Carbon Dioxide in =Haddock=
ISH is one of the most perishable of all foodstuffs, and any method of retarding its deterioration is therefore of great economic importance. It has been known for more than fifty years that the action of bacteria upon flesh can be retarded by storage in an atmosphere of carbon dioxide. Not until recently, however, has any work been done in applying this fact t o the preservation of fish. Killeffer (6)in 1930 showed definitely that fish can be kept in better condition for longer periods when stored in the presence of this gas. Coyne discussed the action of carbon dioxide upon marine bacteria (2) and applied his results to the commercial handling of fish in England (3). Considerable experimental work has been done in Russia by Alekseieff (1) showing that carbon dioxide lengthens the period during which fish can be successfully stored. The present work was begun to determine the feasibility of using carbon dioxide in the handling and transBortation of fresh fish under commercial conditions obtaining in the United States. No attempt was made to investigate the mechanism of the action of carbon dioxide upon bacteria in retarding the spoilage of fish. I n order to restrict further the scope of the investigation, the work was confined to one species, the haddock (Melanogramrnw aegli$nus). Haddock is fairly representative of nonfatty fish and is caught in larger quantities in this country than any other species of this type of fish. Moreover, no attempt was made to apply the use of carbon dioxide to the preservation of fish on board fishing vessels. This is a separate problem and might form the basis of a future investigation. It was realized, however, that, during the relatively short time between the landing and the consumption of the fish, carbon dioxide might not
OF
be of sufficient value t o warrant its use. This project was begun primarily to settle this point.
Haddock Quality In order to compare the condition of fish stored in carbon dioxide with the condition of those in air, some criterion as to their quality must be used. In former investigations the organoleptic tests have been used almost exclusively, but other standards are desirable and for scientific research purposes are more appropriate. For example, in comparing the odors of two fish, not only do two different observers often disagree, but frequently the same observer will, from day to day, describe the same odor in a different way. Organoleptic tests give, a t the best, only a rough approximation as to the condition of the fish. Furthermore, as Reay (6) has pointed out, organoleptic tests are frequently deceptive when applied t o new methods of handling fish. In order to establish a scientific standard for the quality of a fish, two important factors must be considered: How much decomposition has taken place, and how rapidly will ensuing decomposition proceed? The first factor depends upon the presence of decomposition products already in the flesh and is best ascertained by means of a chemical test. The second factor depends not only upon the amount of deterioration already present but also upon the number of bacteria in the flesh; the larger the number of bacteria in the flesh, the faster the fish will decompose. A chemical test for decomposition in haddock was described by Stansby and Lemon (7). Griffiths and Stansby (4) have developed an arbitrary “freshness index” which takes into account both the decomposition of the fish and the number of bacteria present in the flesh. This freshness index has been used in the present work to
1452
Handling Fresh Fish MAURICE E. STANSBY
AND
FRANCIS P. GRIFFITHS
U. S. Bureau of Fisheries Technological Laboratory, Gloucester, Mass.
evaluate the benefit of a carbon dioxide atmosphere in the preservation of haddock.
History of Samples An interval of from a few hours to more than a week may elapse between the time haddock are caught and the time they are landed by the fishing vessel. For most haddock this interval averages about 5 days, although in a few cases the fish are landed on the same day that they are caught. I n the present project, some of the fish used were caught just outside Gloucester harbor and landed within 3 hours; the remainder were caught by otter trawlers off Georges Banks and landed after about 4 days. A portion of the latter lot was filleted, washed, and wrapped by the dealer in the regular commercial manner. I n both lots of fish the haddock had been eviscerated a t sea and were transported to the laboratory within 4 hours of the time of landing.
