Question

Major flavour compound in yoghurt is

• A. Diacetyl
• B. Acetaldehyde
• C. Methyl ketone
• D. Furfural

Hint:

Fermented Dairy Flavor Compounds:
YOGHURT = ACETALDEHYDE (20--40 ppm).
BUTTER = DIACETYL (2,3-butanedione from citrate).
BLUE CHEESE = METHYL KETONES (2-heptanone, 2-nonanone).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Sensory flavor chemistry of fermented milks: the symbiotic yoghurt consortium (Streptococcus thermophilus + Lactobacillus delbrueckii subsp. bulgaricus) produces 20--40 ppm acetaldehyde as the primary signature volatile aroma compound.
Key Formula or Approach:
\[ \text{Yoghurt Symbiosis: } \textit{S. thermophilus} + \textit{L. bulgaricus} \xrightarrow{\text{Threonine Aldolase}} \mathbf{Acetaldehyde (20 - 40\text{ ppm})} \implies \text{Signature Green, Tart Yoghurt Flavor} \]

Step 2: Detailed Explanation:
In dairy chemistry and the flavor technology of fermented milks:
- The distinctive, clean, tart, refreshing aroma that defines commercial Yoghurt is primarily attributed to Acetaldehyde (Ethanal) (B), present in the finished product at concentrations of $20\text{ to 40\text{ mg/kg (ppm)}$}.
- Acetaldehyde is biosynthesized during symbiotic incubation ($42^\circ - 43^\circ ext{C}$) principally by Lactobacillus delbrueckii subsp. bulgaricus via the threonine aldolase enzymatic pathway. Minor volatile components (diacetyl, acetoin, acetone) provide rounded background complexity, but acetaldehyde is overwhelmingly the major, indispensable flavor compound of yoghurt.

Step 3: Final Answer:
Therefore, the major flavour compound in yoghurt is Acetaldehyde, matching option (B).