Analysis of Thiobarbituric acid and Benzo(α)Pyrene Value of Smoked Nile Tilapia (Oreochromis niloticus) Using Different Liquid Smokes

The purpose of this research was to find the different  influence of corn cob (LS_A) and coconut shells (LS_B) liquid smokes to the changing of thiobarbituric acid (TBA) value, benzo(α)pyrene (BP), organoleptic of the smoked nile tilapia during storage. The result indicated that the smoked nile tilapia which used liquid smoke corn cob had higher organoleptic value than using coconut shells. The result of organoleptic 8.60 (LS_AH₀), 8.24 (LS_BH₀), 8.02 (LS_AH₅), 7.88 (LS_BH₅), 4.91 (LS_AH₁₀), 4.56 (LS_BH₁₀) and were rejected on 10 days storage. The smoked nile  Tilapia which was processed using liquid smoke of corn cob (LS_A) and vacuum packed had higher organoleptic value than those which were processed by liquid smoke of coconut shells (LS_B) along the storage. The different of liquid smoked gave very significant effect to TBA value (P<0.01). The duration of storage gave very significant effect to TBA value (P<0.01). The interaction between liquid smoke and duration of storage gave very significant effect (P<0.01) at 10^th, 5^th days, whereas at 0 day did not give very significant effect (P>0.01). TBA value of smoked nile tilapia using liquid smoke of corn cob (LS_A) higher than using liquid smoke of coconut shells (LS_B) for each storage (LS_AH₀ : 0.76; LS_BH₀ : 0.74; LS_AH₅ : 1.02; LS_BH₅ : 0.95; LS_AH₁₀ : 1.42; LS_BH₁₀ : 1.32). The result on polycyclic aromatic hydrocarbons (PAHs) of smoked nile tilapia using corn cob and coconut shells liquid smoke showed that there was no benzo(α)pyrene detected.

Nile tilapia fish (Oreochromis niloticus) is one of fresh water species which is liked by many countries because it has thick meat, delicious taste and has not cholesterol (Suyanto, 2008). The preservation effect of smoke on fish has been known for many years. The main functions of smoke are to develop aroma, flavour, and colour, to preserve, to create new products, to form a protective skin in emulsion-type and to protect the products from oxidation (Coronado, et al. 2002).

Traditional smoking technique is now being substituted by the use of liquid smoke. Smoke flavourings have been used for ± 50 years as preservative and aromatisers of fish. Liquid smoke have several advantages i.e. : easier to apply uniformity, much cheaper, no environmental pollution and free of harmful compounds such as Polycyclic Aromatic Hydrocarbons (PAHs) (Swastawati, 2007). Finally, liquid smoke of different composition are available and can be combined to obtain products with very different sensory characteristics.

Thiobarbituric Acid (TBA) is one of the most common method used as an indicator parameter of lipid oxidation. TBA value is a measure of malonaldehyde concentration in the sample. Malonaldehyde is often bound to protein and the conditions for its optimal release are often hard to determine (Fernandez, et al., 1997; Shahidi, 1994).

PAHs are generally considered to be carcinogenic compound and, as these also end up in the finished product after smoking, use of the method can be questioned. The carcinogenicity of several PAH compounds is known. The most thoroughly studied PAH compound is benzo (α) pyrene (BP) (Sikorski, 1988).  

This research is aimed to analyze  TBA and BP value of smoke nile tilapia (Oreochromis niloticus) using corn cob and coconut shells liquid smokes.

 Two liquid smoke (LS_A and LS_B) has been used to smoke nile tilapia fish (Oreochromis niloticus). LS_A and LS_B contained similar proportions of chemical compound mainly of phenol derivatives and organic acids

Nile tilapia fish has length about 18 – 23 cm and weight about 120 – 150 gram were obtained from “Barokah fishing area” located in Tembalang-Semarang. The liquid smoke concentration used was 3% (^V/_V) and brine concentration used was 10% (^W/_V). The fish were dipped into brine for 15 minutes and dehydrated in an oven of ± 40-80⁰C for about 5 hours. Each smoked fish was then vacuum packed in an oxygen impermeable bag and stored at room temperature until analysis in 0, 5 and 10 days.

