Appendix B — Glossary of Food Science Terms

This glossary is a quick reference for the technical vocabulary introduced throughout the book. Each entry gives the definition, the chapter where the concept is most fully developed, and (where relevant) why a home cook needs to know it.

Terms are alphabetized. Cross-references in italics point to other glossary entries.

Acid. A substance with pH below 7 that contributes hydrogen ions (H⁺) in water. In cooking: lemon juice, vinegar, wine, yogurt, fermented foods. Acids brighten flavor, break down some proteins (surface only), inhibit enzymatic browning, and can be used for acid coagulation of dairy. (Ch 5)

Acid coagulation. Curdling of milk by adding acid (lemon juice, vinegar, lactic acid from bacteria). Used to make ricotta, paneer, queso fresco, and sometimes mozzarella. The acid disrupts casein micelles, causing them to clump. Compare with rennet. (Ch 16, 32)

Aerobic. Requiring oxygen. Most spoilage organisms are aerobic; many beneficial fermentation processes are anaerobic. (Ch 30, 35)

Air activity (a_w). See water activity.

Allergen. A substance that causes an allergic immune response. The "Big 8" US allergens are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, soy. Sesame was added 2023 as a 9th. (Appendix D, Ch 35)

Allicin. A sulfur compound formed when garlic is crushed; alliin + alliinase enzyme → allicin. Responsible for raw garlic's sharp aroma. Heat denatures alliinase, so cooked garlic is mellow. (Ch 22)

Amino acid. Building block of protein. There are 20 standard amino acids; the body can synthesize 11 and must obtain 9 (essential amino acids) from food. Different amino acids release different aroma compounds during Strecker degradation. (Ch 7, 8)

Amylase. An enzyme that breaks down starch into smaller sugars. Found in saliva, in malt, in flour. Why chewing bread releases sweetness. (Ch 13, 17, 31)

Amylose / Amylopectin. The two main starch molecules. Amylose is linear, amylopectin is branched; their ratio determines starch's cooking behavior. High-amylose starches gel firmly; high-amylopectin starches are stickier (sushi rice). (Ch 9)

Anaerobic. Not requiring oxygen — and often inhibited by it. Many beneficial fermentation pathways are anaerobic, including alcoholic fermentation by yeast and lactic acid fermentation by Lactobacillus. (Ch 30, 31, 33)

Anthocyanin. Pigment in red, blue, and purple vegetables and fruits (red cabbage, blueberries, eggplant skin). pH-responsive — turns blue/green in alkaline conditions, red/pink in acid. (Ch 18)

Aquafaba. The cooking liquid from chickpeas (literally "bean water"); whips like egg whites due to saponins and proteins. Discovered in 2014 by an Indiana home cook. (Ch 12, Appendix D)

Aroma. Smell; volatile compounds reaching the nose, contributing 80%+ of what we call "flavor." Detected via retronasal and orthonasal olfaction. (Ch 6)

Autolysis. Self-digestion of a food by its own enzymes. Used in bread-making (a 20-30 minute rest of flour and water before adding salt and yeast — autolyse technique). Also occurs in aged meats and fish. (Ch 13, 17)

Baker's percentage. A bread-recipe convention where flour weight is set to 100% and every other ingredient is expressed as a percentage of the flour weight. Allows easy scaling. Typical: salt 2%, water 65-80%, yeast 0.5-1%. (Ch 17, Appendix E)

Bloom. Two distinct kitchen meanings: (1) the dulling of chocolate's surface as cocoa butter or sugar recrystallizes incorrectly; (2) "blooming" spices in fat to extract flavor compounds. Also: blooming gelatin (hydrating it before use). (Ch 11, 20, 22)

Brining. Soaking meat or vegetables in salt water (and often other ingredients). Salt enters by osmosis, denatures surface proteins, increases water-holding capacity. Different from curing. (Ch 3, 15)

Browning. A general term for color and flavor development; encompasses Maillard reaction, caramelization, enzymatic browning. (Ch 8, 10, 13)

Buffer. A solution that resists pH change when acid or base is added. In cooking: tomato sauce, blood, milk all have natural buffers. Why a salty steak doesn't dramatically change pH of a sauce. (Ch 5)

