Ice cream coating is usually a very high-fat product which will change viscosity and behavior during production. Therefore this well tasting coating is often a source to production, quality and price problems, but it does not need to be so!
Using the right emulsifier systems reduce the potential problems and in addition to this open the possibility of making a stable production of low-fat and cost-effective coating which will improve the competitiveness of your products.
For the ice-cream industry chocolate and compound coatings are widely used to add extra value to the ready-to-eat products. The combination between the relatively sweet ice-cream base and the relatively distinct cocoa flavour creates a well balanced flavour appreciated by most consumers. The usage of coating has not been given too much attention in the literature taken into consideration its complexity, difference from ordinary chocolate and that it is a source for potential problems.
In many ways chocolate is by nature incompatible with the ice-cream and this can create problems at the production stage. In the manufacturing process of chocolate it is a general rule to avoid water during the entire process, and in the conching step a lot of effort is exercised to reduce the total water content in the chocolate well below 1%. Higher content of water will increase the viscosity of the chocolate dramatically making it unsuitable for production as the flow properties will become too poor.
On the other hand ice cream is a system typically holding 65% water which is mainly frozen in the final stage, but during the manufacturing process a great proportion of the water will be found in a liquid stage. Where it is attempted to keep the temperature as low as possible during manufacturing of ice-cream, the chocolate has to be heated to 30 – 40o C in order to remain liquid. The contact between the frozen surfaces of the ice-cream sticks and the warm chocolate will thaw some water which will migrate into the chocolate causing an increase in viscosity and yield value resulting in increased layer thickness and crystallization time.
Emulsifiers like lecithin - but especially PGPR (polyglycerol polyricinoleate), are known to improve the flow properties of the liquid chocolate mass and to a certain extend counteract this negative effect of water. It is therefore interesting for the ice-cream industry to take food emulsifiers into consideration when working with liquid chocolate or ice cream coatings.
Chocolate for Ice Cream - Typical Enrobing
Chocolate is in many countries a protected product where a certain purity standard must be followed. There are restrictions on the minimum content of cocoa components and on the type of fats allowed. Also the use of food emulsifiers is restricted and regulated according to local food standards and legislation.
In terms of fat, cocoa butter is the main component in chocolate. Milk- and white chocolate also contain milk fat which makes the chocolate softer, more plastic in consistency and shows less contraction during crystallization. Even in dark chocolate for ice-cream applications it is highly recommended to add 4-5% anhydrous milk fat making the chocolate more plastic. This will reduce the cracking problems, especially in extruded ice-cream types where the centre is hard and there is no room for this contraction, and hence the chocolate will crack.
Today also many countries allow addition of up to 5% non cocoa based vegetable fat to be added, and still maintain the status as a real chocolate. These so called cocoa butter equivalents (CBEs) might also be applied to plasticize the chocolate.
Typically the total fat content of an ice-cream chocolate will reach approx 40 – 45%.
ICE CREAM COATING - compound coating
Ice-cream coatings - typically thin layers are manufactured from rather inexpensive fats like coconut oil or hydrogenated palm kernel fat. Contrary to an ice-cream stick covered with a thick layer of real chocolate, the ice-cream coating should only form a thin layer round the ice-cream stick. The total fat content is therefore often above 60% in order to achieve a sufficient thin layer and a short crystallization time.
Both coconut oil and palm kernel fat are forming quite hard and brittle coatings upon cooling, so as for the ice cream chocolate it is recommendable to "soften" the fat phase. Here addition of approx 8% liquid oil e.g. maize, peanut, sunflower or rape seed oil will provide the necessary plasticity to the coating.
Addition of approx 5% skimmed milk powder to a dark coating will improve the flavour of the coating balancing the bitterness of the alkalized cocoa powder.
Emulsifiers work in the chocolate by improving the flow properties of the liquid chocolate mass. Especially some emulsifiers lower the plastic viscosity whereas other emulsifiers influence the
so-called yield value. The yield value can be defined as the energy input needed to initiate flow of the chocolate. As an added benefit for the ice cream manufactures, the emulsifiers also have the ability to absorb a limited amount of water which is destined to be transferred from the ice-cream to the chocolate during dipping or enrobing of the ice cream sticks or bars.
Soya lecithin (E 322) is the most abundantly used emulsifier in chocolate. The emulsifier has the ability to lower the plastic viscosity in the chocolate, but when added at dosages above 0.5%, the yield value of the chocolate will increase making flow more difficult.
Especially in an ice cream chocolate this is a disadvantage, as higher dosages of emulsifier will improve the water binding capacity of the chocolate.
Finally soya lecithin might provide disadvantages in terms of the GMO-status and allergen status of the ice cream product.
Ammonium phosphatide (E 442) – is a well known alternative to soya lecithin, and is widely used by the chocolate industry. Being a non-soya based emulsifier, the ammonium phosphatide - PALSGAARD® 4448, has a non-GMO status and is not considered to be an allergen. Furthermore dosages above 0.5% will not increase the yield value of the chocolate noticeably. PALSGAARD® 4448 has a very neutral flavour profile and will therefore not have any negative impact on the chocolate flavour in the ice-cream chocolate.
