Fish Processing Centrifuge | Fish Meal Production

Fish Oil Processing Centrifuge - Alfa Laval

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Fish Processing Centrifuge

A fish processing centrifuge is an industrial centrifuge designed to separate fish oil and fish meal from the process water, also known as stick water. A majority of industrial fish processing involves cooking and grinding leftover fish parts, separated into fish oil, stick water, and protein or fish meal. 

Fish Oil Processing Centrifuge Video


Fish Meal and Fish Oil Centrifuge Operation

Fish centrifuges operate by using a high centrifugal force to affect the separation of the three phases of processed fish residue. These centrifuges separate Fish Oil, Fish Meal, and Stick-water from inedible fish processing residue. The fish residue consists of non-saleable fish parts such as skin, guts, heads, bones, offal, and fins.

Pre-centrifuge Fish Processing Steps

The incoming fish leftovers and water are heated in a cooker. This process sometimes uses steam to breakdown the raw fish and release the oil.

The cooked fish biomass passes through a screening process to separate the bulk of solids from liquids. The solids separated at this phase are protein. This solid phase is dried and is known as fish meal. Fish meal is a valuable product that finds many commercial uses in aquaculture and agriculture.

Methods of Centrifuging in Fish Processing

The liquid phase from the process mentioned above consists of oil, water, and fine solids. There are two ways to separate the three phases (oil, water, solids) in this fluid.

Using a Tricanter for Fish Oil Production

The first method uses a tricanter or a three-phase decanter centrifuge to separate the oil, water, and solids simultaneously. A tricanter is a three-phase horizontal centrifuge that separates bulk solids from water and oil. So, a tricanter processing this strained fluid separates the remaining fish meal from the stick-water and fish oil.

However, there is an inherent limitation with using a tricanter due to the lower centrifugal force generated. A lower g-force may not be sufficient to separate the oil and water phases in the feed efficiently.

Using a Decanter and Disc-Stack Centrifuge for Fish Meal

The other method is a two-step process using a 2-phase decanter centrifuge as the first step to de-sludge the process fluid. The decanter separates the fish meal solids from the oil and water. In the following step, the oil and water fluid passes through a three-phase, disc-stack centrifuge.

The following diagram shows this process flow.

Fish Meal Process Flow Diagram
Fish Meal Process Flow Diagram

The disc-stack separator exerts a higher centrifugal force than the decanter, and it separates the fine solids and the oil from the stick water in a continuous process. The separator discharges the fish oil and stick-water through independent outlets while intermittently ejecting the fine fish meal solids.

Further evaporation concentrates the separated stick-water into a thick syrup. Mixing of this stick-water slurry with the strained fish meal produces the final fish meal product.

Fish Oil Polishing Centrifuge

A fish oil polishing centrifuge separates the fine suspended fish meal particles and stick-water to produce pure fish oil. The fish oil produced by the tricanter centrifuges contains residual water and fine suspended particles due to the lower centrifugal force exerted by a tricanter.

Fish oil polishing centrifuges are food-grade,  disc-stack type centrifuges. They could be ‘manual-clean’ or ‘self-cleaning’ type centrifuges depending on the level of contamination. The higher g-force generated by a disc-stack centrifuge, up to 7,000 g’s, is adequate to separate particles down to 0.5µ level and all remaining free water.

White Fish Surimi Decanter Centrifuge
Alfa Laval NX418 Food-Grade Tricanter

Fish Meal Decanter Specifications

The accompanying image shows a ‘self-cleaning’, hydraulic oil centrifuge type Alfa Laval NX418 Decanter Centrifuge. This model is ideal for processing up to 8 Tons per hour of mince fish and water mix.

Fish Meal Centrifuge Models

  Alfa Laval FPNX 309 Alfa Laval UVNX 314 Alfa Laval NX 418
Centrifuge Type Decanter Tricanter Tricanter
Capacity (GPM) 10 40 80
Gear Box 1.0 kNM Cyclo 2.5 kNM Planetary 2.5 kNM Planetary
Bowl RPM 5,600 4,000 4,000
Motor Power (HP) 5 10 20
Frame Size (in) 24″ x 40″ x 40″ (H) 36″ x 48″ x 60″ (H) 36″ x 48″ x 96″ (H)
Weight (Lbs) 800 1,400 2,500

Surimi Processing

Surimi is a seafood substitute often found in imitation lobster and crab meat or fish balls. Minced, refined white fish meat is separated from unusable fish parts to make pure fish protein paste known as Surimi. Whitefish such as pollock and whiting are the primary feedstock for surimi production.

The meat from these fish goes through a sophisticated process to produce a surimi gel. It is a cheaper and sustainable replacement for seafood, especially given that it is also made from farm-raised fish.

Surimi Processing Centrifuge

A surimi centrifuge processes minced, refined white fish meat into a thick fish paste, the base product for commercially sold surimi. The centrifuge separates the gutted fish and fillets from water to produce high-grade surimi.

Traditional Surimi Processing Methods

Traditionally, surimi production involves repeated washing of the white fish meat, also known as leaching. One or more dewatering steps follow this washing process.

A refining step separates unwanted fish parts such as skin, bones, and fins. A screw press squeezes the refined fish meat into primary grade surimi.

The discarded fish parts from the step above go through another leaching step, followed by a screw press to produce secondary grade surimi.

The total yield from this traditional process rarely exceeds 50% of the original fish meat processed.

Alfa Laval Decanter for Surimi Processing

An Alfa Laval decanter system replaces the screw press in the traditional system. It also makes several of the washing steps redundant. Elimination of these steps makes for a much more compact process equipment.

In this replacement process, the fish fillets go through the mincer to separate the skin. The minced fish with added water goes through the refiner to separate remaining unwanted parts, i.e., skid, bones, fins, etc.

The cleaned meat slurry goes through a decanter centrifuge, which separates the water from the fish meat. The separated fish meat is the surimi base. Average recovery rates of over 70% from feedstock are considerably higher than the traditional screw press process.

Hydrolyzed Fish Protein Centrifuge System
Hydrolyzed Fish Protein Centrifuge System

Centrifuge for Hydrolyzed Fish Protein

Enzymes break down fish processing byproducts into Fish Protein Hydrolysates or FPH. The process involves the use of specific enzymes to digest fish protein into a human consumable form.

There are precise process requirements considering the product is for human protein substitute. In some forms, FPH is pre-digested and is directly used for medical supplement use.

The preceding image shows a Hydrolyzed Fish Protein processing facility centrifuges supplied by Dolphin Centrifuge.

FPH is available in liquid as well as solid forms. Longer shelf life and ease of transportation make solid FPH more desirable.

One of the main challenges in the production of solid FPH is the drying of the semi-digested fish protein. Alfa Laval decanter centrifuges work well to dewater the reacted fish protein slurry at controlled temperatures.

A food-grade, three-phase disc centrifuge separates the fish oil before the enzyme reaction step. An Alfa Laval AFPX213 Purifier centrifuge is an ideal centrifugal separator for this process step because it continuously separates the oil from the water and protein solids.

Contact Dolphin Centrifuge for more information and to check our current stock of Fish Oil and Fish Meal processing centrifuges. You can always reach us at (248) 522-2573