FISHERIES AND MARINE SERVICE Translation Series No. 37.58

Further experiments on the storage of herring in refrigerated salt water (Report.no: 2)

by Olaf Karsti, and Heine Blokhus

Original title; Fortsatte fors^k med lagring av sild i kj^lt salt:vanti. (Report ni. 2)

.rrom: (Norwegian Fisheries Research _Lnstitute, Ber.pen), (98/66) . , l(lp,, 1966

Translated by the Translation Bureau ( PINJ) Mulf:ilingual Services Division Department of the Secretary of State of Canada

Hepai:tmetlt of the Fnviron111ent Eistieries and Karine) Service Halifax Lab*oratory

Halifax, N. S. 1974

1l pages type-script

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Noxwegian AUTHOR - AUTEUR

Olaf Karsti and Heine Blokhus TITLE IN ENGLISH - TITRE ANGLAIS

Further experiments on the storage of herring in refrigerated salt w a-Kter (Report No. 2). TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ETRANGERE (TRANSCRIRE EN CARACTÉRES ROMAINS)

fortsatte fors¢k med lagring av sild i kj^lt saltvann

(Rapport nr. 2)

REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGN CHARACTERS. REFÉRENCE EN LANGUE ETRANGÉRE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTÉRES ROMAINS.

REFERENCE IN ENGLISH - RÉFERENCE EN ANGLAIS

Report No. 98/66 A.h. 26 (1966) 10 p. PUBLISHER - EDITEUR

DATE OF PUBLICATION DATE DE PUBLICATION

Norwegian Fisheries Research Institute, YEAR

ANNÉE

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ISSUE N0. NUMÉRO

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1966

Bergen, Norway

98

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Further experiments on the storage - of herring in refrigerated salt water (Report No. 2)'. (The effect of salt concentrations from 3 to 20 6 and storage at -2 ° and -6 ° C). Fortsatte forsek med lagring av sild I kjelt saltvann (Rapport ni. 2). O (Effekten av saltkonsentrasjoner fra 3 ti1,20% og lagring ved -2 ° og -6 C). by Olaf Karsti and Heine Blokhus Norwegian Fisheries Research Institute, Bergen Report No. 98/66

A.h. 26 (1966) 10 p.

— Coetinued laboratory experiments on the storage of herring in refrigerated p.1 salt water have been aimed at determining if better quality and extended keeping times can be obtained by using a somehwat stronger brine solution, for instance, with sodium polyphosphate added, than by storage in 3% salt solution which was tried earlier (compare report no. 94/65). In addition, storage at somewhat lower o temperatures ( 2 0 and 6 C) was also tried and the herring used in these experi-

-

ments were, therefore, frozen in the salt water. Experimental Two series encompassing 5 and 6 experiments were carried out. Series I was carried out with large prespawning winter herring which were caught west of Kristiansund N on February 14th. The herring were ca. 30 hours old at arrival at the Institute and the experiments were as follows:

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2 1) 4 parts herring stored in 1 part 3% NaC1 solution at -2 °C. 2) 4 parts herring stored in 1 part 3% NaC1 solution + 1.5% na-tripely phosphate at -2 ° C. 3) 4 parts herring stored in 1 part 7% NaC1 solution at -2 ° C. 4) 4 parts herring stored in 1 part 10% NaC1 solution at -2 ° C. 5) Herring covered with ice and stored at -2 ° C. 6) Usual icing at +1 0 C. In Series II the herring were cooled down and frozen in salt solution at -6 ° C. The experiments were carried out with spring herring (post spawning) purchased in Bergen on March 14th. The herring were ca. 40 hours old at arrival at the Institute and the experiments were as follows: 1) Herring covered with ice and stored at -6 °C. 2) 4 parts herring stored in 1 part 10%.NaC1 solution at -6 °C. 3) 4 parts herring stored in 1 part 15% NaCl solution at -6°C. 4) 4 parts herring stored in 1 part 20% NaC1 solution at -6 °C. 5) Ordinary icing at +1 ° C. The cooling of the herring in the salt solution was carried out 'in containers which were placed in refrigerated rooms at -2 ° C and -6 ° C in advance. The temperatures during storage for Series I, experiments 1 to 5, varied from ca. -1.5 0 to -2 °C, and for experiment 6 they varied from 0 0 to o +1 C. In Series II, experiments 1 to 4, the temperatures varied from -5 to -6°C and for experiment 5 from 0 ° to +1° C. RESULTS Series I. (prespawing winter herring) The samples from Series I were quality evaluated and analyzed after 3, 6, 10 and 14 days storage. The following analyses were carried out: Total volatile N, trimethylamine-N, peroxide value, free fatty acids, salt absorption and the appearance, odor and flavor were judged organoleptically.

3

The results obtained are shown in figures 1 and 2.

After 3 days

storage it was noted that all samples were of good quality. There were no differences of importance except that the samples that had been stored in the strongest salt concentrations (7% and 10%) had taken up more salt than the others (figure 1). After longer storage the differences in quality became more noticable. The salt absorption increased further. When comparing the appearances it was found that experiment 5 (ice at -2 °C) kept best, while there were few differences between the others. Averages of odor, taste and texture gave the impression that experiments 3 and 4 (7% and 10% salt water) were best, but the difference was small and without practical importance the first 6 days. Red discoloration developed in the flesh of herring that had been stored in salt water, especially in the samples from experiments 1 and 2 (3% salt). The fillets from the herring that were iced were lighter in color and more attractive. Some of these herring also had burst bellies. This appears, however, not to occur as often when the fish are stored in salt wker with higher salt concentration. The development of volatile N and trimethylmnine-N (figures 1 and 2) shows a more rapid increase and higher values for the samples that were stor£d in salt water (experiments 1 to 4) than for those that were iced

.

