- Ice creams are dairy-based frozen foods usually consumed as snacks or desserts. Federal regulations or standards of identity stipulate that ice cream must contain a minimum of 10% milk fat and 20% total milk solids by weight.
- A school of thought opines that ice cream started as a luxury desert in the ancient Roman Empire between A.D 54–68. It was believed that Roman Emperor Nero Claudius Caesar used slaves to gather snow in the mountains, which was subsequently flavored with fruits and juices to make ice cream.
- Between 2000 and 2020, at least 88 ice cream-associated outbreaks were reported to CDC’s National Outbreak Reporting System (NORS), causing 1,150 illnesses, 92 hospitalizations, and 5 deaths.
- In ice cream, bacteria, parasites, toxins, and viruses can cause spoilage and foodborne disease. Pathogenic microorganisms commonly responsible for ice cream outbreak incidents include Escherichia coli O157:H7, Listeria monocytogenes, Salmonella, and Campylobacter jejuni.
Ice cream is a common dessert product that is produced through the pasteurization and homogenization of blended dairy products, (typically milk, condensed milk, butterfat, and cream). Other ingredients such as sweetening agents, flavorings, stabilizers, emulsifiers, colorings are also added to the mix. Occasionally, fruits, nuts, variegates, candy pieces, and other condiments are added to make a desired ice cream flavor. The process then involves freezing the mixture and incorporating air. The addition of air is called overrun and contributes to the lightness or denseness of ice cream. Without air, ice cream would be similar to a frozen ice cube. The ice cream is then placed into its packaging container. Finally, ice cream is cooled down to a holding temperature of less than -13°F (-25°C) as quickly as possible.
The origins of ice cream are thought to date back to the Roman Empire (A.D. 54-86) where Nero Claudius Cesar would send runner to fetch snow in the mountains to be flavored with fruit and juices. Sherbet was brought to Italy by Marco Polo leading to the recipe being modified to ice cream some time in the 16th century. Ice cream may have been developed in England at the same time or before the Italians. The dessert was brought to America in the late-1700s and it remained a rare item consumed by the elite through the mid-1800s. The industry soon began to grow as steam power, refrigeration, homogenizers, and new freezing technologies helped improve ice cream production and efficiency. By the 1900s ice cream was widely available in supermarkets and parlors throughout the United States, steadily growing to the current production of approximately 1.6 billion gallons per year.
Foodborne Outbreaks and Recalls
Ice cream related foodborne disease is a pervasive problem caused by consuming contaminated ice cream products. Between 2000 and 2020, at least 88 ice cream-associated outbreaks were reported to CDC’s National Outbreak Reporting System (NORS), causing 1,150 illnesses, 92 hospitalizations, and 5 deaths. One of the earliest cases of food borne illnesses related to ice cream was traced to selected ice cream products from Schwan’s Sales Enterprises of Marshall, Minnesota in 1994. This incident was reported to have occurred from Salmonella – related contamination, when raw unpasteurized eggs were hauled in a tanker truck that later carried pasteurized ice cream mix to the Schwan’s plant. This outbreak was traced to about 740 people in 30 states. The outbreak was suspected to have sickened over 3,000 additional people in as many as 41 US states.
In 2005 a multi-state outbreak of Salmonella Typhimurium occurred in Cold Stone Cake Batter Ice Cream. The outbreak infected 25 people across nine states, leading to four hospitalizations and no reported death Investigation into the outbreak found that Gold Metal Super Moist cake mix that is included as an ingredient was the source of contamination, wherein 24 of the 25 cases reported eating the cake batter ice cream which shared a cream base with other flavors of ice cream. Cold Stone Creamery issued a recall of this flavor in response to the outbreak.
