Why are stabilizers used in ice cream?

Stabilizers in Ice Cream

What are ice cream stabilizers?

Stabilizers are hydrocolloids that are water-soluble, i.e. they disperse in water, and are commonly used in ice cream making. Stabilizers extensively used in the ice cream industry include guar gum, locust bean gum, carboxy, ethyl cellulose (CMC), sodium and propyleneglycol alginates, xanthan, gelatin, and carrageenan (Goff and Hartel (2013)). These stabilizers are derived from plants, bacteria, and animal by-products. Although derived from natural sources, stabilizers are considered food additives under European law.

Plants

Most stabilizers used in ice cream making are of plant origin. These include sodium alginate (E401) extracted from brown seaweeds, carrageenans (E407) extracted from red seaweeds, locust bean gum (E410) and guar gum (E412) extracted from tree seeds, pectin (E440) extracted from citrus peel and apple pomace, carboxymethyl cellulose (CMC) (E466) extracted from cotton and wood pulp, and sodium (E401) and propylene glycol (E477) alginates extracted from kelp.

Bacteria

Xanthan (E415), a bacterial polysacharide produced by the bacterium Xanthomonas campestris, is used as a stabilizer in ice cream making.

Animal by-products

Gelatin (E441), a polypeptide of animal origin (mostly from bones, bovine hides, and pig skin) is also used as a stabilizer. Gelatin was traditionally used as a stabilizer in ice cream making but has now largely been replaced by polysaccharide hydrocolloids in ice cream making. So we know that stabilizers are food additives that are derived from plants, bacteria, and animal by-products.  Let’s turn now to why stabilizers are used in ice cream making.

Why are stabilizers added to ice cream?

So just why are stabilizers added to ice cream? According to Goff and Hartel (2013), the primary purposes for using stabilizers in ice cream are to:

  • increase mix viscosity;
  • retard ice crystal and lactose crystal growth during storage;
  • help prevent shrinkage of the ice cream during storage and
  • reduce the rate of meltdown.

Let’s look at each of these points individually.

Increase mix viscosity

Mix viscosity can be loosely defined as the thickness of the ice cream mix. Generally speaking, the thicker and more viscous a mix is, the better the texture is likely to be. A certain level of viscosity is also essential for proper whipping and retention of air that is incorporated during the churning process, and for good body and texture in the ice cream (Goff and Hartel (2013)). Increasing the concentration of stabilizer, protein, fat, and total solids in a mix will increase viscosity, with stabilizers having the greatest effect on mix viscosity (Goff and Hartel (2013)).

Concentrating a mix by evaporating some of the water will also increase mix viscosity. I have found that heating a mix at around 71.4°C for 60 minutes denatures whey proteins, which contributes significantly to smooth and creamy texture, and also increases mix viscosity thus reducing the need for stabilizers.

Retard ice crystal growth during storage

All ice cream will eventually become sandy and coarse as the ice crystals grow during storage. Small ice crystals, essential for smooth and creamy texture and developed during the whipping process, will eventually grow into large crystals that are detectable on the tongue. These crystals can be easily seen when you open an ice cream tub that has been left in the freezer for months and find large bits of ice on your ice cream.

Stabilizers are added to ice cream to slow down the rate at which ice crystals grow during storage. Stabilizers retard ice crystal growth by slowing the rate of diffusion of water to the surfaces of growing crystals (Goff and Hartel (2013)).

Although stabilizers keep ice crystals smaller for longer during storage, they actually have little (Caldwell et al., 1992) or no (Sutton and Wilcox, 1998a,b) impact on the ice crystal size distribution in ice cream right after it has been churned in the machine and also little or no impact on initial ice crystal growth during quiescent freezing and hardening (Flores and Goff, 1999a), but they do limit the rate of growth of ice crystals during recrystalisation (Flores and Goff, 1999b).

So, we know that small ice crystals are essential for smooth and creamy texture (see my post on ice crystal size effect on texture). Stabilizers do not have an effect on the size of ice crystals at the time the ice cream is churned in the machine. This means that adding stabilizers will not promote the formation of small ice crystals when the ice cream is made. Ice crystals will grow over time and the bigger they grow, the sandier the texture becomes. The longer ice cream is left in the freezer, the bigger ice crystals grow. Stabilizers are added to retard this ice crystal growth so that the texture stays smoother for longer.

