A half-century ago, Doug Goff grew up in a home in Truro, NS where the freezer usually held seven or eight flavours of ice cream and a sleeve of cones was nearby. Today, Goff is known as Dr. Freeze around the world for his pioneering research into making consistently better ice cream.
“You could say that I was pretty much born into it, yes,” Goff says with a chuckle.
And Goff can still scoop all the ice cream he wants, as the professor of physical chemistry at the University of Guelph responsible for a unique ice cream technology course that is celebrating its 100th anniversary this year. “It’s fun to be known as the Ice Cream Prof; at the same time the complexity of ice cream from a physical chemistry point of view has been a great thing to study,” says Goff.
Doug Goff — aka Dr. Freeze — says that superior ice cream is a happy marriage of numerous ingredients like caseins, lactose and emulsifiers. Photo credit: Martin Schwalbe
The 54-year-old wasn’t considering a research career when he came to Guelph in 1980 to finish a degree in dairy science after two years at the Nova Scotia Agricultural College in Truro. He fully expected to return home to the same dairy operation where his father worked for four decades (explaining the well-stocked home freezer.) But he was offered a summer job by A.M. (Sandy) Pearson, the professor then overseeing the ice cream technology course. That triggered a curiousity about a foodstuff people had consumed for centuries but still didn’t totally understand. The timing was opportune because significant advances were underway in ice cream research. “Ice cream has a complicated structure, a balance of air, fat and ice. It’s both an emulsion and a foam. In the last three decades we’ve made great strides in understanding how all these components come together, understanding structure and shelf life through sophisticated tools like electron microscopy. Before that the manufacturing of ice cream was more on the art side than on the science side.”
Goff applied to Cornell University in Ithaca, NY — “it had a great ice cream program” — where he did both his MS and PhD. The title of his thesis was “The role of chemical emulsifiers and dairy proteins in fat destabilization during the manufacture of ice cream.” In 1987 he returned to Guelph to take over the technology course from Pearson, who had retired, and assume a full teaching load in the Department of Food Science. For the past 15 years he’s taught the nutritional sciences course, which dovetails neatly with his ice cream specialization.
The ice cream technology course could be looked upon as the cherry atop the sundae of the dairy science program at Guelph. Since its inception in 1914 more than 3,000 ice cream industry people from around the world have completed what is now a five-day course. Participants over the past five years have come from North America (all Canadian provinces, the United States and Mexico), Europe (United Kingdom, France and the Netherlands), the Middle East (Kuwait, United Arab Emirates) as well as the Philippines.
Low-temperature scanning electron micrograph of ice cream after the initial aeration, whipping and freezing step. Numerous air bubbles can be seen, each about 40 micrometres in diameter. Ice cream is a frozen foam, about half its volume is air. Photo credit: Douglas Goff, Dept. of Food Science, University of Guelph.
Low-temperature scanning electron micrograph of ice cream after hardening and temperature-abusive storage, showing a large increase in ice crystal size, resulting in a coarsening of texture. Air bubbles can be seen between the ice crystals and fat globules can be seen adsorbed to the air bubbles. Photo credit: Douglas Goff, Dept. of Food Science, University of Guelph.
Low-temperature scanning electron micrograph of ice cream showing a close up image of the surface of an air bubble. Numerous fat globules can be seen adsorbed to the surface, a phenomenon that is responsible for giving the ice cream many of its desirable properties of shape retention, slowness of melt and smoothness. Fat globules are about one micrometre in diameter. Not all fat globules exist at the air interface; some can also be seen as a discrete phase in the unfrozen solution. Photo credit: Douglas Goff, Dept. of Food Science, University of Guelph.
Goff’s forefront research into the physics and physical chemistry of ice cream has been carried out separately from the technology course, working over the years with an estimated 60 to 70 graduate students and collaborating with colleagues at Guelph and elsewhere. His website lists three books, 40 book chapters, 139 articles in refereed journals and 37 publications in non-refereed journals, nearly all with an ice cream flavour.
The central focus of Goff’s research over three decades has been the structure of ice cream, which he considers “both fascinating and confusing. It can be described as a partially frozen foam with ice crystals and air bubbles occupying a majority of the space.” Goff considers that his greatest contribution to ice cream science has been to help develop the basic understanding of the roles of the various ingredients: milk fats, other milk solids like caseins and lactose, sweeteners, stabilizers and emulsifiers and water, in forming structure. “Structure is central to the quality of the product. It is the ultimate determinant of manufacturing performance, scoopability, texture, shelf life and ingredient functionality. And, from a science perspective, it’s where the physical chemistry comes into play.”
Texture and taste are the ways most people judge the appeal of ice cream. And structure determines the perception of the texture — is it silky smooth and creamy, or rough and granular? “Most people are unaware of what they’re consuming. A lot of them seem surprised when they hear that half the volume of ice cream is air and that it’s full of really small bits of ice. I sometimes say to myself that it should be obvious that it does have ice in it, since it is called ice cream.” This ice content is one of the big challenges in elucidating the structure of ice cream since, as Goff points out, you can’t put something that melts quickly under an ordinary microscope. Fortunately, Guelph’s Food Science department has long boasted a top-notch electron microscopist, Alexandra Smith, and working together she and Goff pioneered some of the research methods now standard in the field.
