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Abstract This study was conducted to prepare fish burger by replacing minced tilapia fish with 10, 15, 20 and 25% of mashed pumpkin or mashed potato. Canned fish luncheon was prepared by replacing minced tilapia fish with 20, 25, 30 and 35% of beef fat and stored at room temperature for 6 months. Extruded products were also prepared from yellow corn grits (90%) and corn starch (10%). Yellow corn grits was replaced by dried carp fish and dried after fried carp fish with 5, 10 and 15%, then packaged in polypropylene bags and stored at room temperature for 3 months. The chemical composition, chemical and physical quality characteristics, color, texture, microbiological analysis, mercury, cadmium and sensory properties of prepared products were evaluated. The obtained results can be summarized as follows: 6.1. Tilapia fish burger: 6.1.1. Proximate composition of raw materials: Minced tilapia fish had lower moisture (78.26%) and higher protein (18.59%), fat (1.97%) and ash (1.18%) contents than mashed pumpkin and mashed potato. Mashed pumpkin had higher protein (1.89%) and ash (1.01%) contents than mashed potato. Mashed potato had higher carbohydrate content (16.52%) than mashed pumpkin (on wet weight basis). 6.1.2. Proximate composition and energy: Fish burgers formulated with different replacement levels of mashed pumpkin or mashed potato had higher moisture (68.19-69.07%) and carbohydrate (10.86-12.97%) contents and lower crude protein (13.82-15.65%), crude fat (2.13-2.31%), total ash (2.49-2.69%) and energy values (124.45-128.17 kcal/100g) than control fish burger. Moisture content was highly reduced by cooking process. Crude protein, crude fat, total ash and carbohydrates contents were increased by cooking process. 6.1.3. Chemical quality characteristics and pH value: Fish burgers formulated with mashed pumpkin or mashed potato had lower TVN values (9.45-11.20 mg/100g) than control (12.08 mg/100g) at any replacement levels. There are no differences in the TMA (up to 20%) and TBA (up to 15%) values between control and fish burgers formulated with mashed pumpkin or mashed potato. However, TMA, TBA values at higher replacement levels were lower than control fish burger. Neither replacer type nor cooking process affected TVN, TMA and TBA values except TVN values which decreased by cooking process. The pH values were not affected by replacer level, replacer type and cooking process. 6.1.4. Cooking characteristics: Cooking yield was decreased by increasing mashed pumpkin or mashed potato replacement levels. There was no difference in moisture retention value between control and fish burgers formulated with mashed pumpkin or mashed potato up to 15% replacement level. However at higher replacement levels, moisture retention values (73.62-75.11%) were lower than control fish burger (76.91%). Fish burger formulated with different replacement levels of mashed pumpkin or mashed potato had higher fat retention values (167.11- 173.06%) than control fish burger (162.59%). There was no difference in shrinkage value between control and fish burger formulated with 20% mashed pumpkin or mashed potato. At 25% replacement level, shrinkage value (7.96%) was higher than control fish burger (7.64%). Fish burgers formulated with different replacement levels of mashed pumpkin or mashed potato had higher juiciness values (3.84-4.84%) than control fish burger (2.61%) at any replacement levels. Cooking yield, moisture retention and juiciness were not significantly affected by replacer type. 6.1.5. Water holding capacity and plasticity: Fish burger formulated up to 20% mashed pumpkin or mashed potato had higher water holding capacity (2.77-3.29 cm²/0.3g) than control fish burger (2.37 cm²/0.3g). However there was no difference in water holding capacity value between control and fish burger formulated with 25% mashed pumpkin or mashed potato. Plasticity was not affected by replacement levels and types. Water holding capacity and plasticity were reduced by cooking process. 6.1.6. Color measurement: There were no difference in the Lightness (L*) values between control and fish burgers formulated with mashed pumpkin or mashed potato up to 15% replacement level. However at higher replacement levels, Lightness (L*) values (39.94 42.71) were lower than control fish burger (48.26). Fish burgers formulated with mashed pumpkin or mashed potato up to 20% replacement levels had higher redness (a*) values (4.91 5.32) than the control (3.84). However at 25% replacement level, redness (a*) value was similar to control fish burger. Yellowness (b*) values were not affected by replacement levels. Lightness (L*) and redness (a*) values were not affected by replacement types. Fish burger formulated with mashed pumpkin had higher yellowness (b*) values (19.71) than fish burger formulated with mashed potato (13.97). Hue angle values were not affected by replacement levels and types. 6.1.7. Texture profile: Hardness values were increased with replacement levels of mashed pumpkin or mashed potato with the exception of 10% replacement level which increased but not significant. Fish burger formulated with mashed potato had higher hardness (18.55) than fish burger formulated with mashed pumpkin (13.89). Cohesiveness and springiness values were not affected by replacement levels and types. 