TBA value was determined by the Tarladgis method  (Sudarmadji, et al.,2003), mean while BP value was determined by using LIPI (2000) and Holden and Marsden (1969) methods.  Sensory analysis of fish smoke was determined by using SNI No. 01-2725-2006 and flesh fish sensory analysis was determined by using SNI No. 01-2729-2006. A panel of ten trained panelists performed the product sensory assessment. The quality indicates of smoked nile tilapia fish that were selected in preliminary experiments from the following set : appearance, texture, colour and flavour.

            The mean TBA values of smoked nile tilapia fish the LS_A and LS_B after 0, 5 and 10 days of storage are presented in table 1.

Table 1. TBA value of smoked nile tilapia fish during storage

Note : Average value of  3  times repetition ± standart deviation

^a               :  Very significant effect (P<0.01); means without a letter are not significant effect

A         :     Tilapia fish using corn cob liquid smoke

B         :     Tilapia fish using coconut shells liquid smoke

            TBA values for sample A has higher value than sample B  along the storage (0, 5 and 10 days). The differences were statistically very significant (P<0.01). The duration of storage see very significant effect to TBA value (P<0.01). The interaction between liquid smoke and duration of storage gave very significant effect (P<0.01) at 10^th, 5^th days, whereas at 0 day did not give significant effect (P>0.05).

PAHs constitute a large class of organic substances containing two or more fused aromatic rings made up of carbon and hydrogen atoms. BP was the first PAHs to be identified as carcinogen and as consequence, has been studied most (Simon et al, 2006). The content of PAHs compounds in smoked nile tilapia was slightly difference (Table 2). 

Table 2. PAHs compounds in smoked nile tilapia fish (ppb)

            The result on PAH of smoked nile tilapia using LS_A and LS_B showed that there was no BP detected. Study by Siskos et al (2007) found that traditional cold-smoked rainbow trout fillet (Oncorhynchus mykiss) consits of 3.4 µg (fresh weight) of BP. Meanwhile,  samples treated by liquid smoke ware found free of BP. The acceptable daily intake (ADI) for BP from food was 47 ng/day or 17 µg/year, this means that from a health perspective a person should not eat more than 5 kg of traditionally cold smoked fish annually if fish contains of BP equal amount to 3.4 µg (Hattula et al, 2001).

            Sensory evaluation was a method of trial which using human five senses as the prime devices to measure the acceptance of food. The test of organoleptical quality of flesh nile tilapia was conducted by 10 panelist of fisheries students, Diponegoro University. The evaluation of fresh nile tilapia quality was based on fresh fish organoleptical score sheet SNI No. 01-2729-2006 which had range of value 1-9.

            According to the result of calculation of certainty  interval, it was founded that fresh nile tilapia fish which used in fish smoking had average organoleptical value 8.34 with certainty interval  8.202 < m < 8.518. It was characterized by bright and protruded eyes, clear cornea, gleamed red gill,  clean mucus layer, glisten meat slices, fresh odor, compact consistence and elastic when being pushed by finger (Adawyah, 2007).  Minimum requirement of fresh fish according to Indonesia National Standart SNI No. 01-2729-2006 was 7.

            Organoleptic value of smoked fish was necessary to measure the acceptance of consumer. The evaluation of smoke nile tilapia quality was based on smoke fish organoleptical score sheet SNI No. 01-2725-2006 which had range of value grade 9 (good) to grade 1 (bad).

Table 3. organoleptic value of smoke nile tilapia fish during storage

^a               :  Very significant effect (P<0.05); means without a letter are not significant effect

           

            In general LS_A sample received higher sensory score than LS_B at all times of storage. Research by Ganulalan et al (2003)  showed that smoke by dipping in liquid smoke and brinning mix has influence for panelist accepting sensory.

            Smoking fish processed using different liquid smoke and storage duration gives significant effect toward the change of thiobarbituric acid,  benzo(a)pyrene and organoleptical values. Both corn cob and coconut shells liquid smokes were acceptable by panelist. However, corn cob liquid smoke seems to be more likely by panelist in terms of it’s specific taste. Download full articel here/ disini