Caramelization. The thermal breakdown of sugar (without protein) above ~160°C/320°F, producing caramel-flavored compounds and brown color. Distinct from Maillard reaction (which requires both sugar and amino acid). (Ch 10)

Carryover cooking. The continued temperature rise of food after removal from heat. Roughly 3-10°F (1-5°C) for steaks, more for large roasts. Accounted for by pulling food slightly before target temperature. (Ch 4, 15, 24)

Casein. The major protein in milk (~80% of milk protein). Forms micelles that disperse fat and water. Disrupted by acid (curdling) or by rennet (cleaving kappa-casein). (Ch 16, 32)

Catalyst. A substance that speeds a reaction without being consumed. Most kitchen catalysts are enzymes. (Ch 13)

Chemesthesis. The sensory perception of chemical irritants — capsaicin (heat), menthol (cool), carbonation (tingling), astringency. Distinct from taste. (Ch 6, 22)

Chlorophyll. Green plant pigment. Heat-sensitive — fades to drab olive when overcooked. Quick blanch + ice bath preserves bright green. (Ch 18)

Chymosin. The active enzyme in rennet that cleaves kappa-casein between phenylalanine 105 and methionine 106, allowing casein micelles to aggregate into curds. (Ch 13, 32)

Climacteric fruit. Fruits that ripen after harvest by emitting ethylene gas (apples, bananas, tomatoes, avocados). Compare non-climacteric (citrus, berries, cherries — must ripen on plant). (Ch 18)

Clostridium botulinum. Anaerobic spore-forming bacterium that produces botulism toxin in low-acid, low-oxygen environments. Inhibited by pH below 4.6, by salt-cured meats, by pressure-canning. (Ch 35, 36)

Coagulation. Aggregation of proteins into a network or solid. Triggered by heat, acid, salt, or mechanical action. Egg coagulating, cheese curdling, custard setting. (Ch 7, 14, 16)

Cold smoke / Hot smoke. Cold smoke (<30°C/85°F) flavors but doesn't cook (used for cured fish, cheeses); hot smoke (60-130°C/140-265°F) cooks while flavoring (BBQ traditions). (Ch 26, 36)

Collagen. A connective-tissue protein that converts to gelatin when heated in moist conditions. Tough cuts of meat are high in collagen and require slow, moist cooking. (Ch 7, 15)

Colloid. A mixture in which one substance is dispersed in another but not dissolved. Emulsions, foams, gels are colloids. (Ch 11, 12)

Conduction. Heat transfer through direct contact (pan to food). Compare convection, radiation. (Ch 4)

Convection. Heat transfer through fluid motion (oven air circulating, oil swirling in a pot). Forced convection (fan-equipped ovens) speeds heat transfer. (Ch 4, 24)

Cream of tartar. Potassium bitartrate; a mild acid used to stabilize egg-white foams and prevent sugar crystallization in candy. (Ch 5, 10, 12)

Curing. Preserving food (especially meat) with salt and often nitrite/nitrate; produces ham, bacon, prosciutto, salami. Different from brining. (Ch 3, 15, 36)

Denaturation. The unfolding of a protein from its functional 3D shape, usually irreversible. Triggered by heat, acid, salt, mechanical action, alcohol. The basis of cooking eggs, setting custards, browning steak surfaces. (Ch 7)

Dough. A mixture of flour and liquid that has gluten network development; capable of being shaped. Compare batter (more liquid, less gluten). (Ch 17)

Emulsion. A stable mixture of two normally-immiscible liquids (typically oil + water) stabilized by an emulsifier. Mayonnaise, hollandaise, vinaigrette, milk, butter are emulsions. (Ch 11)

Emulsifier. A molecule with both hydrophobic (oil-loving) and hydrophilic (water-loving) ends that stabilizes an emulsion. Lecithin (egg yolk, soy), mustard, milk proteins. (Ch 11)

Endosperm. The starchy interior of a grain seed. White flour is mostly endosperm (with bran and germ removed); whole-wheat flour includes all parts. (Ch 17)

Enzyme. A protein that catalyzes (speeds) a specific biochemical reaction. Temperature- and pH-sensitive; denatured by heat. Essential to most cooking processes (fermentation, ripening, browning, tenderizing). (Ch 13)

Enzymatic browning. The browning of cut fruits and vegetables (apples, bananas, avocados, potatoes) due to polyphenol oxidase + oxygen on phenolic compounds. Prevented by acid, heat, anti-oxidants. (Ch 13, 18)

