ARCHIVES. by P. Lohne. 17 pages typescript FISHERIES AND MARINE SERVICE. Translation Series No. 4119

Transcription

1 ARCHIVES FISHERIES AND MARINE SERVICE Translation Series No Fat'reeparation new knowledge can open new processing'possibilities by P. Lohne Original title: Fettfraskilling - ny kunnskap kan apne for flere prosessmuligheter From: Meld. SSF (3): 9-14, 1976 Translated by the Translation Bureau (PMJ) Multilingual Services Division Department of the Secretary of State of Canada Department of Fisheries and the Environment Fisheries and Marine Service Halifax Laboratory Halifax, N.S pages typescript

2 dqh 4* 4 9 DEPARTMENT OF THE SECRETARY OF ST-ATE TRANSLATION BUREAU SECRÉTARIAT D'ÉTAT BUREAU DES TRADUCTIONS MULTILINGUAL SERVICES DIVISION CANADA DIVISION DES SERVICES MULTILINGUES TRANSLATED FROM TRADUCTION DE INTO EN AUTHOR - AUTEUR Norwegian English Per Lohne TITLE IN ENGLISH TITRE ANGLAIS Fat separation--new knowledge can open new processing possibilities. TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÉRE (TRANSCRIRE EN CARACTLRES ROMAINS) Fettfraskilling--ny kunnskap kan Rpne for flere prosessmuligheter REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE e0reign CHARACTERS. RÉFÉRENCE EN LANGUE ÉTRANGE.RE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTèRES ROMAINS. Meld. fra SSF. REFERENCE IN ENGLISH RÉFÉRENCE EN ANGLAIS Reports from SSF. PUBLISHER SSF. ÉDITEUR PLACE OF PUBLICATION LIEU DE PUBLICATION Bergen, Norway YEAR ANNÉE DATE OF PUBLICATION DATE DE PUBLICATION VOLUME ISSUE NO. NUMÉRO PAGE NUMBERS IN ORIGINAL NUMÉROS DES PAGES DANS L'ORIGINAL NUMBER OF TYPED PAGES NOMBRE DE PAGES DACTYLOGRAPHIÉES 17 REQUESTING DEPARTMENT MINISTÉRECLIENT Envi ronment TRANSLATION BUREAU NO. NOTRE DOSSIER N BRANCH OR DIVISION TRANSLATOR rtel ,1 I MR (INITIA UV" I.n6..1 LS) DIRECTION OU DIVISION Fisheries TRADUCTEUR (INITIALES) PivreT PERSON REQUESTING DEMANDÉ PAR YOUR NUMBER VOTRE DOSSIER N 0 Dr. R.G. Ackman of1-130-pa-b-tar Halifax, N.S. SEP DATE OF REQUEST DATE DE LA DEMANDE SOS (R E V. 2/68)

3 I -Secretary SeCrétariat of State d'état TRANSLATION BUREAU BUREAU DES TRADUCTIONS W in I I MULTILINGUAL SERVICES DIVISION DES SERVICES DIVISION MULTILINGUES CLIENT'S NO. DEPARTMENT DI VISION/BRANCH CITY N DU CLIENT MINISTRE DIVISION/DIRECTION VILLE Environment Fisheries Ottawa LAMING. LANGUAGE TRANSLATORONIVALO N DU BUREAU LANGUE TRADUCTEUR (INITIALES) Norwegian PMJ..SEP Fat separation-new knowledge can open new processing possibilities. Fettfraskilling--ny kunnskap kan.pne for flere prosessmuligheter by Per Lohne Meld. fra SSF.(3):9-14 (1976) UNEDITED TRANSLATION For information only REVISEE TRADUCTI:»1 Information seulement Editor's comments: 9 The article is partly based on preliminary results from projects underway, but we have found it useful to consider these results in connection with the practical experiences we have. During 1977 an extensive report will be given on the results from the project "Fat tissues in fish" being carried out at the Technical University in Trondheim. SEC 5-25T (6/76)

