October 1, 1998

30 Min Read
Indulgent Ice Cream

Indulgent Ice Cream
October 1998 -- Cover Story

By: James C. Burg
Technical Editor

  Fat is out, right? Well, not in the case of indulgent ice creams. These guilty pleasures are a hot item in the freezer case, boasting funky formats and flavors.
"Being a liberal with milkfat would be part of the definition of designing indulgent ice creams," says Bill La Grange, Ph.D., extension food scientist, Iowa State University, Ames. "Milkfat in the 14% to 18% range would be more typical for indulgent products. Also, the very good flavors and flavor combinations that have been developed are an important element of the category. Intense, dairy-compatible flavors are integral to the design."

Structurally speaking

  Ice cream is a three-dimensional frozen foam, consisting of frozen films surrounding air bubbles, and containing frozen fat micelles distributed between the films. The films consist of the ice cream mix sugars, milk proteins, added stabilizers and frozen water crystals. The fat micelles contain frozen milkfat and emulsifying milk proteins, plus added emulsifiers. High fat levels, even distribution of the suspended air bubbles, and small particle size of the ice crystals all contribute to ice cream's creaminess.

  Fat level and total solids level, including fat, sugar and milk solids, all play a major role in the finished product. Also important are levels of emulsifiers and stabilizers used to modify structural integrity. Creaminess, stiffness, bite, meltdown and resistance to heat shock are characteristics that determine the ice cream's quality. The composition and storage temperature maintain product stiffness. The bite, or resistance to shearing by the teeth, must neither be too hard, nor too soft, like a soft-serve frozen dessert product. Meltdown refers to ice cream's ability to retain its shape at serving temperatures. It must neither melt very quickly, nor must it hold its shape indefinitely like a gel. Resistance to heat shock is due primarily to stabilizers. Temperature fluctuations occur during product storage and shipment. Warmer temperatures allow partial melting, which leads to growth of ice crystals on refreezing. This growth can damage the ice cream structure and produce a coarse, rough-textured mouthfeel.

  The amount of air incorporated into the mix during freezing, known as overrun, is lower in high-fat ice creams. Standard ice creams may have half of their volume represented by air, a 100% overrun. "Indulgent ice creams would have overrun levels of 40% to 65%," says Irwin Immel, director of development, proteins and fats, Kerry Ingredients, Beloit, WI. "Too low an overrun can churn out butterfat in a 16% ice cream. It's hard to keep the fat in a good emulsion." The lower overrun gives the product a creamier, bulkier body, due to the higher density of the ice cream. Overrun affects handling, mouthfeel and cost.

  Mixing efficiency in the freezer promotes homogenous incorporation of air cells into the matrix, allowing the product to melt more evenly. The greater the number of air cells present in the product, the less cold-tasting the product will feel. "The primary reason for lower overrun, usually 20% to 50%, is that the more fat in a product, the less cold-tasting it is, and in that way, the less refreshing," says Phil Keeney, Ph.D., professor emeritus, Pennsylvania State University, University Park. "The more air in a product, the greater the insulating effect. If you have both a lot of fat and a lot of air, and especially when the air cells are finely emulsified, you're going to have a product that tastes more like a whipped topping. You want that cold and refreshing character. In contrast, with a lowfat dessert, higher overrun provides warming and smoothing qualities to compensate for the loss of fat somewhat."

Freeze frame

  Indulgent or higher-fat ice creams are prepared by the same processes as other ice creams. The higher fat and total solids levels require freezer equipment adjustment for the desired overrun amount and consistency, as well as setting the freezing rate for proper ice-crystal growth.

  The rate of freezing and subsequent storage temperature fluctuations largely determine texture. Coarse mouthfeel can be due to ice-crystal growth. Abuse temperatures can partially melt the product, resulting in collapse of the foam structure and loss of overrun. A typical sucrose level in premium ice cream, 16.5%, will depress the freezing point of water about 1.13°C (2.03°F). Since the mix freezes at a lower temperature, ice crystals are smaller, providing a smoother texture.

