Chemical studies on the Freshnes of whale ·Meat III
Effect of Hydrogen-Ion Concentration on Decrease in Freshness
and Titration Curve of Whale Meat with HCI and Na2CO,

Tadashi Nakai
In order to find out the effect of pH on decrease in freshness of whale
meat, buffer solution of pH 2; 4.2; 5.9 and 7.7 was added to minced whale
meat and left standing for 144 hours at room temperature and the changes
in the quantity of volatile basic nitrogen and formal titrating nitrogen werestudied. At pH 2 and 4.2, it was observed that formal titrating nitrogenincreased slightly but volatile basic nitrogen showed almost no increase.
At pH 5.9 and 7.7, both nitrogens showed a very large increase. That is,decrease in freshness may be stopped at pH lower than 4.2, pH 4.2 is very
nearly the same as the growth limit pH of bacteria on the acidic side.
From this result, the author planned a storage experiment on whale
meat at pH outside the growth range of bacteria. However, Nakae1>
reports that, with the object of industrial treatment of sardine, he wassuccessful in preventing spoilage of sardine by storage at pH below 3.2 byFig.
1using HCl. HCl was used in
the author·s experiment andfirst of all, in order to find out
2
the required quantity of HCl,
2N HCl was used and titration
curve of whale meat was obtained (Fig. 1). At the same time,
titration curve by 2.N. Na"CO:iwas obtained because it wasnecessary for other experiment(Fig. 2). Samples in all cases
were baleen whale meat.

3pHiO

20

30

40

2.N HCI:cc per lOOg,of meat

Nakae2> obtained titration
curve with HCl on many kindsof fish and reports that general50
ly there is less buffer action

32

Tac!ashi Nakai
Fig.

between pH 6-4 and ap.pears strongly between the11pH 4-3 range. According
to the result obtained by
10
the author, .with whale
sample Illmeat, buffer action is weak9
between pH 2-3 2nd pH
5-7.7 range and appeared
pl:I
relatively strongly at otherparts. As can be ·observed
from Fig. 1, buffer capacity.
7
was somewhat small until
up pH of about 3, in Sample II which is high in fat
6~~~~~~..__~~_.__~~.....__~~_..,._.
010w
~w
00
content and low in other
2N Na,C03: cc per IOOg. of meat
constituents when compared with Sample I which has the opposite content of the various constituents.
Titration curve with HCl clearly indicates that it is composed of two
types of curves. For example, in the curve of Sample I · there is a curve
having an extension (A) and a curve with extension (B) and it shows that
there is a combination of both curve in between. That is, it is assumed
that curve (A) and curve (B) each indicates a separate reaction. Therefore, according to the graph, a reaction shown by curve (A) only takes
place up to pH of <:tbout 3.5, next, the reaction shown by curve (B) begins
and gradu'ally reaction of curve (A) diminishes and reaction of curve (B)only takes place at pH lower than 2.
The same can be said for Sample
II. Thus, it is very interesting to note that clearly, two reactions takes
place one after the other so it might be able to clarify a part of thechemistry of decrease in freshness by investigating this further.
If pH 3 is assumed to be the objective pH for storage, from the above
results, about 200 c.c. of 2N HCI will be required per 1 kg. of whale meat.
Thus, when a lump of whale meat is soaked in half its quantity of water
which also contains the .aforementioned percentage of HCl, removed after
5 days and boiled together with wat~r, decomposition of the fleshy partwas great and also, the meat had an acidic taste. Therefore, this method.}2Chemical studies on the Freshness of whale meat. III.

