Food Science - Exam 2

Ultra-Processed foods + drinks, Gluten & Dough, Yeast breads, Leavening Agents, Quick breads - batter and soft dough, Fats & Oils, and Frying Wks

Name Major cereal grains in US

Corn, oats, barley, rice, and wheat (wheat = #1 in US)

Name basic components of a cereal grain

Bran = fiber-rich outer layer protecting seed and containing B vitamins and trace minerals

Endosperm = middle layer containing carbohydrates and proteins

Germ = small, nutrient-rich core that contains antioxidants, vitamin E, B vitamins, and healthy fats

Explain types of wheat classification

Red vs. White for bran color

Spring vs. Winter for planting season

Hard vs. Soft for protein content

Describe how popcorn pops.

1. Heat is applied to the corn kernel. 

2. The kernel has a dense arrangement of cellulose in the pericarp (hull) that is able to conduct heat very efficiently to the endosperm, leading to steam pressure building up in the pericarp (hull).

3. When the heat builds up, the steam inside the endosperm causes starch gelatinization and protein softening. 

4. The soft starchy endosperm and protein matrix build pressure, causing the pericarp (hull) to burst open. The sudden release of pressures causes the matrix to expand rapidly and puff. The structure then sets as it cools off and becomes light and crisp. 

Describe the process of nixtamalization.

Nixtamalization is the process of soaking and cooking corn in an alkaline solution, typically limewater, which softens the grain, enhances its nutritional value, and improves its flavor. This method also removes the pericarp, making the corn easier to digest and process.

How and why does nixtamalization impact the physical structure of corn kernels?

Nixtamalization changes the kernel by softening up the pericarp and cell walls, intensifying its color and producing volatiles that contribute to the flavor and aroma of the kernel.

Why is nixtamalization beneficial?

The process prevents pellagra (niacin deficiency), increases calcium content, forms resistant starches (retrogradation and fiber), reduces mycotoxins (from mold), and increases iron bioavailability. 

Explain the differences in various preparations of oats and rice.

Different preparations of oats include rolled oats, steel-cut oats, and instant oats, varying in texture and cooking time, while rice varieties like white, brown, and wild rice differ in flavor, texture, and nutritional properties.

Describe differences in preparation and shape/texture of ready-to-eat breakfast cereals. 

Ready-to-eat breakfast cereals can differ in their preparation methods, shapes, and textures. Some are extruded, resulting in a puffed texture, while others are flaked, producing a crunchy bite. The shapes can vary from traditional flakes to shapes like loops or clusters, contributing to different mouthfeels and eating experiences.

Describe key events during the 4 stages of starch cook-up. Use the terms: granule, amylose, gelatinization, pasting, and gelatin. 

When heating a grain, the starch granules become swollen and begin to gelatinize, releasing amylose into the surrounding liquid. As the temperature increases, the starch mixture undergoes pasting, creating a viscous gel. This process continues until the starch granules lose their structure, resulting in a thickened gelatinous mixture.

Identify starches high in amylose.

Corn, wheat, and long-grain white rice are examples of starches that contain higher levels of amylose, leading to a firmer texture when cooked.

Identify starches high in amylopectin.

Potato, tapioca, and short-grain white rice are examples of starches that predominantly contain amylopectin, resulting in a sticky and cohesive texture when cooked.

Compare amylose and amylopectin thickening properties.

Amylose tends to form a more gel-like structure, resulting in a firmer texture and better thickening properties, while amylopectin provides a creamier consistency, contributing to a smooth and stable thickening in sauces and gravies.

What is dextrin? How do its thickening properties compare to starch?

Dextrin is a water-soluble carbohydrate produced from the hydrolysis of starches, commonly used as a thickening agent.

Compared to starch, dextrin thickens at lower temperatures and provides a smoother texture.

4 basic elements of Flour and Water mixtures

Starch granules, gluten proteins, water, and air

Describe the difference between a batter and a dough.

Batter can be poured; Dough can be kneaded and shaped.

Example of batter = pancake batter

Example of dough = bread dough

What are the different types of wheat flour? Which ones have a higher gluten content vs. a lower gluten content relative to all purpose flour, and the kinds of applications that lends them to and why?

Types of wheat flour: Vital Wheat Gluten, Whole Wheat, Durum Wheat, Bread, All-purpose, Pastry, and Cake

Compared to All-purpose flour: Vital Wheat Gluten, Whole Wheat, Durum Wheat, and Bread have higher gluten content b/c they have more protein content, leading to them have a harder and tougher exterior; while Pastry and Cake have lower gluten content b/c they have less protein, resulting in a softer, more delicate texture. 

Name 2 proteins that combine to form gluten. 

Glutenin, which helps with elasticity (stretchiness)

Gliadin, which helps with plasticity (ability to be shaped)

How are hydration and kneading related to gluten development?

