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Fish Quality.pptx

  1. Fish Quality Venny Agustin, M.Sc
  2. Quality • Quality means the level of good or bad on something, the degree or level of quality. Quality means that something has a quality or good quality. • According to Philip B Crosby quality is compliance with requirements or standards. In other words, a product is considered qualified if its specifications comply with predetermined quality standards. • According to ISO 2000, the notion of quality is the totality of the characteristics of a product (goods or services) that support its ability to satisfy specified or defined needs.
  3. ● Source: Oehlenschlager, J and Hartmut ,Rehbei. 2009. Fishery Products: Quality, Safety and Authenticity
  4. Categories of fish species Source: Oehlenschlager, J and Hartmut, Rehbei. 2009. Fishery Products: Quality, Safety and Authenticity
  5. Fish muscle ● The proportion of fish flesh to total body weight varies between 40% and 65%, depending of species, shape, age and the physiological status of the fish. Fish with more elliptical cross sections (tuna, herring and salmon) exhibit a much higher proportion of the edible part than flatfish species or species with very big heads such as monkfish. ● Fish flesh consists of light and dark musculature. Both types can be differentiated by chemical composition, physiological importance and nutritional value. Most species have more light than dark muscle.
  6. Continue… • The light musculature is used for rapid, sudden movements and obtains energy mainly from anaerobic glycolysis. For continuous swimming, fish use their dark musculature. • This type of muscle is therefore well developed in pelagic species (herring, mackerel, tuna), well supplied with blood and rich in myoglobin. The metabolism of dark muscle is aerobic; energy is provided by lipids and carbohydrates.
  7. Nutritional composition • The fat content of fish varies greatly in quantity and fatty acid composition. The protein content is almost constant. The fat content is mainly dependent on biological state of maturity, but also on nutritional status, age, catching ground and season. • The fat is not homogeneously distributed in the body. In lean fish species, it is located in the liver as an energy reservoir; in fatty species, it is deposited in the muscle tissue, as a subcutaneous layer under the skin or in the intestines. • Lean fish species have a higher proportion of polar lipids (phosphatidylcholine and phos-phatidylethanolamine). • The highly unsaturated character of these fatty acids is the reason why they are susceptible to lipid oxidation and oxidative degradation. Fatty fish species therefore have a tendency to exhibit rancid tastes and odours after limited storage time.
  8. Vitamins ● The vitamin contents in fish are species specific. They can vary considerably within one species with age, size, sex, season, diet, state of health and geographic location. ● In fish farmed by aquaculture, the contents of vitamins reflect the composition of the corresponding components in the fish feed. Therefore, the vitamin content of wild and farmed fish can be different.
  9. • The liver of fish is a rich source of fat-soluble vitamins (A, D, E and K). In fish flesh, dark muscle contains more fat-soluble vitamins than white muscle because of its higher fat content. • The flesh of fatty fish still contains moderate amounts of vitamin A, but lean fish contain only trace amounts. Fish and fish products are commonly regarded as the most important natural food sources of vitamin D. • Vitamin E functions as a natural antioxidant to prevent lipids from becoming rancid. Fish flesh is only a low to modest source of vitamin E. • Relatively few values for the vitamin K content of fish are available. The highest concentrations are found in muscle of marine and freshwater fish with high fat content, and in the liver. Fat-soluble vitamins
  10. Water-soluble vitamins ● Most fish species cannot synthesise vitamin C (ascorbic acid). The average vitamin C content of fish ranges from 1 to 5 mg per 100 g. ● The natural thiamin (vitamin B1) content of most fish and fishery products is relatively low. A special problem with some fresh- and seawater fish species is the occurrence of thiaminases. These enzymes cleave the thiamin molecule. They ooccur especially in the viscera of fish. ● For example, carp, mackerel and mussels have high thiaminase activity. The enzymes can act during food storage, but they are inactivated by heat, so cooking and smoking destroy them.
  11. Quality parameters of fishery products • Good quality → Fresh fish • Fresh fish → looks, smells, tastes, as well as the texture
  12. Fresh fish category • Fresh fish caught and not experiencing process preservation or further processing yet. • Fish that haven’t go through physical or chemical changes/ which still has properties same when caught.
  13. Factors determining the quality of fresh fish 1. How to catch fish 2. Fishing port 3. Various other factors, starting from the public sale, packing, transportation and processing
  14. Fish classified into four quality classes Prime Very good once Advanced Good Medium Reverse Spoiled Not fresh
  15. Spoilage of Fresh Aquatic Products • Fish and other aquatic products are among the world’s most perishable commodities. Spoilage in aquatic products begins soon after death. Following the death of fish, blood circulation stops resulting in a series of changes within the muscle. • The spoilage of fresh fish is complicated process for which no single factor is responsible, but, rather it is a combination of several interrelated processes.