33

can be applied for studying the quantity of volatile basic nitrogen only
because actually it is accompanied by the aforementioned changes so it isinappropriate to apply this in practical cases.
Gratitude is expressed to Dr. Tsutomu Maruyama for his kind instructions and review, and appreciation is expressed to Mr. Ryusuke Fukazawa for his assistance in the expriment.
Experiment
Changes in volatile basic nitrogen and formol titrating nitrogen in whale
meat at time of adding buffer solution.
To 2 g. each of minced baleen whale meat 18 c.c. of buffer solution ofpH 2, 4.2 (mixed solution of HCl-NaAc); 5.9, 7.7 (mixed solution ofphosphate) was added and after standing for 144 hours at room temperaturein summer, 30 c.c. of absolute alcoholic N/100 HeS01 was added to stop
further changes and the following analysis made.
Volatile basic nitrogen- The above mixture is made slightly acidic,boiled mildly on a water bath to evaporate the alcohol and made to about
20 c.c., 1 g. of MgO added and as previously reported'1\ volatile basic substance was collected into N/50 H~S04 by the aeration method and titrated
back with N/50 NaOH.
Formol titrating nitrogen- The above mixture is made slightly acidic,
heated in a mildly boiling water bath for 15 minutes, drained off andwashed 3 times by heating for 5 minutes in water bath with 10 c.c. of
distilled water each time. I c.c. of 20% sulfosalicylic acid is added to thefiltrate and washing and left standing for one night. It is then filtered,washed, filtrate and washing made to 40 c.c. and 25 c.c. of this is titrated

by the usual method.
The result obtained was as follows :--- ·· ·----- - ···------·----·---~--VOfatile baslC Nfiiogell ____!____ ForffiOl-iltiatlllg NitrOgen___________________ ________ {~gj_lOOff.)_ ______ 1 _ _ _ _ (mg/100 g.) _ __Titration curve.
The sample whale meat were three kinds of baleen whale meat (frozen)
and their composition were as follows :Tadashi Nakai·34

Moisture
Crude Protein r
Crude Fat
Ash___
0·--··-----~--~%~o___ ,____,_%...___ _ ,___%~
o~______--2L___
72.65
21.48
3.97
1.02
Sample I
63.80
19.57
15.13
0.85
Sample II
76.89
20.70
1.65
0.95
Sample lil

Titration curve by HCI.
Samples I and II were used. These were minced with a meat grinder,
variable quantity of 2N HCl and distilled water added to 10 g. of mincedmeat and the total quantitiy made in to 20c.c. of slushy substance. It is left
standing for one night and pH determined with Yokogawa type antimonyelectrode hydrogen ion meter. However, pH of the sample with 0 c.c. HCI
added was determined one hour after addition of distilled water.
The following result was obtained. From this, the curve in Fig. 1
was obtained.
a)-------------------~-------------~----------··----

0 ' 2.05 i 4.11 i 6.16 _: 8.22 [ 10.27 12.3211 14.38 ' 16.45 18.49
2NHC1 (c.c. per lOOg. of meat)
ISample I
5.9
5.3 ! 4.9
4.5 • 4.3
4.o i 3.8
3.6 : 3.35 3.1
pH { Sample II
3.9 : 3.65 3.4 ! 3.15 3.05
6.2
5.3 : 4.9 ! 4.55 : 4.2-------------'-----:.!

1I·2N HCl (c.c. per lOOg. of meat)
Sample I
pH{ Sample TI

20.54
2.9
2.6

22.59
2.6
2.25

24.65
2.15
1.95

28.76
1.85
1.7

26.70
1.9
1.7

30.81
1.8
1.65

41.08
1.65
1.60. · b) Titration curve by Na2C03
Sample III .was used, treated in the same manner as a) and the followi11g result was obtained. From this, the curve in Fig. 2 was obtained.
-2N.Na2COs· (c.c. p er lOOg. of. meat)
pH (Sample ill)------- -2N Na2C0a(c.c. per lOOg. ofmeat)
pH (Sample III)

I'J

2.o

6.1

7.05

----------~-----

12II 14

6.0

8.0

7.85

8.05

8.3 l_~.6l 8.9 I 9.1

30

32

34

10.35 10.35 10.5

10.5

--I

10

---------------

24

26

10.05 10.1

10.2

: 22I

4.028I1) Nakae and co-workers:

36I

i_9·3~1-~-5~ 9.75
38 I 40

10.55 10.6

J. Fermentation Technology 21, 630, 6:t5 (1943).

3) This periodical No. 1, page 21.

i! 18 II 20.

References
2) Nakae: Ibid, 21, 661 (1943).

16J--I 50

10.7 110.85