Revealing covariance structures in fourier transform infrared and Raman microspectroscopy spectra: a study on pork muscle fiber tissue subjected to different processing parameters

Spectroscopic techniques combined with chemometrics for rapid detection of food adulteration: Applications, perspectives, and challenges

Food adulteration is an important threat to food safety and can be difficult to detect. Some analytical methods are complex and difficult to meet the needs of large numbers of samples. In this study, we introduced the application of six spectroscopic techniques (NIR, FTIR, HSI, Raman, UV-Vis, and FS) and chemometric methods in common food adulteration (powdered food, meat, honey, drink, edible oil, and dairy product) over the last three years. We introduced the consequences of food adulteration, the principles, advantages, and limitations of spectroscopic techniques, spectral data preprocessing and key wavelength selection methods, chemometrics methods, dataset division methods, and evaluation methods for models. Moreover, it provided a perspective for the future application of spectroscopic techniques in food adulteration. The results showed that linear chemometric methods were still the main method used by many researchers, which may limit the application potential of spectroscopic techniques. Therefore, deep learning-based chemometrics methods and their interpretability should be further explored in food adulteration. Secondly, data fusion and ensemble models based on multiple spectroscopic techniques and chemometrics can further improve the accuracy of the models. Future research should select appropriate spectroscopic techniques based on food type and spectroscopic principles, and consider portable technical solutions wherever possible to improve the application scenarios of spectroscopic techniques.

Fusion vs. Isolation: Evaluating the Performance of Multi-Sensor Integration for Meat Spoilage Prediction

High-throughput and portable sensor technologies are increasingly used in food production/distribution tasks as rapid and non-invasive platforms offering real-time or near real-time monitoring of quality and safety. These are often coupled with analytical techniques, including machine learning, for the estimation of sample quality and safety through monitoring of key physical attributes. However, the developed predictive models often show varying degrees of accuracy, depending on food type, storage conditions, sensor platform, and sample sizes. This work explores various fusion approaches for potential predictive enhancement, through the summation of information gathered from different observational spaces: infrared spectroscopy is supplemented with multispectral imaging for the prediction of chicken and beef spoilage through the estimation of bacterial counts in differing environmental conditions. For most circumstances, at least one of the fusion methodologies outperformed single-sensor models in prediction accuracy. Improvement in aerobic, vacuum, and mixed aerobic/vacuum chicken spoilage scenarios was observed, with performance enhanced by up to 15%. The improved cross-batch performance of these models proves an enhanced model robustness using the presented multi-sensor fusion approach. The batch-based results were corroborated with a repeated nested cross-validation approach, to give an out-of-sample generalised view of model performance across the whole dataset. Overall, this work suggests potential avenues for performance improvements in real-world, minimally invasive food monitoring scenarios.

Investigating the Impact of Long-Term Alcohol Consumption on Serum Chemical Changes: Fourier Transform Infrared Spectroscopy for Human Blood Serum

Chronic alcohol consumption significantly impacts physiological and neurological functions. This study aimed to investigate the biochemical alterations in serum associated with long-term alcohol use using Fourier Transform Infrared (FTIR) spectroscopy. Serum samples from control and alcohol use disorder (AUD) were analyzed, and their spectra were compared. Multivariate analysis techniques, including Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), were employed to differentiate the groups. A machine learning model, Grid Search-Support Vector Machine Discriminant Analysis (GS-SVMDA), was developed to classify samples with high accuracy. Significant differences in the absorbance values of specific functional groups, particularly those associated with phospholipids, amides, and fatty acids revealed. The AUD exhibited lower levels of these biomolecules. The models achieved perfect classification, demonstrating the potential ofFTIR spectroscopy as a non-invasive tool for diagnosing AUD. Findings contribute to a better understanding of the biochemical mechanisms underlying alcohol addiction and may aid in the development of novel diagnostic and therapeutic strategies.

Combined Effects of Compound Low-Sodium Alternative Salts and Vacuum Tumbling on the Quality, Water Distribution, and Microstructure of Marinated Beef

This study proposes a compound low-sodium alternative salt (CLSAS) formulation (2.4% sodium chloride, 0.8% K lactate, 0.4% magnesium chloride, 0.4% Ca ascorbate, 0.2% L lysine, and 4% sorbitol) combined with vacuum tumbling for beef marination. The effects of 4% NaCl static marination (F), CLSAS static marination (L), and CLSAS vacuum tumbling (VT-L) on the physicochemical properties, water distribution, and microstructure of marinated beef were evaluated. Compared with F, L maintained similar yield and color, reduced cooking loss, and improved texture while lowering sodium content. VT-L further enhanced product yield, water content, color, texture, and tenderness. Both CLSAS and vacuum tumbling reduced the relaxation time of immobilized water, promoted orderly formation of protein structure, and altered the microstructure of myogenic fibers. VT-L additionally improved the water-holding capacity of myofibrils and further reduced the relaxation times of immobilized and free water. Overall, VT-L could be an effective approach for enhancing the quality of low-sodium meat products, providing a feasible basis for the industrial application of CLSAS for low-sodium marinated meat products.

