Quiz — Chapter 17: Grains and Bread

Eighteen questions. Mix of multiple choice, short answer, and "explain why." Answer key with explanations at the end.

Multiple Choice (questions 1–13)

1. Which two proteins in wheat flour combine to form gluten when hydrated and worked?

a) Albumin and globulin b) Casein and whey protein c) Gliadin and glutenin d) Lectin and ferritin

2. Of the three parts of a wheat grain, which contains the highest proportion of starch?

a) Bran b) Germ c) Endosperm d) Husk

3. A bread recipe calls for 800 g flour, 560 g water, 16 g salt, and 4 g yeast. What is the hydration percentage?

a) 56% b) 70% c) 80% d) 140%

4. Why does the refrigerator stale bread faster than the kitchen counter?

a) Bacteria grow faster in the cold b) Starch retrogradation is fastest at refrigerator temperatures c) Refrigerators are very dry environments d) Yeast continues to ferment in the cold

5. What is the function of scoring (slashing) a loaf of bread before baking?

a) Decoration only b) To release alcohol vapor c) To create a controlled weak point where expanding gases can push through d) To prevent the bread from over-rising

6. Which gas is primarily responsible for raising bread dough during fermentation?

a) Oxygen (O₂) b) Ethanol vapor c) Carbon dioxide (CO₂) d) Hydrogen (H₂)

7. What is the primary chemical reagent traditionally used in nixtamalization?

a) Sodium chloride b) Calcium hydroxide (slaked lime) c) Sodium bicarbonate d) Acetic acid

8. Why does steam in the oven help bread achieve maximum oven spring?

a) Steam adds water to the dough b) Steam delays the setting of the crust, allowing the gluten network to stretch longer c) Steam kills the yeast, preventing over-rising d) Steam carries flavor compounds into the crust

9. Which of the following is NOT a strategy to develop gluten in dough?

a) Vigorous kneading b) Stretch-and-fold method c) Long autolysis d) Refrigerating the flour before mixing

10. A baker performs the windowpane test on a piece of dough and finds it tears immediately into ragged pieces. What is the most likely problem?

a) Too much water b) Underdeveloped gluten c) Too much salt d) Yeast is dead

11. Which of the following is true about the relationship between celiac disease and gluten?

a) Celiac disease is a fad with no scientific basis b) Celiac disease is an autoimmune condition affecting roughly 1% of the population c) Celiac patients can safely eat sourdough because the bacteria break down gluten d) Celiac is the same as gluten sensitivity

12. Which leavening agent is "self-contained" in that it includes both an acid and a base?

a) Baking soda b) Baking powder c) Yeast d) Cream of tartar

13. Why is wheat (as opposed to other grains like rice or corn) the basis of most leavened breads?

a) Wheat grows faster than other grains b) Wheat has the highest starch content c) Wheat contains gliadin and glutenin, which form a unique gas-trapping protein network d) Wheat is the cheapest grain

Short Answer (questions 14–18)

14. A friend made bread that came out dense and gummy in the middle. List three possible causes and how to test each one.

15. Explain why salt is described as both a "flavor enhancer" and a "structural reinforcer" in bread. Give the mechanism for each role.

16. What is starch retrogradation, and how does it relate to bread staling? Why does freezing prevent it while refrigeration accelerates it?

17. Describe the symbiotic relationship between yeasts and lactic acid bacteria in a sourdough starter. What does each contribute, and why don't they out-compete each other?

18. Walk through the three forces that drive oven spring in the first ten minutes of baking. Why is the timing critical?

Answer Key

1. c) Gliadin and glutenin. These two wheat proteins, when hydrated and mechanically worked, form the viscoelastic gluten network. Other grains have proteins, but they don't form a gluten-like network because they lack this specific combination.

2. c) Endosperm. The endosperm is about 83% of the wheat grain by mass and is mostly starch with the gluten-forming proteins embedded. The bran is the fibrous outer layer; the germ is the embryo (rich in fats and vitamins, but small).

3. b) 70%. In baker's percentages, water mass / flour mass = 560/800 = 0.70 = 70% hydration.

4. b) Starch retrogradation is fastest at refrigerator temperatures. Around 4°C, molecular mobility is high enough for water to migrate but low enough for starch chains to recrystallize into rigid forms. Freezing slows molecular motion enough to almost stop retrogradation.

5. c) To create a controlled weak point where expanding gases can push through. Without scoring, the expanding gas in the oven would rupture the surface randomly, often in ugly ways. A score directs and shapes the rise.

