipe post, we’ll be covering it here. We’ll be looking at the importance of producing small ice crystals, maintaining these small ice crystals during storage, and the effect of prolonged heating of the ice cream mix on texture.
1. ICE CRYSTALS IN ICE CREAM
Ice crystal size is a critical factor in the development of smooth and creamy ice cream (Donhowe et al. 1991). Smooth and creamy ice cream requires the majority of ice crystals to be small, around 10 to 20 µm in size. If many crystals are larger than this, the ice cream will be perceived as being coarse or icy (Drewett & Hartel, 2007; Goff & Hartel, 2013). Ice cream is frozen in two stages: dynamic and static freezing. Ice crystals are formed during dynamic freezing, where the ice cream mix is frozen and agitated in an ice cream machine to incorporate air, and grow during static freezing, where the partially frozen ice cream mix is hardened in a freezer without agitation. The primary aim is to promote the formation of as many small ice crystals as possible during dynamic freezing and then preserve these small crystals during static freezing and storage.
1.1. THE DYNAMIC FREEZING STAGE
In the dynamic freezing stage, the ice cream mix enters the ice cream machine slightly above its freezing point (the temperature at which the water in the mix first begins to freeze). As the freezer bowl absorbs the heat in the mix and brings it below its freezing point, a layer of ice freezes to the wall of the cold freezer bowl causing rapid nucleation (the birth of small ice crystals) (Hartel, 2001). The crystals that form at the wall of the cold bowl are then scraped off by the rotating dasher blades and mixed with the warmer mix in the centre of the bowl, where they grow in size.
1.1.1. NUCLEATION
For smooth and creamy ice cream, it’s important to have a high rate of nucleation so as to create as many small ice crystals as possible (Hartel, 1996). Nucleation occurs only at the wall of the freezer bowl where it’s cold enough to form new crystals. Drewett & Hartel (2007) found that decreasing the coolant temperatures at the freezer bowl wall caused higher ice crystal nucleation rates. Similarly, Russell et al. (1999) note that the rate of nucleation is determined by the degree of heat removal from the ice cream mix, which is dependent on the freezer bowl temperature, and found that as the freezer bowl temperature was lowered, the nucleation rate increased accordingly.
1.1.2. RESIDENCE TIME
Residence time (the length of time the ice cream mix spends in your machine) has a significant effect on the final ice crystal size distribution (Russell et al., 1999; Goff & Hartel, 2013; Drewett & Hartel, 2007; Cook & Hartel, 2010). A longer residence time means that the ice cream mix is slower to reach its draw temperature (the temperature at which the ice cream is removed from the machine) of -5 to -6°C (23 to 21.2°F) in commercial machines, which gives the ice crystals in the centre of the freezer bowl more time to recrystallise and grow larger (Russell et al., 1999; Drewett & Hartel, 2007). Russell et al. (1999) found that ice creams made with shorter residence times had smaller ice crystals due to a decline in recrystallisation (the general increase in ice crystal size). Russell et al. (1999) also note that ice crystallisation is dominated by recrystallisation and that this mechanism appears to be more important than nucleation in determining the final crystal population.
The freezer bowl wall temperature has a direct effect on the cooling rate, and therefore the residence time, of the mix (Cook & Hartel, 2010). Lower wall temperatures can lower the bulk temperature of the ice cream faster, reducing residence time and improving the ice crystal size distribution (Russell et al., 1999; Drewett & Hartel, 2007).
Tip #1 – THE FREEZER BOWL WALL TEMPERATURE
To promote rapid nucleation and a shorter residence time, it’s important that your freezer bowl wall temperature falls in the range of -23°C to -29°C (-9.4°F to -20.2°F). If you’re using the Cuisinart ICE 30-BC, or any other machine that requires the freezer bowl to be frozen before use, your freezer’s temperature will have a direct effect on the freezer bowl wall temperature. The colder you can get your freezer, the lower you will get your freezer bowl wall temperature and the higher the rate of nucleation and the shorter the residence time.
When I freeze my Cuisinart ICE-30 bowl, I use the ‘super freeze’ function on my freezer to get the temperature down to around -30°C (-22°F). This results in a freezer bowl wall temperature of -27°C (-16.6°F) and a residence time of 32 minutes for a 700 ml (0.74 quarts) batch of ice cream. This compares to a freezer bowl wall temperature of -15°C (5°F) and a residence time of 38 minutes for a 700 ml (0.74 quarts) batch when my freezer temperature is set to around -18°C (0.4°F).
