TOMATO PRODUCTS: PULP, KETCHUP, AND CHILI SAUCE TEXT

1477 | 1.0610 | | 1.0464 | Do | 1.0610 | | 1.0449 | Do | | | 1.0600 | 1484 | 1.0423 | 1.0330 | 1.0380 | 1485 | 1.0347 | | 1.0336 | 1483 | 1.0464 | 1.0437 | 1.042 | Do | | 1.0420 | 1.0446 | Do | | 1.0430 | | Do | | 1.0442 | | 1482 | 1.0441 | 1.0416 | 1.0360 | Do | 1.0444 | 1.0419 | 1.0410 | Do | 1.0447 | 1.0424 | 1.0413 | 1481 | 1.0449 | 1.0410 | 1.040 | Do | 1.0449 | 1.0410 | 1.041 | Do | | 1.0418 | 1.0397 | 1480 | | 1.0430 | 1.036 | Do | | 1.0420 | 1.040 | Do | | 1.0429 | 1.044 | Do | | | 1.0407 | 1496 | 1.0340 | 1.0330 | | Do | 1.0341 | 1.0326 | | Do | | 1.0326 | | Do | | 1.0346 | | 1.0299 Do | | 1.0341 | | 1.0303 Do | | 1.0341 | | 1.0343 Do | | | | 1.033 1515 | 1.0351 | | | 1.036 Do | 1.0352 | | | 1.035 1519 | 1.0380 | | | 1.0377 Do | | | | 1.0383 Do | | | | 1.0329 Do | | | | 1.0350 1521 | 1.0440 | | 1.0410 | 1.0439 Do | | | 1.0439 | 1.0448 1522 | 1.0500 | | 1.0428 | 1.0493 Do | | | 1.0455 | 1.0508 1524 | 1.0519 | | | 1.0504 1524 | | | | 1.0529 Do | | | | 1.0510 1526 | 1.0519 | | 1.0472 | 1.0529 Do | | | 1.0463 | 1.0525 1528 | 1.0519 | | 1.0509 | 1.0514 Do | | | 1.0485 | 1.0514 1530 | 1.0252 | | 1.0281 | 1.0260 Do | | | | 1.0264 Do | | | | 1.0269 1531 | 1.0291 | | 1.0312 | 1.0294 Do | | | | 1.0311 Do | | | | 1.0313 ------+---------------+---------------+---------------+-------------- [18] Table 7 gives the results obtained in the determination of specific gravity of several samples of pulp by different methods. The specific gravity given in the first column under the head “Centrifuging at 68° F.” has been proved to be correct by other analytical methods. It will be noted that where duplicate determinations are given in this column they agree with each other very closely. The errors in the other methods in determining specific gravity are shown in the remaining columns. It will be noted that the duplicates given in these columns vary materially from each other. It should be stated that the results given under the heading “Pouring cold and whirling by hand” were obtained by much more careful work than is practicable in the factory. The flasks in which the determination was made were equipped with a bail, as shown in Fig. 5. page 44, and the samples were whirled by hand until air bubbles were eliminated as far as practicable by that method. The results, in this column are therefore much more accurate than are obtained by the method as ordinarily practiced. It was thought that better results might be secured by modifying the construction of a cup in such a manner as to permit it to be filled by dipping below the surface of the pulp in the kettle. A bail made of 3/16-inch wire was, therefore, soldered to the opposite side of the cup (see Fig. 5). By means of the bail the cup was lowered into the kettle. After it was filled with the pulp the attempt was made to remove air bubbles by repeatedly giving the bail a quick twist or circular motion with a sudden stop. The cup was then brought quickly to the surface of the kettle and “struck off” with a straight edge, the outside of the cup and bail washed quickly with water, dried, and the cup and contents weighed. In using this method the steam is turned off, and as soon as the foam subsides the cup is sunk well below the surface of the pulp. At this time the heat in various portions of the kettle is of course uniform, by reason of the thorough mixture caused by the vigorous boiling. Owing to the large mass of rather viscous material, and the heat of the kettle itself, the contents of the kettle cool slowly, and even after 10 minutes the temperature does not decrease more than 1° F., except at the very surface of the pulp. As a result of several observations, it was found that a thermometer bulb held 3 inches below the surface of the pulp showed a lowering of temperature of not more than 1° F. in 10 minutes and a lowering of only 0.5° F. in from 5 to 7 minutes. The bail employed was about 6½ inches wide and 8 inches long. There was some difficulty, owing to the pulp spattering on the hands of the operator because of the air escaping from the cup. This might be diminished by the use of a longer bail, or by wearing suitable gloves. When evaporating tanks are used it will probably be necessary to attach the bail to a stick or support of some kind. In addition to permitting this method of filling, the bail has the additional advantage that the cup full of pulp may be handled for washing and conveying to the balance much more conveniently and with less danger of