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Food Science Practice Test — Medium Level

A free 10-question Food Science practice test for Science Olympiad, written at regional and state level. Every question and answer choice is listed below — correct answers and scoring are revealed when you take the timed test.

10 questions15 min timedMedium levelAI-generated — verify answers against reliable sources
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1. Whole cow’s milk is described as being three kinds of mixtures at once. Which component is CORRECTLY matched with the type of mixture it primarily forms in milk?

  • A.A) Fat globules – true solution
  • B.B) Casein micelles – colloidal dispersion
  • C.C) Lactose – emulsion
  • D.D) Minerals (salts) – emulsion

2. A student wants to maximize cheese yield from a limited volume of milk. Based on typical composition, which milk source would give the highest mass of cheese per liter, assuming similar processing?

  • A.A) Human milk, because it has the highest lactose content
  • B.B) Skim cow’s milk, because it has almost no fat
  • C.C) Sheep milk, because it has the highest fat and protein content
  • D.D) Standard whole cow’s milk, because its water content is lowest of all milks

3. In a curd-forming lab, 200.0 g of whole milk are acidified to pH 4.6 and drained, producing 24.0 g of curds. What is the percent curd yield by mass, and which main milk protein is primarily responsible for these curds?

  • A.A) 9.6% curd; whey proteins form the curd
  • B.B) 12.0% curd; casein forms the curd
  • C.C) 24.0% curd; whey proteins form the curd
  • D.D) 88.0% curd; casein forms the curd

4. Which of the following BEST explains why yogurt becomes thick and tangy as it ferments?

  • A.A) Whey proteins reach their isoelectric point and precipitate at pH 6.6, trapping water
  • B.B) Lactic acid bacteria convert lactose to lactic acid, lowering pH toward 4.6 so casein gels
  • C.C) Lactose crystallizes out, forming a network of sugar crystals that thickens the milk
  • D.D) Pasteurization during yogurt making denatures casein and causes it to precipitate

5. A student makes ice cream mix and then cools it in a 0 °C ice bath with no salt added. The mix does not freeze, even after a long time. Which is the BEST scientific explanation?

  • A.A) The ice bath is too cold; milk fat cannot crystallize below 0 °C
  • B.B) The mix’s freezing point is below 0 °C because of dissolved sugars, so 0 °C ice is not cold enough to freeze it
  • C.C) The mix’s freezing point is above 0 °C because lactose raises the freezing point, so it cannot freeze in ice
  • D.D) The mix must first be pasteurized to allow ice crystals to nucleate and grow

6. An ice cream mix is cooled in a brine made by dissolving sucrose to create a 0.50 molal sugar solution. Treating sucrose as a non-dissociating solute (i = 1) and using Kf(water) = 1.86 °C·kg/mol, what is the approximate freezing point of the brine?

  • A.A) −0.5 °C
  • B.B) −0.9 °C
  • C.C) −1.9 °C
  • D.D) −3.7 °C

7. A batch of ice cream is made from 200 mL of liquid mix and whipped/frozen to a final volume of 320 mL. What is the overrun of this ice cream, and how does it compare to typical commercial products?

  • A.A) 20%; lower than typical standard ice cream
  • B.B) 40%; similar to premium ice cream with low overrun
  • C.C) 60%; moderate, between premium and standard ice cream
  • D.D) 160%; higher than typical standard ice cream

8. A person drinks a small glass of regular milk and experiences gas and cramping but NO hives, swelling, or breathing problems. Later they drink lactose-free milk and feel fine. Which statement BEST explains what is happening?

  • A.A) They have a milk allergy caused by an immune reaction to lactose, which lactose-free milk does not contain
  • B.B) They are lactose intolerant because they lack enough lactase to digest lactose into glucose and galactose
  • C.C) They are allergic to casein, and lactose-free milk contains no casein, so it is safe for them
  • D.D) They are sensitive to milk fat, and lactose-free milk has a lower fat content, preventing symptoms

9. During butter-making, cream is chilled to about 13 °C before churning. Which combination of factors at this temperature MOST directly helps cream invert from an oil-in-water emulsion to a water-in-oil emulsion (butter)?

  • A.A) All fat is completely liquid, so fat globules stay separate and resist coalescence
  • B.B) All fat is completely solid, so fat cannot move to air bubble surfaces during churning
  • C.C) Some fat is solid and some is liquid, allowing globules to partially coalesce when membranes are damaged
  • D.D) The milk fat globule membranes are fully intact, preventing fat globules from sticking together

10. Why is HTST pasteurization (72 °C for 15 s) followed by rapid cooling an effective preservation method for milk without significantly changing its flavor?

  • A.A) It kills all microorganisms and their spores, making the milk completely sterile at room temperature
  • B.B) It inactivates key pathogens and enzymes like alkaline phosphatase while limiting heat damage to proteins and flavor
  • C.C) It removes most of the water in milk, lowering water activity enough to stop microbial growth
  • D.D) It raises the pH above 7.0, creating an environment where foodborne bacteria cannot grow

Questions are AI-generated for Food Science practice and can contain mistakes — check answers against reliable sources. Take the timed version to see correct answers, scoring, and explanations: start the Food Science test.