Formalin-testing kit for seafood

27Oct 2017

       Formalin is known as embalming solution, which is commonly used to preserve dead bodies. With this known property, the solution has been illegally used to preserve vegetables and meat. Formalin is thus usually found in fresh seafood, vegetables, and meat. Too much residue of formalin could cause harm to consumers. Some of the symptoms are irritation inside the mouth and throat. In some cases of hypersensitivity, formalin can cause headache, difficulty breathing, and tightness in the chest. Contact with formalin at 2-10% concentration can cause skin infection. Moreover, formalin can also cause cancer in human.

       For this reason, it is necessary to test formalin in food. Most popular method is Chromatography technique. However, this technique is limited since it requires expensive equipment that is not only large and high-maintenance but also requires a skilled technician to analyze the result. The formalin-testing kit is thus invented to reduce the cost, easy and convenient to use, and portable. The kit relies on reaction between formalin and appropriate reagent, Pararosaniline. The reaction between formalin and Pararosaniline yields a color visible to the naked eyes. Quantitative analysis could also be conducted through Spectrophotometer, to test light absorption, which is easy to do, commonly available in any lab, and not as expensive as other tools.

Principles and methods to measure formalin

       The kit relies on reaction between formalin and Pararosaniline which yields purple color visible to the naked eyes. Meanwhile, quantitative analysis can be achieved through Spectrophotometer by measuring absorption of light with 580-nanometre wave length (measuring procedure shown in picture 1). The reading of light absorption and darkness of the color increase as the formalin concentration increases (picture 2).

       The kit can measure formalin between 5.0 to 200 micromolar concentration, but presents limitation when measuring at 4.0 micromolar concentration.

Picture 1 Formalin testing procedures

Picture 2 Change of colors yielded by the kit at different formalin concentration

Application of formalin-testing kit

       The application of the kit to test formalin in various seafood samplings offer results that do not differ from results provided by the standard method of HPLC (table 1). However, in comparison, the kit can easily be used directly by the consumer and offers fast result, not needing any expensive tools.

Table 1 shows analysis of formalin in seafood samples through the kit and standard method of HPLC

Sample

Formalin-testing kit
(micromolar)

Standard method (HPLC)
(micromolar)

Cephalopod-1

unmeasurable

3.93±0.01

Cephalopod-2

unmeasurable

0.52±0.01

Salmon-1

7.37±0.16

7.19±0.01

Salmon-2

5.95±0.29

6.02±0.01

Octopus

7.24±0.76

7.15±0.01

Pancacias

unmeasurable

1.54±0.01

Black pomfret-1

6.94±0.27

7.08±0.04

Black pomfret-2

4.04±0.21

4.22±0.01

White pomfret

5.71±0.46

5.48±0.01

Scomberoforus

8.82±0.80

8.64±0.01

Sample of seafood tested for formalin

       Outstanding characteristics of formalin-testing kit Formalin-testing kit is easy to prepare, convenient to use, low-cost. It can measure formalin both qualitatively and quantitatively. The resulting color can be observed by naked eyes. The concentration of formalin can be easily measured via Spectrophotometer without using any expensive tools. Therefore, any consumers can use the kit and does not have to rely on a skilled technician.

Assoc. Prof. Dr. Proespichaya Kanatharana and Asst. Prof. Dr. Opas Bunkoed
Trace Analysis and Biosensor Research Center, Faculty of Science, Prince of Songkla University
E-mail: proespichaya.k@psu.ac.th
Source : http://rdo.psu.ac.th/


Research and Development Office, Learning Resource Center Building,Floor. 11 - 12, Prince of Songkla University, Hat Yai, Songkhla 90110 Tel. 0-7428-6940-67, Fax 0-7428-6961 E-mail: rdo@group.psu.ac.th