Shedding light on biochemical changes in single neuron-like pheochromocytoma cells following exposure to synchrotron sourced terahertz radiation using synchrotron source Fourier transform infrared microspectroscopy

Synchrotron sourced Fourier transform infrared (SS FTIR) microspectroscopy was employed to investigate the biological effects on the neuron-like pheochromocytoma (PC 12) cells after exposure to synchrotron sourced terahertz (SS THz) radiation. Over 10 min of exposure, the PC 12 cells received a total energy of 600 J m2, with a total incident power density of ∼1.0 W m-2 (0.10 mW cm-2) at the beam extraction port (BEP) of the THz beamline at the Australian Synchrotron. To investigate the metabolic response of PC 12 cells after synchrotron THz radiation exposure, we utilized the FTIR microscope at the Infrared Microspectroscopy IRM beamline, which offers high photon flux and diffraction-limited spatial resolution enabling the detection of functional group variations in biological molecules at a single-cell level. Principal component analysis (PCA) based on the SS FTIR spectral data revealed a distinct separation of SS THz-exposed and control (non-exposed) cells. According to the PCA loadings, the key changes in the exposed cells involved lipid and protein compositions as indicated by the stretching vibrations of CH2/CH3 groups and amide I/II bands, respectively. An increase in lipids, such as cholesterol, or notable changes in their compositions and in some protein secondary structures were observed in the SS THz-exposed cells. The PCA analysis further suggests that PC 12 cells might maintain cell membrane stability after SS THz irradiation through higher volumes of cholesterol and cell morphology via regulation of the synthesis of cytoskeleton proteins such as actin-related proteins. The outcome of this study re-emphasized the exceptional SS FTIR capability to perform single-cell analysis directly, providing (i) unique biological information on cell variability within the population as well as between different groups, and (ii) evidence of molecular changes in the exposed cells that could lead to a deeper understanding of the effect of THz exposure at a single-cell level.

Optimising Shifted Excitation Raman Difference Spectroscopy (SERDS) for application in highly fluorescent biological samples, using fibre optic probes

Fibre optic probe based Raman spectroscopy can deliver in vivo molecular compositional analysis of a range of diseases. However, some biological tissues exhibit high levels of fluorescence which limit the utility of the technique, particularly when the fluorescence induces CCD etaloning, which can be particulalry hard to remove in subsequent analysis. Furthermore, use of fibre probes can result in silica signals superimposed on the biological Raman signals. Shifted excitation Raman difference spectroscopy (SERDS) utilises a small seperation in excitation wavelengths to remove signals from fluorescence, room lights, optical components and etaloning contributions, while retaining chemical signals from the sample. In this study, we sought to measure the optimum SERDS spectra enabling reconstruction of a range a narrow and broad peaks found in biological samples.  A original wavelength of 830 nm was utilised with 7 different shifts between 0.4 and 3.9 nm to determine which gave the best performance. This range roughly corresponds to the typical range of peak widths within biological Raman spectra at 830 nm excitation; 0.41 - 3.25 nm or 6 - 47 cm-1. An wavelength shift of 2.4 nm was identified as optimal. Finally, a fibre optic Raman probe was used to measure 2 human lymph nodes ex vivo to demonstrate the feasibility of the approach with real-world examples.

Differentiation of protein types extracted from tilapia byproducts by FTIR spectroscopy combined with chemometric analysis and their antioxidant protein hydrolysates

This research aimed to characterize protein types including sarcoplasmic protein (SP), myofibrillar protein (MP), and alkali-aided protein extract (AP) prepared from tilapia byproducts using water, 0.6 M NaCl, and alkaline solution (pH 11), respectively compared to freeze-dried minced tilapia muscle (CONTROL). Principal component analysis was performed from second derivative FTIR spectra to differentiate protein type. The AP mostly contained β-sheet structure and had low total sulfhydryl content and surface hydrophobicity. SP can be distinguished from MP by the loading plots of the FTIR bands representing the α-helical structure. While the bands for lipids and β-sheet of protein were noted for differentiating AP from CONTROL. After being hydrolyzed by Protease G6, the AP hydrolysate disclosed the highest ABTS radical scavenging activity, while the SP hydrolysate revealed the strongest metal chelating ability. Thus, an understanding of how fish processing waste can be utilized in the production of antioxidant protein hydrolysates has been achieved.

Staphylococcus aureus surface attachment selectively influences tolerance against charged antibiotics

