FOOD 2151 Dairy Processing - Raw Milk Quality Tests

Main ideas / lessons conveyed

• Purpose of raw milk quality receiving tests: When tanker loads of raw milk arrive, the plant performs quick quality checks (e.g., temperature, aroma, pH, titratable acidity) to confirm the milk is suitable for processing and has not been adversely affected (e.g., temperature abuse or spoilage growth).

• Testing approach:

  • Use predefined specifications (plant/internal guidelines) to determine pass/fail.
  • If results are out of specification, follow an escalation process—such as repeat/confirm tests and notify a supervisor/manager.

• What each test indicates:

  • Temperature: Detects cold-chain failure and helps predict spoilage risk.
  • Aroma (organoleptic): Screens for obvious spoilage/quality issues; aroma differences are easier to detect after warming.
  • pH and Titratable Acidity (TA): Both relate to acidity from spoilage/bacteria, but measure it differently:
    • Lower pH → more acidic → likely more bacteria/spoilage
    • Higher TA → more acidity content → likely more bacteria/spoilage

• Antibiotic testing (note):

  • Plants may also run an antibiotics test (Charm test).
  • A positive result leads to rejection, treated as a regulated outcome.

• Documentation/logbook:

  • Record results and deviations in the plant’s logbook.
  • Maintain calibration records.

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Methodology / instructions (detailed step-by-step)

1) Receiving raw milk: temperature check

• When the tanker arrives:

  • Check milk temperature using:
    • Thermometers known to be accurate and certifiable.
    • Proper insertion technique (milk often in a tank; product may be referenced as in a “tanker bag”).
  • Record the temperature in receiving documentation/logbook.

• Specification target:

  • Milk temperature should be < 4°C.

• If out of specification (> 4°C):

  • Take another sample to confirm (verify measurement reliability).
  • If it remains > 4°C:
    • Notify the supervisor/quality/production/plant manager per site chain of command.
    • Record the deviation in the logbook.

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2) Aroma test (organoleptic)

• Rationale: Screen aroma differences to assess incoming milk quality.

• Procedure concept (as demonstrated):

  • Warm the milk to about 22°C (room temperature) so aroma is detectable.
  • Compare aroma between samples (example involved one sample with temperature abuse overnight).

• Documentation:

  • Record aroma observations in provided handouts/logbook.

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3) pH testing (with calibration and electrode care)

• Equipment:

  • A pH meter (device type referenced as “CUE map/cup map”-type; multiple brands exist).

• Critical practices:

  • Know how to use the pH meter properly.
  • Maintain the electrode:
    • Electrode contains fill solution.
    • Keep electrode solutions clean and stored in proper storage solution to prolong life.

• Calibration:

  • Calibrate using standard buffer solutions:
    • pH 2, pH 4, pH 7 (color-coded buffers shown).
  • Frequency:
    • At least once per day, often twice per shift (document in logbook).
  • Calibration approach:
    • Example described as a 2-point calibration using pH 4 and pH 7.

• Performing the measurement (for a sample):

  • Rinse probe with distilled water.
  • Blot dry.
  • Immerse probe into the milk sample.
  • Wait for the reading to stabilize (meter may show “stabilizing” until equilibrium).
  • Record the measured pH value.

• Example result & specification:

  • Example measured pH: 6.64
  • Example spec range mentioned: 6.5 to 6.7
  • If within spec: record as acceptable.

• Important note about standards:

  • pH (and TA) are not government-regulated; they are plant-defined standards/guidelines.

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4) Titratable Acidity (TA) / titratable acidity procedure (titration)

• Reference location:

  • Described as a procedure on page 5.9 (from video handouts).

• Setup & reagents:

  • Use a predetermined milk volume:
    • 9 mL milk (using a calibrated glass pipette).
  • Add approximately equal distilled water (exact volume not critical; milk volume is).
  • Add indicator:
    • Phenolphthalein
  • Prepare burette with standardized sodium hydroxide:
    • 1/10 normal (0.1 N) NaOH.

• Titration steps:

  • Record the starting burette volume.
  • Add NaOH slowly until a permanent light pink color appears (endpoint).
  • Record the end burette volume at endpoint.

• Calculations (as demonstrated conceptually):

  • Determine NaOH volume used:
    • Example: starting 0.1 mL, end 1.8 mL → used 1.7 mL
  • Example conversion shown:
    • 1.7 ÷ 10 = 0.17

• Example specification & interpretation:

  • TA recorded for sample A: 0.17
  • Example acceptable range: 0.14 to 0.17 (plant/internal standard)

• Standards note:

  • TA specification is described as internal (not government regulation).

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5) If test results indicate possible quality issues

• General response:
  • If out of specification:
    • Repeat the test internally to confirm.
    • If still out of spec:
      • Notify a supervisor/manager to investigate and follow deviation procedures.

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6) Antibiotics testing (Charm test) and rejection criterion

• Mentioned as an additional test:

  • Could occur upstream or at receiving.

• Outcome:

  • If antibiotics are detected (positive result / bandbox mentioned):
    • The milk load is rejected.

• Distinction:

  • Antibiotic detection is treated as a regulated issue, unlike pH/TA/temperature/aroma screening.

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Speaker / sources featured

• Speaker: Ken (introduced as “hi my name is Ken”)
• Video source/content type: Training/lecture material referenced as “section five”, with course handouts/pages referenced (e.g., 5-1, 5-2, 5-9, 5-12). No external named authors beyond Ken are cited.