In 2015, a multi-state outbreak event was reported due to Listeria monocytogenes contamination of ice cream processed at Blue Bell Creameries. Ten people with listeriosis related to this outbreak were reported from four states: Arizona (1), Kansas (5), Oklahoma (1), and Texas (3). All ill consumers were hospitalized, and three deaths were reported from Kansas. Investigation into the outbreak identified various ice cream products produced on the same production line as sources of Listeria contamination. On April 20, 2015 Blue Bell creameries recalled all products from shelves and warned consumers to suspend the purchase or consumption of the brand’s ice cream products and dispose of products they have already purchased. As consequence of the outbreak, the former president of Blue Bell Creameries, Paul Krause, was charged with wire fraud and conspiracy in connection with a scheme to cover up the company’s sale of the contaminated products. The company was additionally sentenced to pay $17.25 million in criminal penalties related to two counts of distributing adulterated food products.
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Causes of Contamination
Bacteria, parasites, toxins, and viruses can cause spoilage and foodborne disease in ice cream. Pathogens typically responsible for ice cream outbreak incidents include Escherichia coli O157:H7, Listeria monocytogenes, Salmonella, and Campylobacter jejuni. These microorganisms are known to multiply rapidly at standard holding temperatures and conditions for ice cream, heightening the likelihood of a severe outbreak. Symptoms of such microbial contamination may include abdominal pain, backache, chills, diarrhea (both bloody and not), fatigue, fever, and headache, nausea, and malaise. These symptoms usually become apparent 2 to 5 days after ice cream is eaten, and last about 8 days, however depending on the pathogen and infectious dose, symptoms can manifest within 12 hours or up to 3 weeks after ingestion. Serious illness can result from foodborne disease, including Hemolytic Uremic Syndrome (HUS) that causes acute kidney failure has developed in very young consumers. A similar illness, thrombotic thrombocytopenic purpura (TTP), may occur in older. Meningitis and spontaneous abortions in pregnant women can also occur. If left untreated these severe effects can lead to death.
Finished ice cream products may be contaminated with microorganisms at any time; during manufacturing, freight, point of sale, and in consumer homes. Pathogens can be found in the intestinal tracts of animals and birds, in raw dairy products, untreated water, and dirt and sewage sludge. Contact with any of the listed items or with an ill person can result in contamination and/or illness. In manufacturing locations improperly processed ice cream or contaminated ingredients and inappropriately cleaned equipment can also provide suitable environments for pathogens.
In order to prevent ice cream outbreaks, manufacturers need to ensure good food handling and processing practices, eliminate all possible routes of contamination, and maintain adequate freezing temperatures. Likewise, personal hygiene of manufacturers, and workers, as well as improved methods of decontamination of consumer products could significantly reduce the extent of morbidity and mortality of due to ice cream contamination.
Ice cream is manufactured via the following steps: blending of ingredients, pasteurization, homogenization, aging of the mix ingredients, freezing, packaging and hardening.
Blending and Pasteurization
Blending consists of selecting the appropriate ingredients and corresponding amounts for a particular flavor of ice cream and blending them together using high speed blenders to create the “ice cream mix.” The mix is then pasteurized using either a batch or continuous pasteurizer. In the former method, blending of ingredients is done in large jacketed vats, where the mix is heated with steam or hot water to 69° C (155°F) for about 30 minutes, or any temperature high enough to destroy pathogens and reduce bacterial count to a max of 100,000 per gram. An advantage to batch pasteurization is its ability to denature high amounts of whey protein, which is believed to provide the ice cream better body. Continuous pasteurization is performed in a high temperature short time heat (HTST) exchanger after ingredients are blended in an insulated feed tank. The equipment consists of stacked steel plates framed in a way that allow for various flow patterns to be used. This method also can also use steam or hot water as its heating medium. The advantage to this process is that it is both more time and energy efficient than the batch method. Regardless of the method used, pasteurization is done for two important reasons: to destroy pathogenic bacteria and to reduce the number of spoilage organisms (i.e. psychrotrophs).
