MARCH, 1950 Vol. 75, No. 888 The Estimation of Tomato Solids in Tomato Products by a Method Involving the Determination of Lycopene by Absorption Spectroscopy BY F. G. STOCK SYNOPSIS-A method is proposed for the estjmation of tomato solids in tomato products by the determination of lycopene by absorption spectroscopy. The history of work done on the tomato pigment is traced. The theoretical aspects of the determination of lycopene in the presence of carotenes are discussed in the light of experiments carried out by the author. A method giving consistent and reproducible results has been evolved for the extraction of lycopene from tomato products. A suggestion is advanced that the origin of the extracted pigment, whether from a ripe or green tomato, is indicated by the shape of the absorption curve obtained.A series of five graphs is used as an illustration. The lycopene content of (a) English tomatoes in various stages of ripeness, and (b) commercially available concentrated purkes are given. The method is applied to sauces and ketchups at present available. THE Food Standards (Tomato Ketchup) Order, S.R. and 0. No. 1817, 1949,* prescribes a standard for tomato ketchup, catsup, sauce and relish. A tomato solids content of not less than 6 per cent. by weight is specified, and the Order comes into operation for sales by retail on October lst, 1950. The characteristic red pigment of the tomato was first investigated in 1876 by Millardet,l who obtained it in a crystalline state, and also observed the crystals in the flesh of the ripe fruit. He established that absorption in the visible portion of the spectrum of a carbon disulphide solution of the pigment was characterised by two bands in the green region and one in the blue.Later investigators2~3~4~5 found that carotene was present in tomatoes, *See Analyst, 1950, 75, 112. 1 1 i118 STOCK: ESTIMATION OF TOMATO SOLIDS I N TOMATO PRODUCTS BY A [VOl. 75 and considered it to be identical with the pigment obtained by Millardet. The tomato pigment was again studied in 1903 by Schunck,6 who found that the red colouring matter was clearly distinguishable from carotene in appearance, crystal form, solubility and absorption spectrum. The first chemical investigation of lycopene was undertaken by Montanari7 in 1904. His results led him to consider that the tomato pigment was a condensation product of two molecules of carotene, having the formula C,,H,,.In 1910, Willstatter and Escher8p9 isolated from Italian tomato conserve a relatively large quantity of the pure crystalline red pigment, together with a smaller quantity of the yellow pigment, carotene. They found lycopene to be an unsaturated hydrocarbon and to possess the same composition and molecular weight as carotene, namely C4oH5,. It was less soluble than carotene in ether, carbon disulphide, light petroleum and alcohol, and oxidised and bleached more readily. Xantho- phylls and xanthophyll esters were also reported to be present. As a result of the work of Karrer and others,10,11~12,13~14,16 the following structural formula has now been assignedu to the pigment- CH, CH3 CH3 CH, I I I (CH,) 2C : CH-CH,CH,*(C : CHCH : CH) ,*C : CHCH : CHCH : (CCH : CHCH), : dCH&H,CH : C(CH$ , Willstatter and Escher, as well as Montanari, carried out their investigations on the pigment isolated from Italian-grown varieties.Matlack and Sandole proved the pigments contained in Italian-grown tomatoes and in American red and purple tomatoes to be identical. Lubimenko17 considered lycopene to be formed by the oxidation of chlorophyll, but Euler et aZ.18 found that green tomatoes kept at 20" to 21" C. ripened normally in a few days, developing the usual red lycopene colouring. At 30" C. they developed only a yellow colour, and tests showed the presence of carotene, xanthophyll and an unidentified flavone dye, but no lycopene.At 37" C. they turned yellow and spoiled rapidly. Neither light nor its absence had any effect on the rate of colouring. It is believed that lycopene is formed by an enzyme action which is inhibited by the higher temperature. Kuhn and Grundmann16 stated that the chlorophyll content of the green fruit is far too small to account for the formation of lycopene from