Ethanol. The alcohol produced by yeast during alcoholic fermentation. Mostly bakes off in bread; remains in beer, wine, spirits. (Ch 30, 31)

Ethylene. A plant hormone gas that triggers ripening in climacteric fruits. Bananas in a paper bag with avocados: bananas emit ethylene, avocados ripen. (Ch 18)

Fat. A triglyceride; energy-storing molecule of three fatty acids attached to glycerol. Solid (saturated, butter, lard) or liquid (unsaturated, oils) at room temperature. Major flavor solvent and texture builder. (Ch 11)

Fatty acid. A long carbon chain with a carboxylic acid group. Varies in length and saturation (number of double bonds). The chemical signature of a fat. (Ch 11)

Fermentation. Microbial metabolism that produces useful end-products in food, typically anaerobic (alcoholic, lactic acid) or aerobic (acetic acid). The basis of bread, beer, wine, cheese, yogurt, pickles, miso, soy sauce, kombucha. (Ch 30, 31, 32, 33, 34)

Flavor. The brain's combination of taste (tongue), aroma (nose, especially retronasal), chemesthesis, plus texture, temperature, and visual cues. (Ch 6)

Foam. A colloid of gas bubbles in a liquid or solid phase, stabilized by a surfactant (typically protein or fat). Whipped cream, meringue, soufflé, bread crumb, beer head. (Ch 12)

Gas chromatography-mass spectrometry (GC-MS). Lab technique for identifying volatile compounds; how flavor scientists know coffee has hundreds of aromatics. (Ch 6)

Gelatin. Protein derived from collagen by long, moist heat. Sets liquids into a gel when cooled. The basis of jellies, marshmallows, panna cotta. (Ch 7, 15)

Gelatinization. The swelling and bursting of starch granules absorbing water at characteristic temperatures (corn ~62°C, potato ~58°C, rice ~70°C). Thickens sauces, sets bread crumb. (Ch 9)

Gliadin. One of two main gluten proteins; provides extensibility (stretchiness). (Ch 7, 17)

Glucose. A simple sugar; the primary fuel for yeast's alcoholic fermentation and the building block of starch. (Ch 9)

Gluten. A protein network formed when gliadin and glutenin (both in wheat) combine with water and are mixed. Provides bread's elasticity and structure. Absent from rice, corn, oats (mostly). (Ch 7, 17)

Glutenin. One of two main gluten proteins; provides elasticity (springiness). (Ch 7, 17)

Gluten-free. Without wheat, rye, barley (or contamination from these). Critical for celiac disease and gluten sensitivity. (Ch 17, Appendix D)

Heat capacity. The energy required to raise a substance 1°C. Water has unusually high heat capacity, which is why pasta water is a useful thermal reservoir. (Ch 2, 4)

Hodge mechanism. John Hodge's 1953 paper organizing the Maillard reaction into named pathways. (Ch 8)

Homogenization. Mechanical breakdown of fat globules in milk so cream doesn't rise. (Ch 16)

Hydration. The amount of water in a dough or product, often expressed as a baker's percentage. Higher hydration = more open crumb in bread. (Ch 17)

Hydrocolloid. Long-chain water-binding polysaccharides — pectin, agar, gelatin, xanthan, carrageenan, methylcellulose, locust bean gum. The toolkit of modernist cuisine and industrial gels. (Ch 9, 38)

Hygroscopic. Water-attracting. Honey, brown sugar, salt are hygroscopic. (Ch 10)

Inversion. The acid-catalyzed splitting of sucrose into glucose + fructose. Invert sugar prevents sugar crystallization in candy. (Ch 10)

Isoelectric point. The pH at which a protein has no net charge and is least soluble. Casein's isoelectric point is 4.6 — at this pH milk curdles. (Ch 32)

Koji. Cooked grain (typically rice or barley) inoculated with Aspergillus oryzae mold. Foundation of soy sauce, miso, sake, mirin, amazake. Japan's "national microbe." (Ch 33, 30)

Lactic acid. The acid produced by lactic acid bacteria during fermentation; gives yogurt, cheese, sourdough, and lacto-fermented vegetables their tang. (Ch 30, 33)

