Rancidity Test through TBA levels of Tilapia Fish Fillet Chips

3.1.3. Rancidity Test through TBA levels of Tilapia Fish Fillet Chips

One factor determining the quality of food containing oils or fats include the emergence of a number Thiobarbituric acid (TBA). TBA number will show the rancidity level. Smell rancid mainly due to the formation of aldehyde or ketone in the stored food. In TBA, rancidity occurs in fat because of the emergence of detectable aldehydes as malonaldehyde (Slamet Sudarmadji et al. , 1996), as Malonaldehyde is the result of lipid oxidation (Anton Apriyantono et al. , 1989). Analysis result of TBA test of Tilapia Fish Fillet Chips during the storage shown in Figure 4.

Average TBA interaction number between rice and tapioca flour formulation and storage time ranging from 1.106 - 2.279 mg / kg malonaldehyde. In figure 4, the different formulation mixture of rice flour and tapioca flour as the dough pads of tilapia fish fillet chips, has no effect on the TBA numbers, and the average value of the levels of TBA in the formulation: R100T0, R80T20 and R70T30 row is 1.677;

1.71 and 1.621 mg / kg of malonaldehyde. But with the increasing storage time from

3.6 and 9 weeks will increase TBA levels, a row of 1.344; 1.545 and 2.12 mg/kg of malonaldehyde. Watts (1962) in Febrina (2012) said that limits value of TBA in foods is 1-2 mg / kg (Siti Nur Sayang and Abustam, 20013 in http://repository.unhas.ac.id/.../ARTIKEL%20SYG.doc?...2 ). Based on the TBA levels, it means that chips product began to show rancidity in storage at least 9 weeks. In this research, chips storage is done in polyethylene plastic bag and sealed using a sealer, to delay rancidity up to 9 weeks. Research of Eko Nurcahyo

Sept ember 8 th – 9 th 2015, Facult y of Biot echnology – Universit as At ma Jaya Yogyakart a

Dewi and Ratna Ibrahim (2008, in http://eprints.undip.ac.id190821EKO_Nur.pdf ) in tilapia fish beef jerky is packed in Vacuum container compared with polyethylene plastic bag for storage of 30 days, the polyethylene plastic is not able to prevent the growth of aerobic bacteria, means that packaging is not able resist oxidation. This is evidenced by the increasing number of total bacteria of 4.784 log colony / gram (at 0 day) to 5.195 log colony / gram after stored for 30 days. This shows that the plastic bag that still contain oxygen in the bag, so that allow the oxidation of fat or oil in the product.

Fatty meat fish contains 17-21% saturated fatty acids and 79-83% unsaturated fatty acids. The high content of unsaturated fatty acids cause the fishery products easily oxidized (Rahayu, et al. , 1992 in Evi Susilowati, 2005. http://repository.ipb.ac.id bitstream.....16500...A02esul....pd.). The big oxidation process mainly happen during material processing (filleting, seasoning until frying in high temperature) until before the product is packed. The frying step in this research took place at a high temperature (185°C-190°C) for ± 15 minutes. This process is one of the processes that trigger rancidity, especially it happens on food containing high unsaturated fatty acids. (Mudjajanto, 1991 in Evi Susilowati, 2005. http://repository.ipb.ac.id bitstream.....16500...A02esul....pd). The air oxygen in contact with tilapia fish fillet chips during frying, and the heat will attack the double bond in unsaturated fatty acids to form peroxides. The peroxides leads to fat or oil oxidation to produce the aldehyde (Ketaren, 1986) in the form of malonaldehyde which can be detected by TBA numbers (Slamet Sudharmaji, 1996). Rancidity process continues in plastic bag, because the plastic bag that do not vacuum still allows contain oxygen in the packaging.