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This study aims to develop a pH-functional thin-film sensor for non-invasive measurement of spoilage of packed fish.

At first, polymers of natural origin such as hydroxy(propyl)methyl cellulose, potato dextrose agar and starch alongside a pH sensitive-mixed indicator formulation were used to produce thin film sensor. The developed thin film sensor was tested for monitoring the spoilage of seafood stored at 4°C. Using ultraviolet-visible and Fourier-transform infrared spectroscopy, the halochromic sensor was characterised. In addition, the halochromic response of the thin film was directly correlated to the total volatile base nitrogen emitted by the packaged fish, pH, microbial activity and sensory evaluation.

The results suggested the developed biopolymer-based thin film sensor showed different colours in line with the spoilage of the packed fish, which could be well correlated with the total volatile base nitrogen, microbial activity and sensory evaluation. In addition, the thin film sensors exhibited a high degree of biodegradability. The biopolymers-based thin film halochromic sensor has exhibited excellent biodegradability along with sensitiveness towards the spoilage of the packed fish.

In the future, consumers and retailers may prefer seafood containers equipped with such halochromic sensors to determine the degree of food deterioration as a direct indicator of food quality.

This study aims to describe on-site determination of pH in aquaculture using a portable colorimeter.

A basic and inexpensive portable colorimeter having light sources of different wavelength has been optimized for the determination of pH. A chromic reagent is optimized to develop colors depending on different pHs. Then, the color is measured using portable colorimeter in terms of resistance. Using the resistance to absorbance relationship, the resistance values are converted to absorbance. The performance of the developed colorimetric system is compared with commercially available colorimeter and pH meter. Eighty brackish water aquaculture samples were tested using the developed colorimetric system to check its adaptability in aquaculture farms.

A chromic reagent optimized in this study exhibited linear relationship with the pH changes of pH standards. Portable colorimeter having three different light sources is optimized using this chromic agent for determination of pH. Colorimeter possessing yellow light revealed more linear results than the others. The developed colorimetric system determines the pH of aquaculture water with an accuracy of ±0.14 in comparison with commercial colorimeter at the pH range of 6.0−9.0.

pH plays a pivotal role in aquaculture, impacting not only productivity but also profitability. The colorimetric system introduced in this research is promising for pH measurement in the field of brackish water aquaculture. The on-site pH assessment facilitated by this colorimetric system holds significant potential for adoption within the aquaculture sector, owing to its precision, portability, simplicity of use and user-friendly nature.

This study aims to describe the development of a battery-operated portable colorimeter for on-site determination of water quality in aquaculture.

A simple and economical colorimeter is built using light sources of different wavelength and a light-dependent resistor combined with an electrical circuit. The whole system was fabricated as to fit into the pocket or palm for easy handling. The developed portable colorimeter was calibrated for estimation of nitrite. Further, the performance of developed portable colorimeters was compared with the commercially available colorimeter.

Three colorimeters with different light sources were developed and calibrated for determination of nitrite in water. Among them, colorimeter with yellow light source exhibited higher potential for determination of nitrite in the range of 0.5–3.5 ppm. Further, the results of the developed colorimeter are comparable with the commercial colorimeter.

The portable colorimeter developed in this study exhibits potential for determination of nitrite in aquaculture. Determination of nitrite at low concentrations is important for assessing the quality of culture as well as wastewater in aquaculture industry. The accuracy, portable nature, economy and simple operation of these portable colorimeters offer opportunity for on-site determination of water quality parameters in aquaculture.