6.1.8. Microbiological analysis: Fish burgers formulated with different replacement levels of mashed pumpkin or mashed potato had lower total bacterial count, proteolytic bacteria, lipolytic bacteria, psychrophilic bacteria and total yeast and mold counts than control fish burger. All microbial contents were decreased by increasing mashed pumpkin or mashed potato replacement levels. Cooking process reduced total bacterial counts in fish burger from 15-47×103 to 12-44×102 cfu/g of sample. 6.1.9. Mercury and cadmium: Mercury was not detected in all fish burger samples. Cadmium content in fish burger samples ranged from 0.0001 to 0.00481 mg/kg. The Mercury and Cadmium contents in cooked fish burgers were below the permissible limits. 6.1.10. Sensory properties: Fish burgers formulated with 15 and 20% of mashed pumpkin or mashed potato had higher rating scores ranged between 8 and 8.25 of all sensory properties under study and described as like very much. Control fish burger and burgers formulated with 10 and 25% mashed pumpkin or mashed potato had rating scores ranged between 7.2 (like moderately) and 8.20 (like very much) of all sensory properties under study. 6.2. Tilapia fish luncheon: 6.2.1. Proximate composition of raw materials: Tilapia fish had higher moisture (78.26%), crude protein (18.59%) and total ash (1.18%) contents and lower crude fat (1.97%) than beef fat. Minced tilapia fish and beef fat had zero carbohydrates content. 6.2.2. Proximate composition and energy: Control fish luncheon had higher moisture (72.75%), crude protein (14.24%) and total ash (0.98%) and lower crude fat (2.03%) and energy (115.22 kcal/100g) than fish luncheon formulated with different replacement levels of beef fat. Moisture and crude protein contents of fish luncheon formulated with different replacement levels of beef fat were decreased by increasing beef fat replacement levels. However, crude fat and energy values had opposite trend. Fish luncheon formulated with different replacement levels of beef fat had a lower total ash than control fish luncheon. Moisture and energy values of canned fish luncheon were decreased by increasing the storage period. 6.2.3. Chemical quality characteristics and pH value: The TVN and TMA values of fish luncheon were decreased by increasing beef fat replacement levels. The TVN and TMA values were increased by increasing storage period. The TBA values of fish luncheon were increased by increasing beef fat replacement levels and storage period. The pH values were not affected by beef fat replacement level but they increased during storage period. The TVN, TMA and TBA values of canned fish luncheon were within the acceptable limits. 6.2.4. Gross weight, net weight, juiciness, water holding capacity and plasticity: Gross weight, net weight and plasticity of fish luncheon were not affected by replacement levels of beef fat and storage period. Juiciness of fish luncheon formulated with 35% replacement level of beef fat (23.62%) was higher than control fish luncheon (18.74%) and similar to other luncheon treatments. Juiciness was increased during storage period. Water holding capacity was decreased by 25% replacement level of beef fat and similar to 20% and 30% replacement levels of beef fat. However, water holding capacity was increased by 35% replacement level of beef fat than control fish luncheon. Water holding capacity was also increased by storage period up to 2 months. However at 4 and 6 months of storage, water holding capacity was similar to zero time. 6.2.5. Color measurement: Lightness (L*) value of control fish luncheon (38.42) was lower than fish luncheon formulated with different replacement level of beef fat. Redness (a*) value of control fish luncheon (2.47) was higher than fish luncheon formulated with different replacement level of beef fat. Yellowness (b*) value of control fish luncheon was similar to fish luncheon formulated with beef fat up to 30% replacement level. However at 35% replacement level, yellowness (b*) value was higher than control fish luncheon. Hue angle of control fish luncheon was lower than fish luncheon formulated with 25-35% replacement level of beef fat and similar to fish luncheon formulated with 20% replacement level. Lightness (L*), redness (a*) and yellowness (b*) values were decreased during storage period. However, hue angle was increased during storage period. 6.2.6. Texture profile: Hardness of fish luncheon formulated with beef fat up to 30% replacement levels was similar to control fish luncheon. At 35% replacement level, hardness was lower than control fish luncheon and other treatments. Hardness of fish luncheon was reduced during storage period. Cohesiveness was not affected by the replacement levels of beef fat but was reduced during storage period. Springiness of fish luncheon was not affected by replacement levels of beef fat and storage period. 6.2.7. Microbiological analysis: Fish luncheon formulated with different replacement levels of beef fat had lower total bacterial count and proteolytic bacteria and higher lipolytic bacteria than control fish luncheon. Total bacterial count of fish luncheon did not detect at zero time and increased during storage period (2-6 months) from 1×102 to 9.5×102 cfu/g. Proteolytic bacteria and lipolytic bacteria counts of fish luncheon did not detect up to 2 months of storage. However at 4 and 6 months of storage, proteolytic bacteria and lipolytic bacteria counts ranged from 5×10 to 11×10 and 5×10 to 13.5×10 cfu /g, respectively. Total yeast and mold of fish luncheon did not detect during storage period. 