Goff’s lab has specialized equipment to carry out differential scanning calorimetry at subzero temperatures, low-temperature scanning electron microscopy, transmission electron microscopy and light scattering and spectrophotometric analysis techniques for analyzing particle size distribution. The detailed investigation of structure is especially relevant for large-scale industrial manufacturing where the ice cream is going to be shipped long distances and could sit in freezers over a protracted time, requiring the addition of stabilizers in significant amounts. By contrast, the sooner the ice cream will be consumed, the less need for stabilizers and other additives that can affect both taste and texture. Which is why Goff says some of the best ice cream in the world is found at street gelato stands in Italy. Those traditional artisan ice creams with their unique flavours, rich creamy base and same-day freshness captivated him on his first visit to the country. “I probably ate gelato two or three times a day. It was so good. Of course the freshest ice cream tends to be the best if it has been formulated well. We make a lot of ice cream here at the university and people always say, ‘Oh it’s so good.’ Again, it’s very fresh.”
Even though the dairy science program has the equipment to make a large amount of ice cream, it doesn’t sell it on a regular basis or even supply the university cafeteria. What isn’t consumed on site is given away or donated to charitable events. “We’re not here to run a business and I’m not interested in becoming the manager of an ice cream facility in my spare time,” Goff says.
In his spare time, in fact, Goff doesn’t get very far from ice; he’s an avid club curler in Guelph. When not concentrating on draws and take-outs as a vice-skip, however, he’s tackling aspects of one of the newest wrinkles in the world of ice cream — frozen desserts. In the supermarket freezer these look almost identical to traditional ice cream, with labels making claims such as “Classic Vanilla.” But the tiny type hidden on the package reads, “Frozen Dessert.” Missing from the ingredient list are milk fats, which must be more than 10 percent by weight for the product to qualify as ice cream.
Instead of relatively costly milk fats, frozen desserts use fats derived from vegetable oils such as coconut or palm kernel oil that are much less expensive. In 2006 the federal government gave the green regulatory light to this substitution. The impact can be seen in the official statistics for the production in Canada of the milk-fat-containing “mix” used to make traditional hard and soft ice creams. It peaked in 2005 at 172,699 kilolitres and by 2012 had plunged to 110,007 kilolitres. “There isn’t any data on the consumption of these frozen desserts. It looks like the market has gone down but if we could look at both ice cream and frozen desserts, it has probably gone up,” says Goff.
Goff says that most people cannot detect either a taste or texture difference between the best examples of frozen desserts and ice cream. He’s fairly sure he could for any vanillas, which he considers the gold standard for ice cream because any off-flavours from stabilizers aren’t masked. There is, however, a considerable cost difference that anyone can distinguish between milk-fat-based ice cream and vegetable-fat-based frozen desserts. Goff speculates that parents might buy the frozen desserts for their children but treat themselves to a premium ice cream, which could have 15 percent milk fat and be only 20 percent air by volume.
The surge of frozen desserts has produced a new research challenge for the Goff lab — finding a domestic oil to substitute for the imported tropical vegetable oils currently used. The replacement has to be solid at the freezer temperatures used to harden ice cream, typically below -25 C, something canola and other Canadian-grown seed oils can’t manage. “Here comes the science,” says Goff. “We need to find a way of converting our unsaturated domestic oils that will give us the fat products that we need. And we have to stay away from hydrogenation because that produces transfats, which are unhealthy.”
Back when Goff first set up his lab at Guelph, such research might have been supported by Discovery Grants from the Natural Science and Engineering Research Council. However, now all his ice cream and related research is underwritten by industry. He steers away from proprietary product development work, aiming instead at publishable research that benefits graduate students and the industry as a whole. One segment of the industry that is particularly interested in their sponsored research being published is the manufacturers of ingredients such as stabilizers, emulsifiers and milk proteins. “They want everybody to know that academics have had a look at their products,” says Goff.
Another area of continuing research involves sugars in ice cream, or their absence. The obvious job of natural sugars like sucrose and fructose is to deliver sweetness. But they also play a less obvious yet crucial role in a physical chemistry reaction known as freezing point depression. This means that the ice cream remains scoopable at the temperatures of the serving tubs in retail outlets, typically -16 C. The challenge is to balance the various sugars so that different flavours of ice cream not only have the desired sweetness but are neither too soft nor too hard for scooping into hand-packed cones. This is where Raoult’s Law comes into play. In 1882, French chemist François-Marie Raoult formulated a complex law of thermodynamics which has an everyday application in ice-cream making. It states that the lowering of the freezing point of a solution varies with molar concentration of the dissolved substance. Since fructose has half the molar weight of sucrose, only half as much by weight would be needed to lower the freezing point of an ice cream mix by the same number of degrees.
Today, problems abound for ice cream makers. Consider non-sugar sweeteners like aspartame, which is widely used in soft drinks. It’s such a concentrated sweetness that only a tiny amount is required for ice cream. But that’s far too little to depress the freezing point and the resulting mixture will be “hard as a rock” at serving temperatures, says Goff.
To further complicate matters, sugar alcohols such as sorbitol and maltitol are attractive for ice-creaming-eating consumers with diabetes because of their low glycemic index. But heavy consumption has been linked to bloating, gas and diarrhea and can require an off-putting “caution” label on the package. “There are a lot of very bad no-sugar-added products on the market,” Goff says with a sigh.
Still, a truly astonishing range of exotic and enjoyable ice creams is available. Forever on the lookout for something different, Goff has licked his way through blue cheese ice cream in Ireland (“very good”), lobster bisque (at a dairy foods conference), black bean, Guinness (again in Ireland) and a jalapeno made in his own lab.
And the best news is saved for the last. Goff says it’s healthy to eat ice cream despite well-founded public concern about obesity. Portion size is the key. “You can’t eat your 2,500 calories a day and then go out and have a three-scoop ice cream cone.”