Tomato products: pulp, ketchup, and chili sauce.

by W. D. Bigelow; A. E. Stevenson; National Canners Association

FACTORY CONTROL OF THE COMPOSITION OF KETCHUP

Ketchup of uniform color, consistency and taste can be produced only by controlling the quality and quantity of its constituents. Therefore, any satisfactory method of control necessitates the determination of the solids in the batch of cyclone juice before sugar, salt, vinegar and spices are added. Control, based solely on uniform specific gravity of the finished product, assures only that the specific gravity is uniform; it does not assure uniformity in consistency, sweetness, acidity, or in any other characteristic of the product.

Since, under any specific procedure in a factory, the distinctive tomato flavor and the consistency of the finished product depend entirely on the tomato solids, and since about half the final acidity and sugar content is derived from the same source, the control of the tomato solid content is especially important.

Fortunately the solids in cyclone juice have a fairly uniform composition. The ratio of total solids to insoluble solids is fairly constant, likewise the ratio of sugar to acid. The sugar in cyclone juice varies from about 42 per cent to 54 per cent of the total solids, averaging about 50 per cent.

As the consistency or body of ketchup is due chiefly to the tomato solids, the amount of evaporation necessary to secure ketchup of the desired consistency from a known volume of pulp measured at the boiling temperature and of known Brix or specific gravity can be determined from [Table 9, page 56]. For instance, if the volume of the boiling pulp is 800 gallons and the corrected Brix reading of the filtrate is 5.10, it is found from [Table 9] that it will be necessary to evaporate to 423 gallons to secure a ketchup of approximately the consistency of 1.040 pulp, to 374 gallons for a consistency comparable to 1.045 pulp and to 334 gallons for a consistency comparable to 1.050 pulp. This evaporation is carried out, of course, with the addition of the necessary ingredients for the making of ketchup. The amount of these ingredients can be varied in order to secure ketchup of the desired flavor.

After having once decided on the amount of ingredients to be used, the manufacture may be standardized. Supposing for instance on evaporating 800 gallons of partly concentrated pulp of Brix of filtrate (5.10) to approximately 334 gallons (calculated from the 1.050 column in [Table 9]) it has been found that the use of 301 pounds of sugar, 26.7 gallons of 100 grain vinegar, 66.8 pounds of salt and 50.2 pounds of onions together with spices gives ketchup of the flavor desired. Dividing the amount of each ingredient by 334, it is found that each gallon of finished ketchup contains .9 pound of added sugar, .2 pound of salt, .15 pound of onions, and about 10 ounces of vinegar. After having determined the amount of each ingredient per gallon of finished ketchup, it is easy to make a table giving the amount of ingredients necessary for a given volume of cyclone juice or concentrated pulp of any gravity. In [Table 11] such calculations are made. This table is based on securing a ketchup having the consistency of 1.050 pulp and starting with 800 gallons of boiling pulp of specific gravity 1.0220 (Brix reading of filtrate 5.10). Some manufacturers may desire to base the amount of ingredients on 100 gallons or multiple of 100 gallons of finished ketchup. This may be done by first making out a table similar to 9 and then calculating the amount of pulp and other ingredients for 100 gallons of ketchup. This would, however, involve considerable work as unless the pulp used had a constant specific gravity, a calculation of the quantity of each ingredient would have to be made for the volume of pulp for each batch.

Table 11.—Manufacture of Ketchup. Quantity of Constituents to be Added to 800 Gallons of Boiling, Partly Concentrated Pulp

