effect of drying and storage on the physico-chemical characteristics and protein quality of smoked...
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EFFECT OF DRYING AND STORAGE ON THE PHYSICO-CHEMICAL CHARACTERISTICS AND PROTEIN QUALITY OF SMOKED HORSE MACKEREL (Trachurus trachurus) FILLETS
A RESEARCH PROJECT SUBMITTED IN PARTIAL FULFILLMENT OF REQUIREMENT FOR THENAWARD OF MASTER OF SCIENCE (M.Sc) DEGREE IN FOOD SCIENCE AND TECHNOLOGY
PAGES: 84
TABLE OF CONTENTSTitle page ............................................................................................iApproval page .................................................................................iiDedication ...............................................................................iiiAcknowledgement .............................................................................ivTable of contents ...............................................................................vList of figures .....................................................................................ixList of tables .........................................................................................x
Abstract ..........................................................................................xii
CHAPTER ONE1.0 Introduction ........................................................................................................11.1 Fish production in Nigeria .................................................11.2 Fish preservation and processing method in Nigeria ....................21.2.1 Freezing.......................................................................................31.2.2 Salting .......................................................................................31.2.3 Drying ........................................................................................31.2.4 Smoking .....................................................................41.3 Quality, safety and nutritive value of smoke dried fish ....................51.4 Significance of study................................................................61.5 Research objectives ....................................................................61.5.1 Specific objectives .....................................................................6
CHAPTER TWO
2.0 Literature Review............................................................................72.1 Introduction ..................................................................................72.2 World Fish Production ...................................................................72.3 The Biology of Horse Mackerel .....................................................82.3.1 Appearance ............................................................................. 82.3.2 Nutritional value ................................................................... 92.3.3 Annual fat cycle ....................................................................... 92.4 Post mortem changes in fish ........................................................112.5 Post harvest losses and related food problems ..............................122.6 Fish processing and preservation .................................................132.6.1 Fish drying ......................................................................132.6.2 Fish salting .................................................................... 142.6.3 Fish canning and bottling ....................................................142.6.4 Fish fermentation .................................................................. 15
2.6.5 Fish freezing......................................................................152.6.6 Fish smoking .......................................................................162.7 Spoilage and microbial analysis of fish and fish products ............182.8 Effects of smoking and drying on the physicochemical andconsumer acceptability of fish ........................................ 19
CHAPTER THREE3.0 Materials and Methods ...........................................................213.1 Procurement of raw-materials ............................................213.2 Sample preparation/Fish processing .....................................213.2.1 Smoking process ............................................................213.2.2 Drying of smoked fish fillets ...............................................213.3 Proximate analysis ...............................................................233.3.1 Determination of moisture content ..........................................233.3.2 Determination of dry matter content ........................................233.3.3 Determination of crude protein content .....................................233.3.4 Determination of ash content ..............................................243.3.5 Determination of fat content ................................................24
3.3.6 Determination of caloric value...................................... 243.4 Physicochemical analysis...............................................253.4.1 Determination of pH ....................................................253.4.2 Determination of peroxide value ....................................... 253.4.3 Determination of thiobarbituric acid (TBA) number ..................253.4.4 Determination of free fatty acid (FFA) ...........................263.5 Protein quality analysis .......................................................263.5.1 Determination of soluble protein ...................................263.5.2 Determination of in vitro protein digestibility .......................263.5.3 Determination of amino acid content ......................................273.6 Microbiological analysis ....................................................283.6.1 Total viable count .................................................................283.6.2 Mould count ........................................................................283.7 Sensory evaluation ..............................................................283.8 Statistical analysis ...............................................................29
CHAPTER FOUR4.0 Results and Discussion ........................................................ 304.1 Weight loss during sample preparation (Filleting and Smoking)….30
