T H E J O UR-VAL OF I N D L S T R I A L AiYD ESGIIVEERING CHEAWISTR Y
l I a y , 1913
iodin number with the total fatty acids as determined by the official method as before outlined. Some one hundred and fifty samples were analyzed by both methods before the final selection of the factor was made. The follo~vingtable shows the closeness of the two mct hods. Sample number 2171 72 75 76 77 78
79 s1 R4 87 88 90
91 92 94
F. P. A. b y official method 43.39 40.70 47.35 46.70 49.34 47.13 46.51 48.48 51.52 49.30 46.67 47.45 19.31 47.03 49.29
So.
F. F. .A. by calculated for I S o .
53.53 50.90 58.6R 57.64 60.71 58.16 57.13 58.88 61.19 61 . O 47.34 50.66 61.48 58.16 61.19
4 3 . 17 41 . 0 5 47.32 16.48 48,96 46.90 46.07 47.48 47.31 49.20 38.18 47.31 49.58 46.90 49.35
Iodine
The above represented one day's work, and the results are typical of all work done. The three samples z 181-84-88,which show the greatest difference, were several weeks old a n d fermentation was in an advanced stage. The results showed t h a t t h e conversion factor could not be depended on if the soap stock was more than a week old, b u t as the whole purpose was t o obtain results as soon as possible after the refining was made, this was no serious objection. The six years' use has proven t h a t the method, as used, gave, on the whole, extremely satisfactory results, and i t has only received minor modifications, consisting in using special strength of sodium thiosulfate and iodin solution, so as t o simplify the calculation. SAVANNAHGEORGIA ~
T H E MODIFIED BABCOCK F O R FAT I N SWEETENED DAIRY PRODUCTS-ICE CREAM' B y J. 0.
HALVERSOX'
D I F F I C U L T I E S I S T E S T I K G SWEETEKE11 DAIRY PRODUCTS BY T H E B A B C O C K T E S T
The Babcock test is not applicable to sweetened dairy products on account of the charring action of the acid on the sugar. This causes a black charred mass t o rise in the neck of the test bottle. S o r can the &%dams-Soxhletmethod be depended upon as the sugar particles enclose fat.3 Leach3 overcomes this by pipetting off this solution containing sugar after precipitating the proteids with the fat by Fehling's copper sulfate solution. He then centrifuges in the cold. washes twice with water. The chances for errors are in thrice pipetting off the sugar solutions. Errors are also increased three-fold by multiplying the final reading by three. P a p e r presented at t h e Annual meeting of t h e American Chemical Society. Milwaukee. I f a r c h . 1913. A preliminary report was read a t the Washington meeting of the A. 0 . A. C., September 17, 1912. Formerly Deputy Food a n d Drug Commissioner, Acting Analyst, Missouri D e p a r t m e n t of Food a n d D r u g Inspection, Columbia, hfo. P a t e n t s dedicated t o t h e public are pendinc on the novel features of t h e test bottle described in this article. "-each, J . A m . Chem. S a c . , 1900, p , 5 8 9 .
403
Later, in 1900, Farrington' published a method of coagulating the proteids with small portions of 3 cc. of sulfuric acid. centrifuging a t 1000 revolutions for six minutes with the tester heated t o a temperature of z o o o F. This gathered the proteids with the fat into a firm lump. so the sugar solut.ion could be poured out the neck. Ten cc. of water are then added and the curd shaken up, 3 cc. of acid added and the process continued as above. After most of the sugar is removed. I O cc. of water are added and continued as in the Babcock test. These are the modified Babcock methods used to remove sugar from sweetened condensed milk. Where the per cent. of fat runs high, as in ice cream, these methods do not precipitate all the fat, part of which rises t o the surface. Hence these methods are inapplicable. GRAVIMETRIC . I S D
VOLUMETRIC
METHODS
IN
USE
O S
I C E CREAM
For ice cream gravimetric methods are used as the Roese-Gottlieb Extraction Method2 and Paul's Method.3 a combination of the Leach and the extraction method. The f a t obtained is finally weighed in both these methods. Of the volumetric methods, none remove the sugar entirely, b u t attempt to minimize its interference the most possible. Such a method is t h a t of Holm.