Storage Methods Coyne (3) has shown that any concentration of carbon dioxide between 20 and 100 per cent retards spoilage of fish, and that there is little difference between the results obtained in storing fish in various concentrations of the gas, although a slightly better retardation of spoilage occurred when 40 ~~
~
Whole haddock, stored in carbon dioxide from the time they are caught until they are unfit for food, keep approximately twice as long as those stored in air. Haddock which are just passing out of rigor m o r t i s are benefited if stored in the presence of carbon dioxide, a pronounced difference existing after 4-day storage in ice in favor of the gas-stored fish over those stored in air. Haddock which are in rigor m o r t i s are not greatly benefited by carbon dioxide storage, as long as rigor persists. Fillets maintained in a carbon dioxide atmosphere will be of better quality than those kept in air, especially after prolonged storage. If the best sanitary conditions are used during filleting, the use of carbon dioxide will be of the greatest benefit. The use of hypochlorite solutions will not offset careless handling of the fillets.
per cent carbon dioxide was used. In any simple application of carbon dioxide to the shipment of fish, no control of the exact concentration of the gas can be made, nor is this necessary, provided that, the concentration of the gas always exceeds 20 per cent. I n the present investigation a carbon dioxide atmosphere wa8 considered to be present when the concentration of the gas exceeded 25 per cent. Tests were run frequently to see that at, least this minimum was maintained.
Eviscerated fish were packed in wooden boxes or barrels. In the first trial, wooden, boxes, 16 X 24 X 40 inches, of the type used in shipping haddock were used for. storing the fish. Subsequent trials were made with the water-tight barrels such as are used in shipping mackerel. The latter, when covered with a burlap lid furnished with a moisture-proof coating on the lower side, were found to retain carbon dioxide for 2 to 3 days without replenishment The fish were kept well supplied with ice, and the carbon &oxide was applied in various manners. At first, attempts were made to apply the carbon dioxide in the solid form in an in-, sulated box placed at the top of, and inside of the barrel, in. such a way that the slow vaporization of the solid carbon di-. oxide would keep the barrel filled with the gas. Both cardboard and wooden boxes (the latter lined with insulation) were used but in each case the solid carbon dioxide vaporized very rapidly and had to be replenished frequently. The greatest success with whole fish was attained when the solid carbon dioxide was put into a vacuum bottle, and the latter placed on top of the ice in the barrel which was then covered with the burlap lid. The! vacuum bottle was tightly sto pered with a rubber stopper con-. taining a very small hole to alow the gaseous carbon dioxide to escape. An example of the length of time the solid carbon dioxide lasts when used in this way is given in Table I. The first column gives the number of days since the beginning of the run, the second column indicates the weight of the solid carbon dioxide added on the day indicated in column 1, the third column gives the weight of solid carbon dioxide remaining in the flask prior to the addition of the amount indicated in column 2. The last column shows the weight of solid carbon dioxide evaporating per 24 hours in the preceding interval. As shown in Table I, 2384 grams of solid carbon dioxide were used in 16 days. This is an average of 148 grams or about one-third pound per day. Table I also shows that 1 pound of solid carbon dioxide will last about 3 days. As long as any solid carbon dioxide remained in the flask! a carbon dioxide atmosphere was maintained in the barrel. Even after the last trace of solid carbon dioxide had evaporated, the barrels were found to hold the carbon dioxide gas for several days. The fillets were packed in gas-tight, one-gallon (3.79-liter) cans having a friction top lid. About 5 grams of solid carbon. dioxide were put into each can; when about 4.5 grams had vaporized, thereby replacing the air in the can with carbon dioxide, the lids were fastened in place and the cans packed in ice. I n this way a carbon dioxide atmosphere was maintained until the cans were opened. I n all cases the fish were kept completely surrounded by large quantities of ice, several times the amount ordinarily used in commercial practice. This minimized the chance of any temperature difference between the control and gasstored fish. The amount of solid carbon dioxide used was far too small to have any effect in this connection.
