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Full text of "Information sheet on brine peeling of various root vegetables"

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Historic, archived document 

Do not assume content reflects current 
scientific knowledge, policies, or practices. 


April, 1943 



Western Regional Research Laboratory, Albany, EagJ-f^jQ-aR A^^ 
Bureau of Agricultural and Industrial ChAi^jffijfcNT SERIAL RECORD 
Agricultural. Research Administration! m/io 
IS. S/< tment of Agriculture | 

This information sheet is a brief preliminary report on a' method whe reby 
operators of vegetable processing plants can peel potatoefej ruta bagas, and 
possibly other root vegetables by scalding them in a hot saturated salt 
solution and then removing the peel in a suitable washer. The brine solution 
can be brought to a temperature higher than that of boiling water — that is, 
to 228° F. under sea level conditions, or 16 degrees above the boiling 
temperature of water. Brief immersi< . in the high-temperature brine bath 
softens the cells adjacent to the skin, thus loosening it from the vegetable. 
Since the method has certain advantages in comparison with other methods, 
it has been given experimental trial at the Western Regional Research Laboratory, 

Pro cedure 

A saturated brine solution is prepared by adding common salt (NaCl) to water 
in the ratio of approximately 3 .'i pounds of salt par gallon of water. The 
weight of one gallon of the solution is about 9.6 pounds. This solution is 
brought to boiling temperature and the washed vegetables are held below the 
surface of the boiling brine ition for varying periods of time. This 
interval must be determined by trial for each vegetable and also for various 
lots of the same vegetable if th© quality varies. Excessive scalding will 
result in high peeling losses, whereas too short a treatment will leave much 
peel to be removed by hand, ! the vegetables have been properly scalded, 

the skins remain intact. These skins can then be removed by washing in a 
suitable washer equipped wit) oderately high-pressure spray (approximately 
125 pounds per square inch) 

The scalding procedure can be carried out either as a batch or as a continuous 
process. The latter method is preferable, however, and may be accomplished 
through the use of a specially designed draper-type brine peeler described 
below. A standard draper- type lye peeler can be used as a brine peeler pro- 
vided it incorporates means for holding the vegetables below the surface while 
they are being conveyed through the bath, and provided the materials of con- 
struction of the machine are not affected by the concentrated salt-water 
solution. It should be pointed out that all vegetables float in a concentrated 
brine solution. 


The U. S. Department of A£g has prepared two brine peeler designs for 

use with either gas or oil as a fuel. Steam is used for rapid initial 
heating during "start-up" periods. These units can be modified for use with 
indirect steam heating. The designs are shown on USDA Drawings Nos. D-109 
and D-lll, and are designated as designs No<. 1 and No. 2 respectively. The 

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first design shows the construction details of a unit capable of processing 
approximately 8 to 10 tons of potatoes per hour, with a 6-minute retention 
^period in boiling concentrated brine. The capacity will vary with other vege- 
tables in accordance with time of retention. Similarly the second drawing shows 
the construction details of a unit capable of processing approximately 2 to 3 
tons of potatoes per hour, with the same retention period. These designs may 
be obtained on request from the. Western Regional Research Laboratory, Albany, 

The USDA peelers operate as follows: The vegetables are held below the surface 
of the brine by means of a wire belt fitted with vertical advancing flights. 
As "the product nears the discharge end of the tank, it is picked up by a draper 
belt* The excess salt is washed from the surface of the product by a light 
water spray which serves also as a make-up water supply to replace water lost 
through evaporation, etc. From the draper belt the product is discharged 
directly into the washer where the peeling is removed. 

Discussion and Comparison with Other Metho ds 

Some of the advantages of the brine method as compared with lye peeling are as 
follows: The salt with which brine is made costs approximately one-fifth as 
much as caustic soda per pound or about three-fifths as much per charge., Salt 
can be handled without personal hazard, whereas caustic soda say cause burns . 
Both salt and caustic soda are lost by adherence to the surface of the vege- 
table, but lye in addition gradually loses its strength by chemical reaction 
and consequently must be renewed more frequently than the salt Carry-over of 
salt on the vegetable is not detrimental, whereas even a trace of lye left 
after washing is highly undesirable. Lye may cause discoloration of the surface 
of the product and if the treatment is too drastic will ruin itc 

Excessive retention periods with either method will soften the surface too deeply 
and result in excessive peeling loss. The effect of high altitudes on reducing 
the boiling temperature of the liquid may prevent successful use of brine peeling 
in some localities. The normal peeling loss with brine peeling ranges between 
12 and 15 percent on potatoes, and the over-all loss, including paring and 
peeling, will range from 13 to 18 percent. 

Brine peeling has not undergone a full-scale commercial test as yet. Experi- 
mental trial runs are recommended for plants that are handling potatoes, 
rutabagas, sweetpotatoes, or carrots. 

Numerous other high-boiling liquids have been studied in addition to brine. 
Mineral oil is the only other fluid that has given satisfactory results, but 
further study must be made before it can be recommended. 

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