Mould deterioration of feeding-stuffs in relation to humidity of storage: Part I. The growth of moulds at low humidities

The literature relating to the growth of moulds at different humidities is surveyed.
Observations were made on the development of mould growth on six widely different types of feeding-stuffs for storage periods extending over some 3 1/2 years. The main factors controlling mould growth were found to be:
1. The relative humidity rather than the moisture content of the food.
2. The length of the storage period. Mould growth took place relatively quickly on all feeding-stuffs stored at 100-75% R-H. Below 75% R.H. mould growth, while not prevented, only developed after a very prolonged latent period. Mould development was observed on locust beans exposed to a humidity as low as 65 % after a latent period of over 2 years.
3. The balance and type of nutrients provided by the various feeding-stuffs was shown to influence the latent period as well as the extent of mould deterioration. This was confirmed by experiments on artificially dried grass fractions and by experiments on starch, protein and fibre mixtures.
4. The temperature of storage was found to affect the rate of mould development; mould growth developed sooner on samples stored at 22C. than at 15.5C.
5. The type of mould species present. At high humidities all mould species grew rapidly: at low humidities, only a few types were capable of growth.