spilling than with the handle on the side of the cup. Again, the bail does not heat when the cup is filled with hot pulp, and for that reason is easier to handle. (d) HYDROMETER METHOD Hydrometers are of little value in determining the specific gravity of tomato pulp. With cold pulp they cannot be used at all. With hot pulp a relatively slender hydrometer comes to rest and readings can be taken with more or less accuracy. The value of the reading is relative to the specific gravity of the pulp and varies with the shape of the hydrometer and with the character of the pulp. It is necessary therefore to obtain the relation between the reading of the hydrometer in the hot pulp and the specific gravity (obtained by an accurate method) of the same pulp cooled without evaporation. In the hands of a careful operator some manufacturers have found hydrometers (used with hot pulp) helpful in making pulp of uniform specific gravity. The hydrometer gives much more accurate results with the filtrate of pulp. As shown on page 31, there is a direct relation between the specific gravity of tomato pulp and of the liquor obtained by filtering or straining the same, so that when the specific gravity of the latter is known that of the former may be ascertained readily by means of a table. This method is peculiarly applicable to the examination of cyclone juice and light pulp from which the insoluble solids may be removed quickly by straining through a cloth, and it therefore affords the most rapid method that is available to the average factory for determining the specific gravity of cyclone juice. In Table 8 are given a series of corrections making it possible to use this method at any temperature between 50 and 80° Fahrenheit. The more closely the readings are taken to 68° F. the more accurate the results. Moreover, when it is attempted to strain the insoluble solids from hot pulp or cyclone juice, considerable evaporation occurs, causing concentration of the product and producing an error in the results. When hot pulp is handled, therefore, it must be strained as quickly as possible, and more accurate results may be obtained if the pulp is cooled quickly before straining. This may be done by placing in a large can and stirring vigorously while the can stands in ice water, or shaking under water in a large flask. There are several forms of hydrometer which may be used for determining the specific gravity of the filtrate. The ordinary specific gravity hydrometer is the most logical form to use, since it gives the specific gravity directly. Unfortunately, specific gravity hydrometers with the particular marking required for this work are not a stock article, and would, therefore, have to be made to order. For this reason they would be difficult to obtain and not easily replaced if broken. The Brix hydrometer appears to solve the difficulty. This hydrometer has no direct relation to specific gravity, but Brix readings can, of course, be converted to the specific gravity readings by a table arranged in parallel columns. Table 9 gives the specific gravity of tomato pulp and the corresponding Brix reading of the filtrate. The Brix hydrometer gives directly the per cent of sugar in a solution of cane sugar, one degree Brix being equivalent to one per cent sugar at the temperature for which the hydrometer was calibrated. This fact and the ordinary purpose for which the instrument is manufactured are of no interest to us in this connection, however. The Brix hydrometer of the range desired for the examination of cyclone juice and pulp is a stock article and can be secured readily. The instrument can be used with the same accuracy as the specific gravity hydrometer, and the results obtained by it, after correcting for temperature by Table 8, are converted into terms of specific gravity by means of Table 9. The determination of the specific gravity of pulp by means of the hydrometer reading of the filtrate obtained from the pulp has several advantages over the ordinary method of weighing a measured quantity of the pulp. When applied to pulp manufactured from whole tomatoes, the method is reasonably accurate. It is also very rapid and the equipment required is inexpensive. This method is especially applicable to the examination of pulp manufactured from whole tomatoes. It is less applicable to trimming stock pulp, although even with that product the method will be of value, especially for the examination of cyclone juice for the purpose of controlling concentration. With pulp manufactured from trimming stock, the relation of the specific gravity of the pulp to the specific gravity of the filtrate obtained from it will vary according to the nature of the raw material used and also according to the method of manufacture. It seems probable, therefore, that after a manufacturer has determined this relation as applied to his own product, he may be able to use this method with reasonable accuracy even in connection with trimming stock pulp. The method is adapted especially to the examination of cold pulp or cyclone juice. The following apparatus is used in this method: 1 Brix hydrometer, graduated at 20.0° C., with a range of 1–10°, graduated in 1/10°. 