Specific gravity of pulp at 68° F.	Filtrate from pulp		Volume of finished ketchup	Added constituents
	Degrees Brix at 68° F.	Specific gravity at 68° F.		Sugar	100-grain vinegar	Salt	Onions
			_Gals._	_Lbs._	_Gals._	_Lbs._	_Lbs._
1.0154	3.50	1.0137	226.0	203	18.1	45.2	33.0
1.0158	3.60	1.0141	232.0	209	18.5	46.4	34.8
1.0162	3.70	1.0145	239.0	215	19.1	47.8	35.9
1.0166	3.80	1.0149	245.0	221	19.6	49.0	36.8
1.0170	3.90	1.0153	252.0	227	20.2	50.2	37.8
1.0174	4.00	1.0157	258.0	232	20.6	51.8	38.7
1.0178	4.10	1.0161	265.0	239	21.2	53.0	39.8
1.0182	4.20	1.0165	272.0	245	21.7	54.4	40.8
1.0186	4.30	1.0169	278.0	250	22.2	55.6	41.7
1.0190	4.40	1.0173	285.0	257	22.8	57.0	42.8
1.0194	4.50	1.0177	292.0	263	23.4	58.4	43.8
1.0199	4.60	1.0181	299.0	269	23.9	59.8	44.9
1.0202	4.70	1.0185	306.0	275	24.5	61.2	45.9
1.0206	4.80	1.0189	313.0	282	25.0	62.6	47.0
1.0211	4.90	1.0193	320.0	288	25.6	64.0	48.0
1.0216	5.00	1.0197	327.0	294	26.2	65.4	49.1
1.0220	5.10	1.0201	334.0	301	26.7	66.8	50.2
1.0224	5.20	1.0205	341.0	307	27.3	68.2	51.2
1.0228	5.30	1.0209	347.0	312	27.8	69.4	52.1
1.0232	5.40	1.0213	354.0	319	28.3	70.8	53.2
1.0236	5.50	1.0217	361.0	324	28.9	72.2	54.2
1.0240	5.60	1.0221	368.0	331	29.4	73.6	55.2
1.0244	5.70	1.0225	374.0	337	29.9	74.8	56.2
1.0249	5.80	1.0229	381.0	343	30.5	76.2	57.2
1.0253	5.90	1.0233	388.0	349	31.0	77.6	58.2
1.0257	6.00	1.0237	395.0	356	31.6	79.0	59.3
1.0261	6.10	1.0241	402.0	362	32.1	80.4	60.4
1.0266	6.20	1.0245	409.0	368	32.7	81.8	61.4
1.0271	6.30	1.0249	416.0	374	33.3	83.2	62.5
1.0275	6.40	1.0253	422.0	380	33.8	84.4	63.4
1.0279	6.50	1.0257	429.0	386	34.3	85.8	64.4
1.0283	6.60	1.0261	436.0	392	34.9	87.2	65.4
1.0287	6.70	1.0265	443.0	399	35.4	88.6	66.5
1.0291	6.80	1.0270	450.0	405	36.0	90.0	67.5
1.0295	6.90	1.0274	457.0	411	36.6	91.4	68.6
1.0299	7.00	1.0278	464.0	418	37.1	92.8	69.6
1.0304	7.10	1.0282	471.0	424	37.7	94.2	70.7
1.0309	7.20	1.0286	478.0	430	38.2	95.7	71.8
1.0313	7.30	1.0290	485.0	437	38.8	97.1	72.8
1.0318	7.40	1.0294	492.0	443	39.4	98.5	73.8
1.0322	7.50	1.0298	499.0	449	39.9	99.9	74.9
1.0326	7.60	1.0302	506.0	455	40.5	101.3	76.0
1.0330	7.70	1.0306	513.0	462	41.1	102.7	77.0
1.0335	7.80	1.0310	521.0	469	41.7	104.2	78.2
1.0339	7.90	1.0315	529.0	476	42.3	105.8	79.4
1.0343	8.00	1.0319	536.0	482	42.9	107.2	80.4
1.0347	8.10	1.0323	543.0	489	43.5	108.6	81.5
1.0352	8.20	1.0327	550.0	495	44.0	110.0	82.6
1.0356	8.30	1.0331	557.0	501	44.5	111.4	83.6
1.0361	8.40	1.0335	564.0	508	45.1	112.8	84.7
1.0365	8.50	1.0339	571.0	514	45.7	114.2	85.7
1.0369	8.60	1.0343	578.0	520	46.2	115.6	86.8
1.0374	8.70	1.0348	585.0	527	46.8	117.0	87.8
1.0379	8.80	1.0352	592.0	533	47.4	118.4	88.8
1.0383	8.90	1.0356	600.0	540	48.0	119.0	90.0

The use of [Table 11] gives a ketchup of medium concentration. Using this as a basis the manufacturer can decide the extent to which he should evaporate to secure a ketchup of the consistency desired and modify the table accordingly.