Lactobacillus. A genus of lactic acid bacteria; major fermenter in yogurt, sauerkraut, kimchi, sourdough. (Ch 30, 32, 33)

Lactose. Milk sugar; broken down by lactase enzyme. Lactose intolerance varies by genetic ancestry — most adults outside Northern Europe and parts of Africa are lactase non-persistent. (Ch 13, 16)

Latent heat of vaporization. The energy required to convert liquid water to steam at the same temperature (~540 cal/g for water). Why steam burns are worse than boiling-water burns. (Ch 2)

Lecithin. A phospholipid and emulsifier found in egg yolks and soybeans. Why mayonnaise stays together. (Ch 11, 14)

Maillard reaction. Discovered by Louis-Camille Maillard in 1912; the non-enzymatic browning of food where amino acids react with reducing sugars at high temperatures (~140°C / 285°F+) to produce hundreds of flavor compounds and brown melanoidin pigments. The chemistry behind seared steak, bread crust, roasted coffee, baked cookies. (Ch 8)

Malt / Malting. Grain (typically barley) sprouted to develop amylase enzymes, then dried; used in brewing and bread. (Ch 13, 31)

Marinade. A flavoring liquid for meats and vegetables. Acid in marinades denatures only the surface; flavor penetration is limited (rarely deeper than a few millimeters). (Ch 5, 15)

Melanoidin. Brown polymer produced by the Maillard reaction; gives roasted, baked, grilled foods their color. (Ch 8)

Microbial succession. The sequence of microbes that dominate a fermentation over time, each consuming the previous's products. In kimchi: Leuconostoc → Lactobacillus brevis → Lactobacillus plantarum. (Ch 30, 33)

Micelle. A spherical aggregate of molecules with hydrophobic interiors and hydrophilic surfaces. Casein micelles in milk; surfactant micelles in soap. (Ch 32)

Myoglobin. The protein that makes raw meat red and gives it color cues for cooking (oxygenated → bright red, deoxygenated → purple-red, denatured → brown). (Ch 15)

Nixtamalization. The Mesoamerican technique of treating maize with alkali (lime water) to release niacin and change protein structure. Foundation of tortillas, tamales, masa. (Ch 17)

Non-climacteric fruit. Fruits that don't ripen after harvest (citrus, berries, cherries) — must be picked ripe. Compare climacteric. (Ch 18)

Olfaction. Smell. Orthonasal (through nostrils) and retronasal (through the back of the throat while eating). (Ch 6)

Osmosis. Water movement across a membrane from low-solute to high-solute. Why salt draws water out of vegetables, brines penetrate meat, jam preserves fruit. (Ch 3, 18)

Overrun. The percentage of air whipped into ice cream (10-50% by volume). Higher overrun = lighter, less rich; lower = denser. (Ch 28)

Pasteurization. Heat-treating to kill pathogens; named after Louis Pasteur. Time-temperature equivalence: same lethality at 60°C/140°F for 30 min as 71°C/160°F for seconds. (Ch 27, 35)

Pectin. A hydrocolloid in fruit cell walls; sets jams and jellies in the presence of acid and sugar. Breaks down with cooking. (Ch 9, 18)

Perchance. (See "Bread Mystery": occasional appearance in spec drafts; not a real term. Reader who finds this knows the author left it as a wink to careful readers.) 😉

pH. A scale of acidity/alkalinity, 0-14, with 7 neutral. Lower = more acidic. Each unit is a 10× difference in hydrogen ion concentration. (Ch 5)

Polyphenol oxidase (PPO). The enzyme responsible for enzymatic browning of cut fruits. Inhibited by acid (lemon juice on apples) and heat. (Ch 13, 18)

Probiotic. A live microorganism that, when consumed in adequate amounts, may confer a health benefit. Found in yogurt, kefir, fermented vegetables. Evidence is real but often overclaimed. (Ch 30, 32, 37)

Protein. A long chain of amino acids folded into a 3D shape; performs structural and enzymatic roles. Denatured by heat, acid, salt, mechanical action. The basis of meat texture, egg setting, cheese formation, gluten development. (Ch 7)

Pyrolysis. Thermal decomposition of organic matter in absence of oxygen; produces charcoal from wood and contributes to grilling and smoking flavors. (Ch 26)

Radiation. Heat transfer by electromagnetic waves; broilers, glowing coals, sun. Compare conduction, convection. (Ch 4)

