VOL. 5 (1951) ANALYTICA CHIMICA ACTA 63
DETERMINATION OF THE WATER CONTENT OF FOODS
III. THE DIRECT DETERMINATION OF TOTA& SOLIDS IN LIQUID SACCHARINE FOOD PRODUCTS AND
IN MEAT-CURING BRINES, ACCORDING TO JOSSE-BUYZE*
bY
D. A. A. MOSSEL AND S. L. WIT** Centrat InsCi1uf.e for NuLrition Research T.N.O., Ufracht (Nathsrlands)
INTRODUCTION
A convenient method for direct determination of total solids in aqueous sugar solutions has been proposed as early as 1893 by the French chemist Jossti. In this method the solution 1s absorbed by fiUev paper and easily desiccated after- wards since no essential retardation of desiccation due to crust formation’0 occurs. Although this technique has been applied in some instances w De a it never became very popular, probably due to the inconsistency of the results obtained by some worker& 7a 5.
The JossE-method to our opinion was considerably improved by BUYZE~
who proposed a special filter paper pile to prevent sticking of the paper. His pile consists of a central, folded cone, surrounded by a periferous, pleated cylinder; cf. Fig. I. Any liquid, not absorbed by the pile, is caught by two normal analytical filters, which are present below the pile proper.
This paper reports experiments carried out in this laboratory: i) with model substrata, to check the exactness of the method:
ii) with actual substrata, to study the suitability of-the method.
Mot&d subs&ala MATERIALS
A brine was prepared from sodium chloride A. R. and peptone (Difco, for bac- teriological purposes).
The sodium chloride was heated at 500~ C in an electric furnace to expel any occluded water. The peptone was dried for 72 h at 40~ C over P,O, in vacua ; rt did not loose an further weight on prolonged drying and therefore was considered as to be water- ree. Y
The anhydrous materials were dissolved in distilled water to give a solution, containing about ZOO/~ of NaCl and 0.5% of peptone! which corresponds to the average of data found in this laboratory when analyzmg meat-curing brines.
An artificial saccharine sap was prepared from dextrose A.R., levulose (Kahlbaum ;
+ For II see Anal. Chim. A&a, 3 (1949) 397. +* Student Research-fellow, Pharmaceutical Laboratory, Utrecht University.
References p. 67.
64 l.3. A. A. MOSSEL, S. L. WIT VOL. 5 (rgjjr)
“reinst. ftir analytische Zweckc”; and dehydrated Difco-peptone.
Ig42), potassium sulfate (desiccated at 500~ C) The materials were dissolved in distilled water to
give a solution, containmg about 20% of invert sugar, 2% of potassium sulfate and 0.5% of peptone. Since experience shows that very few levulose preparations are really pure, the solution was analysed for total reducing sugars according to the titrimetric LUIIZ~~-SCHOORL copper-reduction methodsa.
A liquid maif cxtvact was prepared from Difco dehydrated malt extract. The preparation was desiccated for 3 days at 40~ C over P,Q, in vacua, after which it did not loose alty further weight, and then dissolved rn distilled water to give a solution of about zoy&.
Actual substrata Fig. f
A coffee’extract, containing about 16&% of solids, was prepared in the following wa
K’ bout x50 g of commercially ground, roasted Africa coffee was moistened with water and then repeatedly percolated with about 300 ml of water in a steam-heated laboratory percolator (50 x 4 cm), The concentration of the total solids in the extract finally obtained was determined by recalculation of the d”: = 1.0660 with a standard tablet’.
A sample of commercial grenadine syvup (n$ = 1.44~8, corresponding to 60 % of solids) could not be desiccated as such, since its pH was 2.2, which should have induced serious caramcllisation reactions on drying. It was therefore partially neutralized with 0.5 N sodium hydroxide, until its - electrometrically controlled - pH was 6.8. The solution obtained was then diluted to about 20% of solids; in the calculation the Na added and H replaced were accounted for.
Refemnces p. 67.
VOL. 5 *(x951) WATER CONTENTS OF FOODS III 65
A sample of commercial orange syrup (ng = x.4364, solids = 58%; px = 2.2) was treated analogously until its pH was 6.6 and it contained about 200/~ of solids.