When freezing your removable bowl, cover the top with cling film. This will help prevent water vapour in your freezer, as well as any ice that may fall in, from freezing to the inside of the bowl. Any water that freezes at the bowl wall will likely be incorporated into your mix during dynamic freezing, with possible implications for texture if a sufficient amount is incorporated.
If you’re using a domestic machine with a self-refrigerating compressor, switch the compressor on and leave the machine running for about 15 minutes before you add the mix. This will ensure that the freezer bowl wall temperature is as low as possible when the mix is added.
Tip #2 – FREEZE YOUR EQUIPMENT
Freeze a 1 litre (1.06 quarts) plastic container and the ice cream dasher overnight. Freezing the plastic container will remove any stored heat. Heat stored in the container causes the ice cream that contacts the side and bottom to melt, resulting in an increase in ice crystal size.
It’s also important to freeze enough water in some ice trays to make an ice bath. We’ll be using an ice bath to quickly cool the ice cream mix once it’s been heated, minimising the time it spends in the ‘danger zone’, between 5°C (41°F) and 65°C (149°F), where bacteria likes to multiply.
1.1.3. DRAW TEMPERATURE
Draw temperature, between -9°C and -12°C (15.8°F and 10.4°F) in domestic machines, refers to the temperature at which ice cream is removed from the freezer bowl once dynamic freezing is complete. Draw temperature has a significant influence on mean ice crystal size (Drewett & Hartel, 2007). In general, a lower draw temperature results in smaller ice crystals (Arbuckle, 1986). Hartel (1996) argues that of all the factors affecting ice crystallisation that can be controlled, the draw temperature of the ice cream freezer bowl is probably the most significant.
To obtain a low draw temperature, the freezer bowl temperature must be as low as possible to give rapid heat removal. Heat transfer must also be as efficient as possible. This means using dasher scraper blades that contact the wall of the freezer bowl as they rotate to prevent a build up of ice. A lower draw temperature also reduces recrystallisation during the static freezing stage as harding times are reduced (Drewett & Hartel, 2007).
Longer residence times are usually required to obtain a lower draw temperature. Koxholt et al. (2000) note that the dynamic freezing step must account for competing phenomena as shorter freezing times are needed to produce small ice crystals, but longer freezing times give smaller air cells and a lower draw temperature.
Tip #3 – PROMOTE EFFICIENT HEAT TRANSFER
If you’re using the Cuisinart ICE-30, you can limit ice build up on the freezer bowl wall, thus promoting efficient heat transfer, by using your thumb to push the dasher firmly against the side of the bowl during dynamic freezing. I’ve used this technique for the past 6 years with my ICE-30 and haven’t had any issues with the added stress that is placed on the motor.
1.2. ICE CRYSTAL GROWTH DURING THE STATIC FREEZING STAGE
No new ice crystals are formed during the static freezing stage but the existing small crystals grow in size until the temperature decreases to -18°C (-0.4°F), or ideally -25°C to -30°C (-13°C to -22°F), to halt this growth. Faster cooling of the partially frozen ice cream during static freezing, therefore, results in smaller ice crystals (Donhowe, 1993; Goff & Hartel 2013).
TIP#4 – FAST COOLING
To promote faster cooling of the partially frozen ice cream during static freezing, place your ice cream at the back of your freezer where it’s coldest. The size of your batch also affects the cooling time, with larger batches usually taking longer to cool to below -18°C (-0.4°F).
1.3. ICE CRYSTAL GROWTH DURING STORAGE
Storage conditions, namely temperature and temperature fluctuations, influence ice recrystallisation and shelf life, with colder storage temperatures better for minimising recrystallisation and extending shelf life. The ideal storage temperature to reduce recrystallisation would be below the glass transition temperature, below about -32°C (-25.6°F) (Goff & Sahagian, 1996; Roos, 2010). Below the glass transition temperature, recrystallisation occurs very slowly, but storage below about -25°C (-13°F) gives a sufficiently slow recrystallisation rate to give extended shelf life (Goff & Hartel, 2013).
Temperature fluctuations due to automated defrost cycles on home freezers contribute to higher rates of recrystallisation during storage. Witting and Smith (1986) showed that ice creams stored in a ‘supermarket-type frost/defrost freezer’ with temperature cycles between -9.4°C and -15°C (15°F and 5°F) became detectably icy in 4 weeks and objectionably icy in 3-10 weeks.
