Understanding Senses Downgrades

Summary:

Here you’ll find common milk smell and flavour issues, what causes them, and simple ways to identify and prevent them on farm.

A senses test, or organoleptic assessment, measures the smell and look of raw milk. It involves visually checking the milk for free fat, coagulation, or colour from blood or colostrum and smelling for odours such as feed taints or bacterial action (sourness).

Downgrade support

At MilkTestNZ, one person will screen the samples and set any aside that are suspect. To confirm, a team of two people will identify and quantify the odour and colour.

There must be consensus between the confirming team before a senses downgrade is issued.

Organise a traceback

If you cannot determine the cause of the test result or you receive downgrades, call the Farm Source Service Centre.

Depending on the duration and severity of the issue, they will organise an on-farm trace back and take you through the Milk Quality Support Programme.

Refund support

Fonterra will refund up to the total amount of the deductions made under Clause 9.5 of the Fonterra Farmers’ Terms of Supply (“Terms of Supply”), in the current season, to cover the cost of help from a Fonterra approved service provider to solve milk quality problem.

Please refer the Terms of Supply Clause 9.7 for more information.

What to look for on-farm:

  • Crop feed or weeds that cause sour, rancid or chemical smells
  • Blood or colostrum that changes the colour or smell
  • Foreign matter or dirt from poor filtration
  • Poor temperature or silo management enabling excessive bacterial growths

How to prevent senses downgrades

Early intervention is the best tool you have for preventing downgrades.
  • Ensure good grazing management by feeding crops after milking to avoid strong-smelling crops affecting milk 
  • Control weed growth in pasture and supplements 
  • Maintain good pre-cooling and refrigeration
  • Maintain good cow condition 
  • Check your milking management practices to avoid blood, colostrum and foreign matter getting into milk

Prevention by odour type

Feedy – onions and/or fruity 

  • Avoid feeding strong-smelling feeds before milking (e.g. turnips, onions, cabbage) 
  • Be aware feed can affect milk for up to 5 hours 
  • Watch for sudden feed changes, especially in spring  

Cheesy  

  • Avoid excessive agitation or churning during milking 
  • Keep milk temperature stable 
  • Check plant handling if strong cheesy or sour odour appears  

Sour or rotten, acidic  

  • Cool milk correctly and avoid freezing 
  • Ensure milk is agitated properly 
  • Check chiller is on and working 
  • Avoid leaving milk sitting too long  

Cow  

  • Keep shed and cows clean to reduce odours 
  • Watch cow health (e.g. ketosis) 
  • Check feed quality for odour issues  

Fishy  

  • Check for oxidation from bacteria or equipment 
  • Review feed quality as a possible cause 
  • Investigate thoroughly as cause can vary  

Chemical  

  • Rinse plant well to remove cleaner residue 
  • Check cleaning process is correct  

Oxidised  

  • Avoid exposing milk to sunlight 
  • Reduce air exposure during handling  

Stale  

  • Avoid holding milk in the vat too long 
  • Watch for stale milk during dry-off period  

Buttery  

  • Check for bacterial activity causing flavour 
  • Review cleaning and storage conditions  

Musty  

  • Check feed for mould or dampness 
  • Avoid feeding musty forage  

Rancid  

  • Treat similar to cheesy issues 
  • Reduce agitation and temperature changes  

Skatole  

  • Watch for strong musk-like odour 
  • Check cow health for possible liver issues  

Cress  

  • Avoid cows eating cress-type plants 
  • Watch for peppery or burnt rubber odours from feed