$ This consists of a mixture of equal parts of glacial acetic and hydrochloric acid on a nine-gram sample. This acid used is less liable t o char the sugar. Howardj uses I O cc. of Fehling's Copper Sulphate Solution, shakes and centrifuges 3 minutes t o precipitate the proteids. First chloroform is added, which dissolves the fat. He then removes the supernatant liquor. The chloroform is then driven off by running in steam. The elimination of sugar in sweetened dairy products would make the Babcock test available as a rapid, easy method for the determination of fat. I t was thought if the sugar could be drained of after all the curd was practically dissolved b y the ordinary acid used in testing cream and after the fat was centrifuged t o the top, the E3abcock could still be used as a rapid volumetric method for determining fat in ice cream and other sweetened dairy products. I t mas observed t h a t in the Ehbcock method in testing ice cream, an appreciable interval of time elapses on adding sulfuric acid slowly before action on the sugar begins. This is the basis of the proposed Modified Babcock Method and the essential point in this method. The acid-sugar solution is readily drained o f f b y using a modified cream test bottle, which consists in fusing a small glass stopcock ( I mm. bore) on the side of a modified 6-inch 30 per cent cream test bottle. To drain off the acid containing the sugar, after centrifuging, equal parts of water and acid are added up to near the neck. Two minutes more centrifuging drives the fat and undissolved curd \Vis. E x p . Sta.. An,tuol R e p o r t , 1900, p p . 86-8'2. Lan+slr. V e r s . , 40, 1-27 (1892). a B u r . Chem., Circ. 90, p . 10. 4 Ann. Regort, State Food Corn.. Illinois. 1906. p . SO. j J . A m . Chem. Soc., 1907, 1622. 1
404
T H E J O U R N A L OF I N D U S T R I A L A Z i D l i " V E E R I N G
t o the top and the sugar is then drawn off by tilting the test bottle carefully, i t being held in the left hand. The test bottle was later modified to a h'/,-inch I j per cent cream bottle (see Fig. I ) , cspecialiy adapted for testing ice cream. This test bottle consists of a small glass stopcock ( I mm. bore) fused on thc lower part of the bottle a t an angle and placed at g o 0 to the right of t h r graduated readings. The graduation up t o "5 per cent is based on an 18-gram charge, oi which the smallest division reads to n quarter per cent.
1:io. I
Another modification t h a t suggested itself for use in the large International centriiuges or in ordinary Babcock testers for use in food control laboratories is a modified pear-shaped separatory funnel with a 2 j per cent graduated neck of an ice cream test bottie fused on the upper part and placed in trunnion collars or cups for centrifuging. A special excellent form of separatory funnel which
CNI:'MlSTRI'
Vo!.
j.
Ko.
j
can be modificd for this purpose is shown in Circular 2 0 2 , Uurimu of Animal Industry, U. S. Dept. of Agric., p. 3 . Fig. I , which would consist in a modified top by iusinx on thc graduated neck oS an ice cream bottle and its length changed to about onc-half t h a t given, to hold a corresponding volume of 45 cc. TO i i i ? T f n h i i r E P A T I N
(I
mzsn
: 5) C A K E
MILK
n-rm 2o
PER CENT
SUGAR .IDIlED
I t x a s thcn attempted to test sweet milk for f a t to which 2 0 per cent cane sugar had been added. This is the same proportion used in making ice cream. A few drops of Sormaldehyde wcrc added and the milk samples kcpt in the cooler. This was drsignatcd '' 23." The part of the same milk unsweetened was marked "A," The details of the modified method used are as Sollows: A churge of 1 7 . 6 cc. is taken to which is added 7 t o I O cc. of ordinary acid in small 3 cc. portions with shaking- with a slight pause after each. When the color of the mixture of milk and acid has been slowly built up to the color of coffee with cream in it (an amber-brown)' z to 3 cc. of cold water are added with shaking t o check the action. Centrifuge j minutes. Add hot water to near the ncck and whirl z minutes more. Then carcfully drain off the acid-sugar solution and again add acid in small portions till a coflec-black color is obtaiiicd (8 to I O cc. of acid is approximately required). Add hot wat,er up to near the neck and whirl 2 minutes more. ( S o precipitate will be kit if carcfully done and it will be unnecessary tri drain a second time.) Run the f a t into the neck with hot water. Whirl onc minute and read. The results are given in Table I Results from determinations r l l to q H were slightly low while t h e x s u l t s from determinations j R t o 8B were practically the same as in fresh milk. These fat columns were as clear as those attained in ordinary work with milk and cream except determinations j B to SB, inclusive, which each perfectly clean and clear in a set of four r,,n +ha C_jmO 'yL. '.>+~ 1 . 1 1" l Y i l . "
+"1i1.m a 11.
i)eterminations I~ to S B , inclusive, were read under standard conditions, t h a t is, in a hot water bath at ~ ~ also ??.ith "pl'rmoi. ....~ . ~ .dcd~ or - oj , and > d -. i!in,ita This latter is a white mineral oil used for removing the meniscus. ~~
1
Indiana Agticultural Experiment Station. E d . 146, P. 560.
