Because of conflicting statements in the literature, experiments have been camed out in which spores of moulds commonly associated with mouldy bread have been incorporated in bread doughs before baking. It has been demonstrated that such moulds and the ascospores of Neurospma tetrasperma are killed well before the end of the baking period. This evidence supports the contention that in normal bakery practice moulds do not survive baking and that mould growth on bread is due t o post-baking contamination with mould spores. IntroductionThe wastage of bread due to the development of mould costs the baking industry a large s u m of money each year, one estimate' being that the equivalent of about five million IQ-lb. loaves are spoiled in this way per annum. This mould problem, which occurs mainly in the summer months, is most serious in the case of sliced, wrapped bread where conditions for the development of mould spores are rather more favourable than with unwrapped loaves.At the present time, mould inhibitors are not permitted as bread additives in this country (but see reference 2), although the use of such inhibitors would result in a significant reduction in the wastage of bread due to mould growth. Nevertheless, it is important to remember that anti-mould agents normally delay rather than prevent the development of mould' and that, while bread spoilage will be reduced if mould inhibitors are permitted as additives, mould is likely to remain a problem in the baking industry.It is generally considered that post-baking contamination of bread by mould spores is the origin of the moulds that subsequently develop on the bread. While the mouH spore population of air is variable and is affected by such factors as the time of year and the location,s and by the conditions in the bakery, it is clear that, unless stringent precautions are taken, post-baking contamination of bread by air-borne mould spores will be significant. For example, it has been estimated that some 7000-8000 mould spores per sq. m. of surface may settle from the bakery atmosphere in an hour.' Under normal circumstances, therefore, mould will develop on bread if the storage conditions are suitable.Despite the inevitable danger of post-baking contamination, it is important to establish whether mould spores present in the dough ingredients wiU survive the baking process. Flour always contains mould spores which are mainly derived from the wheat from which it has been milled, although contamination can occur during the milling p r o c e~s .~ A number of workers have measured the mould spore population of flour and have obtained results varying within wide limits. Mould spore counts obtained in these laboratories in recent years have ranged from 500 to 70,000 per g. (average goo0 per g.) and these results are considered to be typical.The conditions prevailing when bread is baked are such that, from these considerations alone, it is extremely unlikely that mould spores in the dough would survive the baking process. Bread is usually baked at oven temperature...

In flour suspensions a substantial proportion of malt a-amylase is adsorbed from solution by the damaged starch in flour whereas much smaller proportions of fungal amylase are adsorbed under similar conditions. The greater adsorption of malt a-amylase by damaged starch is mainly responsible for the enhanced effect of malt in the maltose test. Only about 60-70% of malt a-amylase appears to be capable of being adsorbed by flour, and this suggests that the enzyme contains at least two components differing in their adsorption characteristics.

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As the methods normally used in the examination of flour do not reveal the presence of fungal amylases, a technique has been developed which may be employed for their detection and semiquantitative estimation. 'This based on the decrease in cc-amylase activity which occurs when a flour extract contai g calcium ions is heated at 68" for 30 min. Confirmation of the presence of fungal am 'e and of t h e amount which has been added to flour can be obtained by using the rehtionship between cereal r-amylase activity and Hagberg number.

High lipase activity in flour, which may result from mould contamination of wheat, has been shown to be a cause of the development of a soapy taste in biscuits made from the flour. Three methods may be used to assess whether, as a result of high lipase activity, a flour is likely to give biscuits with such a taint. These methods involve (1) organoleptic tests on a flour‐fat dough incubated at 80° F, (2) measurement of the acidity of the fat extracted from such a dough and (3) determination of the counts of moulds and fat‐splitting organisms in the flour.