Procedure In each series the fmh were divided into two lots; one was, designated as the control and was packed in ice without any car-, 1453
INDUSTRIAL AND ENGINEERING CHEMISTRY
1454
VOL. 21, NO. 12
bon dioxide, and the other was stored with ice and gas as deTABLE I. RATEOF EVAPORATION OF SOLID CARBONDIOXIDE scribed. At regular intervals the barrels were opened, the fish or fillet was withdrawn, and the organoleptic tests were careSTORED IN A VACUUM BOTTLE fully compared. One fish or fillet from each barrel was laid aside Solid COa for the tests, the remainder was returned to the proper barrels Sohd COa So!id COa Evaporating per and re-iced, more carbon dioxide was applied, and the cover was Time Added to Flask Remaining in Flask 24 Hr. fastened in place. Each of the q-hole fish was then filleted, the Days Grams (Ounces) Grams (Ounces) Grams (Ounces) fillets were ground, samples were taken, and tests were made in the manner to be described. In this way it was possible t o fol.... 0 462 0 ... 2 0 (5.2) 168 147 low the progressive changes occurring in both the fish stored in 453 0 ... 3 air and in carbon dioxide. Moreover, a ready comparison of the 4 130 (4.'& 323 130 organoleptic tests was possible when the control fish and that 163 0 6 127 453 0 ... (. 5. ..7. ) 7 stored in the carbon dioxide were sampled simultaneously. .... 10 0 ... 453 Whole fish were washed in tap water, dried vith a clean cloth, 144 (5.1) 13 20 433 and filleted with a sterile knife, and the fillets were ground twice 0 ... .... 0 16 through a sterile meat grinder. The fillets were skinned and Total 2384 84 ground in the same way. Bacterial counts were made by weighing duplicate 5-gram samples of the ground haddock into 95 cc. of sterile saline solution, shaking 10 minutes in a mechanical shaker, and plating with agar media a t appropriate dilutions. TABLE11. ACCURACY OF B AND A VALUESIN PREDICTING The plates were incubated a t 25' C. for 3 to 5 days before countODORSOF HADDOCK ing. Five grams of the same ground fillet were used for the Sample No. Predicted Odor5 Obsvd. Odora 4bs. Error chemical freshness test. This test is executed by saturating a suspension of 5 grams of the fish in 100 cc. of water with quinhydrone and determining the amount of 0.0165 N hydrochloric acid required to bring the pH of this suspension to about 6, the number of cubic centimeters of acid being designated as B. The additional number of cubic centimeters of acid required to bring Series B the pH of the suspension to about 4.3 is designated as A . The larger the value of B , the more spoilage products there are in the 0.3 1.3 1.0 A flesh. The brger the value of A , the less protein has hydrolyzed. 0 1.0 B I 1.0 1.2 2.8 4.0 C I For a more complete description, the reader is referred to the 0.2 3.5 3.7 D I original paper of Stansby and Lemon ( 7 ) , from which the data 0.2 5.2 5.0 E 1 0 given in Table I1 are taken. 7.0 7.0 F I Pairs of fish or fillets were withdrawn from the barrels every Series C 3 or 4 days until the fish were judged to be entirely unfit for food. In this way one complete series would be made up of tests on four to seven pairs of fish or fillets. Seven such series were run as follows: Two series were run using whole haddock which had been caught not more than 3 hours before the first sample was taken, two series on whole haddock which had been caught about Series D 4 days before the first sample was taken, and three series of fillets prepared from the last lot of whole fish. One of the fillet series consisted of fillets prepared by the fish dealer in the regular commercial manner; a second series used the same commercial fillets which had been dipped for 2 minutes in a hypochlorite solution containing 40 p. p. m. of chlorine; and the third series Numerical scale of odors: 1 = fresh; 2 = fishy; 3 = sweet; 4 was-run on fillets prepared from the same lot of whole fish in the slightly stale; 5 = stale; 6 = very stale; 7 = putrid.
-
CHEMICAL AND BACTERIOLOGICAL DAT.4 FOR WHOLE
TABLE 111.
Sample No. A
TO
Odor Fresh
FRESHLY CAUGHT HADDOCK,
4 HOURSOUT OF WATERWHENOBTAINED ----Chemical
Days since Start of Run 0
3
PH 6.71
Tests A value
B value
Decompn. index (B A 30)
Series A Started April 25, 1933 24.4 7.6
- +
Bacteriological Tests Freshness Bacterial Index count per (B A 30 gram flesh Log bact. Log Bact.)