it. Smithla showed that protection from intense light favours lycopene formation, whereas light is conducive to the maximum production of carotene. Since lycopene is present in mature fruits which have been grown in the complete absence of light and which have therefore never contained chlorophyll, lycopene cannot be an oxidation product of chlorophyll as has been assumed by some investigators. The oil-soluble colour of the tomato has been suggested as a basis for an approximate estimation of tomato solids in tomato products.20 The natural colour of the tomato was extracted with light petroleum, and its visual density determined by means of a Lovibond tintometer fitted with the Rothamsted device.Three analytical techniques are of use in the study of a problem of this nature, namely- (a) The separation of carotenoids by the partition technique between immiscible solvents as described in detail in Thorpe's Dictionary, volume 11.21 (b) Chromatographic adsorption. (c) Spectroscopic criteria using absorption maxima in different solvents. These afford much assistance in the task of characterising carotenoids. EXPERIMENTAL A chromatographic study of the pigment extracted from ripe tomatoes by light petroleum Three zones (i) At the bottom of the column, a rather indistinct, yellowish, diffuse zone, viz., (ii) A well-defined reddish zone, viz., lycopene, in the middle.(iii) At the head of the column, a pinkish ill-defined zone, viz., xanthophylls. A rough idea of the respective proportions present could be obtained from the depths of the various zones. Very approximately, the pigment appeared to be composed of about 90 per cent. of lycopene, the remainder being carotenes with only a very small amount of xanthophylls. This assumption is borne out by the work of Kuhn and Grundmann on the const it u t ion of 1 ycopene. For work of b.p. 80" to 100" C., was made in this laboratory, using an alumina column. separated- a- and p-carotenes.The spectral absorption curve of the extracted pigment was next examined.March, 19601 METHOD INVOLVING THE DETERMINATION OF LYCOPENE 119 in the visible region, a light petroleum (b.p. 80" to 100" C.) solution was employed, and a chloroform solution for the investigation of absorption in the ultra-violet. uch general absorption was observed in the ultra-violet, and it was found necessary to extract the chloro- form solution with 90 per cent. methanol, after which satisfactory absorption curves were b t I 4 cu go.9 V - $0.8 0 v c 0-7 0 $0.6 X - - - - * - 0 4 0.3 0.2 01 00. Fig. 2. - - - - \ ' 1 1 I - ' ' 1 ' 1 ' 1 1 1 ' 1 ' 1 Absorption curve in ultra-violet spectrum for methanol-washed chloroform solution 0.1 -120 [Vol. 75 obtained with very little irrelevant absorption.The spectral absorption curve of the pigment dissolved in light petroleum (b.p. 80" to l0OOC.) was next studied (Fig. 1). Solutions in chloroform and in carbon disulphide were also examined. The following maxima were recorded- STOCK: ESTIMATION OF TOMATO SOLIDS IN TOMATO PRODUCTS BY A Observed Recorded Solution in maxima, mp. maxima, mp.* Light petroleum . . .. .. 605 475 450} cf. { 606 474 444 Chloroform . . .. .. .. 610 480 455 513 480 451 * Morton,Be chart V, p. 60. This identified the pigment as being chiefly lycopene. As further evidence, the ultra-violet curve of a chloroform solution, extracted with 90 per cent. methanol to remove substances giving irrelevant absorption, was determined (Fig. 2). This showed a well-defined maximum at 305 mp., which is in agreement with recorded data.Furthermore, the extinction coefficient at 305 mp. was one-third of that at 475 mp., which again is in accordance with published results.= The shape of the lycopene curve is extremely characteristic. The absorption curves obtained in different solvents have the same shape, but there is a "shift" in the wavelengths of the maximum absorption peaks of the curves. If we compare the carbon disulphide and light petroleum curves, we find that the 505mp. maximum in light petroleum is displaced to 545mp. in carbon disulphide, i e . , towards the red end of the spectrum. The solution does, in fact, appear quite red in carbon disulphide, whereas in light petroleum it is yellowish- red. The effect of carotene on the shape of the lycopene curve was studied using a light petroleum extract of carrots as a source of carotenes.The absorption curve of this solution is shown in Fig. 3. The point of interest is that the absorption at 505mp. is practically Carbon disulphide . . .. .. 