TIP#5 – TEMPERATURE FLUCTUATIONS DURING STORAGE
To minimise recrystallisation during storage, try to minimise temperature fluctuations by reducing the number of times you take your ice cream out of the freezer, leave it out at room temperature, and then re-freeze it. The more times this cycle is repeated, the more recrystallisation is likely to occur. Also, try to limit the time that your tub of ice cream is left at room temperature by returning it to the freezer as soon as you’ve finished scooping.
TIP#6 – DISABLE AUTO DEFROST
If possible, disable the auto defrost setting on your freezer to minimise temperature fluctuations during storage.
2. REDUCTION
For all recipes on the blog, the starting weight of the ice cream mix will be either 1000g or 1200g, with a target reduction of 15% and 13% respectively after heating for 25 minutes at 72°C (162°F). These target reduction figures are to ensure that we have the necessary mix composition after heating. For a recipe with a starting weight of 1200g and a 13% target reduction after 25 minutes heating at 72°C (162°F), you should be left with 1044g of mix after heating. For a recipe with a starting weight of 1000g and a 15% target reduction, you should be left with 850g of mix after heating.
Here is how to check the level of reduction after heating for 25 minutes at 72°C (162°F) of a mix with a starting weight of 1200g:
First weigh your pan and record its weight. My 23cm diameter pan weighs 1606g.
1606g pan + 1200g starting mix = 2806g starting weight.
After 25 minutes of heating, my total weight (1606g pan + 1044g 13% reduced mix) should be around 2650g.
If my total weight after 25 minutes heating is greater than 2650g, I will continue heating until the weight falls to 2650g or less.
3. THE SIZE OF YOUR PAN
The size of the pan you use will affect the rate of evaporation and, therefore, the heating time. I use a large pan with a 23cm diameter, which results in either a 13% or 15% reduction after 25 minutes of heating. If your pan is smaller than 23cm, you’ll likely need to continue heating your mix for a further 2-5 minutes to achieve the target reduction. If you don’t achieve the target reduction, you may be left with too high a water content in your mix, which may result in coarse texture.
4. THE IMPORTANCE OF HEATING TIME AND TEMPERATURE
There are three principal reasons why we’ll be heating our mix to 72°C (162°F) and holding it there for at least 25 minutes: 1. to pasteurise the mix, 2. to improve foaming and emulsification, and 3. to improve body and texture.
4.1. PASTEURISE THE MIX
If you’re running a business and making ice cream to sell, you need to ensure that you are in compliance with food safety legislation. Here in the U.K, the Dairy Products (Hygiene) Regulations 1995, Schedule 6, part v 1 (a) states:
1. Pasteurised ice-cream shall be obtained by the mixture being heated—
- to a temperature of not less than 65.6°C (150.1°F) and retained at that temperature for not less than 30 minutes;
- to a temperature of not less than 71.1°C (160°F) and retained at that temperature for not less than 10 minutes; or
- to a temperature of not less than 79.4°C (174.9°F) and retained at that temperature for not less than 15 seconds.
Ice cream needs to be pasteurised in order to destroy all pathogens and the enzyme phosphatase that may be harmful to health. This is just as important for those of us making ice cream to sell as it is for you guys making ice cream at home.
4.2. IMPROVE FOAMING AND EMULSIFICATION
The second reason we’ll be heating our mix to 72°C (162°F) and holding it there for at least 25 minutes is to improve whey protein foaming and emulsification. Foam formation and its stability is important for texture and for the retention of air that is incorporated into ice cream during dynamic freezing. Heating milk so that the whey proteins undergo partial protein unfolding yields a more voluminous and more stable foam and improves the emulsifying characteristics of the proteins (Philips et al., 1990). Similarly, Damodaran (1996) found that denatured proteins have better foaming properties, attributed to increased hydrophobicity, and greater interfacial contact. Sava et al (2005) found that surface hydrophobicity increased considerably at temperatures between 70°C and 77.5°C ( 158°F and 171.5°F) when whey protein was heated for 45 minutes, with greater increases noted after longer heating times.
Sava et al. (2005) note that thermal denaturation of whey protein involves 2 steps: an unfolding step at 70 to 75°C (158 to 167°F), and an aggregation step at 78 to 82.5°C (172.4 to 180.5°F), that mostly follows unfolding. Phillips et al. (1990) note that foaming and emulsifying characteristics may be impaired if protein undergoes aggregation
4.3. IMPROVE BODY AND TEXTURE
The third reason we’ll be heating our mix to 72°C (162°F) and holding it there for 25 minutes is that heating milk also improves ice cream texture because of the denaturation of proteins and the consequent increase in their water-holding capacity (Goff & Hartel 2013).
