Nov.. 1916
T H E .JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
m a y be easily worked t o a kind of cheese, in which a large p a r t of t h e wheat albumins are made available for human food. T h e process is in no wise restricted t o t h e use of wheat bran. Maize, peanuts, almonds a n d many other albumin-bearing seeds a n d oil cakes await their testing as t o t h e production of' palatable food. I n fact t h e r e is a variety which could never be attained b y t h e dairying industry working with cows' milk only. SNEFK, HOLLAND
THE DETERMINATION AND DISTRIBUTION OF MOISTURE IN BREAD By H. L. WESSLINC Received July 13, 1916
During t h e past few years t h e subject of t h e moisture content of bread has been receiving more a n d more attention. Excess of :moisture is considered much in t h e nature of adulteration a n d in certain quarters t h e advisability of fixing a definite standard for t h e water content of bread is being considered. I t will be necessary in t h a t event., however, t o arrive a t some understanding as t o t h e method of determining moisture in bread, since this is still a mooted question. Xccording t o Jago,l a thin slice should be t a k e n from t h e center of t h e loaf, t h e crust cut off a n d t h e interior portion crumbled, these crumbs thoroughly mixed a n d used for analysis. Neumann2 calls attention t o t h e fact t h a t t h e proportion of crust t o crumb, which varies with t h e size and form of t h e loaf, must be taken into consideration. He states t h a t t h e total water content of bread may be known only b y determining t h a t of crust a n d of crumb a n d finding the relation of crust t o 'crumb. Berman3 asserts t h a t t h e results are practically t h e same whether t h e moisture is determined on t h e crust a n d crumb together (direct method), or on these separately a n d t h e n calculated for t h e entire loaf (indirect method). He uses a wedge-shaped slice a n d takes into consideration t h e proportion of crust t o crumb. B o ~ t r o u x ,like ~ Jago, cuts a slice from t h e center of t h e loaf, trims off t h e crust, crumbles t h e interior a n d mixes these crumbs thoroughly. He goes farther, however, in t h a t he determines t h e moisture on crust a n d crumb separately. Boutroux also refers t o work done along this line b y Balland i n which he gives t h e water content of crust, of crumb a n d of t h e whole bread. Wiley6 uses t h e entire loaf, which he chops i n t o bits, weighs at once a n d dries until t h e bread is reduced to a small bulk. The dried bread is weighed a n d t h e loss of moisture d e t e r m h e d u p t o this point. This bread is t h e n ground fine a n d a further moisture determination made upon a sample thereof. A very rapid method for t h e determination of moist u r e in bread is t h a t described b y Wilh. Thornere and recently modified b y F. Schaffer.' I XVm. Jago and W. C. Jago, "The Technology of Bread-Making," 191 1 Edition, p. 834. * M. P. Neumann, "Brotgetreide u n d Brot," 1914, pp. 436-7. a "R'atergehalte van Wittebrood," Pharm. W t e k h l n d , 48, 675. L. Boutroux, "Le Pain et la Panification," 1897, p . 308. Bureau of Chemistry, B i ~ t ! 13, . P a r t 9 (1898), 1121 %. angew. Chem.. 2 1 (1908), 148. . l l i f t . Lebensm. Hyg., 6 ( l g l S ) , 6.
