40 THE ANALYST. THE FACING OF RICE. BY CECIL H. CRIBB, B.Sc. LOND., F.I.C., AND P. A. ELLIS RICHARDS, F.I.C. (Read at the Meeting, February 7, 1906.) IT has been a matter of more or less general knowledge for some years that rice is faced, i.e., polished, with the aid of some extraneous substances, but we are not aware of any reEerences to the subject beyond a note in the ANALYST (vol. ii., p. 152) on t L waxed rice,” a statement in the Bdzsh Food Journal (1900, p. 46) that rice is finished with the aid of oil, paraffin oil being sometimes employed, and a paper by Matthes and Muller (Zeit. o f l e d . Chenz., 1905), abstracted in the ANALYST (vol. xxx., p. 206). These authors mention the use of ‘‘ talc ” as a coating material for various cereals, including rice. I t was formerly the custom in some retail businesses, and may be so now, to polish the rice by shaking in a bag of sheepskin or other suitable material, the process being known as “trouncing.” With the advent of machinery this simple method is no doubt a thing of the past ; but most of the earlier recorded analyses plainly show that, whatever the process employed, it did not as a rule involve the addition of any appreciable amount of mineral matter.The following figures for the total ash of rice are given by the authors named : Boussingault ... ... ... ... ... ... _ . I ... Poggiale ... ... ... 0 . . ... ... ... ... Cooley’s “ Encyclopaedia ” ... ... ... ... ... Jago (‘‘ Chemistry of Wheat Flour,” p. 233) ,.. ... Wynter Blyth (“ Foods : Composition and Analysis,” p. 214) ... Leffmann and Beam (“Food Analysis,” p.101) ... ... ... Leach (“ Food Inspection and Analysis,” p. 213) : Unhulled ... ... ... ... ... _.. ... Unpolished ... ... ... ... ... ... ... Polished ... Fresenius ... ... ... ... ... ... ... ... Polson ... ... ... ... ... ... ... ... ... ... Bell (“ Analysis and Adulteration of Foods,” p. 86) ... ... ... ... ... ... ... ... ... Total Ash. 0.5 per cent. 0.52 ,, 0.9 9 , 0.32 ,, 0.5 9 , 0.28 ,, 0.28 ,, 0.45 ,, 0.3 to 0.6 per cent. 4.09 per cent. 1.15 ,, 0.46 ,, Hassall, in a complete analysis of the ash, gives the silica as 3-35 and Leach as 6.14 per cent, of the total ash. We have recently had occslsion to examine a number of samples submitted to us under the provisions of the Sale of Food and Drugs Acts, and the very high proportion of ash in some of the samples, together with the presence of a substantial amount of mineral matter insoluble in hydrochloric acid, plainly indicated that some inorganic substance foreign to rice was present.Table I. gives the total ash, together with the soluble ash and the ash insoluble in hydrochloric acid, in the samples referred to, and it will be seen at a glance that in every case but one the polished samples exhibit an increased total ash and a largely increased insoluble ash, as compared with the unpolished samples, thus clearly establishing the connection between the polishing and the excess of mineral matterTHE ANALYST. 41 Also it may be mentioned that the sophisticated samples can be at once distinguished by the appearance of the ash as obtained in a muffle furnace.Genuine rice yields a fused glassy mass, whilst the ash of the polished samples exhibits a powdery appear- ance, and frequently retains, in skeleton form, the shape of the original granules. Further, it will be noticed that the variations in the total ash are almost entirely due to the substances insoluble in acid, the soluble ash being not only fairly constant in amount, but also almost always under 0.5 per cent.-ie., within the limits of variation of the ash of natural unpolished rice. TABLE I. Samples of iTnTcnown Ow@ii. 1. 2. 3. 4. 5 . 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 26. 27. 28. * 25. Price per lb. - lgd. l*d. 3d. - - - - - - -- 2d. - - 2d. Id. 2d. Id. 2d. 2d. l i d . 