TIP#7 – HEATING TIME AND TEMPERATURE
Studies point to an optimal heating temperature for whey protein at somewhere between 70°C (158°F) and 75°C (167°F). In this temperature range, whey proteins undergo reversible unfolding, which improves foaming, emulsification, and texture. Holding whey protein at between 70°C (158°F) and 75°C (167°F) for an extended period of time significantly increases surface hydrophobicity with only a minimal loss of solubility, which improves foaming.
5. WHY IS SKIMMED MILK POWDER ADDED TO ICE CREAM?
Skimmed milk powder’s primary role in ice cream is to increase the milk solids-not-fat (MSNF), namely the protein. Flores & Goff (1999) demonstrated that milk proteins had a large impact on texture by limiting ice crystal size and enhancing their stability.
I hope this helps. I’d love your thoughts on how this post could be improved so do get in touch and say hi! All the best, Ruben 🙂
REFERENCES:
Arbuckle, W.S., 1986. Ice Cream (4th ed). New York: Van Nostrand Reinhold.
Cook, K. L. K., & Hartel, R. W., 2010. Mechanisms of Ice Crystallisation in Ice Cream Production. Comprehensive Reviews in Food Science and Food Safety. 9 (2).
Damodaran, S., 1996. Functional properties. In: Nakai, S., Modler, H.W. (Eds.), Food Proteins – Properties and Characterization. VCH Publisher, New York, pp. 167–234.
Donhowe, D. P., 1993. Ice recrystallization in ice cream and ice milk. Ph.D. thesis, Univ. of Wisconsin-Madison, Madison.
Donhowe, D. P., Hartel R. W., and Bradley R.L., 1991. Determination of ice crystal size distributions in frozen desserts. Journal of Dairy Science. 74.
Donhowe, D. P., and Hartel, R. W., 1996. Recrystallization of ice in ice cream during controlled accelerated storage.Int. Dairy J. 6.
Drewett, E. M., & Hartel, R. W., 2007. Ice crystallisation in a scraped surface freezer. Journal of Food Engineering78(3).
Flores, A. A., & Goff, H. D., 1999. Ice Crystal Size distribution in Dynamically Frozen Model Solutions and Ice Cream as Affected by Stabilzers. Journal of Dairy Science. Volume 82. 7. 1399–1407.
Goff, H. D., and Hartel R. W., 2013. Ice Cream. Seventh Edition. New York Springer.
Goff, H. D., and Sahagian, M. E., 1996. Glass transitions in aqueous carbohydrate solutions and their relevance to frozen food stability. Thermochim Acta. 280:449–464
Hartel, R. W., 1996. Ice crystallisation during the manufacture of ice cream. Trends in Food Science & Technology. 7(10).
Hartel, R. W., 2001. Crystallisation in foods. Gaithersburg, MD: Aspen Publishers.
Koxholt, M., Eisenmann, B., Hinrichs, J., 2000. Effect of process parameters on the structure of ice cream. Eur Dairy Mag. 1.27-30
Phillips, L. G., Schulman, W. and Kinsella, J. E., 1990. pH and heat treatment effects on foaming of whey protein isolate. Journal of Food Science. 55:1116–1119.
Roos, Y. R., 2010. Glass transition temperature its relevance in food processing. Annu Rev Food Sci Technol. 1:469–496
Russell, A. B., Cheney, P. E., & Wantling, S. D., 1999. Influence of freezing conditions on ice crystallisation in ice cream. Journal of Food Engineering. 29.
Sava, N., Rotaru, G. & Hendrickx, M., 2005. Heat-induced changes in solubility and surface hydrophobicity of β-Lactoglobulin. Agroalimentary Processes and Technologies. Volume 11. 1. 41-48.
Wittinger, S. A., and Smith, D. E., 1986. Effect of sweeteners and stabilizers on selected sensory attributes and shelf life of ice cream. J Food Sci. 51(6):1463–1466, 1470.
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Hi Ruben,
I just found your website and I love all of the information and attention to detail. I have one question that I fear is very basic … would using malted milk powder have the same effect as milk powder in stabilizing an ice cream mixture? I realize the flavour would be impacted since the powder is malted but I’m unsure if the texture would also be effected. Thank you in advance for any help you can provide.
Hi there Madison!
