T H E J O I ' R S . 4 L O F Ia\TDL-STRIdL d S D ESGI.\*EERISG
July. 191j
CHEMISTRY
607
T ~ B LIE REACTIONS WITH Gnorrps Group I . .
. . ......
GROUP REAGENTS
Iodine solution
(;roup 11.. , . , , , .
IIillon's or Stokes' reagent (acid nitrate of mercury)
(:roup 1 1 1 . . , . , , , . . ,
Concentrated solution of sodium borate
(;roup I V ,
, , ,
(:roup I'. .
,
, ,
,
,
.,
(;roup 1.1,. . , , . . . .
Solution of sodium hydrate Solution of mercuric chloride Schweitzer's reagent (solution of cupra-ammonia]
of egg, which is sometimes used t o glaze coffee beans t o make t h e m appear better t h a n t h e y really are. .Again t h e thickeners, etc., are used in such products as ice cream and custards, primarily t o add bulk t o the product. and t o gire the material in which they are used a frothy appearance. T h e y are also used in this connection t o make t h e ice cream and custards " s t a n d up." A great many ice cream manufacturers use a so-called "ice cream powder." These "ice cream powders" vary in composition, but generally contain one or more of t h e following: dext r i n , acacia. tragacanth, gelatine, albumen. a n d st:ir ch . This paper deals more specifically with t h e detection of these gelatinizing agents, pasty materials. and thickeners in food products b y a group method. T h e above table, prepared and worked out b y the writer o n actual experiments in the laboratory, places t h e above-mentioned materials in six groups : I---the iodine solution group; 11-the acid nitrate of mercury group: 111-the concentrated solution of sodium borate group; IT-the solution of sodium hydrate group ; \---the solution of mercuric chloride group; TI-the solution of cupra-ammonia group. -4 careful s t u d y of this group method shows t h a t a new means for testing agar-agar has been discovered. This test is based on Groups 11. 111 a n d IT7. The characteristic reactions for agar-agar depend on a new test for acacia in Group 11, t h a t is, one drop of acid nitrate of mercury plus t h e unknonm water solution. which test yields a stringy gelatinous precipit a t e . solzbble i i t c x r c s s of the reageut. Since the reagent in Group 111 precipitates only agar-agar and acacia, it is simply a test t o pr0T-e whether one or both are present in t h e unknown water-soluble mixture. The reagent in Group IT' does not precipitate agar-agar. and hence if no precipitate is obtained here, agaragar is present in Group 111; if a white, cloudy precipit a t e occurs, t h e unknown is acacia, and if a brownish yellow color occurs on heating, t h e unknown is tragacanth. -Acacia may be further tested for with a solution of so1ut)le basic lead acetate, which gives a whitish gelatinous precipitate a n d again tested for b y t h e acid nitrate of mercury test in Group I 1 as already indica-
W A T E R - S O L ~ B L Es O L U T I O N S O F T H E G E L A T I N I Z I N G hCIEHTS
PASTY hf A T E R I A L S A N D T H I C K E N E R S Blue coloration indicates slarrh. (Sometimes green apples made into jelly will give traces of starch.) Purple coloration iridicates A mylo-dextrin. Red coloration indicates Erylhro-dextrin. iXo coloration may indicate neither starch nor dextrin. b u t may he Achtodextrin. Mixture. after shaking substance in solution with reagent is cloudy. Yellow precipitate with picric acid solution indicates Gelatine. Drop of this reagent. Gelatinous precipitate, soluble in excess of this reagent, indicates Acacia. X slight white cloudy precipitate may indicate either Agar-agar or Traga'aiilh o r both (test for tragacanth as in Group IV). A white gelatinous precipitate indicates either Agav-ago? or Acacia or both. C . T. Acacia will give a gelatinous, opaque white precipitate with solution basic lead acetate. Acacia may he further tested for as in Group I1 or Group IT' or by adding a solution of tannin which gives a bluish black coloration. A brownish yellow color on heating indicates Tvagacanlh. A white cloudy precipitate indicates Acuria. A slight turbidity may indicate Dexlvin. A white precipitate may indicate Albumen and Geluline. If a concentrated water solution of the unknown is treated with this reagent and placed on glass slide under microscope, a delicate framework of cupric pectate is evident. showing a Pectin of fruit or vegetable origin present.
t e d . The remaining tests in t h e other groups gi\-en in the table are rather well known, b u t t h e writer thinks t h a t this group method mill be helpful t o those interested in food chemistry. DIVISIOSOB FOOD A K D Dnnr,s BOARD OF IIEALTII, TOPEK.%
KAXSAS S T A T E
TAMARIND SYRUP By \V.
