The human body requires protein to perform some important functions, which makes protein an important nutritional requirement. There has been a recent surge in the demand for its semi-processed forms, mostly as dietary supplements, in urban areas, due to the fast-tracked lifestyle of the majority of the urban population.
The study by Andrade et al. (2019) [1] reported that the consumption of protein-rich nutritional supplements has been increasing over the years to compensate for the increase in protein needs. A popular example of a protein supplement is whey protein (WP) powder. Whey protein, a common by-product of the cheese industry, is a highly bio-available protein source rich in essential amino acids with proven benefits for post-exercise muscle synthesis [2,3], making it a popular choice among consumers partaking in physical activities. The allergenic compound-related limitations of whey protein and an increase in specialized diets, including veganism [4], have led to the emergence of a wide variety of additional protein powders on the market, including pea and beef protein. In ensuring the quality of protein-based foods, such as protein powders, several analytical methods have been explored.
The most common among these are based either on combustion (Dumas) or chemical digestion (Kjeldahl), techniques capable of assessing protein concentrations in food products based on their total nitrogen (N) content. These methods have been proven to have problems when it comes to accuracy since they evaluate the so-called apparent protein content based on the sample’s total nitrogen content, not specifically nitrogen derived from proteins.
Reports for protein sources adulteration have been on the increase with the conversional methods being unable to detect the adulterants. A typical example is the use of melanine (C3H6N6) in many countries, including China in the production of raw milk, infant formula and cereal-based products. This adulterant is difficult to detect using the conversional means since it contains 66.6 % nitrogen and so can mimick proteins and escape being detected. Melanine therefore has been used as an adulterant to increase protein content whilst in reality results in consumers getting proteins below the recommended intake.
This and many more cases necessitates the development of models that can detect and quantify the actual concentration of proteins and be able to detect adulterants in protein based products.
Affordable alternative approaches with better sensitivities are required. An example of a non-sophisticated technique that can serve as an alternative approach to the total nitrogen determination methods is near infrared spectroscopy (NIRS). Generally, the NIRS technique measures the intensities of absorptions of radiation while NIR light passes through a sample.
FTIR is another technique that can be used in adulterant detection. When the infrared light from the light source passes through a Michelson interferometer along the optical path, it is called Fourier transform infrared spectroscopy (FTIR) [5]. FTIR spectroscopy is based on interferometry and makes use of the complete source spectrum rather than recording the spectra at the individual wavelengths that can be generated by grating or prism systems used in conventional near-infrared spectroscopy [6]. DLP-based spectrometers which is a third technique includes a digital micromirror device (DMD) and a single-point detector for wavelength selection, making them more suitable for portable designs than spectrometers with conventional linear array detectors [7].
This study aimed to assess the performance of three benchtop and one handheld NIR instruments with two different sample presentation methods for the rapid detection and quantification of multiple adulterants in whey, beef, and pea protein powders. The aim was also to prepare a solid groundwork for future developments, including the building of more generalized and potentially transferrable predictive models to support the quality control of multiple types of protein powders.
Whey, beef, and pea protein powders were mixed with a different combination and concentration of high nitrogen content compounds—namely melamine, urea, taurine, and glycine—resulting in a total of 819 samples. NIRS, combined with chemometric tools and various spectral preprocessing techniques, was used to predict adulterant concentrations, while the limit of detection (LOD) and limit of quantification (LOQ) were also assessed to further evaluate instrument performance.
Out of all devices and measurement methods compared, the most accurate predictive models were built based on the dataset acquired with a grating benchtop spectrophotometer, reaching R2P values of 0.96 and proximating the 0.1% LOD for melamine and urea. Results imply the possibility of using NIRS combined with chemometrics as a generalized quality control tool for protein powders.
Was this post useful?
Yes
No
Bình luận