1 Cylinder of heavy glass, lipped, height 12 inches, diameter 2 inches. 1 Chemical thermometer, graduated in Fahrenheit system up to 212° F. Since this apparatus is likely to be broken, it is well for each plant that contemplates using the method to equip itself with at least two of each item mentioned above. The Brix hydrometer mentioned above is suggested because it is a stock article handled by all dealers in chemical apparatus and can be secured quickly. It has the disadvantage that it is relatively large, and in order to use it the filtrate must be prepared in much larger quantity than would be required by a smaller hydrometer. By placing orders well in advance with dealers in chemical apparatus special hydrometers may be made with a bulb about one-half inch in diameter and with a total length of five or six inches. Such hydrometers could be used with a cylinder as small as one inch in diameter. They would require much less liquor than is necessary for the Brix hydrometer and therefore would enable the analyst to obtain results much more quickly. In securing such hydrometers it would be well to order several at a time, since it would require several weeks to replace any that may be broken. The details of the method are as follows: Place a piece of cotton cloth of about the texture of ordinary glass toweling over a clean, dry container 10 or 12 inches in diameter or over a No. 10 can. Pour on the cloth a suitable amount of the pulp or cyclone juice to be examined, pick the cloth up by the corners and squeeze gently to separate the greater part of the insoluble solids. The strained liquid left in the vessel will be more or less turbid, according to the pressure exerted in squeezing. The amount of insoluble material producing this turbidity, however, is not usually sufficient to interfere with the examination of the product by means of a hydrometer. If, however, it is necessary to exert considerable pressure to get the amount of filtrate desired and the turbidity is therefore considerable it will be necessary to pass the liquor through a second filter, which, of course, may be done quickly. Transfer this strained liquid, which for the sake of convenience we will designate as “filtrate,” to the 2-inch cylinder described above, and lower the Brix hydrometer into it until the hydrometer floats. When the hydrometer, becomes stationary, the reading on the stem is taken. In reading the hydrometer it will be noted that, owing to the meniscus, the liquid immediately at the stem rises one or two divisions above the general surface. The reading at the lowest point of the surface is desired. In reading the stem, therefore, allowance for the meniscus should be made and a reading recorded one or two divisions on the scale below the extreme height of the meniscus on the stem. The reading so obtained is recorded as the Brix hydrometer reading of the filtrate. After determining the Brix reading of the filtrate from the tomato pulp, the corresponding specific gravity of the pulp may be obtained from Table 9. The result obtained by the method should be corrected to the temperature of 68° F., according to Table 8. If it is desired to use the reading of the filtrate from cyclone juice for the purpose of controlling the evaporation of tomato pulp, suitable directions are given below under “Evaporation to Specific Gravity Desired.” IMPORTANCE OF ACCURACY IN DETERMINING SPECIFIC GRAVITY The description of the tables given in the following page is intended for those operators who desire to take the trouble to obtain the specific gravity of raw product. Where, as is often the case, the pulp is sold under definite specifications for specific gravity, the care necessary to make these observations with a considerable degree of accuracy will be found to be an economy. If a product be shipped that is materially below the