The threat of infection during implant placement surgery remains a considerable burden for millions of patients worldwide. To combat this threat, clinicians employ a range of anti-infective strategies and practices. One of the most common interventions is the use of prophylactic antibiotic treatment during implant placement surgery. However, these practices can be detrimental by promoting the resilience of biofilm-forming bacteria and enabling them to persist throughout treatment and re-emerge later, causing a life-threatening infection. Thus, it is of the utmost importance to elucidate the events occurring during the initial stages of bacterial surface attachment and determine whether any biological processes may be targeted to improve surgical outcomes. Using gene expression analysis, we identified a cellular mechanism of S. aureus which modifies its cell surface charge following attachment to a medical grade titanium surface. We determined the upregulation of two systems involved in the d-alanylation of teichoic acids and the lysylation of phosphatidylglycerol. We supported these molecular findings by utilizing synchrotron-sourced attenuated total reflection Fourier-transform infrared microspectroscopy to analyze the biomolecular properties of the S. aureus cell surface following attachment. As a direct consequence, S. aureus quickly becomes substantially more tolerant to the positively charged vancomycin, but not the negatively charged cefazolin. The present study can assist clinicians in rationally selecting the most potent antibiotic in prophylaxis treatments. Furthermore, it highlights a cellular process that could potentially be targeted by novel technologies and strategies to improve the outcome of antibiotic prophylaxis during implant placement surgery. STATEMENT OF SIGNIFICANCE: The antibiotic tolerance of bacteria in biofilm is a well-established phenomenon. However, the physiological adaptations employed by Staphylococcus aureus to increase its antibiotic tolerance during the early stages of surface attachment are poorly understood. Using multiple techniques, including gene expression analysis and synchrotron-sourced Fourier-transform infrared microspectroscopy, we generated insights into the physiological response of S. aureus following attachment to a medical grade titanium surface. We showed that this phenotypic transition enables S. aureus to better tolerate the positively charged vancomycin, but not the negatively charged cefazolin. These findings shed light on the antibiotic tolerance mechanisms employed by S. aureus to survive prophylactically administered antibiotics and can help clinicians to protect patients from infections.

Exploration of macromolecular phenotype of human skeletal muscle in diabetes using infrared spectroscopy

Introduction

The global burden of diabetes mellitus is escalating, and more efficient investigative strategies are needed for a deeper understanding of underlying pathophysiological mechanisms. The crucial role of skeletal muscle in carbohydrate and lipid metabolism makes it one of the most susceptible tissues to diabetes-related metabolic disorders. In tissue studies, conventional histochemical methods have several technical limitations and have been shown to inadequately characterise the biomolecular phenotype of skeletal muscle to provide a holistic view of the pathologically altered proportions of macromolecular constituents.

Materials and methods

In this pilot study, we examined the composition of five different human skeletal muscles from male donors diagnosed with type 2 diabetes and non-diabetic controls. We analysed the lipid, glycogen, and collagen content in the muscles in a traditional manner with histochemical assays using different staining techniques. This served as a reference for comparison with the unconventional analysis of tissue composition using Fourier-transform infrared spectroscopy as an alternative methodological approach.

Results

A thorough chemometric post-processing of the infrared spectra using a multi-stage spectral decomposition allowed the simultaneous identification of various compositional details from a vibrational spectrum measured in a single experiment. We obtained multifaceted information about the proportions of the different macromolecular constituents of skeletal muscle, which even allowed us to distinguish protein constituents with different structural properties. The most important methodological steps for a comprehensive insight into muscle composition have thus been set and parameters identified that can be used for the comparison between healthy and diabetic muscles.

Conclusion

We have established a methodological framework based on vibrational spectroscopy for the detailed macromolecular analysis of human skeletal muscle that can effectively complement or may even serve as an alternative to histochemical assays. As this is a pilot study with relatively small sample sets, we remain cautious at this stage in drawing definitive conclusions about diabetes-related changes in skeletal muscle composition. However, the main focus and contribution of our work has been to provide an alternative, simple and efficient approach for this purpose. We are confident that we have achieved this goal and have brought our methodology to a level from which it can be successfully transferred to a large-scale study that allows the effects of diabetes on skeletal muscle composition and the interrelationships between the macromolecular tissue alterations due to diabetes to be investigated.

Heating temperatures affect meat quality and vibrational spectroscopic properties of slow- and fast-growing chickens

This study determined the effect of water bath cooking (70°C and 90°C for 40 min) and the extreme heat treatment by an autoclave (121°C for 40 min) on the quality of breast meat of a fast-growing chicken, commercial broiler (CB), and slow-growing chickens, Korat chicken (KC), and Thai native chicken (NC) (Leung Hang Khao), by vibrational spectroscopic techniques, including synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy and Fourier transform Raman (FT-Raman) spectroscopy. Taste-enhancing compounds, including inosine-5'-monophosphate (IMP) and guanosine-5'-monophosphate (GMP), were better retained in cooked KC and NC meats than in cooked CB meat (P < 0.05). The high heat treatment at 121°C depleted the amount of insoluble collagen in all breeds (P < 0.05). Shear force values of slow-growing chicken meat were not affected by high heating temperatures (P > 0.05). In addition, the high heat treatment increased protein carbonyl (P < 0.05), while no effect on in vitro protein digestibility (P > 0.05). SR-FTIR microspectroscopy performed better in differentiating the meat quality of different chicken breeds, whereas FT-Raman spectroscopy clearly revealed differences in meat qualities induced by heating temperature. Based on principal component analysis (PCA), distinct characteristics of chicken meat cooked at 70°C were high water-holding capacity, lightness (L*), moisture content, and predominant α-helix structure, correlating with Raman spectra at 3,217 cm^-1 (O-H stretching of water) and 1,651 cm^-1 (amide I; α-helix). The high heating temperature at 90°C and 121°C exposed protein structure to a greater extent, as evidenced by an increase in β-sheets, which was well correlated with the Raman spectra at 2,968 and 2,893 cm^-1 (C-H stretching), tryptophan (880 cm^-1), tyrosine (858 cm^-1), and 1,042, 1,020, and 990 cm^-1 (C-C stretching; β-sheet). SR-FTIR and FT-Raman spectroscopy show potential for differentiation of chicken meat quality with respect to breeds and cooking temperatures. The marked differences in wavenumbers would be beneficial as markers for determining the quality of cooked meats from slow- and fast-growing chickens.

