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Continental J. Fisheries and Aquatic Science 4: 44 - 46, 2010 ISSN: 2142 - 4246 © Wilolud Journals, 2010. http://www.wiloludjournal.com

COMPARATIVE DETERMINATION OF TRIMETHYLAMINE IN FRESH FISH (HALIBUT, MUDFISH AND TILAPIA)

1 V.O. Aina, 2Hauwa Haruna M.S and 3Amina Zakari Department of Applied Sciences, College of Science and Technology, Kaduna Polytechnic, P.M.B 2021,

Kaduna – Nigeria

ABSTRACT An investigation was carried out to determine the concentration of trimethylamine (TMA) in halibut, mudfish and tilapia purchased from fishermen in their live forms at River Kaduna in Kaduna State. Ashing method of analysis was carried out in which 100g of each of the fish was taken at three (3) h interval to twelve (12) hrs. It was observed that the concentration of trimethylamine of each 100g dry weight of halibut, mudfish and tilapia at zero (0) hrs of harvesting was undetectable. After 3-12hrs of storage, the trimethylamine (TMA) level in halibut rose from 6.53mg to 12.33mg, in mudfish, TMA level rose from 5.74mg-9.0mg, while in Tilapia, TMA rose from 4.64mg-8.12mg. KEYWORDS: Trimethylamine (TMA), Tilapia, Fishermen, Ethylamineoxide (TMAO), Flavobacterium Perishability

INTRODUCTION Fish contribute the major amount of protein as meat, the substance (protein) replaces worn out tissues and promote growth. The fat contained in fish is mainly polyunsaturated and believed to assist in preventing coronary heart diseases. Fish have a storage or shelf life of a few hours to a few days when outside it’s natural habitat. This is caused due to changes occurring from within the fish that causes quality decline by deterioration followed by spoilage (John, 1990). Therefore, most fish flesh are considered more perishable than meat because of more rapid autolysis by the fish enzymes. Fish contain high concentration of Trimethylamineoxide in their flesh, when it does, microorganisms breakdown this compound into trimethylamine, which is an odour precursor that contribute to the characteristic smell of bad fish, also resulting in the change of the texture and the colour. The consumer of such fish containing toxic substances such as trimethylamine may suffer from food intoxication such as diarrhea, abdominal cramps, fever, vomiting, nausea, fibrosis and botulism (Gaman 1981). Fish flesh contain between 0.2 – 2.0 % trimethylamineoxide. After death, some spoilage microorganisms utilize the trimethylamineoxide as terminal electron accepter under anaerobic condition resulting in the production of trimethylamine. Thus reducing the reliability of trimethylamine as a spoilage indicator. (CH3)3 – N = O (CH3)3 – N + HCHO Trimethylamineoxide Trimethylamine Formaldehyde Certain bacteria are known to cause fish spoilage namely Acenotobacteria, Acetomonas, Altromonas, Clostridium, Cyanobacterium, Aspergillus, amongst others. There spoilage bacteria first utilize the simple compound and in the process releases various volatile components (Shewan, 1992). Trimethylamineoxide, creatinine and taurine are decreased during fish spoilage with the production of trimethylamine, ammonia, hydrogen sulphide, indole which contribute to the characteristic smell of spoilt/bad fish (James, 1992). Various kinds of fish differ considerably in their perishability. Fats and oils of many kinds of fish are composed of unsaturated fatty acids and hence are subjected to oxidative changes producing oxidative rancidity and sometimes undesirable changes. Anti oxidants may be applied as dip coatings and glazes. These methods are used for temporary storage (Frazier, 1978) the consumer of spoilt fish containing the toxic substances such as trimethylamine suffer from food poisoning such as Botulism, Vibriosis, amongst others. AIMS AND OBJECTIVES

1. The aim of this research is to determine and compare trimethylamine (TMA) in three species of fish namely; halibut, mudfish and tilapia.

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V.O. Aina et al.,: Continental J. Fisheries and Aquatic Science 4: 44 - 46, 2010

2. The analysis will establish the keeping qualities of these fishes and finally, to advice fish users especially the marketers on how best to handle and preserve them.

