IES80727B2 - Fish processing - Google Patents

Abstract

Fish are processed by filleting raw fish and marinating the fillets in barrels in a marinade having a pH less than 5.0 and a salt content of less than 20% for a maximum of 70 days, wherein the barrels are agitated for a maximum of 30 minutes every 72 hours. The fish are preferably herring and the acid may be acetic acid. The cured fillets may be rejected if saccharine is detected and if the histamine content and microbial count are above certain limits.

Description

Fish Processing Introduction The present invention is directed towards a method for processing fish, in particular for marinating herring in marinade.

Marinated herring fillets are a very popular food. However, there are problems associated with ensuring that the .fillets are cured properly.

Ideally, the consistency of the fillet is firm, however, it is often difficult to ensure that there is no excessive fluid retained in the fillet. It is essential that the fillets are marinated with minimal weight loss. Other desirable properties are that the cured fillets have a light meat colour, are free from scales and have hardly any yellow discolourings as the general appearance and texture of the final product can have a major effect on customer acceptance. It is also vital to ensure that the microbial count of the marinated fish is within acceptable limits. It is difficult to achieve all of these properties in the finally cured fish.

The organoleptic properties of the marinated fillet is another important property. The problems of excessive salt, reducing palatability following brining is discussed in GB Patent Specification 2139475. EP Patent Specification 704159 describes a process for processing fish to be canned. An aqueous solution of sodium chloride is injected into the raw fish prior to steaming to improve the taste of the final product.

It is an object of the present invention to provide a marinated herring fillet which is cured, with minimal yellow discolouring, weight loss and has a firm texture.

Statements of Invention According to the invention, there is provided a process for processing fish comprising the steps of:taking the raw fish into the plant and storing in a chilled environment with an air temperature between 0 and 4°C; grading the fish for size and sorting by sex; filleting the fish; placing the fish fillets in barrels; preparing a marinade having an acidic content less than 10%, a pH less than 5.0 and a salt content less than 20%; marinating the fillets in marinade for not more than 7 0 days; agitating the fillets in the marinade for not longer than 30 minutes in every 72 hour period; maintaining the temperature of the marinade at less than 7°C; draining the cured fillets; measuring fish tissue water of the cured fillets to ensure that the acid content is less than 3%, a pH less than 5.0 and a salt content less than 7%; storing the recovered marinade as a packing liqueur; weighing and packing the fillets and topping up the weighed fillets with the liqueur; and storing the barrels at a temperature below 7°C.

We found that gentle agitation on a regular basis had a surprising effect on the overall quality of the resultant cured herring. Not alone was there no discolouration which is a feature of more conventional marinading whether it be a process where the marinade is only occasionally or never agitated. Weight loss was also minimised with not alone a better product due to its moisture retention without water logging but also one with an extremely firm flesh and for the customer one that provides an easy to eat product. It, by virtue of its moisture retention, is attractive financially as it gives increased yield for the producer.

In a preferred embodiment of the invention, the marinade contains not more than 10% acetic acid.

In a particularly preferred embodiment of the invention, the salt content is less than 15.0%, the pH is less than 5.0 and the acidic content is less than 8%. This ensures optimal curing with minimal microbiological contamination.

In a particularly preferred embodiment of the invention, the cured fillet has a fish tissue water containing 2.42.8% acid, 6-6.8% salt and a pH less than 4.2.

In a particularly preferred embodiment of the invention, the female fish have their roe removed and then recycled with the other fish for filleting. This produces a high value product for certain markets.

In an especially preferred embodiment of the invention, the curing is done between 35 and 70 days.

Tests showed that when marinaded for less than 35 days, the marination was not always satisfactory while if carried out for more than 70 days, excessive retention of water occurs with a resultant soggy flesh.

In a preferred embodiment of the invention, the histamine content of the cured fillet is measured and the fillet is rejected if the histamine content is greater than 10 ppm.

In a preferred embodiment of the invention, the saccharine content of the cured fillet is measured and if saccharine is detected, the cured fillet is rejected.

In a preferred embodiment of the invention, the cured fillet is rejected if the microbial count is greater than the following:aerobic number of germs entero bacteria lacto bacteria listeria enterokokk mould <5-10z/g <102/g <102/g negative <102/g negative yeast coliform E. coli <102/g <102/g negative.

