Question

In fermented milk products, green apple flavour is associated with

• A. Lower diacetyl and lower acetaldehyde
• B. Lower diacetyl and lower lactic acid
• C. Lower diacetyl and excess acetaldehyde
• D. Lower diacetyl and excess lactic acid

Hint:

Fermented Milk Flavor Ratios:
Desirable Butter Aroma = High Diacetyl (Diacetyl : Acetaldehyde $\ge 3:1$).
Green Apple Grassy Defect = LOW DIACETYL + EXCESS ACETALDEHYDE.
Yoghurt Flavor = Acetaldehyde dominates ($20 - 40\text{ ppm}$).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Aroma ratio balance in cultured dairy products: green apple (yoghurt-like) flavor defect occurs in cultured buttermilk and butter when acetaldehyde is in excess relative to diacetyl ($ ext{Diacetyl} : ext{Acetaldehyde} < 3:1$).
Key Formula or Approach:
\[ \text{Ideal Cultured Butter Flavor Ratio: } \frac{\text{Diacetyl}}{\text{Acetaldehyde}} \approx 3:1 - 4:1 \quad \longleftrightarrow \quad \text{Defect: } \frac{\text{Low Diacetyl}}{\mathbf{Excess \text{ } Acetaldehyde}} \implies \mathbf{Green \text{ } Apple \text{ } Defect} \]

Step 2: Detailed Explanation:
In the sensory chemistry and aroma kinetics of fermented dairy products:
- In cultured buttermilk, dahi, and ripened butter, the characteristic rich 'buttery' aroma is governed by the Diacetyl to Acetaldehyde ratio (optimal ratio is $3:1\text{ to } 4:1$).
- If the aroma-producing leuconostoc/diacetylactis starter cultures fail to synthesize adequate diacetyl or if lactic starters overproduce acetaldehyde:
- The ratio drops drastically, creating an imbalance characterized by Lower Diacetyl and Excess Acetaldehyde (C).
- Acetaldehyde imparts a pungent, tart, grassy, 'Green Apple' (or harsh yoghurt-like) off-flavour in products where a smooth buttery profile is expected.

Step 3: Final Answer:
Thus, green apple flavour is associated with Lower diacetyl and excess acetaldehyde, corresponding to option (C).