  The mix is pumped to a freezer, typically a continuous type in larger operations. Very rapid freezing produces small ice crystals in the adhering mix. Allowing the frozen layer to build up on the wall's surface reduces heat transfer and produces ice crystals that are too large and uneven in size. A chaser, or scraper, continually shaves the partially frozen mix off the walls. This provides an even ice crystal size, preferably below 35 µm. Nozzles inject air into the frozen mix, and a series of whipping blades pushes the mix forward while incorporating fine air bubbles. The aerated frozen mix exits the freezer barrel in a semifluid state to the fillers for hard-packing. Slow freezing of the serum phase can cause breakdown of the fat emulsion by the concentrated salts. The milkfat can then coalesce as larger fat globules, with subsequent flavor problems. Excessive milk solids can contribute to precipitation of lactose crystals, resulting in graininess. Furthermore, formation of large ice crystals can damage the films, which maintain the structure, causing a loss of volume during storage.

  Freezer storage and shipping temperatures must be maintained at or below -18° C to ensure optimum quality. Storage and shipping freezers are subject to rising and falling temperatures, which can, in some cases, be equivalent to as many as 360 cycles per month. The product won't necessarily reach an equilibrium temperature as extreme as the storage temperatures, due to heat-transfer lag times. Control of ice crystal melt can be aided by stabilizers. However, it is essential that temperatures never reach -12°C (10°F). Concentration effects can then lead to water-melting and migration and enlarged ice crystals.


  Indulgent ice creams have milkfat contributed from cream, whole milk and condensed milk. Milk solids nonfat (MSNF) are in the range of 7% to 8%. Sugar is at the level of 16% to 17%. Sugar in indulgent ice creams generally is sucrose, although corn syrup solids and high fructose corn syrup also are used in lower-fat products, because their greater freezing-point depression leads to small ice crystals.

  The higher fat levels, 14% to 18% milkfat, mask some of the sweetness. The stable emulsion within the milkfat system requires less added emulsifier to maintain the emulsion. Some super-premium products have approached 20% fat. Generally, better properties would be obtained in the 16% fat area, as creaming, or fat separation, might occur at higher fat levels.

  "Condensed milk should not be overcooked," says Immel. "There are qualities of condensed milk, that if you heat it in such a way that it becomes a highly heated product, the denatured proteins can add body to ice cream upon freezing. However, you don't want it over-caramelized.

  "Primary focus in designing indulgent ice creams is on the quality of ingredients," he says. "The fresher the better, and quality control of the received product is monitored to prepare the best product. The milkfat and proteins of new cream and milk provide not only the best taste, but are responsible for the structure and keeping quality of the finished products. Ingredients for indulgent ice creams are typically the best available - small amounts of egg sometimes and sucrose."

  The primary milkfat emulsion is often supplemented with emulsifiers and stabilizers at levels of 0.20% to 0.25% combined total of the mix. Egg yolks can act as an emulsifier, due to their lecithin. However, if used, levels of 0.5% to 1.0% prevent too strong an egg flavor. Lecithin also can be added as an emulsifier at 1% to obtain a clean label. Often, ice creams use mono- and diglycerides as emulsifiers.

  Emulsifiers are needed for smooth structure, but also perform another function. "Emulsifiers help to stabilize the foam structure, but are often eliminated from indulgent ice creams because of ingredient-labeling considerations," Immel says. "Ice creams at 20% fat without emulsifiers can take on a greasy mouthfeel.

  "Another product which can add functionality and a clean label to a premium ice cream product is a milk protein isolate obtained by ultrafiltration," Immel explains. "The process retains much of the original milk globule membrane, consisting of proteins with high fat affinity. This protein membrane is a good emulsifier. It provides good mouthfeel, and has a smooth and creamy texture. It is as effective as gums, while providing a clean ingredient label."

  Gums absorb available water, preventing its migration and restricting ice-crystal growth. They also might control water by forming coiled strands around the free water, preventing migration, or by forming gels that restrict water movement.

