Jitendra Kumar¹* M.F.Sc. (Fisheries Resources Management), Neeraj Pathak² M.F.Sc. (Fish Processing Technology), Saurabh Dubey¹ M.F.Sc. (Fisheries Microbiology)

¹ College of Fisheries, Mangalore, Karnataka

² College of Fisheries, Veraval, Gujarat

*Corresponding author: jitenderanduat@gmail.com

INTRODUCTION

Surimi is a wet frozen concentrate of myofibrillar protein of fish muscle (Lanier, 1986). It is deboned, washed and stabilized fish mince. Like many other fishery products it originated in Japan.

Surimi and Surimi based Kamaboko sea foods are traditional products of Japan and occupy an important position in the dietary culture of that country. With the introduction of a new generation of surimi-based seafood products in the form of imitation shell fish analogs, its technology has received worldwide recognition and traditional fish.

SURMI PRODUCTION METHOD

Raw material selection

The important criteria in selection of fish for surimi are:

1) Low cost

2) White meat

3) Non oily

4) Abundantly available year round

5) Good gelling ability

Process of Surimi Production

Raw material Receiving

Fresh fish whole, received in insulated vehicle, is unloaded and taken into raw-material receiving room through chute doors. Organoleptic inspection and temperature check of the raw material is carried out and if found unacceptable, is rejected back to the suppliers. Fish is drained and weighed. Raw material is iced properly and if necessary stored in the chill room (2 -5 ^°C) properly iced.

Sorting & Cleaning

Before processing can begin, the fish must be sorted according to size. This is done so that when the fish are processed by machine the processing speed can be increased and the yield of fillets is raised. Sorting can be performed automatically using either roller or caterpillar type apparatus.

Heading & Gutting

Mechanical fish meat separators, developed by companies in Japan, Germany, and the United States, are modern sanitary machines that remove virtually all the flesh from the frame of a properly prepared fish. According to Piggott, there are several methods to prepare fish for deboning. One is to remove the head, gut, and thoroughly clean the belly walls before deboning the carcass. The other is to fillet the fish and then debone the fillet, which also contains skin and bone.

Washing

After heading, gutting and washing, it is necessary to remove the blood and adherent particles which make it suitable for deboning.

Deboning & Mincing/ Meat Separator

De skinned and deboned fillets give cleaner minced meat because blood, membrane, and other contaminants have been removed. A beheaded and gutted carcass, on the other hand, results in a higher final yield of minced flesh, but the quality is relatively low. Another method is skin on fillet (butterfly shape), which increases yield and keeps quality loss to a minimum.

Washing

The most important step of surimi processing to ensure maximum gelling, as well as colorless and odorless surimi, is efficient washing. Many of the problems with color, taste, and odor that develop in minced is minimized or eliminated when washed.

The number of washing cycles and the volumes of water varies with fish species, freshness of fish, type of washing unit, and the desired quality of the surimi. During a batch process, the water/mince ratio varies from 5:1 to 10:1. In a commercial process, however, repeated washing with continueous agitation is used to accelerate the removal of water soluble substances. It is impossible to measure the exact ratio in a continuous process.

Refining machine

The partially dewatering of mince from the last washing is refined to remove any connective tissue, skin, scales or other undesirable materials.

A typical refiner consists of a cylindrical perforated screen with perforation size of 1-3 mm and a screw shaped rotor. The washed mince is fed in to the machine and soft meat emerges from the front part of the refiner. Towards the near part of the refiner, the meat becomes increasingly more tinged with brown shade, is harder and poor quality. Hard materials such as connective tissue, skin, bones and scales which can not escape through perforations are discharged through the end of the refiner as reject.

Dewatering/ screw pressing

The moisture content of refined mince is about 90%. In order to reduce moisture content to about 80-84%, final dewatering is carried out in a Screw press consisting of a rotary screw and cylindrical screen. The diameter of the screw shaft is tapered or the pitch varies. Generally, the hole diameter of the screen ranges from 0.5 to 1.0 mm at the inlet and from 1.0 to 2.0 mm at outlet. It is also common to use a 0.1- 0.3% salt mixture of NaCl and CaCl₂ to facilitate the removal of water from the screw press. Generally, recovery after dewatering accounts for about 20% of the raw materials.

Mixing with cryoprotectant

The addition of cryoprotectant is important to ensure maximum functionality of frozen surimi because freezing induces protein denaturation and aggregation. Sucrose and sorbitol, alone or mixed at ~9% w/w to dewatered fish meat, serve as the primary cryoprotectant in the manufacture of the surimi. In addition, a mixture (1:1) of sodium tripolyphosphate and tetrasodium pyrophosphate at 0.2-0.3% is commonly used as a synergist to the cryoprotective effectives of carbohydrate additives.

Shaping and packing

Blended material is shaped into blocks of appropriate size and weight (say 10 kg.). Packed into polythene bags by automatic machines or by other equipment.

Rapid freezing and packaging

Surimi blocks are placed in a contact plate freezer and held for approximately 2¹/₂ hrs or until the core temperature reaches -25°c. After inspection of frozen surimi blocks with metal detector, two 10 kg frozen surimi blocks are packed into a cardboard box. Drum freezing of surimi, on the other hand, offers the prospect of rapid freezing, which enhances surimi quality and results in frozen surimi chips, which is a more convenient product form. However, drum freezing may not be preferred by at-sea processors where storage space is limited.

Cold storage

After freezing of the surimi block, it is packed into cartons, which are immediately shifted to cold storage which is maintained below -18^°C temperature. Generally, recovery after cold storage accounts for about 24% of the raw materials.