Homogenization and Aging
Homogenization of ice cream mix is typically a two-stage process that takes place at the pasteurizing temperature. Using a high temperature allows for the formation of fat emulsion via efficient reduction of (i.e. milk, cream) globules, resulting in a thinner more easily whipped mix. A two-stage homogenizer usually requires pressure values of 2000 – 2500 psi and 500 – 1000 psi on the first and second stage, respectively to provide satisfactory results. However, it is important to bear in mind that greater amounts of solids and fat in a mix will require a lower pressure. Among other benefits, process also allows for the use of essential ingredient such as butter and frozen cream. Ice cream also becomes smoother, richer, more palatable, and more resistant to melting. The next step consists of aging the mix, usually done overnight in an insulated or refrigerated storage tank, silos, etc. The mix is maintained at a temperature as low as possible without freezing, at or below 5°C. During this time fat cools down, crystallizes and allows for complete hydration of proteins and polysaccharides for a small increase in viscosity. This step further improves the mix’s whipping quality, as well as the texture and body of the product. After processing, the mix is placed in flavor tank where colors, purees, or other liquid flavors are added.
The freezing process consists of freezing both a portion of the water and whipping air into the frozen mix to give ice cream its characteristic lightness. Mix is pumped through a “barrel” freezer and drawn in about 30 seconds, or 10-15 minutes using a batch freezer. During this process ingredients such as fruit, nuts, candy, cookies is added to the semi-frozen ice cream. A barrel freezer is heat exchanger with a scraped-surface covered with a boiling refrigerant, like ammonia or Freon. Rotating blades in the barrel keep ice off the freezer’s surface and dashers within it are used to help whip the mix. Providing air to the mix provides ice cream its lightness. Ice cream is packaged and placed into a blast freezer at -30° to -40°C where most of any remaining water is frozen. At temperatures lower than -25° C, ice cream is stable for indefinite periods of time; however, ice crystal growth at higher temperatures is possible and will limit shelf life.
Hardening involves rapid-rate static freezing of packaged products in blast freezers. Temperatures in this process are low, around -40°C with either enhanced convection (freezing tunnels with forced air fans) or enhanced conduction (plate freezers). Hardening is effected by several factors including but not limited to: the temperature of the blast freezer, the colder it is will result in a faster the hardening and a smoother the product, the temperature of the ice cream when hardening began, the colder it was initially, the faster it will harden. A container’s size should maximize surface area to cold air and be stacked in a way that does not impeded air circulation, (i.e. no dead air spaces).
Studies have shown that many cases of ice cream foodborne illness begin with under-processed and/or unpasteurized dairy products. Pasteurization is a key step in commercial ice cream processing; the pasteurization process applies heat to the ice cream mix and destroys pathogens that may be present. If ice cream is homemade, it is recommended that pasteurized milk and/or cream be utilized for optimal safety. Raw or undercooked ingredients have also been associated to foodborne illness outbreak, as such they should not be used without pasteurization in the production of ice cream either commercially or in the home.
Allergen contamination is another food safety concern in ice cream production. Food allergies provoke the immune system to react against foods it identifies as harmful. Allergic reactions can be life threatening. Most ice cream products contain milk, as one of the big eight allergens, so those who are allergic to milk, milk-containing products, or lactose intolerant should pay special attention to the milk allergen content of ice cream. Additionally, it is not uncommon for ice cream to contain added fruits, nuts, bulky flavorings, or ingredients containing tree nuts, peanuts, milk, eggs, soy, wheat, and corn products. Some consumers may be allergic to these added ingredients. Regulations demand that commercial ice cream manufacturers declare allergens in their product. It is strongly advised that consumers understand the labeling of their ice cream and be sure there are no risks of allergenic reactions in their choice of ice cream.
The following steps aim to help consumers store ice cream safely and in a way that retains quality:
- At the grocery store, the ice cream aisle the last stop of the shopping trip
- Check the temperature of the grocer’s freezer case. The temperature in the supermarket’s freezer case should not be above -20°F. If the freezer is kept at a proper temperature, ice cream will be thoroughly frozen and hard to the touch. If the product is soft, it should be brought to the attention of the store manager.
- Insulate ice cream products with other groceries for the ride home.
