2026 QRC Food Tech Review: Food Chemistry

Comprehensive vocabulary flashcards covering the history, components, and chemical reactions discussed in the Food Chemistry review lecture.

Food Chemistry

A major aspect of food science dealing with the composition, properties, and chemical changes of food during handling, processing, and storage.

Carl Wilhelm Scheele

A chemist who isolated and studied lactose from milk, malic acid from apples, and citric acid from lemons.

Antoine Laurent Lavoisier

A pioneer in food chemistry who first demonstrated that fermentation can be represented by a balanced chemical equation.

Justus von Liebig

He classified foods as nitrogenous (albumin, casein, vegetable fibrin, animal flesh, and blood) or non-nitrogenous (fats, carbohydrates, and alcoholic beverages).

Water Activity ($a_w$)

A measure of the availability of water for biological and chemical reactions, defined as the ratio of vapor pressure of water in food ($P$) to the vapor pressure of pure water ($P_0$) at the same temperature ($a_w = \frac{P}{P_0}$).

Free Water

Water that can be readily extracted from foods by squeezing, cutting, or pressing, and can act as a solvent or freeze at moderate temperatures.

Bound Water

Water that is not easily extractable, does not function as a solvent for salts and sugars, and exhibits virtually no vapor pressure.

Sorption Isotherm Region I

The region representing strongly bound monolayer water, which is the most difficult to remove and least mobile.

Hard Water

Water that is high in dissolved minerals, primarily calcium and magnesium.

Monosaccharides

The simplest sugars or monomeric units with the general formula $C_n(H_2O)_n$ that cannot be hydrolyzed into smaller carbohydrates.

Invert Sugar

A mixture of $1:1$ glucose and fructose produced by the hydrolysis of sucrose; it is known to be sweeter than sucrose.

Lactose

The principal disaccharide found in milk, composed of glucose and galactose units joined by a $\beta$-1,4-glycosidic bond.

Amylose

A straight-chain polymer of glucose units that typically makes up $20\%$ of starch.

Amylopectin

A branched polymer of glucose units that typically makes up $80\%$ of starch.

Gelatinization

The irreversible loss of crystalline regions in starch granules that occurs upon heating in the presence of water.

Retrogradation

The recrystallization of starch during storage that can decrease its digestibility.

Cellulose

An unbranched polymer of glucose units joined by $\beta$-1,4-glycosidic linkages that provides structural support to plant cell walls.

Pectin

Complex polysaccharides rich in galacturonic acid, used as gelling agents, thickeners, and stabilizers in foods like jams and jellies.

Glycogen

An extensively branched glucose polymer used by animals as an energy reserve, highly concentrated in the liver and skeletal muscles.

Polymorphism

The ability of a substance to have more than one crystal structure; for example, fat bloom in chocolate.

Winterization

A process involving dissolving nonpolar fat in a polar solvent at sub-zero temperatures to promote crystal formation of solid fat for removal by filtration.

Hydrogenation

A process that extends the shelf life of fats and oils by reducing their unsaturation via the catalytic addition of hydrogen.

Oxidative Rancidity

Degradation occurring in unsaturated fats when oxygen attacks the $C=C$ bonds, resulting in ketones, aldehydes, and unpleasant smells.

Hydrolytic Rancidity

The breakdown of triglycerides into glycerol and free fatty acids, favored by moisture and enzymes rather than oxygen.

Biological Value (BV)

A measure reflecting how efficiently the body can utilize a protein's amino acids for growth and maintenance.

Essential Amino Acids

The nine amino acids that cannot be synthesized by the body and must be supplied through food: M, T, H, V, I, F, W, K, and L.

Anthocyanins

Water-soluble pigments (red, purple, blue) whose color is pH-dependent, appearing red in acidic and blue in alkaline conditions.

Chlorophyll

Green pigments in plants that can degrade to olive-brown pheophytin under acidic cooking conditions.

Polyphenol Oxidase (PPO)

The enzyme responsible for initiating enzymatic browning by catalyzing the oxidation of phenolic compounds into colored quinones.

Maillard Reaction

A non-enzymatic browning reaction between reducing sugars and amino compounds that forms brown nitrogen-containing polymers called melanoidins.

Caramelization

The thermal degradation of sugars leading to volatiles and brown-colored products, typically occurring at temperatures above $120\,^{\circ}\text{C}$, without requiring amino acids.