SURIMI BASED PRODUCT

1) Products with smooth gel structure with no fibrous

Kamaboko

Kamaboko is one of the oldest traditional paste fishery products of Japan. Presently it is mostly made out of surimi. Kamaboko is essentially a gel of myofibrillar proteins. Products are resilient and white in appearance. Kamaboko is also known as fish cake. .

Flow chart of kamaboko preparation

Chikuwa

Chikuwa is made by moulding surimi ground with other ingredients around a brass tube or a piece of bamboo & then moved inside the over as boiling proceeds. Chikuwa has a hollow cylindrical shape. Good chikuwa is white inside with a brown surface.

Hampen

Surimi is ground to fine paste along with Japanese yarn & other ingredients called HAMPEN. HAMPEN is different from Kamaboko (steamed) & Chikuwa (boiled) HAMPEN is processed by boiling. Good HAMPEN has a soft spongy texture resulting from incorporation of air during rapid kneading.

Fish Ham

A method of processing fish ham widely practiced is as follows: salt, sugar, chemical flavorings, spices & a smoke flavoring are added to the surimi and the mixture is allowed to cure for a day or two in a cold atmosphere. The cured mass is mixed with additional quality of surimi, starch and 50% protein and ground to a fine paste. The paste is sealed in a PVC casing and is heated in water at 85-90°C for 40-60 minutes and frozen after cooling. If the product is intended for marketing fresh it will be steamed for four minutes at 120°C.

Microbiological tests

Quality parameter of the surimi my be divided under following three categories,

1. Physical quality

2. Chemical quality

3. Biological quality

1. Physical quality

Physical parameter like pH, gel strength, etc... are important parameter to asses the surimi quality.

(I) pH

For the measurement of pH, add 90 or 190 ml of distilled water to 10g of test sample as needed to disperse. Homogenize the mixture and then measure pH of the suspension with glass electrode pH meter.

(II) Gel-strength

There are number of methods used to asses the gel-strength and other rheological properties of surimi. The most popularly used method for measurement of gel-strength by folding test, teeth cutting and using instrument like the Okada- gelometer.

Folding Test

Round slices of kamaboko with 3 mm thickness and 10 mm diameter are cut from kamaboko. The disks are folded into half between the thumb and forefinger of one hand. Grades of the products are given according to the observation as detailed as below.

Observation Grade Remarks

No crack after folding twice AA Very good

No crack showing after folding in half A Good

Cracks gradually when folded in half B Fair

Cracks immediately when folded in half C Poor

Breaks by finger pressure D Very poor

Teeth cutting test

The sample for testing is prepared as for the folding test. The springiness of the sample is felt by biting the slice between upper and lower incisors and the scoring is made on hedonic scale.

Okada- Gelometer

The Okada-Gelometer has become the standard instrumental method used in surimi industries.

In this test, a piece of surimi of about 25 mm thickness is placed under a plunger with a round top (5 mm). When pressure is applied through the plunger to the test piece, it gets gradually deformed and ultimately broken. The recorded peak force (F) at break and the depth of penetration are used describe the gel properties. Often these two values are multiplied together to give the gel- strength.

(2) Chemical quality

Protein content

The proteins are usually classified in to three categories on the basis of their solubility characteristics; Sarcoplasmic protein, myofibrillar protein and stroma protein. During the surimi processing removal of sarcoplasmic protein by washing cycle, increases the concentration of myofibrillar protein and thus enhances the gel-forming ability. Ultimately the quality of surimi depends on the protein content. The percentage of protein content of surimi is dependent on the species of fish in which the surimi is prepared.

Fat content

Standard method for the measurement of fat content, precisely weight 5-10g of test sample with approximately the same quantity of anhydrous sodium sulphate and a small amount of refined sea sand, put in a mortar. Mash the material uniformly into dry powder and put it in a cylindrical filter paper. Extract and determine the fat content according to soxhlet method and calculate a value according to following formula:

Moisture

The standard method for moisture content determination is by AOAC, Oven Drying method. Utilizing an over night (18 hrs) drying period at 100^°C, take 10gm of surimi sample and put into the oven and after 18 hrs calculate the moisture content by following formula:

MARKET OF SURIMI

The total exports of surimi from India was about 36000 mt worth US $55 million during 2004-2005. There has been a steady increase in the quantity of surimi exported despite increased in plant consumption for manufacture of analogues. One way to further expand the worldwide surimi consumption is tap the markets in East Asia and South Asia, where surimi is used in their traditional food such as fish balls. World market for surimi based products comes from crabsticks and fish balls, where lower grade of surimi are used. While the surimi based products were earlier viewed as imitation seafood, there is a change of image. These products are now being considered as fresh, ready to use items available at an affordable price. Surimi seafood is now promoted as suitable meals as a center of plate items, or mixed with salads. Thinly sliced surimi seafood is also used like meat in sandwiches and other quick meals. In recent times, however, due to economic reasons, there has been a slump in the surimi market particularly in Japan.

SUMMARY

During Surimi production all the steps are important especially washing and mixing with cryoprotectant. Washing helps to remove the sarcoplasmic protein, blood and fat, consequently, it enhances the gel forming ability of surimi. But the loss of considerable quantities of proteins and other nutrients during washing cannot be overlooked. Mixing of surimi with cryoprotectant prevent the denaturation and aggregation of protein during storage.

Looking to the present situation of the marine capture fishery, the catch of commercially important fishes like Shrimps, Lobsters, Pomfrets etc. has been drastically reduced. But the catch of trash fishes or low priced fishes has increased consequently, so the fish processing industries have to slowly shift to the minced meat production rather than the production of whole frozen fish for their profit maximization.