  Stabilizer choice depends on product properties sought. One critical factor is the degree of ice-crystal growth during storage controlled by stabilizers. Stabilizers can increase meltdown time so a product won't quickly soften and lose its shape during serving. Also, the body of the product is an eating-quality characteristic providing the right degree of melt, mouthfeel, refreshing character and bite. Mix viscosity during air incorporation and pumping of the partially frozen product is an important production and quality factor. The right stabilizer level depends on the fat content, other ingredients and best incorporation of the stabilizer into the mix. Cost is an element that is somewhat less prominent, as use levels are typically low in indulgent ice creams.

  Stabilizer systems are blends of stabilizers and emulsifiers designed for maximum effect. The customized blends consist of gums such as guar, locust bean and carrageenan, coupled with mono-and diglyceride emulsifiers. Carboxymethylcellulose, a cellulose-derived product with good water control properties, can also be used as a stabilizer. Custom blends can be obtained depending on the label declarations desired. An indulgent product design would typically strive for an "all-natural" label. A lecithin and gums system at 1% helps build the frozen film strength.

  "One way of stabilizing an emulsion is by increasing viscosity," says Florian Ward, Ph.D., vice president and director, R&D, TIC Gums, Belcamp, MD. "Gums add body, bind water and prevent water migration in the frozen product. You don't need much gum to stabilize the ice cream emulsion. Gums form a film around the emulsion and make it more stable by preventing oil from coalescing. Gums such as guar, locust bean gum and carrageenan have high molecular weights, so they adsorb or immobilize water better. Gums also allow a slow, creamy meltdown of ice cream. Under repeated freezing and melting of product by the consumer, gums help to increase heat-shock resistance, and reduce ice-crystal growth during re-freezing."

  Ward cites an ice cream study, "The Influence of Polysaccharides on the Glass Transition in Frozen Sucrose Solutions and Ice Cream," in the May 1993 Journal of Dairy Science, that used a stabilizer of 0.15% locust bean gum and 0.02% carrageenan. Samples of the prepared ice cream were stored at abuse temperatures for 24 weeks. At zero time, mean diameters of the ice crystals were 43.3 ±3.3 µm for the unstabilized control and 35.4 ± 3.2 µm for the stabilized sample. After 24 weeks of storage, the respective crystal diameters were 113.7 ±7.0 µm and 95.4 ± 5.1µm. Crystal size growth was about 19% greater for the unstabilized product than for the stabilized sample. Water control by the gum blend at this low level was moderately effective in controlling the crystal size over time.

What's in a name?

  Indulgent ice creams can reside in lower fat regions. FDA defines ice creams under regulation 21 CFR Part 135 in terms of fat contents, allowed sweeteners and dairy additives, plus applicable technologies. Under the standards, "lowfat" ice cream may not contain more than 3 grams of total fat in a half-cup serving. "Nonfat" ice creams must contain less than 0.5 grams of total fat per half-cup serving. The products must not be nutritionally inferior to regular ice creams, allowing supplementation. Ingredients are allowed to maintain organoleptic qualities, and additives must be part of the label statement. The products must have a density of at least 4.0 lbs. per gallon.

  Total solids levels of lowfat desserts might be in the 28% to 38% range. Sugar comprises much of the solids, with other bulking agents based on whey and polydextrose, sugar alcohols such as sorbitol, MSNF levels, and higher levels (0.40% to 0.50%) of emulsifiers and stabilizers than high-fat ice creams. Ice creams having 3% to 9% fat, and even lower-fat products (which are the most difficult to design), rely on increasing amounts of emulsifier and emulsifier/stabilizer blends to mimic the creamy texture of regular ice creams. At lower levels of fat, milk proteins also assist in improving texture.

  Indulgent lower-fat products also will rely on the types and quantity of inclusions and flavors to earn a designation of indulgent. Variegate syrups with high sugar levels are used at less than 20% of the mix, as sugar will draw moisture from the frozen dessert. Use of mildly acidic fruit inclusions, with more fruit chunks and added flavor, can circumvent curdling of the partially frozen mix due to acidic effect on the milk proteins under less-than-ideal temperature production and storage conditions.

