Carbohydrates in food: Classification, analysis and changes during processing MCQs With Answer

Carbohydrates in Food: Classification, Analysis and Changes During Processing is an essential review for M.Pharm students preparing for MPA 104T Food Analysis. This blog provides focused multiple-choice questions that cover carbohydrate classification (mono-, di-, oligo- and polysaccharides), analytical techniques (colorimetric assays, chromatographic separations, detectors and sample preparation), and the chemical and physical changes carbohydrates undergo during processing (gelatinization, retrogradation, Maillard reaction, caramelization, inversion and resistant starch formation). The questions emphasize practical laboratory implications, interpretation of assays and processing-related quality changes relevant to pharmaceutical and nutraceutical formulations. Use these MCQs to strengthen conceptual understanding and analytical problem-solving skills in carbohydrate analysis.

Q1. Which of the following carbohydrates is a non-reducing sugar?

• Glucose
• Fructose
• Lactose
• Sucrose

Correct Answer: Sucrose

Q2.Which qualitative test produces a violet or purple ring at the junction of two layers and is sensitive for trace carbohydrates?

• Benedict’s test
• Molisch’s test
• Iodine test
• Barfoed’s test

Correct Answer: Molisch’s test

Q3. The phenol–sulfuric acid method for total carbohydrate estimation is based on which principle?

• Reduction of copper(II) to copper(I)
• Formation of furfural derivatives from dehydrated sugars that react with phenol to form a colored complex
• Complexation of iodine with helical polysaccharides
• Enzymatic conversion of glucose to gluconic acid with NADH formation

Correct Answer: Formation of furfural derivatives from dehydrated sugars that react with phenol to form a colored complex

Q4. Which analytical technique is most suitable for resolving and detecting native (underivatized) monosaccharides with high sensitivity?

• Gas chromatography–mass spectrometry (GC–MS) without derivatization
• Reverse-phase HPLC with UV detection
• High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD)
• Thin layer chromatography with ninhydrin stain

Correct Answer: High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD)

Q5. The DNS (3,5-dinitrosalicylic acid) assay is commonly used to measure which parameter in food carbohydrate analysis?

• Total dietary fiber
• Non-reducing sugars
• Reducing sugars
• Starch molecular weight

Correct Answer: Reducing sugars

Q6. The iodine test yields a characteristic blue-black coloration with which starch component?

• Amylopectin only
• Amylose only
• Cellulose
• Lignin

Correct Answer: Amylose only

Q7. Which description best defines starch gelatinization during heating in excess water?

• Enzymatic hydrolysis of amylose to maltose
• Crystalline melting of granular regions accompanied by granule swelling, loss of crystallinity and leaching of amylose
• Formation of Maillard brown pigments
• Oxidative crosslinking of polysaccharide chains

Correct Answer: Crystalline melting of granular regions accompanied by granule swelling, loss of crystallinity and leaching of amylose

Q8. Retrogradation of starch during cooling primarily results in which of the following effects?

• Increased solubility and loss of texture
• Re-association of amylose/amylopectin chains causing firming, syneresis and decreased digestibility
• Immediate enzymatic hydrolysis to monosaccharides
• Increased sweetness due to sugar formation

Correct Answer: Re-association of amylose/amylopectin chains causing firming, syneresis and decreased digestibility

Q9. The Maillard reaction in food systems requires which key reactants?

• Non-reducing sugars and polyphenols
• Reducing sugars and free amino groups (from proteins or amino acids)
• Lipids and ascorbic acid
• Cellulose and water under neutral pH

Correct Answer: Reducing sugars and free amino groups (from proteins or amino acids)

Q10. Caramelization differs from the Maillard reaction in that caramelization involves:

• Reaction of sugars with amino acids producing melanoidins
• Thermal dehydration and pyrolysis of sugars without amino nitrogen, producing caramel colors and volatiles
• Enzymatic browning catalyzed by polyphenol oxidase
• Crosslinking of polysaccharides with proteins via transglutaminase

Correct Answer: Thermal dehydration and pyrolysis of sugars without amino nitrogen, producing caramel colors and volatiles

Q11. Which type of resistant starch is formed mainly by retrogradation of gelatinized starch after cooling?

