1. Handling of live fish and shellfish
1.1 Removal of off-flavour from fish
(a) Causative agents of off-flavour (Actinomyces, Oscillatoria tenuis, Symploca muscorum, Anabaena circinalis, Volvox aureus); causative compounds (geosmin, mucidone, 2-methylisoborneol).
(b) Practical control measures:
(i) Control in culture systems - minimizing feed wastes, exchange of water, chemical control of blue-green algae, increasing turbidity through mechanical agitation or bottom feeding fish.(ii) Removal from affected fish - keeping in charcoal-filtered clean flowing water; keeping in pond with frequent exchange of water till flavour improves, keeping in floating bags off the bottom, addition of salt to achieve 10‰ salinity (in closed raceways).
(iii) Removal by processing - smoking, steam pre-cooking and addition of vegetable oil before canning.
(c) Influence of temperature on rate of flavour removal and rate of weight loss of fish; method of sensory evaluation for off-flavour.
1.2 Depuration of molluscs
(a) Need for purification of molluscs, conditions favouring concentration of pathogenic micro-organisms by molluscs, bacteriological standards for harvest area and shellfish, certification requirements for import of shellfish to certain countries and markets.
(b) Designs of purification plants.
Criteria for location of plant site.
(c) Different designs of purification plants: layout, plant structure materials, handling equipment, holding baskets, seawater systems, water treatment facilities, purification tank design - size, depth, shape, materials for construction, inflow and outflow piping arrangements, uniform hydraulic flow, cleanability, prevention of disturbance of shellfish by turbulence, vibrations, etc.
(d) Purification process: washing, culling and basketing of shellfish, intake of sea-water, sterilization with chlorine, ultraviolet light or ozone, aeration, temperature control, advantages or disadvantages of process, including cost and flavour of product.
(e) Conditions necessary for successful depuration: maintenance of proper biological state of the molluscs, supply of adequate food to enhance purging of gut, low turbidity, good water quality, proper stacking in depuration tank, prevention of rapid temperature rises to arrest spawning, maintenance of suitable flow rate.
(f) Methods of monitoring and control of harvest area and shellfish:
(i) Fermentation tube test for coliforms, and
(ii) Elevated temperature plate test.
1.3 Holding or temporary storage of live fish, shrimps and prawns before marketing or processing
(a) Objectives:
(i) Maintenance of good condition of animal;
(ii) Improvement of quality of flesh, and
(iii) Minimizing weight loss.
(b) Requirements: supply of clean oxygen-rich water; temperature control; feeding in prolonged holding.
(c) Holding facilities; holding ponds, holding nets, floating boxes, tanks, vats, aquaria.
1.4 Sorting and grading
Species-wise and size-wise; grading devices - grading baskets, mechanical graders and grading nets.
1.5 Transportation of live fish and prawns (see Chapter IV - Seed Production)
1.6 Transportation of fresh fish
Containers used; methods of packing with crushed ice.
2. Fish spoilage
Causes of fish spoilage - autolysis and bacterial spoilage, oxidation and rancidity of fats and protein denaturation; spoilage micro-organisms of fish and fishery products, rigor mortis - pre-rigor, rigor and post-rigor conditions; importance of prolonging pre-rigor and rigor conditions.
3. Methods of evaluating freshness of fish
Organoleptic, chemical (estimation of TVBN and VAN) and microbiological methods.
4. Preparation of fish for processing
Checking for off-flavour, grading, stunning, dressing (scaling or skinning, beheading, cutting of fins and eviscerating), washing and cutting; different forms of preparation - whole or round, drawn, dressed, steak, fillets and comminuted.
5. Preparation of shrimps for processing
Peeling (manual and enzymatic), deveining, washing, different forms of preparation - shell-on, headless, PD, PDC, etc.
6. Preparation of molluscs for processing
Depuration, shucking, washing and packing.
7. Methods of preservation and processing
7.1 Chilling
Icing; determination of quantity of ice required; use of dry ice, liquid nitrogen, cold air, chilled water, refrigerated sea water and refrigerated brine; methods of super-chilling.
7.2 Freezing
Principle underlying freezing technique as a preservative measure; different types of freezers (air blast freezers, hybrid freezers, plate freezers and immersion freezers); cryogenic freezing; treatments before freezing; glazing; use of anti-oxidants; packaging; cold storage; factors limiting shelf-life of frozen products; thawing; cold chain.
7.3 Other methods
Drying, salting, smoking, canning, pickling, fermentation, and preparation of paste products and by-products; their relative merits.
8. Quality control
Methods; national and international standards.
9. Sanitation and hygiene standards for handling and processing establishments, containers, transport vehicles and markets
10. Marketing of fish and shellfish
Importance of consumer research in marketing; marketing patterns based on consumer preferences; packing for the market; use of insulated and refrigerated vans; wholesale and retail marketing.
Practicals
Removal of off-flavour of fish; depuration of molluscs; sorting and grading; packing and transportation of live and freshly killed fish and shellfish; freshness tests; visits to different processing establishments.