5.45 605 - 548 507 - f I \ k lycopene \ ' " L L 1 I r ' ' ' " a ' 1 ' ' A 600 590 580 570 560 550 540 530 520 510 500 490 480 470 460 450 440 430 420 & Wavelength my. Fig. 3. Comparison of a mixed a- and ,%carotene curve and a lycopene curve (light petroleum solutions) negligible, and the first absorption maximum is reached at 485 mp., thus enabling lycopene to be estimated spectroscopically in the presence of carotenes. As confirmation, equal volumes of two solutions of approximately equal concentration, as indicated by the extinction coefficients, were mixed, and the mixed solution evaporated to the same volume.The shape of the absorption curve for this solution is shown in Fig. 4. The actual maximum at 505 mp. was practically unaltered, but the shape of the curve is vastly different. If we assume that the lycopene/carotene ratio in the pigment from ripe tomatoes approximates to 9/1, then Fig. 4 is the curve of a mixture of lycopene and carotenesin the ratio of approximately 9/11.March, 19M)J METHOD INVOLVING THE DETERMINATIOX OF LYCOPEKE 121 0.3 m r n I L 430 60 go Wavelength my. Fig. 4. Effect on the lycopene cume of the addition of ct- and /3-carotenes (light petroleum solutiOn) Fig. 5 . 0.0 6do 5b sio s;o sio s ; ~ s40 s;o sio 5io A 4;o do 4;o 4 ~ 0 4;0 4;0 i;o 4;o 4to Wavelength mp.The absorption curve of the pigment extracted from a green tomato (light petroleum solution)122 STOCK: ESTIMATION OF TOMATO SOLIDS IN TOMATO PRODUCTS BY A [VOl. 76 This confirms the findings of Mills,= that, by selecting suitable wavelengths, accurate quantitative spectral analysis of carotenoid mixtures can be made with an error of less than 2-5 per cent. Another question arising here is the possibility of determining by the shape of the curve whether a given pigment originates from a green or a ripe tomato. This would be possible if the relative proportions of lycopene and carotene altered upon ripening. Kuhn and Grundmann in their work on the constitution of lycopene gave the following figures for the lycopene, carotene and xanthophyll content of the tomato pigment.Green, Half ripe, Fully ripe, mg. per 100 g. mg. per 100 g. mg. per 100 g. Lycopene * . .. . . 0.11 0.84 7.85 Carotene . . .. .. 0.16 0-43 0.73 Xanthophyll . . .. . . 0.02 0.03 0-06 Xanthophyll esters . . . . 0.00 0.02 0.10 This indicates that by inspection of the shape of the curve an inference regarding the origin of the pigment may be drawn. The ratio Emax 505mp./Ema, 475mp. is approximately 8/10 in a normal ripe tomato pigment, and the use of this ratio is now suggested as a criterion. The curve obtained from the pigment of a green tomato is shown in Fig. 5, and its shape is obviously very different from that obtained for the ripe fruit. In order to obtain results on a statistical basis for the lycopene content of tomatoes and tomato products, a method was evolved which gave consistent and reproducible results.Extraction with light petroleum of an aqueous solution gave rise to troublesome emulsions, and it is also doubtful whether a complete extraction of the lycopene is obtained in this way. The use of anhydrous sodium sulphate, followed by hot extraction in a Bolton extractor, was also unsatisfactory. PROPOSED METHOD The method finally decided upon was to dry the material, well mixed with sand, in a vacuum desiccator, and then, after powdering, to transfer to a Bolton extractor. Acetone was used as solvent, light petroleum not being very successful, owing to a form of chromato- graphic separation taking place on the sand column. Further, the penetration of the column did not seem as effective with light petroleum as with acetone.PROCEDURE Weigh accurately about 5 g . of the purke, sauce or ketchup into a stainless steel or porcelain dish. Incorporate carefully, and thoroughly, sufficient sand to make a powdery mass. Allow to dry in an efficient vacuum desiccator over calcium chloride for at least 16 hours. Transfer to a mortar