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

Abstract

With Plate 6 and 6 Text-figures)The literature relating to the growth of moulds at different humidities is surveyed.Observations were made on the development of mould growh on six widely different types of feeding-stuffs for storage periods extending over some 31 years. The main factors controlling mould growth were found to be : I . Thc relative humidity rather than the moisture content of the food. 2. The length of the rtoruge peziod. Mould growth took place relatively quickly on all feedhg-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 "/o after a latent period of over z years.3. The b a k e and type of nutrients provided by the various feeding-stuffs mas 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 tempnaiure of rtoruge was found to affect the rate of mould development; mould growth developed sooner on samples stored a t zz°C. than at 15.5'C.5. The type o j mould rpecier present. At high humidities all mould species grew rapidly: at low humidities, only a few types were capable of growth.

The self-heating of wet wool

“…However, when the same sample (without removal from the apparatus) was conditioned to equilibrium with an atmosphere of 81 % RH, it heated to 46.7°e. These differences in the rate of heat generation between equilibrium atmospheres of 76% and 81 % demonstrate the narrow variation in moisture content that is sufficient to control heating, and are in accordance with published descriptions of fungal metabolism (Galloway 1935;Snow et' at. 1944).…”

The Germination of Mould Spores at Controlled Humidities

“…The factors influencing the growth of moulds on various stored products have been described by several authors. These include observations on book-binding materials by Groom & Panisset (1933), on textiles by Galloway (1935), on leather by Colin-Russ (1940), on dried meat by Macara (1943), and on feeding stuffs by Snow, Crichton & Wright (1944). It has been shown that the development of moulds on various materials is conditioned by the relative humidity of the storage atmosphere rather than by the moisture content of the materials themselves.…”

The bacteriology of dehydrated vegetables

“…Snow, Crichton & Wright (1944) found that moulds developed fairly rapidly on animal feeding-stuffs stored at 100 to 75 % R.H. At humidities below 75 % R.H. mould growth was not entirely prevented but took place after a very long latent period. Growth was not found to take place below 65% R.H. Gane (1943) gives figures for the water relations of air-dried scalded vegetables.…”

“…Little work has been carried out on the incidence of mould growth on vegetables at different humidities, but Wright (1940) found that samples of artificially dried grass stored at 70 % R.H. showed no signs of moulding for almost a year, after which slight growth took place. Snow, Crichton & Wright (1944) found that moulds developed fairly rapidly on animal feeding-stuffs stored at 100 to 75 % R.H. At humidities below 75 % R.H. mould growth was not entirely prevented but took place after a very long latent period.…”