  16. What makes the fish spoil? Bacteria Enzymes Chemical
  17. Bacteria ● The flesh of the fish is sterile (free from bacteria) when they are alive, but large numbers of bacteria are normally present in the surface slime, on the gills, and in the guts. ● Freshwater fishes bacteria: mesophilic-gram positive. – 3 layers of cell wall and purple in color. Example: Micrococcus, Bacillus, Cornyformes ● Marinewater fishes bacteria: Psychrotrophic gram-negative- 2 layers of cell wall and pink in color. Example: Pseudomonas, alteromonas, acinetobacter, flavobacterium, cytophaga and vibrio. ● Bacterial spoilage does not start until the passage of rigor mortis.
  18. Enzymes ● Enzymes are protein substances present in the muscle and in the gut of fish that initiate or speed up chemical reactions. ● At the death of fish, the normal regulation system stops to function and the supply of oxygen and energy production ceases. ● The cells begin a new sequence of processes characterized by the breakdown of glycogen (this process known as Glycolysis) – the degradation of energy-rich compounds. ● After death, the enzymes naturally act on the food in the gut tissue. ● Autolysis – the self-breakdown or selfdigestion that results the weakening, softening and discoloration of fish tissues.
  19. Chemical spoilage Spoilage of fish due to chemical changes mainly occurs during storage in ice or in frozen condition. 3 factors in chemical changes or rancidity of lipids: 1. Lipid autolysis – enzymatic hydrolysis with fatty acids, and glycerol as main product. 2. Auto-oxidation – the reaction of unsaturated lipid with oxygen. ● Oxidative rancidity in fish can result to serious quality problems such as rancid flavors and odors as well as discoloration. 3. Denaturation of proteins during frozen storage resulting to tough, dry and fibrous texture.
  20. Post mortem changes in fish muscle The quality and shelf life Type of fish species, physiological condition, killing procedures Biochemical reactions starts
  21. Fish Freshness Parameters Sensory /organole ptic Microbiology Chemical
  22. The freshness of the fish can be seen by the simple method, by looking at the physical condition: ● External appearance; Fresh fish, bright appearance and not dull. There are no biochemical changes. Metabolism in the fish's body is still running perfectly. ● Flexibility of fish flesh; Fresh fish flesh is quite pliable and will return to its original shape when pressed. ● Eye condition; Changes in the freshness of the fish will cause a noticeable change in it’s brightness. ● Condition of gills and scales; Fresh fish bright red, while the fish are not fresh dark brown. For fish scaly if the scales are still firmly attached, no easily released from the body means fish it's still fresh.
  23. Fresh fish VS Spoiled fish
  24. Chemical analysis pH Analysis Hypoxathine content analysis Analysis of dimethylamine, trimethylamine/ammonia levels IMP (Inosine Monophosphate Dephosphorylation) Fat breakdown analysis (ex:TBA)
  25. Chemical freshness determination of fish Fish meat pH analysis • Fish that is not fresh has a high pH (alkaline) compared to fresh fish. Due to the presence of alkaline compounds ex: ammonia, trimethylamine, and compounds other volatiles. Analysis of hypoxanthine content • Hypoxanthine comes from ATP breakdown, the higher the content hypoxanthine then the degree of freshness low fish
  26. Continue… Analysis of dimethylamine, trimethylamine/ammonia levels. • Protein decomposition produces the above compounds, if the freshness of the fish has decreased then volatile nitrogen content enhancement. Patterns of protein breakdown in fresh water fish produce ammonia, while sea fish produce dimethylamine and trimethylamine. Dephosphorylation of Inosine Monophosphate (IMP) • IMP is related to changes in the taste of meat fish and fish freshness, so it can be used to determine the freshness of the fish.
  27. Microbiological Determination Method • Fish naturally carry microorganisms. Dominant microorganisms cause damage in the form of bacteria because of its high protein, water content and the pH of the fish meat is close to neutral making it a suitable medium for growth bacteria • Microbiological testing of fish can be done by determination of the Total Plate Count (TPC). • Only counting the total number of bacterial colonies and then comparing it to the quality standards of fresh fish, the test can take place more quickly.
  28. Sensory Fish Determination Method • This method is easier and faster (using sensory tools) • Sensory testing is more towards observation visually • Sensory testing in the form of color appearance, mind taste and texture • The fresher the fish analyzed the score will be the higher it is. • Its nature is very subjective just rely on panelist senses (e.g. discriminating between foul odor with ammonia or indole odor) • The panelists will give a score on observed samples
  29. Organoleptic Test
  30. Thankyou

Notas del editor

  1. Oksidasi lemak merupakan fenomena yang umum dan sering memberikan perubahan kimia yang berdampak pada penurunan kualitas nutrisi, flavor dan perubahan tekstur produk. Perubahan kimia tersebut bertanggung jawab terhadap terjadinya ketengikan flavor dan aroma