SLA 2011: Science of Ice Cream

Science of Ice Cream

Thomas Palchak · Berkey Creamery Manager , Pennsylvania State University

(Yes, I should probably be in the session about alternate uses of library degrees, but, hey, this talk is about *ice cream*!)

Process manufacturers think about ingredients different from consumers.

Historical: Crystalline sugar dates from Persia (627AD), refining was used in Egypt, Mesopotamia, and Spain.
Development of beet sugar in the 19th century caused prices to drop, so the public could afford sugar.
Ice cream arrived in America with the British colonists.
* 1774: record of Dolly Madison serving ice cream at the White House. Ice cream was largely developed in the US.
* 1843, Nancy Johnson got patent #3254 for the first ice cream freezer.
* 1851, Jacob Fussell established the first ice cream plant in Baltimore. Fussell improved on Johnson’s design.
* 1892 Pennsylvania State College offered ice cream manufacturing instruction
* In WWII, Mussolini thought ice cream was American enough to ban its sale
* Ice cream production = 1.6 billion gallons
* New Zealand consumes ~26 quarts per capita. US gets ~24.
* Ice cream has gone from being a royal treat to being egalitarian

Characteristics: frozen when eaten, melts, tastes sweet, aroma suppressed until melting releases it, creamy and smooth, appearance important, various flavors (PSU creamery makes more than 150 flavor; vanilla is the most popular flavor)

FDA standards of identity: consumers know product meets standards and is safe to eat
* not less than 10% milk fat (creaminess) and not less than 20% total milk solids
* must contain at least 1.6 pounds of total solids per gallon
* must weigh at least 4.5 pounds per gallon
* frozen custard is at least 1.4% egg yolk solids
* must be frozen under agitation (prevents spoilage)
* must be pasteurized
* sweeteners much be “safe and suitable” (or meet approval)

* mix of air, water, milkfat, solids, sweeteners, stabilizers, emulsifiers, and flavors -> colloid
* mix is the unfrozen blend of ingredients without air and flavoring -> everything else is pasteurized
* standards vary throughout the world

Frozen Dairy desserts: ice cream, frozen custard, reduced fat (at least 50% less than standard ice cream), lite (1/3), lowfat, nonfat (.5% or less), gelato (can contain nothing but fruit juice and still be gelato), bulky flavored ice cream, sherbet (no more than 2% milk fat, but it must contain 10% milk fats -> sherbet is dairy), ice milk (fading away, 7-10% fat, came about during WWII food rationing), soft serve, mellorine (vegetable oil instead of milk fat), paravine (vegetable oil), frozen yogurt (no standard), water ice, frappe, italian ice, sorbet/sorbetto

Ingredient roles
* milk fat satisfies legal definition, adds richness, flavor, synergist for added flavor compounds, smooth texture, desired melting properties, lubricates the palate, improves insulating properties (the higher the fat, the warmer the ice cream feels -> no ice cream headache, chilled teeth)
** two kinds of ice cream eaters: biters and lickers

Nonfat milk solids
* enhance texture, increased chew resistance, prevents snowy/flaky texture
* protects against “heat shock”
* milk proteins contribute to structure development (ability to foam). Ice cream is about 50% air
* added solids prevent coarse/icy defects

liquid/dry ingredients -> blending -> pasteurization -> homogenization -> cooling -> aging ->

* sweeten and enhance flavors
* lack = flat taste; too much will overshadow desirable flavors
* sugars do not dissociate in solution
* the body breaks high-fructose corn syrup down into sucrose and glucose, same as other sugars. There’s no difference between HFCS and other sugars as far as your body is concerned.

Children under 2 should not consume honey -> pasteurization issue. Honey is not frequently found in ice cream because of texture issues.