T H E JOURi‘V‘AL OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
AfLly, I 9 1 3
TABLEI-SWEET MILK PLUS 20 PERCENT CASE SUGARADDED F a t in “ B ” Sweetened milk
F a t i n “A” r n s w e e t e n e d milk
Determination number
. . . 4 30 . . . . . 4.35 3.. . . . . . . . . . . . 4.40 4. . . . . . . . . . . . . . . . . . . 1. . . . . . . . 2. . . . . . . .
. . . . . . . . . . . . . . . 4.35 ..................... 4.20
I
.....................
4.4
. . . . . . . . . . . . . . . . . . . . . 4.4
8.
...................
4.4
Average. . . . . . . . . . . . . . . . . 4 . 3 5
RESIDUAL F A T LOST I S T H E P R O P O S E D T E S T
4.0 4 .O L O
It is known‘ t h a t 0 . 2 t o 0 . 3 per cent of fat is lost which never rises in the neck in the Babcock test of cream. To obtain the amount of fat thus lost, a n 18-gram charge of 18 per cent ice cream in this proposed method was undertaken. The acid-sugar solutions drained off were extracted for fat with waterfree ethyl ether. The results are given in Table 111. These were obtained by extracting with 40 cc. of anhydrous ethyl ether, extracting a. second time with 2 0 cc. A third extraction with I j cc. gave practically no fat (from I . 9 t o 3 mgs. with impurities) and so was discontinued. The ether was slowly distilled off from a small weighed Erlenmeyer flask on a water bath, dried in a steam oven and weighed t o constant weight. The fat was then dissolved out of the flask with several portions of petroleum ether boiling below 60’ C. The flask dried and the residue weighed t o constant weight, which consisted of a few milligrams of dark, charred or decomposed sugar products.
This indicated t h a t by carefully dissolving out the curd and removing the sugar, good tests can be obtained. C O M P A R IS 0 S ACETIC
0F ACID
PRO PO S E D AND
METHOD
WITH
ROESE-GOTTLIEB
well. This was not true of the glacial acetic acid method, which was discontinued.
3.9
4 .O 4.4 4.2 4.3 4.2 4.30
.*\-ernge. 5. 6.
GLACIAL
METHODS
By using the same method and manipulation on ice cream as above with the exception t h a t the action of the acid was checked w-ith j cc. of cold water, comparisons were made of the proposed method with the glacial acetic acid and the Roese-Gottlieb extraction methods. ,411 the ice cream tested from the determinations 94 a , b , and c. t o 99 a , b, c, and I O O c, were weighed out a t the same time from a carefully mixed lot of ice cream. They were then kept until they could be run.
TABLE111-RESIDUAL FATLOST I N DRAINED-OFF PORTIOS CHARGE I N 18 DETERMINATIOKS
Det. 90.
-
v
Charge Grams
-
-
-
Per cent. fat
cI__-
v
Charge Grams
Per cent. fat
Charge Grams
55’ C. 5 8 0 c. 17.6 b-18.0 16.4 c-4.000 17.2 b--18.0 l5,9.5 c-4.000 17.5 b-18.0 17.0 c-4.000 58‘ C. 9 7 . , lPAKISON O F PROPOSED > f O D I F I E D BABCOCK AND G L A C I ~ L ACETIC A C I D J I E T H O D WITH T H E ROESE-GOTTLIEB bfETHOD Glacial acetic Roese-Go ttlieh Modified Babcock method acid method method r
405
I
,
The‘ per cent residual fat lost varies from 0.103 to 0 . 3 3 2 excepting in determination 8 3 , Ti-hich is 0 . j 1 6
FIG.2-Showing t h e Modified Bahcock T e s t , Bottles. a n d Holder. The t e s t bottle t o t h e right shons a f a c t o r y control test. Bottom of f a t column dim, indicated by arrow
per cent, The amount of milligrams of fat lost varies from 1 8 , j to 5 9 , o and 9 3 . 0 , which one is considerable above the others. The average per cent residual 1
Indiana Agr. Exp. S t a . , Bull. 146, p . 5 i O .
T H E J O U R N A L OF I N D U S T R I A L A N D ENGIA’EERI-VG C H E M I S T R Y
406
fat drained off is 0 . z j 8 , which corresponds closely to t h a t lost in cream tests as found by Hunziker,I which averaged 0 . 2 8 per cent on 26 separate samples of cream.
to 50’ F., a t which temperature the cream rose to the top, upon standing. A study of this factor and of the non-uniformity of the ice cream itself, also of the method of mixing ice cream samples for taking charges after having been kept several days, is given in another article.’ I n brief, the results show t h a t not perfectly uniform charges can be obtained on such samples. This causes a slightly greater variation in the per cent of fat reading with a tendency to run somewhat lower. To eliminate this difficulty as much as possible, 18-gram charges were used. Especial care was also taken to thoroughly mix the samples before taking charges for testing.* A summary of the data is given in Table V.