c.T a a E n '
Received March 2 5 , 1915
syrup prepared from the pulp of tamarinds with added sugar has come into use in the United States as a summer beverage t h a t is highly esteemed by Italians. Xfter dilution with water this syrup forms a refreshing drink. The making of this syrup apparently originated in Italy some years ago. The districts of Lombardy and Piedmont are the Italian sections most prominently identified v i t h the making of this product. The tamarinds used in this country are practically all imported. T h e y are t h e fruit of a leguminous tree, T a m a v i i i d u s i n d i r a , which grows in tropical and semi-tropical countries. A native probably of Africa, i t was early introduced into the East Indies. West Indies, Brazil, hiexico and most of the tropical countries. The fruit is a large, flat pod from 4 t o 8 in. long, filled with a n acid pulp, seeds and a stringy, fibrous matter. In t h e samples examined in this laboratory t h e pulp constituted about sixty per cent of t h e whole fresh fruit as removed from t h e pod. T h e reported analyses of tamarinds are not uniform. The statements in regard t o the presence of citric and malic acids are quite conflicting. Yauquelin,? who published one of the earliest analyses of tamarind, reported a large amount of citric acid as one of the constituents. This report can have little xeight as the method of identification was faulty. Xfter concentration, the addition of calcium carbonate produced a precipitate. which. on decsomposition, gave an acid precipitate with lime water. This n ~ o u l dnot be sufficient t o distinguish between tartaric acid and citric acid. 1
Assistant Chemist, Bureau of Chemistry. A n n . d e C h i m . . [ I ] 5 ( l i 9 0 ) , 92.
T H E J O L ' R N A L O F I - V D C S T R I A L .i.VD E I V G I ~ V E E R I N GC H E M I S T R Y
608
VOI.
j , SO.7
Schmey' quotes Nevinney, who found I . j t o 6 per used in making t h e syrups as outlined belowr, it may cent of tartaric acid and u p t o 9.4 per cent of citric. be doubted whether a sufficient amount of citric acid The methods of analyses used, however, are not given. would be extracted from the tamarinds t o gi1.e a test, hIueller2 reports the examination of nine samples taking it for granted t h a t it was present in t h e original of tamarind pulp freed f r o m seeds. He found a n aver- fruit t o t h e extent of 2 or 3 per cent. The fact t h a t t h e acidity was lower t h a n t h a t age of 2 , 2 per cent of citric acid, which figure included the malic acid which m a y have been present. found b y some analysts mentioned above may have Neumann3 found on t h e average f r o m t e n E a s t been due t o incomplete ripeness. Geerligs' has shown Indian, mostly Calcutta, and one West Indian variety t h a t t h e composition of the pulp varies with t h e different stages of ripening. I n a typical case t h e tartaric ;. 062 per cent of free tartaric acid, 3 . 0 5 per cent of citric acid, and 0 . 9 6 9 per cent of malic acid. acid content increased from 3 . 2 j t o I j .8 per cent during sixteen days of ripening, a n d the sugars from Adams4 reports no citric acid in t h e pulp. Octave Remeaud,j one of the more recent analysts, 0 . i 3 t o 1 5 . 2 Per cent. reports the results from t h e pulp of a known sample The manufacturing process employed in making of t h e fruit a n d from two commercial samples. His commercial tamarind syrups consists simply in makanalyses show a total acidity as tartaric of I I . 7 per ing a water extract of the tamarinds b y adding water cent on t h e known sample, largely due t o tartaric acid, t o t h e fruit. heating the mixture for a few hours, filwith a small amount of undetermined acid. His tering it, and adding sugar until a solid content of result on invert sugar is high, 4 2 . 3 0 per cent. approximately 60 per cent is obtained. There are, B ~ analyzed ~ twenty-one ~ ~ samples ~ of whole ~ G however, on t h e market artificial or imitation tamarind tamarinds f r o m c a l c u t t a , and one from t h e itlest syrups which are prepared from citric or tartaric Indies. and found on t h e average I , i 6 per cent of acids a n d colored with caramel t o give t h e product citric acid, with possible traces of malic in two cases, t h e appearance of a syrup containing a large amount of tamarind, and sometimes a small amount of t h e Tolman a n d MunF r o m analyses made b y Chace, tamarind may be added, varying from I t o j per cent. son7 some years ago, i t was seen again t h a t t h e fruit Glucpse is also added in some cases and other fruit in its natural state is remarkable for its large amount juices such as prune or raspberry. of sugar, over 30 per cent, which is mainly reducing The formulae used for making t h e true tamarind sugar, a n d for its high degree of acidity which t h e y syrup vary somewhat in t h e amount of fruit used, found t o be approximately I O per cent. I t has been some manufacturers .using a s much as 30 t o 3 j per stated b y P r a t t a n d del Rosaries t h a t the tamarind cent. I n t h e opinion of makers of high-class goods, contains more acid a n d more sugar t h a n any other tamarind syrup should be a preparation containing naturally occurring food. These authorss recently a sufficient amount of the extract of tamarind t o imreport t h e analysis of Philippine tamarinds in which part t o it t h e desired acidity a n d flavor. They apt h e total sugar as invert is 4 1 . 