MANUFACTURE OF ICE-CREAM 273 



(3) Skimmed milk is boiled, either with or witliout the addition of some form 

 of starch (generally corn flour) with a certain number of eggs, sugar and flavouring. 

 Practically, the number of eggs used varies inversely with the amount of starch, the 

 effect of both being to thicken the mixture, and in some cases the practice has been 

 to at once freeze the mixture ; in others, in order to economise the consumption of 

 ice, the heated liquid has been allowed to cool naturally. Usually the number of 

 eggs is three or four to the quart. The whole is again boiled (for perhaps 

 twenty minutes), after which it is set aside to cool until the following morning, 

 when it is placed in the "freezers" and frozen. In short, the mixture contains 

 no cream, and is, in fact, a frozen custard. The mUk and eggs are generally 

 obtained locally, and are usually of good quality. It is stated that if such 

 were not the case the ice-cream would be unpalatable, owing to ill-flavour, 

 and therefore unsaleable. The eggs used to be blown, but of late years 

 that practice has fallen into disuse, and they are now broken and mixed in the 

 ordinary way. The boiling is carried out in various utensils over the open fire. The 

 mixture stands for coohng purposes in the living room, or in any out-of-the-way 

 corner, sometimes in the open yard or area. The freezing takes place early on the 

 following morning in the " freezers." A " freezer " consists of a tin or galvanised iron 

 cylinder, or container, in which the mixture is placed. The cyhnder fits into an 

 outer vessel of wood or metal so loosely as to leave an inch or two of space all 

 round. In this space is placed broken ice and salt, and the inner cylinder is rotated 

 from time to time in this ice medium. No ice is added directly or indirectly to the 

 mixture itself, nor are colouring agents used as a rule. The utensils and materials 

 appear, as a general rule, to be clean. 



From this description, which applies, generally speaking, to the street ice-cream 

 industry in London, it will be seen that the "ice-cream " is boiled for some time, and 

 in all probability sterilised, and in due course it undergoes, at least approximate, 

 freezing. These facts, added to the generally wholesome condition of the elementary 

 materials used, would appear, at first sight, to place the substance beyond risk of 

 contamination. But the critical period is the time of exposure between boiling and 

 freezing. Boiling sterilises, but freezing does not sterilise. Hence, if in the long 

 cooling process the substance is exposed to contaminated surroundings, the result 

 may be, in effect, a contaminated ice-cream. Such, in fact, frequently occurs.* 

 Hence it would appear that it is not the process of manufacture that needs super- 

 vision so much as the general condition of the houses in which the substance is 

 made, and of the persons who make it, and the manufacture so far as length of time 

 between boihng and freezing is concerned. 



The important stage of the operation is, therefore, that between the boiling and 

 freezing. Attention has been drawn to the fact that the majority of the specific 

 pathogenic bacilli discovered in ice-cream are of a non-sporing variety, and that, 

 therefore, if originally present in the material, would have been destroyed by boU- 

 ing, and, if found subsequently, must have gained access to the material whUe 

 cooling. The subsequent freezing, while it might inhibit such bacilli, would 

 certainly not destroy them, and on ingestion and melting their growth and develop- 

 ment would again commence. 



Some dozen outbreaks of disease have been attributed to the 

 consumption of ice-creams. A typhoid epidemic occurred in 

 Liverpool (27 cases) in 1897 due to ice-cream, and an earlier epidemic 

 of the same disease traceable to the same cause occurred at Deptford 

 in 1891 (Turner). Eecently, a small outbreak occurred in the city 

 of London affecting 16 telegraph boys. The symptoms were colic 

 and diffuse abdominal pains, headache, vomiting, diarrhoea, and 

 nervous depression. Dr CoUingridge's inquiry resulted in the 

 following conclusions : — 



* See investigations by Klein, Cook, Wilkinson, Foulerton, and others. 



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