Fermentation Products: Analysis of wine, beer, spirits and vinegar MCQs With Answer

Introduction

This quiz collection focuses on the analysis of fermentation products—wine, beer, spirits and vinegar—targeted to M.Pharm students studying MPA 104T Food Analysis. It highlights analytical principles, instrumentation, sample preparation and interpretation of key quality parameters such as alcohol strength, volatile acidity, residual sugars, methanol, sulfur dioxide, esters and fusel oils. Questions emphasize pharmacopoeial and laboratory methods (distillation, ebulliometry, GC-FID, headspace GC, enzymatic assays, titrations and pycnometry) and microbiological processes that influence analytical outcomes. Use these MCQs to reinforce practical understanding of testing procedures, critical controls and safety concerns relevant to fermented beverages and vinegar in a pharmaceutical analytical context.

Q1. Which microorganism is most commonly responsible for primary alcoholic fermentation in wine and beer?

• Saccharomyces cerevisiae
• Lactobacillus plantarum
• Acetobacter aceti
• Zymomonas mobilis

Correct Answer: Saccharomyces cerevisiae

Q2. The principle behind an ebulliometer used for determining alcohol by volume is based on which physical property?

• Boiling point depression of the sample compared to water
• Refractive index differences between ethanol and water
• Density measurement using a hydrometer
• Infrared absorbance of C–H bonds

Correct Answer: Boiling point depression of the sample compared to water

Q3. Which analytical method is classically used to determine volatile acidity in wine?

• Steam distillation followed by titration
• Headspace GC-FID quantification
• Enzymatic assay using alcohol oxidase
• Refractive index measurement

Correct Answer: Steam distillation followed by titration

Q4. Total acidity in vinegar is commonly expressed as which compound and determined by which technique?

• Expressed as acetic acid; determined by titration with standardized NaOH
• Expressed as tartaric acid; determined by HPLC
• Expressed as lactic acid; determined by GC-MS
• Expressed as citric acid; determined by refractometry

Correct Answer: Expressed as acetic acid; determined by titration with standardized NaOH

Q5. What is the primary biochemical source of methanol in fermented beverages?

• Pectin demethylation in fruit-based musts
• Fermentation of glucose by Saccharomyces
• Oxidation of ethanol during aging
• Contamination from distillation equipment

Correct Answer: Pectin demethylation in fruit-based musts

Q6. For accurate quantification of ethanol and congeners in spirits, which analytical setup is most widely used?

• Gas chromatography with flame ionization detector (GC-FID) using an internal standard
• UV-Visible spectrophotometry at 280 nm
• Refractive index measurement with a refractometer
• Paper chromatography with colorimetric detection

Correct Answer: Gas chromatography with flame ionization detector (GC-FID) using an internal standard

Q7. Which method provides the most specific and quantitative measurement of residual glucose and fructose in wine?

• Enzymatic assays using glucose and fructose-specific enzymes
• Hydrometer-based estimation from specific gravity
• Phenol-sulfuric acid colorimetric total sugar test
• Headspace GC for volatile sugars

Correct Answer: Enzymatic assays using glucose and fructose-specific enzymes

Q8. Between Ripper titration and aeration-oxidation (AO) methods for measuring free sulfur dioxide (SO2) in wine, which is considered more accurate and why?

• Aeration-oxidation (AO) because it separates SO2 from interfering matrix components before titration
• Ripper titration because it is faster and equally specific
• Ripper titration because it uses potentiometric detection for better precision
• Aeration-oxidation because it measures total sulfates not SO2

Correct Answer: Aeration-oxidation (AO) because it separates SO2 from interfering matrix components before titration

Q9. Malolactic fermentation in wine primarily causes which chemical change?

• Conversion of malic acid to lactic acid, reducing perceived acidity
• Oxidation of ethanol to acetic acid, increasing volatile acidity
• Reduction of sugars to ethanol and CO2
• Formation of methanol from pectins

Correct Answer: Conversion of malic acid to lactic acid, reducing perceived acidity

Q10. Which analytical technique is especially suitable for profiling volatile aroma compounds in spirits and detecting trace congeners?