6. c) Carbon dioxide (CO₂). Yeast glycolysis produces CO₂ and ethanol. The CO₂ is the gas that inflates bread bubbles. Ethanol vaporizes during baking but contributes mainly to oven spring rather than to dough rise.

7. b) Calcium hydroxide (slaked lime). Mesoamerican peoples developed the technique of cooking corn in alkaline solutions (lime water, or wood ash water) to make masa. The alkali releases bound niacin, softens the corn, and changes its protein chemistry.

8. b) Steam delays the setting of the crust, allowing the gluten network to stretch longer. When dry oven air hits a wet dough, the surface dries quickly and begins to set; once set, it can't stretch further. Steam keeps the surface wet and extensible during the critical first 10–15 minutes of expansion.

9. d) Refrigerating the flour before mixing. Cold flour does not develop gluten; in fact, cold slows gluten development. The other three methods all accelerate or accomplish gluten development through different mechanisms.

10. b) Underdeveloped gluten. A windowpane test that tears immediately indicates the gliadin and glutenin haven't yet formed a continuous network. Solution: knead more, or mix and rest longer.

11. b) Celiac disease is an autoimmune condition affecting roughly 1% of the population. It is real, medically diagnosed, and requires strict lifelong gluten avoidance. Sourdough fermentation does not break down gluten meaningfully and is unsafe for celiac patients.

12. b) Baking powder. Baking powder contains baking soda (base), a powdered acid (e.g., cream of tartar), and a starch buffer. Adding water activates the reaction. Baking soda alone requires an external acid in the recipe.

13. c) Wheat contains gliadin and glutenin, which form a unique gas-trapping protein network. No other major grain has this combination. Rice, corn, sorghum, millet, etc. lack the elasticity needed for tall yeasted bread.

14. (Sample answer.) Three possible causes: (1) Underbaked — test by checking internal temperature; lean breads should reach 95°C/203°F. (2) Underdeveloped gluten — test by doing a windowpane test on the next batch's dough at the end of mixing. (3) Hydration too low for the flour — test by trying a 5% higher hydration on the next batch and comparing crumb structure.

15. As flavor enhancer: Salt suppresses bitter perception in the brain, enhances umami and sweet perception, and at the right level (~1.8–2% by flour weight) is essential for the bread tasting "complete." As structural reinforcer: Salt's sodium and chloride ions screen the charged groups on gluten proteins, allowing tighter packing; salt also encourages additional disulfide bond formation between glutenin chains. The result is a stronger, more elastic gluten network. Salt also slows yeast (osmotic effect on cells), which paradoxically improves flavor by extending fermentation time.

16. Starch retrogradation is the slow recrystallization of gelatinized starch chains as the bread cools. During baking, starch granules absorb water and become an amorphous gel (gelatinization). After baking, those gelatinized chains slowly re-organize into more rigid crystalline structures, expelling water and becoming hard. This is what makes bread go stale. Freezing prevents it because at -18°C, molecular motion is too slow for starch chains to rearrange. Refrigeration accelerates it because ~4°C is in the sweet spot of molecular mobility — water can migrate, and starch can crystallize, faster than at room temperature.

17. Yeasts contribute mainly CO₂ (leavening) and ethanol, plus various aroma compounds. Lactic acid bacteria contribute lactic acid (smooth, dairy-like sourness) and acetic acid (sharper, vinegar-like sourness), plus secondary metabolites that contribute to flavor and to suppressing molds. They don't out-compete each other because: (a) the yeasts and bacteria consume different sugars (yeasts often consume glucose; some LAB consume maltose); (b) the ethanol produced by yeast inhibits LAB growth somewhat; (c) the acid produced by LAB inhibits other yeasts (but the sourdough yeasts are acid-tolerant); (d) the system reaches a dynamic equilibrium where each population's growth limits the other's.

18. The three forces: (1) CO₂ expansion — gas already trapped in the gluten network expands as it heats (PV=nRT). (2) Ethanol vaporization — ethanol from fermentation, boiling point 78°C, flashes to vapor as the dough heats past that point. (3) Steam from dough water — water in the dough turns to steam, further inflating bubbles. The timing is critical because past about 60°C, the gluten begins to denature and set; past 75°C, the starch gelatinizes and locks the structure. Once set, no more spring is possible. So the dough must arrive in a hot oven with plenty of latent gas, intact gluten, and a wet surface (steam delay) so that maximum expansion can happen before the structure locks in.