4 2 Studies of fatty tissues in fatty fish (capelin e mackerel and herring) at NTH which are still underway, have shown that 55-70% of the total fat is located under the skin and in the bellyflap of capelin. The fat cells seem to be weak and can, for instance, be broken by mechanical forbeè. 'These resùlts place existing fat separation methods in a new light, and can explain, for instance, why a temperature of C from the cooker will give optimal fat separation in the press and decanter. This new knowledge indicates that a procedure inveving washing out the fat with stickwater can be very useful, for instance in combination with the LT-process. The process of the future could perhaps involve fine disintegration of the raw material and direct processing in centrifuge after heating to C. Separation of the fat from the dry matter in the fish is an essential operation in the production of meal and oil and still presents problems for the reduction plants. This in spite of the fact that much time has been spent both on research and actual processing studies in order to solve this problem. The difficulties in processing fresh winter capelin with satisfactory results a few years ago led to a relatively intense research effort in this field by SSF. (Research Instituta of the Norwegian Herring Meal and Oil Industry.) These difficulties are still present, especially when meal for human consumption is to be prepared from fresh raw material. The results of this research effort resulted in the LT-process. (1.) (2). The sur-

5 prising results with regard X to fat separation and process temperatures 3 were the opposite of common opinion at the time. Since it was difficult to understand the theory behind the findings, the Institute for Technical Biochemistry, Technical University of Norway (NTH), Trondheim, initiated a study of fat cells and the distribution of fat in the flesh of capelin, mackerel and herring (3). These studies have shed new light on the fat separation technology. They explain why low processing temperatures can be favorable, but also indicate that other, perhaps completely new, techniques can be considered. In this article we will discuss some of the factors that affect fat separation and the possibilities indicated by the new research results. The fat is found in a relatively free form in the fish. The studies at NTH aim at obtaining basic knowledge on the location, composition and properties of the fat depots in fatty fish species. The aim is to obtain exact knowledge which can assist in the studies underway to improve existing processes for the processing of capelin e mackerel and herring. This project "fat tissues in fish" is still underway and we shall 11,1 here only carry out some preliminary evaluations of the usethie reduction (p.10 industry can make of the existing results. ---Most of the fat in capelin is found in special fat cells which ImechanicallyrCen be considered to be -\relatively weak. ---In capelin between 55 and 70% of the total fat in the fish is localized in two chief depots, in the skin and bellyflap, see figs. 1 and 2. In female capelin before spawning the roe is also an important fat depot.

6 4 ---The fat distribution in mackerel and herring differs on many important points from the pattern which is typical for capelin. In mackerel, the area under the skin and the light muscle are the major fat depots (60-70% of total fat amount), see fig. 1. Different methods for improving fat separation. 1. Use low processing temperature, LT-Process. The work that has been carried out with this process is well known and has been reported in earlier issues of "Meldinger fra SSF." (1) (2). A clear connection was found between cooking temperature and fat content in press cake and sludge as shown in fig. 3. The reason for this effect has, to a certain extent, been answered by the basic studies at NTH. A careful coagulation (heating to for instance 6o c), can be sufficient to liberate the fat so that it can be separated in a press or a centrifuge. Heating to 95 0C will also liberate the fat in the first instance, but the strong coagulation can lead to "encapsulation" of some of the fat again. This "encapsulation" is stable and is difficult to reverse. The processing procedures proposed to the factories take into consideration the limitations of the machinery to mechanically treat the mass, and the temperatures are a compromise between optimal fat separation temperatures and the machinery performance. No factories are operating today completely according to the LTprocess as suggested in fig. 4. This is partly due to the failure of the experiments carried out to develop a cooker which could give a controlled

7 5 beating of the raw material better than a convential screw cooker. Most factories processing capelin are, however, utilizing the (p.11 principles for the LT-process, and an outlet temperature between 65 and 85 C in the cooker is common today. Low processing temperatures have also successfully been used in processing sprats. The experiments on optimum fat separation with the LT-process have in many cases failed because of insufficient heating capacity before decanter and separator so that there have been problems to attain a low enough fat content in the stickwater. The LT-process has not been tried systematically on other types of raw material besides capelin. Problems with sprats appear to be similar to those for capelin j and similar effects could possibly be obtained. 2. lkébing -out fat. Since fat is not as tightly bound as earlier assumed, it means that methods based on washing out the fat begin to be interesting. It is well known that if press cake is mixed with water and pressed again, the fat content on a dry matter basis will be reduced from 6 to 10%. If stickwater is used the effect is a little less. In practice water cannot be used, since the amount that has to be used is about the same as the amount of press cake. Double pressing will also be costly from an investment point of view. It would be interesting to clarify the effect of adding stickwater just before pressing. In the experiments with the LT-process, the re-circulated livid was added in the cooker. Both stickwater and liquid from the decanter