I021
These are really modifications of Hoffmann's method for t h e determination of moisture in hops,' a n d t h e principle underlying t h e m is similar t o t h a t used in t h e well-known Brown-Duvel moisture tester.2 ilccording t o Schaffer t h e loaf of bread is cut in two lengthwise a n d again in two crosswise; from every one of these four portions is cut a slice, from 0 . j t o I cm. in thickness, which is crumbled fine a n d these crumbs thoroughly mixed. Of this well-mixed material a 2 5 - g . sample is weighed off a n d distilled with 2 0 0 cc. of heavy petroleum. T h e water which distills over is collected in a graduated cylinder a n d t h e amount calculated t o I O O g. of bread. Schaffer refers t o t h e difficulty of getting a fair proportion of crust a n d crumb b u t suggests t h a t since t h e time requlred for t h e entire operation is comparatively short, two moisture determinations may easily be made a n d their average taken. For t h e purposes of t h e work described i n this paper, Schaffer's method of taking his sample, from t h e center of t h e loaf alone, does not meet our requirements. There is also much opportunity for loss of moisture b y evaporation during t h e operation of sampling a n d weighing. Finally, t h e difficulty of obtaining in a 2 5-8. sample t h e correct proportion of crust a n d crumb seems a decided objection. It is planned later t o make use of t h e Brown-Duvel moisture tester in determining t h e moisture in bread according to t h e suggestion of Schaffer, modifying his method of sampling t o meet t h e objections above stated. For t h e purpose of studying t h e variations in t h e moisture content in different parts of t h e same loaf this work was undertaken. The method used for t h e determination of moisture consists in weighing as quickly as possible in a t a r e d dish, on a torsion balance, t h e portion of bread selected. This bread is carefully heated a t a temperature not exceeding 60" until practically dry. The dried bread is t h e n allowed t o s t a n d exposed a t room temperat u r e for a few hours, in order t o let it come into equilibrium with t h e air. T h e loss i n moisture u p t o this point is t h e n determined. T h e air-dried bread is t h e n immediately ground t o a fine meal a n d t h e moist u r e on a 2 - 8 . sub-sample thereof determined i n t h e vacuum oven at t h e temperature of boiling water. From t h e per cent of additional moisture lost b y this sub-sample, t h a t of t h e entire sample is calculated and added t o t h e amount lost on heating a t 6 0 " . T h e combined loss gives t h e total percentage of moisture in t h e bread. This method is practically t h e same as t h a t described in Arbeiten aus denz Kaiserlichen Gesundheitsamk, 48 ( I ~ I S ) , 60j. Three loaves of different types, a n d differing in shape as well, were bought on t h e open market, all being approximately I O hrs. old a n d unwrapped. Sub-samples from a slice 2 in. thick, cut from t h e center of each loaf, were taken in t h e following order (see Fig. I ) : T ~ ~ Q C h S C h r&all . , 18 (1903). U S Dept Agr
, B. P I , LZYC. 72 (1910).
T H E J O r R L I T A LO F I N D C S T R I A L ALTD EIVGILVEERISG C H E M I S T R Y
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A-The crust proper trimmed off t h e entire slice. B-A section about 1/2 in. thick, next t o t h e crust. C-A second section 1;s in. thick. D-The innermost portion, in form of a cube.
The moisture was determined on every portion with the result,s shown in Table I : TABLEI-PERCEXTAGES
bIOISTURE I N P O R T I O N S O F A SLICE OF BREAD B C D Section next Section Inner KO. Crust t o crust .next cube 1. . . . . . . . . . . . . 25.50 40.78 42.98 42.60 2 ............. 18.79 32.27 38.42 38.69 3.. . . . . . . . . . . . 22.31 3 i . 57 41.70 41.67 OF
-4
Bread
Loaves similar t o the preceding mere then used t o determine how t h e moisture varies in slices taken from different portions of t h e loaf (see Fig. 11). These loaves were sampled as follows: .%-The end crust, about M in. thick. B-A slice immediately adjoining A and about 11s in. thick. C-A slice I/z in. thick c u t about half-way toward t h e center. D--A slice ‘/s in. thick directly from t h e center of t h e loaf.
The moisture content of every slice (crumb and crust together) was determined with the results shown in Table 11: TABLEII---PERCEiiTAGES
O F b1OISTURE IK DIFFERENT P A R T S OF COMMERCL4L BREAD5 .‘I B C D Bread Slice next Slice half-way Slice from ,TO. Crust to crust t o center center 1 . . . . . . . . . . . . 22.63 35.12 35.41 36.01 2. . . . . . . . . . . Z i . i 7 35.74 36.26 36.23 3. . . . . . . . . . l i , l l 30,GR 37.38 3i.i;
Having shown in this experiment t h a t t h e water content varies depending upon the section of t h e loaf from which a slice is c u t , the next step was t o determine t h e moisture of the loaf as a whole compared with t h a t of these slices Loaves of bread similar t o
FSG.
r
FIG.
