Fish Silage Fish silage – liquefied fish protein – crude - PowerPoint Presentation

1. Fish Silage

2. Fish silage – liquefied fish protein – crude hydrolyzatePreservation of surplus fish and offal – use in animal feeding – alternative to fish mealStarted in 1930sDenmark started commercial production in1948Fish silage industries - Denmark and PolandLittle or no production elsewhere

3. ‘silage’ - a product obtained by preserving and storing wet biological material in a silo (a pit or airtight container) ‘silo’ – traditionally used in conjunction with green forage – preserved either by added acid or by anaerobic production of LAB

4. Liquid product made from whole fish or parts of fish that are liquefied by the action of enzymes in fish – presence of acidMineral acid – sulphuric acidOrganic acid – formic acidEnzymes break down fish proteins into smaller soluble units – partial digestionAcid helps to speed up activity while preventing bacterial spoilage

5. Lactic acid – fermentation of sugar – LAB/starter cultureSource of sugar – molasses>20% oil – removed to reduce rancidity and flavour imparted to flesh of animal fed on silage

6. Acid SilageFish ground to particle size not >10mm in diaMixed well with 3.5% by weight of 85% formic acid (35 kg /30 l of acid per tonne of fish) Thorough mixing - all fish comes into contact with acid - pockets of untreated material putrefyAcidity of the mixture - pH 4 or lower - to prevent bacterial action

7. After initial mixing - silage process starts naturally - occasional stirring helps to ensure uniformityMineral acids – pH reduced to 2 or below – more quantityAcid level – neutralized before feeding to animals – to prevent corrosion – calcium carbonate @ 1-5kg per 100kgFormic acid – no neutralization – inherent preservative action – more expensive

8. CharacteristicMineral acidFormic acidpH24QuantityMore Less CorrosionYesNoCostLessMoreShelf lifeLessMore (1 yr in tropical areas)

9. A mixture of inorganic and organic acids – used for silage productionCheap mineral acids like sulphuric acid or hydrochloric acid – used to lower pH and organic acids like propionic or formic – added for antimicrobial activity

10. Commonly used acids or acid mixtures are:Formic acid (90%) 3% (w/w) of fish mince Mixture of 2.5% (w/w) of sulphuric, formic and propionic acids (1:1:0.5), 3) Mixture of 3% (w/w) of 90% formic acid and 95% propionic acid, (1:1 w/w).4) 3% w/w of 90% formic acid, 95% propionic acid and concentrated sulphuric acid (1:0.5:2 v/v).5) 15% (v/w) of sulphuric acid (25 or 30% strength).6) A mixture of formic acid (1%) and hydrochloric acid having pH 2 to 3

11. Dead fish - post-mortem changes – muscle pH falls to as low as 4 – anaerobic breakdown of muscle glycogen producing lactic acidEnzymes – autolysis - proteins broken down to peptides and amino acids At pH 3.0 – exo and endopeptidases present in digestive tract of fish and tissues – active – effective autolysis Low pH (3.0 or lower) – limits hydrolysis to mostly endopeptidases – lesser degree of hydrolysis (65—70%) – more amount of longer peptide fragmentsHigher pH (3—4) –hydrolysis by exopeptidases also – higher degree of hydrolysis (up to 80%) – amino acids and small peptide fragments

12. Degree of autolysisDepends on nature of raw materials80% in temperate fishes 40-45% in tropical fishes High degree of hydrolysis – greater liquefaction and digestion of fish – higher yields of silageLess soluble amino acids - separate from silage on standing

13. Greater leaching losses – incorporation of such silages into feeds – poor assimilation Hydrolysis limited by – Heating to inactivate enzymesAddition of formalin

14. Preservative principle – reservoir of un-ionised molecules of acids – cross bacterial cell membrane – dissociate in cytoplasm – lower pH - death of cellOrganic acids like formic and propionic acids - exist mostly in un-ionised state even at fairly low concentrations Inorganic acids – remain un-ionised at high concentrationsBacterial growth – readily inhibited by either kind of acidFungal growth – inhibited by only organic acids

15. Production tank - any size or shape - acid resistantSteel containers - making or carrying silage - polyethylene liner to prevent corrosionConcrete tanks treated with bitumen - suitable for holding large quantitiesSize and number of tanks depend on amount and type of raw material available

16. Rate of liquefaction depends on Type of raw materialMost species suitable sharks and rays - difficult to liquefy - mixed in with other speciesFatty fish liquefy more quickly than lean fishBony fish liquefy more quickly than cartilagenous fishFreshnessFresh fish liquefy much more quickly than stale fishFish – minced and acid added immediately the raw material is received – avoid slow liquefaction of stale fish

