PROGRESS IN THE DEHYDRATION INDUSTRY. © 
demand. The first step, therefore, in creating a domestic market for 
dehydrated products was the improvement of the products. While 
perfection has by no means been reached, the improvement in quality 
during the past year has been remarkable. 
How has this improvement in quality been accomplished? It has 
not. been accomplished by any extensive changes in the drying equip- 
ment of these plants. Excellent drying equipment, we find, does not — 
necessarily produce excellent dehydrated products. The products 
produced this season have, as a rule, been more palatable, have had a 
more appetizing appearance, and have better keeping qualities. While 
many manufacturers have in the past been able to produce palatable 
dehydrated vegetables of good appearance, the products generally would 
not hold up in storage at ordinary temperatures, even in sealed tins. 
Two types of spoilage have been common in dehydrated vegetables. 
The hardest type to control is the infestation by moths and other insects. 
The other type of spoilage is due to chemical changes which are not 
associated with bacteria and moulds, but are probably due to the action 
of oxidases or enzymes. The Division of Dehydration has con- 
ducted investigations as to the action of moulds and_ bacteria 
on dehydrated products. All of the data secured to date 
indicate that dehydrated products will not be subject to spoilage 
through the action of moulds and bacteria when stored under reasonable 
conditions. Moulds appear to require a moisture content of at least 
24 per cent. for their development, and the average moisture content of 
dehydrated vegetables is well under 15 per cent. Bacteria in dehydrated 
vegetables decrease in number in storage. 
This deterioration in dehydrated vegetables, due to chemical changes, 
is manifested differentlyein different vegetables. In the case of cabbages 
and onions, the dried product becomes brown in colour and loses its 
characteristic flavour. In the case of carrots, the red colour disappears, 
at times associated with the darkening of colour and loss of flavour. 
Our observations indicate that in most cases these changes are due to 
the action of enzymes or oxidases. Neither the type of dryer nor the 
system of drying appears to be a factor. ‘Several factors tend to control 
these changes, which further lead us to believe they are due to the action 
of enzymes or oxidases. 
Investigations have shown that the moisture content of the product 
is a factor which controls the rate at which these destructive changes 
take place—the lower the moisture content the slower the rate of 
deterioration. At ordinary room temperatures, vegetable products, 
with a moisture content above 1 per cent., deteriorate quite rapidly 
—in four to six weeks—while the same products, with moisture con- 
tents of 3 to 5 per cent., show no changes until after four to six months 
of storage. Improvement of the keeping qualities by drying to a very 
low moisture content is not commercially practicable, however, for two 
reasons: First, the removal of this extra moisture means a longer 
drying périod, a higher cost of drying, and especially a greater danger 
of scorching; second, after: drying the product to this low moisture’ 
content, it is necessary to pack it in moisture-proof containers in order 
to avoid absorption of moisture from the atmosphere. ‘The average 
commercial moisture content of dehydrated vegetables is approximately’ 
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