168 Till- PRKSKUYATION OF MKAT, KTC. 



the rest are checked by the plasmolytic influence of the high sugar-content. 

 The putrefactive bacteria also suffer through the action of the free acid present. 

 Sundry vegetables, especially those employed for Julienne soup, are preserved 

 by drying, for which purpose they are cut into small pieces, and exposed in 

 special ovens to a hot air temperature of 5o-6o C. Not infrequently they are 

 then, in accordance with a proposal made by Masson, subjected to hydraulic 

 pressure, compressed vegetables being thereby produced. 



Drying is a comparatively inexpensive operation, but cannot be resorted to 

 in every case, since many kinds of fruit and vegetables have their fine flavour 

 too much impaired thereby. Such articles are treated by the Appert process. 

 Green peas, cauliflower, asparagus, beans, and suchlike are manipulated as 

 follows : After being carefully cleaned, they are placed in glass jars or in tins, 

 which are then filled with water and set in a salt bath, the temperature of which 

 is maintained at below ioo' C. for one or two hours, and thereafter raised to 

 boiling point (108 C.), at which it must be allowed to remain for some time, in 

 order to definitely destroy all the hardy spores of the hay and potato bacilli. 

 The temperature is then allowed to sink to 60 C., whereupon the small blow- 

 hole in the otherwise closed tin is sealed up by means of a drop of solder, glass 

 jars being closed air-tight by other suitable means. Preserves carefully pre- 

 pared in this manner are sterile in the strictest sense of the term ; but if perfect 

 sterility is, by reason of any oversight, not attained, the still-living germs sub- 

 sequently increase at a great rate. Their development is mostly attended with 

 the evolution of gas, in consequence of which the straight walls of the tin are 

 bulged outwards, and frequently even burst, 



A drawback accompanying Appert's process is that the colour of the 

 vegetables so treated is generally destroyed. If the preservation of the colour 

 be desired, as is the case, e.g., with red beet, gherkins, and the like, then other 

 means must be resorted to, and the antiseptic properties of the acids be utilised. 

 The samples in question are boiled in vinegar, the liquor being then poured off 

 and replaced by fresh unimpaired vinegar. In this way mixed pickles, for 

 instance, are prepared. In many cases the boiling is omitted, pickled gherkins, 

 for example, being preserved by simple immersion in cold vinegar. 



That no protection against the development of bacteria is afforded by 

 steeping in brine needs no further argument. As a matter of fact, an easily 

 observable decomposition occurs in the so-called salted gherkins prepared in this 

 way, the phenomenon proving to be lactic fermentation ; and it is to the acid 

 thereby produced, and not to the small proportion of common salt present, that 

 the retardation of decomposition is due. 



The boiling of fruits and fruit-juices is an operation too well known to need 

 detailed description here. The added sugar employed herein restricts decom- 

 position by strongly plasmolysing and preventing the development of such germs 

 as are not destroyed by the boiling. In many cases, this action is assisted 

 by the addition of a certain quantity of whortleberries. A few particulars 

 raspaciing the high percentage of the strongly antiseptic benzoic acid present in 

 the latter have already been given in an earlier chapter ( 80). The glass jars 

 destined to contain the finished jam, marmalade, etc., are sulphured previous to 

 use. The preservation of fruit is greatly facilitated by a careful preliminary 

 cleaning, a preciution that should, moreover, not be omitted when the fruit is to 

 be eaten raw, since the usually sticky surface tenaciously retains the dust and 

 accompanying germs that are blown on to it. Thus, M. T. SCHNIRER (I.) 

 discovered virulent tubercle bicilli on the surface of grapes sold in the Vienna 

 market. 



A word must be adde.l with regard to the gelatinisation of fruit juice. As 

 is well known, the cells of mvny fruits are rich in pectin, which, when the cells 



