Fishery products are made from a wide variety of species found in aquatic environment and usually only the  most  desirable  and  easiest  to obtain portions of thecaracas is salvaged for human food. This leaves a large portion which is high protein and nutritionally desirable as  byproduct.   In addition, many unconventional known as trash species caught when fishing for food species  can also be processed into useful products.

Low value fish are also considered to have high nutritive value as that of high value fish like pomfret, seer fish and cephalopods.The following is a description of some of the products that can beobtained from those unconventional species or trash fish.

Fish protein  hydrolysates

Protein hydrolysates have attained an important place in the realms of man's protein fortified foods and beverages. This is mainly due to their high solubility and digestibility.  The technology of production  of protein hydrolysates has become cheapand all machineriesareavailablecommercially.
A variety of methods of production technique are available. The most common among them arc listed

Acid  hydrolysis

Enzyme hydrolysis

Number of enzymes  arc used in the industrial production of  hydrolysates.   The enzymatic production of protein hydrolysates is perhaps the most convenient and cheapest technique.  The processis fast and gives hydrolysates without much loss of essential amino acids. However, a suitable enzyme has to be selected for this purpose. The choice of enzyme depends on factors like stability, specificity  etc.   The important commerciall y available enzymes are papain,pepsin, bromelain, ficiun and trypsin. Most protein hydrolysates are highly bitterin taste because it contains, pepotones, peptides and free arninoacids. Hence, flavouring agents like cocoa, and  jagcry are usually added during their fortification in food preparation to mask their bitter taste.

Among the important proteolytic enzymes listed above  the widely used ones are bromelain  and papain. The industrial methods of production of protein hydrolysates using bromein and papain are given below.

Commercially available enzyme  is dissolved in citrate buffer of pH 6. It is centrifuged  and the supernatant is taken. This is stable for 3 months.

Preparation of water fat  emulsion

Ten parts of h ydrogenised fat, antioxidant BHA or BHT(0.01%) and  0.15  part  of sorbitan monostearate (emulsifier) are mixed together and heated to 65°C for about 10 to 15 min. To this, water containing 0.35 part sorbitan monstearate is added   (90  parts)  and  the  whole mixture is homogenized in warring blender and then  kept overnight. Next day the soluble oil wateremulsion is separated from the excess  fat and  taken separately.

Hydrolysis: Take100 parts mixed fish meat, 20 parts   water  and  80  parts oil  emulsion and homoginateina biender for 5min. To the resulting pasty mass the enzyme stock solution is added (six parts by weight) and the whole mass is transferred into a  reaction vessel   maintained at  57°C. Hydrolysis is allowed to continue for 15 minutes with continuous stirring. Mter the reaction is over the mixture  is heated  to 80°C  for 12  min. to deactivate the enzyme. The whole mass is again homogenized ina blender and then rapidly cooled to 5°C.  It is ftltered and the ftltrate is dried in a spray drier.

Hydrolysis with papain

Enzyme stock solution.About 2Sg of the enzyme is taken in 100 ml distilled water and centrifuged. The clear filtrate is taken

Hydrolysis: Comminuted fish meat is cooked with water (1:1 W/V) for 15 minutes  and this process results in sterilization of mixture also. The pH of the mixture is adjusted with acid to 6.5. The  mixture  is transferred  to a reaction vessel maintained at 55°C and the enzyme is added to this mixture (1:30, enzyme nitrogen to protein nitrogen). The whole mixture is stirred vigorously and the hydrolysis is continued  for half an hour until it is completed. The hydrolysates is ftltered and centrifuged,and dried in vacuum to get a fine highly hygruswpic powder.

This can be incorporated in a variety of food preparation like soups, beverages etc as a protein suppliment and there by enhance nutritive value.

Protein hydrolysates incorporated beverages

Protein hydrolysates are bitter in taste and as such unpalatable. One  of the best ways to make the hydrolysates tasty is to add malt,cocoa, sugar and fat to the hydrolysates and the fortified mass  is spraydried to makeita fine powder which is highly hydroscopic and  soluble  in water.   One such formula is given below:

Recipe

Composition by weight %

Fish protein hydrolysate : 30; Malt : 20; Sugar : 20; Milk powder : 10 r'a.t; Cocoa : 10

This product is found highly  acceptable to consumers and acceptability with respect to taste, flavour  and  odour is over  90%.   The  protein efficiency ratio of the product is 22 compared to casein (37) at 10% level of protein.

