Continuous gradient temperature Raman spectroscopy (GTRS) is a simple, rapid technique for determining the unique structures of fatty acids, triacylglycerols and phospholipids. Improved lipid spectra and vibrational assignments have many applications in food safety and quality. Herein we analyze the residual lipid components in porcine and poultry meat and bone meal (MBM) collected directly from rendering operations. We are developing a rapid throughput GTRS method that requires no special extraction methods or toxic/expensive solvents, and can be adapted to field use. Crude ethanol, methanol and water extracts of pork, poultry samples and 20:80 pork:poultry MBM were investigated from -100 to 80°C. GTRS provides 20 Mb three-dimensional data arrays with 0.2°C increments and graphical first and second derivatives. Comparison of second derivative data showed good reproducibility among samples, with some vibrational modes distinct for either pork or chicken. The 20:80 pork:poultry data showed for the first time that lipid prepared from mixed MBM can be positively identified. Oil from pollack waste was also examined. GTRS and other methods can easily identify pure fishmeal or fishmeal mixed into terrestrial MBM; fishmeal is distinguished by its long-chain polyunsaturated fatty acid content. The analytical challenge is to determine economic or accidental adulteration whereby porcine, bovine or ovine MBM are mixed with each other, or mixed into poultry or fish meals.
Many issues occur when microbial bacteria contaminates human food or water; it can be dangerous to the public. Determining how the microbial are growing, it can help experts determine how to prevent the outbreaks. Biofilms are a tightly group of microbial cells that grow on living surfaces or surrounding themselves. Though biofilms are not necessarily uniform; when there are more than one type of microbial bacteria that are grown, Raman mapping is performed to determine the growth patterns. Depending on the type of microbial bacteria, they can grow in various patterns such as symmetrical or scattered on the surface. The biofilms need to be intact in order to preclude and potentially figuring out the relative intensity of different components in a biofilm mixture. In addition, it is important to determine whether one biofilms is a substrate for another biofilm to be detected. For example, it is possible if layer B appears above layer A, but layer A doesn’t appear above layer B. In this case, three types of biofilms that are grown includes Listeria(L), Ralstonia(R), and a mixture of the two (LR). Since microbe deposits on metal surfaces are quite suitable, biofilms were grown on stainless steel surface slides. Each slide was viewed under a Raman Microscope at 100X and using a 532nm laser to provide great results and sharp peaks. The mapping of the laser helps determine how the bacteria growth, at which intensity the bacteria appeared in order to identify specific microbes to signature markers on biofilms.
The structural, cognitive and visual development of the human brain and retina strictly require long-chain polyunsaturated fatty acids (LC-PUFA). Excluding water, the mammalian brain is about 60% lipid. One of the great unanswered questions with respect to biological science in general is the absolute necessity of the LC-PUFA docosahexaenoic acid (DHA; 22:6n-3) in these fast signal processing tissues. A lipid of the same chain length with just one less diene group, docosapentaenoic acid (DPA; 22:5n-6) is fairly abundant in terrestrial food chains yet cannot substitute for DHA. Gradient Temperature Raman spectroscopy (GTRS) applies the temperature gradients utilized in differential scanning calorimetry to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur near and at phase transitions. Herein we apply GTRS to DPA, and DHA from -100 to 20°C. 20 Mb three-dimensional data arrays with 1°C increments and first/second derivatives allows complete assignment of solid, liquid and transition state vibrational modes, including low intensity/frequency vibrations that cannot be readily analyzed with conventional Raman. DPA and DHA show significant spectral changes with premelting (-33 and -60°C, respectively) and melting (-27 and -44°C, respectively). The CH2-(HC=CH)-CH2 moieties are not identical in the second half of the DHA and DPA structures. The DHA molecule contains major CH2 twisting (1265 cm-1) with no noticeable CH2 bending, consistent with a flat helical structure with small pitch. Further modeling of neuronal membrane phospholipids must take into account this structure for DHA, which would be configured parallel to the hydrophilic head group line.
The symmetrical β−conformer of endosulfan has the identical chemical composition of the asymmetrical α−conformer, and both have very different melting/boiling points. The α− and β−isomer however have markedly different Raman spectra at each of 50°C, 75°C and 100°C. Moreover, the commercially available Raman spectra of the 60/40 (α−/β−) mixture at the same temperatures is discrete from either a- and b-isomer alone. Previous research demonstrated that at a- boiling point 110°C, β−conformer partially converts to α−. DSC curves of mixtures suggest thermal interactions and conformational changes occurs in BOTH α− and β−isomer at temperatures even 60°C lower than the liquid/gas phase transition.
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