Thanks for getting in touch. That’s a good question. Yes I think that using malted milk powder will have the same beneficial effects on ice cream as using skim milk powder and may even be more beneficial if there is malted barley and wheat flour in the malted milk powder. My guess is that, if the malted milk powder does contain malted barley and wheat flour, your ice cream mix is likely to be thicker, which is a good thing to a certain extent, than one that contains skim milk powder. My advice would be to give it a go and see how your ice cream turns out! It would also be a good idea to compare a batch made with malted milk powder to one made with skim milk powder.
Hope that has answered your question. Let me know if you need a hand with anything else.
All the best,
Ruben
Thanks so much Ruben!
Hi Ruben,
Why is it necessary to pasteurise the mix when most cream and milk we buy is already pasteurised?
it increases the ratio of solid vs moisture, you basically reducing the water in the mixture. When you get the ratio right, you end up with better texture & consistency. An ice cream thats creamier. There is a section on the process in the literature that explains it detail, I’m sure Ruben will post a link.
4.2. IMPROVE FOAMING AND EMULSIFICATION
The second reason we’ll be heating our mix to 72°C (162°F) and holding it there for at least 25 minutes is to improve whey protein foaming and emulsification. Foam formation and its stability is important for texture and for the retention of air that is incorporated into ice cream during dynamic freezing. Heating milk so that the whey proteins undergo partial protein unfolding yields a more voluminous and more stable foam and improves the emulsifying characteristics of the proteins (Philips et al., 1990). Similarly, Damodaran (1996) found that denatured proteins have better foaming properties, attributed to increased hydrophobicity, and greater interfacial contact. Sava et al (2005) found that surface hydrophobicity increased considerably at temperatures between 70°C and 77.5°C ( 158°F and 171.5°F) when whey protein was heated for 45 minutes, with greater increases noted after longer heating times.
Sava et al. (2005) note that thermal denaturation of whey protein involves 2 steps: an unfolding step at 70 to 75°C (158 to 167°F), and an aggregation step at 78 to 82.5°C (172.4 to 180.5°F), that mostly follows unfolding. Phillips et al. (1990) note that foaming and emulsifying characteristics may be impaired if protein undergoes aggregation
4.3. IMPROVE BODY AND TEXTURE
The third reason we’ll be heating our mix to 72°C (162°F) and holding it there for 25 minutes is that heating milk also improves ice cream texture because of the denaturation of proteins and the consequent increase in their water-holding capacity (Goff & Hartel 2013).
Hi Ruben. Thank you for this wonderful resource. Since you recommend Jeni’s book, I’m wondering if you have any experience using cream cheese. She seems to be the only one using cream cheese as an ingredient. Do you know the purpose of this? I have a feeling that it might be a short cut for getting some fat and solid content without the use of non-fat milk powder. Do you think that’s correct? Does it serve other purposes? Thank you!
Hi there Julian,
I haven’t tried using cream cheese myself, I use Jeni’s book more for her flavour ideas and ratios than the base mix. Yes I suspect cream cheese is used as a source of fat and protein, the latter you get mainly from skimmed milk powder and is important to stabilise the air that’s incorporated into the mix, and provide body and smooth texture.
I hope that answers your question. Let me know if you need a hand with anything else.
All the best,
Ruben
Hi Ruben,
First i want to thank you for an amazing blog!
I have a question about Reduction.
As far as i can gather the reduction(evaporation) of13-15% is to get the water content down to a level where you don’t rise getting a course texture.
so faced with wanting to prepare the base in a “sous vide” bath @72º, could i modify the milk/skim milk ratio to get to the same water content as i will have virtually no evaporation ?
Thank you
D
Ps would love a copy of your spreadsheet
Hi there Daniel!
Thanks for getting in touch! You could indeed modify the recipe to prepare a batch sous vide. I’ll send you my spreadsheet over shortly with the recipe already modified for sous vide. Do let me know how it turns out if you give it a go.
All the best,
Ruben
Hi Ruben,
I am planning to make ice cream using the sous vide method too. Could you please send me the spreadsheet? Also, how do you calculate the numbers on the excel spreadsheet? I have been trying to figure it out, but it is hard and I may be overthinking. lol. I am from Houston, TX and we may be using heavy cream that has different % of fat.
Hi there Thidarhod!
Thanks for getting in touch. Sure, I’ll send through my spreadsheet shortly. The formulas in the spreadsheet are based on the formulations in Ice Cream by Goff and Hartel. I highly recommend giving that a read if you’re thinking of putting together a spreadsheet.
