What causes off-flavour contamination?

Microorganisms called actinomycetes can grow on stored peanuts. These actinomycetes produce volatile compounds that contaminate the stored nuts, and cause the musty, earthy off-flavours.

Key points

• Off-flavour contamination in North Queensland peanuts can cause major product downgrades, resulting in large financial costs for growers and processors.
• Off-flavour is caused by odorous (volatile) compounds that can diffuse into, and contaminate, clean peanuts, particularly while peanuts are in storage.
• Microorganisms called actinomycetes that grow on peanuts and other organic material in crop windrows can produce these volatile compounds.
• Actinomycetes are present everywhere in the environment but only produce off-flavour compounds under certain conditions such as high temperature or high relative humidity.
• Growth of these microorganisms after digging of the crop can be reduced by making sure peanuts are rapidly dried to safe pod-moisture content after harvest.
• Post-harvest, peanuts should be stored in clean and secure on-farm storage bins to prevent growth of microorganisms, and delivered to the buying point as quickly as possible.
• Rapid and low-cost analytical techniques to detect off-flavour compounds are being developed to help manage this problem.