Effect of 10% Concentrations of Salt, Garlic and Coriander on the Quality of Smoked Hilsa Fish (Tenualosa ilisha)
Ripon Kumar Adhikary,
Khandaker Rayhan Mahbu,
Md. Rakeb Ul Islam
The present study was conducted to evaluate the quality of smoked Hilsa fish (Tenualosa ilisha). The fishes were grouped into three parts. One part contains 10% salt, 10% garlic and 10% coriander and treated as Treatment 1 (T-1). Another named was Treatment 2 (T-2) and contained 10% salt and 10% garlic. The other parts contained 10% salt only and treated as Treatment 3 (T-3) to evaluate the quality of the smoked Hilsa with these ingredients for preparing a ready food item. All three treatments were found microbiologically acceptable since indicator organisms and Salmonella were not detected. However, from the results of overall acceptability, taste, colour and texture of the products, Treatment 2 had the best acceptance and significantly different when compared to the other treatments and selected the item as a quick but ready food item in laboratory condition. The moisture content, protein content, fat content, ash content, total volatile nitrogen and salt content of treatment 2 were found 39.65±0.19, 25.65±0.17, 24.85±0.17, 3.50±0.30, 2.55±0.22 and 16.20±0.14, respectively. All three treatments were found microbiologically acceptable since indicator organisms and Salmonella were not detected. However, from the results of overall acceptability, taste, colour and texture of the products, Treatment 2 had the best acceptance and significantly different when compared to the other treatment and selected the item as a quick but ready food item in laboratory condition.
Received: February 01, 2012;
Accepted: April 23, 2012;
Published: June 29, 2012
Fish is the primary source of animal protein in the diet of the most people
in our country. Fish and dried fish is a very popular food item. Fish contribute
about 9% of the total protein composition and 63% of the per capital animal
protein intake in the daily diet of the people. According to the Fisheries Statistical
Yearbook, 2006-2007 per capita animal fish take was 16.62 kg. Per capita annual
fish needed was 25.50 metric tons. Annual total fish demand 2.3 million metric
ton and contribution to animal protein supply is 63% (Department
of Fisheries, 2007).
Fish protein is said to be healthier and cholesterol free. Fish proteins that
contains all of the EAA in right proportion and is called complete protein needed
for the proper growth and development of the animal body. Fish tissue is being
characterized in being rich in protein substance but low in carbohydrate resulting
in high post mortem pH (<6). Further the pelagic fatty fishes have a high
content in lipid consisting mainly of triglycerides with long chain fatty acid
which are highly unsaturated. Also the phospholipids are highly unsaturated
and these circumstances have important consequence for spoilage process under
aerobic storage condition. Fish have rich source of essential nutrients required
for supplementing both infant and adult diets (Abdullahi
et al., 2001).
Fish lives in water. There are millions of very small micro organisms, called
bacteria, in the water that can come in direct contact with fish. Water pass
through the gills and mouths during respiration. Marine fish drinks water, so
these bacteria may enter the stomach. Thus the whole body of fish (skin, mouth,
gills, eyes, stomach) is exposed to bacteria. Most of these bacteria are harmless:
some of these are use to fish, some breakdown vegetation to the soil to release
nutrients to the water, but some cause disease in fish and some also spoil fish
(Clucas and Ward, 1996). The spoilage bacteria, however,
cannot spoil the muscle when the fish alive. After death, spoilage bacteria
enter the muscle from the skin and gills, disintegrate the muscle cells and
take necessary energy to grow. As soon as the fish dies the supply of energy
ceases. The fish muscles gradually harden and the entire body becomes stiff
with a few hours of death. This hardening remains for a couple of hours depending
on the species, temperature and other conditions of death (Nowsad,
Smoking is a method of preserving fish which involves some processes of (1)
Cooking, (2) Drying and (3) Preservative value of the smoke (Clucas
and Ward, 1996).
Smoking is a method of preservation that combines six important effects in
fish and shrimp muscle. Fire producing smoke can generate heat and dry the fish
and thus reduce the water activity so that the micro organisms cannot survive.
Hot smoking cooks the flesh and thus destroys enzymes and kills the bacteria.
Wood smoke contains compound like phenol and kill bacteria. Wood smoke contain
compound that acts as anti oxidant. Smoking imparts on the product highly acceptable
bright brown and reddish color. Wood smoking imparts effects of highly relished
characteristics smoke flavor (Horner, 1992).
Ilish is the national fish of Bangladesh. As it is anadromous in nature (an uncommon phenomenon in tropical waters), the Ilish lives in the sea for most of its life, but migrates up to 1,200 km inland through rivers in the Indian sub-continent for spawning. Distances of 50-100 km are usually normal in the Bangladesh Rivers.
In Bangladesh a lot of works were carried on drying (Ahmed
et al., 1979; Morshed, 2005), salting and
freezing (Rabbane, 2006; Sarmin, 2008)
but few scientific works on smoke curing. On the other hand smoke curing method
is the method which is not affected by climatic condition as well as the smoke
cured product has a special taste and color. It also has worldwide acceptability
as processed fish.
