Glossary

POD Potere Dolcificante

Relative sweetening power. The sweetness of a sugar, measured against sucrose at 100. In English this property is called relative sweetness.

PAC Potere Anti-Congelante

Relative anti-freezing power. How strongly a sugar resists the freezing of water, measured against sucrose at 100. In English, the effect it measures is called freezing-point depression. It is the measure by which the softness of gelato is designed.

DE (dextrose equivalent)

A measure of how far a starch has been hydrolyzed. Dextrose is 100 and starch is 0. The higher the DE, the lower the average molecular weight, and the higher the POD and PAC of the glucose syrup. The form matters as well: the dried form holds nearly 100 % solids, the liquid form about 80 %.

MSNF (milk solids-not-fat) solidi del latte non grassi

The part of the milk solids left after the fat is removed. It consists of protein, lactose, and minerals, and it carries the frame of gelato and holds the air bubbles. It is also called serum solids. The limit on raising it is set by the solubility of lactose.

lactose lattosio

The only sugar in milk. A disaccharide of glucose and galactose. Its solubility is low, about one twelfth that of sucrose, and an excess produces the defect called sandiness. POD 16, PAC 100.

casein caseina

The main protein of milk. In milk it is present as calcium caseinate, and it coagulates with acid at around pH 4.5. In a strongly acidic mix it can be a cause of sandiness.

unfrozen phase

The liquid phase that stays unfrozen even in the freezing range. Sugar and other solutes remain dissolved in it. It is the reason gelato is cold and still soft.

emulsion emulsione

A state in which one of two liquids that do not mix is dispersed through the other as fine droplets. In a mix, fat globules are dispersed through the water phase; it is an oil-in-water emulsion.

corpo

The sense of weight, the density, and the melting behavior of gelato. It is set mainly by the recipe — the amount and the composition of the solids.

struttura

The fineness and the smoothness of the texture of gelato. It is set mainly by the process — the control of freezing, hardening, and storage. It is the counterpart of corpo.

balancing bilanciamento

The design work of separating a mix into its components: sugar, fat, MSNF, other solids, and water. Their proportions are then brought into the target ranges.

total solids solidi totali

The sum of everything in the mix other than water. What remains is the water. It is a basic measure, governing both the texture of gelato and how well it keeps.

mix

The liquid base, before freezing. It combines the milk, sugar, flavor ingredients, and stabilizers of the recipe. The mix is pasteurized, aged, and then sent to the mantecatore. The recipe is fixed at this stage. Every later step can change only how the ice and the air bubbles form.

pasteurization pastorizzazione

Heat treatment that kills pathogenic bacteria and reduces spoilage bacteria. Spores survive the heat, so the mix is cooled rapidly afterward. A lower temperature requires a longer holding time. (For Japan's legal minimum, see Ch. 6.)

homogenization omogeneizzazione

The step that uses mechanical force to break the fat globules fine and disperse them evenly. It stabilizes the emulsion, and it raises both corpo and the ability to whip.

aging maturazione

The step that rests the pasteurized mix at about 4 °C for several hours. Protein binds water, and part of the fat crystallizes. Together they build the foundation of a smooth texture.

mantecazione

Freezing with agitation. The step that freezes the mix while adding air, and keeps the ice crystals small.

roasting tostatura

Heating nuts and similar ingredients to develop their aroma and flavor. Coldness dulls flavor in gelato, so a somewhat darker roast is often preferred.

HACCP Hazard Analysis and Critical Control Point

Hazard Analysis and Critical Control Point. A method of food hygiene that prevents hazards by controlling every step, rather than by inspecting the finished product. The points where hazards are most likely — the critical control points — are monitored and recorded continuously.

mantecatore

The machine that performs mantecazione. A blade scrapes the ice from the inner wall of the chilled cylinder, while air is added at the same time. There are vertical and horizontal types.

blast freezer abbattitore

The machine that performs hardening. It chills the gelato leaving the mantecatore to about −22 °C in a short time. The critical temperature zone, where ice crystals grow, is therefore crossed quickly.

overrun

The amount of air incorporated during freezing. It is expressed as the percentage increase in volume over the mix.

sorbetto

A frozen dessert made without milk, from water, sugar, and fruit. Sugar supplies nearly all of the solids, so the design of the sugar decides the quality.

granita

A frozen dessert made with almost no agitation, so coarse ice crystals remain. Its sugar content is low, about 17–21 °Bx in solution.

degrees Brix (°Bx) gradi Brix

The proportion of soluble solids in a solution, read as roughly the weight percent of sugar. It is measured with a refractometer. In sorbetto design it is the basic measure of how much sugar a fruit carries.

hardening indurimento

The step that fixes the structure. At the exit of the mantecatore only about half of the water is frozen. A blast freezer then cools the gelato quickly to about −22 °C.