+- +
13.2
820
2.91
16.1
6.7 6.7
13.4 15.4
18,000 700
4.25 2.84
17.6 18.2
Fishy sweet Slightly sweet
6.85 6.78
23.3 21.3
11 11
Sweet Fresh
6 90 6.78
21.3 24.1
8 0 7.3
16.7 13.2
1,480,000 37,000
6.17 4.57
22.9 17.8
D I D I1
17 17
Extremely BM eet Slightly sweet
7.23 7.09
18.0 19.7
10 7 9.3
22.7 19.6
2,200,000 600,000
6.34 5.78
29.0 25.4
E1
21 21
Stale: sharp Very sweet
7.40 7.36
17.5 17.5
17 0 15.0
29.5 27.5
15,600,000 10,800,000
7.19 7.03
36.7 34.5
B I B I1
6 6
c I1
CI
E I1
Series B Started June 29, 1933 4
0
Fresh
6.85
30.1
8.2
8.1
1300
3.11
11.2
B I B I1
4 4
Fresh Fresh
6.78 6.78
23.5 21.8
5.7 6.0
12.2 14.2
10,000 12.000
4.0 4.08
16.2 18.3
C I c I1
8 8
Slightly stale Slightly sweet
6.77 6.72
22.4 24.8
6.1 5.7
13.7 10.9
15,000 2,000
4.18 3.30
17.9 14.2
D I D I1
12 12
Extremely sweet Slightly sweet
6.94 6.86
16.1 17.0
8.2 6.7
22.1 19.7
1,000,000 24,000
6.0 4.38
28.1 24.1
E I1
E1
16 16
Stale Sweet
7.14 7.11
13.7 18.3
10.0 9.0
26.3 20.7
12,000,000 420,000
7.08 5.62
33.4 26.3
F I F I1
19 19
Putrid Stale
7.41 7.19
14.8 16.3
12.2 7.4
27.4 21.1
4,800,000 160,000
6.68 5.20
34.2 26.3
G I1
25
Yeast-like
6.87
12.1
6.4
24.3
250,000
5.40
29.7
DECEMBER, 1935
k,
INDUSTRIAL AND ENGINEERING CHEMISTRY
white. This might be confused by some observers with the opacity of the eyes accompanying staleness in fish. It is actually an entirely distinct phenomenon and indicates nothing regarding the stage of decomposition of the fish. After about 3 weeks of storage in the gas, the skins of the whole haddock became extremely bleached; this is considered of no practical commercial importance, since the fish would rarely, if e\-er, remain this long in contact with the gas. The gills were observed in some cases to become brown more rapidly than in airdored fish. If carbon dioxide were to be generally adopted as a storage medium for fish, the consumer would have to be educated to distinguish these changes from the similar changes accompanying staleness in fish. The freshness index is repreqented by the formula:
GRAPH A
1'0
DAYS S l H C L DEATY
-
l,o
,ao
P
15
115
WHOLE H A D D O C K 4
c---
1453
DAYS
MIT OF
WATER
WHEN
B - A
,LO
,I5
DAYS KlNCE
DEATH
+ 30 + log bact.
OBTAINED
F I S U I N AIR
ODOR 5
4
SLIGHTLY
FRESH
I
STALE
FISH I N CARSONDIOXIDE
I 2
FlSHT
b
VERI
S
SWEET
7
PUTP I O
STALE STALE
FIGURE1. EFFECTOF C.~RBOX DIOXIDE ON THE KEEPIZG QUALITY OF WHOLE,ICEDHADDOCK
laboratory, using the most sanitary conditions possible. The purpose of running the three fillet series Tvas to show the effect of using special precautions in preparing fillets. It was hoped that, by dipping the commercial fillets in a hypochlorite solution, the contamination caused by careless handling during filleting by the dealer might be reduced so that the quality of the fillets would approach that of those prepared under the most sanitary conditions in the laboratory. Beginning about the third day after storage, the haddock stored in gas were not'iceably in better condition than those packed in ice alone. After a week or more, the difference was very evident. In most cases the fish were examined by four or five disinterested persons who knew nothing of the history of the fish, and almost invariably the gas-stored fish was chosen as being in better condition than the corresponding control fish stored in ice and air. I n addition to the observed action of carbon dioxide retarding spoilage, three other effects were noticed. After about 3 days in the gas the eyes of the haddock became noticeably TABLE11'. Sample KO.