8 6 were tried, and the amount of liquid was also varied, but no effect on the fat content in the press cake was registered. Use of stickwater to wash out fat appears to be more logical, and the manufacturer of centrifuges Zeta/Alfa Laval has also recommended this. The amount of sludge is however, only ca % of the total solids (fresh winter capelin) and there must be considerable amounts of fat in the sludge in order to affect the fat content of the meal. The fat content in the stickwater seems to have great importance (p.12 for washing out the fat. Very few exact data are available on this, but fig. 5 shows some data found during the experiments with "Centrifish" on fresh capelin in Vadso In this case only decanter (not press) was used and it was probably therefore that the fat content in the meal was so high. The amount of stickwater that must be used is uncertain, but it can in general be stated that the effect increases with increasing quantities of recycled liquid. It appears that feed/stickwater ratios of 2:1 can be sufficient. It can also be of importance where stickwater is being added. Under actual conditions there would probably not be any other possibilities than to add it in the inlet pipe together -with the feed to the decanter. It would have been best if the stickwater could be added inside the decanter in the dry zone ("beach") as shown in fig. 6. In such case it would probably be sufficient with considerable less recycled liquid. A suggested arrangement where washing is used and could be used in practice is shown in fig. 7. The suggested procedure is a combination of the LT-process and washing. (p.13

9 7 By heating to 600c in the cooker it is now known that the fat is liberated and can be washed out. The high temperature in the decanter is due to the fact that the material in the machine must have temperatures above 65 0 order to operate properly. Temperatures of C in the feed to in decanter will assure that the fat separation in the separator is satis- factory, if the temperature is further increased to 95 C before separation. There is no control over all factors that influence - the fat separation during the washing operation. The conditions are chemically and technically probably very complicated and difficult to clarify fully. The next method to be mentioned is an example of this. 3. Washine out fat with chilled stickwater. This method is developed and patented by production engineer A. Nilsen, Bode SildoljefabrikkA/S and the patent has been discussed earlier in Meld. fra SSF (4). The outline of the process is roughly as shown in fig. 7, but the stickwater to be added to the screw conveyor has been cooled to ca. 20 C and the screw is furthermore equipped with a cooling jacket for further cooling of the mixture of press cake and stickwater before pressing in press 2. Ordinary cooking temperatures (95 C in the cooker) are also being used. It should be thought that a law temperature in the cooker would be an advantage, but it is claimed that the opposite has been registered. This method is said to give ca. 3% lower fat content in the meal as mompared to the conventional process and the process is in use at Bode SildoljefabrikkA/S, Bode. During the development of the method it was found therefore to be considerably better fat separation when the washing

10 was carried out with stickwater of 20 C as campared with stickwater at 95 C. The reasons for this surprising effect is not known Storage of the raw material until it is "production ripe." This is the melod used most frequently, but it is also the least desirable method. The disadvantages are obvious since storage leads to reduced oil and meal quality. There can be several reasons for the fact that the fat is easier to get out after storage of the fish, but we do not have full knowledge of ail factors. Years' experience lias, however, shown that it is so. If free fatty acids (ffa) in the fat phase leused as a measure of the freshness of the fish, the following connection between fat in meal and ffa in produced oil has been found for winter capelin (fig. 8.) Fig. 9 shows the same relationship for sprats whichwalso a fish species that can be difficult to process while fresh. The curves cannot be given general validity for the respective types (p.14 of raw material since the data are arbitrarily obtained in connection with experiuents that were not designed for this purpose. It must be expected that large variations could occur depending on the fat content of the raw material, date of catch, biological state of the fish, etc. Process of the future? The process being used today has weaknesses such as camplicated mechanical equipment, high energy demand, difficult to control and there- fore automl-m, etc. The later results probably also indicate that the process is hardly optimal when it comes to separating the fat from the

11 9 dry solids. How should the process be carried out based on the new knowledge? At an early stage in the development of the LT-process it was found that fine disintegration of the raw material with subsequent centrifugation gave better results for non-heated raw material than for fish that had been heated to 95 0C before centrifugation (2). This resulted in a patent which covered fine disintegration and fat separation without heating (5). Today we know that the fat is stored in special fat cells which mechanically are relatively weak and that our results could therefore be expected. The LT-process has shown that there is an optimum temperature(50-60 C) for the fat separation. Furthermore that separation of the liquid phase at C technically can be carried out with a fat content in the stickwater of 1-2%. On a background of these observations the following process can be outlined (fig. 10). The mill (grinder) has two purposes: to break up the rau material so that the fat is easier liberated and so that the raw material together with the recycled liquid behaves like a liquid and yields as little sludge as possible from the centrifuge. It is desirable to keep dry matter in a liquid phase as free of fat as possible. Heating to 500C is carried out in order to have optimum fat separation and at the same time avoid too extensive coagulation. Formation of emulsions is probably the major problem. Fine grinding can result in relatively