Ambergris

Ambergris is a compound obtained accidentally from the sea and is valued fabulously because of its use in perfumery.    Its rarity, uniqueness  in chemical composition and high commercial value attributed to some real and certain unimaginative properties, make it one of the most priceless gift of animal kingdom to man. It is often used in the East as an aphrodisiac although  this particular property is not scientifically supported. It has a characteristic musk odour. It is used in blending of a large number of exotic perfumes. Ambergris is collected either from open sea or from seashores. It is often  spotted  in  tropical  and  subtropical seashore of  many  countries like  Australia, Newsealand,India and Bahamas. Eighty percent of ambergris  is cholesterol. A fatty  oil called ambreni, benzoic acid, some other steroids and hydrocarbons are also reported as its constitutes.

Ambergris is now  considered as a morbid concretion from the intestinal tractof sperm whale (Pystercatadon,Lphyslen.dae)and probably only of male whale. It comes from the stomach of dead whale.  This is based on  the enormous size of ambergris cited in the past. A mass weighing184 kg and 1SO em in girth and another weighing up to 418 kg were recorded in the past. This would have come from vety big animal like whale. When sperm whale feeds on cuttlefish due to some injury or un known reason the ambergris is formed in the insteines.This is based on the findings that small fragments of cuttlefish are seen in the ambergris when it is freshly collected.

Ambergris is  normally  jettisoned from   the intestines when the whale dies.  By constant exposure to sun and seawater ambergris hardens and develops a pleasant scent.  A good  quality ambergris is soft, waxy and gray in colour.Black ambergris isof poorest quality. Although itis sticky it can be kneaded with the fingers. A good quality and aged ambergris is found to have a concentric layered structure resembling that of onions. Properties:   It is grey to black waxy mass with characteristic odour. Density-0.8 to 0.92, Melting point 60 to 65°C, Softening point  45 -65°C It is inflammable and al\most volatile by heat. It is insoluble in water or alkali but soluble in  hot alcohol, chloroform, ether, fats and volatile oils. It bums with a pale blue flame with characteristic musky odour (resembling   the burning smell of rubber) without leaning scum or ash. It also floats on fresh and salt water.

Uses: it is widely used in perfumery on tincture and essence for fixing delicate odours. A . good quality ambergris  has commercial value ranging from  $ 1000 to 2000  depending on  its quality. Ambergris is usually found adulterated with whale fat

Handling and  processing

The valueof the product depends upon its shape, size  and  quality. Being  soft·bodied animals, holothurians have to be h211dled with care after collection.  Efficient handling practices through proper maintenance of cleanliness and hygiene on board,reduce losses during processing and keep the high quality of end product which can fetch maximum value for the product. To meet the required standard the following characteristics of the sand fish have to be considered during fishing handlingand processing.

1. Like  most   holothur.ians, the  sand fish eviscerates whendisturbed.
2. Its skin ruptures, if keep out  of water for long duration.
3. Sticks to each other  with dried slime kept under direct sunlight.
4. The body wall shapes .into holes or cervices of calcium

As soon as the sand fish is landed up a 2-3 em slit is made near the cloaca. Pressing the body wall ncar the oral region facilitates rapid evisceration of gut and entrails.  Any water that may remain inside the body is also squeezed out.  Plastic fish boxes with  smooth interior are  ideal  for holothurians onboard.Live one can regenerate its lost parts if returned to the sea. The use of ice is not recommended because the body wall raptures with cooling.

Processing of sea  cucumber

Bechc-de-mer in cylindricalshape is most preferred in the market. Theanimalsare to be introduced in boiling water so that it is quickly killed in seconds. 1be first reactionof theanimalto adverse situations like intense  heat is into  convex itsdf with the longitudinal and circular muscles.  This facilitates formation of cylindrical shape.

Heating causes both outside and inside water of the animal to boil and hence pressure builds up inside the body wallbums up inters removed from the pan before boiling is reached. Ifthe animals are introduced in the boiling water there  is no chanceof talcingwater and buildingup the pressure and consequent breakage of body wall.

A clean shallow saucer pan made of cast iron is filled to two third height with clean sea water and allow to boil. Eviscetated and water squeezed out animal may be put into the pan one by one rill the water rises to  nine tenth of the pan. It is stirred upwith spatulaended pole for 45 minutes. Bottom layers may be made upside down carefully with the stirrer causing no damage to the animal The boiling should be adequate enough to proceed to the next stage of processing. With a ring net end pole, the sea cucumbers are removed and allowed to cool on sand.

