TROUBLESHOOTING BY PALSGAARD
Ice cream quality suffers from the effects of temperature fluctuations during transport and storage. Discover what lies at the root of the problem and how the right combination of emulsifiers and stabilisers can help ice cream manufacturers maintain good ice cream from the factory doors to the consumer's table.
Ice cream is a complex system of foam, containing a gas (air) dispersed as small cells in a partially frozen continuous phase. In the continuous phase, fat is dispersed as an inner phase in an emulsion, where the milk solids and stabilisers are in a colloidal solution and sugar and salts form a true solution.
Three ingredient types exert the most influence on a typical ice cream’s ability to withstand heat shock: milk solids, sugars, and additives in the form of emulsifiers and stabilisers.
Milk solids and sugars both have a lot to say when it comes to the freezing point of the ice cream, so it is important to get both the types and amounts used exactly right.
Fat, while important for the product’s structure, has little effect on its ice crystals, since it works in the fat phase and not in the water phase.
Milk solids act to stabilize ice cream and provide body for the product’s networked structure.
But they are an expensive part of the product, making their reduction a desirable move for many manufacturers. If less milk solid is used, however, there will be a greater proportion of water in the product. And all that moisture needs to be crystallized – resulting in a watery mouthfeel and greater instability.
Choosing a milk solid that can combat heat shock requires manufacturers to have a good eye for quality. First, the milk solid needs to be in a form that is best able to support the formation of the desired texture. Most often, a powder is used, but milk or cream is also relatively common.
Sugars play twin roles in ice cream: helping to control taste and the product’s freezing point. Adding a lot of sugar lowers the freezing point, helping to achieve the softness needed, for example, for scoopable ice cream applications. But doing so also makes the product more vulnerable to damage along its journey, with more free water moving to attach to the existing ice crystals and causing them to grow. Too little sugar, on the other hand, makes the ice cream harder.
Even with the same fat and milk solid content, the percentage of water frozen into ice crystals will vary if sugar levels or types are adjusted.
Figure 2 shows the effect of a different sugar composition alone on the freezing curve of ice cream containing 8% fat and 11% milk-solids-nonfat (MSNF).
Sugar, of course, comes in different types. Ice creams typically use a combination of refined sugar and, for example, glucose syrup. This combination affects the texture and the freezing point of the product, too. Some producers even add a little salt to the mix, further depressing the freezing point and adding to heat shock susceptibility.
The most common emulsifiers used in ice cream are mono-diglycerides (E471), lactic acid esters (E472b), propylene glycol esters (E477) and blends of these.
Generally speaking, good compositions can be made with most of the widely-used emulsifiers and stabilisers such as mono- and diglycerides, carrageenan and locust bean gum. If that is, they are used in the right amount and compositions to suit each recipe.
Adding propylene glycol esters such as propylene glycol monostearate (PGMS), for example, protects against the Heat Shock Effect by ensuring small ice crystals are created during freezing and reducing their tendency to grow during the journey to the consumer’s table, as shown in Figure 4.
Figure 5 depicts two melting curves of an ice cream that was melted using a special machine for accurate measurement. The amount of ice cream landing in bowls placed under the product was measured as a percentage of its overall weight. The upper curve reflects an ordinary ice cream recipe, while the lower curve, which performs far better, shows the effect of adding one of Palsgaard’s integrated blends of emulsifiers and stabilisers, Palsgaard® ExtruIce.
It’s worth noting that melting curves can be influenced by homogenization, too, if homogenisation isn’t conducted at the right pressure level. This doesn’t directly affect heat shock robustness, as such, but may weaken the ice cream’s structure and hasten melting.
So, which emulsifier is best for countering the effects of heat shock? Monodiglyceride (E471), for example, comes in many forms and qualities (differing in fatty acid composition, and in the levels of mono and diglycerides) each bringing out different qualities in ice cream.
Composing an emulsifier stabiliser blend with the right composition to work with an ice cream’s structure, protect against heat shock and achieve everything else the manufacturer and the product’s consumers would like takes a great deal of expertise. And it demands an unrelenting eye on the Big Picture, comprising ingredients, emulsifier/stabiliser composition, process and equipment. You may also be wise to discuss your product’s packaging with its manufacturer, who may be able to recommend better packaging and handling solutions.
At Palsgaard, we work with different recipes to find the right combination and quality of emulsifiers and stabilisers. We know, for example, that not all emulsifiers will work well with milk replacers (cheaper milk solids used to replace skim milk powders) and they’re likely to have a different effect depending on the type of milk solids used, too. And that means there is much more trial and error involved in figuring out exactly which additives, combinations of additives and dosages will work best.
What is your heat shock protection strategy? It’s likely to depend on factors such as your product’s market positioning in terms of quality, conditions at your factory and the realities of price points, for example, in your part of the world.
Whichever steps you take, you can be sure that building heat shock stability into your ice creams will help to maintain their quality, providing a better consumer experience and a more secure future for your products in retail outlets. Without a doubt, the emulsifier/stabiliser blends you choose will be at the heart of making it all happen.
Remember, too, that reviewing your emulsifier choices brings an important new opportunity: the ability to introduce sustainably sourced and produced ingredients, meeting fast-growing consumer and regulatory priorities. A good example of that could be Palsgaard’s range of non-GMO, vegetable-based, sustainable emulsifiers which are produced in 100% carbon-neutral production plants, and which can be made using only 100% RSPO (Roundtable for Sustainable Palm Oil) Segregated-level palm oil and derivatives.
TROUBLESHOOTING BY PALSGAARD