Hope it helps!
All the best,
Ruben
Hi Ruben! I’m making incredible ice cream thanks to your science! I purchased a sous vide cooker for Christmas. Could you share your updated spreadsheet for sous vide?
Good afternoon Ruben. I must say that I am really enjoying the information that you provide on the website – as well as all of the resource references – simply brilliant!!! I am also curious about preparing this recipe sous vide (the base – without the lemon curd – specifically). Was wondering if you could kindly shoot me the spreadsheet for a sous vide base recipe that would nullify the 15% evaporation step in the process?
Thank you & keep up the great work!
Hi there Anthony,
Thanks for getting in touch and apologies for the delay in getting back to you. The sous-vide spreadsheet is the same as the normal spreadsheet I’ve posted here. The only difference is that the values in cells C18 and G18 will be the same because there won’t be any reduction through evaporation during heating. You may need to stir the mix in a pan over heat to dissolve the solids before you transfer it to your sous vide bag, in which case some water is likely to evaporate and the value in G18 will be different to C18. Does that waffle make sense?
Let me know if you need a hand.
All the best,
Ruben
On reduced or free-of-sugar recipes: Last week I tried substituting a xylitol-erythritol-stevia mix for 1/2 of the sugar in the chocolate ice cream. No one in my family noticed!
So, this week I’m going to try a sugar-free vanilla with your 25 minute base. I’m thinking of using the gum mixture I’ve seen on your site elsewhere–“guar / lambda carrageenan / locust bean gum, at 0.4g, 0.4g, 0.6g per liter” as a way to increase the chances of success. I’m aiming for scoopability and mouth feel that will match the sugared variety. What’s your advice: With or without the gums for my first try?
Hi again Roger!
I’m actually in the process of researching the use of sugar alcohols and intense sweeteners as alternative sweeteners to sucrose. I’ll hopefully be posting my research on the blog in a few weeks.
Why are you considering using a gum mixture? Is it to compensate for the reduction of total solids when you omit sucrose? I’ve found that the effect that the 25 minute heating method has on the proteins and their water-binding capacity produces similar results to gums. My advice will always be to leave gums and stabilisers our of ice cream but try one batch with and one without to compare.
If you’re reducing or omitting sucrose, you will loose total solids as you probably won’t use an equivalent amount of sugar alcohols. This will mean that your mix won’t be as viscous, which may have an adverse effect on the foam phase. The effect that a decrease in sucrose has on viscosity and body is what I’m currently researching but I don’t yet have a clear understanding of these effects. I’ve found the following article helpful and recommend you have a look at it:
Effect of the Sweeteners on the Qualities of Vanilla-Flavored and Yoghurt-Flavored Ice Cream
Hope that helps. Please do keep me updated with your results.
All the best,
Ruben
Hi Ruben I look forward to seeing your research on non sugar sweeteners. I’m now on my 4th batch of our keto friendly ice cream & am having consistently outstanding results. The egg yolk & milk powder along with the pasteurisation process are the secret. As for the xylitol, its easy to work with as it’s sweetness is 1 for 1 with sucrose. Most importantly to us it does not affect blood sugar levels thus not requiring elevated insulin. Something to consider if your research is looking at making a product that is a little friendlier to diabetics. Would be interesting to calculate the GI of our ice cream.
Hi again Marc!
I think that keto-friendly ice cream is certainly an interesting niche worth exploring. Do you just replace sucrose with the same quantity of xylitol in your mix? As xylitol has a lower molecular weight than sucrose, have you found that your ice cream is colder or harder because of the effect on freezing point depression? I’ll send you a message once my research is up on the blog.
All the best,
Ruben
Hi Ruben
I replace sugar with xylitol at a ratio of 1 to 1 as they have the same sweetness.
As you may recall, the problem I had was the ice-cream was refusing to freeze, the xylitol was acting as an anti freeze.
This was remedied by increasing the fats & milk solids in the way of egg yolks & milk powder. The texture and mouth feel is rich, smooth and creamy, all these qualities are very much to my liking, the handful of people who have been my Guinea pigs have been blown away by it. I’d be happy to share my ingredients list & method. But I kind of think you already have it sorted. Never the less, please let me know, I’d be happy to share my experiment with you.
Kind regards.
Marc
It would be great to exchange some ideas when I start experimenting with some sugar-free recipes:)
Hey again Ruben!
Thanks for keeping the blog updated and for sharing your knowledge and experience in ice cream making.