Preliminary investigation into the prediction of indicators of beef spoilage using Raman and Fourier transform infrared spectroscopy

The objective of this study was to assess the potential to predict the microbial beef spoilage indicators by Raman and Fourier transform infrared (FT-IR) spectroscopies. Vacuum skin packaged (VSP) beef steaks were stored at 0 °C, 4 °C, 8 °C and under a dynamic temperature condition (0 °C ∼ 4 °C ∼ 8 °C, for 36 d). Total viable count (TVC) and total volatile basic nitrogen (TVB-N) were obtained during the storage period along with spectroscopic data. The Raman and FTIR spectra were baseline corrected, pre-processed using Savitzky-Golay smoothing and normalized. Subsequently partial least squares regression (PLSR) models of TVC and TVB-N were developed and evaluated. The root mean squared error (RMSE) ranged from 0.81 to1.59 (log CFU/g or mg/100 g) and the determination coefficient (R²) from 0.54 to 0.75. The performance of PLSR model based on data fusion (combination of Raman and FT-IR data) is better than that based on Raman spectra and similar to that of FT-IR. Overall, Raman spectroscopy, FT-IR spectroscopy, and a combination of both exhibited a potential for the prediction of the beef spoilage.

Contribution of κ-/ι-carrageenan on the gelling properties of shrimp myofibrillar protein and their interaction mechanism exploration

BACKGROUND

The contribution and mechanism of κ-/ι-carrageenan (CG) with different hydration characteristics on the gelling properties of shrimp myofibrillar protein (MP) gelation was studied.

RESULTS

The gel strength, water-holding capacity and viscoelastic properties of MP gels were significantly enhanced by 1.0% κ-/ι-CG (P < 0.05), but the microstructure showed that excessive carrageenan caused fragmentation of the gel network and a corresponding decrease in gel properties. Compared to MP-ιCG, MP-κCG showed larger breaking force and shorter breaking distance, thus enhancing the hardness and brittleness of the gel, which might be ascribed to a reinforced network skeleton and a tighter binding of κCG-myosin. However, MP-ιCG stabilized more moisture in the gel network, thereby improving the tenderness of the gel, which might be related to the electrostatic repulsion observed between the sulfate groups of ιCG and the myosin observed by molecular docking. In addition, the β-sheet content and intermolecular interactions might be positively correlated with gel properties.

CONCLUSION

In this study, a composite gel system was constructed based on the interaction of MP and CG. The quality differences of two kinds of CG-MP gels were clarified, which will provide guidance for the application of different kinds of carrageenan and the development of recombinant meat products with specific quality. © 2022 Society of Chemical Industry.

Assessment of the Microbial Spoilage and Quality of Marinated Chicken Souvlaki through Spectroscopic and Biomimetic Sensors and Data Fusion

Fourier-transform infrared spectroscopy (FT-IR), multispectral imaging (MSI), and an electronic nose (E-nose) were implemented individually and in combination in an attempt to investigate and, hence, identify the complexity of the phenomenon of spoilage in poultry. For this purpose, marinated chicken souvlaki samples were subjected to storage experiments (isothermal conditions: 0, 5, and 10 °C; dynamic temperature conditions: 12 h at 0 °C, 8 h at 5 °C, and 4 h at 10 °C) under aerobic conditions. At pre-determined intervals, samples were microbiologically analyzed for the enumeration of total viable counts (TVCs) and Pseudomonas spp., while, in parallel, FT-IR, MSI, and E-nose measurements were acquired. Quantitative models of partial least squares–Regression (PLS-R) and support vector machine–regression (SVM-R) (separately for each sensor and in combination) were developed and validated for the estimation of TVCs in marinated chicken souvlaki. Furthermore, classification models of linear discriminant analysis (LDA), linear support vector machine (LSVM), and cubic support vector machines (CSVM) that classified samples into two quality classes (non-spoiled or spoiled) were optimized and evaluated. The model performance was assessed with data obtained by six different analysts and three different batches of marinated souvlaki. Concerning the estimation of the TVCs via the PLS-R model, the most efficient prediction was obtained with spectral data from MSI (root mean squared error—RMSE: 0.998 log CFU/g), as well as with combined data from FT-IR/MSI (RMSE: 0.983 log CFU/g). From the developed SVM-R models, the predictions derived from MSI and FT-IR/MSI data accurately estimated the TVCs with RMSE values of 0.973 and 0.999 log CFU/g, respectively. For the two-class models, the combined data from the FT-IR/MSI instruments analyzed with the CSVM algorithm provided an overall accuracy of 87.5%, followed by the MSI spectral data analyzed with LSVM, with an overall accuracy of 80%. The abovementioned findings highlighted the efficacy of these non-invasive rapid methods when used individually and in combination for the assessment of spoilage in marinated chicken products regardless of the impact of the analyst, season, or batch.