R E S U L T S B Y T H E M O D I F I E D BABCOCK O N T H R E E S A M P L E S O F COMhIERCIAL I C E C R E A M
It has been found in preliminary work in Table I1 t h a t the results agree fairly well with the Gottlieb method. Next the proposed method was tried on three samples of ice cream made by different formulae, and which ran lower in fat. An attempt was made to obtain ice cream of medium to good quality averaging 1 2 t o 14 per cent butter fat: also some of poor quality containing 5 to I O pes cent fat. The fat readings were taken under standard conditions. The test bottles were placed in a water bath a t 54O-62 O C. for I j minutes, then read, using white mineral oil-glymolto eliminate the meniscus. This was done on all tests reported hereafter as ‘‘ standard readings.”
TABLE v-SAMPLE
TABLEIV---MODIFIEDBABCOCK.RESULTS ON 3 COMMERCIAL SAMPLES OF ICECREAM Det. h-0. 1
Sample No. 1 Per cent Det. fat No. 12.8 13 .O 13.2 13.2 13.1 13.0
1 2 3 4 5 6
Av., 6 13 . O S Max. variation 0 . 4
6
2
3 4
5 6
-_
Sample KO.2 Per cent fat 13.9 14.0 14.0 14.0 13.5 14.0
-.
13.90 0.5
Det. No. 1
4 5 6
SUMMARY O F RESULTS
OF
RESULTS
OF
Average . . . . . . . . . . . . . Low with calculated per c e n t . . . . . . . . . . . Maximum variation.. .
13
Mix A & B av. 23 detns..
...............
17.53 0.22
0.26
- 0.50
- 0.50
Low with calculated per cent f a t . . .
.......
...............
I t was found t h a t some variation was due to a n inability t o obtain uniform charges from the samples preserved with formalin and kept in a cooler a t 40’ 1 purdue
A p . Exp. Sta., Bull. 146, p . 570.
Mix
17.08 16.59 16.71 0.10 1.65 0.50
17.34 16.64 16.83 0.25 0.45 0.15
MIXES
COMPARED
KNOWN
THE
CENT
FAT BASED
CALCULATED PER CENT FATBASED ON
“E” not frozen
8
+
THE
BABCOCK
Mix “F” frozen
17.50
17.10
0 03 1 00
-
17.21
17.10
- 0.37
- 0.26
- 0.37
- 0.50
- 0.90
___
Xslix E & F, 18 detns..
10
-
...........................
0.90
17.16
Low with calculated per cent f a t . , . . . . . . . . . . . . . . . . . . 0 . 3 1
0.24
EFFECT O F SAMPLING
17.48 16.99 16.79 0.38 0.16 0.73
To obtain more accurate data, preliminary tests were run on known mixes of ice cream by weighing
17 S I
Determinations 3 to 6, inclusive, in sample No. 3 , show the greatest variation. The results are not as concordant. Difficulty of obtaining uniform charge on these determinations which were run a day or two later, was encountered. The effect of sampling or taking charges out of the sample a t various times was investigated.
Direct reading
30 lbs. cream a t 21 per cent 6 lhs. sugar 60 cc. vanilla extract
Mix “B” frozen
17.49
Standard reading
The following standard ice cream formula for a five-gallon mix was used throughout :
7.98 0.7
10
F a t by Modified Bahcock
O N T H E B A B C O C K TEST
__
FATFOUKD O N KNOWNMIXES, COMPARED WITH TESTO F CREAM
Mix “A” not frozen.
ON
RESULTS O X “SAMPLINQ”
Per cent fat RoeseGottlieh
W I T H T H E CALCULATED P E R
The tests were run a t once in quadruplicate on each sample except No. 3. Determinations I and z on sample KO.3 and all determinations on samples Nos. I and 2 gave concordant results with a maximum variation of 0 . 7 , 0 . 4 and 0 . 5 per cent, respectively. TABLEv I . - s U M M A R Y
SUXMARY OF
....
8.1 8.3 7.6 7.6 8.2 8.1
6
11/19/12
1st set, sampled a t once, a v . , 2nd set, sampled 1 week later, av. 3d set, sampled still later, a v . . . . Maximum variation, 1st set. . . . . Maximum variation, 2nd set.. . . . Maximum variation, 3rd s e t . . . . .
Sample No. 3 Per cent fat
2 3
Vol. .5> No. 5
them out in pounds on a creamery butter scales, as fnllows : Ibs. cream testing 3 8 . 8 and 39 . O : average per cent., 3 8 . 9 lbs. skim milk 0 . 8 3 3 lbs. sugar plus 2 9; cc. vanilla extract
2.7 2.5
__
6 033 Ibs. equivalent t o l i , 7 5 per cent butter f a t (calculated)
This mix was divided into two equal parts desig. nated “ A ” and “ B. ” Sample A was tested a t once while sample B was frozen the usual amount and tested to observe any difference. The results obtained by the Modified Babcwk test are 1
“Sampling Ice Cream,” THIS JOURVAL, 5, 409.