A A'
CHElliICAL A N D
?ass since Start of Run
TISH
I
IN ~ ' I G O R WHEN L ~ N D E D F I S H
OUT o r
a i ~ o WHEW i
LANDED
FIGURE2. COSDITIOX OF WHOLEHADDOCK 4 DAYSAFTER L ~ N D I N G
BACTERIOLOGICAL DATAFOR HADDOCK, C A C G H T 4 DAYSJ v H E N OBTAINED Chemical Tests Decompn. .1 B Index PH value value ( B - A f 30) Series C Started August 15, 1933a
7-
Odor
Bacteriological Testa Bacterial count per gram flesh Log bact.
Freshness Index
+
(B - 9 30 Log Bact.)
+
0
Slightly sweet Sweet
6.7s 6 82
24.6 24.0
7.8 8.0
13.2 14.0
40,000 17,000
4.60 4.23
17.8 18.2
B I1
3 3
Sweet Sweet
6.94 6.70
23.2 24.2
9.8 5.4
16.6 11.2
460,000 210,000
5.66 5.32
22.3 16.5
C I c I1
7
7
Stale Very sweet
7.00 6.92
21.5 21.3
7.8 5.0
16.3 13.7
230,000 34,000
5.36 4.53
21.7 18.2
D I D I1
12 12
Stale Yery stale
7.09 7.12
14.2 13.8
9.8 9.8
25.6 25.0
2,000.000 2,200,000
6.30 6.34
31.9 32 3
BI
'/l
Seriea D Started August 15, 1933
a
A
0
Fresh
6.71
25.6
6.7
11.1
80,000
4.90
16.0
B I B I1
4 4
Fresh Fresh
6.65 6.60
19.5 23.9
5.8
5.7
16.3 11.8
560,000
5.75 3.94
22 0 15.7
CI c I1
13 13
Stale Stale
7.04 6.94
14.8 18.2
7.2 5.8
22 4 17.6
7,600,000 100,000
6.88 5.00
29.3 22.6
D I D I1
16 16
Putrid Cheese-like
6.92 6.87
16.4 16.5
6.0
8.8
22.4 19.5
9,000,000 320,000
6.96 5.50
29.4 25.0
.....
..
..
5
E1 21 Putrid 7.41 10.3 11.3 31 0 This lot of fish was believed not to have been handled properls before reaching the laboratory.
8800
VOL. 27, NO. 12
INDUSTRIAL AND ENGINEERING CHEMISTRY
1456
CHEMICAL AND BACTERIOLOQICAL DATAON HADDOCK FILLETS PREPARED FROM FISH4 DAYSOUT OF WATER
TABLE V. Sample NO.
Days since Start of Run
Chemical Tests
7
Odor
A value
PH
B
value
Bacteriological Tests Bacterial count per gram flesh Log bact.
Decompn. Index (B A 30)
- +
Freahnesa Index (B - A 30 Log Bact.)
+
+
Series E, Commercial Fillets Started August 15, 1933
A
0
Slightly sweet
6.66
26.7
5.8
9.1
400,000
5.60
14.7
B I B 11
3 3
Sweet; fiahy Sweet
6.61 6.65
22.2 23.6
4.2 4.1
12.0 10.5
1,000,000 460,000
6.00 5.66
18.0 16.2
C I c I1
7 7
Slightly stale Sweet
6.90 6.80
18.0 21.3
9.4 9.7
21.4 18.4
23,000,000 1,300,000
7.36 6.11
28.8 24.5
D I D I1
10 10
Putrid Stale
7.00 6.94
16.0 18.0
17.3 7.9
31.3 19.9
4,000,000 440,000
6.60 5.64
37.9 25.5
E1 E I1
14 14
Very stale Very stale
.. ..
20.8 19.2
9.0 13.8
18.2 24.6
9,600,000 180,000
6.98 5.26
25.2 29.9
F I F I1
17 17
Putrid Very stale
7.16 7.07
16.8 19.0
11.5 12.4
24.7 23.4
....
