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Impedance is a complex Cartesian function describing the difference between an inputting and exiting sinusoidal electrical signal.  It can be depicted graphically as a plot (vector) of resistance vs reactance.  The linearity of this plot, and the angle of the vector, are distinctive.  In a sample of meat or fish, impedance is affected by the cell structure and the water content.  Both of which are an indicator of freshness.  An impedance sensor, comparing the result with a “normal” database, can therefore be used to detect unfresh meat or meat that has been prior frozen and defrosted without declaration.

This review (open access) describes published applications, comparing the technique with other approaches such as HADH Enzyme measurement (see FAN method explainers).  It concludes that the development of Impedance Sensor methods is now at a stage where the technique is ideal as a cheap, non-destructive inline check in the food industry, particularly if coupled with machine learning to spot unusual or anomalous samples.

Photo by Victoria Shes on Unsplash

Water-injected meat leads to microbial growth risk, as well as being economic fraud.

In this study (purchase required) the authors designed and tested a colorimetric porous polymer microneedle patch to detect added water.  Microneedle patches consist of hundreds to thousands of tiny needles, usually only tens to hundreds of microns long, which can extract tissue fluids and transport the extracted molecules to the backing layer for colour displaying. There is no need for sample preparation and often no need to open the packaging.

In this case, detection was designed and prepared using photopolymerization of an acrylate monomer with a porogen substrate and cobalt (II) chloride as colour change indicator and tartrazine as the reference. The colour of the microneedle patch changed from green to yellow with increased moisture concentration.

The authors reported that this discoloration trend of the microneedle patch during the moisture measurement of meat was very regular. The moisture measurement of meat in range of 66.9 %–75.7 % exhibited a good linear dependence on RGB values. The results indicated that the microneedle patch can visually determine the moisture content of meat in 3 minutes. It can be combined with a smartphone as a quantitative reader.

Photo by Philippe Zuber on Unsplash

A study conducted by Universidad Nacional Autonoma de Mexico (UNAM) researchers found traces of dolphin meat in three out of 15 samples of tuna cans on sale in Mexico. 

Lead researcher Karla Vanessa Hernendez Herbert used DNA probes with polymerase chain reaction (PCR) to identify dolphin meat adulteration.

The full report has yet to be published in a journal, but the Herbert and Professor Francisco Montiel Sosa disclosed the results in an interview with Mexican newspaper, Excelsior. The original article can be read here in Spanish., or a summary of the article from SeafoodSource can be found here.

Animal origin food products, including fish and seafood, meat and poultry, milk and dairy foods, and other related products play significant roles in human nutrition. However, fraud in this food sector frequently occurs, leading to negative economic impacts on consumers and potential risks to public health and the environment. Therefore, the development of analytical techniques that can rapidly detect fraud and verify the authenticity of such products is of paramount importance.

Traditionally, a wide variety of targeted approaches, such as chemical, chromatographic, molecular, and protein-based techniques, among others, have been frequently used to identify animal species, production methods, provenance, and processing of food products. Although these conventional methods are accurate and reliable, they are destructive, time-consuming, and can only be employed at the laboratory scale. On the contrary, alternative methods based mainly on spectroscopy have emerged in recent years as invaluable tools to overcome most of the limitations associated with
traditional measurements. The number of scientific studies reporting on various authenticity issues investigated by vibrational spectroscopy, nuclear magnetic resonance, and fluorescence spectroscopy has increased substantially over the past few years, indicating the tremendous potential of these techniques in the fight against food fraud.

This manuscript reviews the state-of-the-art research advances since 2015 regarding the use of analytical methods applied to detect fraud in food products of animal origin, with particular attention paid to spectroscopic measurements coupled with chemometric analysis. The opportunities and challenges surrounding the use of spectroscopic techniques and possible future directions are also be discussed.

Read full paper here.

Researchers in Ireland have published a paper which discusses current and evolving techniques to determine geographical origins of meat. The paper explores applications of meat authenticity techniques including spectrscopy, stable isotope ratio analysis, and the measurement of compounds derived from the animals' diets. The authors also discuss challenges in interpretation of the data.

Read the abstract here.

A new meat species authentication method designed for Halal food verification has been developed by scientists at the University of Münster, using a  SCIEX QTRAP^® 6500 LC-MS/MS system. BusinessWire reports that the method that can detect multiple species simultaneously.

Read the original article >>>