Detailed Description of the Invention The invention will be more clearly understood from the following description thereof, given by way of a flow diagram of the marination process and the accompanying figures, in which:Fig. 1 is a flow diagram of a marination process of the invention; Fig. loss 2 is a graph showing the test in one trial; results of weight Fig. loss 3 is a graph showing the test in another trial; results of weight Fig. loss 4 is a graph showing the test in a further trial; results of weight Fig. loss 5 is a graph showing the test results of weight in another still further trial; Fig. 6 is a graph showing the test results of average weight loss during the trials; Fig. 7 is a graph depicting % weight loss during the trials; Fig. 8 is a graph depicting average temperatures during the trials; Fig. 9 is a graphical depiction showing the effect of variation in salt levels on weight loss; and Fig. 10 is a graphical depiction showing the effect of variation in acid levels on weight loss.

Referring to Fig. 1, there is illustrated a flow diagram of a marination process for performing the present invention.

Raw herrings 1 are received and are visually inspected for freshness and quality. Fish passing visual inspection are taken into the chilled storage 2 which has an air temperature of 0-4°C to await processing. Bins containing fish failing to pass inspection are clearly labelled and removed from the site as soon as possible. A conveyor takes the fish where they are sorted by sex, the female are cut, the roe removed and they are recycled with the other fish.

A conveyor takes the sexed fish through a water spray system through size graders 4, into filleting machines 5. Small fish are directed to the filleting machines designated for that purpose and large fish to other designated filleting machines. If grading is not required, the fish pass directly into the designated filleting machines via the conveyor system. Fillets pass out of the filleting machines into a fillet conveyor system which leads to the marinating process. Fillets are visually inspected at 6 on the conveyor system and poorly cut fillets are removed to waste 7 for subsequent processing as a by product.

Fillets for marinating are taken via a conveyor into a marinating weigher and mixer 10 from where they are automatically mixed with marinade at a preset ratio (70 kg of fish: 50 kg of marinade).

The marinade is a mixture of purified water, brine and acetic acid all stored in suitable tanks 25, 28 and 30 respectively. The composition of the marinade has been formulated to marinate fish and kill nematodes. The marinade is produced in 3,000 litre batches. The acid, brine and water volumes are programmed into a batch controller 40, which, when activated, pumps in the required amounts to the mixer 10. All the ingredients are mixed by being recirculated in the batch controller for five minutes. A sample is taken and checked for percentage acid, percentage salt and pH. The batch is adjusted and re-tested if necessary. When the solution is acceptable, it is transferred to a holding tank (not shown) until required for marinating and pumped into the marinating weigher and mixer 10.

Controlled quantities of hydrogen peroxide may be added directly into the weigher and mixer 10, together with the marinade.

The contents of the weigh drum and mixer 10 is then tipped into pre-cleaned barrels. These barrels are sealed and labelled at 45 with a lot number for identification purposes. The barrels are then rolled at 50 to ensure proper mixing of the fillets within the marinade. The barrels are palletised and stacked in the yard. The next day, the barrels are rolled again and inspected. The barrels are left to cure (i.e. to become marinated herring) for a minimum of 35 days in storage 60. The barrels are rolled for a period of not longer than 30 minutes every 24 hour period.

For topping at 65 a pallet containing 9 barrels of marinated herring is taken on a forklift to a stage over a hopper. An operator removes labels, rims, and lids and tips the contents of the barrel into the hopper. The empty barrels, lids and rims are transferred to the wash room for cleaning. Fillets are taken out of the hopper via a conveyor which works as a draining board at 70 to remove excess liquor 70.

An on-line inspection 75 is carried out to remove any oxidised, yellow, or badly cut fillets. The fillets are poured into the pre-cleaned plastic lined barrel, on a weighing scales 80 and the correct weight is made up. Barrels are then topped up with liquor. Food grade barrel liners are tied with plastic cable ties and pre-cleaned lids are put on at 90. The barrels are sealed and labelled 100 with product, production date, lot number and weight. The barrels are palletised and put in export chill 110 having an air temperature of -3 to 0°C pending shipping 150. Marinated herring are exported by container transport.