  Flavor expression becomes more difficult as fat levels are reduced. Small amounts of fat are better than no fat in providing flavor. Use of a gum, such as xanthan at a level such as 0.1%, also might lower flavor release. Use of concentrated flavors, flavor potentiators, cream flavors and milk notes improve the profile.

Thanks for the flavor

  Flavor of the month is what's happening in the age of indulgence. Everything old is new again, and some new flavors will become old-timers in the current scurry for the unique in ice cream products. Cherry has become sour cherry has become chocolate-covered maraschino cherry.

  Indulgent ice cream flavors are typically natural flavors. Determining the optimum flavor levels is important, due to the ability of the fats and proteins to retain some of the flavor components in their respective matrices longer. Levels required might increase as fat percentages increase, and not necessarily in a linear manner.

  Typically, for 10% to 12% fat ice creams, 0.3% vanilla might be used, according to Paul Graffigna, vice president, marketing, Virginia Dare, Brooklyn, NY. Probably proportionally more vanilla would be used for a 14% to 18% fat ice cream, and sometimes substantially beyond that concentration might be used in the same fat-level ice creams.

  "The actual requirement depends on the end user," Graffigna says. "When we demonstrate a product that's fairly heavily flavored, sometimes we'll get comments to the effect that it's good, but that a lot couldn't be consumed. Usually the customer wants a flavor level that's moderate so that a reasonable portion could be consumed."

  To attain the same flavor intensity, profile and temporal expression in ice creams containing different fat levels, the designer must modify or choose different flavor levels for optimization. "Fruit flavors deliver good character in ice creams, especially coupled with fruit inclusions," says Janet Schurig, director, flavor applications, Virginia Dare. "The pH can be adjusted somewhat if required to provide some flavor modification." Inclusions and variegates in the product can often boost the identical flavor profile if there is no competition from flavor blends.

  The continuing flavor favorite or flavor base in an ice cream containing inclusions is vanilla. For indulgent ice creams, pure vanilla is the product of choice, and the premium product is bourbon vanilla. A two-fold pure bourbon vanilla extract would be used at 0.3% by weight in a 12%-fat ice cream as a starting point. A product at 16% fat might require at least 0.4% two-fold vanilla as a starting point, and perhaps considerably more, depending on the total composition of the product.

  The natural flavors developed for premium ice creams are relatively heat-stable, and can be added to the mix before pasteurization, especially HTST pasteurization. They should provide natural profiles post-pasteurization, with no stability issues in the product. Natural & artificial flavors, with brilliant characterizing and fresh notes, also are stable.

  "Under freeze/thaw conditions, some products in storage are getting beaten up," Schurig says. "If we can account for conditions and depend on the other ingredients that are usually natural in high-fat products, no shelf-life problems occur." Shelf-life conditions might expose ice creams to higher-than-recommended storage temperatures. With controlled temperature conditions, the flavors should perform well, with no off-flavors developing. As long as the other ingredients used, such as dairy components, are in good, fresh condition at the time of manufacturing, the ice cream should deliver a desirable profile at the time of consumption.

  In addition to flavors, ice cream manufacturers also use ice cream bases. "Flavor bases are generally cooked products, which could be egg bases, cheesecake bases, chocolate syrups or fruit purees," says Greg McClatchy, product manager, Universal Flavors, St. Louis, MO. "These bases can be added to the mix either before or after pasteurization." Since they are pasteurized, they have reasonable shelf life. They can be added to the mix and pasteurized again, or with proper hygienic handling, can be blended into the chilled aging tank. "It's efficient to add different flavor bases to divisions of a common ice cream mix batch," says Dave Watson, manager, product development, frozen desserts, Universal Flavors, Dairy Division, St. Louis, MO.