critical temperature zone

The temperature range in which ice crystals grow most readily, from the freezing point (about −2 to −3.5 °C) down to −8 °C. How fast this range is crossed, in freezing and in hardening, decides how fine the texture becomes. This book uses this name for the range; it is not a standard term.

recrystallization ricristallizzazione

The growth of ice crystals during storage, driven by changes in temperature. With each change, water passes from small crystals to large ones. It is the main cause of the coarsening that happens after the gelato is made.

stabilizers addensanti

Polysaccharides and similar substances that bind free water and give the mix viscosity. They restrain the coarsening of ice crystals and the separation of water (syneresis). Locust bean gum, guar gum, and pectin are examples. In English, the word thickeners usually names the viscosity effect alone; this book uses stabilizers for the whole group.

emulsifiers emulsionanti

Substances that carry both a water-loving group and an oil-loving group. They gather at the boundary between water and fat, and govern how the fat globules behave. Lecithin and mono- and diglycerides are examples.

syneresis sineresi

Water separating from a gel or a mix and seeping to the surface. Stabilizers restrain it.

gelato

Italian for "the frozen thing". The general name for the frozen desserts born in Italy. Gelato holds less air and less fat than ice cream, and it is served at a slightly higher temperature. This is why it tastes rich without feeling heavy.

gelateria

A shop that makes gelato and sells it. In most of them the mix is prepared daily in a workroom at the back. The gelato is displayed on the day it is made.

crema

The family of gelato built on milk. Its character is richness and a satisfying feeling. Some cremas add egg yolk for still more richness. Crema is the counterpart of sorbetto.

fiordilatte

The basic crema flavor, in which milk itself is the taste. The quality of the ingredients appears directly.

glucose syrup sciroppo di glucosio

A mixture of sugars obtained by hydrolyzing starch. Its behavior follows from the DE. A low-DE syrup neither sweetens nor softens; it adds solids alone, and works as a structural material.

locust bean gum (LBG) farina di semi di carruba

A stabilizer obtained from the seeds of the carob tree. It is the most versatile of the stabilizers, and holds 80 to 100 times its own weight in water. Full hydration, however, requires heat.

lecithin lecitina

A natural emulsifier, present in egg yolk among other sources. It is amphiphilic, and it mediates between water and fat.

refractometer rifrattometro

The instrument that measures degrees Brix. In sorbetto design it is used to measure the sugar of the day's fruit directly.

colligative properties proprietà colligative

Properties that depend only on the number of dissolved particles. Freezing-point depression is one of them. At equal weight, a sugar of lower molecular weight gives more particles, and so a higher PAC.

freeze concentration crioconcentrazione

The process by which water leaves the unfrozen phase as ice, so the solutes left behind grow denser. This is why gelato has no single point at which it turns liquid. It is also why gelato grows harder continuously as the temperature falls.

supercooling sottoraffreddamento

The state of a liquid that has passed below its freezing point without freezing. How far below it goes decides how fast ice crystals are born and how fast they grow.

nucleation nucleazione

The birth of the first seeds of ice crystals. The deeper the supercooling, the more seeds appear at once. For the same amount of ice, each crystal then stays smaller.

Ostwald ripening maturazione di Ostwald

Small crystals are less stable than large ones, so their molecules move to the large ones. The large grow at the expense of the small. The total amount of ice does not change, and yet the texture coarsens. It is a main cause of coarsening in storage.

heat shock shock termico

Damage to the texture caused by swings in temperature. Each time the temperature rises and falls, small crystals disappear, and their water freezes onto the large crystals that remain. Every round leaves the texture coarser.

hydration idratazione

The hydroxyl groups of a polysaccharide draw water by hydrogen bonds and hold it in place. It is the first step by which a stabilizer binds water. How readily hydration proceeds depends on whether the chains associate with one another.

shear thinning pseudoplasticità

The property by which viscosity falls under strong force, so the material flows more easily. At rest it holds water; inside the mantecatore and in the mouth it flows. An older name for this property is pseudoplasticity.

yield stress sforzo di soglia

The greatest force a material can bear while still holding its shape like a solid. Beyond it, the material flows. Yield stress is the physical substance of scoopability.

scoopability spatolabilità

The property of flowing moderately when pressed with a spatula. It is determined by the yield stress: too high and the gelato is stiff, too low and it slumps.

rheology reologia

The study of how matter flows and deforms. With viscosity, yield stress, and viscoelasticity, it turns melt into something that can be measured.

partial coalescence coalescenza parziale

Partly crystallized fat globules link through the points of their crystals and form clusters without merging completely. This builds the network of fat that supports the air bubbles. Emulsifiers are used to encourage it in moderation.

casein micelle micella caseinica

A particle of casein and calcium phosphate, roughly 100 to 200 nm across. Hairs of κ-casein on its surface create repulsion and keep the particles apart. This is what makes milk look white and cloudy.

sandiness sabbiosità

A defect felt as sand on the tongue. It comes mostly from lactose crystallizing in excess, and it arises from two sides at once: too much MSNF, and swings in storage temperature.