A series of trials were performed to determine the optimal time and temperature conditions required for marination by using herring fished at various locations. The following tables 1 to 4 give details of the tests. -σ (Ο φ U Ο Ο (_> ο 2 ο ρ— s Ρ— ο φ φ r— >- >- Φ· φ ο ο >- ζ ζ ί u ω ν σι <α ο ΙΛ «ζ» ΙΑ >» Ο r*. σι φ to to ο I r-. σι σι co η co to σι σι σι σι μ co co σι >=r cm φ- CM ο ο ο ο οο σι μ σι to to to to οοοο ο Ό <υ u j<ο ο «ζ» co Φ- CO • · ο ο ι ι κο <σ U Ή σι C U 3 -σ ιζι 0J U 3 4-» ίθ U φ ο. ε φ +-> Ό C (Ο ιζι ο οό 1— «X Lu UI Ο ο +-> «χ ζ -C ζ ο σι 1-) ζ >- ac ·—< ζ Φ < Ζ Ζ 3 Σ ζ ui ιζι ο UI ζ +-> Ο Ζ <χ ζ ·· ο ιζι c ο. ζ Ui UI φ < ζ ζ -σ Η— U. «< φΜ ι—1 ιζι ο\» •φ- ώρ . ο Φ UJ •—ι 13 Ι^ΟΖ » 1—I _Ι • Η— Ο ii ζ -Q α ϋ —1 ·—· ιζι «χ «X CJ CM >—· Η- 1—1 co tzi «X «—t U. ΙΑ Ζ to φ ίΦ U φ Ε φ σι φ φ r1 «X m in csi in m m Οι Οι οι ο» r>. m cm ο csj ιη • · · · ο ο ο ο —•CO σι ΙΟΙ— ΙΟ ο ο ο σι οοοο •Μ CM CO r-t CO —Μ ο ο ο ο CM co «5t co co οοοο O'—lCMrO«3-CO·—•CMCO'S' I Ν.Β. NO Η202 ADDED >· «ο co >» Ό •a to <β σ» «Ο υ ΙΛ «Λ ο Ό 0» (Λ S«β u CSI <α S3 σ οα jp ΙΛ I— ΟΙ «β ί~ V Ο. Ε (U ιζι S >- UJ α CO ζ to >- >—« ζ «« αζ »-· s az _ι Σ az ιη α> ·»— at ω o Z «Μ az o ο c z ·· c_> Q vn «X Q. Z UJ UJ at d> «X az az u ΊΟ »— u_ 3 txi oV +J CM CM o\° · to a • r- to z u 0> UJ IO • ►—1 a» r— -J H- a ^z z a. .o GO —1 ►—« 1/7 ε m «X C_> C\J 1—1 a> »— 1- 00 ΙΛ «X«-· u_ ►— - II ο υ Μ «Ο σ> <0 υ ι/ι ΙΛ 1/7 Ul u u (0 u Q£ l/l l/l (/) +J 4J +J o O O Q. Q_ Q. in in (Z> XJ XJ XJ u >.?> >7 >) cu 3 e s- Ε Ι- e u O <0 3 Ό 3 nJ 3 Q) U a> u O S- c u c u c o l_) o u o o «I >* *» <0 3 ο σι ο ω r*» 3 co σ> ιο CM to οο 10 co co cm co o> σι σ> ο» in —ι in in ONN^t CM O cm r^in m in *3oooo CM I ·»» u 4-> KO σ> co c • •r» rx. U 3 ·· XJ <#» (/) t— 0) < s- U-. l/l >» in co ci ·/* Οι ι*ν co ixrxr^ua Ol 07 07 07 --1 CM • · · · oooo io m in to in in * · · · oooo m n —ι > · · o · c*· »—i io -t-> «3I I (0 u 0) a. E ω 4-» XJ C to Ul V) a 4-> «X -C Z co o> *—· /Σ. •r— on i—· az 0) 5 X an o _ Ul CJ 1/) o 3 +j an υ «X 3 ·· •R» o «η (X Z Ul Ul Φ X) 1— Lu «X m «χ» co co «0- otp . eg •wixtjz 13 · r- «J •1—0^3 -O 0 i—i m m < «X U CM >-i κ >— co in «χ -ί Lu « t« Q. ε <υ c οι O’ 07 co oo cs to 07 07 07 cm in oooo —* cm oo o —-* cm oo m ·—' rx in in in in • · * · oooo oo —i cm oo »# I N.B. NO H202 ADDED * A LOT OF ICE IN -3° BUCKETS +J u 1/) 3 to o UJ o cu ί- u ο E ο •Ο <Λ >> •Ο σ» ιη m σ» <υ <ίCM σ> co m oo cn co lO CO CJ) CT< IO oo o —« cm r-^ co cm oo m co CO CO CO 0) Ο O CM CM «—1 «-Μ θ CM ο O' ^•4 LO ο-4 Ο Ο »—♦ LO θ' cm οο οο σ* cm οο cm ο ο cm <μ co «—' θ θ ο ο ί/> to u «ο ς. φ ex -σ c «ο ι/ι LU Ο «I in LU LU w> >* +» o -C o e» -r- in 0> t—1 □t CM cm χο ο CM Οθ οοσϊσι m io σ> r<υ ae <χ CO CX Z O oc =, LU Q Q CX «X Z -- cu •r— o in «X o. z LU UJ 01 to «X CX ex u ♦» T3 h~ U_ «X 3 c in o\° ♦» 0» X» xj· oV • CD β • «—l !— to z u La to Ul o • ►—» 0> E —1 • t— CJ ax z Q. -Q co _J t—1 tn E ns CM ·— 01 H- t- co m «—1 U_ l·— —i CM fO Μ- © ·—< CM fO O m «—« cm co «οι N.B. NO H20Z ADDED Figures 2 to 5 are graphical depictions of weight loss of the fillets when the marination was performed at -3°C, 0°C and ambient temperature for 0, 15, 35 and 70 days for trials 1, 2, 3 and 4 as detailed above.

