Question

Corrected lactometer reading is to be determined from observed lactometer reading considering the following parameters. Select the correct combination

• A. Temperature of milk & Density of milk
• B. Fat % of milk & Viscosity of milk
• C. Protein% of milk & Temperature of milk
• D. Temperature of milk & Fat% of milk

Hint:

Lactometer readings are highly temperature-dependent because fat density changes rapidly with temperature.
Therefore, both temperature and fat content are needed to correctly interpret milk density and calculate solids-not-fat (SNF).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A lactometer is a hydrometer designed to measure the observed specific gravity (density) of milk at a specific calibration temperature (e.g., $15.5^\circ\text{C}$, $20^\circ\text{C}$, or $27^\circ\text{C}$).
Because milk density varies with temperature, if the milk is tested at any temperature other than the calibration temperature, a correction must be applied to find the Corrected Lactometer Reading (CLR).

Step 2: Detailed Explanation:
Let us analyze the standard calculations used in quality control:
To find the CLR from the Observed Lactometer Reading (OLR), we apply a temperature correction factor (typically adding or subtracting about \( 0.1 \) to \( 0.2 \) lactometer degrees per degree deviation from the calibration temperature).
Furthermore, during the calculation of solids-not-fat (SNF) or total solids (TS) of milk, the CLR is mathematically combined with the Fat percentage of the milk using standard Richmond formulas, such as:
\[ \text{SNF\%} = \frac{\text{CLR}}{4} + 0.21 \times \text{Fat\%} + 0.36 \]
Because the true specific gravity and physical state of fat (solidified versus liquid) also influence the density at different temperatures, both the Temperature of the milk and the Fat% of the milk are critical parameters considered when accurately standardizing and correcting lactometer measurements for milk solids calculations.
Therefore, option 4 is the correct combination.

Step 3: Final Answer:
The corrected lactometer reading and related solid calculations are determined considering the Temperature of milk and Fat% of milk.