α-lactose monohydrate

The form lactose takes when it crystallizes below 93.5 °C. It holds water of crystallization, and its crystals are hard, angular, and slow to redissolve. It is the physical substance of sandiness.

retronasal olfaction

The path by which the aroma of food in the mouth passes from the throat to the nose and is sensed there. In cold gelato the aroma sensed from outside through the nose — orthonasal olfaction — is weak. The aroma that opens as the gelato warms in the mouth is where flavor is decided.

glass transition temperature (Tg) transizione vetrosa

The temperature at which the unfrozen phase becomes too viscous to flow, and its solute molecules lose the freedom to move. In ice cream it lies roughly between −30 and −40 °C, depending on the recipe, and the composition of the unfrozen phase decides it. Below this temperature, recrystallization stops on any practical timescale. Even above it, the nearer the temperature comes, the slower the change. This is not a true phase change like freezing. It is a question of whether molecules can move.

critical radius

The radius that decides whether a new seed survives. A seed smaller than this breaks apart and disappears. Above it, growth lowers the energy, so the seed keeps growing. Deeper supercooling makes the radius smaller, and seeds form more easily.

heterogeneous nucleation

Nucleation that starts on a surface that is already present, such as a speck of dust or the wall of a vessel. Fewer molecules are needed than to build a seed from nothing, so seeds form even under shallow supercooling. The cold wall of the mantecatore acts as such a surface.

disproportionation sproporzionamento

Air passes from small bubbles to large ones through the liquid between them. The small bubbles vanish and the large ones grow. The cause is that the pressure inside a bubble rises as the bubble gets smaller. The mechanism mirrors Ostwald ripening in ice.

Laplace pressure

The difference in pressure across a curved surface. The smaller the radius, the larger the difference. A small bubble therefore holds a higher pressure inside, and its air dissolves more readily into the liquid. This is what drives disproportionation.

hydrophobic effect effetto idrofobico

Fat crystals and other water-repelling molecules gain energy by being surrounded by oil rather than by water. In partial coalescence, this is what drives a crystal projecting from one globule to enter a neighboring globule and stay there.

SFC (solid fat content)

The proportion of the fat that is crystalline at a given temperature. At 0 % the fat is entirely liquid; at 100 % it is entirely solid. Partial coalescence happens at neither extreme, and proceeds best in between. Choosing the temperature of aging is choosing this proportion.

polymorphism polimorfismo

One fat can take several crystal forms, differing in how the molecules pack. Stability runs β > β′ > α. The barrier to forming a nucleus is low, however. Fat therefore crystallizes often in a metastable form, and shifts to a stable one over time. How readily a form appears and how stable it is are two different things.

mutarotation mutarotazione

The shift between the α and β forms of lactose in water, until the two reach equilibrium. When lactose dissolves, mutarotation raises the amount that will dissolve. When lactose crystallizes, it keeps replacing the less soluble α form as that form leaves the solution, and so feeds the growth of crystals. The same mechanism works in opposite directions on the way in and on the way out.

partition coefficient coefficiente di ripartizione

How an aroma molecule divides between the gas phase and the liquid phase. The larger it is, the stronger the aroma. It falls as the temperature falls, so cold gelato is already at a disadvantage at the first stage of releasing aroma.

oil–water partition coefficient

Whether an aroma molecule prefers fat or water. Above 1 it is hydrophobic; below 1, polar. As fat increases, only the hydrophobic aromas find it harder to reach the gas phase, while the polar ones barely change. Fat hides only the aromas that dissolve in it.

pasteurized liquid egg

Hen eggs broken from the shell into liquid form and then pasteurized. In Japan, the standard requires them to test negative for Salmonella. Using them releases the maker from the heating otherwise required for foods that contain egg. Unpasteurized liquid egg carries only a limit on bacterial count, and is an ingredient that assumes the user will heat it.

matrix matrice

The medium itself, which holds the aroma molecules and the particles. In gelato it means the system as a whole: the fat globules, the water phase, and the boundary between them. The more strongly the matrix holds an aroma, the less of it reaches the gas phase. This is why the same amount of flavoring rises differently when the base changes.

volume ratio (R_V)

How many times larger the effective volume a polymer occupies in solution is than the volume of the chain itself. For a molecule coiled into a sphere the ratio is about 1. For an extended chain it can reach billions. At the same molecular weight, a linear chain gives a larger ratio and a branched one a smaller ratio. This is why a stabilizer works in so small an amount.

