How ice cream is made and why you so addicted to it

Science Oct 15, 2020

Ice cream (derived from earlier iced cream or cream ice) is a sweetened frozen food typically eaten as a snack or dessert. It may be made from dairymilk or cream and is flavoured with a sweetener, either sugar or an alternative, and any spice, such as cocoa or vanilla. Colourings are usually added, in addition to stabilizers. The mixture is stirred to incorporate air spaces and cooled below the freezing point of water to prevent detectable ice crystals from forming. The result is a smooth, semi-solid foam that is solid at very low temperatures (below 2 °C or 35 °F). It becomes more malleable as its temperature increases.

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Before the development of modern refrigeration, ice cream was a luxury reserved for special occasions. Making it was quite laborious; ice was cut from lakes and ponds during the winter and stored in holes in the ground, or in wood-frame or brick ice houses, insulated by straw. Many farmers and plantation owners, including U.S. Presidents George Washington and Thomas Jefferson, cut and stored ice in the winter for use in the summer. Frederic Tudor of Boston turned ice harvesting and shipping into a big business, cutting ice in New England and shipping it around the world.

A Boku Europa ice cream maker in Aachen, Germany

Ice cream was made by hand in a large bowl placed inside a tub filled with ice and salt. This is called the pot-freezer method. French confectioners refined the pot-freezer method, making ice cream in a sorbetière (a covered pail with a handle attached to the lid). In the pot-freezer method, the temperature of the ingredients is reduced by the mixture of crushed ice and salt. The salt water is cooled by the ice, and the action of the salt on the ice causes it to (partially) melt, absorbing latent heat and bringing the mixture below the freezing point of pure water. The immersed container can also make better thermal contact with the salty water and ice mixture than it could with ice alone.

The hand-cranked churn, which also uses ice and salt for cooling, replaced the pot-freezer method. The exact origin of the hand-cranked freezer is unknown, but the first U.S. patent for one was #3254 issued to Nancy Johnson on 9 September 1843. The hand-cranked churn produced smoother ice cream than the pot freezer and did it quicker. Many inventors patented improvements on Johnson's design.

In Europe and early America, ice cream was made and sold by small businesses, mostly confectioners and caterers. Jacob Fussell of Baltimore, Maryland was the first to manufacture ice cream on a large scale. Fussell bought fresh dairy products from farmers in York County, Pennsylvania, and sold them in Baltimore. An unstable demand for his dairy products often left him with a surplus of cream, which he made into ice cream. He built his first ice cream factory in Seven Valleys, Pennsylvania, in 1851. Two years later, he moved his factory to Baltimore. Later, he opened factories in several other cities and taught the business to others, who operated their own plants. Mass production reduced the cost of ice cream and added to its popularity.

The development of industrial refrigeration by German engineer Carl von Linde during the 1870s eliminated the need to cut and store natural ice, and, when the continuous-process freezer was perfected in 1926, commercial mass production of ice cream and the birth of the modern ice cream industry was underway.

In modern times, a common method for producing ice cream at home is to use an ice cream maker, an electrical device that churns the ice cream mixture while cooled inside a household freezer. Some more expensive models have an built-in freezing element. A newer method is to add liquid nitrogen to the mixture while stirring it using a spoon or spatula for a few seconds; a similar technique, advocated by Heston Blumenthal as ideal for home cooks, is to add dry ice to the mixture while stirring for a few minutes. Some ice cream recipes call for making a custard, folding in whipped cream, and immediately freezing the mixture. Another method is to use a pre-frozen solution of salt and water, which gradually melts as the ice cream freezes.

Borden's Eagle Brand sweetened condensed milk circulated a recipe for making ice cream at home. It may be made in an ice cube tray with condensed milk, cream, and various simple flavourings. It can be ready to serve after as little as four hours of freezing. Fresh or frozen fruit, nuts, chocolate, and other ingredients may be added as well.

An unusual method of making ice cream was done during World War II by American fighter pilots based in the South Pacific. They attached pairs of 5-US-gallon (19 l) cans to their aircraft. The cans were fitted with a small propeller, this was spun by the slipstream and drove a stirrer, which agitated the mixture while the intense cold of high altitude froze it. B-17 crews in Europe did something similar on their bombing runs as did others.

Ingredients and standard quality definitions

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Many countries have regulations controlling what can be described as ice cream.

In the U.S., the FDA rules state that to be described as "ice cream", a product must have the following composition:

  • greater than 10% milk fat
  • 6 to 10% milk and non-fat milk solids: this component, also known as the milk solids-not-fat or serum solids, contains the proteins (caseins and whey proteins) and carbohydrates (lactose) found in milk

It generally also has:

  • 12 to 16% sweeteners: usually a combination of sucrose and glucose-based corn syrup sweeteners
  • 0.2 to 0.5% stabilizers and emulsifiers
  • 55 to 64% water, which comes from the milk or other ingredients.

These compositions are percentage by weight. Since ice cream can contain as much as half air by volume, these numbers may be reduced by as much as half if cited by volume. In terms of dietary considerations, the percentages by weight are more relevant. Even the low-fat products have high caloric content: Ben and Jerry's No-Fat Vanilla Fudge contains 150 calories (630 kJ) per half-cup due to its high sugar content.

According to the Canadian Food and Drugs Act and Regulations, ice cream in Canada is divided into  Ice cream mix and Ice cream. Each have a different set of regulations.