Go coconuts

  A product worth considering in an indulgent ice cream for functional and flavor attributes is coconut concentrate, which is a fine, desiccated particulate, reduced to 20 µm. "It improves the viscosity of the ice cream itself, according to Fe Reyes, director, Baker's Coconut, Kraft Food Ingredients' (KFI) R&D, San Pablo, Philippines. "It can substitute for milkfat up to 100%, providing a cost savings."

  "At this level, the crystal stability is excellent, and overrun can be 110%," says Dante Dumaraos, product development manager, KFI R&D. On absorbing water, the product swells, and has a good, creamy mouthfeel. Substitution of at least 50% is recommended to provide a minimum effect on ice-crystal regulation. Viscosity will be medium at this level. A 25% substitution adds no coconut flavor to the ice cream. The concentrate is compatible with any flavor at that level.

  "We found that at 10% replacement of milkfat, the coconut has a tendency to round out flavors," says Mary Taylor, associate business manager, Baker's Coconut, KFI, Memphis, TN. "It becomes more of a flavor booster than an actual presence in the profile." In addition to being an interesting flavor for ice creams, alone or with chocolate, pineapple and many other flavors, the flavor-modifying effect is quite useful. The 10% substitution of coconut concentrate for milkfat provides rounding, mellowing and definition to flavors like lemongrass, chocolate and ginger for some exotic flavor effects.

Soda fountain of youth

  Indulgence can be coupled with health by incorporating ingredients that might provide new flavor categories and phytochemicals. Fruits in themselves provide a wealth of health in their anthocyanins, beta-carotene and other pigments. Green-tea ice cream has been around a long time, with its healthful antioxidants.

  In the botanical area, taste and use level are important considerations. "At 10% of the U.S.P. (U.S. Pharmacopeia), flavors and matrices provide enough masking," says Forouz Ertl, vice president, technology and regulatory, Botanicals International, Long Beach, CA. "The bitterness of some botanicals, such as gingko, can be covered with masking agents, flavors and the matrix." In Europe, where botanical extracts have been used in more recent years in a number of foods, the German Pharmacopeia recommends use of about 10% of the effective level of a botanical for food products. "Scientifically, I would not recommend going over 25% of the U.S.P.," Ertl says, "due to multiple doses liable to be encountered in the diet from different foods during the day."

  There are numerous ingredients, such as fruit and fruit preps for vitamins, phytochemicals and colors. Botanical extracts, soluble or fine suspended powders, can be added to the mix, as long as the particle size is small enough not to add grittiness to the ice cream.

Variegate variety

  Variegates are another way to add flavor and color variety to indulgent ice creams. Available are fruit syrups - including pieces and purees - chocolate and compound coating syrups, caramel and fudge compositions, and blends of ingredients including everything from nut butters to coffee syrups.

  These high-solids products are added to the partially frozen ice cream or frozen dessert coming from the freezer, where they are injected with a variegate pump using nozzles that can produce various patterns and swirls in the product as it is packaged.

  "Variegates are cooked products in a stabilized sugar solution," Watson says. "Indulgent-type products tend toward a more natural ingredient statement. Generally, in variegates at 55% to 65% total solids, natural stabilizers like pectins are a little more difficult to work with, as it is somewhat more difficult to control viscosity. In variegates, pectins, locust bean gum, xanthan gum and modified starches are used. At the low levels used, it is more difficult to control viscosity, since they're more sensitive to other ingredients in the mix. Small changes can affect viscosity levels. More control must be exercised in choice of ingredients and levels. Indulgent products tend to use citrus and apple pectins rather than xanthan gum."

  Fruit preparations add high value as well as nutritional value to indulgent ice creams. Smaller pieces provide discrete pieces throughout the packaged product. Larger pieces at lower counts would not be as appealing. In any case, the fruit feeder auger might restrict fruit piece size. Fruit preps for indulgent ice creams tend to have higher fruit levels than those for regular ice creams due to cost factors. Use levels can be as high as 50 lbs. of fruit prep per 35 gallons of ice cream mix. Fruit preps often contain sugar, citric or malic acid, thickeners such as pectins, xanthan gum or modified food starches, preservatives including sodium benzoate and potassium sorbate, and added color. Fruit preps need to be chosen that are workable with the ice cream product. Any adverse effects on the ice cream due to sugars, acids, thickeners and colors should be determined. Viscosity changes, melt and other structural properties, sensory changes or color and flavor bleed require modifications or selection of different preps. Label requirements may require formulation without some additives, such as preservatives.