12 10 stable emulsions of fat in the separator. SSF is presently carrying out basic studies in this field. Assuming sufficient fine-grinding and that the emulsion is broken, an ordinary separator could possibly separate the fat sufficiently. A combination decanter/separator could also be considered. Dryers and evaporators where the temperatures are not to exceed C will also result in large technical problems. It is understood that there are very many open questions in such a process and considerable research and development is necessary both on the processing and equipment sides. If such a process could be realized, there would be many advantages on the product side, and it should be a simple matter to autom-z-e the process.

13 11 Literature (1) (2) ' (3) (4) (5) Lohne, Per, A. O. Utvik og T. Nordhus: «LT-prosessen sluttrapport fra forsekene». Meld. SSF, nr. 3, (1972), s. 69. «LT-prosessen. Prosess for opparbeiding av fersk lodde». Meld. SSF nr. 3 (1971) s Mohr, V., A. Ormberg, J. Halvorsen, E. Padget: «Fettvev i fisk» Rapport III. Institutt for teknisk biokjemi. NTH, Trondheim Nilsen, Asbjern, Bode: Patentselmad, utlegningsskrift nr , 25/ «Fremgangsmàte for fremstilling av mel og olje fra fettrikt fiskeràstoff». Utvik, A. 0. og P. Lohne: «Fremgangsmàte for frem.- stilling av mel og olje av fettrikt animalsk ràstoff». Norsk patent nr "The LT-process--final report of the experiments." "The LT-process. Process for processing fresh capelin." "Fat tissues in fish." Report III. Institute for Technical Biochemistry. 4. Patent application no , 25 / "Procedure for producihg meal and oil from fatty raw material." 5. "Procedure for producing meal and oil from fatty raw material." Norwegian Patent no

14 II Hostmakrefl FA-] mackerel vànmkra Spring mackerel 10 m l. u m hmaer, Heaa a. R BaceYtkne Intestines laver tnuetisclemustesclità Sommerlodde Summer capelin L.--I Vimerlodde for wing II Vimerlodde etter uen Winter capelin before Winter capelin after spawning Fig. 1. The lipid distribution in mackerel and capelin (males)

15 13 Fig. 2. Cross section of whole capelin (male). Location: ca. 1/3 1. LMee. light muscle, MM It. arrk muscle, BE =belly epithelium. S = skin = intestines RB backbone (3) ,7v ' C Fig. 3. Fat content in press cake sludge as a function of process temperature.

16 14 :..=.koagulator Heating coagulator C su 1 Dnin C Press Presse Returveske ' "D an Ireos:, Tank 80 C shim sludge Separator 95 C '1 1- Damp eickwater Evaporator Grakse 11" Damp Inndamper Konsentrat Dryer Torke / MI 4' Fig. 4. The LT-process..%feui grake. u la-ares , ,5 % Feu I limvann (recurvxske) Fig. 5. Fat in sludge (dry basis) as a function of the fat content in the re-circulated liquid (stickwater)

17 /1/4111/41/41/ / gez ipaylr M.: fir enimmnsuir _ EMEXISMEIM Fig. 6. shows decanter where the washing liquid is introduced into the decanter (D) in the dry zone. (B) sludge outlet and (C) liquid outlet. Otherwise (A) is inlet, 60 C Koke Cooker Steam + Damp Mltorke To dryer I iiw I'v"XXXXX Presse H 75 C Rlverskrue 80 C 90 C Dekanter Fig. 7. Bruk au utvasking i kombinasjon med LT-prosessen. In 1 Iii InndampIng To evaporator Fig. 7. Use of washing in combination with the LT-process

18 Fia i olje 6 0/ i0 Fig. 8. Winter capelin. Fat in meal as function of F FA in oil.

19 % fett i mei Ffa i olje 6 o Fig. 9. Fat in meal as function of FEA in oil. Raw R5stoff Mae for (kidding Material) bflni d g C Heating to yec Oppvarming til 50 C Retur av vzske mel +-I Dryer Trrke 41 Emulsjons _Emulsion bryter brpekpr 3 e*se sentrifuge/ separator Pentrifuge/S Sludge 4-50-sec Oil H*ole epara tor Dry matter Torrsta-fase Vacuum eva ra- C Vakuuminndamp tit 50,X,ts tor Fig. 10. Process based on fine grinding, beating and direct centrifugation.