Roasted Almond Ice Cream – Recipe
For this recipe, I use a fine roasted almond paste from http://whynutshop.co.uk/. Whynut is a small artisanal company, based in the UK, that focuses on making fine nut pastes and nuts from Turkey. They sell pastes in 110g pots, which is perfect for 1 litre of ice cream. They won a Great Taste Award for their Lightly Salted Antep Pistachios, which is great to see.
This recipe makes an extremely smooth and creamy ice cream with a nice roasted almond flavour.
Ingredients: organic cream, organic semi-skimmed milk, organic un-refined sugar, organic free-range eggs, roasted almond paste.
If you are using cream at 36% fat:
Semi-skimmed milk 413g
Egg yolks 72g
Roasted Almond Paste 110g
If you are using cream at 38% fat:
Semi-skimmed milk 440g
Egg yolks 72g
Roasted Almond Paste 110g
If you are using cream at 50.5% fat:
Semi-skimmed milk 555g
Egg yolks 72g
Roasted Almond Paste 110g
The tables below show the composition of the ice cream mix before and after heating. The totals are expressed as a percentage of the mix.
Composition of the mix before it has been heated
Composition of the mix after it has been heated
1. Freezing the freezer bowl
For this recipe, I use the Cuisinart ICE-30 which comes with a large 2 litre bowl. I have used this machine for a very long time and would highly recommend it. The day before you start making your ice cream, take the removable bowl and cover the top with cling film; use an elastic band to help keep it in place.
Put the bowl in a plastic bag and tie the ends. The plastic bag and cling film will help prevent water from freezing to the inside of the bowl whilst in the freezer. Any water that is frozen to the inside of the bowl will melt into the mix and is likely to have an adverse effect on ice cream texture.
Take a 1 litre plastic container, the freezer bowl, and the ice cream dasher and place them in your freezer overnight. Freezing will remove any heat stored in the dasher and container. Heat that is transferred to the ice cream during freezing from the container or dasher increases ice crystal size, by melting the crystals, contributing to a sandy texture. If you add ice cream to a plastic container that is at room temperature, you will notice the ice cream that comes in contact with the side of the container quickly start to melt, which is a big no no as is likely to cause a sandy texture.
It’s also important that you freeze enough water to be able to make an ice bath. Freeze water in several ice trays or small plastic containers.
2. Setting the fridge and freezer temperature
It is very important that set your fridge to between 0 and 2°C to increase the rate of crystallisation of the fat globules when you age your mix overnight. Crystallisation of fat during the ageing process helps maintain the shape of ice cream when it is served and also helps minimise the rate at which the ice cream melts. If you don’t allow these fat globules sufficient time to crystallise, it is likely that your ice cream will suffer from relatively fast meltdown and less retention of shape.
Set your freezer to around -25°C, or as cold as you can get it. Once churned in the ice cream maker, the quicker you can get your ice cream to below -18°C, the smaller the ice crystal are likely to be, and the creamier the texture. The temperature and rate of hardening determine the final ice crystal size . Hardening is complete when the temperature at the centre of the ice cream container drops to -18°C or lower, preferably -25 to -30°C. The longer it takes for the ice cream to reach these temperatures, the larger the ice crystals will grow and, subsequently, the sandier the texture will be.
The importance of a really cold freezer
I cannot stress enough the importance of setting your freezer as cold as you can get it. An extremely cold freezer is not only important when storing your ice cream, but is also extremely important for your machine’s removable bowl.
I’ve noticed that a bowl frozen to around -14°C takes longer to churn a batch of ice cream, compared to a bowl frozen to around -18°C or below. Because a bowl frozen at around -14°C will take more time to churn a batch of ice cream, it is more likely to produce a colder, sandier, and wetter texture. I set my freezer to around -25°C and the resulting ice cream is much drier, smoother, and holds its shape better, compared to when I use a bowl that has been frozen to around -14°C.