4.2 Weigh loss during drying operation ........................................... 314.3 Temperature and relative humidity of the storage room ..................314.4 Chemical composition of fresh and freshly smoked horsemackerel fillets .................................................................334.5 Changes in physicochemical quality of smoked and dried horsemackerel fillets during storage ...........................................344.5.1 Moisture content ...........................................................344.5.2 Dry matter ......................................................................364.5.3 Protein content .............................................................374.5.4 Fat content ..............................................................384.5.5 Ash content .............................................................404.5.6 Caloric value .................................................................414.5.7 Peroxide value (PV) .......................................................424.5.8 Thiobarbituric acid (TBA) number .................................... 434.5.9 pH ..............................................................................454.5.10 Free fatty acid (FFA) content ..................................... 464.6 Microbiological quality of smoked and dried horse mackerel filletsduring storage................................................................484.6.1 Total viable count (TVC) ....................................................484.6.2 Mould count .................................................................494.7 Changes in protein quality of smoked and dried horse mackerel
fillets during storage ................................................ 504.7.1 Protein solubility ........................................................504.7.2 In vitro protein digestibility .........................................514.7.3 Amino acid composition ...........................................534.8 Changes in sensory qualities of smoked and dried horse mackerelfillets during storage ................................................. 59
CHAPTER FIVE5.0 Conclusion and Recommendation .................................... 63References ........................................................................................65Appendices .................................................................71
LIST OF FIGURESFigure 1: Flow chart for the production of smoked and dried horse mackerel fillets 22Figure 2: Changes in moisture content (%) of smoked and dried horse mackerel filletsduring storage ....................................................................................35Figure 3: Changes in dry matter content (%) of smoked and dried horse mackerel filletsduring storage ....................................................................................37
Figure 4: Changes in protein content (%) of smoked and dried horse mackerel filletsduring storage.....................................................................................38Figure 5: Changes in fat content (%) of smoked and dried horse mackerel fillets duringstorage. ...............................................................................................39Figure 6: Changes in ash content (%) of smoked and dried horse mackerel fillets duringstorage. ...............................................................................................40Figure 7: Changes in caloric value (Kcal/100g) of smoked and dried horse mackerelfillets during storage ..........................................................................41Figure 8: Changes in peroxide value (meq/kg) of smoked and dried horse mackerelfillets during storage. .........................................................................43Figure 9: Changes in thiobarbituric acid (TBA) number of smoked and dried horsemackerel fillets during storage. ..........................................................44Figure 10: Changes in pH of smoked and dried horse mackerel fillets during storage 46
Figure 11: Changes in free fatty acid (%) of smoked and dried horse mackerel filletsduring storage ....................................................................................47Figure 12: Changes in protein solubility (%) of smoked and dried horse mackerel filletsduring storage.....................................................................................51Figure 13: Changes in vitro protein digestibility (IVPD) (%) of smoked and dried horsemackerel fillets during storage. .........................................................52
LIST OF TABLESTable 1: Fish, crustacean, mollusks (fished in 2001) .......................................….7Table 2: Average per capita consumption of fish and shellfish (2001-2003) ..................................................................................................…10Table 3: Nutritional value (100g fillet of mackerel) .......................................…11Table 4: Scale employed for evaluating freshness of chilled horsemackerel ............................................................................................…17
Table 5: Weight loss during filleting of horse mackerel fish ...........................…30Table 6: Weight loss in horse mackerel fillets during smokingoperation… .......................................................................................…31Table 7: Weight loss in smoked horse mackerel filletsduring drying treatment.........................................................................31Table 8: Temperature and relative humidity of the storage room .......................32Table 9: Chemical composition (%) of fresh and freshlysmoked horse mackerel fillets ..............................................................33Table 10: Total viable count (cfu/g) of smoked and driedhorse mackerel fillets during storage ..................................................48Table 11: Mould count (cfu/g) of smoked and dried horsemackerel fillets during storage .............................................................49Table 12: Amino acid composition (g/100g protein) of smokedand dried horse mackerel fillets during storage (Day 0) ......................55Table 13: Amino acid composition (g/100g protein) of smokedand dried horse mackerel fillets during storage (Day 10) ....................56Table 14: Amino acid composition (g/100g protein) of smoked