• RS1 (physically inaccessible starch)
• RS2 (native granular starch)
• RS3 (retrograded starch)
• RS4 (chemically modified starch)

Correct Answer: RS3 (retrograded starch)

Q12. For regulatory quantification of total dietary fiber in food, which method is considered authoritative and widely used?

• Phenol–sulfuric acid colorimetry
• AOAC enzymatic–gravimetric method
• DNS reducing sugar assay
• Gas chromatography of volatile derivatives

Correct Answer: AOAC enzymatic–gravimetric method

Q13. Sucrose inversion produces which monosaccharides, and which condition accelerates inversion?

• Glucose and galactose; alkaline pH accelerates inversion
• Glucose and fructose; acid catalysis and heat accelerate inversion
• Fructose and mannose; presence of lipase accelerates inversion
• Galactose and mannose; low temperature accelerates inversion

Correct Answer: Glucose and fructose; acid catalysis and heat accelerate inversion

Q14. Prior to GC analysis, monosaccharides typically require derivatization; which derivatization is commonly used to make volatile, GC-amenable derivatives?

• Silylation to form trimethylsilyl (TMS) derivatives
• Direct injection without derivatization
• Complexation with iodine
• Enzymatic phosphorylation

Correct Answer: Silylation to form trimethylsilyl (TMS) derivatives

Q15. Which detector is commonly paired with conventional HPLC for quantification of neutral sugars and oligosaccharides when samples are not derivatized?

• UV detector at 280 nm
• Refractive index detector (RID)
• Diode array detector at 214 nm
• Fluorescence detector with FITC labeling

Correct Answer: Refractive index detector (RID)

Q16. Molisch’s reagent contains which key reagent that reacts with dehydrated sugars to give a purple ring?

• Alpha-naphthol in ethanol
• Biuret reagent (copper sulfate and alkaline tartrate)
• Benedict’s solution (copper sulfate in alkaline tartrate)
• Iodine–potassium iodide solution

Correct Answer: Alpha-naphthol in ethanol

Q17. Which formulation factor is most likely to lower the glycemic index of a carbohydrate-rich food?

• Increasing the proportion of rapidly digestible starch
• Adding high levels of simple sugars
• Incorporating resistant starch and soluble fiber
• Reducing fat and protein content to zero

Correct Answer: Incorporating resistant starch and soluble fiber

Q18. During strong acid hydrolysis of polysaccharides, which monosaccharide is particularly susceptible to dehydration and degradation to hydroxymethylfurfural (HMF)?

• Glucose (an aldose) is most susceptible
• Fructose (a ketose) is especially susceptible
• Mannose is completely stable
• All monosaccharides are equally stable

Correct Answer: Fructose (a ketose) is especially susceptible

Q19. Benedict’s test detects reducing sugars based on which chemical change?

• Oxidation of aldehyde/ketose groups with reduction of Cu2+ to Cu+ forming a red Cu2O precipitate
• Formation of a blue iodine–polysaccharide complex
• Dehydration of sugars to furfural followed by color development with phenol
• Enzymatic oxidation producing NADH measured at 340 nm

Correct Answer: Oxidation of aldehyde/ketose groups with reduction of Cu2+ to Cu+ forming a red Cu2O precipitate

Q20. For accurate quantification of oligosaccharides such as raffinose and stachyose in complex food matrices, which analytical approach is most suitable?

• Simple sugar paper chromatography with aniline spray
• HPAEC-PAD or HPLC with appropriate column and detection designed for oligosaccharides
• Gravimetric precipitation after ethanol extraction
• UV spectrophotometry at 260 nm

Correct Answer: HPAEC-PAD or HPLC with appropriate column and detection designed for oligosaccharides

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