6.2.8. Mercury and cadmium: Mercury content did not detect in all fish luncheon samples. Cadmium content in fish luncheon samples at zero time and 6 months of storage ranged from 0.00125 to 0.0082 and 0.012 to 0.097 mg/kg, respectively. 6.2.9. Sensory properties: Fish luncheon formulated with 25 and 30% replacement levels of beef fat had higher taste, odor, texture and overall acceptability than control fish luncheon. However, their color was similar to control fish luncheon. Fish luncheon formulated with 25 and 30% replacement levels of beef fat had higher scores of sensory properties than fish luncheon formulated with 35% replacement levels except for odor which was similar to fish luncheon formulated with 35% replacement levels. All sensory properties of fish luncheon were reduced by storage period. 6.3. Extruded corn products: 6.3.1. Proximate composition of raw materials: Fresh carp fish had higher moisture than other raw materials and lower protein, fat, ash and energy contents than dried carp fish and dried carp fish after frying. Dried carp fish and dried carp fish after frying had lower moisture content and higher protein, fat, ash and energy contents than yellow corn grits and corn starch. However, yellow corn grits and corn starch had higher carbohydrate content than other raw materials. Yellow corn grits had higher moisture, protein, fat and ash contents and lower carbohydrate and energy contents than corn starch. Fresh carp fish and dried carp fish had not carbohydrates content. 6.3.2. Proximate composition and energy of extruded corn products: Extruded corn products formulated with different replacement levels of carp fish had higher moisture, crude protein, crude fat and energy and lower carbohydrate than control sample which formulated with 90% yellow corn grits and 10% corn starch. Total ash content of extruded corn products formulated with 10 and 15% replacement levels of carp fish were higher than control however at 5% replacement level of carp fish, total ash was similar to control. There were no differences in moisture, total ash and carbohydrates between extruded corn products formulated with dried carp fish and those formulated with dried carp fish after frying. However, extruded corn products formulated with dried carp fish had higher crude protein and lower crude fat and energy than those formulated with dried carp fish after frying. Proximate composition and energy of extruded corn products were not affected by storage period. 6.3.3. Chemical quality characteristics and pH value of extruded corn products: The TVN, TMA and TBA values of extruded corn products formulated with different replacement levels of carp fish were increased by increasing replacement levels of carp fish. Extruded corn products formulated with dried carp fish had higher TVN and TMA and lower TBA values than those formulated with dried carp fish after frying. The TVN, TMA and TBA values of extruded corn products formulated with different replacement levels of carp fish were increased by increasing storage period. However, pH values of extruded corn products were not affected by different replacement levels and types of carp fish and storage period. 6.3.4. Physical properties of extruded corn products: Expansion ratio and water solubility index of extruded corn products were decreased and bulk density, shear force and water absorption index increased by increasing the replacement levels of carp fish. Extruded corn products formulated with dried carp fish had higher expansion ratio, water absorption index and water solubility index and lower bulk density and shear force than those formulated with dried carp fish after frying. Physical properties of extruded corn products were not affected by storage period. 6.3.5. Microbiological analysis of extruded corn products: Total bacterial count of extruded corn products was reduced from 2.9×102 to 1.8×102 cfu/g by increasing replacement levels of carp fish. Dried carp fish after frying was more affected than dried carp fish in reducing total bacterial count. Total bacterial count of extruded corn products was increased by increasing the storage period. Proteolytic bacteria count, lipolytic bacteria count and total yeast and mold of extruded corn products did not detect in all samples. 6.3.6. Sensory properties of extruded corn products: Taste of extruded corn products was increased by increasing replacement levels of carp fish. However, color, crispiness, chewiness and pore distribution had opposite trend. Extruded corn formulated with 5 and 10% carp fish had higher surface characteristics than extruded corn control. No significant difference was observed in surface characteristics between extruded corn control and extruded corn formulated with15% carp fish. No significant difference was found in overall acceptability among extruded corn products. On the other hand, extruded corn formulated with dried carp fish after frying had higher taste, crispiness, chewiness, surface characteristics and overall acceptability and lower pore distribution scores than extruded corn formulated with dried carp fish. The color was similar in both products. Color, crispiness, pore distribution and surface characteristics of extruded corn products were decreased by increasing storage period. Taste, chewiness and overall acceptability of extruded corn products did not differ up one month of storage followed by decrease in their scores up to the end of storage period. |