History
Our love affair with ice cream is centuries old. The ancient Greeks, Romans, and Jews were known to chill wines and juices. This practice evolved into fruit ices and, eventually, frozen milk and cream mixtures. In the first century, Emperor Nero reportedly sent messengers to the mountains to collect snow so that his kitchen staff could make concoctions flavoured with fruit and honey. Twelve centuries later, Marco Polo introduced Europe to a frozen milk dessert similar to modern sherbet that he had enjoyed in the Far East. The Italians were especially fond of the frozen confection that by the sixteenth century was being called ice cream. In 1533, the young Italian princess Catherine de’ Medici went to France as the bride of the future King Henry II. Included in her trousseau were recipes for frozen desserts. The first public sale of ice cream occurred in Paris at the Café Procope in 1670.
Frozen desserts were also popular in England. Guests at the coronation banquet of Henry V of England in the fourteenth century enjoyed a dessert called cremefrez. By the seventeenth century, Charles I was served cream ice regularly. Eighteenth-century English cookbooks contained recipes for ice cream flavoured with apricots, violets, rose petals, chocolate, and caramel. Other early flavourings included macaroon and rum. In early America, George Washington and Thomas Jefferson were especially fond of ice cream. Dolley Madison was known to serve it at White House state dinners.
Because ice was expensive and refrigeration had not yet been invented, ice cream was still considered a treat for the wealthy or those in colder climates. (In a note written in 1794, Beethoven described the Austrians’ fear that an unseasonably warm winter would prevent them from enjoying ice cream.) Furthermore, the process of making ice cream was cumbersome and time-consuming. A mixture of dairy products, eggs, and flavourings was poured into a pot and beaten while, simultaneously, the pot was shaken up and down in a pan of salt and ice.
The development of ice harvesting and the invention of the insulated icehouse in the nineteenth century made ice more accessible to the general public. In 1846, Nancy Johnson designed a hand-cranked ice cream freezer that improved production slightly. The first documented full-time manufacturing of ice cream took place in Baltimore, Maryland, in 1851 when a milk dealer named Jacob Fussell found himself with a surplus of fresh cream. Working quickly before the cream soured, Fussell made an abundance of ice cream and sold it at a discount. The popular demand soon convinced him that selling ice cream was more profitable than selling milk.
However, production was still cumbersome, and the industry grew slowly until the industrialisation movement of the early twentieth century brought electric power, steam power, and mechanical refrigeration. By the 1920s, agricultural schools were offering courses on ice cream production. Trade associations for members of the industry were created to promote the consumption of ice cream and to fight proposed federal regulations that would call for selling ice cream by weight rather than volume, and the disclosure of ingredients.
The Prohibition era proved to be very profitable for the ice cream industry. Denied alcoholic beverages, many people ate ice cream instead. Breweries were often converted to ice cream factories, although it is likely that some of the plants were merely fronts for illegal liquor sales. Although the repeal of Prohibition in 1933 and the ensuing depression slowed ice cream sales, the industry continued to grow. The film industry was especially instrumental in the promotion of ice cream, and scenes depicting stars enjoying the frozen concoctions were plentiful. Ice cream parlours sprang up in every town, and the parlour employee—the so-called soda jerk—developed into a cultural icon.
After the Second World War, with raw materials readily available again, the ice cream industry produced over 20 qt (19 l) of ice cream for each American per year. During the 1950s, competition sprang up between the ice cream parlour and the chemist (drugstore) that sold packaged ice cream. It was during this time that usage of lesser-quality ingredients increased. Many producers were adding very low percentages of butterfat and pumping large quantities of air into the ice cream to fill out the carton.
The 1970s saw the development of gourmet ice cream manufacturers with an emphasis on natural ingredients. People also became interested in making ice cream at home. Upscale restaurants began offering homemade ice cream on their dessert lists.
Raw Materials
Today, ice cream is made from a blend of dairy products (cream, condensed milk, butterfat), sugar, flavourings, and federally approved additives. Eggs are added for some flavourings, particularly French vanilla. The broad guidelines allow producers to use ingredients ranging from sweet cream to non-fat dry milk, cane sugar to corn syrup solids, and fresh eggs to powdered eggs. Federal regulations stipulate that each package of ice cream must contain at least 10% butterfat.