Final concentration of the ketchup is controlled in the same manner as for pulp, either by a gauged tank or by specific gravity determination. If we start, therefore, with a given volume of partially concentrated cyclone juice and determine the solids present, we can in every case quickly ascertain from the appropriate table the number of gallons of finished product we should obtain, and the gauge stick or attached gauge glass will indicate when to stop evaporation in the tank. One advantage of measuring the original volume at the boiling temperature is that no temperature corrections are necessary, as both the initial and final temperature measurements are approximately the same.

The final concentration may be controlled, as stated above, by determining the specific gravity of the finished product by one of the methods given under pulp (see page 33 and following). The determination of specific gravity at this point will probably give more accurate results than the use of a gauge stick, and is to be recommended for use with the finished product, provided the added constituents have been standardized. The method described on page 42 for determining the specific gravity of hot tomato pulp, may be used for obtaining the per cent of solids in the boiling cyclone juice in place of the Brix spindle reading on the filtrate.

[Table 11] for controlling the concentration of finished ketchup is based on the idea that there shall be a definite volume of partly concentrated pulp in the tank when the inflow of cyclone juice is stopped and the sample is taken for analysis. In this respect, this method of controlling the concentration of ketchup varies from the method described on page 54 for the control of the concentration of tomato pulp. It is sometimes convenient to secure this definite volume by filling the tank to a greater height than is desired and evaporating until the desired volume is secured. When this point is reached the sample of pulp is taken for specific gravity and steam is again turned on the tank.

The Abbé refractometer may also be used for controlling the final concentration of the ketchup. This provides a very simple and quick method for determining the percentage of solids. It requires but a few drops of the filtered liquor from the ketchup to make the determination. The reading may be taken and the calculation made in one or two minutes’ time by use of Tables 13 and 14.

The table for calculating the solids from the refractometer reading is Geerlig’s table for dry substance in sugar-house products, and is taken from the Methods of the Association of Official Agricultural Chemists, 1919. The entire table is not given but only the range over which it might possibly be desired to use it in the control of the manufacture of ketchup.

The results by this method are only approximate, but are sufficiently accurate for manufacturing control. [Table 12] gives a comparison of the solids obtained by drying in vacuum at 70° C. with results obtained by the refractometer.

Table 12.—Solids in Ketchup Obtained by Drying in Vacuum at 70° C. and by Abbé Refractometer from Geerlig’s Table

Solids in tomato ketchup
By drying in vacuum at 70° C.	By Abbé refractometer
Per cent	Per cent
29.5	29.0
30.0	29.4
32.8	32.4
28.0	27.9
22.0	21.8
27.7	28.0

There are several errors in this determination which partially compensate for each other and give results fairly comparable with those obtained by drying. The refractometer of course determines only soluble constituents. Since salt gives a higher refractive reading than the same per cent of sugar, and since tomato solids give a higher refractive reading than the same percentage of sugar, and since any acetic acid of the vinegar is also read as solids on the refractometer, the total increase in reading due to these different factors nearly compensates for the insoluble solids of the ketchup.

The variation of the per cent of solids as obtained by the refractometer from that obtained by drying will depend somewhat on the composition of the ketchup and in using the refractometer it is advisable to also determine the solids by drying on a few samples to obtain the relation between the two figures for that particular ketchup.