and powder thoroughly. Pack tightly into the liner of the Bolton extractor. Extract with acetone for 3 hours, using a 100-ml. Quickfit pyrex flask, keeping it away from bright sunlight. Evaporate the acetone until nearly dry, then blow the last drops off in a current of air, with the flask removed from the water-bath. Add light petroleum (b.p. 80" to 100" C.) and heat to boiling on the water-bath, cool, and make up to a convenient volume, usually 150 ml.Determine the absorption at 505 mp. in a l-cm. cell, using a constant-deviation spectro- meter in conjunction with a Hilger photometer, a ribbon filament lamp being employed as light source. The full absorption curve may be plotted if required, special note being made of the Em,,. 475mp. Normally, however, only one determination a t 505mp. is required, and this is made in duplicate. If the solution is left in the dark overnight, the E alters very little, but it is advisable t o make the determination without delay. A light petroleum (b.p. 80" to 100" C.) solution of the pigment was refluxed for 3 hours and gave the same reading before and after the refluxing. So for all practical purposes, there is very little destruction of the lycopene under the conditions of the experiment.It was found in a series of experiments that approximately 70 to 80 per cent. of the lycopene was extracted in a few minutes, and 85 to 90 per cent. in about half an hour. To obtain a 95 to 98 per cent. extraction, however, 3 hours were required. It was possible to obtain still more complete extraction by prolonging the time beyond 3 hours, but the further amount extracted, even after prolonged boiling, was proportionately very small. The method outlined above will extract at least 95 per cent. of the lycopene present, and since all theMarch, 19501 METHOD INVOLVING THE DETERMINATION OF LYCOPESE 123 determinations are made under the same conditions, the figures obtained are comparable.The method will give consistent results on the same sample. The question of complete extraction is closely connected with the distribution of lycopene in the tomato. The bulk is easily extracted, but a proportion appears to be held in the fruit in some way. Information on this question is difficult to find, but it seems probable that, with a more complete extraction, the figures obtained by Darbishire on commercial purkes, using a Lovibond tintometer, would have shown a smaller variation than the 40 per cent. he reported.20 Extraction for 3 hours gives the acetone solutions a cloudy appearance, but if the experimental details regarding the evaporation of the acetone are closely followed, the resulting light petroleum solution is quite clear. Light petroleum (b.p.80" to 100" C.) was used as final solvent because of its comparatively high bding-point, so that there is less risk of concentration due to evaporation when transferring the solution to the l-cm. cell of the photometer. Furthermore, the 505 mp. maximum is a very easy one to determine. In calculation it is assumed that the E: 2;. 505 mp. for lycopene in light yetroleurn is approximately 2000, and the Eft:! is calculated for the product under examination. In the case of tomato puries, the total solids, and salt, if any, were also determined, and hence the true tomato solids content. The lycopene content was expressed as (a) micrograms of lycopene per gram of product, or (b) micrograms of lycopene per gram of tomato solids (on the purkes only). RESULTS ,4 number of determinations were made on tomatoes in various stages of ripeness, after preparing purkes by mashing and passing through a sieve to obtain a purke free from skins and seeds.I t will be observed that the lycopene The results obtained are given in Table I. TABLE I THE LI-COPENE CONTENT OF P U R ~ E S PREPARED FROM EKGLISH-GROWN TOMATOES I N VARIOUS STAGES OF KIPENESS Description of tomatoes Green . . .. .. Red-green . . .. Ripe, red-green .. Red, firm (very small) Red, firm . . .. Red, firm . . .. Ripe, red, firm . . Very ripe, some rotten Total solids .. 5.4 . I 4-8 .. 5.4 . . 10.8 . . 7.0 . . 5-2 .. 4.4 .. 5.2 Lycopene +per g. , assuming &&. 505 mp. = 2000, PLg. 3.2 16-0 3.3 16.5 6.6 28.0 12-8 64-0 15.8 79-0 12.5 62-5 12.9 64.5 22.0 110 E:? 