Food Science: Water Activity and Colligative Properties
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Questions and Answers

What is the main cause of osmo2c pressure?

  • The pressure applied to the water
  • The temperature of water
  • The presence of large molecules in water
  • The presence of small molecules that dissolve in water (correct)
  • Which process describes water movement from a hypotonic solution to a hypertonic solution?

  • Filtration
  • Reverse osmosis (correct)
  • Diffusion
  • Forward osmosis
  • In the context of colligative properties, what happens to the boiling point of a concentrated fruit juice when water evaporates?

  • It decreases significantly
  • It increases (correct)
  • It fluctuates randomly
  • It remains unchanged
  • Which of the following solutes is not typically associated with colligative properties?

    <p>Oxygen</p> Signup and view all the answers

    During forward osmosis, which statement is true about the movement of water?

    <p>Water moves without energy input</p> Signup and view all the answers

    What primarily influences the perishability of foods with the same water content?

    <p>The 'state' or thermodynamic 'activity' of water</p> Signup and view all the answers

    How does water activity (aw) affect food preservation?

    <p>It controls biochemical and microbiological reactions.</p> Signup and view all the answers

    What method can be used to prepare moisture sorption isotherms for food products?

    <p>Maintaining a weighed sample in a controlled humidity at constant temperature.</p> Signup and view all the answers

    What does water activity control during food processing?

    <p>Rate of moisture transfer and biochemical reactions</p> Signup and view all the answers

    Which of the following is NOT a method for achieving desired relative humidity environments for sorption isotherms?

    <p>Introducing artificial flavors</p> Signup and view all the answers

    What does the water activity (aw) measure?

    <p>The vapor pressure of water relative to pure water</p> Signup and view all the answers

    Which carbohydrate is primarily referred to as a sugar consisting of glucose and fructose?

    <p>Sucrose</p> Signup and view all the answers

    What percentage of the calories in the human diet worldwide is supplied by carbohydrates?

    <p>70-80%</p> Signup and view all the answers

    What is the primary biological purpose of starch in plants?

    <p>To supply energy for germination and growth</p> Signup and view all the answers

    Which enzyme is responsible for breaking down complex carbohydrates into glucose?

    <p>Amylase</p> Signup and view all the answers

    Which element is NOT a component of carbohydrates?

    <p>Nitrogen</p> Signup and view all the answers

    What can be said about the composition of carbohydrates in terms of their elemental makeup?

    <p>They are composed of carbon, hydrogen, and oxygen.</p> Signup and view all the answers

    Why is storing pure glucose in seeds considered detrimental?

    <p>It leads to immediate death of the seed.</p> Signup and view all the answers

    What is the primary composition of a water molecule?

    <p>Two hydrogen and one oxygen atom</p> Signup and view all the answers

    What unique thermodynamic property does supercooled liquid water possess?

    <p>It shows anomalies not present in ice</p> Signup and view all the answers

    Why does ice float on water?

    <p>Ice has a hexagonal pattern resulting in lower density than liquid water</p> Signup and view all the answers

    Which of the following correctly describes the role of water in biological systems?

    <p>It composes about 90% of our blood and brain</p> Signup and view all the answers

    In what form is water primarily found in plants?

    <p>As an intracellular and extracellular component</p> Signup and view all the answers

    What does water's role as a 'universal solvent' imply?

    <p>It dissolves almost everything, facilitating biochemical reactions</p> Signup and view all the answers

    What happens to water molecules when they freeze below 0°C at atmospheric pressure?

    <p>They arrange themselves into a hexagonal pattern</p> Signup and view all the answers

    Which branch of biological science is primarily involved in the study of water and its properties?

    <p>Food Chemistry</p> Signup and view all the answers

    What primarily causes foods to freeze faster than they thaw?

    <p>Differences in thermal properties of water and ice</p> Signup and view all the answers

    How does the thermal conductivity of ice compare to that of water at 0°C?

    <p>It is four times greater than that of water</p> Signup and view all the answers

    What is the heat capacity of ice compared to liquid water?

    <p>It is about one-half that of liquid water</p> Signup and view all the answers

    What is the H–O–H bond angle in a water molecule?

    <p>104.5°</p> Signup and view all the answers

    Which statement correctly describes water's structure?

    <p>It has two hydrogen atoms covalently bonded to one oxygen atom</p> Signup and view all the answers

    What property does the polar nature of water molecules cause?

    <p>Hydrogen atoms acquire a partial positive charge</p> Signup and view all the answers

    How does the thermal diffusivity of ice compare to that of water?

    <p>Ice has ninefold greater thermal diffusivity</p> Signup and view all the answers

    What is the van der Waals radius of the oxygen atom in a water molecule?

    <p>1.4 Å</p> Signup and view all the answers

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