The additives, which act as emulsifiers and stabilisers, are used to prevent heat shock and the formation of ice crystals during production. The most common additives are guar gum, extracted from the guar bush, and carrageenan, derived from sea kelp or Irish moss.
Ice cream flavours have come a long way from the standard vanilla, strawberry, and chocolate. By the 1970s, the International Association of Ice Cream Manufacturers had recorded over 400 different flavours. In an ever-expanding array of combinations, fruit purées and extracts, cocoa powder, nuts, biscuit pieces, and cookie dough are blended into the ice cream mixture.
Air is added to ice cream to improve its ability to absorb flavourings and to facilitate serving. Without air, ice cream becomes heavy and soggy; too much air results in a snowy, dry texture. The federal government allows ice cream to contain as much as 100% of its volume in air (known as overrun).
Makers of high-quality (gourmet) ice cream use fresh whole dairy products, a low percentage of air (approximately 20%), 16–20% butterfat, and as few additives as possible.
The Manufacturing Process
Although ice cream is available in many forms (including novelties such as chocolate-dipped bars and sandwiches), the following describes ice cream packaged in pint and half-gallon containers.
Blending the mixture
The milk arrives at the ice cream plant in refrigerated tanker trucks from local dairy farms. It is pumped into 5,000 gal (18,925 l) storage silos kept at 36°F (2°C). Pipes bring the milk in pre-measured amounts to 1,000 gal (3,785 l) stainless-steel blenders. Pre-measured amounts of eggs, sugar, and additives are blended with the milk for six to eight minutes.
Pasteurising to kill bacteria
The blended mixture is piped to the pasteuriser, composed of a series of thin stainless-steel plates. Hot water, approximately 182°F (83°C), flows on one side of the plates while the cold milk mixture passes on the other. The water warms the mixture to 180°F (82°C), effectively killing bacteria.
Homogenising for a uniform texture
Using intensive pressure—sometimes as much as 2,000 psi (≈141 kg/cm²)—the hot mixture is forced through a small opening into the homogeniser. This breaks down fat particles and prevents separation. In the homogeniser (a high-pressure piston pump), the mixture is further blended as it is drawn into the pump cylinder on the downstroke and forced back out on the upstroke.
Cooling and resting to blend flavours
The mixture returns to the plate heat exchanger where cold water at approximately 34°F (1°C) cools it to 36°F (2°C). It is then pumped to 5,000 gal (18,925 l) tanks in a room set at 36°F (2°C), where it rests for 4–8 hours to allow flavours to blend.
Flavouring the ice cream
The ice cream is pumped to stainless-steel vats, each holding up to 300 gal (1,136 l). Flavourings are piped in and blended thoroughly.
Freezing to soft-serve consistency
The mixture is pumped into continuous freezers that can process up to 700 gal (2,650 l) per hour. The temperature inside the freezers is kept at -40°F (-40°C), using liquid ammonia as the refrigerant. While in the freezer, air is injected. When the mixture leaves, it has the consistency of soft-serve ice cream.
Adding fruit and sweet inclusions
If pieces (e.g., strawberry or biscuit/cookie chunks) are to be added, the semi-frozen mix is pumped to a fruit feeder. Chunks are loaded into a hopper at the top, and a starwheel meters pre-measured amounts into the flow. A blender then distributes inclusions evenly.
Packaging and bundling the finished product
Automatic filling machines drop pre-printed pint or half-gallon cartons into holders and fill them at 70–90 cartons per hour. Lids are applied and cartons move along a conveyor belt, passing under an inkjet that prints the expiry date and production code. The cartons then pass through a bundler (heat tunnel) that shrink-wraps each unit.
Hardening
Before storage and shipping, ice cream is hardened to -10°F (-23°C). A conveyor moves cartons through a hardening tunnel set at -30°F (-34°C). Constantly turning ceiling fans create a wind-chill of -60°F (-51°C). Over 2–3 hours, the contents reach a rock-solid state. Cartons are then stored in refrigerated warehouses until shipment.
Quality Control
Every mixture is tested during production. Butterfat and total solids are measured, bacterial levels are monitored, and each batch is taste-tested. Producers also closely monitor all incoming ingredients from suppliers.
The Future
Manufacturers continue to develop new flavourings. Ironically, given the industry’s experiences during Prohibition, one recent innovation has been the introduction of liqueur-flavoured ice creams.