I1
the preceding were used. These were cut in half and t h e moisture determined on slices cut from one half in a manner similar t o t h a t indicated in Fig. 11. The other half, E, was used entire, crust and crumb together, for a total moisture determination. These results are shown in Table 111: TABLE111-PERCENTAGIX
O F hfO1STURE I N DIFFERENTPARTS OF .4 L O A F BREAn COMPARED WITH TH.4T OF THE ENTIRELOAF A B C D E Bread Slice next Slice half- Slice from Half loaf No Crust to crust mav t o center center or total 37.70 37.45 35.14 1 . . . . . . . . . . . . 26.85 36.59 35.93 33.09 32.75 35.65 2 . . . . . . . . . . . 20.03 38.18 38.00 34.99 3.. . . . . . . . . . . 23.50 .35.32
OF
Yol. 8 No. 1 1
cated in Fig. I! moisture being determined on every portion. These results are shown in Table 11-: TABLEIV-PERCENTAGES
OF ~ I O I S T U IT RE PORTIONS OF .I I,OAF BREAD COMPARED WITH T H A T OF THE ENTIRE 1,OAF A B C D E F Section Section Inner Crust of Crumb of Total in Crust next crust next cube 1 4 loaf 1 ’ 5 loaf 111 loaf 26.84 39.72 43.10 43.08 29.18 41.44 77.17
OY
DISCUSSIOK OF RESULTS
I t is very el-ident t h a t t h e moisture content of t h e crumb varies considerably, depending upon its proximity t o the crust or t o t h e center of t h e loaf. I t might be supposed t h a t there would be a more or less regular increase in moisture as the sample approaches the actual center, b u t this does not seem t o be the case. I n fact, the results indicate t h a t there is no appreciable difference in moisture content in slices of bread taken a reasonable distance from t h c end of the loaf or in the crumb of any individual slice taken a reasonable distance from the crust. Therefore, after one gets fairly within the !oaf, it seems t o matter little whether t h e crumb be taken directly from t h e center of the loaf or not, since t h e variation is not great until rather near the end 01crust of t h e ].oaf. There is a great difference, hoxever, between t h e moisture in the whole bread (as det,ermined on one-half or one-yuarter of a loaf),‘ and t h a t in either the crust or crumb taken separately or in one entire slice. This shows t h a t in reporting the moisture content of bread it is necessary to stntc what portion of t h e bread was used. as well as how the moisture was determined. Another point that seems t o deserve attcntion is the age of t h e loaf. It is known t o every one t h a t bread loses moisture from the moment it leaves the oren. Consequently some idea of t h e freshness of the loaf should be given. When bread is baked in the laboratory it is usually weighed from I t o 2 hrs. after leaving the oven. When loaves are bought on t h e open market it is not always possible t o know honlong t h e time since baking, b u t this will almost always be less than 24 hrs. I n conclusion, t o determine t h e moisture i n bread use one-half or one-quarter of a loaf, depending upon the character of t h e crust, and follow t h e method described on page 1 0 2 1 . This is a far more simple as well as more accurate method t h a n t o find t h e proportion of crust t o crumb and t o determine the water content of each separately. LABORATORY OF PL.4NT CHEXISTRY BCREAUOF CHEMISTRY, WASHINGTON
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Xs a final experiment t h e moisture of t h e entire loaf as well as of different portions thereof was determined as follows: The loaf (which was a crust-covered one) was cut in half, and one half di\-ided into two quai.ters. T h e total moisture was determined on one quarter, and t h e moisture of the crust and of the crumb separately on t h e other quarter. From the remaining half loaf was cut a thick slice. as in our first experiment. and t h e different portions trimmed off as inrli-
A POLARISCOPIC DETERMINATION OF SUGAR I N
“CONDENSED MILK” B y R. 0. BROOKS Received September 20, 19!6
I n the legal analysis of “condensed milk,!’ two items are of paramount importance, vis.. t h e percentage of fat and t h e percentage of milk-solids. For the estima1 When t h e loaf is crust-covered, one quarter of i t , obtained by cutting t h e loaf in half crosswise and this half in two lengthwise, is sufficient t o represent t h e entire loaf. When t h e loaf lacks crust o n one side, by reason of having been baked in contact with another loaf, one half of t h e loaf is required for anal>-&.
