Flavour Chemistry Questions and Answers

Answer: C

The incorrect statement is that saltiness is a taste that is mainly produced by chloride ions.

Salty taste is produced mainly by sodium ions (and to a lesser extent other alkali metal cations), which enter taste cells through epithelial sodium channels. The anion modifies the taste, which is why sodium chloride tastes saltier than sodium salts of larger anions, but chloride alone is not the stimulus.

The other statements are accepted: glutamate gives the savoury umami or 'meaty' taste of cheese and soy sauce; astringency is a drying sensation caused mainly by phenolic compounds such as tannins binding salivary proteins; and sourness comes from hydrogen ions sensed by acid-sensitive channels in taste cells.

Answer: B

The match is P-2, Q-4, R-1, S-3.

• Ginger: gingerol, its pungent phenolic compound.
• Green tea: epigallocatechin gallate (EGCG), the main catechin.
• Spinach: lutein, a xanthophyll carotenoid abundant in leafy greens.
• Turmeric: curcumin, the yellow curcuminoid.

The other options pair at least one commodity with another's constituent, such as curcumin with spinach or lutein with ginger.

Answer: D

The compound that does not produce caramel flavour is p-Amino benzoicacid.

The other three are sugar-degradation products with the caramel-like odour: 3-hydroxy-2-methylpyran-4-one is maltol, 2H-4-hydroxy-5-methylfuran-3-one is a hydroxyfuranone of the furaneol type, and 3-hydroxy-2-acetylfuran is isomaltol. All three share the enolized cyclic diketone structure that gives the burnt-sugar note.

p-Aminobenzoic acid is an aromatic amino acid derivative, a B-vitamin-related compound, and is not a caramelization product.

Answer: A

The characteristic flavour comes from 5-methyl-2-phenyl-2-hexenal.

During roasting, Maillard reactions and Strecker degradation of amino acids produce aldehydes; condensation of these yields 5-methyl-2-phenyl-2-hexenal, which is regarded as a key compound of the typical cocoa and chocolate aroma.

Cyclotene (a caramel, maple-like note), furaneol (a strawberry and caramel note) and maltol (a sweet, caramel note) are general products of sugar browning found in many cooked foods, not compounds unique to cocoa.

Answer: C

Allicin is found in garlic.

When a garlic clove is crushed or cut, the enzyme alliinase acts on the sulfur amino acid alliin and produces allicin, the compound responsible for raw garlic's pungent smell and much of its antimicrobial activity.

The other foods are known for different phytonutrients: grapes for resveratrol and anthocyanins, cauliflower for glucosinolates (which give sulforaphane and related compounds), and chilli for capsaicin, the source of its heat.

Answer: D

The correct matching is P-3; Q-1; R-2; S-5; T-4.

• Cloves: eugenol, the main component of clove oil (3).
• Butter: diacetyl, produced by fermentation in cultured cream (1).
• Orange: limonene, the dominant terpene of orange peel oil (2).
• Lemon: citral, which gives lemon its characteristic aroma (5).
• Garlic: diallyl disulfide, formed from allicin (4).

Option B swaps butter and orange, and options A and C mismatch cloves or garlic.