Molasses – Foaming

Molasses – Foaming

Normally, stored molasses seldom shows any unusual behaviour, however like all such extracts from plant-based production, it can deteriorate over time, and at elevated temperatures resulting in a loss of sugars.

This results in fermentation, shown as a ‘gassing’ reaction, producing volumes of CO2 and Ethyl Alcohol. Mostly CO2.

The ‘gassing’ reaction consists in small bubbles in the molasses which are retained in the bulk liquid for some time and which  manifests itself in frothing, and an increase in volume of the molasses which may overflow a cargo tank in extreme circumstances.

The visual effect of ‘gassing’ onboard a ship, would be an increase in volume, and foam formation, especially on top of the liquid molasses.

As this decomposition accelerates, a rise in temperature may be experienced, together with a change in colour and smell of the molasses.

Extreme decomposition may result in an explosive type of decomposition, and then actual explosions.

However, with the advent of an effective mill sanitation program and anti-foaming agents, this is largely a thing of the past and would now be an extremely rare occurrence.

Nobody really understands how, and why, the reaction occurs, one theory known as the ‘MAILLARD Reaction’ is based on a reaction between amino acids and reducing sugars.

Once started, nothing can stop the Ethyl Alcohol production, however the source of the fermentation can be eliminated by blowing air into cargo.

By blowing air, the fermentation stops, the temperature slowly drops, the volume decreases and the foam is absorbed back into the liquid.


Lower weighted air-hoses into the liquid molasses, ensuring the hose is well into the liquid itself , not the foam layer.

The air does not need to be at a high pressure, a constant air-stream at a pressure of 1-3 bar is all that is needed.

Do not expect to see an immediate reaction, blowing should be continued over a period of hours, where the froth slowly becomes absorbed back into the liquid.

Continue blowing, changing the position of the hoses as necessary, until the froth is at a manageable level, so that sweeping is possible (if intended) or the discharge can be satisfactorily completed.


The enclosed paper ‘Deterioration of Molasses during Storage: Possible Cause and Means to Prevent it’, explains the precis above in more detail.

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