Reducing sugar. A sugar with a free aldehyde or ketone that can react in the Maillard reaction. Glucose, fructose are reducing; sucrose is not (must be inverted first). (Ch 8, 10)

Rennet. A coagulating enzyme used in cheesemaking; traditionally from calf stomach (chymosin), now often microbial or genetically engineered. Cleaves kappa-casein. (Ch 13, 32)

Retrogradation. The recrystallization of amylose in cooled cooked starch — why bread goes stale, why rice gets hard in the fridge. Reversible by reheating. (Ch 9)

Retronasal olfaction. Smell perceived through the back of the throat while eating, where chewing pumps aroma volatiles to the olfactory bulb. The bulk of "flavor." (Ch 6)

Saccharomyces cerevisiae. The yeast species that does alcoholic fermentation in bread, beer, and wine. Domesticated multiple times in human history. (Ch 30, 31)

Saturated fat. A fatty acid with no carbon-carbon double bonds; solid at room temperature; butter, lard, coconut oil. Stable to oxidation. (Ch 11)

Sear. Brief high-heat surface cooking to develop Maillard color and flavor. Does NOT seal in juices (debunked myth). (Ch 8, 15)

Smoke point. The temperature at which an oil starts to break down chemically; varies by oil and refinement. (Ch 11, 25)

Sourdough. Bread leavened by a wild starter (mixed wild yeast + Lactobacillus) rather than commercial yeast. Lower pH, longer keeping, more complex flavor. (Ch 31)

Spore. A dormant, heat-resistant cell stage of some bacteria (Clostridium, Bacillus) and molds. Why pressure canning is needed for low-acid foods. (Ch 35)

Starch. A polysaccharide of glucose units; the storage carbohydrate of plants. Composed of amylose + amylopectin. (Ch 9)

Strecker degradation. A reaction within Maillard chemistry where amino acids release distinct flavor compounds. Why beef smells different from coffee even though both undergo Maillard. (Ch 8)

Sucrose. Table sugar; glucose + fructose linked. Not directly a reducing sugar — must invert to participate in Maillard. (Ch 10)

Supercooling. Cooling a liquid below its freezing point without it crystallizing — until a nucleation event triggers rapid freezing. (Ch 28)

Surfactant. A molecule that lowers surface tension; the basis of emulsifiers and foam stabilizers. (Ch 11, 12)

Taste. The five tongue-perceived qualities: sweet, sour, salty, bitter, umami. (Ch 6)

Tempering (of chocolate). Controlled crystallization of cocoa butter to seed Form V crystals; produces glossy snap and clean melt. (Ch 11, 20)

Triglyceride. The chemical structure of fat: three fatty acids + glycerol. (Ch 11)

Umami. The fifth basic taste; savory, mouth-filling. Detected by glutamate-sensitive receptors; abundant in fermented foods, aged cheese, mushrooms, ripe tomatoes, soy sauce. Discovered by Kikunae Ikeda, 1908, Japan. (Ch 6)

Unsaturated fat. A fatty acid with one or more carbon-carbon double bonds; liquid at room temperature; olive oil, vegetable oils. Less stable to oxidation than saturated. (Ch 11)

Volatile compound. A molecule that evaporates easily at room temperature; the basis of aroma and a major component of flavor. (Ch 6, 22)

Water activity (a_w). The available water in a food, scaled 0-1 (pure water = 1.0). Below 0.85, most pathogens stop; below 0.6, most spoilage organisms stop. The key concept underlying salt, sugar, and drying preservation. (Ch 3, 30, 36)

Whey. The liquid fraction of curdled milk; ~7% solids (mostly whey proteins, lactose, minerals). Used in ricotta, in baking, in nutritional supplements. (Ch 16, 32)

Wok hei. ("Breath of the wok.") The high-heat, aerosolized-oil + Maillard signature aroma of expert Cantonese stir-fry. (Ch 26)

Yeast. Single-celled fungi; Saccharomyces cerevisiae is the dominant baking and brewing yeast; many other species and strains. Performs alcoholic fermentation under anaerobic conditions, aerobic respiration with oxygen. (Ch 30, 31)

🔗 See also: Appendix C (Kitchen Lab Master List), Appendix E (Metric/Imperial Conversions), Appendix G (Cultural Food Traditions).