Because stabilizers do not have an effect on ice crystal size when ice cream is made, ice cream that is freshly made and eaten within a short time does not really need added stabilizers. Stabilizers are mainly added to ice cream to increase its shelf life in the supermarket by keeping ice crystals smaller for longer. That is why you rarely find added stabilizers in good ice cream parlours where the ice cream is freshly made, consumed within a short period of time after it has been made, and not stored for long periods of time.

Help prevent shrinkage of the ice cream during storage

Shrinkage can be seen in ice cream that has been stored for long periods of time and has contracted or ‘deflated’ so that it no longer touches the sides or the lid of the container. Shrinkage is sometimes noticeable when you open an ice cream tub that has been left in the freezer for a while and notice that it has deflated and looks somewhat flat. Shrinkage results from a loss of air bubbles as they come together and begin to form continuous channels, eventually leading to collapse of the product itself into the channels (Turan et al., 1999). Stabilizers are added to ice cream to slow down the rate of shrinkage.

Reduce the rate of meltdown

The melting rate of ice cream is of great importance; no one likes an ice cream that quickly turns to slush as you are eating it. Added stabilizers increase the melting resistance of ice cream due to their water-holding and microviscosity enhancement ability (Goff and Hartel (2013)).

Ice Cream defects caused by stabilizers

Although stabilizers have many beneficial functions in ice cream, too much stabilizer can have adverse effects on texture. These include a gummy or sticky texture that is often slow to melt and a heavy or putty-like texture.

Conclusion

Although stabilizers have many beneficial effects on ice cream, I have found that extremely smooth and creamy ice cream can be made at home without the need for added stabilizers. The beneficial effects of added stabilizers can be easily achieved by heating a mix to somewhere around 71.4°C and keeping it there for 60 minutes. This increases mix viscosity and improves the water-holding capacity of protein.

The increased milkfat used in home made ice cream also plays a similar role to added stabilizers in that it will retard or reduce the rate at which ice crystals grow during storage, keeping the smooth and creamy texture for longer. I still maintain that these food additives should not be used in ice cream and that the main reason they are added to commercial ice cream is to allow companies to keep their ice cream on supermarket shelves for longer.

Because us home-made ice cream enthusiasts devour our ice cream in a matter of days, we don’t need to store it in the freezer for months and months and do not, therefore, need to add stabilizers.

I hope that helps.

All the best,

Ruben :)

References:

Bahramparvar, M. and M Tehrani. 2011. Application and functions of stabilizers in ice cream, Food Reviews International, 27:4, 389-407

Caldwell, K. and D. Goff, and D. Stanley, 1992. A low temperature scanning electron microscopy study of ice cream. 1. Techniques and general microstructure. Food Struc. 11:1-9

Clarke, C., The Science of Ice Cream, 2004

Flores, A. and D. Goff 1999a. Ice crystal size distributions in dynamically frozen model solutions and ice cream as affected by stabilizers. J. Dairy Sci. 82:1399-1407.

Flores, A. and D. Goff, 1999b. Recrystallisation in ice cream after constant and cycling temperature storage conditions as affected by stabilizers. J. Dairy Sci. 82:1408-1415

Goff, D. and R. Hartel, Ice Cream, Seventh Edition, 2013

Sutton, R. and J. Wilcox, 1998a. Recrystallisation in model ice cream solutions as affected by stabilizer concentration, J. Food Science. 63:9-11

Sutton, R. and J. Wilcox, 1998b. Recrystallisation in ice cream as affected by stabilizers. J. Food Science. 63:104-197

Turan, S. and R Bee. 1999. Measurement of gas phase morphology in ice cream. In Bubbles in Food, pp. 183-189.

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Comments

  1. says

    I’m really enjoying your site, Ruben, although I take issue with some of your conclusions in this post. Stabilizers aren’t just used to cut corners in manufactured ice cream. The best pastry chefs in the world use stabilizers in their ice creams. I think you’d be hard pressed to find ones who don’t (not counting ones who use paco-jet, which generally makes stabilization optional).

    It’s important to recognize that you do indeed use stabilizers in your recipes. Egg custard is both a stabilizer and an emulsifier. Denatured milk proteins are both a stabilizer and an emulsifier. The former is added purely for these textural duties; the latter are there anyhow, but you are greatly increasing their proportions with your methodology.

    The objective question is: what is the best way to achieve the desired textural qualities? All methods have their advantages and disadvantages. Egg custard gives a wonderful texture, but it also gives the flavor of eggs (which you may or may not want) and it has much stronger flavor masking properties than many of the alternatives. I can’t speak to the pros and cons of high concentrations of altered milk proteins (although I believe this is similar to the method used by Haagen Dazs).