17. Temperature of the processThe warmer the mixture, the faster the processSilage from fresh white fish offal 2 days to liquefy at 20°C 5-10 days at 10°C - much longer at lower temperaturesWinter - heat the mixture initially, or keep it in a warm area until liquidTemperature >40C – enzymes become inactivePeriodic agitation – assist liquefaction1-2 weeks

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19. Biological silage Fermentation by lactic acid produced by bacterial actionGround fish – made into slurry by mixing with 10% molasses and 30% waterCooked for 10 min – then cooled18-22 hrs old culture of Lactobacillus plantarum added – mixed well – allowed to ferment for 72 hrs

20. Streptococcus faecalis, Lactobacillus plantarum, L. brevis, L. cerevicae, and L. mesenteroidsL. plantarum - best suited for fish silage production – tolerate very low pH and high salt content up to 8%Ferment sugars to organic acid, predominantly lactic acid – thus lowering pHAt low pH - growth of putrefying organisms inhibited bycompetitive inhibition action of certain antibiotics produced in the system

21. Process of conversion of carbohydrate to lactic acid by fermentation – anaerobic 3 stagesHydrolysis of starch to maltose by amylaseMaltose is converted to glucose by maltaseConversion of glucose to lactic acid by the bacteriaSmall amounts of acetic acid, propionic acid and ethyl alcohol – also produced

22. Complete liquefaction of silage – 3 to 7 days- separates into 3 or 4 layersOily layer floats at the top - sometimes with an underlying emulsified layerMiddle aqueous layer – forms most of the silageBottom layer – sediment or sludge containing undigested protein, scales and bones

23. Fish silage of correct acidity – stable at room temperature for at least 2 yrs without decompositionProtein becomes more soluble during storageLong term storage – antioxidants viz ethoxyquin added – to prevent ranciditySilage becomes smoother in consistency during storage – develops a pleasant malty odour

24. Silage from fatty fishFatty fish – technological problems – silage produced is susceptible to rapid lipid oxidationFormation of an emulsion phase – occludes sizeable quantifies of proteins – lost – not easily recoverable even on centrifugationFatty silage gives a fishy taint to milk of cattle, eggs of poultry, and meat of pigs and chicken Fatty fishes – not generally preferred in silage production

25. Fatty fish – lipids float on top of silage –anaerobic Lipid oxidation – formation of volatile carbonyl compounds – interact with proteins and make silage nutritionally poorLiberated fatty acids from lipid hydrolysis - solubilisation of protein – lower yield of liquefied proteinsSilage from fatty fish - shorter shelf-life than one produced from lean fish

26. Removal of oilIndustrial production of silage – de-oiling equipments –used to remove excess fatOil content – adjusted to desirable limits before feedingDe-oiling – done immediately after liquefactionOil – removed by centrifuging liquid mass

27. Composition of fish silageVery similar to raw materialMoisture – 70 to 81%Crude protein – 15 to 17%Ash – 2 to 4.5% Fat – 0.5 to 13%

28. Nutritional value of silageSilage concentrate – highly digested protein hydrolyzate – convenient as a protein supply for weaning calves and pigs, and poultryAmino acid composition – lysine, threonine and sulphur containing amino acids are present in high levelsDigestible energy and nitrogen – higher in diets containing fish silage than in those using fish meal

29. TypeDigestible energy(MJ/kg DM)Metabolizable energy (MJ/kg DM)Crude protein (% DM)Nitrogen digestibility (% total N)Mackerel23.422.652.192Whiting 17.516.574.184De-oiled, herring offal17.9-67.591

30. Health, fertility and general appearance – improved when some fish silage protein is included in feedLow levels of inclusion in diet – no ill effects on growth of chicken and pigs and serves as ideal substitute for fish mealHigh amounts of fish silage fed to mature ruminants or fish – production and growth reduced – due to adverse effects of highly hydrolyzed protein in metabolism 5 – 10 % of the feed protein may be substituted by silage protein without negative effects

31. Fish meal vs fish silageParameter Fish mealFish silage Capital costHighLow Manpower requirement Require engg. and tech. staffRequire unskilled workersStorage Less spaceMore spaceOff odour at production centreMoreLessFly infestation during dryingYesNo TransportCheapCostlyMarketingEstablished, well knownNot well known

32. Use of silage as feedEither whole mass or decanted liquid portion – used as feed – cattle, pig, poultry, fur animals and farmed fish Inherent defect – liquid consistency – difficult to transport to distant places and to store – increases costSeparated aqueous phase of silage – concentrated to a higher solids content – Norway and Denmark

33. Solid feed mix – boiled fish silage and rice bran powder – 1:3 – sun-driedResultant dry powder – 9% moisture and 21% proteinRice bran – rich in vitamins, particularly B group and other micronutrients – added advantage – silage usually deficient in vitaminsEasily transported – extended shell-life at ambient temperatures in the tropics