505 mp. Lycopene per g.of tomato solids, CLg. 296 344 519 693 1128 1201 1466 2115 content gradually increases, with a very considerable variation between green and over-ripe tomatoes. It is worth noting that, for an average ripe, red, firm tomato, the concentration of lycopene approximates to 1500pg. per g. of tomato solids. With respect to the actual commercial products available to the sauce manufacturers, it should be remembered that nearly all, if not all, concentrated tomato purkes used in this country are imported, and consist of a product manufactured from ripe tomatoes. Unripe tomatoes are used for tomato chutney rather than for tomato sauce or ketchup. In a bulletin issued by the National Canners' Association Research Laboratory of the U.S.A.,25 reference is made to the exclusion of greenish tomatoes in the preparation of purke, because of the development of an objection- able colour.Not only do green tomatoes, or tomatoes with green portions, not have the desired amount of red colouring matter, but the yellow and greenish particles mask and dull the red colour present. Also the amount of pectin naturally occurring in tomatoes is greatest at the time of complete ripeness; this is important, because the pectin present in the finished product contributes to its viscosity. The avoidance of over-ripe tomatoes also is in the interests of the manu- facturer, because the absence of mould is of great importance. The colour of tomato products is an important index of their quality, and greatly influences their commercial value. The manufacturers of purees have a financial interest in avoiding the use of green, partly green and over-ripe tomatoes, and it is highly improbable that they will do anything likely to decrease the commercial value of their products. Thus we may be reasonably assured of a Good pulp can be made only from thoroughly ripe, sound tomatoes.124 STOCK: ESTIMATION OF TOMATO SOLIDS IN TOMATO PRODUCTS BY A [VOl.75 fairly uniform concentrated purke being commercially available to sauce manufacturers] and this is borne out by Table 11. TABLE I1 THE LYCOPENE CONTENT OF MANUFACTURERS’ COXCENTRATED PUREES AND ALSO OF TWO SAMPLES Origin (u) MANUFACTURERS’ PURBES Italian “Rago” . . . . .. Italian “Valnure” ,. .. Italian “Helvia” . . . . .. I talian “Suprema’ ’ . . .. Italian “Soriso” .. . . .. Italian “Catalano” . . .. Portugese “Toiro” . . .. Hungarian “Gschwindt” .. Hungarian “Helins” . . . . Hungarian “Globus” . . . . Hungarian “Golden Pheasant” . . French “U.D.C.” I . .. French “Gourmet” . . . . French “Rolli” . . . . . . Canadian “Smith” . . . . South African “Barclay Vale” . . Australian “O.T. Ltd.” . . . . Total solids, % 33.9 26.4 26.7 33.1 32.5 28.3 37.9 28.0 25.8 27.2 27.6 30-7 27.5 28.1 25-9 27.4 23-8 (b) CANNED UNCONCENTRATED PURBES Australian .. . . . . 11.0 New Zealand . . . . . . 11.2 OF UNCONCENTRATED PURBE NaCII, Yo 2.3 1.9 1.6 3-1 0.7 1.5 2.4 0.2 0.2 0.2 0.2 2.3 0.3 4.5 0.3 0-4 1.9 0.7 0.9 Tomato Lycopene solids, E:%?’ 605 mp. per g . , % PE5 31.6 24.5 25.1 30-0 31.8 26.8 35-5 27-8 25-6 27.0 27.4 28.4 27.2 23-6 25-6 24.0 21-9 108 87 106 91 107 87 110 85 95 82 87 70 92 69 07 77 75 540 435 530 455 535 435 550 425 475 410 435 350 460 345 485 385 375 Average 10-3 31 155 10.3 33 165 Lycopene per g.of tomato solids, 1709 1775 1677 1517 1683 1624 1550 1529 1856 1518 1588 1652 1691 1462 1505 1604 1712 1620 1505 1601 The variation in lycopene content is surprisingly small, and this is all the more remarkable when we consider that these purkes represent random samples from the produce of seven different countries, covering practically the whole world. It would seem a reasonable assumption that 1 g. of tomato solids contains a minimum of 1500 pg. of lycopene, and it is proposed that this figure should be used as a means of estimating the tomato-solids content of an unknown sauce or ketchup.In the manufacture of such products, colouring matter may occasionally be used to maintain a standard colour. In this case, however, a water-soluble dye is used, which is not extracted by the proposed method. In any event, the shape of the absorption curve of lycopene is so characteristic that an analyst, if ever confronted with an oil-soluble