APPLE CIDER 23 



pressure head of six to eight feet is used, but with more pressure head the filter 

 may be run longer without cleaning. To clean the filter, the tube is untied and 

 the filter aid and sediment shaken out or washed out under running water, 

 after which the tube may be returned to the filter 



Filter Presses and Plate Filters 



For large installations filter presses are preferred for the production of clear 

 ciders. A list of manufacturers of equipment is given in the appendix. In 

 general, each manufacturer can best give directions for use of his particular type 

 of press and can define its limitations. 



Freshly pressed apple cider cannot be economically filtered in a filter press 

 without the use of a filter aid such as asbestos or diatomaceous earth. The 

 colloidal matter present clogs the filters and makes them useless. However, 

 after treatment with a filter aid or with Pectinol or gelatin-tannin, the filter 

 presses are very satisfactory and give a brilliantly clear product. Accessory 

 equipment such as storage tanks, pumps, and sanitary metal tubing is required 

 when filter presses are used. 



The so-called germ-proof filters used for sterilizing cider can be utilized only 

 after the cider has been already clarified and pre-filtered. 



PERSERVATION OF CIDER 



Preservation methods have as their object the elimination or control of unde- 

 sirable microorganisms. In sweet cider, the esential organisms which must be 

 controlled are yeasts and molds: yeasts, because they ferment the sugars in 

 the cider to alcohol; molds, because they present an unattractive appearance 

 in the cider and also slowly use up the sugar and impart off-flavors to the prod- 

 uct. Molds require much more air to carry on their activities than do yeasts, 

 but yeasts are killed more easily by heat treatment and grow less readily at low 

 temperatures than do molds. These points are mentioned because they are 

 important considerations in the preservation of cider. 



Preservation methods may be put into four general groups: 



1. Germ-proof filtration. 



2. Freezing. 



3. Pasteurization. 



4. Treatment with preservatives 



Germ-proof Filtration 



In this method, cider after a pre-filtration treatment is run through a filter 

 with openings so small that while the cider can pass through the filter, yeasts 

 and molds are prevented from doing so. After going through the filter the 

 cider is run into sterile bottles; capped with sterile caps, and stored for two 

 weeks or so to be sure fermentation will not take place. It is then ready for 

 distribution. The advantage of the germ-proof filter method is that no heat 

 is required, thus preventing any "cooked" flavor in the cider. 



Disadvantages of the germ-proof filter are: (1) Care is required to assure 

 sterility in the bottled juice. (2) The equipment is too expensive for the small 

 manufacturer. (3) Such fine filtration removes much of the color and "body" 

 from the cider. 



