Near infrared (NIR) spectroscopy has been proposed as a potential method to analyze different properties in live animals and humans, as infrared light has the ability to penetrate living tissues. This study evaluated the potential use of NIR spectroscopy to identify and analyze beef muscles through the skin nondestructively. The results from this study demonstrated that the NIR region has the potential to noninvasively monitor some properties of meat associated with either fat or muscle characteristics and to differentiate either muscle or fat tissue analyzed through the skin. At present, there are no rapid and noninvasive tools to monitor and assess any characteristic or property in live beef animals. Although these results look promising, more experiments and research need to be carried out before recommending the beef industry using this technology in live animals.
Research in animal feeding and nutrition often requires the evaluation of live animals, postmortem carcass assessment, or meat composition to assess the nutritional value of feeds on animal performance [
Near infrared (NIR) spectroscopy has been proposed as a potential method to analyze different properties in live animals and humans, as infrared light penetrates living tissues [
It has been reported that NIR spectroscopy can detect tissue oxygenation changes in the brain and muscle of humans where the detection of tissue oxygenation is possible because of the relative transparency of biological tissues to NIR wavelengths [
Short wavelengths (SW) in the NIR (700 to 1100 nm; 13,900 to 9400 cm−1) range can penetrate deeply into the skin, offering a potential spectral window for the analysis of animal and human tissues [
One of the main reasons for the low performance in the NIR measurements in living animals is related with the amount of incident light (e.g., reflectance). Using this methodology, light is highly scattered by the complex structure of the skin and its main layers (epidermis (blood-free layer), dermis (vascularised layer with dense irregular connective tissue with collagenous fibers), and hypodermis (subcutaneous adipose tissue layer composed of two sublayers separated by thin connective tissue)) [
This study evaluated the potential use of NIR spectroscopy to analyze muscle and fat characteristics in beef cattle through the skin. The optical properties of tissues analyzed through the skin and the application of pattern recognition methods were used in order to demonstrate the ability of this method to analyze different tissues through the skin.
In order to study the optical properties or spectra of different tissues, two commercial meat cuts, namely, rump (
The diffuse reflectance spectra of the samples were recorded from the flat surface using the purpose built contact probe attached by a fibre optic (10 mm diameter) cable to a Fourier transform (FT) NIR instrument (Antaris II, Thermo, USA). The instrument records spectra with resolution of 1 nm for the wavelength region 14,000–4000 cm−1 (700–2500 nm). Data collection and processing was achieved using the Thermo interface software enabling automation of data collection provided by the Antaris II instrument. The instrument was set to average 10 readings internally for each spectrum saved. A ceramic tile or reference panel provided by the instrument manufacturer was used as a white reference between each measurement.
Spectra were exported from the Thermo software in GRAMS format (
Discrimination models were developed using partial least squares discriminant analysis regression (PLS-DA). The PLS-DA regression technique is a variant of PLS regression, where for each class, a model (
Figure
Second derivative of the average of the near infrared mean spectrum of skin, muscle, fat, skin plus fat, and skin plus muscle.
The most relevant changes were observed in the long NIR wavelength region where differences were observed at 7100 cm−1 (O-H and C-H), 5263 cm−1 (O-H, mainly related with water/moisture), and between 4762–4350 cm−1 (CH combination tones). The same wavenumber range (4762–4350 cm−1) was reported by other authors to be associated with cartilage when pure bovine cartilage samples were analyzed using NIR spectroscopy [
In order to further test and evaluate the interactions between different tissues (skin, muscle, and fat) the NIR spectra were analyzed using PCA (see Figure
Score plot of fat, muscle, skin, skin plus fat, and skin plus muscle samples analyzed using near infrared spectroscopy.
Loadings derived from the PCA used to analyze fat, muscle, skin, skin plus fat, and skin plus muscle samples analyzed using near infrared spectroscopy.
Score plot of fat and skin plus fat in the meat samples analyzed using near infrared spectroscopy.
Loadings derived from the PCA used to analyze fat and skin plus fat in the meat samples analyzed using near infrared spectroscopy.
The PLS-DA models were used to further evaluate the ability of NIR spectroscopy to identify different tissue types analyzed through the skin (see Figure
Partial least squares discriminant analysis of different types of beef tissues analyzed using near infrared reflectance spectroscopy.
All samples
Steak
Rump
Zamora-Rojas et al. [
It is well known that light penetration depth in a specific sample is a function of the geometry of the optical probe, the scattering and the absorption characteristics of the sample [
The results from this study demonstrated that the NIR region has the potential to monitor some beef meat properties associated with fat or muscle noninvasively through the skin. The proposed method would provide beef producers or industry with a powerful tool to monitor more closely the effects of health, nutrition, or product characteristics with the goal of producing a consistently uniform product and maximize profits assuring consumer with a product of high quality. Although these results look promising, more experiments and research need to be carried out before recommending the beef industry to use this technology in live animals.
The authors declare that there is no conflict of interest regarding the publication of this paper.