Samples of confectioned paars and ckerrias, containing about 70 O/O of total solids, = 4.2 and 3.7 resp., were hom*ogenized in
t:der adjustment of their pri to about 6.7, a Turmix-apparatus, diluted I to 4
and then treated as outlined above. A sample of commercial ComaLo puree was analyzed for pn, reducing sugars,
saccharose, levulosers, NaCIa, total solids (from ng = 1.3620 according to BIGBLOW*). and insoluble solids.
To determine the latter figure about 2 g of puree was diluted and hom*ogenized with xoo ml of distilled water and then centrifuged for IO’ at zooo r/min. The fairly clear serum was filtered over a tared oven-desiccated folded filter (0 = x5 cm) and the residue washed and centrifuged again until the liquid showed no Cl-reaction and no reduction when heated with the LurxGcHoonL-reagenti*. Then the residues were transferred to the filters previously used for filtering the sera, and dried to constant weight in a well ventilated standard oven at 102.5~ C. Insoluble solids . were calculated from the residue by subtracting 0.7% for water bound by the macromolecular dry substance s.
The data obtained are recorded in Table 1.
TABLE I
ANALYTICAL DATA OF TOMATO PUREE USI?D
invert sugar %
3.6 I r-3 I 9.8 I 0.7 I x.6
I 20.4 2.6
I I I I. I I
The 10% o P
uree was adjusted to PH = 6.6 in the usual way and then diluted to about solids, since a more concentrated dispersion could not be distributed evenly
over the filter paper pile.
METHOD
The BUYZE-#~X were prepared from folded filter papers (Whatman No, 12 or Schleicher & Schtill No. 588) of 0 = 15 cm and current circular filter papers of the same type. The flasks, equipped with the piles, were dried in a standard electric oven (65 x 45 x 45 cm) at an average temperature of 102.5X and an average absolute water vapour pressure of 10 mm Hg. They were closed in the oven when still hot and then transferred quickly to a desiccator in which calcium chloride was present. After cooling for exactly 30 mm they were weighed to 0.2 mg. Drying was continued until the weight changes noticed in consecutive weighings did not surpass 1.0 mg.
Over the piles, dried in this way, about 2 ml (in the case of diluted tomato puree: 5 ml) of the substrata were dispersed within I min with the help of a 5 ml-pipette. Moistening the pile was effected by applying one drop of the substratum to each of the vertical edges of the periferous cylinder and distributing
References p. 67.
66 D. A. A. MOSSEL. S. L. WIT VOL. s (xggr)
the rest evenly over the central cone. The flasks were then closed immediately and weighed quickly.
Drying was carried out as described for the tares. The time required for reaching “constant weight” (t,) was noted in every determination and from these data the average value c (in hours) was calculated.
RESULTS
The results obtained, when the model substrata were analyzed in two series of duplicates, are recorded in Table II.
TABLE II
DETERMINATION OF TOTAL SOLIDS IN MODEL SUBSTRATA
_ .-_ -
Substratum
Meat-curing brine Saccharine sap Malt extract
PH Total solids
cak?zted
6.6 I 8.2 6.0 x8.6 4.6 I 8.3
-^
Total solids ( JOSSE-BUY+
( %I ( 1 1
I I 2 3 4 1 Av 1 $1
I I I I I 18.2 18.2 I 8.2 18.2 18.2 3 18.5 18.6 ‘18.5 18.5 18.5 18.2 18.1 18.1 18.1 18.1 ::
-I ’ I
The results obtained with the actual substrata are presented in Table III
TABLE III
DETERMINATION OF TOTAL SOLIDS IN ACTUAL SUBSTRATA
Substratum
._-_
Coffee extract ’ 4.8 Grenadine syrup 6.8 Orange syrup Pears, confectioned ::; Cherries, confectioned 6.8 Tomato puree 6.6
-_-._
Total solids (from ng
or d'y ) calculated
( %! -
16.6 60.0
z;-‘: 7o:7 20.4
T- I-
Total solids ( JOSSE-BUYZE)
I I 2
~6.1 16.1 60.0 60.0 56.8 69.2 g;.y
69.7 6g:8 21.7 21.5
DISCUSSION
(%I
3 4
16.0 16.0 60.0 60.0 57-r 56.9 - - -
21.7 -
21.7
-
Av
16.1
60.0
g: 69:8
21.7
-
The replicates obtained by this technique are very satisfactory, thus confirniing BUYZE'S claim.