dye, would be able to detect its presence from the shape of the curve. It is very unlikely, however, that this would be encountered. A number of sauces and ketchups were analysed, with the results given in Table 111. The samples giving low figures were further investigated, and in every case the shape of the absorption curve was the normal curve for lycopene. The E values at 475mp. bore normal relationships to the E values a t 505mp., so that the use of green tomatoes was excluded.To test the accuracy of the method, a number of samples of ketchup of known tomato- solids content were obtained. A series of five samples of ketchup, obtained at different stages in the manufacture of a single batch of tomato ketchup, was analysed, and the lycopene content was found to be practically constant, showing that there is very little loss during the manufacture. Furthermore, about a dozen different purkes were included in this batch of over a ton of ketchup, and the tomato-solids content of each one was known, so that the theoretical cQmposition of the batch could be calculated. The calculated tomato solids approximated to 12.5 per cent., and the actual percentage found by lycopene determination averaged 11.5 per cent. over the five samples.The manufacturers themselves from time to time had analysed their product by Morpeth’s method,26 and this gave figures ranging between 11 and 12 per cent. A ketchup containing exactly 33 per cent. of tomato purke was obtained from one manufacturer, together with a sample of the purke from which it was made. The Eto2:5 505mp. of the purke was 94 and that of the ketchup 29. The solids content of theMarch, 19501 METHOD INVOLVING THE DETERMINATION OF LYCOPENE 125 purke was 27.0 per cent. after allowance for a small amount of salt. The calculated tomato- solids content of the ketchup was therefore 9.0 per cent., and the amount found by lycopene determination was 9.7 per cent. TABLE I11 ,~LPPLICATION OF THE METHOD TO THE ESTIMATION OF THE TOMATO-SOLIDS CONTENT OF A NUMBER OF TOMATO SAUCES AND KETCHUPS AVAILABLE FOR RETAIL SALE (a) TOMATO SAUCES Sample .. .. .. .. 1 E:E% 505 mp. . . .. . . 14 Lycopene, pg. per g. . . . . 70 Tomato solids, assuming 1500 pg. lycopene = 1 g. of tomato solids . . .. .. . . 4.7 Sample . . .. .. .. 10 * . . . 14 lm. 605 mp. . . Lycopene, pg. per g. . . .. 70 Tomato solids, assuming 1500 pg. lycopene = 1 g. of tomato solids . . .. .. . . 4.7 Elo” % (b) TOMATO KETCHUPS Sample . . .. .. .. 18 E:%% 605 mp. . . .. . . 26 Lycopene, pg. per g. . . .. 130 Tomato solids, assuming 1500 pg. lycopene zz 1 g. of tomato solids . . .. .. . . 8.7 Sample . . .. .. . . 27 .. .. 18 Elcm. 505 mp. . . Tomato solids, assuming 1500 pg. lycopene E 1 g. of tomato solids .. .. .. . . 6.0 loo a‘& Lycopene, pg. per g. . . . . 90 2 27 135 9.0 11 20 100 6.6 19 26 130 8.7 28 26 130 8.7 3 21 105 7.0 12 34 170 11.0 20 43 215 14.3 29 30 100 6.7 4 17 85 5.7 13 29 5-8 1.9 21 30 150 10.0 30 31 155 10.3 5 2.1 10-5 0.7 14 21 105 7.0 22 24 120 8.0 31 32 160 10.7 6 24 120 8.0 15 24 120 8.0 23 36 180 1290 32 55 275 18-3 7 0-5 2.6 0.2 16 17 87 6.2 24 12 60 4.0 33 22 110 7.3 8 15 75 5.0 17 11 2.1 0.7 25 31 155 10.3 34 25 125 8.3 9 18 90 6.0 $8 19 75 5.0 From a series of six samples of tomato ketchup supplied by another manufacturer the following results were obtained. Two samples made from Hungarian purke to contain 15.3 per cent. of tomato solids were found to give E:Eh 505 mp. of 40 and 39, corresponding to a tomato-solids content of 13.3 and 13.0 per cent.respectively. Two samples made from French puree to contain 15.0 per cent. of tomato solids were found to give El$:% 505 mp. of 48 and 47, corresponding to a tomato-solids content of 16.0 and 15.7 per cent. respectively. A further two samples made from French pur6e to contain 13.7 per cent. of tomato solids both gave E:::! 