T H E JOI;R,'V'AL O F I S D C S T R I A L A N D Ez"\'GILYEERI~\'G C H E M I S T R Y
May, 1913
summarized in Table VI. The results from samples A and B being satisfactory, another known mix was weighed out in grams, as follows, on a laboratory balance sensitive to 0.01gram: Grams Cream a t 2 1 1 per c e n t . . . . . . . . . . 340 02 68.25 Sugar.. . . . . . . . . . . . . . . . . . . . . . . . . . . 2.295 Vuiilla e x t r a c t . , . . . . . . . . . . . . . . . .
~-
Total m i x . . . . . . . . . . . . . . . . . . . . . . .
410 57
equivalent t o 1 4 . 4 7 calculated per cent butter fat. This was divided into two parts, samples E and F. Sample F was frozen. Results are given in Tables V I and VI1 . TABLE
VII-SUMMARY
OF
is of more interest to practical ice cream makers), the per cent fat low for E and F was less, being 0.03 and -0.26, respectively. The rnaximum variation, however. is somewhat greater than with the standard reading. The maximum variation for A, B, E , and F varied from 0 ,j o t o 0 . 9 0 . The average per cent of fat tor a total of 41 determinations is 0 . 3 0 j low in comparison with the calculated per cent and has a maximum variation of 0.60. For the direct reading the average per cent of fat low is less by one-half t h a t of the standard reading (Table V I I ) , while t h e maximum variation is greater.
+
S U M M A R Y O F A V E R A G E S O F F A T B Y T H E M O D I F I E D 0.473-
TABLEVI
L o n with calculated per cent
Maximum variation
COCK
7-
Slix and No. of detns. Mix "A" ax.. X i x "B" a v . Mix "E" av. Mix "F" av.
13 detns . . 10 detns . . . 8 detns., , 10 d e t n s . . .
Standard reading 0.22 0.26 0.37 0.37
-
T o t a l detns.
41
....
....
fO.03 0.26
0.60
0.95
TABLEVIII-COMPARISON
0.145
THE
ROESE-GOTTLIER
SAMPLES
10/26/12,
MODIFIED
OF
BABCOCK WITH
METHOD O S SAMPLE10/'26/12 Modified Babcock. Detn. Standard Tu-0. reading 1. . . . . . . . . . . . . . . . . . . 1 4 . 0 2 . . . . . . . . . . . . . . . . . . . 14.28 3,. . . . . . . . . . . . . . . .. 4 . . . . . . . . . . . . . . 14.66
~-
__
0 . ,305
1.00 0.90
WITH
ON
11/19/12 A N D 11/0/12
.... ....
0.50 0.50 0.50 0.90
COMPARED
METHOD
S t a n d a r d Direct reading reading
Direct reading
407
The results of samples A and B are, on a n average of 13 determinations, 17.j3 per cent and from I O determinations 17.49 per cent, respectively. A and B compared with the calculated per cent I 7 . 7 j, are low, 0 . 22 and 0 . 2 6 per cent, respectively. 17 . j1 is the average per cent for t h e total 2 3 determinations. This is 0 . 2 4 per cent low with the calculated quantity of fat. On 8 determinations from sample E an average of 1 7 . I O per cent a n d on I O determinations, standard readings on sample F, also 1 7 .I O per cent were obtained. The direct readings in comparison with the standard readings were somewhat higher, being I 7 . j I and 1 7 . 2 I per cent, respectively, the calculated per cent being I 7.47. On a total of 18 determinations a n average of 17.16per cent or 0 . 3 1 per cent low with the calculated amount was obtained. The per cent fat low in comparison with the calculated per cent (see Table V I I ) on samples A, B, E , F was respectively 0 . 2 2 , 0 . 2 6 , 0.37, 0 . 3 7 . I t is important t o observe t h a t with the direct reading (which
Roese-Gottlieb method
Det. No. 1. .
, ,
.
.
,
.,
2. . . . . . . . . . 3. . . . . . . . . . . . . .
14.55 14.94
~
Averages.. . . . . . . . Maximum variation. . Low, per cent fat . . . .
