FOOD 2151 Dairy Processing - Raw Milk Quality Tests

Summary

In this video, Ken walks viewers through the raw milk quality receiving process, focusing on tests like aroma, pH, and titratable acidity (TA) to ensure milk quality before further processing. He demonstrates how to check the temperature, perform aroma testing, and use pH meters and titration techniques to assess the milk’s acidity. These tests are critical for determining the milk's quality, shelf life, and bacterial levels, guiding decision-making at dairy facilities. The video also touches on the importance of following internal specifications and notifying supervisors if deviations are found.

Takeaways

• 😀 Ensure raw milk temperature is checked upon arrival; it should be below 4°C for proper quality control.
• 😀 Aroma test is performed to assess the quality of the raw milk. This is done by warming the milk to about 22°C and comparing samples.
• 😀 A pH test is conducted using a calibrated pH meter. The expected pH range for raw milk is between 6.5 and 6.7.
• 😀 Titratable Acidity (TA) is measured to determine the acidity level in the milk, indicating potential bacterial growth.
• 😀 pH measures acidity directly, while TA helps determine the total acidity in the milk, which is linked to bacterial activity.
• 😀 Calibration of the pH meter is crucial, and it should be done at least once per day, preferably twice per shift.
• 😀 If the raw milk temperature exceeds 4°C, it must be resampled and the supervisor must be notified about the deviation.
• 😀 Milk with lower pH values (more acidic) may indicate higher bacterial activity, while higher TA values suggest more bacterial growth.
• 😀 Proper electrode maintenance and storage are essential for the longevity and accuracy of the pH meter.
• 😀 All quality tests (temperature, aroma, pH, TA) must be logged, and deviations from internal specifications should be reported to the supervisor.
• 😀 Antibiotic testing is crucial for raw milk, as any positive results will lead to the rejection of the milk batch for processing.

Q & A

Why is it important to check the temperature of milk when it is received?

The temperature of milk needs to be checked to ensure it is within the proper range (less than 4°C). This is crucial because higher temperatures may indicate the milk was abused during transport, leading to bacterial growth and spoilage, which can affect its quality and shelf-life.

What is the role of aroma testing in raw milk quality assessment?

Aroma testing is used to detect any off smells in the milk, which could indicate spoilage or contamination. By warming the milk to around 22°C, lab personnel can more effectively evaluate the milk's aroma and spot differences between fresh and potentially compromised samples.

How do pH levels help in determining milk quality?

pH levels are used as an indicator of milk's acidity, which correlates with bacterial activity. A lower pH signifies more acid in the milk, typically resulting from bacterial fermentation, and may point to a higher bacterial count in the milk, impacting its quality.

What is titratable acidity (TA) and how is it measured?

Titratable acidity measures the total acid content in the milk, which is often an indicator of bacterial activity. It is measured by adding a standardized solution of sodium hydroxide (NaOH) to the milk and determining the amount required to reach a specific pH, indicating the acidity level.

What should be done if the milk temperature exceeds 4°C when received?

If the milk temperature exceeds 4°C, the sample should be rechecked. If the temperature remains high, it is necessary to notify a supervisor to determine further action, as this could indicate the milk is not in optimal condition for processing.

How do pH and titratable acidity (TA) relate to bacterial presence in milk?

Both pH and TA are measures of acidity in milk. A low pH indicates more acidity, which is often associated with higher bacterial activity. Conversely, a higher TA value indicates a higher total acidity, pointing to more bacteria present in the milk due to fermentation of lactose.

Why is it important to calibrate the pH meter regularly?

Regular calibration ensures the pH meter provides accurate readings. It is essential for maintaining precision when measuring milk’s pH. Calibration is done using standard buffer solutions (pH 2, 4, 7, and 10) to adjust the meter for consistent performance.

What is the significance of using distilled water when testing pH in milk?

Distilled water is used to rinse the pH probe between samples to avoid contamination. It ensures that the probe remains clean and provides accurate readings without interference from previous samples.

What does a positive antibiotic test result mean for the milk?

A positive antibiotic test indicates that antibiotics are present in the milk, which is a serious concern as it could affect milk processing and consumer safety. In this case, the milk would be rejected, and the load would not be processed.

What factors might influence the pH and TA values of milk?

Factors like the breed of the cow, the time of year, and the handling of the milk (including temperature abuse or bacterial contamination) can influence pH and TA values. Variations in these values can provide insights into the milk's freshness and bacterial load.