The purpose of the present research activities was to investigate the effectiveness of smoking with salt, garlic and coriander treatment to make the fish as a quick but a ready food item that will contain the essential amount of nutrients but in a good quality that will ensure it is not deteriorated in the quality.
MATERIALS AND METHODS
Collection of fish and smoking procedure: The experimental fish were collected from Hatirpul Bazar, Dhaka during very early in the morning. The study was carried out from month of 4 September (2011) to 4 October (2011). The fish samples were transported to the laboratory in sterile polythene bags to avoid any type of microbial contamination. After cleaning and cutting, the fishes were dipped in the solution for about two hours and make ready for smoking. Seven hundred and fifty grams fishes were taken for three treatment and they were soaked in 300 mL of distilled water with the associated ingredients. Temperature and RH inside and outside of the drying box have been recorded carefully by means of thermometer and Hare Hygrometer, respectively. Smoke curing is the final hurdle before tasting that anxiously awaited fish treat. The fishes are to be arranged on rods or rack. Fish may be hanged on S shape. Hooks, strung through gills by rods, split and nailed to rods or simply laid on rock. Regular nails 8 or 10 gauge steel wires, S shaped iron hooks or round wooden sticks are used during curing fish. Build the fire on level ground with non resinous (hickory, oak, maple, apple etc.) wood chip or saw dust to produce fire, constant volume of smoke. Soft (Resinous) wood gives an acrid flavor and odor to fish. Center smoke house over smoldering fire and close flaps. Danger of fire was minimized if ventilation is controlled to promote smoke rather than flames. Alternative method is fire may be built in covered pit or trench outside the chamber. Smoke is conducted into the bottom of smoking chamber via tile on stove pipe.
Preparation of the samples for test: The sample was cut into very small
pieces for sample to test various examinations. Determination of moisture content
of the raw as well as smoke cured fish was conducted by AOAC method (AOAC,
1975). The crude protein of the fish was determined by micro-Kjeldahl method
(Pearson, 1999). The estimation of fat content of experimental
raw fish, smoke cured fish samples had been accomplished by Bligh and Dryer
method. The fresh raw, smoke fish sample (2/3 g) were minced, weighed and ignited
in the crucible. Then it was transferred in the muffle furnace held at dark
red at a rate of 550-600°C for 6-8 h until the residue was white. Finally
the percentage of ash content was calculated. TVN value was determined by the
modified Micro Diffusion technique (Conway and Byrne, 1933).
The volatile bases produced during post mortem changes in fish and their increase
in concentrations indicates fish spoilage. This value was used as a parameter
to estimate the microbiological and enzymatic deterioration of fish. For microbiological
quality assessment the standard plate count was obtained by pour plate method
RESULTS AND DISCUSSION
The comparative studies between the qualities of the three treatments were performed by several parameters, such as biochemical composition, TVN, amount of iron, calcium and phosphorus.
From the Table 1 it is observed that T-1 has the least moisture, protein, fat amount but the highest amount of ash in percentage. T-2 contains more value in moisture, protein, fat but less than T-3. T-3 has the highest value of moisture and fat but less value of protein than T-2. T-3 has the least amount of ash.
The moisture content is medium in T-2 than T-1 and T-3 indicates that it is
resistant to enzymatic and microbial activities and qualities may have lengthened
the shelf life. According to BSTI (1982), the increased
moisture content of dried fishes above 15% favors the growth of mould and insect
infestations which in turn accelerate the spoilage of fish product. According
to Waterman (1976), bacterial action stops at 25% water
content and mould action ceased at 15% water content.
|| Microbiological status of treated Hilsa fish
The moisture content is the highest in treatment 3 but lowest in treatment 1. It seems that as there was highest value in the moisture content it is more likely to be attacked by the microbes. In case of protein percentage also T-3 is the highest but T-1 is the lowest. But in case of fat T-2 is the highest but T-1 is lowest. In case of mineral T-2 contains more in value than T-3.
The TVN value which helps to measure the level of fish spoilage is used widely
to explore the shelf life of fishes. Rahamatullah (1980)
observed a high TVN value varied from 219-512 mg/1000 g in dried pomfret and
reported it unacceptable. At last as the food will be used by a ready food item
the microbial content was also determined. The result of microbiological examination
is given in Table 2.
Total bacterial count was found to range from 2.1x103 to 2.0x104
in the treatments and the treatment 2 showed the lowest count. The total bacterial
counts are similar with the findings of Shewan (1977)
and Gillespie and Macrae (1975). Indicator organisms
coliform and E. coli were absent in all treatments and the pathogenic
bacteria Salmonella was also absent in experimental treatments. These
results are acceptable according to ICMSF (1988).
The present research revealed that the application of salt and garlic gave the best result comparing with the other treatment as it retained the more beneficial nutrient property, lower moisture and TVN score, higher Fat and Ca, protein and salt score. The salt used to remove water from the fish body and thus to help the fish through smoking where as the other two Treatment are used not only to remove water from the fish body but also added some nutrients that prevent the growth of moulds and bacteria due to the formation of an unfavorable growth medium but with a good taste. So Treatment 2 may be recommended for table use as a good quality ready food item after some more field trials.
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