14.75 0 3'2
14.31 0.66 0.44
Having obtained good results so far, it was determined t o check this method with the Roese-Gottlieb on three samples. The first. sample, 1 0 / 2 6 / 1 2 , is a preliminary mix compared with the Roese-Gottlieb method. By the proposed method, 14.31 per cent of fat is obtained from 3 determinations while with the RoeseGottlieb method this is 11.7 j per cent fat. The Modified Babcock runs 0.44 per cent low. The maximum variation for the Xodified Babcock and the RoeseGottlieb methods are, respectively, 0 . 6 6 and 0 . 3 9 per cent. Next two mixes were carefully weighed out on a laboratory balance sensitive t o 0 . 0 1 gram, as follows, numbered sample I I /9/12 :
Grams ' , A ,I
Cream at 2 0 . 5 per c e n t . , . . . . . . . . . . . . . 441.5 83.3 Sugar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 .O Vanilla e x t r a c t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calculated per c e n t b u t t e r f a t , 17.02 f o r 53 1 . 8 grams Koese-Gottlieb h l . per cent b u t t e r f a t , 17.03 on 3 deternlinations
TABLE
IX-sUMMARY
O F AVERACES 01:
1?.+T BY THIS > I O D I F I E n N A B C O C K
AKD
~-
Iioene-Go ttlieb _A
L
3
Sample No. 10/26/12.. . . . . . . . . . . Part"-%" . . . . . . . . . . . . . 11/9/12.. Part " H " . . . . . . . . . . 11/19/12 . . . . . . . . . . . . . . . . . . . . . . .
{
Average. . . . . . . . . . . . . . . . . . . . . . . .
i 2 3
3 3
c 3
c
14.75 17.03 l i 11 l i 48
COMPARED 11,/19/12
WITH T H E
ROESE-GOTTLIEB 11ETHOD
Proposed test low with K.-G.
Modified Babcock
O S SAMPLES
Calculated per cent. f a t
5
$
.7= : j
r
4 14 10 16 44
P
,g
4a 7r z
14.31 16.67 16.20 16.74
2 z i
> 8 .-e
2 2 -
-
.
e
4
..-
,
16.96 16.66 17.31
c
v
w
64.
.-
a1 f ;
+-
*
a % +
z
-
rn
0.44
..
0.36 0.91 0 74 ~ 0.60
0 07
0.45 0.17 _ 0.17
d
--
14.9 17.02 16.75 17.28
_
M a x . variaton
- -
Modified Babcock
2 :
::
SG
.?
,-_-_A_
;r:
+0.15 0.01 0.36 0.20
0.66 0.70 0.79 o 80
0.11
7
~
'Z 2 c:
__
441.5 83.3 . 2 7
10/26,'12, 1l/'q' 1 2
_~-_-A-_ _ _A. _.__ _ . A _ ?
d
;
Grams Cream at 2 0 . 2 per c e n t . . . . . . . . . . . . . . . . . . . . . . Sugar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vanilla e x t r a c t . . . . . . . . . . . . . . . Calculated per cent b u t t e r f a t 16 7 5 f o r 5 3 2 . 5 0 grams Koese-Gottlieb per c e n t , 1 7 . I1 on 3 determinations
"H"
5:::
,3
~
50
0 -
'-4.
a ,.
.... . . . 0 7.5
y z
0.39 0.02 0.03 0.35
408
T H E J O U R N A L OF I N D U S T R I A L A N D ElVGINEERING C H E M I S T R Y
Sample 11/19/12was taken directly from the freezer in the -University creamery room. The calculated per cent fat, the data showed, was 17.28; the per cent fat b y the Roese-Gottlieb from three determinations averaged I j . 4 8 ; the average per cent fat by the Modified Babcock on 16 determinations is 16.74. Thus from the summary (Table I X ) i t is seen t h a t the test runs low with the Roese-Gottlieb method from an average of 0 . 4 4 per cent t o 0 . 9 I in sample B, which was sampled after long standing. Also the variation in sample 11/19/12 was greater. I t is seen t h a t the maximum variation for t h e Roese-Gottlieb method is 0.39 and 0 . 8 0 per cent for the Modified Babcock, or twice as great. On the average of 44 determinations, the Modified Babcock runs 0.60 per cent low and b y the direct reading 0.23 per cent. The calculated reading here ran close t o the Roese-Gottlieb, an average of 0 . I I per cent low. PROPOSED MODIFIED BARCOCK METHOD I X DETAIL
To an 18-gram charge add the usual sulfuric acid sp. gr.) in small portions of 3 cc. a t a time, shaking after each addition with a slight pause. Continue adding acid in portions till a light amber-brown color or the color of coffee with cream in i t , is obtained. Stand a few moments. Then check the action of acid with 5 cc. of cold water with shaking. (This should be done before the solution becomes a deep dark brown or blackish color, which shows charring action on the sugar-which precipitate, if formed, is difficult t o dissolve.) The solution having the color of coffee with cream in it, centrifuge five minutes. Then add j cc. of boiling water, whirl one-half minute longer. Drain off the acid through the glass stopcock carefully b y tilting the bottle (approximately j cc. of solution will be left). Dilute with cold water up to I O cc., shake. Add acid in small portions as above, with shaking (approximately 8 t o I O cc.), till t h e remaining curd is dissolved or a n almost coffee-black color, as in testing milk, is obtained. Add 3 cc. excess of acid and shake. Whirl 4 minutes.' Dilute t o the neck with an acid solution (3 : j), 3 parts of the sulfuric acid t o j of water, C. a t a temperature of about 60'-70' Whirl one minute. Then add boiling water up t o zero or above and again whirl one minute more. Read the per cent of fat. ( I . 82-1.83
REMARKS ON THE METHOD
There were two obstacles which gave considerable difficulty in working out this method. One was a n occasional curdy or flocculent precipitate beneath the fat column. On dilution with hot water, i t was found t h a t a p a r t of t h e protein precipitated out and centrifuged into the neck as a flocculent precipitate. T o avoid this a n acid solution ( I : I) of sulfuric was This method in factory control can he considerably shortened after the first draining by whirling 4 minutes, then adding the dilute acid mixture up to zero or above. Whirl two minutes more and read directly. The variation in the per cent of fat is slightly greater or lower by a few tenths. 1