Application of FTIR Spectroscopy to Detect Changes in Skeletal Muscle Composition Due to Obesity with Insulin Resistance and STZ-Induced Diabetes

Age, obesity, and diabetes mellitus are pathophysiologically interconnected factors that significantly contribute to the global burden of non-communicable diseases. These metabolic conditions are associated with impaired insulin function, which disrupts the metabolism of carbohydrates, lipids, and proteins and can lead to structural and functional changes in skeletal muscle. Therefore, the alterations in the macromolecular composition of skeletal muscle may provide an indication of the underlying mechanisms of insulin-related disorders. The aim of this study was to investigate the potential of Fourier transform infrared (FTIR) spectroscopy to reveal the changes in macromolecular composition in weight-bearing and non-weight-bearing muscles of old, obese, insulin-resistant, and young streptozotocin (STZ)-induced diabetic mice. The efficiency of FTIR spectroscopy was evaluated by comparison with the results of gold-standard histochemical techniques. The differences in biomolecular phenotypes and the alterations in muscle composition in relation to their functional properties observed from FTIR spectra suggest that FTIR spectroscopy can detect most of the changes observed in muscle tissue by histochemical analyses and more. Therefore, it could be used as an effective alternative because it allows for the complete characterization of macromolecular composition in a single, relatively simple experiment, avoiding some obvious drawbacks of histochemical methods.

A comparative study of meat quality and vibrational spectroscopic properties of different chicken breeds

Chicken breed is one of the key factors that influence meat quality. The quality attributes of breast meat from commercial broiler (CB), Thai native chicken (NC, Leung Hang Khao), and the crossbred Korat chicken (KC) were investigated via synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, and physicochemical analysis. The protein and carbonyl contents of KC and NC meats were higher than that of CB meat, but the lipid content was lower (P < 0.05). CB meat was characterized by high moisture, lightness (L*), and presence of taste-active nucleotides, namely, inosine 5′-monophosphate (IMP) and guanosine 5′-monophosphate (GMP). Moreover, NC meat had the highest insoluble collagen and inosine contents (P < 0.05). The predominant protein secondary structures of KC and NC meats were β-turns and random coils, whereas α-helices were mainly found in CB meat. Based on principal component analysis, the meat quality and spectra were clearly separated by breeds. The high moisture and lipid content of meat corresponded to O–H stretching (3,203 cm⁻¹) and C–H stretching (2,854 cm⁻¹) in the FT-Raman spectra, whereas PO₂⁻ stretching (1,240 cm⁻¹), measured via SR-FTIR, was well correlated with the IMP content. In addition, the FT-Raman wavenumber of 934 cm⁻¹, indicating C–C stretching, was correlated with high water-holding capacity (WHC) in KC meat. The quality of meat from slow- and fast-growing chickens significantly varies. Vibrational spectroscopy is a powerful technique that provides insightful molecular information correlated with various meat attributes.

Effects of β-alanine and L-histidine supplementation on carnosine contents in and quality and secondary structure of proteins in slow-growing Korat chicken meat

Carnosine enrichment of slow-growing Korat chicken (KRC) meat helps differentiate KRC from mainstream chicken. We aimed to investigate the effects of β-alanine and L-histidine supplementation on the carnosine synthesis in and quality and secondary structure of proteins in slow-growing KRC meat. Four hundred 21-day-old female KRC were used, and a completely randomized design was applied. The chickens were divided into 4 experimental groups: basal diet (A), basal diet supplemented with 1.0% β-alanine (B), 0.5% L-histidine (C), and 1.0% β-alanine combined with 0.5% L-histidine (D). Each group consisted of 5 replicates (20 chickens per replicate). On d 70, 2 chickens per replicate were slaughtered, and the levels of carnosine, anserine, and thiobarbituric acid reactive substances were analyzed. Biochemical changes were monitored using synchrotron radiation-based Fourier transform infrared microspectroscopy; 5 chickens per replicate were slaughtered, and the meat quality was analyzed. Statistical analysis was performed using ANOVA and principal component analysis (PCA). Group D chickens exhibited the highest carnosine meat content, followed by those in groups B and C. However, amino acid supplementation did not affect anserine content and growth performance. Higher carnosine levels correlated with increasing pH_{45 min} and decreasing drip loss, cooking loss, shear force, and lipid oxidation. PCA revealed that supplementation with only β-alanine or L-histidine was related to increased content of β-sheets, β-turns, and aliphatic bending groups and decreased content of α-helix groups. This study is the first to report such findings in slow-growing chicken. Our findings suggest that KRC can synthesize the highest carnosine levels after both β-alanine and L-histidine supplementation. Higher carnosine contents do not adversely affect meat quality, improve meat texture, and alter the secondary structures of proteins. The molecular mechanism underlying carnosine synthesis in chickens needs further study to better understand and reveal markers that facilitate the development of nutrient selection programs.