Hydration: water (or any liquid) draws out the proteins and starch granules

Kneading: mechanical action that encourages gluten formation by aligning and stretching the proteins and starch granules to create a strong network.

Identity factors that control gluten strength.

Flour type, presence of oxidizing agents (bleached flour increases disulfide bonds which means a stronger flour and bread-like dough), water content, stirring & kneading, salt (a little bit of salt will tighten up the gluten network but too much salt will kill the gluten), and added fats and oils (will weaken gluten network and tenderize the product)

What are the effects of different kinds of milling techniques or nixtamalization processing on cereal grains in terms of cooking time, sensory properties, and nutritional value?

Milling techniques and nixtamalization can significantly impact cooking time by altering the texture of grains, enhance sensory properties such as flavor and aroma through the release of oils, and improve nutritional value by increasing bioavailability of nutrients and reducing antinutrients.

Why do cereals increase in volume and viscosity during cooking? What is this process called?

This process is called gelatinization, where heat and moisture cause starch granules to swell and absorb water, leading to an increase in volume and viscosity.

Why are cereals typically NOT stirred during cooking?

Stirring can break down the structure of starch granules, leading to a decreased viscosity and a gummy texture in the final product.

Identify the essential ingredients in yeast bread and explain the role of each in breadmaking. 

Essential ingredients in yeast bread include flour (provides structure and gluten), water (hydrates and activates yeast), yeast (fermentation agent), salt (flavor and regulates yeast activity), and sugar (food for yeast and enhances browning). Each ingredient plays a crucial role in the breadmaking process, affecting texture, flavor, and rise.

Explain the 4 basic steps in yeast dough preparation and what is happening to the dough in each step. 

1. Mixing: starch granules absorb water, as the yeast cells feed on sugars and produce CO2 and alcohol. The proteins (Glutenin + Gliadin) absorb water and begin to form gluten. 

2. Kneading: the dough is stretched, folded, compressed, and the gluten becomes elongated. Gluten proteins orient side-by-side and develop bonds between neighbors, trapping the air that gets introduced into the dough during the folding process. 

3. Fermentation & Rising: usually has 2 proofs. 1st proof produces CO2, gluten continues to develop, resulting in a completed fermentation of doubled volume, retaining an impression. 2nd proof relaxes the dough and prevents over-stretching of gluten, while subdividing air bubbles, and redistributing yeast cells.

4. Baking: 3 stages. Early baking results in a oven spring, where there is a rapid rise b/c of elongated cells, w/ CO2, steam, and alcohol vapor, and lasts around 6-8 minutes. Mid-Baking causes the gluten to harden, while the starch gelatinizes. The increasing pressure leads to a continued network of holes. Late baking is when the crust begins to brown, and the inner structure becomes fully set. 

Describe the stages of bread and what’s happening during each stage. 

1. Mixing: Ingredients like flour, water, and yeast combine, allowing flour to absorb water and activate gluten formation. Yeast starts fermentation, producing CO2.

2. Kneading: The dough is manipulated, developing gluten structure while air is incorporated, contributing to elasticity.

3. Fermentation: The dough rises as yeast ferments sugars, producing gas that increases volume and develops flavor.

4. Baking: Heat causes the dough to rise further, gelatinizing starches and hardening gluten, while browning the crust.

Explain why steam is important in the bread-baking process.

Steam during bread baking is crucial because it causes the heat transfer rate to increase, air cells to expand rapidly, starch gelatinization happens, and the crust becomes glossy. Additionally, steam helps create a moist environment, allowing for optimal oven spring and preventing the crust from hardening too quickly.

Describe starch retrogradation as it relates to bread, how to temporarily reverse it, and what solutions food processors have come up with to delay its onset. 

Starch retrogradation is the process where gelatinized starch molecules re-associate after cooling and water is expelled, leading to a tougher texture in bread. It can be temporarily reversed by reheating, which disrupts the crystallized structure. Food processors often use ingredients like mono- and diglycerides or enzymes to delay retrogradation and extend shelf life.

Amylose retrogradation happens 1st, upon bread cooling. 

Amylopectin retrogradation happens over a period of days. 

Describe the three main types of leavening agents and how they work.

Biological = yeast produces CO2, forming bubbles via glucose fermentation. Fermentation rate is also affected by sugar and salt.

Chemical = baking soda has sodium bicarbonate, which produces CO2 when in contact with water and acid. Baking soda (alkaline) and acid ionize to produce CO2.

Physical = baking powder has sodium bicarbonate, dry acid, and starch. Sodium bicarb is the source of CO2, dry acid can only be activated with water or heat, but starch absorbs the water, which prevents the reaction from happening until it is baked. The steam during baking raises the batter, and the CO2 from baking powder contributes to leavening.

Explain why baking powder is considered a complete leavening agent. 

Baking powder has sodium bicarbonate, dry acid, and starch, making it easy to pour and for accurate measuring, and it doesn’t activate until after it has started baking. 

