What’s new in an old product?

Ice cream and related desserts have been manufactured for centuries, the history of which is a fascinating tale replete with old-fashioned imagery of wholesomeness, tradition, family fun and folklore1. Today, though, ice cream is a very large global business that is anything but standing still in tradition. This paper will review notable recent advances in formulations, ingredients and manufacturing equipment within the ice cream and related frozen dairy dessert category.

The ice cream and related products industry is estimated to be a ?23 billion global business – a number rising to as high as ?37 billion if small-scale manufacturers are included2. As a dairy food, it represents 17 per cent of total global sales2. Industrial consolidations have brought multi-nationals (Unilever and Nestle being the big two, worldwide) to the forefront of the global industry and they have invested heavily in modernisation and new technologies. A 2003 International Dairy Federation symposium on ice cream in Thessaloniki, Greece, attracted some 300 industrial and academic scientists from around the world and its proceedings contains 42 papers representing scientific advancement and technical innovation in ice cream3. Four recent papers also provide detailed reviews of the state-of-the-art in ice cream technology4.

Formulations

The boundaries of conventional ice cream formulations are being stretched in all directions, illustrated by new introductions in categories such as reduced/low/no fat; reduced/low/no sugar; organic and nutritionally-fortified products.

Lower fat products have been available for a number of years, but the quality of these is steadily improving. The motivation behind such product developments is two-fold:

• The desire on the part of consumers to reduce their total or saturated fat intake
• The desire to reduce energy density of ice cream and related products

Dietary cholesterol, as present in milk fat, is no longer considered a marketing point per se as it was 10-20 years

ago, owing to the fact that nutritionists and consumers have learned of the limited link between dietary and serum cholesterol levels. However, saturated fat intake remains an important dietary indicator of potential for enhanced serum LDL cholesterol and trans unsaturated fats have been linked to both enhanced LDL and decreased HDL cholesterol – both of which are indicators of the potential to develop cardiovascular diseases. Depending on the source of fat, these may be important issues for consumers and product developers. Milk fat, on the other hand, is complex and, in the context of whole milk ingredients, including the solids-not-fat component, may have numerous health benefits. Some of these are not yet understood, however. In fact, regular dairy product consumption, including ice cream, has been linked to decreased incidence of insulin resistance, obesity and cardiovascular disease, particularly among young people5. Hence, from a nutritional point of view, recommendations to reduce milk fat intake may not be warranted.

Ice cream is an energy-dense food, however, so reductions in fat for the purpose of reductions in energy density may be alluring to many consumers. Obesity is a growing trend world-wide, increasing at alarming rates in some countries such as the US6. Hence, energy-dense foods will become increasingly targeted as contributors to obesity. Energy-dense products must be justifiable in terms of nutrient density to satisfy the growing demand for an all-out assault on obesity. Regardless of the reasons for lowering the fat content of ice cream and related products, one thing remains clear: quality cannot be compromised if sales are to remain.

In addition to the low fat category, ice cream and related products that can make low carbohydrate or no sugar added (NSA) claims are also newcomers to the product line-up. Again, there are multiple reasons. There is a consumer interest, particularly in the United States, in weight loss from low carbohydrate diets, popularised by the Atkins approach, amongst others. Some predict that this may be a passing trend, not worth the effort to cater to in terms of new products. However, it is also true that the incidence of Non-Insulin Dependent Diabetes Mellitus (NIDDM or Type II diabetes) is increasing world-wide and in some countries at an alarming rate – particularly amongst younger people6. This has led to a large market segment looking for low glycemic index foods – and this trend is not anticipated to abate soon. These issues are in addition to the more general need to reduce energy density, as discussed previously. Hence, the case can certainly be made for new product introductions in the NSA category. Ingredients for ice creams to satisfy these interests will be discussed later.

Yet another emerging category in the case of ice cream is that of nutritionally-fortified products. These include formulations with probiotics and prebiotics and those that are enriched with any combination of vitamins, minerals, soluble fibre or nutraceuticals4. Ice cream can be an excellent carrier of nutritionally-significant ingredients. It is frozen and close to neutral in pH so stability is usually good and most people are willing to consume fortified nutrients in a product they enjoy eating. Functionality (texture, freezing point depression) or flavour may be issues, depending on the substance to be fortified.

Some consumers and producers have shown market interest in Organic products and in Genetically Modified Organism (GMO)- free products. These trends may not involve formulation changes but rather careful ingredient selection.