Stabilizers and emulsifiers
* group of ingredients
* added in small amounts (<0.4%
* increase mix viscosity
* produce a stable foam
* melt resistance
* smoothness in texture
* slows moisture migration
* firm ice cream
* aids suspension of ingredients
* improve whipping quality
* produces dry, stiff ice cream

Water and air
* ice crystals <4 microns at start (The human tongue can perceive 20 microns of ice.)
* water is the solvent: present as liquid and solid
* due to solutes, it never completely freezes

* taste includes texture/”feel sensation” as well as flavor
* blending of flavors is important: few extra grams of vanilla can make it mediciney
* Subjective
* Preference for delicate over harsh -> recognizable, but not overwhelming

* vanilla is king, fruit flavors are second, chocolate is 8th, but added to other flavors, is ranked higher
* aseptic processing provides sterility and improved quality
* best source of flavor
* extracts from prepared fruit, artificial flavors, and extracts with added artificial flavors
* added after agitation and first freezing

Color -> if it looks good, it sells
* delicate and attractive
* readily suggests ice cream flavor
* must be certified (FD&C) and declared on product label
* can’t use “natural color” in ingredients or description: “color added” or “artificial color”

* 0-8% milkfat
* 14-24% sugar
* 4-12% SMS
* 32-42% total solids
* 58-68% water

Someone asked about the “frozen dessert” designation and that Canada has a icon of a cow for dairy desserts. A: In PA, same issue. If it sells, it must be okay as a dessert, no problem with it not being dairy as long as the company is honest about that.

Pasteurization: the process of heating every particle of milk or milk product to the minimum required temperature and holding it continuously for the required time -> destruction of vegetative pathogenic microorganisms present in milk or dairy product; different kinds of pasteurization: high temp/short time -. same results with all of them

Homogenization: uniformly distributes fat -> important part of texture; reduces milkfat globules’ size, changes the nature of the surrounding membrane Thomas says homogenized ice cream is high quality ice cream. [How many of us homogenize our home-made ice cream, yet consider that to be higher quality than what we can buy in the store?]

Aging of ice cream mix
* mix cooled to <4 degrees C, <40 degrees F
* 4 to 24 hours
* allows milkfat to crystallize
* nearly complete crystallization is needed to promote coalescence of fat globules during ice cream freezing–think of butter left out and how it’s still shaped like a rectangle

Milk is sticky and will stick in the back of the throat, hence the mucousy sensation that happens with dairy products.


What happens in the ice cream freezer?
* crystallization of water
* air is whipped in
* milkfat forms clumps and crystals
* water freezes, solutes are concentrated
* air expressed as % overrun -> increases the volume of the mix due to incorporation of air
* 1 liter of mix yields

Dasher is the beater that spins in an ice cream churn. It’s razor sharp in commercial productions.

Continuous freezers
* home-made ice cream is 20-40% air
* ammonia or freon

* public institution, public recipe
* 14.1% milkfat
* 12.5% solids
* 3.7% dry corn syrup solids (conversion of corn sugar into dextrose)
* 12.96% cane sugar
* .26% stabilizer
email him to get the creamery formula adapted for home use

Q: No difference between sweeteners? Why use cane sugar?
A: Purest form of sweetener. Leaves no aftertaste. Corn syrup has an aftertaste and allergen concerns.

Microbial food safety
* Milk: perishable, easily contaminated, must be refrigerated
* Ice cream: not a sterile product, does not contain harmful bacteria, must be pasteurized, post-pasteurization is a concern

Microorganisms in raw milk
* sterile after milking
* transfer during transport

Spoilage organisms
* coliforms
* pseudomonas
* pathogens: Yersinia, Listeria, E. coli,
Run a blacklight over milk to check for some bacteria

5 states make 50% of US milk: Wisconsin, California, Minnesota, Pennsylvania, New York.
4 dairies in WV, 8 in NE, 5 in MS, 3 WY, 8 MT, 9 NV, 10 NM, 8 NH

Microbiology of ice cream
* properly frozen, little microbes occur
* wash hands

Sensory evaluation: flavor, body and texture, color/appearance/package, melting …
terms: slight, definite, pronounced, unsalable

Milk and Ice Cream
* nutritious growth media

top sellers:
vanilla, fruit flavors,

ice cream will usually allow 2 good unfreezings and refreezings and recover

Q: why does the creamery disallow flavor mixing?
A: it’s a line issue: too many people

Q: what about Iceland and ice cream consumption?
A: Scandinavian countries love their ice cream. PSU’s ice cream freezers come from Denmark. College students drink milkshakes and eat ice cream as soon as the dairy shop opens at 7 am, winter, summer …

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