Illuminating the biochemical interaction of antimicrobial few-layer black phosphorus with microbial cells using synchrotron macro-ATR-FTIR

In the fight against drug-resistant pathogenic bacterial and fungal cells, low-dimensional materials are emerging as a promising alternative treatment method. Specifically, few-layer black phosphorus (BP) has demonstrated its effectiveness against a wide range of pathogenic bacterial and fungal cells with studies suggesting low cytotoxicity towards healthy mammalian cells. However, the antimicrobial mechanism of action of BP is not well understood. Before new applications for this material can be realised, further in-depth investigations are required. In this work, the biochemical interaction between BP and a series of microbial cells is investigated using a variety of microscopy and spectroscopy techniques to provide a greater understanding of the antimicrobial mechanism. Synchrotron macro-attenuated total reflection-Fourier transform infrared (ATR-FTIR) micro-spectroscopy is used to elucidate the chemical changes occurring outside and within the cell of interest after exposure to BP nanoflakes. The ATR-FTIR data, coupled with high-resolution microscopy, reveals major physical and bio-chemical changes to the phospholipids and amide I and II proteins, as well as minor chemical changes to the structural polysaccharides and nucleic acids when compared to untreated cells. These changes can be attributed to the physical interaction of the BP nanoflakes with the cell membranes, combined with the oxidative stress induced by the degradation of the BP nanoflakes. This study provides insight into the biochemical interaction of BP nanoflakes with microbial cells, allowing for a better understanding of the antimicrobial mechanism of action that will be important for the next generation of applications such as implant coatings, wound dressings, or medical surfaces.

Sous Vide Cook Temperature Alters the Physical Structure and Lipid Bioaccessibility of Beef Longissimus Muscle in TIM-1

Changes in the physical states, induced with different sous vide cooking temperatures, significantly (P < 0.05) altered lipid bioaccessibility measured in the TNO-simulated gastrointestinal tract model-1 of AAA boneless beef striploin, containing the longissimus lumborum muscle. The denaturation of actin significantly correlates with the total cumulative free fatty acid (FFA) bioaccessibility, whereby the striploin cooked to 60 °C presents the maximum lipid bioaccessibility (15.8 ± 1.0%), rate constant (k_a) for FFA hydrolysis (0.087 ± 0.003 min^-1), and greatest actin denaturation enthalpy (-0.57 ± 0.06 ΔH). Thus, thermal treatments above 60 °C significantly decrease the kinetics of lipolysis (70 °C = 0.042 ± 0.002 min^-1 and 80 °C = 0.047 ± 0.002 min^-1) and the resultant total lipid bioaccessibility (70 °C = 8.6 ± 0.7 and 80 °C = 8.3 ± 0.5%). This research highlights the potential to manipulate the physical food structure to alter digestion kinetics, supporting the need to understand supramolecular structures in food and their nutritional outcomes.

Use of Fourier Transform Infrared Spectroscopy for Monitoring the Shelf Life and Safety of Yogurts Supplemented With a Lactobacillus plantarum Strain With Probiotic Potential

The current study aimed to explore the performance of a probiotic Lactobacillus strain as an adjunct culture in yogurt production and to assess Fourier transform infrared spectroscopy as a rapid, noninvasive analytical technique to evaluate the quality and the shelf life of yogurt during storage. In this respect, bovine milk (full-fat) was inoculated with the typical yogurt starter culture without (control case) or with the further addition of Lactobacillus plantarum T571 as an adjunct (probiotic case). The milk was also inoculated with a cocktail mixture of three strains of Listeria monocytogenes in two different initial levels of inoculum, and the fermentation process was followed. Accordingly, yogurt samples were stored at 4 and 12°C, and microbiological, physicochemical, molecular, and sensory analyses were performed during storage. Results showed that the lactic acid bacteria exceeded 7 log CFU/g during storage in all samples, where the probiotic samples displayed higher acidity, lower pH, and reduced counts of Lb. monocytogenes in a shorter period than the control ones at both temperatures. Pulsed-field gel electrophoresis verified the presence of the probiotic strain until the end of storage at both temperatures and in adequate amounts, whereas the survival and the distribution of Listeria strains depended on the case. The sensory evaluation showed that the probiotic samples had desirable organoleptic characteristics, similar to the control. Finally, the spectral data collected from the yogurt samples during storage were correlated with microbiological counts and sensory data. Partial least squares and support vector machine regression and classification models were developed to provide quantitative estimations of yogurt microbiological counts and qualitative estimations of their sensory status, respectively, based on Fourier transform infrared fingerprints. The developed models exhibited satisfactory performance, and the acquired results were promising for the rapid estimation of the microbiological counts and sensory status of yogurt.

Analysis of Pathogenic Bacterial and Yeast Biofilms Using the Combination of Synchrotron ATR-FTIR Microspectroscopy and Chemometric Approaches

Biofilms are assemblages of microbial cells, extracellular polymeric substances (EPS), and other components extracted from the environment in which they develop. Within biofilms, the spatial distribution of these components can vary. Here we present a fundamental characterization study to show differences between biofilms formed by Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Pseudomonas aeruginosa, and the yeast-type Candida albicans using synchrotron macro attenuated total reflectance-Fourier transform infrared (ATR-FTIR) microspectroscopy. We were able to characterise the pathogenic biofilms' heterogeneous distribution, which is challenging to do using traditional techniques. Multivariate analyses revealed that the polysaccharides area (1200-950 cm^-1) accounted for the most significant variance between biofilm samples, and other spectral regions corresponding to amides, lipids, and polysaccharides all contributed to sample variation. In general, this study will advance our understanding of microbial biofilms and serve as a model for future research on how to use synchrotron source ATR-FTIR microspectroscopy to analyse their variations and spatial arrangements.

