Food Preservatives Practice Questions
20 free Food Preservatives practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following chemical compounds is most commonly used as a preservative in fruit juices and squashes to inhibit the growth of molds and yeasts?
- A Sodium benzoate
- B Calcium carbonate
- C Sodium bicarbonate
- D Sodium sulfate
Correct answer: Sodium benzoate
Sodium benzoate is the sodium salt of benzoic acid and is widely used in acidic foods. It works by entering the individual cells of microorganisms and increasing the intracellular acidity, effectively halting their growth.
Common salt (Sodium Chloride) preserves meat and fish by which of the following processes?
- A Plasmolysis
- B Oxidation
- C Neutralization
- D Hydrogenation
Correct answer: Plasmolysis
High concentrations of salt create a hypertonic environment, drawing water out of microbial cells via osmosis. This process, known as plasmolysis, dehydrates the microbes and prevents them from multiplying.
Which gas is used in the packaging of potato chips to prevent the oxidation of fats and oils, thereby preventing rancidity?
- A Oxygen
- B Carbon dioxide
- C Nitrogen
- D Chlorine
Correct answer: Nitrogen
Nitrogen is an inert gas that displaces oxygen in the packaging. By removing oxygen, the chemical reaction of oxidation—which causes fats to smell and taste bad (rancidity)—is significantly slowed down.
The use of high concentrations of sugar in jams and jellies serves as a preservative by:
- A Reducing the availability of water for microbial growth
- B Increasing the acidity of the food
- C Acting as a direct chemical poison that kills bacteria outright
- D Bleaching the colors of the fruit
Correct answer: Reducing the availability of water for microbial growth
Similar to salt, sugar reduces the 'water activity' in food. By binding with water molecules, sugar makes the environment too dry for most bacteria and fungi to survive.
Which of the following is an example of a 'Class II' preservative according to the Food Safety and Standards Authority?
- A Vinegar
- B Sugar
- C Edible vegetable oils and fats
- D Potassium metabisulfite
Correct answer: Potassium metabisulfite
Class I preservatives are natural substances like salt and sugar, whereas Class II are synthetic chemicals. Potassium metabisulfite is a synthetic preservative commonly used in wines and dried fruits to prevent spoilage and browning.
Which acid is naturally present in vinegar and acts as a preservative by lowering the pH of the food item?
- A Acetic acid
- B Citric acid
- C Lactic acid
- D Tartaric acid
Correct answer: Acetic acid
Vinegar contains about 5-8% acetic acid. The acidic environment inhibits the growth of many spoilage-causing bacteria, which is why it is the primary ingredient in pickling.
Sulfur dioxide (SO2) is frequently added to dried fruits and wines primarily to:
- A Improve the natural sweetness of the fruit pulp
- B Act as an antioxidant and antimicrobial agent
- C Increase the protein content
- D Shorten the drying time
Correct answer: Act as an antioxidant and antimicrobial agent
Sulfur dioxide prevents both microbial spoilage and the enzymatic browning that occurs in fruits. In wine, it helps maintain the fresh flavor and prevents the growth of unwanted wild yeasts.
BHA (Butylated Hydroxyanisole) and BHT (Butylated Hydroxytoluene) are added to oil-based foods to act as:
- A Antioxidants
- B Emulsifiers
- C Flavor enhancers
- D Coloring agents
Correct answer: Antioxidants
BHA and BHT are synthetic antioxidants that react with free radicals. This prevents the oxidative breakdown of oils, extending the shelf life of products like butter, lard, and cereals.
Which of the following preservatives is commonly used in bread to prevent the growth of 'rope' bacteria and molds?
- A Sodium nitrate
- B Calcium propionate
- C Potassium metabisulfite
- D Citric acid
Correct answer: Calcium propionate
Calcium propionate is the salt of propionic acid. It is particularly effective against molds and certain bacteria in baked goods without interfering with the action of the baking yeast.
Sodium nitrite and sodium nitrate are specifically used in the preservation of processed meats like ham and bacon to prevent the growth of which deadly bacterium?
- A Salmonella
- B Clostridium botulinum
- C Escherichia coli
- D Listeria monocytogenes
Correct answer: Clostridium botulinum
Nitrites are highly effective at inhibiting the spores of Clostridium botulinum, which causes botulism. They also help maintain the characteristic pink color of cured meats.