(exueriments 5 and 6). On the other side it was noticed that the samples from experiments 5 and 6 (ice) turned rancid more rapidly than the samples in brine. The peroxide values were rapidly increasing when stored longer than 3,-days and here were . good agreements between the peroxide values and organolptically evaluated rancidity. The order of the samples listed in increasing order of rancidity was 2, 1, 3, 4, 5 and 6. The reasons for the difference in rancidity were obviously that by brine cooling an increased protection against the air was obtained compared to that obtained It is also worth notihg that somewhat lower values were found in experiment 2 where sodium tripolyphosphate had been added, than in experiment 1 which was without. The analytical values for peroxide further shows a definite temperature effect for the samples in ice at -2 0 , by the use of ice.

and +1 ° C.

(experiments 5 and 6). When evaluating the results it was concluded that there was little difference between the experiments in the first 5-6 days. Regarding the values for total volatile N and trimethylamine N, the salt con-

4

centrations appear to have a certain effect. The differences found must however be assumed to have little practical importance, but the results indicate that a better keeping ability can be obtained by the use of stronger salt solution and lower storage temperatures. Storage of herring in ice longer than 5 days shows, as mentioned, lower values for the content of total volatile N and trimethylamine N than the storage in salt water, but on the other hand the samples stored in ice were definitely The results for experiments 5 and 6 confirm the importance more rancid. of storage at temperatures as low as possible and indicates that the herring should preferably be superchilled or partly frozen during storage. The problem is, however, to prevent bulk freezing and difficulties in thawing when the herring are to be unloaded. The alternative is therefore to store in salt water with a higher salt content and lower freezing point than that corresponding to 3%. This was as mentioned attempted in series II.

Series II.

(spring herring post spawning)

The samples from series II, where salt concentrations from 10% to 20% wei^é used and chilling and freezing at -6°C were carried out (see eartier), were judged and analyzed after 4, 9, 16, 21 and 32 days storage. As expected the herring kept considerably better than those stored in ice +1°C and in salt water-at -2°C as mentioned under series I. The at relatively long freezing times at -6°C did not appear to have detrimental effect on the texture of the herring of any practical importance for the storage times used. The uptake of salt by the herring and the subsequent dilution of the salt water occurring during the cooling of the herring gave a higher freezing point than -6°C in.the salt water. This resulted in complications with bulk freezing (both of water and herring), thawing difficulties and problems in taking samples in-experiments 2 and 3. If this is to be avoided, a higher ratio of salt water to herring than 1:4 (as used in this case) must be used, but the usable volume will then be smaller.

The results for experiments 2 and 3 were therefore not as ex-

In experiment 4, however, (20% salt in water) the herring froze pected. individually and gave a better base for evaluation as compared to experiment 5 (ice at +1°C).

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7 From figures 3, 4 and 5 it can further be seen that, except for the peroxide values, there were few differences in quality between the samples from experiments 1, 2 and 3. The samples from experiment 4 (20% salt water) were a little better, and experiment 5 (ice at +1°C) had the This is confirmed by the values for total poorest keeping ability. volatile N., trimethylamine N and the criteria for rancidity. Storage in 10%, 15% and 20% salt water however resulted in a salt uptake of 0.9, 1.7 and 2,3% after 4 days storage in experiments 2, 3 and 4 respectively. All samples stored in brine tasted definitely salty after being boiled in It must therefore be assumed that the herring must be soaked in water. water in order to be usable. It can however, hardly be avoided that herring that have absorbed this much salt will take on a flavor similar to salt herring and will be quite different from fresh herring. It is probably better possibilities for using such herring for salting, marinating or reduction, but this would have to be tried under industrial conditions.

CONCLUSION In the continuing experiments on the storage of herring in refrigèr_ated salt water, an attempt was made to obtain quality improvements and'better keep ability by storing in salt water containing from 7% to 20% NaCl as compared to 3% NaCl which was attempted earlier. (Re. no. 94/65) Addttion of Na-tripolyphosphate, storage at -2° and freezing and storage at -6JC were also attempted. The results obtained are shown in figures 1, 2, 3, 4 and 5. It can be seén that there were small differences in quality between samples that had been stored in 3, 7 and 10% salt water and in ice at -2°C for the first. 5-6 days.

After further storage the difference in quality became

The salt concentration appeared to have a certain effect, more noticable. but the differences registered were small and probably without practical Storage in ice showed a slower increase in the content of importance. total volatile-N and trimethylamine-N, than storage in salt water, but the samples in ice showed more noticable rancidity and had higher peroxide The results illustrate the noticable effect and the advantages values. obtained by storing at lower temperatures, and indicate that one should superchill or partly freeze the herring. It was also showed that the

8 addition of Na-tripolyphosphate had a certain effect. Storage in 10, 15 and 20% salt water at -6 °C resulted in complications with bulk freezing, thawing difficulties and a considerable salt uptake.

The salt content in the water became gradually lower so that the freezing point for the water in experiments 2 and 3 (10% and 15% became higher than -6 °C. To avoid freezing the water, the ratio of herring to water must be higher than 1:4, but the usable volume then becomes smaller. The keeping time was, as expected, considerably longer than with ordinary icing and storage in salt water at -2 ° C. It can however be difficult to prevent the herring from taking up so much salt that salt herring-like flavors appears, and this limits the utilization for fresh consumption. The high salt content also makes it necessary to eventually soak the herring in fresh water befor utilization for oil and meal, and this aspect would have to be further investigated.

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