overlap concentration (c*)

The concentration at which polymer chains begin to touch one another. It is inversely proportional to the volume ratio, so a bulkier molecule reaches it at a lower concentration.

semi-dilute regime

The range of concentration in which polymer chains already act on one another, while each is still surrounded mostly by solvent. It lies above the overlap concentration and below the entanglement concentration. A stabilizer in a liquid mix is usually here.

entanglement concentration

The concentration at which entanglement begins. It lies above the overlap concentration. A stabilizer in the unfrozen phase, after freeze concentration, is usually past it.

entanglement

Polymer chains that have penetrated one another and can no longer slip past. They are not tied together, so a strong force separates them again. This is what shear thinning is. It differs on this point from a gel held by chemical cross-links.

viscoelasticity viscoelasticità

The property of showing viscosity and elasticity at the same time. Part of an applied force is stored in deformed bonds (elasticity), and the rest is lost as heat through friction (viscosity). The stored part is measured as the storage modulus, the lost part as the loss modulus. Firmness is what the tongue reads from this division.

The seven entries that follow name what you sense when eating gelato. They follow three moments: when it enters your mouth, while it melts, and after it is gone. They are words for sharing what you notice — not a standard, and not a scale of quality. If your own words describe it better, use your own words.

coldness

One of the seven tasting words. First moment — when the gelato enters the mouth. Coldness is the low temperature the tongue receives at that instant. The colder it is, the more it is felt as an edge. A lower serving temperature also suppresses aroma and lowers perceived sweetness, and each sugar is suppressed to a different degree. Coldness is a matter of mouthfeel and of the strength of the taste at the same time.

grain

One of the seven tasting words. First moment — when the gelato enters the mouth. Grain is the sense of particles felt the instant the tongue touches the gelato. Roughness divides into two kinds. Icy grain comes from ice crystals that have grown large. Sandy grain comes mostly from lactose crystals, and is the same thing this book calls sandiness. When neither is present, the grain is smooth.

melt

One of the seven tasting words, also called melt in the mouth. Second moment — while the gelato melts. Melt is the speed at which it disappears in the mouth. The ratio of ice to unfrozen phase and the serving temperature act first. Fat, air bubbles, and the viscosity and yield stress of the unfrozen phase are added to them. Melt is an integrated sensation: flow, melting, and the release of aroma proceed together on the tongue.

firmness

One of the seven tasting words. Second moment — while the gelato melts. Firmness is the resistance felt when the gelato is pressed. It flows when pressed and stops when the force is released, and firmness is the tongue's reading of that behavior. In physical terms it corresponds to viscosity, yield stress, and viscoelasticity. Scoopability names the same yield stress seen from the spatula rather than from the mouth; the two words share the physical quantity, not the character of the word. Firmness is not corpo, which names weight, density, and melting behavior.

onset

One of the seven tasting words. Second moment — while the gelato melts. Onset is the time aroma and sweetness take to appear in the mouth. What the cold suppressed opens late, as the gelato warms. Onset covers two things. One is the retronasal aroma that passes from the throat to the nose. The other is the sweetness that returns as the temperature rises. Each sugar also has its own shape in time, and that shape is added to the effect of temperature.

aftertaste

One of the seven tasting words. Third moment — after the gelato is gone. Aftertaste is what remains in the mouth after swallowing. The most common example is the thin film that fat leaves on the surface of the tongue. Aftertaste is a question of how much remains. Length, which asks how long the taste continues, is a separate word.

length

One of the seven tasting words. Third moment — after the gelato is gone. Length is how long the taste continues after swallowing. It is not only a tail that fades. Sweetness and aroma that the cold suppressed also return once the gelato has melted completely. Length is a question of time. Aftertaste, which asks what remains, is a separate word.

post-harvest ripening maturazione della frutta

The process by which a fruit continues to ripen after it is picked. Pectin becomes soluble and the flesh softens; fructose is formed and the fruit sweetens; aromatic esters are formed and the aroma rises. Only fleshy fruits have this ability. Citrus stops the moment it leaves the tree.

protopectin

The pectin of unripe fruit, which does not dissolve in water. It glues the plant cells to one another. As post-harvest ripening proceeds, enzymes turn it into soluble pectinic acid — pectin in the narrow sense. The cells, no longer glued, separate, and the flesh softens. Past ripeness it degrades further into pectic acid, which again does not dissolve in water.

pozzetti

A way of storing and serving gelato in lidded cylinders sunk into a coolant. It was once the standard at the counter, but display cases replaced it because the contents cannot be seen. In recent years its merits are returning, in forms that combine a sealing lid with visibility.

carapina

The cylindrical container used to receive, store, and serve gelato. Gelato taken from the mantecatore is transferred into it first.