Which naturally occurring preservative is found in many citrus fruits and is used to prevent the browning of cut fruits?
- A Malic acid
- B Ascorbic acid
- C Benzoic acid
- D Salicylic acid
Correct answer: Ascorbic acid
Ascorbic acid is a powerful antioxidant. It reacts with oxygen before the oxygen can react with enzymes in the fruit, thereby preventing the oxidative browning (enzymatic browning) of sliced apples or peaches.
Sorbic acid and its salts (sorbates) are primarily effective against which type of spoilage organisms?
- A Molds and yeasts
- B Thermophilic bacteria
- C Acetic bacteria
- D Anaerobic bacteria
Correct answer: Molds and yeasts
Sorbates are used in cheese, wine, and baked goods. They are most active at a lower pH and specifically target the metabolic processes of fungi rather than bacteria.
The process of 'Cold Pasteurization' refers to which method of food preservation?
- A Freezing
- B Vacuum packaging
- C Irradiation
- D Lyophilization
Correct answer: Irradiation
Food irradiation uses ionizing radiation to kill bacteria and parasites without significantly heating the food. Because the food stays cool during the process, it is sometimes called cold pasteurization.
Which of the following is a disadvantage of using sulfur-based preservatives like metabisulfites?
- A They are far more expensive than other additives
- B They can trigger allergic reactions in asthmatic individuals
- C They make the treated food noticeably salty
- D They require the food to be stored below freezing at all times
Correct answer: They can trigger allergic reactions in asthmatic individuals
Sulfites can cause severe respiratory distress and allergic reactions in sensitive people. Because of this, food labeling laws require the presence of sulfites to be clearly disclosed.
What is the primary role of 'Chelating Agents' like EDTA in food preservation?
- A To add a sour taste
- B To kill bacteria directly
- C To bind with metal ions that catalyze oxidation
- D To increase the vitamin content of packaged foods
Correct answer: To bind with metal ions that catalyze oxidation
Metal ions like copper and iron can catalyze the oxidation of fats. Chelating agents like EDTA grab these metal ions and lock them away, preventing them from starting the spoilage process.
The preservative effect of 'Fermentation' is primarily due to the production of which two substances by microbes?
- A Oxygen and Sugar
- B Lactic acid and Alcohol
- C Water and Carbon dioxide
- D Protein and Methane
Correct answer: Lactic acid and Alcohol
During fermentation, beneficial bacteria produce lactic acid or alcohol as byproducts. These substances lower the pH or increase the toxicity of the environment for harmful spoilage bacteria.
Which of the following describes 'Lyophilization' as a preservation technique?
- A Heating food to 100°C for an hour
- B Storing food in a high-pressure chamber
- C Freeze-drying food under a vacuum
- D Smoking food over a wood fire
Correct answer: Freeze-drying food under a vacuum
Lyophilization involves freezing the food and then reducing the surrounding pressure to allow the frozen water to sublimate directly from ice to vapor. This removes moisture while preserving the food's structure and nutrients.
Which organic acid, often found in cranberries, is used in its salt form to preserve carbonated drinks?
- A Benzoic acid
- B Stearic acid
- C Oleic acid
- D Palmitic acid
Correct answer: Benzoic acid
Benzoic acid occurs naturally in berries. Its salt, sodium benzoate, is the most widely used chemical preservative in the world for carbonated soft drinks due to its high solubility and effectiveness in acidic conditions.
Nisin is a unique food preservative because it is a/an:
- A Synthetically produced inorganic mineral salt
- B Petroleum derivative
- C Antibiotic peptide produced by bacteria
- D Heavy metal salt
Correct answer: Antibiotic peptide produced by bacteria
Nisin is a bacteriocin produced by the bacterium Lactococcus lactis. It is used in processed cheese and meats as a 'natural' preservative because it is a protein that is easily digested by humans.
Why is 'Paraben' (Para-hydroxybenzoate) sometimes used in food despite being more common in cosmetics?
- A It is far cheaper to manufacture than sorbic acid
- B It adds a mild fruity aroma to beverages
- C It is completely broken down by the human digestive system
- D It is effective across a wider pH range than benzoic acid
Correct answer: It is effective across a wider pH range than benzoic acid
Most organic acid preservatives only work in highly acidic foods. Parabens are effective at more neutral pH levels (up to pH 8), making them useful for preserving products that aren't naturally tart.