Describe the basic reaction for baking soda leavening.

Baking soda, or sodium bicarbonate, reacts with acids (like vinegar or buttermilk) in the presence of moisture to produce carbon dioxide gas, which creates bubbles that help leaven baked goods.

What is the difference between a single and a double-acting baking powder?

Single Acting: has 1 acid; usually fast-acting acid

Double Acting: has 2 acids, 1 fast- and 1 slow-acting acids

What is the difference between fast- and slow-acting baking powder?

Fast-acting acids activate with water, and is used when the a recipe doesn’t contain an acid ingredient. 

Slow-acting acids activate with heat, allowing the baker to hold the batter/dough before baking without losing CO2.

What would the outcome be if the butter in a biscuit recipe was incorporated completely?

The biscuits would likely become dense and may not rise properly, resulting in a tough texture instead of the desired light and flaky consistency.

Why is it important to keep butter cold when folding it into a biscuit recipe?

Keeping butter cold ensures that it remains solid, creating flaky layers in the biscuits. If the butter is too warm, it will melt into the dough, resulting in a denser texture.

Why would overworking the biscuit dough result in a tougher texture?

Overworking the biscuit dough develops gluten, which can make the biscuits dense and chewy instead of light and flaky.

What might you expect to happen if milk was replaced with buttermilk in a biscuit recipe? How might you modify the ingredients if the buttermilk was replaced with regular milk?

The milk would cause the biscuit recipe to not rise as well and have a denser texture, without the aid of the acid that buttermilk has. If using regular milk, you would need to add a tablespoon of vinegar or lemon juice to mimic buttermilk's acidity, improving the rise and texture.

Are eggs the main leavening agent in cream puff recipes? Explain. 

No, they are not the main leavening agent in cream puff recipes, but the moisture from the eggs are helpful in producing H2O for the steam leavening that happens in the oven during the baking process. 

Why is it important to not open an oven when baking cream puffs?

Opening the oven will cause all of the stream to leave, which will result in the cream puffs collapsing and not rising properly.

How would a cream puff recipe differ if there was more flour or less water added? Why?

Adding more flour would result in a denser cream puff, while less water would yield a drier product with less steam, preventing proper rising and creating a firmer texture.

When flour (or any starch) is directly added to hot water, it gets lumpy because of starch gelatinizing on the outside of lumps. Why doesn’t this happen with cream puff dough?

The emulsification of fat in the cream puff dough allows for a smoother incorporation of flour, preventing lumping and ensuring an even distribution during mixing.

After flour is added to the hot water/butter mixture, cream puff dough typically takes on a curdled/separated appearance, but becomes glossy after the eggs are mixed in. Why?

This occurs because the heat from the mixture cooks the flour, allowing it to absorb water and create a smooth batter after the eggs are incorporated.

Use these words in 1-2 sentences to tie ideas together: steam, cream puff dough, heat, water, expand

When cream puff dough is heated up in an oven, the water from the eggs incorporated into the recipe becomes steam, and causes the dough to expand until they are finished baking. 

What kind of emulsion is cream? What kind is butter?

Cream is a water-in-oil emulsion, while butter is an oil-in-water emulsion.

What did it look like when the emulsion inverted?

The emulsion appeared as a thicker, more stable mixture with a creamy texture, indicating that the water phase had been incorporated into the oil phase.

What was the continuous phase of the initial cream emulsion, and then of the final butter emulsion?

In the initial cream emulsion, the continuous phase was the water, while in the final butter emulsion, the continuous phase became the oil.

How did the different continuous phases impact the texture of the emulsion?

The texture of the emulsion varied significantly; a water continuous phase resulted in a lighter, creamier texture, while an oil continuous phase provided a denser, richer mouthfeel.

Which emulsion was more water soluble and which was more fat soluble?

The cream emulsion was more water soluble, while the butter emulsion was more fat soluble.

What is an emulsion?

An emulsion is a mixture of two immiscible liquids, where one liquid is dispersed in the other in the form of tiny droplets, typically stabilized by an emulsifier.

Name some common food emulsions.

Mayonnaise, salad dressings, and hollandaise sauce.

Identify the continuous phase and dispersed phase of an emulsion.

In an emulsion, the continuous phase is the liquid in which the droplets are dispersed, while the dispersed phase consists of the tiny droplets of the other liquid.

Describe 5 outcomes of frying.

Moisture transfer, fat transfer, crust formation, interior cooking, and degradation of oil

Advise how to resolve problems in frying. 

Smoking point, oil temperature, and food moisture content should be monitored closely. Lowering temperature, using a different oil, or drying food before frying can reduce smoke and improve frying outcomes.

Name some appropriate oils for frying and explain the key property that makes them so. 

Some appropriate oils for frying include canola oil, peanut oil, and vegetable oil. These oils have high smoke points, which allow them to withstand the high temperatures required for frying without breaking down.