  Aseptic packaging gives good fruit-piece texture, color and flavor due to HTST pasteurization as compared to retorted products. Heat processing kills microorganisms, so they can be held at 55° to 75°F (12.8° to 23.9°C), with a 12-month shelf life.

  Individually quick-frozen fruits also are used. The products have been frozen using liquid nitrogen, and quality can be very good, due to the small ice crystals forming as a result of the quick-freezing.

  Variegates require tempering prior to pumping into the soft frozen ice cream from the freezer. A fudge might require warming at a suitable temperature to a viscosity at which the variegating pump can deliver the fluid into the ice cream with the texture that will yield the desired swirl pattern and consistency. A chewy caramel variegate stored at 35° to 45°F might have to be tempered at ambient temperature prior to use to attain the correct viscosity throughout the container. The variegate must not be so warm that significant ice cream melting occurs before hard-packing is achieved. The variegating sauce also must not be exposed to warm temperatures for too long a time prior to use or it might be subject to spoilage.

  Some products, like ambient-temperature fruit preparations, have to be pre-chilled to a cold temperature that will allow addition via variegating pump or fruit feeder in a pattern or blend required, without melting the frozen mix or bleeding juices into the frozen product.

  The pH of either variegates or inclusions will not usually curdle protein if the products are blended at cold temperatures and hardened quickly. Should a problem become evident, a buffer such as a citrate could be used or the acidity of the additive reduced.


  Inclusions include pieces, shavings or chunks of chocolates, compound coatings, nuts, cookies, cake and other baked items, and fruits and fruit preparations of many kinds. Beyond unique flavor creations and combinations, inclusions are the departure point into the truly unruly and unrivaled world of the creative imagination. Almost anything edible and credible can end up as an inclusion. Cookies, cookie doughs, candies of many types, donut pieces, fruit pieces of every type, biscotti and other wafers - all have found their way into indulgent ice creams.

  "One of our best sources when determining new flavors for our ice cream add-ins is to look for hot trends in desserts," says Subha Luck, industrial sales manager, Rhino Foods, Inc., Burlington, VT. "We visit high-end restaurants and bakeries and test their dessert items. Since tiramisu is a hot dessert right now, we have developed a baked cake ice cream add-in that tastes like tiramisu." She adds that market research, focus groups and "good old intuition" also generate valuable concepts.

  Among the many choices, the king of inclusions might be chocolate - rich, creamy and indulgent by its very nature. Containing 52% cocoa butter and 48% cocoa solids, the ingredient can be supplied as milk chocolate, dark semisweet chocolate, white chocolate (consisting primarily of cocoa butter and sugar) or chocolates flavored with liqueurs, oils and extracts.

  "A technical reason why one chocolate might be better is that we have one blend of beans used to make our chocolate," says Jim LaRosa, vice president, specialty ingredients, Ghirardelli Chocolate Company, San Leandro, CA. "We remove the shell by passing them through a micronizer, obtaining the nibs. Nibs are the shelled bean, which are hard and not greasy, even though high in fat. The fat is entrapped in the cocoa fibers. Grinding the shelled blend to a small uniform particle, we roast the particles to a uniform deep roast, with no shell burn-on. The shell can also give an off-flavor. Then, the deep-roasted nib blend goes through a series of high-shear blenders, and then ball mills. The result is the chocolate liquor product. This is the same product as the cocoa nibs blend, but is now a liquefied product." The chocolate liquor is refined for the final chocolate products, or it is sold for formulation into various coatings.

  Genuine chocolate has a standard of identity, in that no fats other than cocoa butter are allowed. Typically, indulgent ice creams will have real milk-, dark- or white-chocolate pieces as inclusions. "Maintaining the desired texture of chocolate is a challenge," Watson explains. "In genuine chocolate, increasing solids and water activity is all that's available."

