4.5 Ability for detection of volatile amine of BP extract-entrapped PVA films
The ability to diagnose the presence of NH3 of BP extract-entrapped PVA film was investigated. The response of the BP extract-entrapped PVA films to NH3 in terms of their color change was measured using a colorimeter (CIELAB system) and calculated the total color difference (∆E) according to ASTM D2244-09b. The NH3 solution was prepared at four different concentrations (0.01, 0.05, 0.1 and 1.0 M).
Figure 4.14 shows the color response of BP extract-entrapped PVA film toward various concentrations of NH3 (1.0, 0.1, 0.05 and 0.01 M) at ambient conditions. The BP extract-entrapped PVA films changed the color from blue to green in response to NH3 exposition. The results indicated that the BP extract-entrapped PVA films have a potential for use as a seafood spoilage indicator.
The detection limit was found to be 0.01 M of ammonia solution. The vapor – liquid equilibrium in close- container reached after 60 minutes and the color of films remained stable. As can be seen in figure 4.14 a. (1.0 M ammonia solution), the response time of the films to ammonia vapor was apparent within 5 minutes. At high concentration, BP extract-entrapped PVA films response to presence of NH3 vapor faster than low concentration of NH3. The response time of the films was found to depend on the establishment of sample steady state condition in the container and the relative humidity. However, in the closed package environment, both of these factors are constant.