I haven’t posted in a while but never stopped reading and refreshing your blog, anyways I wanna share with you some experiences that I had.
Last time I asked you if I could roast a natural nut paste in the oven, I tried it and it worked. I spreaded the nut paste on a baking sheet and put it in a preheated 180 degrees celsius oven, after a few minutes the paste starts to “rise” and tiny bubbles form on it, then I stirred it and spreaded it evenly again and placed it back into the oven, by the time the brown colour gets darker and you get a nice roasted nut paste with a very wonderful smell.
I also made mint chocolate chip ice cream using your 1000g(15% reduction) base. I read somewhere that in order for the mint to release its flavours it must be blanched to kill its enzymes, I don’t know if 72 degrees celsius is enough to blanch it, so after roughly 20 minutes cooking the base, I used 40 grams of organic mint leaves, weighted them, then washed them down under boiling water for about 3 to 5 seconds and weighted them again to get the water content, I blended it and transferred it straight into the base. I kept cooking it until I reached the target weight after 15% reduction + the weight of the leaves (before washing it).
After aging it overnight I strained it using a sieve to get the excess leaves out. When I churned the base I melted some dark chocolate and drizzled it in tiny strips when the ice cream was almost ready. The result was very smooth, light green coloured ice cream with a very wonderful and interesting flavour, you first taste the refreshing mint and then you feel the chocolate in your mouth, very good, it was finished the next day ;).
Next thing I wanna make is an olive oil ice cream, I wanna do this by adding 60 grams of pure olive oil (we make the olive oil on our own!) to a 850g base (the one that requires 15% reduction), but I’m afraid the texture will be too “waxy” or too heavy because of the high fat content. Do you think adding a small amount of Maltodextrin or increasing the milk powder will help? If so how much Maltodextrin would you add or by how much would you increase the milk powder?
Also wanted to ask something,
Why do you have two formulas with two different reduction percentages? For example one requires 13% and one requires 15%, I understand they produce different amounts of ice cream but If I wanted to get more ice cream wouldn’t I just need to multiply the original recipe by 2? So the 15% reduction should remain the same.
Huge thanks in advance, your blog is awesome and interesting, every day I learn something new.
I arrived here purely by chance and it feels like I hit the jackpot!!
I’m a food writer/photographer (with a Chemistry background) and I’ve been planning for sometime to write a simple book for home ice cream lovers and makers. I’ll certainly be visiting often. You have great material and insight here, thank you for sharing!
Cheers, Miriam
Hi there Miriam!
Thanks for getting in touch! 🙂 Just had a quick look at your site and your pictures look great!
I hope the blog helps. Let me know if you have any questions.
All the best,
Ruben
Not long after writing the question I put to you re my ice cream not setting I had a revelation, Xylitol is a sugar alcohol & in effect an anti freeze. Put my assumption to the test by making a syrup from xylitol & water, put it in the freezer over night & as per my guess, it did NOT freeze.
I’ve made ice creams using xylitol before & they have worked, these were using a custard base. So I will plan a micro batch as an experiment using the same ingredients & adding egg yolks. Your thoughts on when to add the eggs would be appreciated, prior, during or post pasteurization? My gut feeling is that they go in prior & are a part of the pasteurization process.
Many thanks in advance
Marc
Hi there Marc!
Thanks for getting in touch! 🙂 Yes I suspect that Xylitol had a considerable effect on depressing the freezing point with the amount you used, resulting in a slush that refuses to freeze. I also suspect that your total solids content in your mix was low because of the omission of yolks and what looks like a lot of milk. What is the fat content of the cream you used? Try and get the total solids content of your mix (the sugar, fat, not fat-milk-solids, and egg yolks solids) to around 54% after reduction.
I’d recommend adding the egg yolks prior to pasteurisation and heating all the ingredients together. This is important to pasteurise the yolks and also to ensure that the lecithin adsorbs to the fat globules (which I think happens more easily when the globules are warm), which is important for promoting partial coalescence during whipping. I’d also recommend using less Xylitol.
I hope that helps. Let me know if you have any other questions and good luck with your tests.
All the best,
Ruben
Hi Ruben
Thanks for the response.
Unfortunately I have no information on the fat content of the cream, there is no information available on the packaging here in Thailand.
I did run a half batch yesterday with a slightly modified version of one of your recipes using the same quantity of Xylitol as it would be for sugar & included egg yolk & the result was absolutely brilliant.
Next batch I will introduce milk powder.
