Microbially generated spoilage odours during grain storage: factors affecting their formation

Spoilage of grain by micro-organisms can cost the industry significant amounts of money from loss of raw material, down time, and effort involved in clean-up and further prevention. Grain spoilage gives rise to off-odours – in particular musty, sour, ‘green’ and fishy odours –which result mostly from fungal activity when the grain is stored under conditions of high moisture and temperature. However, they are difficult to detect using human senses, due to background odours for example on the farm and in the store. By the time they are detectable, spoilage is already likely to be widespread.

Although a lot is known about how spoilage arises, and the storage conditions required to prevent it, such conditions cannot always be achieved. Therefore the availability of systems for early detection of spoilage odours can facilitate targeted intervention. This literature review pulls together a wealth of information on spoilage odours – including their nature, formation and the kinds of conditions under which they are likely to arise – as a prelude to the development of a sensor system for early detection of spoilage problems. It is likely to be of interest to anyone for whom understanding the background to grain spoilage is important.

Contents:

• Introduction
• Grain storage
  - Safe storage conditions
  - Preservation of quality
  - Odours associated with grain
• Micro-organisms on grain and factors inducing them to grow and produce spoilage odours
  - Introduction
  - Microflora of grain
  - Conditions that promote damage to grain by storage fungi
  - Formation of mycotoxins from fungi
  - Physiological factors affecting mycotoxin production
• Volatiles associated with grain and spoilage odours
  - Volatiles associated with cereal grains
  - Odours produced by micro-organisms on cereal grains
  - Detection of microbial spoilage
• References