.. *.
..... .....
Seriea F, Commercial Fillets Treated with Hypochlorite Solution, Started .4ugust 15, 1933
A
0
Slightly sweet
6.73
22.3
5.0
12.7
500,000
5.70
18.4
B I B I1
3 3
Fishy Sweet
6.65 6.66
20.6 19.9
4.9 6.0
14.3 16.1
830,000 180,000
5.92 5.26
20.2 21.4
CI c I1
7 7
Stale Sweet
6.94 6.85
21.1 21.2
9.5 8.5
18.4 17.3
3,700,000 440.000
6.S7
5.64
25.0 22.9
D I1
D I
10 10
Stale Stale
7.00 7.07
17.2 21.6
11.8 12.4
24.6 20.8
1,800,000 560,000
6.26 5.75
30.9 26.6
E1 E I1
14 14
Very stale Very stale
... .
19.0 17.2
12.0 10.8
23.0 23.6
54,000,000 500,000
7.73 5.70
30.7 29.3
F I
17 17
Very stale Very stale
7.00 7.02
18.8 22.1
10.2 11.5
21.4 19.4
..... .....
.. ..
*.
F I1
..
Series G, Fillets Prepared in Laboratory, Started August 15, 1933
A
0
Fresh
6.71
25.6
6.7
11.1
80,000
4.90
16.0
B I B I1
3 3
Slightly sweet Rresh
6.60 6.66
24.6 22.9
5.7 6.3
11.1 13.4
330,000 100,000
5.52 5.00
16.6 18.4
CI c I1
7 7
Stale Sweet
6.77 6.56
21.2 24.0
8.8 4.6
17.6 10.6
9,000,000 240,000
6.96 5.38
24.6 16.0
D I D I1
10 10
Very stale Stale
7.26 6.90
18.8 23.4
14.4 10.7
25.6 17.3
160,000,000 360,000
8.20 5.56
33.8 22.9
E1 E I1
14 14
Very stale Very stale
.. ..
19.3 19.5
15 2 14.2
25.9 24.7
9,600,000 180,000
8.98 5.26
32.9 30.0
F I F I1
17 17
Very stale Very stale
7.11 7.02
19.5 24.4
12.5 13.4
23.0 19.0
where B and A
=
log bact.
=
chemical values described by Stansby and Lemon ( 7 ) logarithm of bacterial count per gram of fish flesh
This freshness index is more or less proportional to the quality of the fish, values of ten to twenty corresponding to fish of fairly high quality, whereas fish in which considerable decomposition is present give values of thirty or more. Chemical
K -40
-
2
-30
-a0
gb
Cn
0
i
-lo
....
and bacterial data of the seven runs are tabulated in Tables 111, IV, and V. The first fish in each series has been designated by the letter A while each succeeding pair of fish or fillets was numbered B I and B 11, C I and C 11, etc. T h e number I refers to the control fish stored in ice in the ordinary manner, and I1 denotes the fish stored in carbon dioxide and packed in ice. The freshness index was plotted against the time elapsed since the fish was caught (Figure 1). I n addition, a symbol was inserted a t each point on the graph to indicate the approximate degree of odor of the fish. The odors are not entirely consistent with the freshness index values. This is due not so much to the inaccuracies of the organoleptic tests as to the fact that the freshness index includes also another factor (bacterial count) which, as has been pointed out, partially determines the quality of the fish by predicting how much longer it will keep. The fish represented in graph A were packed in boxes which were not gas-tight, so that an atmosphere of carbon dioxide was present only part of the time; consequently there is not a great deal of difference between the control fish and those stored in the gas.
3
Discussion of Results Figure 1 ( A and B ) shows that for the first 5 or 6 days there is little or no difference between the control and gasstored fish. After the first week of storage, a very preceptible difference in favor of the fish stored in carbon dioxide occurs. I n graph B where a carbon dioxide atmosphere was main-.
0
IS
SINCE
..* .
0
W
DAYS
..... .....