At about -25°C, it takes me about 16 minutes to churn a batch of ice cream, which is very good for a domestic ice cream maker (professional ice cream makers take about 8 minutes). If I set my freezer to around -14°C, it takes between 20-25 minutes for the bowl to churn a batch. Remember, the quicker you can churn your mix, the smaller the ice crystals are likely to be and the creamier the texture of your ice cream.
3. Preparing an ice bath
Once you have allowed enough water to freeze, take a large pan and fill it with enough ice to make an ice bath. Have a large zip-lock freezer bag ready next to the bowl, along with some table salt.
The point of using a zip lock bag and water bath is to ensure that the mix is cooled as quickly as possible once it has been cooked, minimising the time the mix spends in the ‘danger zone’ where bacteria likes to multiply; between 5 and 65°C. The longer your mix spends in this temperature range, the more bacteria is likely to multiply, imparting an undesirable taste and smell.
4. Size of pan
As strange as it sounds, the size of the pan in which you heat your mix is extremely important. The larger the diameter of your pan, the more water will evaporate during heating. This is important because the fundamental reason for heating your mix for 60 minutes is to concentrate the milk solids non fat, more specifically the protein.
By concentrating the mix, you increase the percentage of protein. Protein plays a significant role in limiting the size of ice crystals, thereby improving texture. The higher the percentage of protein in your mix, the creamier the texture is likely to be.
I recommend using a large pan with a 23cm diameter. This will allow you to concentrate your mix by about 32%. If you use a pan with a smaller diameter, you won’t be able to reduce the mix by the same amount in 60 minutes. The texture won’t be as smooth and creamy as a mix prepared in pan with a larger diameter.
Use a large pan with a 23cm diameter, similar to the one on the left
5. Heating your mix
Once you have prepared the ice bath, add the sugar and the egg yolks to the pan. Mix the eggs and sugar together until both ingredients have combined. Mixing the sugar with the yolks will help prevent the yolks from curdling. Add the cream and milk and gently stir the mix before you switch on the heat.
Over a medium heat, heat the mixture until the temperature reaches 70°C, making sure that you are constantly stirring. You will risk burning the proteins and curdling the egg yolks if you do not constantly stir the mix.
Once the temperature reaches 70°C, turn the heat down to low and continue heating until the temperature reaches 71.4°C. Use a kitchen thermometer to keep the temperature at 71.4°C for 60 minutes. The aim is to promote reversible unfolding of the whey proteins but not aggregation, which will significantly improve the texture of the finished ice cream.
Try not to let the temperature rise above 71.4°C. It will be difficult to keep the temperature at 71.4°C and you will find it quickly fluctuating between about 71.2°C and 71.8°C. It’s not the end of the world if you do briefly go above 71.4°C but do quickly bring the temperature down if you notice it creeping up. You will risk aggregating the proteins, which is detrimental to texture, and developing the unpleasant and eggy hydrogen sulphide taste if you heat the mixture above 71.4°C.
Heating the mix for 60 minutes may sound like a long time but believe me it is a small price to pay for extremely smooth and creamy ice cream. Holding the mix at 71.4°C for 60 minutes will concentrate the mix by about 32%, thereby increasing the percentage of protein. After trying different variations, I have found that a mix heated for 60 minutes produces a much creamier and smoother ice cream than one heated for 15, 30, and 45 minutes.
6. Cooling the mix
After 60 minutes, take the pan off the heat and carefully pour the mix into the zip lock bag. Pour about 2 tablespoons of salt onto the ice to lower its temperature. This will cool your mix faster.
Once the mix has cooled to about 10°C, place it in the fridge and leave overnight to age. Remember that crystallisation of fat during the ageing process helps maintain the shape of ice cream when it is served and also helps minimise the rate at which the ice cream melts.
7. Churning the mix
Once you have allowed the mix to age overnight, place the freezer bowl in the machine and add the dasher. Put the lid on and, with the machine switched on, pour in the mix followed by the almond paste.