Both of these trends require very careful supplier scrutiny to ensure the traceability of all substances that end up in an ice cream formulation.

Ingredients

There are numerous ingredient innovations for ice cream formulations. Only a few will be highlighted here, but further details are readily available4,7.

Concentrated sources of milk solids-not-fat, such as condensed or dried skim milk, were found in all traditional mix recipes. Improved functionality and/or reduced cost have seen many changes to this ingredient category. Milk ingredient manufacturers are custom blending many ingredients suited for various ice cream formulations. The functional demands of water holding capacity/viscosity enhancement, foaming and emulsification must be met by the protein component. Whey proteins and caseinates have become commonplace as components of these ingredients and new innovation has occurred with membrane processing to produce high protein products with enhanced functionality. Microparticulation/microgelation has also been employed to improve protein functionality for low fat applications.

In NSA formulations, sugar alcohols are common sweetening agents. The right balance of sweetness, freezing point depression and total solids contribution is critical when reformulating the sweetener component. Low molecular weight monosaccharide alcohols, such as erythritol or xylitol, can be utilised for their contribution to freezing point depression. Disaccharide alcohols such as maltitol, lactitol or isomalt provide similar freezing point characteristics to sucrose but with varying sweetness and taste profiles. Non-nutritive high-potency sweeteners, such as aspartame or sucralose, can be used to boost sweetness intensity if required, but do not contribute to freezing point depression.

Hydrocolloids are also well established mix ingredients as viscosity enhancers and for ice recrystallisation inhibition. However, enhanced levels of hydrocolloids as bulking agents are necessary in some product development applications and polydextrose, inulin and various starches have all been used. Other soluble fibres have also been examined for fortified products although, in the case of fortification, the challenge is to find soluble fibres that do not contribute as much to viscosity enhancement or textural guminess. New options are also becoming available for the control of ice recrystallisation. One recent innovation arises from the beneficial effect seen from the use of certain emulsifiers such as propylene glycol monostearate4. The incorporation of ice structuring proteins from natural sources also provides another innovative means of ice recrystallisation control8.

All the ingredients interact together to form ice cream structure, which gives rise to texture. From a scientific point of view, there has been a tremendous increase in knowledge regarding ice cream structure over the last decade. As an example, in a 2002 review of colloidal aspects of ice cream structure9, 31 ice cream-specific scientific references were quoted that were published in the years since 2000.

Innovation in ice cream flavours abound4. There are very little limits to the type of flavours that can be included in ice cream. Internationalisation of the product has led to migration of ethnic flavours around the globe. Equipment innovations, such as modified inclusion feeders and shaker tables, allow for larger and more defined particulates with a wider range of textures to be added to ice cream. Examples of new flavour introductions in the last year include tiramisu, spicy walnut raspberry streusel, carrot, beet, cucumber/dill, candied red beans, molasses/cinnamon, chai tea, green tea, lemon grass, wasabi and on and on4. However, flavours require custom blending to work in specific formulation applications. The NSA formulations, for example, provide more of a challenge in terms of flavour perception compared to traditional formulations.

Equipment

Equipment suppliers have also been extremely busy with innovation in the last decade. There are three global leaders in this area: TetraPak Hoyer (www.tetrapakhoyer.com), Gram Equipment (www.gram-equipment.com) and WCB Ice Cream (www.wcbicecream.com). A look at any of their websites will provide a tremendous appreciation of innovation in equipment development – not only in freezers but in all aspects of a modern process, including automated ingredient feeders and product shaping, forming and packaging equipment.

Probably the most exciting innovation has been the development of low-temperature extrusion equipment for ice cream products. While there are now several manifestations of this development, the earliest innovation can be credited to Professor Erich Windhab of the Technical University of Zurich (ETH), Switzerland10. This equipment takes ice cream from a conventional scraped-surface freezer and passes it through a (single- or twin-) screw extruder where temperature is lowered from, for example, -5°C to -12°C. The addition of inclusions and packaging is still possible at these low temperatures, with appropriate equipment and considerable quality improvement and energy/cost-savings result, compared to conventional convective or conductive freezing. Some formulation changes, particularly in emulsifier content, may be required to optimise fat structure.