DEATH
OF Rigor mortis ON BACTERIAL COUNT FIGURE 3. INFLUENCE AND DECOMPOSITION OF FISH
tained continuoualy, tlie fis!~stored in the gas kept approximately twice as long aE t h e in air. Thus it took only 13 days for the air-stored 6811 to reach a freshness index of 30; those stored in carhon dioxide had a corrcspondiug value of 29.5 after 25 days. Graphs C and D,repre.sonting whole fish which werc 4 days out of tiie water when obtained, show a corrsiderable difference between tiie control fish and those stored in carbon dioxide, during the first 6 days after the fish were obtnincd. Toward the end of each series the condition !if the gas-stored and control fish is nearly the same. Moreover, graphs C arid D show that tire series represented in the latter were ilk better condition initially than those in the former, and that there was a greater differeme between the gas-stored and control fish at the end of tlre run in the former series than in the latter. On the average, ahout 4 days elapse hetwveeri t.he time wide haddock are landed and the time they reach the consumer, and in this interval carbon dioxide can most easily be used as a storage medium. Figure 2 represents the condition of haddock 4 days after landing. The fish which were about 4 davs out of the water when the zas w&3 first aunlied .. show the &atest benefit. The fact t,hat carbon dioxide is of little value durina the first few days after the f i 4 have been cauglrt, is explained by the
Jut. that during this period tiie fish are in rigtir mortis.' In a larger nuinher of cases in connection with this and other proj-
ects it has been observed that as long as tlie fish remain in rigisor m,ortis, the bacterial count dnes not rise significantly, :urd deermposit,ion proceeds at an imperceptible rate. Figure :I slrows one such instance. The iIlitial drop of the decomposition index is cristoniary, since it is due t,o an increase in
'FiRLE VI. KEEPWQQUALITIES OF FILLETS, PREPARED IN V \RIOUS WkUS, STORED IN Arn OR CARBON DIOXIDE, Ah'D KEPT
IN ICE
D a m of Storage to Reaeh a F r e d neea Index of:
Order According t o Keening QudituI%we d filleting
Speoisl trestrnent
Method of atorage
I"
22-
30b
cot
A value caused by rigor mortis. No rise in bacterial count or decomposition occurs until after rigor mortis has passed. It is not to be expected, therefore, that an atmosphere of carbon dioxide (%,hi& retards decomposition by reducing bacterial growth and action) would be of any great benefit as long as tire fish remaills in rigor mortis. Most haddock or otiier ground fish are no lmigcr in rigor morf.6 when landed. Such fish would be benefited considerably if kept in a carbon dioxide atmosphere until sold, especially if no marked decomposition were present when t.he gas was first applied. A
BOXES OF
FISH ! h A D Y
FOR SHIPMEYT AT
FULTONMARKET,NE\\
YORK
I Tim term r i v m rnoiiia is used in tkia pmr io the broader ~ e n mto include not o n l y the peiiod when t.he fiali i~ extremely a t i t but ~ 1 8 0the accorn~any i i l ~dienomenn sircb RB the gelntinoua state at the flesh, the fall in PH of tlre flesh. eto. Thin neriod ordiirsrily In& for from 2 to 4 d e n
INDUSTRIAL AND ENGINEERING CHEMISTRY
1458
few fish are landed, h o w e v e r , a few hours after they a r e c a u g h t and when they are just entering rigor mortis; these fish might remain in rigor until sold to the consumer so that a carbon d i o x i d e atmosphere would be of uncertain value. The results of the fillet series were graphed in the same way as the whole-fish series. Table VI shows the difference in these series more clearly. When the freshness index is 22 or leds, the condition of the fish is still quite good; and when it reaches 30, the fish are barely edible. The number of days required for this value to reach 22 and 30 has been calculated for the various series and t a b u l a t e d in Table V I in the order of their keeping q u a l i t i e s . Table V I shows that all three series of fillets stored in a carbon dioxide atmosphere kept better than the three in air. iMoreover, the fillets prepared in the laboratory kept much better than
VOL. 27, NO. 12 those prepared by the fish dealer. This was especially marked in the series kept in the carbon dioxide. Some of these results are depicted in Figure 4. These experiments show that the utmost care must be taken in preparing fillets if the products are to be kept for t h e maximum length of time.