Table 5 depicts average weights and temperature during trials 1 to 4.

TABLE 5 Average Weights and Temperatures for Trials 1-4 Ambient 0 Day 15 Day 35 Day 70 Day Avg. Weight 12 9.72 9.49 9.42 Avg. Temp. 8.7 8.7 8.9 % Weight Loss 0 19 20.91667 21.5 0C 0 Day 15 Day 35 Day 70 Day Avg. Weight 12 10.38 10.37 10.3 Avg. Temp. 0.2 -0.2 0.95 % Weight Loss 0 13.5 13.58333 14.16667 -3C 0 Day 15 Day 35 Day 70 Day Avg. Weight 12 10.35 10.43 10.55 Avg. Temp. -1.8 -1.5 -0.25 % Weight Loss 0 13.75 13.08333 12.08333 Figure 6 is a graphical depiction of the average weight loss of the fillets in trials 1 to 4. Figure 7 is a graphical depiction of the percentage weight loss of the fillets in trials 1 to 4. Figure 8 shows average temperatures for trials 1 to 4. The conclusion reached was that the optimal conditions for marination of fillets was a temperature of -3°C to 0°C for 35 days.

Figures 9 and 10 demonstrate the variation in % weight loss arising from further trials. This is due to variations in salt and acetic acid concentration in the barrels. It was concluded that a salt content of less than 15%, a pH of less than 5.0 and an acid content of less than 10% is optimal.

Many variations on the specific embodiment of the invention will be readily appreciated and accordingly the invention is not limited to the embodiments hereinbefore described which may be varied in detail within the scope of the claims.

Claims (6)

1. A method for processing fish comprising:taking the raw fish into the plant and storing in a chilled environment; 5 grading the fish for size and sorting by sex; filleting the fish; placing the fish fillets in barrels; preparing a marinade; introducing the marinade into the barrels; 10 marinating the fillets in marinade for not more than 70 days; agitating the fillets in the marinade; maintaining the temperature of the marinade; draining the cured fillets; 15 measuring fish tissue water of the cured fillets; storing the recovered marinade as a packing liqueur; weighing and packing the fillets and topping up 20 the weighed fillets with the liqueur; and storing the barrels.

2. A method according to claim 1, in which the salt content is less than 15.0%, the pH is less than 5.0 and the acidic content is less than 8%.

3. A method according to claim 1 in which the cured 5 fillet has a fish tissue water containing 2.4-2.8% acid, 6-6.8% salt and a pH less than 4.2.

4. A method according to any preceding claim, wherein the marinading is done between 35 and 70 days.

5. A method for processing fish substantially as

6. 10 described herein.