If you’re using a machine with an in-built compressor, switch the machine on and leave it for about 20 minutes before you add the mix. This will ensure that the bowl gets as cold as possible.
As soon as you pour in the mix, use your thumb to push the dasher against the side of the bowl. Pushing the dasher against the bowl will prevent any ice from freezing to the side. Any ice that is frozen to the side of the bowl will act as an insulator, slowing the release of heat from the ice cream to the bowl.
If the transfer of heat from the ice cream to the freezer bowl is reduced, the ice cream will take longer to freeze. The longer the ice cream takes to freeze, the larger the ice crystals will grow and the sandier the texture is likely to be. Keep the dasher pushed against the side of the bowl until you have finished churning the mix (a sore thumbs is yet another price to pay for smooth creamy ice cream).
Use a spoon to push along any static lumps of ice cream. Any static lumps will start to melt, causing a sandy texture. Ensure that the mix is constantly moving whilst in the machine.
After about 20 minutes (or about 16 minutes if your freezer was set to around -27°C), the mix should have a nice dry, stiff texture and should stick easily to the dasher when you take it out of the machine. If the mix drips too easily off of the dasher and has a wet shine, churn the ice cream for another 5-10 minutes.
Quickly empty the mix into the pre-chilled container. The longer you take to empty the ice cream into the container, the longer the ice cream will spend at room temperature. At room temperature, ice crystals will start to quickly melt. If ice crystals melt, they will grow bigger in size when the ice cream is placed in the freezer. The longer the ice cream spends at room temperature, the sandier the texture is likely to be. Be as quick as you can when emptying the ice cream into the plastic container.
8. Hardening the ice cream
Once the mix has been churned, it will have a consistency similar to soft-serve ice cream (Mr Whippy). Although you can eat the ice cream straight after it has been churned in the machine, I recommend hardening it in a plastic continaer in the freezer for at least 4 hours before serving. After about 4 hours, depending on your freezer, the ice cream will have a nice firm scoopable consistency, somewhere around -15°C, and be ready to serve.
9. Serving the ice cream
Scoop and serve the ice cream at around -15°C. If you can wait, allow the ice cream to warm to below -12°C before eating. As the serving temperature is increased from -14.4 to -7.8°C, flavour and sweetness become more pronounced.
10. Storing the ice cream
Ice crystals will continue to grow until the temperature drops to below -18°C. It is therefore critical to get the your ice cream into the freezer and down to below -18°C as quickly as possible to prevent a sandy and coarse texture from developing. Make sure that there is enough space in your freezer for the air to circulate freely. The more cluttered your freezer, the longer it will take for ice cream to reach -18°C and the bigger the ice crystals will get.
At -18°C, it is recommended that homemade ice cream be kept for about a week. Ice cream can be stored for several weeks at -25°C, and several months at -30°C. Even at these low temperatures, ice crystals will eventually start growing in size. The longer you store your ice cream in the freezer, the larger the ice crystals are likely to be and the sandier the texture.
Any questions or suggestions, feel free to send me a message.
Hope this recipe helps!
Protein found in milk and cream plays a significant role in giving ice cream a smooth and creamy texture. Flores and Goff (1999) demonstrated that milk proteins had a large impact on texture by limiting ice crystal size and enhancing their stability.
The easiest and cheapest way of increasing the protein content in ice cream is through the addition of skimmed milk powder. In keeping with my ethos of using only natural ingredients in my ice cream, I avoid using this heavily processed powder by heating my mix for 60 minutes. This evaporates water and increases the percentage of protein in my ice cream. I think this is a much better, albeit more tiresome, way of increasing the protein content in ice cream as it avoids the addition of heavily processed ingredients.
After years of standing over my ice cream batches stirring away for hours on end, I decided to search far and wide for a way of maintaing a mix at a constant temperature whilst stirring it at the same time. After a lot of research, I stumbled across a magnetic stirring hot plate, a device more commonly found in science labs than in kitchens. Could this be adapted to the kitchen I wondered.