• Headspace gas chromatography–mass spectrometry (HS-GC-MS)
• Direct UV spectroscopy of the bulk spirit
• Viscometry to assess viscosity-related volatiles
• Paper electrophoresis of volatile fractions

Correct Answer: Headspace gas chromatography–mass spectrometry (HS-GC-MS)

Q11. The common hydrometer method to estimate percent alcohol by volume in fermented beverages relies on which measurement?

• Difference between original gravity (OG) and final gravity (FG) of the wort or must
• Direct reading of refractive index of the final beverage
• Boiling point measurement with an ebulliometer
• Colorimetric ethanol assay

Correct Answer: Difference between original gravity (OG) and final gravity (FG) of the wort or must

Q12. Fusel oils in distilled spirits refer to which class of compounds?

• Higher (C3–C6) alcohols such as isoamyl and isobutanol
• Short-chain fatty acids like acetic and propionic acid
• Sulfur-containing volatile thiols
• Polyphenolic tannins contributing to color

Correct Answer: Higher (C3–C6) alcohols such as isoamyl and isobutanol

Q13. Why is total sulfur dioxide routinely measured in wine analysis?

• Because SO2 acts as an antioxidant and antimicrobial preservative affecting shelf life and stability
• Because SO2 increases ethanol concentration by chemical reduction
• Because SO2 is the primary sweetening agent in fortified wines
• Because SO2 is required to convert malic acid to lactic acid

Correct Answer: Because SO2 acts as an antioxidant and antimicrobial preservative affecting shelf life and stability

Q14. The microbial genus responsible for converting ethanol to acetic acid during vinegar production is:

• Acetobacter
• Saccharomyces
• Lactobacillus
• Clostridium

Correct Answer: Acetobacter

Q15. In spirit distillation, the fraction termed the “hearts” refers to:

• The central fraction collected after discarding the volatile “heads” and before the higher-boiling “tails”
• The initial highly volatile fraction rich in methanol
• The final fraction containing primarily water and heavy congeners
• The azeotropic mixture of ethanol and water

Correct Answer: The central fraction collected after discarding the volatile “heads” and before the higher-boiling “tails”

Q16. Which laboratory tool provides the most precise determination of sample density for small volumes of alcoholic beverages?

• Pycnometer
• Glass hydrometer
• Refractometer
• Capillary viscometer

Correct Answer: Pycnometer

Q17. Which GC detector is most commonly used for routine quantitative analysis of ethanol and other volatile organic compounds in beverages?

• Flame ionization detector (FID)
• Electron capture detector (ECD)
• Thermal conductivity detector (TCD)
• Photoionization detector (PID)

Correct Answer: Flame ionization detector (FID)

Q18. Which analytical parameter better correlates with perceived sourness in wine, titratable acidity or pH, and why?

• Titratable acidity, because it measures total titratable protons and buffering capacity that influence taste
• pH, because it measures total acid content more directly
• pH, because it quantifies volatile acidity exclusively
• Titratable acidity, because it measures only volatile acids

Correct Answer: Titratable acidity, because it measures total titratable protons and buffering capacity that influence taste

Q19. Esters that impart fruity aromas to wine are formed primarily by which chemical reaction during fermentation and aging?

• Esterification between alcohols and organic acids
• Oxidation of ethanol to acetaldehyde
• Hydrolysis of polysaccharides
• Reduction of sulfates to thiols

Correct Answer: Esterification between alcohols and organic acids

Q20. For selective detection of trace volatile sulfur compounds (e.g., H2S, mercaptans) in fermented beverages, which GC detector is highly suitable?

• Gas chromatography with sulfur chemiluminescence detector (SCD)
• GC with flame ionization detector (FID) without selective interface
• High-performance liquid chromatography with UV detection
• Refractometric detection after distillation

Correct Answer: Gas chromatography with sulfur chemiluminescence detector (SCD)

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