- Make the grocery store or ice cream parlor the last errand before going home to ensure ice cream does not sit in a warm car while making other stops.
- At home, ice cream should be stored in the very back of the freezer at a temperature between -5°F and 0°F. Freezer settings should be adjusted to maintain this temperature.
- Ice cream should not be left out of the freezer unnecessarily, nor should it be repeatedly softened and refrozen. When ice cream’s small ice crystals melt and re-freeze, they eventually turn into large, unpalatable lumps.
- To reduce the formation of ice crystals, keep the ice cream container lid tightly closed when putting it back in the freezer.
- Do not store ice cream alongside uncovered foods; odors may penetrate ice cream, affecting its flavor.
- The ideal serving temperature range is between 6°F and 10°F.
Whether consumers are buying ready-to-eat ice cream from the grocery stores, visiting an ice cream parlor, or making ice cream from scratch, one thing they should know about ice cream storage, is that ice cream hates changes in temperature. Frozen desserts exposed to temperatures above 10°F, are subject to adverse changes in body, texture, and flavor characteristics. Every time ice cream increases in temperature, some of the ice crystals trapped within it begin to melt. This is not a problem if the ice cream is eaten right away, but upon re-freezing partially-melted ice cream, ice crystals re-form, bigger and crunchier, robbing the ice cream of its creaminess.
Ice cream can be purchased as a large carton as well as individually wrapped frozen novelties that include ice-cream sandwiches, ice cream cones, chocolate-dipped bars, Klondike bars, and popsicles. The average American consumes almost 22 pounds of ice cream per year, which is equal to 26 liters (45.8 pints). Despite this high consumption, New Zealand is the world leader in per capita ice cream consumption at 28.4 liters. Approximately 87% of Americans have ice cream in their freezers at any given time, where Sunday is the most common day for American’s to purchase ice cream. Vanilla is America’s favorite ice cream flavor, followed by Chocolate Chip Mint, and Cookies and Cream. Chocolate syrup is the most popular topping. Given the high demand for ice cream, 9% of all milk produced in the U.S. is used to make the frozen dessert. There is a wide variety of options beyond regular ice cream, shown below. While regular ice cream is the most common variety, its consumption reduced 9% between 2000 and 2018 whereas low-fat ice cream consumption increased by 20%.
Regular ice cream – a frozen food made from a mixture of dairy products, containing at least 10 percent milk fat.
Light or lite ice cream contains at least 50 percent less total fat or 33 percent fewer calories than the referenced product.
Low-fat ice cream contains a maximum of 3 grams of total fat per serving (½ cup).
Nonfat ice cream contains less than 0.5 grams of total fat per serving.
Frozen Custard or French ice cream must also contain a minimum of 10 percent milk fat, and at least 1.4 percent egg yolk solids.
Sherbets have a milk fat content of between 1 and 2 percent, and weigh a minimum of 6 pounds to the gallon.
Sorbet and Water Ices are similar to sherbets, but do not contain dairy ingredients.
Frozen Yogurt consists of a mixture of dairy ingredients such as milk and nonfat milk that have been cultured, as well as ingredients for sweetening and flavoring.
Ice creams are dairy-sourced frozen foods usually consumed as snacks or desserts. Federal regulations or standards of identity stipulate that ice cream must contain a minimum of 10 percent milk fat and 20 percent total milk solids by weight.
One serving of ice cream ½ cup, which for regular ice cream contains approximately 140 calories, 7 grams of fat, 14 grams of added sugar, and 2 grams of protein. Ice cream is considered a high-calorie food due to both its high calorie and high fat content for the small serving size. In addition, ice cream is high in saturated fat; high intake of saturated fat has been associated with increased risk of developing cardiovascular disease and type 2 diabetes, however the link between dairy fat and heart disease risk is an ongoing area of debate. Ice cream is considered a good source of calcium and phosphorous, containing 10% daily value per serving. While ice cream can be part of a balanced diet, its high palatability increases the likelihood of overconsumption and increased daily energy intake.
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