and dried horse mackerel fillets during storage (Day 20) .....................57Table 15: Amino acid composition (g/100g protein) of smokedand dried horse mackerel fillets during storage (Day 30) ....................58Table 16: Changes in appearance score of smoked and driedhorse mackerel fillets during storage .................................................60Table 17: changes in odour score of smoked and dried horsemackerel fillet during storage ............................................................60Table 18: Changes in texture score of smoked and driedhorse mackerel fillets during storage .................................................61Table 19: Changes in taste score of smoked and dried horse mackerel fillets during storage ...........................................................61Table 20: Changes in general acceptability score smoked anddried horse mackerel fillets during storage. .......................................62
ABSTRACTThis study assessed the effect of drying on smoked horse mackerel fillets during storage at room temperature. Smoked horse mackerel (Trachurus trachurus) fillets were prepared by smoking brined horse mackerel fillets in a traditional improved kiln for 4 hours at 60 – 70oC. The fillets were later oven-dried at 65-70oC for 0, 2, 4, 6, and 8 hours, spread on perforated trays and stored at room temperature of 24.5 – 34oC and relative humidity range of 59 – 87% for a period of 30 days. The samples were tested after every 10 days for physico-chemical, microbial and sensory qualities as well as for amino acid composition. The results obtained showed that smoking reduced the moisture content from 73.61 to 20.93% which led to concentration of other proximate components. There was a significant difference (p<0.05) in the proximate composition of the dried samples with drying treatment and on storage. Drying treatment decreased the moisture content of the smoked fillets from 20.93 to 14.57% on the 0 day while the other components increased significantly presumably due to increase in dry matter with protein forming the largest in quantity (65.30 – 70.93% on 0 day). With the exception of control, caloric values for all the samples were within the range of United States Recommended Dietary Allowance (US/RDA) of 450 – 600 kcal/100g. Thiobarbituric acid value (TBA), peroxide value (PV), and free fatty acid (FFA) increased with drying treatment while pH, soluble protein and in-vitro protein digestibility (IVPD) decreased. Sample dried for 8hrs recorded the highest range of values in TBA (0.574 to 1.040), PV (5.40 to 16. 88 M.eq/Kg), and FFA (0.671 to 1.109% oleic acid). Control sample had the
highest range of values in pH (6.49 to 6.22), soluble protein (54.78 to 48.29%), IVPD (99.44 to 94.07%).
There was a general decline in all the analyzed parameters at the end of the storage period. Drying treatment and storage severely affected the amino acid composition with control sample showing highest concentration of 47.10 to 27.42 g/100g protein. Microbial growth was not detected in freshly smoked and dried samples; however storage significantly increased the total viable and mould growth to a range of 2.98x103 – 5.00x105 cfu/g and 2.76x103 – 4.73x103 cfu/g respectively for all the treated samples on the 30th day with 8hrs dried sample recording the least growth. Sensory results revealed decline in sensory qualities but was still acceptable after 30 days of storage. The study showed that drying treatment enhanced the shelf stability of the smoked horse mackerel fillets. However, it also indicated that long time drying treatment and storage time could negatively influence the protein quality of horse mackerel fillets stored at room temperature.
CHAPTER ONE1.0 INTRODUCTIONFish has been one of the main foods for humans for many centuries and constitutes an important part of the diet in many countries. Fish are nutritious foods that constitute desirable components of a healthy diet (Erkan et al., 2010). The advantages of fish as food are its easy digestibility and high nutritional value. It is much sought after by a broad cross section of the world’s population, particularly in developing countries. It is estimated that 60 percent of people in developing countries depend on fish for over 30 percent of their animal protein supplies, while almost 80 percent of most developed countries obtain not less than 20 percent of their animal protein from fish (FAO, 2005). However,
with the increased awareness of the health benefits of eating fish and ensuring rise in fish prices, these figures are rapidly changing. Despite the ensuing prices, fish still represent a cheap source of animal protein.
Apart from being a good source of animal protein, fish also provide other nutrients such as fat soluble vitamins, and they are good sources of some minerals like calcium, phosphorous and iron (Belitz et al., 2009). They also contain significant amounts of all essential amino acids, particularly lysine in which cereals are relatively poor. Fish protein can be used therefore to complement the amino acid pattern and improve the overall protein quality of a mixed diet (Osibona et al., 2009). The flesh is consumed when prepared as a form of delicacy or the other; various brands of oil are extracted from the flesh and the fluids of the fish (Ayolabi and Fagade, 2010). Fish farming, its harvesting, handling, processing and distribution provide livelihood for millions of people as well as providing foreign exchange earning to many countries (Davies and Davies, 2009), especially those situated along the riverrine and coastal areas. Industries process many inferior fish and fish waste products into glue, livestock feed and fertilizers. Fish products are also employed in pharmaceutical industries. Therefore, the importance of the fisheries product in satisfying the nutritional and health needs of the people as well as providing foreign exchange and employment cannot be overstated.
1.1 FISH PRODUCTION IN NIGERIANigeria with a population of about 150 million people (2006 census), is the largest single consumer of fish and fish products in the African Region. The country which has an area of 913, 072.64 square kilometers is well watered by the rivers of Niger and Benue and its tributaries, hence abundance of potentials for aquaculture.
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