2 0 per cent, with less parently agree t h a t a t least 2 pounds of the whole t h a n I per cent of sucrose, and with a n acidity of I j .3 3 tamarind t o the gallon of t h e finished product, or apper cent as tartaric. proximately 2 0 per cent, is necessary t o impart the Other references t o the literature on tamarinds m a y distinctive flavor a n d t h e degree of acidity desired. be found in t h e article b y Brunner,l0 b u t t h e y are of Six syrups of tamarinds were prepared in t h e labolittle importance. ratory in t h e following manner: The published analyses agree fairly well a s t o t h e The pulp, separated from t h e seeds and other esamount of tartaric acid present, which is t h e charac- traneous matter, was used in making the estract. teristic acid of t h e fruit. The s u m of the potassium The amount of whole fruit was calculated from the t a r t r a t e a n d tartaric acid was found b y Brunner and pulp, which in this sample was 60 per cent of t h e whole Neumann t o be on t h e average I I . j per cent. hIueller fruit. The pulp was covered with water, placed on obtained a slightly higher figure on t h e pulp freed t h e steam b a t h for several hours, allowed to stand from seeds. oiTer night, filtered through a linen filter, a n d washed T h e fruit examined in this laboratory, which was with hot water. Sugar was added until the perpurchased in the New York market, had an acidity centage of solids was between jo a n d 60, a n d t h e soluof about I O per cent. calculated a s tartaric. A large tion finally filtered for analysis. The large amounts part of t h e acidity was due t o tartaric acid, as found of invert sugar present in Samples j and 6 may be b y t h e quantitative precipitation. and the rest t o accounted for b y the fact t h a t they were evaporated undetermined acids. N o citric acid was found in on t h e steam b a t h after the addition of sugar. t h e syrups made from this fruit, and volatile acids The table shows plainly the gradual increase with only in very small amounts. In x-iew of t h e method increasing amounts of fruit of t h e n o n s u g a r solids, I A l l g . M e d . Cenfr. Zfg., 66 (1896). 6 3 5 . solids other t h a n sugar and acids, acidity, total acid 2 Phurm. Centrafhalle. 23 (1882), 593. 8 Pharmaceuf., (1891). p. 15. as tartaric, ash, alkalinity of ash, phosphoric acid, Z L S .allg. desierrei'h. afiolh. \.ereitz, .\ug.. 1905. and color. The color in Samples j and 6 was increased 6 J . pharm. c h i n . , 23 (1906), 424. b y t h e evaporation of t h e syrup on the steam b a t h , 6 A p o t h . Z f g . , 6 (1891). 53. which resulted in caramelization. A subsequent samU. S . Dept. Agr., Bur. of Chem., Bull. 87 (1904), 1.5. Phil. J. .Sci., 8 (1913), Sec. A , h-0. I . ple of t h e same concentration as Sample 6 showed n 4
8
* Ibid.
'0
L O C . Lit.
1
Intern. Sugar J . , 10 (1908). 372.
.1 S D E S G I S E E RI S G C If E 311 ST R I'
color \-slue less t h a n one-half as much. The test of IIenig;7s'l reagent in t h e above samples did not indic j t e citric acid. While it may be questionable whether .%NIALYSIS OF T A M A R I N D S Y R T ' P S P R E P A R E D I N THE LABORA'CORV
Sample Sample Sample Sample Sample Sample 1 2 3 4 5 6
DETERMIS.%TIOS
.\mount of whole fruit 2.0 percent). . . . . . Total solids by refractometer (per cent). . . . . . 5 0 . 9 Reducing sugar before inversion (Der c e n t ) . . . . . . 4 . 1 Sucrose, G j j copper (per cent) . , . . .. . . . 45.6 'i-otal suear [Der c e n t ) . . . . 4 9 . 7 Son-sug& 'solids [per cent) . , .. 1.2 Solids other than sugar and acid (per c e n t ) . . . 1 . 0 8 Total acidity calculated as tartaric (per cent) , . . 0 . 1 2 .lcidity (cc. .Y 10 per 100 < i . .. 16.3 Tartaric acid; b y . wine method (per c e n t , . . . . .\sh (per cent) 0:O.r .llkalinity of ash ( c c . L Y 10 p e r 1 0 0 g . ). . . . . . . . . . 6 . 8 I'hosphoric acid (per cent) Trace Color in 1 2 in. cell ldeSrees Brewer's scale). . , 1 . 5 Citric acid. , . , . , , , , , . , S o n e
8 0
12 1
16 0
24 0
50.6
53.3
52.0
56 8
56.7
9.6
9 i
14.4
42 3
43.8
38.8 48.4
41 3 51 0
35 4 49.8
11 ,i
53.8
S.8 56.5
2 2
2.3
2 1
3.0
4 I
1 79
1.86
1.60
2 . I8
3.99
4 I
0.21 28.2
o'io
0.44 .i