  Compound-coating bits can be used for different textures. Made from refined palm, soy or cottonseed oils that have been partially hydrogenated, these contain longer-chain, non-lauric fats, chosen for physical characteristics close to cocoa butter. They also can be made by esterification of glycerol with selected fatty acids. Cocoa liquor may be used with non-lauric fats. MSNF are usually used to prevent fat incompatibility. When frozen, lower melting-point fats give a softer, chewier compound. Higher melting-point fats provide chips that are more crunchy.

  To formulate an indulgent, but less-caloric ice cream with chocolatey inclusions, product designers might consider a compound made with the reduced-calorie fat, salatrim. Scientists at Cultor Food Science, Ardsley, NY, have adapted the confectionery version of this fat to produce chips and variegates for ice cream applications. Because the fat calories are lower in the salatrim product than in chocolate or standard compound coating, the fat level in the ice cream base or the level of inclusions can be increased - both of which spell indulgence - without a significant rise in calorie count.

  Many premium ice cream products have a nutty theme - praline, black walnut, chocolate-covered almond, spumoni - the list seems endless. Nuts provide flavor, crunch and visual appeal along with an upscale cachet.

  The variety of nut used is typically a matter of flavor. For example, according to the Walnut Marketing Board, the flavor of walnuts is synergistic with fruits, chocolate, vanilla, mocha, liqueur and more. They might be part of an exotic flavor such as Indian kulfi ruh gulab, an ice cream that combines walnuts and rose essence.

  No matter what the combination, designers need to consider the type, size and level of nut to use. They can be raw, blanched or oil- or dry-roasted. With almonds, for example, "roasted products are the most popular by far," says Sam Cunningham, Ph.D., director, quality control and R&D, Blue Diamond Growers, Sacramento, CA. "Oil-roasting is most typical. Roasting enhances the flavor of the nut." The time and temperature of the roast determines the resulting color and flavor. A darker roast would catch the eye in a light-colored ice cream base, while a lighter roast might be more visually appealing in a dark fudge base.

  Oil-roasting also provides the nuts with additional resistance to moisture migration since the oil can slow any water absorption. Other water-resistance films can be used, such as zein, various gums, food-grade waxes and even chocolate. However, the low water activity and hydrophobicity of most nuts helps maintain a soft crunch in ice cream without additional coatings.

  A larger nut or piece has two benefits: it helps preserve the desirable crunch by exposing less surface area to pick up moisture and it enhances the visual aspects of the ice cream. "You don't often see a sliced almond in ice cream," says Cunningham. "With a very thin piece, you'll get water absorption from both sides and it will get soggy. Most premium ice creams use a large whole nut; most fall in the 20s count-per-ounce range. Almonds are sized in fairly narrow, count-per-ounce ranges - a large nut would be 18 to 20, and sizes would go down to 40 to 50 per ounce. You could also use a half-almond, or split, or a slivered almond."

  According to the Walnut Marketing Board, the optimum level of walnuts to add to ice cream is about 7%. A typical range would be between 5% to 10%. No matter what the type of nut, the object in formulating, especially in a high-quality product, is to try to ensure a nut or piece in each bite of ice cream. This leads to weighing the advantages or disadvantages between cost and size (count per ounce). Given a 5% target level, is it best to have more pieces or larger pieces?

  The bake shop provides inspiration for many ice cream inclusions. These fit into a wide range of different categories: doughs, and high- or low-moisture bits. These can be baked, formed with a cooker-extruder or merely extruded. "The main characteristic of extruded pieces is the texture, which is almost fudge-like since they are usually unbaked," explains Alice Schramm, senior food technologist, Rhino Foods. "This is a desirable characteristic in items like cookie doughs, truffles, fudge brownies, etc., but you are limited to items that taste good with that texture. The advantage to baked add-ins is that now you can create different-textured pieces for ice cream, from cookies to cakes, to even pretzels. The drawback is that the moisture content on baked pieces is so low that sooner or later - usually sooner - the pieces pick up moisture from the ice cream and become soggy.