Rapid Microbial Quality Assessment of Chicken Liver Inoculated or Not With Salmonella Using FTIR Spectroscopy and Machine Learning

Chicken liver is a highly perishable meat product with a relatively short shelf-life and that can get easily contaminated with pathogenic microorganisms. This study was conducted to evaluate the behavior of spoilage microbiota and of inoculated Salmonella enterica on chicken liver. The feasibility of Fourier-transform infrared spectroscopy (FTIR) to assess chicken liver microbiological quality through the development of a machine learning workflow was also explored. Chicken liver samples [non-inoculated and inoculated with a four-strain cocktail of ca. 10³ colony-forming units (CFU)/g Salmonella] were stored aerobically under isothermal (0, 4, and 8°C) and dynamic temperature conditions. The samples were subjected to microbiological analysis with concomitant FTIR measurements. The developed FTIR spectral analysis workflow for the quantitative estimation of the different spoilage microbial groups consisted of robust data normalization, feature selection based on extra-trees algorithm and support vector machine (SVM) regression analysis. The performance of the developed models was evaluated in terms of the root mean square error (RMSE), the square of the correlation coefficient (R²), and the bias (B_f) and accuracy (A_f) factors. Spoilage was mainly driven by Pseudomonas spp., followed closely by Brochothrix thermosphacta, while lactic acid bacteria (LAB), Enterobacteriaceae, and yeast/molds remained at lower levels. Salmonella managed to survive at 0°C and dynamic conditions and increased by ca. 1.4 and 1.9 log CFU/g at 4 and 8°C, respectively, at the end of storage. The proposed models exhibited A_f and B_f between observed and predicted counts within the range of 1.071 to 1.145 and 0.995 to 1.029, respectively, while the R² and RMSE values ranged from 0.708 to 0.828 and 0.664 to 0.949 log CFU/g, respectively, depending on the microorganism and chicken liver samples. Overall, the results highlighted the ability of Salmonella not only to survive but also to grow at refrigeration temperatures and demonstrated the significant potential of FTIR technology in tandem with the proposed spectral analysis workflow for the estimation of total viable count, Pseudomonas spp., B. thermosphacta, LAB, Enterobacteriaceae, and Salmonella on chicken liver.

Spoilage assessment of chicken breast fillets by means of fourier transform infrared spectroscopy and multispectral image analysis

The objective of this research was the evaluation of Fourier transforms infrared spectroscopy (FT-IR) and multispectral image analysis (MSI) as efficient spectroscopic methods in tandem with multivariate data analysis and machine learning for the assessment of spoilage on the surface of chicken breast fillets. For this purpose, two independent storage experiments of chicken breast fillets (n ​= ​215) were conducted at 0, 5, 10, and 15 ​°C for up to 480 ​h. During storage, samples were analyzed microbiologically for the enumeration of Total Viable Counts (TVC) and Pseudomonas spp. In addition, FT-IR and MSI spectral data were collected at the same time intervals as for microbiological analyses. Multivariate data analysis was performed using two software platforms (a commercial and a publicly available developed platform) comprising several machine learning algorithms for the estimation of the TVC and Pseudomonas spp. population of the surface of the samples. The performance of the developed models was evaluated by intra batch and independent batch testing. Partial Least Squares- Regression (PLS-R) models from the commercial software predicted TVC with root mean square error (RMSE) values of 1.359 and 1.029 log CFU/cm² for MSI and FT-IR analysis, respectively. Moreover, RMSE values for Pseudomonas spp. model were 1.574 log CFU/cm² for MSI data and 1.078 log CFU/cm² for FT-IR data. From the implementation of the in-house sorfML platform, artificial neural networks (nnet) and least-angle regression (lars) were the most accurate models with the best performance in terms of RMSE values. Nnet models developed on MSI data demonstrated the lowest RMSE values (0.717 log CFU/cm²) for intra-batch testing, while lars outperformed nnet on independent batch testing with RMSE of 1.252 log CFU/cm². Furthermore, lars models excelled with the FT-IR data with RMSE of 0.904 and 0.851 log CFU/cm² in intra-batch and independent batch testing, respectively. These findings suggested that FT-IR analysis is more efficient than MSI to predict the microbiological quality on the surface of chicken breast fillets.

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Poultry meat’s vulnerability to spoilage demands rapid quality assessment LWT-Food Sci. Technol.methods.

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FT-IR and MSI are non-invasive methods applied in a variety of meat products.

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SorfML is a web platform providing diverse machine learning algorithms.

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FT-IR analysis via lars predicted efficiently microbial loads of TVC.