specific gravity stipulated, the manufacturer will of course be docked and the loss will be considerable. On the other hand, the specific gravity should not be materially above the specifications. The buyer, who is usually a manufacturer of ketchup, desires the pulp of the specific gravity stipulated, and a higher degree of concentration is therefore not a mark of superiority in pulp intended for that purpose. Moreover, material increase in concentration above the specifications of the purchaser causes considerable loss by reason of reduced volume. For instance, 100 gallons of pulp with a specific gravity of 1.036 are equivalent to 103 gallons of a pulp with a specific gravity of 1.035. Again, 100 gallons of pulp with a specific gravity of 1.040 are equivalent to 114.7 gallons of pulp with a specific gravity of 1.035. When these figures are considered with reference to the entire output of the season, it is apparent that the determination of the specific gravity of the final product is of considerable importance, and will warrant care and, if necessary, the employment of a man who is competent to do the work accurately. This is well illustrated by an experience of one of the large pulp makers, who was selling pulp under specification of 1.035 specific gravity. Owing partly to an error in his specific gravity apparatus, he was actually turning out pulp of a specific gravity varying from 1.040 to 1.050. In other words, each 100 cases of pulp he delivered were equivalent to from 115 to 126 cases of pulp of 1.035 specific gravity. While this manufacturer was using the greater part of the pulp himself, he had contracted to sell a considerable amount of it, and all that was supplied before the error was noticed was sold at a loss, whereas after the error was discovered he supplied pulp well above the specifications of the buyer at a substantial profit. Even then his profit was not what it should have been. His output would have been 10 per cent greater than it was if the specific gravity of his product had just complied with his specifications. Another manufacturer who sold his pulp under the specification of 1.035 specific gravity, received a complaint from one of the largest buyers of pulp in the country that the specific gravity was low. The manufacturer then examined samples, which he had retained in his possession, of the various runs, using the method described on page 41, under the head of “Specific gravity of cold pulp without centrifuging.” Seventeen samples in all were examined, and he obtained an average specific gravity of 1.0276. The purchaser had reported a specific gravity of 1.0315–.0039 higher than that obtained by the maker. The manufacturer then brought duplicate samples to this laboratory and the specific gravity was determined in all of them by the method described on page 34, “After centrifuging to eliminate air bubbles.” While this work was being done the manufacturer himself desired to check the mechanical centrifuge, and attempted to remove the air bubbles from the same samples by swinging the specific gravity cups by hand. He made a special effort to remove the air bubbles in this way, devoting nearly a day to the examination of the 17 samples. Notwithstanding his unusual care, his average specific gravity was 1.0318, while the centrifuge method gave 1.0328. It will be noted that the specific gravity as determined by the centrifuge method was .0013 higher than that obtained by the purchaser, though the latter used a more accurate method than has ordinarily been employed in this determination. This difference has ordinarily been regarded in the industry as insignificant. It is apparent that it is not negligible, however, when we consider that the difference in yield involved amounts to over 4.5 gallons in 100 gallons of pulp. It is true that all these results are lower than the specifications for which this particular pulp was sold, but the incident illustrates the importance of an accurate determination of specific gravity. EVAPORATION TO THE SPECIFIC GRAVITY DESIRED Manufacturers of tomato pulp have considerable difficulty in securing a product of uniform concentration and in determining at what point to stop evaporation. Some manufacturers turn off the steam when it is believed that the concentration has gone far enough and make a hasty determination of specific gravity. If it is found the concentration is not as great as is desired, heating is resumed for a time and the specific gravity again determined. Others make but one determination