505 mp. of 42, corresponding to 14.0 per cent. of tomato solids. One important point remains to be stressed, namely the desirability of defining “tomato solids.” In the experiments on the lycopene content of tomatoes and concentrated purbes, approximately 5 g. were taken for the solids determination, a little water was added, and the mixture was dried to an even film on the water-bath for approximately 1 hour, followed by drying at 100” C.in the oven for 1 hour. Various methods are given in the literature for tomato-solids determination,” q., vacuum desiccation, refractometer methods, etc. It would be in the interests of all concerned if the Food Standards (Tomato Ketchup) Order, S.R. and 0. No. 1817, 1949, defined “tomato solids,” and prescribed a standard method for determination. SUMMARY AND CONCLUSIONS It has been demonstrated that the lycopene content of the tomato and tomato products can be ascertained by a spectroscopic method using the spectral absorption at 505 mp. as a criterion. Furthermore, the effect of carotene on the absorption maximum has been shown to be negligible at 605 mp., even though the shape of the remainder of the absorption curve *See report of A.M.C.Tomato Products Sub-Committee, Analyst, 2941, 66, 319.126 STOCK: ESTIMATION OF TOMATO SOLIDS IN TOMATO PRODUCTS alters as the percentage of carotene increases. It is suggested that the relationship between Em,,. 505 mp. and Em,,. 475 mp. can be used as a criterion of the degree of ripeness of the tomatoes used. A method of extracting and determining the lycopene which gives consistent results has been developed. A suggested factor is given, based on a number of determinations of the lycopene content of English-grown tomatoes in various stages of ripening, and also of commercially available tomato purkes from which sauces and ketchups are normally manu- factured. The factor converts micrograms of lycopene to grams of tomato solids. A table is given of the results obtained in the application of the method to a number of ketchups and sauces at present available.The method does not claim extreme accuracy, but it gives a definite indication of tomato-solids content, and is undoubtably a good “sorting out” test, which may be used in conjunction with other methods of analysis. The analytical procedure involved is very simple, and the determination rapid. [Vol. 75 The author is indebted to the Birmingham Public Health Committee for facilities for carrying out this work, and also wishes to record his thanks to Mr. H. H. Bagnall, the Birmingham City Analyst, for his very helpful encouragement. The writer is very grateful to Mr. D. J. Munns, the Chief Chemist at H.P. Sauce Ltd., Birmingham, for supplying the samples of commercial purke.REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. Lubimenko, V., Rev. Gen. Botan., 1914, 25, 476. 18. 19. 20. 21. 22. Morton, R. A., Vitamins, Adam Hilger, London, 1942. 23. 24. 25. 26. Millardet, A., J. Bot. Jahresber., 1876, 4, 783. Arnaud, A., Compt. Rend. Acad., 1886, 102, 1119. Passerini, N., Staz. Sper. Agrar. Ital., 1890, 18, 545. Kohl, F. G., Untersuchungen ubey des Cavotins und seine physiologischefi Bedeutung it& der Pjianze, Ehring, C., Dissertation Munich, 1896. Schunck, C. A., Proc. Roy. SOC. Lond., 1903, 72, 165. Montanari, C., Staz. Sper. Agrar. Ital., 1904, 37, 909. Escher, H. H., Zur Kenntnis des Carotins und des Lycopiiis, Proxnotionsarbeit, Zurich, 1909. Willstatter, R., and Escher, H. H., 2. physiol. Chem., 1910 64, 47. Karrer, P., and Widmer, R., HeZv. Chim. Acta, 1928, 11, 751. Karrer, P., and Bachmann, W. E., Ibid., 1929, 12, 285. Karrer, P., Helfenstein, A., and Wehrli, H., Ibid., 1930, 13, 88. Karrer, P., Helfenstein, A., Wehrli, H., and Wettstein, A,, Ibid., 1930, 13, 1084. Karrer, P., Helfenstein, A., Pieper, B., and Wettstein, A., Ibid., 1931, 14, 435. Kuhn, R., and Grundmann, C., Bey. Chem. Ges., 1932, 65, 898. Matlack, M. B., and Sando, C. E., J . Biol. Chem., 1934, 104, 407. von Euler, H., Karrer, P., von Krauss, E., and Walker, D., Helv. Chinz. Acta, 1931, 14, 164. Smith, A., Cornell Univ. Agr. Expt. Sta. Mem., 1936, 187, 3. Darbishire, 0. B., Analyst, 1948, 73, 457. Thorpe’s Dictionary of Applied Chemistry, 4th Edition, Vol. 11, 1949, p. 399. Brode, W. R., Chemical Spectroscopy, Wiley, New York, 1946, p, 253. Mills, E. S., Plant Physiol., 1934, 9, 193. Bigelow, W. D., Smith, H. R., and Greenleaf, C. A., “Tomato Products,’’ Bulletin No. 27-L, Morpeth, J. C., Analyst, 1948, 73, 449. Leiflsic, 1902, p. 41. 194 1, Nat. Canners’ Assoc. Research Laboratory, Washington. CITY ANALYST’S LABORATORY BIRMINGHAM