MATERIALS AND METHODS Three different fish samples namely halibut, mudfish and tilapia purchased from River Kaduna were used for this research work. They were slaughtered at the same time in order to obtain accurate results. 100g of each sample were taken and at 3 hourly interval the weights were noted at four different times intervals the external changes being noted. The Trimethylamine (TMA) levels were estimated by the method described by (Mamman et al, 2000). 100g each of the sampled fish were minced with a manual grinder, diluted with 200ml 7.5% trichloroacetic acid, centrifuged at 5000 rpm until supernatant was clear. 3ml aliquot of supernatant was collected into a glass stopper test tubes and diluted with 1ml HCl, 4ml formaldehyde, 10mls anhydrous toluene, 3mls potassium carbonate and 5mls picric acid and transferred to a uv double – beamed spectrophotometer cell and absorbance read to 410nm against a blank. The same procedure was also done for the standard and absorbance read at 410nm. Calculation The concentrations of trimethylamine were determined using the formula. Where A = absorbance of sample, A1 = absorbance of standard, 300 = approximation of total supernatant RESULTS AND DISCUSSION Table 1: Concentration of Trimethylamine in Halibut, Mudfish and Tilapia CONCENTRATION OF TRIMETHY-LAMINE (TMA) IN Mg DRY WEIGHT TIME(h) HALIBUT MUDFISH TILAPIA 0 3 6.53 5.74 4.64 6 8.12 6.28 5.55 9 9.12 6.53 6.05 12 13.32 9.00 8.12 Table 1 depicts the concentration of Trimethylamine (TMA) in Mg Dry weight for the three species over a time range of 0-12hr. TABLE 2: OBSERVED SUCCESSION OF EXTERNAL CHANGES OCCURING IN HALIBUT, MUDFISH AND TILAPIA TIME HALIBUT MUDFISH TILAPIA 0hr Bright, fresh and seaweed odour Bright , fresh and seaweed

odour Bright , fresh and seaweed odour

3hr Swollen flap on the skin Swollen gills on the skin Swollen gills and flaps on the skin

6hr Brown discolouration observed with release of sickly sweet odour

Colour of skin faded eye sunken cloudy pupil and opague cornea

Skin colour of fish faded, eyes sunken pupil cloudy and opague cornea

9hrs Softened fleshy juice with light pink gills

Softened fleshy juicy with a muddy odour

Hardness of skin remains the same

12hrs Flesh is extremely soft, reddish brown discolouration with a pungent odour

Stale fishy odour perceived Juicy with a stale fishy colour

Mg TMA/100g Sample = A1 x mg TMA/ml Std solution x 300

A ml of aliquot of sample used

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V.O. Aina et al.,: Continental J. Fisheries and Aquatic Science 4: 44 - 46, 2010 Table 2 depicts the observed succession of external changes occurring in Halibut, Mudfish and Tilapia over a time range of 0-12hr. Mamman et al (2000) stated in a fresh fish, the concentration was usually less than 3mg per 100g fresh weight, for a spoilt fish, the concentration was usually greater than 8mg per 100g fresh weight, while a value of 5mg per 100g could be taken as an indicator of doubtful quality. It was observed that fish flesh was easily perishable and the concentration of trimethylamine increases with storage time. Therefore, it is recommended that fish should not be stored beyond three hours if the freshness must be preserved. The quality of the fish should be preserved by thorough cleanliness and hygiene in handling fish when caught. Preservative method such as freezing, chilling, use of antioxidants, drying, smoking and canning should be employed spoilt fish should be rejected and there should be selection of uncontaminated fish by fish users. The concentration of trimethylamine (TMA) in halibut, mudfish and tilapa increase linearly with time, halibut showed the highest concentration of TMA, while tilapia showed the least. This showed that halibut had a shorter shelf life than mudfish and tilapia and tilapia can be stored for a longer period than halibut and mudfish. As concentration of trimethylamine increases, spoilage sets in which showed that trimethylamine is a good index for spoilage. REFERENCES Frazier, A.I. (1978): Food Microbiology 1st Ed. Bill and Boom Publisher, London Pp 243 – 244 Gaman, P.M. (1981): The Science of Food 2nd Ed. Pergmon Publisher, Brisbane Pp. 207. James, M.J (1982): Modern Food Microbiology 3rd Ed. CBS Publishers,Sydney Pp. 227 – 228, John, D.K (1990): Nutrition Almanac Revised Ed. Mc-Graw-Hill Publishers, London Pp. 8 – 9. Mamman O.A, Aliyu, H. and Sagir, M (2000): Practical Mammal on Food Technology and Dietetic for Schools and Industries 1st Ed, National Science and Technology forum Publication Pp. 225 – 226. Received for Publication: 28/09/2010 Accepted for Publication: 18/10/2010 Corresponding Author V.O. Aina Department of Applied Sciences, College of Science and Technology, Kaduna Polytechnic, P.M.B 2021, Kaduna – Nigeria E-Mail: Vocwummi 2006@Yahoo.Com.