Once again, thank you for your assistance, & for providing such a wonderful blog.
Marc
Great to hear your batch turned out well! 🙂
Let me know how you get on and good luck!
All the best,
Ruben
Hi Ruben
well its been a few weeks since we last spoke & I had to consume the previous batches of ice cream prior to making another one.
Your advice was precisely on the money I have now replicated a very successful batch of chocolate sugar free ice cream using xylitol.
Flavour & texture is amazing, then there are all of the health benefits of the xylitol & what can be clearly called a keto friendly ice cream.
Kind regards & many thanks
Marc
Hi again Marc!
Great to hear your ice cream turned out well! 🙂 I’m currently researching alternative sweeteners to sucrose so will hopefully be experimenting with some sugar-free recipes soon. I’ll post the recipe for you to see when I’m happy with the results.
All the best,
Ruben
Hi Ruben
Thanks again for your reply.
I highly recommend you investigate Xylitol, it is 1 for 1 sweetness wise with sucrose, but the thing that we like about it is it has many positive health benefits, like it remineralizes your teeth, so it is anti decay & it also feeds the good bacteria in the gut.
Again, your information & advice has been absolutely fantastic, thank you so much.
Marc
Hi Ruben, Thanks for the great tips. I have been using the pasteurization technique described above & have had a strange out come on all occasions. During the dynamic stage it seems to do all the right things though it does not become firm at all, I then put it in the freezer, leave it in there for 2 to 3 days & it is still runny, cream like consistency. The ice cream machine I use is the Cuisinart ICE 100, my dynamic time is around 40 to 50 minutes.
The only thing that I can think that may change the freezing temp of the end product is that I use Xylitol instead of sugar, As I’m trying to make a high fat low carb ice cream.
Do you have any suggestions?
My ingredients are.
500 ml whole milk
500ml cream
100gm cocoa (unsweetened)
185 gm xylitol (substitute for sugar)
1 tsp Vanilla
the flavour is excellent I just cannot get it to set.
Mnay thanks
Hi Ruben!, it’s me again vic from indonesia 🙂 thanks for your information.
do you know the popular ice cream shop in Ohio? they didn’t use egg yolk for the based and used starch for thickening the custard. In your opinion which one is better ?and have you ever tried making that style(egg-less)?
i mean in your opinion which one is better, the egg-less style or the opposite?
thank you
Typo: “1.1. THE DYNAMC FREEZING STAGE”
Cheers Steve! 🙂
Hi Ruben
Firstly thank for sharing your depth knowledge about ice cream making with us and I found these topics very very important as well as knowledgeable.
This is Dhruvil Patel from INDIA. I am trying for setting up my own ice cream parlour and for the same I taking trials of various compositions since few months. I would like to mention here that I am using liquid nitrogen to prepare the same.
My problem is though while eating ice cream it tastes so smooth, soft, creamy and not at all icy, upon freezing (in home refrigerator’s deep freezer) for about 10 days it remains equally soft and smooth but it melts so quickly.
Here is the ratios I m maintaining
Fat – >12%
Total solids = 37-40 %
MSNF = 10.47%
And I m using following ingredients for 500 GM preparations.
Milk – 330 ml (6% fat)
Cream – 80 GM(min. 50% fat)
SMP – 11 GM
Emulsifier and stabilizer (CMC+GSM) – 1/4 TBSP
SUGAR – 75 GM
Can you pl. Confirm or suggest where exactly correction is required?
Pl. Note I m not considering reduction %.
With kind regards,
Dhruvil patel
Hi there Dhruvil!
Thanks for getting in touch and a big hello to you in India! I suspect that because you’re using liquid nitrogen, your ice cream has low overrun and larger air cells, which both contribute to a higher melting rate. Which machine are you using to mix the ice cream and liquid nitrogen? If you’re using something like a Kitchenaid, you could try increasing the dasher speed to try and produce a higher shear rate and smaller air cells. You could also try increasing the fat content in your mix as ice cream with a higher fat content tend to melt more slowly.
You could also try increasing the amount of emulsifier you use to try and increase the rate of partial coalescence of the fat globules during the whipping stage, which contributes to slower meltdown rates. You could also try increasing the viscosity of your mix by increasing the amount of stabiliser or increasing the total solids. Don’t increase the sugar too much though as this will depress the freezing point and contribute to faster meltdown rates.
If you haven’t already done so, I’d recommend having a read through my Why does ice cream melt? post.
I hope that helps. Let me know if you have any other questions.
All the best,
Ruben