    Personally, I like the results I get with a very small quantity of egg custard and a small quantity of hydrocolloids. The latter has the advantage of working in minute quantities, of having perfect flavor release qualities, and zero detectable flavor of its own. There are no downsides, besides marketing ones. People reading labels are prone to thinking these ingredients are artificial or unhealthy (they’re not, and they’re not). But I am interested in using science to improve the ice cream, not to pander to unscientific views.

    • Ruben says

      Hi Paul!

      Many thanks for getting in touch. I do think that stabilisers are used in ice cream to cut corners and keep costs down as it is easier to add stabilisers than it is to heat a mix for a longer period of time or increase the total solids count. I don’t see the need for the addition of artificial or excessively processed stabilisers in homemade ice cream.

      Yes you are right that denatured whey proteins play a similar role as stabilisers. I don’t object to the beneficial role that denatured whey proteins play but I do object to the use of artificial or excessively processed stabilisers in my ice cream. I’ve chosen not to include any artificial ingredients in the ice cream that I sell and certainly think there is a premium in doing so.

      I have found that heating my mix to 72°C for 25 minutes produces excellent ice cream with smooth and creamy texture. I’d be interested to get your feedback on how my recipes compare to the ones you have tried that include stabilisers.

      I hope that helps. Let me know if you have any other questions.

      All the best,

      Ruben

  2. Sharon says

    I’m a gelato maker. Wouldn’t cooking the ice cream at that temperature be
    Ike re-pasteurizing the ice cream, destroying the protein content, fruit flavors?

  3. Stacy says

    Awesome post! I’ve been trying to understand the role of stabilizers for a while and your post was very helpful :) You mentioned heating the mixture for 60 min @ 71.4C. I live in the US so that translated to about 160F.This might sound dumb, but I’m wondering if that high of a temp would scramble the eggs in the mixture? Unless you don’t add eggs in your mix?

    • Ruben says

      Hi Stacy!

      Hope the post helped. I haven’t had an issue with curdling the egg yolks at around 72°C as long as the mix is constantly stirred. The sugar, milkfat, and non-fat milk solids also protect the yolks from curdling in that it takes a bit more heat for them to curdle. Mixing the sugar with the yolks before adding the milk and cream also helps.

      I’m experimenting with skim milk powder at the moment to bring down the 60 minutes heating time to around 35 minutes as I know that standing in front of your cooker for 60 minutes isn’t the most interesting thing to do. I will try and post that recipe soon.

      Hope that helps.

      All the best,

      Ruben

  4. says

    Great post about stabilizers — very interesting.

    I agree that there’s rarely a need for it when making ice cream at home, although it can occasionally help compensate for extra water when using fruit or making sorbets — but even then, other ingredients can be used such as alcohol.

    One place where I think it’s (unfortunately) essential is in gelato. A homemade batch of ice cream with a recipe that’s around 18-19% butterfat doesn’t really need stabilizers, but gelato made from 3.5% milk needs something to help with your first bullet point: “increase mix viscosity”. Commercial gelato mixes are loaded with multiple stabilizers, and I think it’s about impossible to make gelato at home unless you do the same — or increase the butterfat to the point that it’s really just ice cream and not gelato anymore.

    I’d be interested to hear your thoughts. Thanks,

    Russell

    • Ruben says

      Hi Russell!

      Good to hear from a fellow ice cream geek. I agree that you do need something in gelato to compensate for the reduction in milk fat but I don’t think that something should be stabilisers. You can increase mix viscosity by adding skim milk powder, which also increases the protein content. You can also increase mix viscosity by heating the gelato mix for 60 minutes; this denatures proteins and also concentrates the mix, thereby increasing non-fat milk solids.

      I haven’t actually made gelato myself but it is on my to-do list for this month. I will let you know how I get along.

      Do you make and sell your own gelato?

      All the best, Ruben

  5. Henning says

    I think additives like stabilizers shouldn´t be used in icecream shops/parlors. That would be a uge benefit for all customers.
    -You only get icecream when the season is there. Business would be back in the hands of those who really care about what they do.
    – you recognize old icecream. Shop owners are forced to sell like a bakery this is kind of difficult due to changing weather,ha. Ageing the mix would be an issue too. But then again who tastes the difference and if the weather is fine you are out of icecream at the end of the day anyway

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