3d. 2id. 14d.2d. 24d. 2d. - Finish. Total Ash. 0.29 0.31 0.32 0.32 0.32 0.32 0.33 0.37 0.38 0.42 0.57 0.52 0.64 0.70 0.80 0.83 0.83 0.85 0.85 1.00 1.02 1-07 1.07 1.50 1.60 1.92 2.00 2.22 Insoluble Ash. trace 0*;05 trace 0.01 0.01 0-035 0.03 0.02 0.02 0.18 0.25 0.30 0 *40 0.41 0.40 0.44 0.39 0.48 0.53 0.71 0.66 1.10 1.10 1.46 1.55 1.65 ,, Residual Ash. 0.29 0.31 0.32 0.315 0.32 0.31 0.32 0-335 0.35 0.40 0.55 0.34 0.39 0.40 , 0.40 0.42 0.43 0.41 0.46 0-52 0.49 0.36 0.41 0.40 0.50 0.46 0.45 0.57 On further examination it was found that by agitating the rice with water and pouring off the turbid liquid, after the grains had' settled to the bottom, and repeating the operation two or three times, the fine particles thus removed from the surface contained practically the whole of the insoluble ash, while the residual grains had the ash of genuine unpolished samples.42 THE ANALYST.TABLE 11. Insoluble Ash. No. 25 ... ... ... Patna ... ... ... No. 12 ... ... No. 26 ... ... ... ... 1.10 0.73 0.18 1.46 Ash of Powder removed by Levigation. 1-05 0.68 0.25 1.52 More detailed analyses of the mineral matter in the samples will be found in Table V. It appears that, while the ash of the unpolished rice contains only a trace of insoluble matter, and from 9 to 11 per cent. of magnesia (MgO) in a soluble form, in the polished rice the insoluble portion almost invariably forms at least 40 per cent. of the total ash, and consists mainly of magnesia and silica. Although the substancs used in the polishing process apparently adds com- paratively little to the amount of soluMe ash, nevertheless, the latter invariably contains an increased amount of magnesium, the result, no doubt, of the partial decomposition of the silicate by fusion with the alkaline salts of the soluble ash, as the following figures show : TABLE 111. Percentage of MgO in portion of Ash Soluble in HC1.Rice. Carolina, unpolished ... ... ... 11.3 per cent. Patna, polished ... ... .I. ... 23.5 ,, Java, polished (A) ... ... ... 20.2 ,, 8 9 ‘2 (B> ... ... ... 21.2 ,, ,, polished ... ... ... 24.5 ,, I t may be taken for granted, therefore, that a compound of magnesia, and silica is largely, though not universally employed in the polishing process. To get further information we have examined a number of samples of known origin and of every price and quality, very kindly supplied to us by some of the largest wholesale and retail houses in the trade, and the analyses of these are set forth in Table IV., The conclusions already arrived at are fully borne out by the foregoing figures, for with the exception of the samples described as ‘‘ oil polished,” all the polished samples contain excess of mineral matter, showing itself almost exclusively in the insoluble ash.The absolute identification of the foreign substance is difficult, if not impossible. The powder washed off from the outside of the grains, when examined under the microscope, appears as transparent angular particles of irregular outline, which exhibit no particular characteristics, although they have a general resemblance to mica and talc. p.43.THE ANALYST. 43 Rice. Carolina .. .-. ... ... ... ... 9 ) 9 , ,Y .I. ..i ... ... .I. . ... Patna : Foreign cleaned ... 9 9 9 9 ... 2, ' a . ,? ..* ... Broken, London milled 9 , 9 9 9 , '.' English cleaned ... Japan ... ... ... Siam, Dutch cleaned ... Bassein : German cleaned ... ... 9 , ?, .*. 9 9 ,? * * . ... 9 , ... 9 , Java : Natural cleaned ... Foreign cleaned ... Indigo treated . .. ... 1.. Edklish cikmed * ' . . . $ 9 9 9 )) $ 9 $ 2 9 9 ... ... ... Dutch cleaned ... ... ... $ 9 9 ) * a . Burma ... ... ... Rangoon : Rice with hull ... Rice de-hulled in the laboratory . . . Oil-dressed, in Holland * Broken, London milled Antwerp milled ... TABLE IV. Samples of Known Origin. Price. 6d. 44d. 4d. 4d. 3d. to 4d 24d. 24d. 24d. 24d. 3d. 3d. 3d. to4a 3a.