  "One way to control moisture migration is to coat your piece in chocolate," Schramm says. "This provides a moisture barrier between the add-in and the ice cream." Other moisture-barrier technologies, such as those listed for nut coatings, also might help the pieces. Another option is to reformulate to provide a high-fat piece that resists moisture pickup.

  On the other hand, some moisture migration may contribute to the desired texture. "For our tiramisu piece, since the cake in a tiramisu dessert is actually soaked in espresso, the moisture migration helps give the piece a more authentic taste and mouthfeel," Schramm explains.

  High moisture add-ins might solve the problems associated with moisture problems, but they might provide additional challenges. For example, one consideration is how the piece will work with production equipment, especially fruit feeders. Schramm recommends a corn-starch coating for cookie dough to prevent the pieces from sticking together or clumping in the fruit feeder.

  "There are a large variety of cookie doughs," says Schramm. "There's no reason why your mom's top-secret chocolate-chip-cookie recipe wouldn't work as a dough for ice cream." This would entail a few minor changes, she notes. For example, no leavening agents would be required for a dough. Also, since many ice cream manufacturers would add their own chips to the ice cream, many cookie-dough inclusions have less chips than traditional cookie doughs.

  Another thing to be alert for with an uncooked piece - whether dough or something else - is any potential microbial problem. This means a close watch on microbial load or methods to treat the potential problem before it occurs, such as the use of pasteurized eggs in cookie dough.

  Lastly, it's important that any ice cream inclusion, especially some of the more fragile baked pieces or delicate fruits or candies, maintain their shape. They must be durable enough to withstand the trip through the fruit feeder into the package and then into the consumer's mouth.

  "The most obvious, and important factor to consider when using inclusions in ice cream is taste," Schramm says. "There is a fine line between a great product and too much or too little add-ins in the ice cream. It is a real art to determine a harmonious blend between ice cream and the inclusions."

  The high path to adventure lies in designing new and extraordinary indulgent ice creams that will keep consumer interest in the category from cooling down. "There are a lot of companies trying to figure out the craziest ingredients to put into ice cream," observes Ted Castle, founder and president, Rhino Foods. "What needs to be considered when developing a new concept is whether it's innovative, tastes great and, most importantly, makes people want to eat the product again and again."

Whey Proteins at Work  Ice crystals large enough to be detected by the tongue result in a negative perception of ice cream's quality. This is particularly true for premium varieties, which are expected to be ultra smooth and creamy - the creamier an ice cream, the more decadent its character.

  Therefore, controlling the growth of ice crystals is key to formulating the foam-and-emulsion concoction known as ice cream. The smaller the ice crystals in the mixture, the better the texture and mouthfeel.

  A recent research project led by David E. Smith, Ph.D., professor of food science and nutrition, the University of Minnesota, St. Paul, and a researcher at Minnesota-South Dakota Dairy Foods Research in Minneapolis, indicates that the concentration of denatured whey protein in ice cream influences the development of ice crystals. Ice creams made with higher concentrations of beta-lactoglobulin whey protein, and processed at increased temperatures, tend to have reduced initial ice-crystal growth, and are less icy over time compared to ice creams made with alternative solids, the research indicates.

  The research, funded by Dairy Management Inc., Rosemont, IL, also indicates that using whey proteins and/or higher processing temperatures not only enhances storage stability, but can reduce the necessary amount of stabilizing agents such as carrageenan, xanthan or other gums. "While not eliminating the need for hydrocolloid stabilizers, changes in ice cream formulation and processing help reduce the amount of stabilizers required," Smith explains.

  This information could prove valuable not only to those looking to create smooth-textured, indulgent ice creams, but also for those looking to ensure a clean label. "There is a manufacturer preference for using natural dairy protein as part of the stabilizer system," Smith says, "instead of ingredients with names that are unpronounceable and unfamiliar to consumers."

Heidi L. Kreuzer

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