A simple and fast method for discrimination of phage and antibiotic contaminants in raw milk by using Raman spectroscopy

Abstract

Phage and antibiotic in raw milk poses significant risks for starter culture activity in fermented products. Therefore, rapid detection of phage and antibiotic contaminations in raw milk is a crucial process in dairy science. For this purpose, a preliminary novel method for detection of phage and antibiotic was developed by using Raman spectroscopy. phages and ampicillin which are quite important elements in dairy industry were used as model. The phage and antibiotic samples were added to raw milk separately, and Raman measurements were carried out. The obtained spectra were processed with a chemometric method. In this study, it has been demonstrated that the presence of phage has a titer sufficient to stop the fermentation (10 pfu/ml), and antibiotic in a concentration which inhibits the growth of starter cultures (0.5 µg/ml) in raw milk could be discriminated through Raman spectroscopy with a short analysis time (30 min).

Raman spectroscopy in the quality analysis of dairy products: A literature review

“…In the Raman spectra of milk tetracycline solutions, as shown in Figure 6, the bands at 1322 and 1621 cm À1 were assigned specifically to tetracycline vibrational modes. No changes in the spectral profile and the position of the bands were observed in the spectra within the F I G U R E 5 PCA score graph for Raman spectra of raw milk samples containing bacteriophage, antibiotic, and white [19] F I G U R E 6 SERS spectrum of milk tetracycline in seven different concentrations [20] same concentration levels, which indicated a consistent and reproducible SERS detection. Figure 6 also shows that the intensities of the 1322-and 1621-cm À1 bands were attenuated with the decrease in the tetracycline concentration, and the 1621-cm À1 band was not visible below a concentration of 0.1 ppm.…”

“…Furthermore, in addition to determining the milk components, Raman spectroscopy can be used to discriminate between the presence of antibiotics and contaminants according to Acar‐Soykut and coworkers [ 19 ] who used Raman spectroscopy for rapid discrimination of contamination by phages (viruses that infect bacteria) and antibiotics in raw milk. According to the authors, phages and antibiotics are among the factors that hinder the quality of fermented dairy products.…”

“…A strong band at 483 cm −1 had already been assigned to the δ(HCC) + δ(CCN) (lactam) + δ(CNCO) + δ ip (lactam) in the ampicillin molecular structure, according to Acar‐Soykut and coworkers. [ 19 ] After identifying these bands, the PCA was used to discriminate the milk samples with phages and antibiotics, as shown in Figure 5. The graph was represented with the first main component that explained 20.01% of the total variance and the second main component that explained 15.54% of the total variance.…”

“…PCA score graph for Raman spectra of raw milk samples containing bacteriophage, antibiotic, and white [ 19 ] …”

Characterization of Heterogeneity and Dynamics of Lysis of Single Bacillus subtilis Cells upon Prophage Induction During Spore Germination, Outgrowth, and Vegetative Growth Using Raman Tweezers and Live-Cell Phase-Contrast Microscopy

“…Raman spectroscopy has been applied for characterization of bacteriophage by Thomas et al , Laser tweezers Raman spectroscopy or Raman tweezers, − has also been used to observe the lysis of individual Escherichia coli cells in an optical trap caused by temperature induction of λ prophage and external lysozyme . Raman spectroscopy has also been used to identify phage in cows’ milk, where phage can negatively affect subsequent bacterial fermentations . Although some Raman spectral and light scattering changes were observed in single-lysing cells in previous experiments, the heterogeneity in the dynamic changes in Raman spectra or cell length during prophage-induced lysis was not characterized for multiple individual cells in a population.…”