Study Of Thermoplastic Extrusion Cooking On Texturing Of Fish Protein

The use of the marine catch is far from optimal; only about 70% of the total landings are intended for human consumption in different forms. In the fish industry, tremendous amounts of underused edible by-products are available. On the other hand, because of the depletion of many valuable resources traditionally used for producing popular fish products, fish protein from less valuable but abundant species is important to alleviate a protein shortage in human nutrition. From the point of view of utilizing low value fish protein efficiently, a comprehensive review of fish protein utilization, fish protein texturization, food extrusion cooking, et al. are made with emphasis on food protein texturization by extrusion cooking. Analysing results according to the integrated overview of food extrusion cooking technology point out the prospect of fish protein texturization by extrusion cooking: CD To produce consumer value-added products with higher acceptability is important to the use of trash fish. Experience has proven that it must be delivered in forms that fall within the organoleptic limits established by traditional human eating habits. So, by converting fish into protein food ingredients, the products should have a functional value in the food systems already familiar to a populace. ?By extrusion cooking, it is possible to produce products with attractive textures such as textured products with meat structure. Extrusion of protein-rich materials is used to create various "fabricated" foods, most commonly meat analogues or extenders.Research on thermoplastic extrusion cooking on texturing offish protein are conducted by following trials, results from the trials conducted indicate the following points:In the first trial, A Clextral BC-45 laboratory-scale twin-screw extruder was used together with response surface methodology to study the effect of process parameters on extruder stability indicated by running pressure. Process variables examined are: barrel temperature in the last zone, screw speed, solid feed-rate and liquid feed-rate; each at 5 levels. The system-running pressure readings are taken down directly from the control panel during experiment-operation. Results show that three of four operational variables affected running pressure significantly, while the solid feed rate has not a clear effect on the running pressure. System analytical model is given with a R2=0.80, the regression equation is credible to a certain extent.In the second trail, wet extrusion is carried out to study the effect of extrusion cooking process parameters on running stability of the extruder indicated by running current. A Clextral BC-45 laboratory-scale twin-screw extruder was used together with Central Composit Design to study the effect of extrusion cooking process parameters on running stability of the extruder indicated by running current. Process variables examined were barrel temperature in the last zone, screw rotation speed and feed moisture; respectively, each at 5 levels. The system-running current readings were taken down directly from the extruder control panel during experiment-operation. The processing variables and extrusion system response parameters of the experiment were presented as response surfaces and contour lines mapped by means of response surface methodology. As shown as surfaces and contours, an increase in screw rotation speed, or an increase in the feed moisture, generally decreased the system running current significantly, while the barrel temperature has not a clear effect on the running current at the range of variables examined. Regression model was built up with a R2 =0.99, the regression equation is highly credible.The functional characteristics of native fish protein can be changed under conditions of extrusion cooking, depending upon the operational variables used. In the third trail, a Clextral BC-45 laboratory-scale twin-screw extruder is used together with response surface methodology to study the effect of process parameters on functional properties of textured fish protein. Parameters examined are: barrel temperature in the last zone, screw speed, feed moisture; each at 5 levels. Water holding capacity and texture profile assessments of the resultant extrudates are made. Results has shown that all of three operational variables do not affect wet extrusion cooking in the same way. Polynomial regression equations of process variables with two functional properties are obtained with R2= 1.00, and R2 =0.93, respectively. Both of two regression equation is highly credible.In the forth trial, effect of extrusion process parameters on the physical properties of extruded fish protein using a twin screw extruder is studied employing response surface methodology. Parameters examined are: barrel temperature in the last zone screw speed and feed moisture, each at 5 levels. Physical properties assessments of the resultant exctrudates are made indicated by water content and bulk density. Results show that moisture content of extrudates are affected intensely by feed moisture, and bulk density is effectively controlled by controlling the feed moisture, barrel temperature and screw rotation speed. Polynomial regression equations of process variables with two physical properties are obtained with R2= 1.000, and R2 =0.926, respectively. Both of two regression equation is highly credible.In the fifth trail, fish mince made from salmon, mackerel, halibut and silver carp are cooked using different method, 4 treatments includes normal steaming, thermal sterilizing, surimi-based processing and extrusion cooking are emploied. Each species results 4 cooked samples from each treatments. The effects of different cooking methods on the in vitro digestibility of fish protein are investigated. The results show that for all fish species investigated, extruded fish protein exhibit better nutritional value indicated by protein digestibility than raw fish protein and other 3 traditional products.At last, the raw materials used in this study are by-products of herring roe processing. This fatty, darkfleshed fish species is supposed to be highly denaturated because of cyclic changes in temperature (freeze-thaw) and loses gel-forming ability because of its poor protein functionality. Minced fish, as the isolate offish protein (FPI) or fish protein concentrate, is prepared . The water content of minced fish was adjusted to 60% after mixing with SPI, then extruded with a twin-screw extruder. The twin-screw extruder was an intermeshing corotating model (CLEXTRAL BC-45). This operation was carried out at a rate of 33 kg/h, a screw speed of 120 rpm, and a barrel temperature of 160℃. Water-absorption and water-holding capacities of the dried extrudates are inspected. Sensory analysis are conducted by estimating several organoleptic properties of the texturized product, including color, chewiness, appearance or structure, and flavor factors. Fine structure of extrudates are examined with a scanning electron microscope. The results indicate that the defatted fish meat with fat contents of 2.8% and 1.6% (dry base), respectively show better texturization properties. The extrudates appear a sponge structure, and have the chewiness properties of meat. The results of scanning electromicrograph show that the fine structure of extrudates consists of a well aligned fibrous structure, and the fibers parallelt to the extrusion direction. Thermal extrusion cooking should lead to a new way of processing low-value fatty pelagic fish such as herrings, sardines, and mackerels. The texturized products from herring meat and SPI have a meatlike texture and chewiness different from that of other fish products. As a kind of food ingredient, the predominant WAC and WHC are important to edibility.It is the first time that thermoplastic extrusion cooking on texturing of wet fish proteinare studied systematically. Running stability in a twin screw extruder is simulated, and process variables in thermoplastic extrusion texturing of fish protein is optimized. The effects of processing methods on both functional properties and nutritional vale of fish protein are investigated. A fibrously texturized product which can be called value added product is obtained from fish protein by extrusion cooking with a twin-screw extruder. The extrudates have the chewiness properties of meat with a meatlike texture. Extrusion texturized fish protein could have and can be used as a "fabricated" meat or meat extender. Texturized fish protein products from low value fish protein by extrusion cooking can be used as meatlike products or meat extenders after rehydration with water or flavored liquids. Some improvement in color, flavor, and product hardness is still needed for these analogues of animal meat and various expensive seafood items. The work on these issues will be continued.In a word, extrusion processes can be used with great success for upgrading underutilized protein from animal by-products.