Another area of recent innovative interest in ice cream mix processing is the application of high pressure, either as high pressure homogenisation or as hydrostatic high pressure11. In the former case, the goal is to produce a smaller mean fat globule size distribution with more fat globules. It is imperative that the right selection of proteins and emulsifiers be used to obtain an optimal fat globule membrane-the concept is that more fat globules can produce optimal fat structure in lower fat applications. Hydrostatic high pressure has been used to modify protein structure in ice cream mix, also with the goal of achieving smoother textures than are possible with conventional processing techniques.

In conclusion, although one could argue that ice cream formulations, ingredients and manufacture still follow similar principles to those of 50 or more years ago, it should be obvious that innovation is at the forefront of the modern ice cream industry. As with many other food industries, ice cream manufacturers that do not continually invest in research and product development will be left behind in the marketplace. Three trends seem to drive the need for innovation in ice cream. Firstly, consumers are becoming more demanding of composition, particularly from a nutritional point of view. Secondly, globalisation and consolidation of the retail marketing industry has put increased demands on the shelf-life of ice cream products, so stabilisation of structure to maintain texture-particularly in the wake of the potential for temperature abuse-remains an important and challenging issue. Lastly, competition remains keen, so cost-saving while preserving quality is another factor that drives the search for new and innovative processes and ingredients.

Notes

1. For interesting reading of the history of ice cream, see any of the following: Dickson, P. 1972. The Great American Ice Cream Book, Atheneum, New York; Funderburg, A. C. 1995. Chocolate, Strawberry and Vanilla: A History of American Ice Cream. Bowling Green State University Popular Press, Bowling Green, OH, USA; Reinders, P. 1999. Licks, Sticks and Bricks, A World History of Ice Cream, Unilever, Rotterdam.
2. Thomas, N. and H. D. Goff. 2003. Ice cream goes global: higher demands on technology. Food Engineering & Ingredients. 28(4): 22-24; Thomas, N. and Elphinstone, P. 2004. Present/future trends in the global ice cream industry. In Goff, H. D. and B. W. Tharp, eds. 2004. Ice Cream II. Special Issue 401. International Dairy Federation, Brussels. pp. 7-20.
3. Goff, H. D. and B. W. Tharp, eds. 2004. Ice Cream II. Special Issue 401. International Dairy Federation, Brussels.
4. Marshall, R. T. and H. D. Goff. 2003. Formulating and manufacturing ice cream and other frozen desserts. Food Technol. 57(5): 32-45; Burrington, K. J. 2004. 21st Century Ice Creams. Food Product Design. www.foodproductdesign.com/archive/2004/0504DE.html; Pszczola, D. E. 2005. Innovative chills ahead for frozen desserts. Food Technology 59(3) 40-51; Phillips, D. 2005. Ice Cream Outlook. Dairy Foods. www.dairyfoods.com/CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,6809,147301,00.html
5. Pereira, M. A. et al. 2002. Dairy consumption, obesity and the insulin resistance syndrome in young adults. Journal of the American Medical Association. 287(16): 2081- 2089.
6. See, for example, www.cdc.gov/nccdphp/dnpa/obesity, from the Center for Disease control and Prevention in the US. See also www.cdc.gov/diabetes/, from the same source.
7. Marshall, R. T., H. D. Goff and R. W. Hartel. 2003. Ice Cream, 6th Edn. New York: Kluwer Academic.
8. Goff, H.D., A. Regand and B. W. Tharp. 2002. The potential for natural ice-structuring proteins in ice cream. Dairy Industries International. 67(10): 30-32.
9. Goff, H. D. 2002. Formation and stabilization of structure in ice cream and related products. Current Opinion in Colloid and Interface Science. 7: 432-437.
10. Windhab, E. J. and S. Bolliger. 1998. Low temperature ice cream extrusion technology and related ice cream properties. European Dairy Magazine. 10: 24-28; Bolliger, S., B. Kornbrust, H. D. Goff, B. W. Tharp, and E. J. Windhab. 2000. Influence of emulsifiers on ice cream produced by conventional freezing and low temperature extrusion processing. Internat. Dairy J. 10: 497-504.
11. Hayes, M. G., A. C. Lefrancois, D. S. Waldron, H. D. Goff, A. L. Kelly. 2003. Influence of high pressure homogenisation on some characteristics of ice cream. Milchwissenschaft. 58: 519-523; Gray, S. J., and Turan, S. 2000.

Preparation of an aerated frozen product using high pressure homogenization. International Patent WO 00/01246, US Patent 6,497,913; Keenan, R. D., Wix, L. and Young, D. 2000. Preparation of an ice confection with ultra high pressure treatment. United States Patent 6,156,367.