Removal of outer layer

Pigment  and chalk like deposits on  the ventral surface of the sea cucumber need to be removed to improve its  market  value.   The  traditional method    followed    involved    bacter ial decomposition of the outer layer. A shallow pit is made  in  the  clean  sandy  beach.   Cooled sea cucumbers are arranged  in  layers, packed  and covered with jute hessian sack. Water is sprinkled to wet thesack and pit closed with sand. After 15 to 18 h, sea cucumbers have been decomposed and.pasty material is present  These are transferred in to a plant fibre woven  basket to half full and immersed in knee-deep water. Trample upon it until decomposed material is washed away. The sea cucumber at this stage will be cylindrical in shape, rubber like,wrinkled and ash greyincolour. After final wash, the sea cucumbers are spread on sand for removing those with white pigment and muddy skin for another round of  boiling. These without any patches are ready for final boiling and drying.

Final boiling

To remove the remnants of bacteria, the material isstirred inboilingseawater foranother 45 minutes. The product is removed and transferred todrying platforms or wire mesh trays for sun drying. Sea cucumbers are dried  until the water content is reduced to 8 10%. The drying process alsocauses some shrinkage.

• Sie - the larger the better
  
• Appearance - smooth surface, uniform shape
• Odour - pleasin& no decomposition smeU
  
• Colour - dark generally preferred
• Moisture content-  10  to 23  %  moistu re content by weight, hard dry product.

Seaweeds and products

From time immemorial man has utilizingseaweeds as food. Agar, alginic acid and  carrageenan are the most important phycocolliod prepared from sea weeds.

The harvested or collected seaweeds should be thoroughly washed inseawater to remove thesand and other foreign materials. For  keeping it for long  period, seaweeds are to be dipped in 2% formalin.  A cottage industrial method for  the extraction of agar is as follows:

Sun bleached sea weeds arewashed in fresh water and  wet  grinded in a stone mortar to  remove impurities and other foreign materials. Sea weeds are boiled with dilute mineralacids for few minutes. Agar gel obtained is ftltered  using a cloth ftlter. Gel is allowed to cool at temperature 0°C to 5°C. When it is thawed at room temperature water is removed.  Freezing and  thawing are  repeated several times. By this method impurities and water are separated. The gel obtained is bleached and dried. After drying it is powdered and  packed. The quality of the agar obtained is not very high in this method. By adopting alkali treatment method (treating seaweeds with O.SN sodium carbonate or   sodium hydroxide, prior  to extraction  very good  quality agar can be prepared.

Uses of agar

Agar was the first phycocolloid used in food industry. In  human food  industry, agar  is used mainly as agelling agent and in a secondary way as a stabilizing agent for controlling viscosity. It is also used as an additive. Usually 1to 1.5 % solution is used for all purposes.

In confectionary to prepare jellies, marmalades, marshmall and fillers and candies or candy fillers. In  marmalade production, agar  is  used   as a thickening and gellingagent. In bakery it is used to cover cakes and icing.  It is  also used for dehydraction of theconfectionary. It is also used

in gelly preparation and yogurt.  Meat industry it is useful for sausage preparation. It is prepared for tissueculturing of plants,and asa bacterial medium and is also used for pharmaceutical purpose as a thickening agent.

Alginates

Most of the brown seaweeds are potential sources of alginates. The properties of alginates vary from one species to another. The main  commercial sources are  Ascophyllum, Drvillaea, Eckmer, Laminaria, Lessonia, Marcrocystis,Sargassm and Turbinaria, Of  these   the  most important are Laminaria macrocystes and Ascophythus. InIndia, sargassm and  turbinaria are  the  two  species of seaweed  used for the production of alginic acid.

Indian alginate irtdustry dependson the sargassum grown in Tamil Nadu coast, Kerala and Gujarat Coast.  The species growingin Gujarat coast gives low viscosity alginates which are unsuitable for the main Indian market of  textile printing. Sargassum found in Philippines is exported toJapan for use in animal feeds and fertilizers.

Uses of alglnates

It is used for fllm formation, filament  formation, food additive,some salts,alginic acid are considered as safe as food. It is used as a thickening gelling and  general colloidal properties. It is used  as a immobilized bio-catalyst: Surface sizing  of the paper is the  main  use of alginates in paper industry. It isalso used in welding industry to coat welding rods.

It is also used in pharmaceutical industry. It is added to increase the viscosity of the medicine, other uses are in medical dressing. It can be used in fish feed as a binder. Alginate gel find small  use in confectionary.