Table 13.—Refractive Index and Per Cent Solids in Tomato Ketchup [21]

Refractive index	Per cent solids	Decimals to be added for fractional readings
1.3484	11	0.0001 = 0.05
1.3500	12	0.0002 = 0.1
1.3516	13	0.0003 = 0.2
1.3530	14	0.0004 = 0.25
1.3546	15	0.0005 = 0.3
1.3562	16	0.0006 = 0.4
1.3578	17	0.0007 = 0.45
1.3594	18	0.0008 = 0.5
1.3611	19	0.0009 = 0.6
1.3627	20	0.0010 = 0.65
1.3644	21	0.0011 = 0.7
1.3661	22	0.0012 = 0.75
1.3678	23	0.0013 = 0.8
1.3695	24	0.0014 = 0.85
1.3712	25	0.0015 = 0.9
1.3729	26	0.0016 = 0.95
1.3746	27	0.0001 = 0.05
1.3764	28	0.0002 = 0.1
1.3782	29	0.0003 = 0.15
1.3800	30	0.0004 = 0.2
1.3818	31	0.0005 = 0.25
1.3836	32	0.0006 = 0.3
1.3854	33	0.0007 = 0.35
1.3872	34	0.0008 = 0.4
1.3890	35	0.0009 = 0.45
1.3909	36	0.0010 = 0.5
1.3928	37	0.0011 = 0.55
1.3947	38	0.0012 = 0.6
1.3966	39	0.0013 = 0.65
1.3984	40	0.0014 = 0.7
1.4003	41	0.0015 = 0.75
		0.0016 = 0.8
		0.0017 = 0.85
		0.0018 = 0.9
		0.0019 = 0.95
		0.0020 = 1.0
		0.0021 = 1.0

In using [Table 13], find the refractive index which is next lower than the reading actually obtained and note the corresponding whole number for the per cent of dry substance. Subtract the refractive index obtained from the table from the observed reading; the decimal percentages corresponding to this difference, as given in the column so marked, is added to the whole per cent of solids as first obtained.

Correction must also be made for the temperature if above or below 28° C. The temperature correction is obtained from [Table 14]. For instance, suppose the refractive index was 1.3750 and that the temperature was 25° C. The per cent of solids as obtained from the table would be 27.2. The correction for temperature would amount to .14, which would be added to this reading, giving 27.34 as the per cent of solids.

Table 14.—Corrections for Temperature to be Used with Table 13

Temperature, ° C.	Per cent of solids.
	10	15	20	25	30	40
	To be subtracted
20	0.55	0.56	0.57	0.58	0.60	0.62
21	.48	.49	.50	.51	.52	.54
22	.42	.42	.42	.44	.45	.47
23	.34	.35	.36	.37	.38	.39
24	.27	.28	.28	.29	.30	.31
25	.21	.21	.22	.22	.23	.23
26	.13	.14	.14	.15	.15	.16
27	.07	.07	.07	.07	.08	.08
	To be added
29	0.07	0.07	0.07	0.07	0.08	0.08
30	.13	.14	.14	.14	.15	.15
31	.21	.21	.22	.22	.23	.23
32	.27	.28	.28	.29	.30	.31
33	.34	.35	.36	.37	.38	.39
34	.42	.42	.43	.44	.45	.47
35	.48	.49	.50	.51	.52	.54

Whether or not ketchup should be processed after filling into bottles depends on the conditions under which it is bottled. If the bottled product can be sealed at 180° F. or better a process is not necessary and is an unnecessary expense and waste of time, besides it may injure the color of the product. With the modern type of equipment it is possible to fill the bottles at a temperature which obviates sterilization. Care must be taken that the temperature of the ketchup in the receiving tank feeding the filler does not fall too low. Care must also be avoided in order not to fill the ketchup at too high a temperature as it results in excessive shrinkage of the contents.

For ketchup filled at relatively low temperature a process should be used. The process necessary will depend upon the temperature at which the ketchup is filled and on the time that may elapse between filling and processing. Sanitary conditions of the factory and equipment are exceedingly important not only in relation to ease of sterilization but also in securing a product of good quality.

In stacking ketchup it is best to stack the bottles upside down. This tends to prevent darkening of the ketchup in the neck of bottle, a condition known as “black neck.” It has been our experience that wherever this condition has occurred it is due to leakage of air into the bottles. Stacking bottles in this way undoubtedly keeps the cork of the cap moist and makes the seal more effective.