  • Ice cream must be at least 10 percent milk fat, and must contain at least 180 grams of solids per litre. When cocoa, chocolate syrup, fruit, nuts, or confections are added, the percentage of milk fat can be 8 percent.
  • The ice cream mix is defined as the pasteurized mix of cream, milk and other milk products that are not yet frozen. It may contain eggs, artificial or non-artificial flavours, cocoa or chocolate syrup, a food colour, an agent that adjusts the pH level in the mix, salt, a stabilizing agent that doesn't exceed 0.5% of the ice cream mix, a sequestering agent which preserves the food colour, edible casein that doesn't exceed 1% of the mix, propylene glycol mono fatty acids in an amount that will not exceed 0.35% of the ice cream mix, and sorbitan tristearate in an amount that will not exceed 0.035% of the mix. The ice cream mix may not include less than 36% solid components.

Why do we love eating ice-cream so much?

The main reason is sugar. Below I will describe why is sugar a highly addictive substance that makes us eating not just only ice-cream in huge quantities but almost every our favorite snacks that you like enjoying with a cup of tea or morning coffee.

It has a somewhat addictive combination of fat and carbohydrates (sugar) wich makes food very palable because our brain identify it as very easy and high source of energy. The brain rapidily becomes upset when we eat only sugar or fat. People usually don’t like to eat pure sugar, butter or drink oil, but we like very much that combination in food like: ice cream, cookies, donuts, cakes, chocolates and even breads.

Is sugar a potentially addictive substance?

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The  FA  literature  considers  sugar  (and  other  refined  carbohydrates) to be a key facet of processed foods with high addictive  potential,  contributing  to  their  GL  (dose)  and  their  rapid  rate  of  absorption.  Within  this  context,  discussion  of  sugar  has  centred  on  its  palatability  or  hedonic  value; however, unlike substances of abuse, sugar has both hedonic  and  caloric  value,  and  these  two  aspects  broadly  map  onto  ingestive  and  post-ingestive  effects  of  its  consumption,  respectively.  Moreover,  these  aspects  are  distinct and dissociable in terms of their neural processing as demonstrated  in  two  elegant  sets  of  experiments.  Domingos et al. showed that melanin-concentrating hormone (MCH)-expressing neurons located within the lateral hypo-thalamus respond to extracellular glucose levels and project to dopaminergic (DA) neurons in the striatum and midbrain regions.  The  animals  show  a  preference  for  sucrose  over  the  non-nutritive  sweetener,  sucralose,  and  the  glucose-sensing  ability  of  these  neurons  is  critical  in  determining  this, as transgenic mice lacking MCH neurons do not show this  preference.  MCH  neurons  encode  the  rewarding  nutrient  properties  of  sucrose  by  increasing  striatal  DA  release independently of gustatory input. Optogenetic stimulation  of  MCH  neurons  during  consumption  of  sucralose  leads to striatal DA efflux and preference for sucralose over sucrose.

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Recently, Tellez et al. expanded upon this work by examining  DA  transmission  in  the  striatum  in  response  to  oral  sucralose  intake  versus  intra-gastric  glucose  or sucralose  administration.  Using  microdialysis,  the  authors  reported  changes  in  DA  release  in  the  ventral  and  dorsal  striatum,  where  regional  DA  release  selectively  encoded  the  pleasurable  and  nutritional  value  of  the  sweet  foods.  Sucralose  consumption  was  linked  to  enhanced  DA  efflux  in the ventral striatum (VS), which was no longer observed following  devaluation  of  the  sweetener  with  a  bitter  additive.  Conversely,  intra-gastric  infusion  of  glucose,  but  not  sucralose,  elicited  DA  release  in  the  dorsal  striatum  (DS).  Thus,  the  VS  and  DS  appear  to  encapsulate  functionally  distinct responses to palatable and nutritive signalling, and the authors went on to delineate the role of D1 and D2 striatal  DA  neurons  in  palatability  and  nutrient  preferences.  Dopaminergic  signalling  excites  D1  DA  neurons  while  inhibiting  their  D2  DA  counterparts,  and  this  interaction  modulates  the  control  of  goal-directed  actions,  including  overeating. Optogenetic stimulation of D1 DA neurons within the DS and substantia nigra terminals increases consumption  of  a  bitter  sucrose  solution,  which  supports  the  dorsal basal ganglia pathway as a circuit that is selectively responsive  to  the  nutrient  properties  of  sugar  reward. It should be noted, however, that the role of MCH, D1 DA, and D2 DA neurons has yet to be explored in animal models of sugar addiction, so whether the aforementioned neural circuits reflect processes underlying addictive-like sugar consumption remains unknown.This experimental work allows us to consider that addictive-like  properties  of  sugar  may  occur  via  three  neural  mechanisms: one related to palatability and the reinforcing effects  of  sweet  taste,  another  related  to  caloric  value  and  post-ingestive  effects,  and  a  third  arising  from  a  combination  of  the  two  effects.  Put  simply,  the  critical  ‘addictive’  quality  of  sugar  may  be  restricted  to  its  sweetness,  nutritional  value,  or  some  combination  of  the  two.  Of  course,  only the third possibility would support sugar as addictive, particularly within Schulte et al.’s model where highly processed foods with added sugar would be very sweet, energy dense,   and   rapidly   absorbed   and   therefore   potentially   have  a  characteristic  profile  of  ingestive  and  post-ingestive  effects.  Nonetheless,  as  humans  often  consume  sugar  in  combination  with  other  nutrients,  differences  between  highly processed foods with high and low addictive potential would need to be characterised. Indeed, Zeevi et al. demonstrated  that  the  same  foods  can  have  very  different  post-ingestive profiles in different individuals. This may be a  critical  factor  and  one  aspect  of  individual  vulnerability  to  a  potentially  addictive  food.  These  are  theoretical  considerations as thus far little work in humans has examined them  directly.  The  animal  literature  does,  however,  offer  some experimental evidence of parallels between sugar and drugs. We consider this in the next section, beginning with a  brief  overview  of  the  neurobiological  characteristics  of  drug addiction.

Research: Sugar addiction: the state of the science.