Water Content in Foods Quiz

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Questions and Answers

What characteristic of bound water makes it not easily removed from food items?

High solubility for salts and sugars

Low vapor pressure

High vapor pressure (correct)

Low solubility for salts and sugars

Why does ice float in water?

Ice is less dense than water (correct)

Ice is denser than water

Ice has a higher freezing point than water

Ice has a lower freezing point than water

What is the approximate water content in potato?

91%

40%

74% (correct)

How does the addition of solutes like salt or sugar affect the freezing point of water?

Lowers the freezing point Signup and view all the answers

Which food item has the lowest water content?

Sugar, candy Signup and view all the answers

What happens to cells in plants/meat when frozen due to the expansion of water?

They rupture Signup and view all the answers

What does an alkaline solution provide?

Hydroxyl (OH-) Signup and view all the answers

What is the result of combining baking powder with water?

Release of CO2 Signup and view all the answers

What does water activity (aw) determine in food preservation?

Perishability of food Signup and view all the answers

Which type of lipids are solid at room temperature?

Fats Signup and view all the answers

What role does salt play in preserving food?

Draws water out of foods Signup and view all the answers

What happens to bacteria when they contact heavily salted food?

They die of dehydration Signup and view all the answers

What happens when a gram of ice absorbs 80 calories of heat?

Ice melts and turns into water without a rise in temperature Signup and view all the answers

At what temperature does water start boiling at sea level?

100⁰C Signup and view all the answers

Why does water boil at a lower temperature in the mountains?

Due to increased elevation and lower atmospheric pressure Signup and view all the answers

How does a pressure cooker speed up the heating time compared to a regular open pot?

By increasing the boiling temperature of water beyond 100⁰C Signup and view all the answers

What is the main reason recipes are usually modified for elevations above 3,000 feet?

To adjust for the lower boiling temperatures at high elevations Signup and view all the answers

What is the purpose of latent heat in changing the state of water from solid to liquid or steam?

To cause water to reach its melting point without a rise in temperature Signup and view all the answers

What is the function of fats in food related to appearance?

Enhancing glossiness Signup and view all the answers

Which type of protein is mostly complete and mainly sourced from animals?

Complete protein Signup and view all the answers

What process occurs when proteins denature due to extreme pH or heat?

Denaturation Signup and view all the answers

Which protein function involves the capability to attract water and form a gel?

Hydration Signup and view all the answers

Which protein characteristic allows for bread dough to rise during baking?

Elasticity of gluten Signup and view all the answers

What distinguishes complete proteins from incomplete proteins?

Essential amino acid content Signup and view all the answers

What is the main purpose of adding antioxidants like vitamin A, C, E, and selenium to foods?

To neutralize free radicals and increase the shelf life of the products Signup and view all the answers

Which of the following is NOT a function of vitamin and mineral in regulating metabolic functions?

Stiffening egg whites Signup and view all the answers

What is the Maillard reaction primarily responsible for in food preparation?

Creating a golden crust on baked products Signup and view all the answers

What does the term 'buffering' refer to in food science?

Resisting extreme shifts in pH Signup and view all the answers

Why are sodium and sugar commonly used as food additives?

For preservation and flavor purposes Signup and view all the answers

What does enzymatic browning primarily involve in fruits and mushrooms?

Reacting on phenolic compounds in the presence of O2 Signup and view all the answers

Study Notes

Bound Water and Water Content

Bound water is part of the chemical structure of proteins, carbohydrates, and fats, and is not free to act as a solvent for salts and sugars.
Bound water is not easily removed and exhibits essentially no vapor pressure, making it resistant to freezing or drying.
Foods contain varying levels of water content, ranging from 0% (oil) to 95% (tomato and watermelon).

Properties of Water

Water can exist as a gas (steam), liquid, or solid (ice) due to the distance between molecules, which is influenced by temperature.
Water expands and becomes less dense when frozen, causing ice to float and leading to container/pipe rupture and cell damage in plants and meat.
Pure water freezes at 0°C, but adding solutes (salt, sugar) can lower the freezing point.
Water requires 80 calories of heat to freeze and 540 calories to boil and vaporize.

Boiling Point and Pressure

The boiling point of water is 100°C at sea level, but decreases by 1°C for every 960 feet in altitude due to lower atmospheric pressure.
Water boils at a lower temperature in the mountains, affecting recipes and cooking times.
Pressure cookers speed up heating time by increasing atmospheric pressure, allowing water to boil at up to 112°C.

Hard and Soft Water

Most water contains impurities, including dissolved gases, organic materials, and mineral salts.
Minerals in water can be classified as neutral (pH 7), alkaline (provide hydroxyl ions), or form salts (e.g., NaCl).
Baking powder releases CO2 gas when combined with water, causing baked products to rise.

Food Preservation and Water Activity

Water activity (aw) determines the perishability of food, with high aw (fresh milk) and low aw (dried milk powder) examples.
Adding solutes (salt or sugar) decreases water activity, inhibiting microbial growth and preserving food.

Osmosis and Osmotic Pressure

Salt is used to preserve food by drawing water out of foods, causing bacteria to dehydrate and die.
Osmotic pressure is the force that draws water through a semipermeable membrane, affecting the concentration of solutes.

Lipids and Fats

Lipids are a group of compounds that include fats and oils, which are differentiated by their physical properties and sources.
Fats are solid at room temperature, usually derived from animal sources, while oils are liquid at room temperature, mostly derived from plant sources.

Enzymatic Reactions and Browning

Enzymatic reactions are used in food manufacturing and quality testing, including browning reactions.
Browning can occur through enzymatic or Maillard reactions, resulting in the formation of new flavor compounds and browning of foods.

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Description

Test your knowledge on the water content of various food items. Learn about the percentage of water in different foods like tomatoes, watermelon, cheese, mayonnaise, potatoes, and more.