Podcast
Questions and Answers
What characteristic of bound water makes it not easily removed from food items?
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?
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?
What is the approximate water content in potato?
- 91%
- 5%
- 40%
- 74% (correct)
How does the addition of solutes like salt or sugar affect the freezing point of water?
How does the addition of solutes like salt or sugar affect the freezing point of water?
Which food item has the lowest water content?
Which food item has the lowest water content?
What happens to cells in plants/meat when frozen due to the expansion of water?
What happens to cells in plants/meat when frozen due to the expansion of water?
What does an alkaline solution provide?
What does an alkaline solution provide?
What is the result of combining baking powder with water?
What is the result of combining baking powder with water?
What does water activity (aw) determine in food preservation?
What does water activity (aw) determine in food preservation?
Which type of lipids are solid at room temperature?
Which type of lipids are solid at room temperature?
What role does salt play in preserving food?
What role does salt play in preserving food?
What happens to bacteria when they contact heavily salted food?
What happens to bacteria when they contact heavily salted food?
What happens when a gram of ice absorbs 80 calories of heat?
What happens when a gram of ice absorbs 80 calories of heat?
At what temperature does water start boiling at sea level?
At what temperature does water start boiling at sea level?
Why does water boil at a lower temperature in the mountains?
Why does water boil at a lower temperature in the mountains?
How does a pressure cooker speed up the heating time compared to a regular open pot?
How does a pressure cooker speed up the heating time compared to a regular open pot?
What is the main reason recipes are usually modified for elevations above 3,000 feet?
What is the main reason recipes are usually modified for elevations above 3,000 feet?
What is the purpose of latent heat in changing the state of water from solid to liquid or steam?
What is the purpose of latent heat in changing the state of water from solid to liquid or steam?
What is the function of fats in food related to appearance?
What is the function of fats in food related to appearance?
Which type of protein is mostly complete and mainly sourced from animals?
Which type of protein is mostly complete and mainly sourced from animals?
What process occurs when proteins denature due to extreme pH or heat?
What process occurs when proteins denature due to extreme pH or heat?
Which protein function involves the capability to attract water and form a gel?
Which protein function involves the capability to attract water and form a gel?
Which protein characteristic allows for bread dough to rise during baking?
Which protein characteristic allows for bread dough to rise during baking?
What distinguishes complete proteins from incomplete proteins?
What distinguishes complete proteins from incomplete proteins?
What is the main purpose of adding antioxidants like vitamin A, C, E, and selenium to foods?
What is the main purpose of adding antioxidants like vitamin A, C, E, and selenium to foods?
Which of the following is NOT a function of vitamin and mineral in regulating metabolic functions?
Which of the following is NOT a function of vitamin and mineral in regulating metabolic functions?
What is the Maillard reaction primarily responsible for in food preparation?
What is the Maillard reaction primarily responsible for in food preparation?
What does the term 'buffering' refer to in food science?
What does the term 'buffering' refer to in food science?
Why are sodium and sugar commonly used as food additives?
Why are sodium and sugar commonly used as food additives?
What does enzymatic browning primarily involve in fruits and mushrooms?
What does enzymatic browning primarily involve in fruits and mushrooms?
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.