Rafsrmcas p. 67.
VOL. 5 (1951) WATER CONTENTS OF FOODS III 67
The correlation between calculated and found values for total solids is excellent as far as concerns the data obtained with model substrata. The correlation between calculated data and the values found in practice in commodilies, is satisfactory for the products, where total solids can be calculated with a high degree of cer- tainty from refractive indices, but, as can be exkcted, is poorer with substrata where the latter calculation is problematic, e.g. in tomato products.
SUMMARY
The filter-paper technique of Jossrz for determination of total solids in liquid food excel ent consistency, P
roducts poor in biocolloids, as recent1 when applied to synt K
modified by BUYZIZ, gives results of etic mixtures and to fruit syrups of
well-known composition. The time required for reaching constant weight of the residue varies from 2-5 (average 34) h at 100’ C.
RESUME
La technique dc JOSSE, a l’aide de papier filtre modifide recemment par Buuzrs,
F ur le dosage des solides dans les products alimentaires liquides, pauvres en biocol-
oldes donne d’excellents resultats dans le cas de melanges synthdtiques et de sirops de fruits de composition connue. Le temps necessaire pour obtenir un poids constant du residu varie de 2 ZL 5 heures (en moyenne 3&), B 100%.
ZUSAMMENFASSUNG
Die, kfirzlich von BUYZE abgesnderte, Jossrzsche Filtrierpa ier-Methode zur Bestixnmung des Gesamtgehaltes an festen Stoffen in flifssigen R ahrungsmitteln, die arm an Biokolloiden sind, gibt ausgezeichnet iibereinstimmende Resultate, wenn man sie auf synthetische Gemische und Fruchtsyrupe von bekannter Zusam- mensetzung anwendet. Die zur Erhaltung eines Ritckstandes von konstantem Gewicht benotigte Zeit betrlgt 2-5 (durchschnittlich 3* ) Stunden bei roo°C.
REFERENCES
1 W. D. BIGELOW UL al., Cited by: W. V. CRUESS, Commercial Fruif and Vagalabls Producls. 3rd Edition, New York, 1948. p. 448.
f H. G. BUYZE, Cirem. Waskblad, 46 (x950 342.
K W. EVANS AND W.R.FETZER, I&. B
4 ng. Ckm. Anal. Ed., 13 (x94x) 855.
*. W. GERRITSMA, J. H. VAN DE KAMER AND J. WILLEM&,, Chem. Wcskblad,
6 46 (1950) 2x3.
l L ._ JA GHIJSEN AND H. J. P..SUYXERBUYX,.
’ T. J.’ d
Chcm. Weekblad. 46 (1950) 474. OSSE, Bull. Assoc. Chrm. Suer. Dastall., IO (x893) 656. ITCHELL, J. Sci. Food and Agric., I (1950) 122.
l D. A. A. MOSSEL, Rec. Tyau. Chim., 6g (1950) 932. l PIEN ET H. MEINRATH, Ann. F&s. F~cawfcs, I (x938) 282. 10 : F. REITH, D. A. A. MOSSEL AND J. H. VAN DE k AMER. Anal. Chim. AC&, 2 (1~48)
359. 11 G. W. ROLFE AND G. DEFREN, J. Am. Chcm. SOL, I 8 (I 8~6) 86~. r* G. W. ROLFE AND W. A. FAXON, J. Am. Chum. SOL, IQ (18~7) 6~8. 18 N. SCHOORL, 2. Untarsuch. Leba*rsm., 57 (1929 14 A: THIEL, R. STROHECXER UND H. PATZSCH, 1
566. uschsnbych fJy die Lebensmiltel-
chcmis. Berlin, 1947. 1s F. TH. VAN VOORST, Anal. C/rim. Acta, 2 (1948) 813.
Received September 4th, 1950