Although these machines aren’t cheap, they are much cheaper alternative to a £14,000 ice cream pasteuriser, and so I took the plunge and invested in one. A magnetic stirring hot plate is my first step towards increasing production!
After a LOT of trial and error, I finally figured out how to adapt this device for ice cream making! Here is my first IKA magnetic stirring hot plate in action.
Flores, A. A., and H. D. Goff, 1999, Ice crystal size distributions in dynamically frozen model solutions and ice cream as affected by stabilizers, J. Dairy Sci. 82:1399-1407.
So despite some cold and cloudy weather, we still managed to get the Batmobile down to Oxford Brookes University to get some feedback on our flavours! We also wanted to get people’s opinion on our portable ice cream trailer (the Batmobile) made by Ben using recycled wood.
The idea is to use renewable energy to power the portable freezer using our mounted solar panel. Coupled with good old leg power to power the bicycle, these small ideas get us one step closer to being the most sustainable and environmentally friendly ice cream company in the world!
We are preparing our homemade ice cream trailer to sell ice cream at Oxford Brookes University! Ben has been working non-stop for the past week adding the finishing touches to the bat mobile. What better way to start a business than to make equipment yourself from recycled wood! We have nearly finished adding the solar panel that will power our portable freezer.
We will be at:
Harcourt Hill Campus on Wednesday 18th September 2013
Wheatley Campus on Friday 20th September 2013
Gypsy Lane Campus on Monday 23rd September 2013
Marston Road Campus on Wednesday 25th September 2013
Come and say hi!
Ruben and Ben
I have finally launched my Kickstarter project to raise funds to buy an Emery Thompson ice cream machine and grow my small business:
Please click here to make a pledge!
The idea behind Ice Cream Science is to combine science and quality ingredients to make the best ice cream in the country.
I’m obsessed with making nothing but perfect ice cream and have been relentlessly experimenting over the past two years with ingredients, science, and techniques. Everyone has seen how chefs like Heston Blumenthal have innovated and pushed food forward. I feel that ice cream has been somewhat left behind. I want to incorporate science and gastronomy into ice cream making to develop new and exciting flavours and textures.
To make the best ice cream, you need to use the best ingredients; I use free-range organic eggs, organic milk from grass-fed cows, fresh cream, and un-refined sugar to make my ice cream base. I use real pistachios in my pistachio ice cream, 80% dark chocolate in my chocolate ice cream, and real mangos in my mango and green peppercorn ice cream.
So last summer I put my theory to the test and started selling ice cream at food festivals. I received great feedback, both about the concept and the ice cream, and was also approached by local cafes wanting to stock my ice cream. I painfully had to turn these requests down as my Cuisinart home ice cream maker simply couldn’t churn out more ice cream. This summer I want to change that.
WHERE YOU COME IN
I’ve been granted a street sellers’ license by Oxford County Council to sell ice cream from King Edward Street in Oxford, on condition that I put my ice cream freezer on a custom, and expensive, ice cream bike.
To start selling ice cream in Oxford and to approach local restaurants, cafes, and delis, I need to grow my business. I simply can’t make enough ice cream with the Cuisinart home ice cream maker that I’m currently using.
To grow my business, I want to invest in a commercial ice cream machine that is capable of churning 6 litres of ice cream in 8 minutes, and a custom ice cream bike, which I plan to sell ice cream from in Oxford and at events.
I also want to invest in equipment usually found in science labs: I want to invest in a magnetic stirring hotplate, to act as a cheaper alternative to an industrial pasteuriser, an aspirator pump so I can reduce the water content in fruit and milk without having to heat them and alter their flavour, and a blast chiller to freeze the ice cream as quickly as possible after it has been churned.
THE ICE CREAM
Please consider making a pledge or sharing the project on the social networks!
All the best, Ruben