Vol. j, NO. 5
used for dilution instead of hot water, being mixed as needed. This solved this difficulty and prevented any precipitate from interfering. However, with this modification i t was noticed t h a t a t times an occasional test read high. I t was also observed t h a t this occurred when one-third or more of the lower p a r t of the fat column was emulsified. When this was less than one-third no appreciable error was observed. To overcome this difficulty, a weaker acid was necessary. An average of many determinations indicated t h a t a strength of 3 : j , three parts of sulfuric acid t o five of water, gave good results. This was too hot at times and then slightly emulsified the lower part of the fat column. Therefore, on mixing the acid used, it was dipped in cold water, stirring till 60' t o jjo C. was reached. This was used a t once and t h e test gave no further trouble, neither a flocculent precipitate nor an emulsified fat column. This test was worked out under such conditions that the color of the fat column was a light walnut, not a golden yellow, and b y following the directions this should be obtained. One hundred determinations were made in working out the preliminary test and a total of 350 tests in completing and substantiating the method. Commercial sulfuric acid, which was frequently used, gave no difficulty. A D. C. Electric twelve-bottle centrifuge of Creamery Package Mfg. Co. was used throughout. This tester was not electrically heated.
To keep the glass stopcocks from loosening, a rubber cement worked well. Caoutchouc was heated t o melting. This was used sparingly. SUMMARY I.
This is a rapid control method.
2 . Results consistent with the Roese-Gottlieb method are obtained, though averaging 0 . 6 per cent. low.
3. The per cent. residual fat lost in the drained portion averages the same as t h a t lost in cream testing. 4. The maximum variation of fat readings is not great considering t h a t the variation is somewhat greater on samples which have stood some time and hence are not perfectly uniform. The variation with the Modified Babcock compares favorably with the Roese-Gottlieb method. j . This method can be used in International centrifuges in food control laboratories if preferred, by using a separatory funnel with a graduated cream tube a t the top. This method is also applicable t o ice cream plants using the ordinary commercial sulfuric acid on hand. Likewise, a similarly modified ten per cent milk test bottle can be used for determining fat in sweetened condensed milk.
The author desires t o express his acknowledgments for advice and facilities to C. H. Eckles, Professor of Dairying, also t o Dr. P. F. Trowbridge, of the Department of Agricultural Chemistry, of the Univer-
May, 1 9 1 3
T H E J O U R N A L OF I N D U S T R I A L A N D EATGISEERI-VG C H E M I S T R Y
sity of Missouri, and t o Mr. 0. C. Smith, of the Experiment Station, for glassblowing. MISSOURIDEPARTMENT O F FOODA N D D R U GINSPECTION COLTJMBIA
SAMPLING ICE CREAM’ B y J . 0. HALVERSOS
I n a n investigation on the Modified Babcock” for testing sweetened dairy products, especially ice cream, considerable variation in the results for butter fat was a t times obtained. I t did not appear t h a t this was caused by the tests used as it was observed in both the hlodified Babcock and the Roese-Gottlieb methods. Thus i t was necessary t o investigate t h e factors which influence t h e per cept of milk fat obtained. These results are discussed in this paper. A good quality of ice cream, testing 16 t o 1 7 per cent fat, was used. This mas made in the University creamery room under the best of conditions. A fact of some importance is worth mentioning in this connection: A small amount (about a tablespoonful) of commercial ice cream powder (gum tragacanth in part) was used as a thickener in the formula for standard vanilla ice cream, given below. An intermittent Miller-Tyson Co.’s freezer, of capacity 2 0 gallons per hour, was used. This, in larger amounts, may have some effect in preventing the “churning” of fat in ice cream. However, this was not investigated. Formula for 5 gallon mix:
they obstructed the milk pipette. The freezer was examined after the day’s run. A considerable number of small lumps of churned butter forming a layer estimated at one-eighth t o three-sixteenths of an inch deep were found along the edges of the revolving paddles. This layer of small lumps of butter became more marked on the last batches frozen. These small particles of fat were more noticeable a t times in the frozen cream. Thus hot weather and old cream may be more favorable for their formation than cold winter weather. These factors. however, were not studied. EFFECT
OF
NOK-UIiIFORMITY O F T H E I C E CREAM
At all times t h e cream was carefully mixed, special care being taken t o prevent churning. All charges in each set in Table I were weighed out a t the same time. Occasionally some variation seemed due t o an unavoidable non-uniformity of the cream itself. A rich cream, as here worked viith, is liable t o churn t o a slight extent in the freezer and contain at times small lumps of butter: such were found. I n weighing out charges Paper presented a t the Annual Meeting of t h e American Chemical Society, Milwaukee, March, 1913. 2 “The Modified Babcock for F a t in Sweetened Dairy Products-Ice Cream,” THIS JOURNAL, 6 , 403.
