Question

Development of what level of acidity in Horrall-Elliker test indicates a good and active culture for cheese making?

• A. 0.10% lactic acid
• B. 0.20% lactic acid
• C. 0.30% lactic acid
• D. 0.40% lactic acid

Hint:

Starter Activity Tests:
Horrall-Elliker Test ($3.5\text{ h}$ at $37^\circ\text{C}$) $\rightarrow$ Active starter develops $\ge 0.35 - 0.40\%$ Lactic Acid.
Whitehead-Cox Test ($6\text{ h}$ at $38^\circ\text{C}$).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Starter activity testing in cheese making: the Horrall-Elliker activity test measures lactic acid development in sterile reconstituted skim milk after 3.5 hours incubation at 37°C; acidity $\ge 0.35 - 0.40\%$ indicates a highly active starter culture.
Key Formula or Approach:
\[ \text{Horrall-Elliker Test (3.5 h at 37}^\circ\text{C)}: \text{Slow/Inactive } (< 0.30\%) \mid \text{Fair } (0.30 - 0.35\%) \mid \mathbf{Active / Good } (\mathbf{\ge 0.35 - 0.40\% \text{ Lactic Acid}}) \]

Step 2: Detailed Explanation:
In cheese starter culture quality control and activity assays:
- The Horrall-Elliker Activity Test (Horrall and Elliker, 1950) evaluates the acid-producing vitality of mesophilic lactic starter cultures (Lactococcus lactis) prior to vat inoculation:
1. Inoculate $3\%$ of the starter culture into $10\text{ mL}$ of sterile $10\%$ reconstituted non-fat dry milk.
2. Incubate in a water bath at 37°C for 3.5 hours.
3. Titrate developed titratable acidity using $0.1\text{ N NaOH}$:
- An acidity development of 0.35% to 0.40% lactic acid (or $\ge 0.40\%$ lactic acid) (D) classifies the culture as 'Good and Highly Active', ensuring rapid pH drop during curd cheddarization.

Step 3: Final Answer:
Hence, acidity level of 0.40% lactic acid indicates a good and active culture, matching option (D).