In order to protect the color it is best to water cool No. 10 cans of pulp after processing. Pulp in cans of any size should not be stacked solid while it is still hot. The metal of the can has a bleaching action on the pulp and this is greatly increased if the pulp is stacked hot or stored in a hot warehouse. If stacked while excessively hot, stack-burning may occur with consequent darkening of the pulp.
As indicated above, there is a considerable difference of opinion among successful manufacturers of pulp regarding the details of manufacture necessary to secure the best results. It is probable that different conditions call for different methods of operation. At any rate, all successful manufacturers are agreed that the color of the pulp is an important index to its quality and greatly influences its commercial value. The flavor of pulp is also an important criterion and is considered by many buyers in forming an estimate of the value of pulp. A scorched taste or a flat flavor show that the manufacture of the pulp was not adequately controlled and impairs the commercial value of the product.
Color and flavor commonly go together. The same manufacturing methods which yield a product of high color are likely to give a product of superior flavor.
DISCARDING TOMATO JUICE
It was formerly customary, and is still the practice of some manufacturers of tomato pulp, to discard a portion of the juice of the tomatoes. Some manufacturers, especially in the preparation of pulp from tomato trimmings, allow the trimmings to pass over a colander and thus separate the free juice, which is discarded. Others allow the product of the cyclone to stand for a time in tanks and then discard the clear juice which settles in the bottom of the tanks. Both practices are wasteful and have generally been discontinued. Some still adhere to one or both, however, and it was thought best to make the matter the subject of study.
Some discard the juice because of the belief that it consists of nothing but water and is valueless. Some are of the impression that the juice separated from the trimming stock before straining takes on a brown color during evaporation which would interfere with the red color desired in the finished product, if allowed to go into the pulp. Some recognize the value of the juice, but believe that the expense of its evaporation would not be warranted by the increased quantity of pulp. Some have not measured the juice discarded and greatly underestimate its volume.
With the view of determining the approximate value of the material discarded in this manner, a batch of material, fresh from the cyclone, was divided into two portions, one of which was immediately concentrated to form a pulp, and the other was allowed to stand about 20 minutes when a clear liquor had separated at the bottom. This clear liquor was then removed and the remainder evaporated until the desired consistency was obtained.
Samples of the finished pulps, of the raw product from which each was prepared and of the clear liquor, separated from the second one, were preserved by sealing in cans and processing. These samples were numbered as follows:
- 702—Product from the trough under the second cyclone, or finisher.
- 703—Clear liquor, which separated at the bottom of the tank, after a portion of 702 was allowed to stand. This formed about one-fourth of the entire product of the tank.
- 704—Drained residue from 703.
- 705—Finished pulp obtained by concentrating 704.
- 706—Finished pulp obtained by concentrating 702.
These samples were examined with the results given below.