- 2d. 2d. 2id. 4d. 2d. 2+d. 24d. 24d. 3d. 3d. 3d. 3d. 3d. 14d. - 2ga. - - - - - Finish. Dull PoliLhed 99 Polished Polished (contains damaged grains) Dull Polished Brown Very dull Slightly polished Dull Polished Total Ash. 0.22 0.29 0.68 0.86 0.71 1.07 1-14 0.90 0.80 0.87 0.92 1-08 0.22 0.40 0.77 1.10 0.33 0.78 0.82 1-26 0.7 1 0.74 0.99 1-14 0.40 0.51 0.54 0.73 0.99 0.30 2.62 1-32 0.30 0.52 1.15 Insoluble Ash. 0.01 0.02 0.44 0-41 0.30 0.70 0.73 0.50 0.42 0.47 0.56 0.78 0.001 0.03 0.35 0-60 0.015 0.34 0.44 0.90 0.31 0.43 0.71 0.73 0.07 0.01 0.25 0.35 0.49 trace 1.421- 0.131- 0.01 0.17 0.82 Residual Ash. 0.21 0.27 0.24 0.45 0.41 0.37 0.41 0.40 0.38 0.40 0.36 0.30 0.219 0.37 0.42 0-50 0.315 0.44 0.38 0.36 0.40 0.31 0.28 0.41 0.33" 0.50 0.29 0.38 0.50 - 1.20 1-19 0.29 0.37 0.35 * Probably polished by oil or some other process.+ Practically all silica.44 THE ANALYST, Even the wholesale dealers appear to have no certain knowledge of the modus operandi of the polishing process, which seems to be a carefully-guarded trade secret, and no doubt differs slightly in different countries as regards both the method and the nature of the added substances. Steatite, French chalk, powdered talc, and mica are amongst the substances hinted at. We were informed that two of the Java samples had been treated with indigo in order to improve the colour, but we have so far been unable to verify the statement. The following table shows the composition of these, together with that of the insoluble matter actually found in the samples examined by ourselves : TABLE V.Polished Rice. Carolina ... ... Patna ... ... Java ... ... ... A. Unknown origin B. 9 , 9 , * * * C . 9 , 9 9 . * . French chalk ... Talc ... ... ... Steatite ... ... ..- ... ... ... ... ... ... ... ... ... 1.. Percentage Composition of Silicious Matter. SiO,. 6 1 56 58 62 62 62 58 61 61 57 62 MgO . 22 22 24 22 25 25 28 20 29 30 33 Fe,O, + A1,03. present" 5.8 present" present" 7-01 9.00 4.02 3-6 3 to 4 8.i Assuming that one or other of these substances is used, the difficult question which always confronts the Public Analyst in such matters at once arises-Is this method of treating rice to be regarded as adulteration ? On the one hand, it must be admitted that it is absolutely unnecessary, inas- much as there are other modes of polishing which are not open to the same objection ; and, moreover, there is no reason whatever, apart from the whims of certain purchasers, why the grains should not be left with their natural surface, as, indeed, is the practice of some of the chief rice-eating nations, notably Japan.The proportion of foreign matter present in some of the samples is quite sufficient to constitute a fraud, inappreciable, perhaps, by the individual purchaser, but ample to give to one unscrupulous vendor an pnfair advantage over his more honest rivals. Further, on the medical aspect of the case, it has been suggested to us that there is the possibility that even very small quantities of an insoluble mineral substance may be injurious to health, not, of course, owing to m y chemical action, but merely by the mechanical irritation it might set up, and because of the possible formation of faecal concretions. * Quantity not estimated.THE ANALYST. 45 On the other side, it has been urged that the proportion of foreign matter is at the worst small and at the best negligible; that the amount of irritation likely to be set up must be extremely slight, and would be quite as likely to be beneficial as other- wise by the promotion of peristalsis. As the alleged adulterant is more expensive than the rice itself, there could be no possible temptation to the manufacturer to adopt the process for the purpose of fraud, and in addition to this, it might also be urged that the foreign matter generally is, and always might be, largely removed during cooking. We understand this is the custom of native cooks in India, by whom the rice is always soaked and washed before use. Whatever may be the opinion in regard to the legal aspect of the question, it is somewhat startling to reflect that an article of diet of such common and widespread use, hitherto accepted as one of the purest forms of vegetable food, should so frequently contain a substance of a foreign nature.