TESTISG
CHARGES
TAKEN
T I M E S O N I C E CREAhI W H I C H H.kS
AT
DIFFEREKT
STOOD, A L L O W I S G
T H E CREXhI TO R I S E TO T H E T O P
Further work led t o the belief t h a t the charges were not uniform, due t o the inability t o thoroughly mix the samples after standing in the cooling rooms for several days. At the temperature of 4 0 ’ t o j o o F. in the cooling rooms on samples preserved with formalin, t h e cream in the ice-cream sample tended t o rise to the top. To uniformly mix the sample in order t o take charges for test.ing gave some difficulty. On sample 1 1 / 1 9 / 1 2 are shown the results of three sets of charges taken as follows (each of these was checked up b y the Roese-Gottlieb method). TABLE~.--“SAMPI.IXG”ICECREAM.
SAXPLE
11,’19/12
P a t by Modified Babcock m Fat Determination RoeseStandard Direct number Gottlieb rending rending
3 0 lhs. cream a t 21 per cent 6 Ibs. sugar 60 cc. vanilla e x t r a c t Small amount. ice cream powder
I n Table I , f a t readings in the Modified Babcock Method, taken a t 130’ t o 140’ F. with glymol, are designated ‘‘ standard readings,” while those taken a t once upon completing the test, are given as “direct readings.” Considerable variation in results at times obtained, may be caused b y a non-uniformity of the ice cream itself or poor mixing after having stood several days in the cooling room. This subject therefore divides itself into three parts: I . Non-uniformity of the ice cream itself. 2. Effect of testing charges taken a t different times on ice cream samples which have stood, allowing the cream t o rise t o the top. 3. Method of mixing ice cream samples after having stood some time.
409
.ri
First s e t . . . . . . . . .
3 15
r6 1 7 8
Second set
r Third s e t . . . . , . . . . . . .
17.70 17.56 17.32
... . . 17 . O i
16.91
19
... ...
‘0
16.45 17.13
16.75
... __
Average. Dets . . . . . 3--17 .OS> Maximum variation 1.25 1st s e t (sampled at once), av. 1 7 . 4 8 2d set (sampled 1 week later), a v . 16.99 3 d set (sampled still later), a v . . 16.79 0.38 Max. variation, 1st s e t . . , , . . . . . 0.16 X a x . variation, 2d s e t . . , . . . . . . 0.73 hlax. variation, 3d s e t . . . . . . . . . .
l i . 10 17.10 17.20 17 .oo 17 . O O 16.15 16.30 li.10 16.80 17 .oo 16.60 16.50 16.75
__
13-16.79 1 .05 17 18 16.59 16.71 0.10 1.65 0.50
17 30 17.35 17.50 17.25 17.30 16.25 16.30 17.25 16.85 16.85 16.80 16.75 1fi.90
__
13-16.94 1.25 17.34 16 64 16.83 0.25 0.45 0.15
First Set.-Determinations one t o five mere tested at once from the sample as the ice cream Fame from the freezer. Second Set.-Determinations 6 to 9 were taken I week later from the same sample, using particular care t o obtain as uniform charges as possible. Third Set.-Determinations I O t o 1 3 were charges taken still later and tested. From the averages and maximum variation on each set it will be seen t h a t when sampled at once the highest per cent of fat is obtained. Allsot h a t , in general, the variation on individual determinations was small while in the third set (determinations I O t o 13) i t is observed the average per cent of fat is lower b y both
