Bent Fiber Sensor for Preservative Detection in Milk

Optical sensor response towards hydrogen peroxide in low fat and full cream milk

Fiber Optic Displacement Sensor (FODS) categorized as one of the optical sensor based reflective intensity modulation. An intensity based sensor have been widely used in detecting various substances due to their simplicity structures. Generally for sensing principle, a pair of fiber is used to construct FODS which one of optical fiber is the transmitting fiber and another one is receiving fiber. The objective of this current work is to introduce FODS to evaluate the optical response in terms of voltage reading at different concentration of hydrogen peroxide in two different types of milk. A real-time measurement, low cost, stability, high sensitivity and simplicity of design promote a well-developed sensor in providing useful parameters in detecting hydrogen peroxide in milk. Hydrogen peroxide is an adulterated agent added in milk that can harm the consumers. Transmitive optical sensor as a function of displacement technique was developed to study the hydrogen peroxide concentrations in the range of 0 %-10 % as consuming more than 3-10 % of hydrogen peroxide can cause mild allergies reactions, stomach upset and vomiting. The output from the receiving fiber in this designated system was measured in terms of voltage reading through multimeter. The sensor shows outstanding performances of delivering 0.0007 V/% sensitivity for low fat milk and with linearity of >98 %. Whereas, the sensitivity achieved for full cream milk was 0.0005 V/% with a good linearity >97 %. The simplicity and credibility of this system offer a good opportunity in this project and also foods industry applications.

A Review on Recent Sensing Methods for Determining Formaldehyde in Agri-Food Chain: A Comparison with the Conventional Analytical Approaches

Formaldehyde, the simplest molecule of the aldehyde group, is a gaseous compound at room temperature and pressure, is colorless, and has a strong, pungent odor. It is soluble in water, ethanol, and diethyl ether and is used in solution or polymerized form. Its maximum daily dosage established by the EPA is 0.2 μg g−1 of body weight whereas that established by the WHO is between 1.5 and 14 mg g−1: it is in category 1A of carcinogens by IARC. From an analytical point of view, formaldehyde is traditionally analyzed by HPLC with UV-Vis detection. Nowadays, the need to analyze this compound quickly and in situ is increasing. This work proposes a critical review of methods for analyzing formaldehyde in food using sensing methods. A search carried out on the Scopus database documented more than 50 papers published in the last 5 years. The increase in interest in the recognition of the presence of formaldehyde in food has occurred in recent years, above all due to an awareness of the damage it can cause to human health. This paper focuses on some new sensors by analyzing their performance and comparing them with various no-sensing methods but focusing on the determination of formaldehyde in food products. The sensors reported are of various types, but they all share a good LOD, good accuracy, and a reduced analysis time. Some of them are also biodegradable and others have a very low cost, many are portable and easy to use, therefore usable for the recognition of food adulterations on site.

A derivatization and microextraction procedure with organic phase solidification on a paper template: Spectrofluorometric determination of formaldehyde in milk

A derivatization and air-assisted dispersive liquid-liquid microextraction procedure with organic phase solidification on a paper template was developed for the first time. The procedure was used for the spectrofluorometric determination of formaldehyde in milk samples. The Hantzsch reaction of formaldehyde with acetylacetone in the presence of ammonia to form a derivative (3,5-diacetyl-1,4-dihydrolutidine) was implemented for the microextraction and detection of analyte. Thymol was investigated as the extraction solvent for the air-assisted dispersive liquid-liquid microextraction for the first time. In the developed procedure, molten thymol was added to the thermostated aqueous sample solution containing reagents for formaldehyde derivatization, and cloudy solution of fine thymol droplets was formed by air bubbling. After separation of phases the liquid extract phase was withdrawn with a dispenser and distributed on the black paper template in a thin layer to be solidified. The solidified extract phase on the template was inserted to a sample holder of a spectrofluorometer and fluorescence intensity was measured without using cuvettes. Under optimal experimental conditions the linear detection range was found to be 45-500 µg L^-1 with LOD calculated from a blank test, based on 3σ, 15 µg L^-1. The developed procedure does not require the dilution of the solid extract phase in organic solvent to be introduced in an analytical instrumentation and the use of cuvettes for spectrofluorometric detection.