Citric acid csters of mono- diglycerides (E 472c) – PALSGAARD® 4201 is a fairly new emulsifier for the chocolate industry, but it’s functionality as a full alternative to soya lecithin is generally recognized in the chocolate industry. PALSGAARD® 4201 is also a non-soya based emulsifier and hereby carries a non-GMO and non allergen status. Quite unique is the ability of PALSGAARD® 4201 to lower the plastic viscosity as well as the yield value of the chocolate. This feature can be utilized to lower the total fat content of the chocolate and still maintain good flow properties. PALSGAARD® 4201 is also an excellent water-binder, and hereby provides further safety in the ice cream dipping process avoiding viscosity build-up during processing.
Polyglycerol olyricinoleate (E 476) – PALSGAARD® 4125 is a highly effective water-binding emulsifier, which also will reduce the yield value dramatically even at dosages down to 0.2 %. The strong effect on the yield value makes it possible for the ice cream manufacturer to reduce the pick up of chocolate per ice cream stick/bar. Also the strong effect of PALSGAARD® 4125 can be utilized in lowering the total fat content of the chocolate with up to 5% and in this way make room for a considerably cost saving.
Recipes for Dipping Trials
Typical recipe suggestions on a milk ice cream chocolate are shown in table 1.
By adding 0.30% PALSGAARD® 4125 it is possible to reduce the fat content from the typical 40% down to 36%. By use of PALSGAARD® 4201 instead of ammonium phosphatide or soya lecithin, the necessary dosage of PALSGAARD® 4125 is slightly reduced.
In order to demonstrate the effect of PALSGAARD® 4125 in an ice cream chocolate and illustrate the potential saving in fat, three different chocolates were manufactured:
1. Chocolate 40% total fat without PALSGAARD® 4125
2. Chocolate 36% total fat with 0.30% PALSGAARD® 4125 added
3. Chocolate 36% total fat with 0.30% PALSGAARD® 4125 added
As lecithin replacer, 0.5% Palsgaard® 4448 is added to sample 1 and 2 whereas Palsgaard® 4201 is used in sample 3.
The chocolates were kept at 40o C and frozen vanilla ice-cream sticks tempered at minus 18o C were dipped in the liquid chocolate for approx. 2 seconds and allowed to drip off until the chocolate had fully crystallized.
For each chocolate 10 ice-cream sticks were dipped and the average pick up was recorded.
From the results in table 2 it is clearly demonstrated that addition of 0.30% PALSGAARD® 4125 allows you to reduce the fat content with 4% and achieve the same quality in the finished product but with a significant cost saving as the result. Using Palsgaard® 4201 will enable an additional reduction.
This result shows a way to reduce the fat content from e.g. 40% to 36%. It will naturally also be possible to keep the fat content at e.g. 40% and with an addition of Palsgaard® 4125 to reduce the pick up significantly if this is requested.
Water Migration and How to Reduce the Effect
Often the ice-cream sticks are frozen in a round-freezer before dipping into the coating.
This provides a further challenge to the ice-cream manufacturer as the last step in the round- freezer is a reheating process allowing the ice-cream sticks to be released from the moulds. As a result of this reheating step, the surface of the ice-cream sticks is quite moist, and when dipped into the 30-35oC warm coating, some of the ice cream mix will end up in the coating.
If this water is allowed to accumulate in the coating, the viscosity will increase, and the pick up per ice-cream stick will go up as well. Increasing the temperature of the coating will reduce the pick up, but at the same time even more ice-cream mix is melted into the coating, and a vicious circle has been started.
It is therefore of utmost importance to secure that the temperature of the ice-cream is as low as possible - preferably minus 15o C in order to reduce the moisture migration to the ice-cream coating and to avoid the formation of pinholes. Pinholes is created by melted and expanding ice- cream mix bubbling out through the still soft coating.
Here PALSGAARD® 4125 is very interesting due to it’s exceptionally high water binding capacity. By using a combination of 0.50% soya lecithin and 0.30% PALSGAARD® 4125 the viscosity in the liquid coating will remain low, even when up to 4% ice cream mix has been added. This is illustrated in figure 1 and illustrate that addition of Palsgaard®4125 will reduce the problems caused by moisture normally seen during a production run.
Adding 0.30% PALSGAARD® 4125 it will also open the possibility of reducing the fat content in the coating with up to 7% as demonstrated in table 3.
Emulsifiers - Summary
Soya lecithin is widely used in ice cream coatings, and due to the very high fat content, yield value considerations are not putting restrictions to the dosage as is seen in chocolate formulations. Therefore often up to 1% lecithin is added to ice cream coatings.
Ammonium phosphatide or citric acid esters of mono- diglycerides can fully replace the soya lecithin if a non-GMO or non-allergen status of the emulsifier system is required.
Polyglycerol polyricinoleate (PGPR) - PALSGAARD® 4125 differs positively from the other emulsifiers due to the unique yield value reducing power and its ability to efficiently reduce the negative effect of moisture in ice-cream coatings. Using this product will assist in a stable production and open the possibility of making a more cost effective coating.