Analysis of formalin content in marketed fish sample and development of a suitable removal technique

Abstract

Fish is an important food stuff and source of protein all over the world. In Bangladesh fisheries sector contributes a lot in case of earning foreign currency and meeting domestic need of animal protein. There has been a lot of controversy around the various poisons finding their way into our food. Use of formaldehyde on marketed fish is a very common practice in Bangladesh to preserve fish. Formaldehyde has serious harmful effect on public health including cancer, kidney failure and others diseases. The study was performed to determine the presence of formaldehyde on marketed fish as well as develop a removal technique of the formaldehyde from fish. The use of the Nash test, in conjunction with TCA extraction, for measuring formaldehyde in fish muscle is one of the most qualitative methods. This was done by means of a "recovery factor" which took into consideration the percent of formaldehyde added to the muscle extracted by the TCA solution. The percentage of added formaldehyde that was recovered varied with variations in the procedures used in preparing the muscle, making the extract, and carrying out the Nash test. In this study I used formalin kit to detect the presence of formaldehyde in different fish species and samples of each species those were collected from different places. I found that Bata, Tilapia, Rui fishes contain formaldehyde ranging from (5.26 to 1.88) mg per 10gm sample. By using only vinegar, we can remove 60 to 99 percent of formaldehyde content from some species as well as by using vinegar and heat we can remove 98 to 99 percent of formaldehyde content from other species of fish. In this study we also performed control test to check the amount of formaldehyde that produced naturally in the preserved fish. In case of Shorputi and Rui the amount was 0.098 and 0.084 mg per 10 gm sample. The present study suggested that fish from wet market contained a certain amount of added formaldehyde and fishes from both freshwater and marine sources shows to contain natural occurring formaldehyde in their muscle at different concentration. The present study also suggested that major portion of the formaldehyde in fish muscle can be removed through vinegar and heat. This research is very beneficial for the society in terms of public health and food safety.