Literature Cited (1) illekseieff, P. 8., Intern. Bull. Inf o r m a t i o n Refrigeration, 1934, RQ.?
(2) Coyne, F. P., J . SOC.Chem. Ind., 51, 119T (1932). (3) Ibid., 52, 19T (1933). (4) Griffiths. F.P..and Stansbu, M .E.. Trans. Am. Fisheries Soc., 64, 401 (1934).
(5) Killeffer, D.H., IND. ENG. CHEM., 22, 140 (1930). (6) Reay, G.A, J . SOC.Chem. Ind., 54, 145 (1935).
I
I
I I L L C T S PREPARED TREATED COMMERCIAL UNTREATEOCOMHEICIAL IN LABORATORY FILLETS FILLETS
FIGURE 4. EFFECTOF STORAGE IN CARBON OF HADDOCK DIOXIDEUPOX KEEPINGQUALITY FILLETS PREPARED IN VARIOUS WAYS
(7) Stansby, M. E., and Lemon, J. M., IND.ESG. CHEM.,Anal. Ed., 5, 208 (1933). RECEIVED iMay 24, 1935. Published with t h e permission of the Commissioner, U. S. Bureau of Fisheries.
Extraction of Pectin from
Apple Thinnings H. W. GERRITZ
College of Agriculture and Experiment Station, The State College of Washington, Pullman, Wash.
STIMATES have been made that 10 per cent by volume of the total apple crop is lost each year as June drop and thinnings. This immature fruit contains large quantities of pectinyielding material which is referred to by Fremy (3) as pecSOCIETYnomenclature tose and by the A M E R I C - ~ NCHEMICAL ( I ) as protopectin. B y treating this immature fruit with 0.5 per cent hydrochloric, sulfuric, or tartaric acid, a large portion of the insoluble pectic substance is converted to soluble pectin of good gelling quality.
Experimental Procedure Rome Beauty and Jonathan ap les thinned from trees in the Yakima valley about the middle ofJune and others thinned from trees at Pullman about the middle of July were picked off the ground for use in the experiment. The apples were wei hed and washed, then ground, sliced, or frozen, and different met%ods of extraction were employed. The plan of each extraction was to obtain a yield of good-quality pectin of such nature that by filtering and concentrating, a liquid pectin sufficiently pure for jelly
ma Ing would be obtaine The jelling strength of the pectin solution was determined by Rooker’s method ( 4 ) ,and crude pectin in the extract was determined according to official methods (9) except that no allowance was made for ash. Since Rooker’s method gives the direct gelling value, rather than chemical pectin content, it offers the more valuable information to jelly manufacturers. (Rooker considers a pectin solution to contain 100 units when 100 grams of solution containing 0.41 gram of lactic acid will gel 100 grams of sugar in 24 hours to give a firm gel weighing 165 grams.) Apple thinnings were ground through a food chopper and suspended in hot water. The filtered press juice contained almost no pectin as indicated by gelling tests. Boiling in an open kettle gave similar results. Ground pressed thinnings heated to 15-20 pounds per square inch (1.1-1.5 kg. per sq. cm.) pressure in an autoclave gave a brown press liquor of no gelling value. Allowing this mixture to stand for several days did not increase its gelling power. Heating the thinnings with very dilute solutions (approximately 0.1 per cent) of h drochloric, sulfuric, or citric acid, as used for extracting pectin $om ripe apple pomace, was unsuccessful with these thinnings. When, however, ground or sliced apple thinnings were mixed with 0.5 per cent hydrochloric acid and allowed to stand for several days, a thick viscous pectin solution of light green color was obtained. The pectin in apple thinnings appears to be in a very insoluble form which cannot be extracted by methods used on the more mature fruit. The long period of extraction with hydrochloric acid in the cold showed these apple thinrings to be rich in material yielding pectin of good gelling quality. The yield was about 1 per cent, compared to 0.4 per cent or less for ripe apples.