Meat analogs: Protein restructuring during thermomechanical processing

Increasing awareness of inefficient meat production and its future impact on global food security has led the food industry to look for a sustainable approach. Meat products have superior sensorial perception, because of their molecular composition and fibrous structure. Current understanding in the science of food structuring has enabled the utilization of alternative or nonmeat protein ingredients to create novel structured matrices that could resemble the textural functionality of real meat. The physicochemical and structural changes that occur in concentrated protein systems during thermomechanical processing lead to the creation of a fibrous or layered meat-like texture. Phase transitions in concentrated protein systems during protein-protein, protein-polysaccharide, protein-lipid, and protein-water interactions significantly influence the texture and the overall sensory quality of meat analogs. This review summarizes the roles of raw materials (moisture, protein type and concentration, lipids, polysaccharides, and air) and processing parameters (temperature, pH, and shear) in modulating the behavior of the protein phase during the restructuring process (structure-function-process relationship). The big challenge for the food industry is to manufacture concept-based (such as beef-like, chicken-like, etc.) meat analogs with controlled structural attributes. This information will be useful in developing superior meat analogs that fulfill consumer expectations when replacing meat in their diet.

Thermal denaturation of proteins in the muscle fibre and connective tissue from bovine muscles composed of type I (masseter) or type II (cutaneous trunci) fibres: DSC and FTIR microspectroscopy study

The changes in secondary structure of proteins with heating were characterised and compared for bovine masseter (fibre type I) and cutaneous trunci (fibre type II) muscles by Differential Scanning Calorimetry (DSC) and Fourier Transform InfraRed (FTIR) microspectroscopy. Heating led to a decrease in α- helices, and an increase in aggregated strands, random coils and aromatic side chains in the muscle fibres of both muscles. In the intramuscular connective tissue (IMCT) of both muscles, a decrease in α- helix, turn and unordered structures was complemented with an increase in aggregated strands. At temperatures < 60 °C, the greater thermal denaturation of proteins in cutaneous trunci than in masseter (FTIR), supported by a myosin associated peak at 55.8 °C for cutaneous trunci and no peak for masseter (DSC), indicates that myosin in type II fibres is more sensitive to thermal denaturation than myosin in type I fibres and this should be considered in thermal meat processing.

Modulating the aggregation of myofibrillar protein to alleviate the textural deterioration of protein gels at high temperature: The effect of hydrophobic interactions

In this study, the strategy of utilizing a model hydrophobic molecule, octenyl succinic anhydride (OSA), to inhibit over-aggregation of MP during heating, aiming to alleviate high temperature-induced textural deterioration of MP gels, was proposed, and a series of experiments were conducted to verify the effectiveness. The results showed that the effect was positively dependent on the concentrations of OSA. The addition of OSA at a concentration of 4 g/kg to 24 g/kg delayed the gelation temperature of MP, as confirmed by the DSC results, and inhibited the aggregation of MP through hydrophobic interactions between OSA and MP, as revealed by fluorescence and FTIR spectroscopy. Furthermore, when the concentration of OSA increased from 4 g/kg to 12 g/kg, the controlled aggregation of MP improved the gel properties of MP formed at high temperature, but when the concentration reached 24 g/kg, the protein aggregation was too inhibited to form developed gel networks.

Antimicrobial Activity of Oregano Essential Oil Incorporated in Sodium Alginate Edible Films: Control of Listeria monocytogenes and Spoilage in Ham Slices Treated with High Pressure Processing

The aim of the study was to evaluate the efficacy of oregano essential oil (OEO) incorporated in Na-alginate edible films when applied to sliced ham inoculated with a cocktail of Listeria monocytogenes strains, with or without pretreatment by high pressure processing (HPP). Microbiological, physicochemical and sensory analyses (in Listeria-free slices) were performed, while, the presence/absence and the relative abundance of each Listeria strain, was monitored by pulsed field gel electrophoresis (PFGE). The OEO incorporation in the films, caused approximately 1.5 log reduction in Listeria population at 8 and 12 °C at the end of the storage period, and almost 2.5 log reduction at 4 °C. The HPP treatment caused 1 log reduction to the initial Listeria population, while levels kept on decreasing throughout the storage for all the tested temperatures. The pH of the samples was higher in the cases where HPP was involved, and the samples were evaluated as less spoiled. Furthermore, the presence of OEO in the films resulted in color differences compared to the control samples, whilst the aroma of these samples was improved. In conclusion, the combined application of HPP and OEO edible films on the slices, led to a significant reduction or absence of the pathogen.

Estimation of Minced Pork Microbiological Spoilage through Fourier Transform Infrared and Visible Spectroscopy and Multispectral Vision Technology

Spectroscopic and imaging methods coupled with multivariate data analysis have been increasingly studied for the assessment of food quality. The objective of this work was the estimation of microbiological quality of minced pork using non-invasive spectroscopy-based sensors. For this purpose, minced pork patties were stored aerobically at different isothermal (4, 8, and 12 °C) and dynamic temperature conditions, and at regular time intervals duplicate samples were subjected to (i) microbiological analyses, (ii) Fourier transform infrared (FTIR) and visible (VIS) spectroscopy measurements, and (iii) multispectral image (MSI) acquisition. Partial-least squares regression models were trained and externally validated using the microbiological/spectral data collected at the isothermal and dynamic temperature storage conditions, respectively. The root mean squared error (RMSE, log CFU/g) for the prediction of the test (external validation) dataset for the FTIR, MSI, and VIS models was 0.915, 1.173, and 1.034, respectively, while the corresponding values of the coefficient of determination (R²) were 0.834, 0.727, and 0.788. Overall, all three tested sensors exhibited a considerable potential for the prediction of the microbiological quality of minced pork.

The Iceman's Last Meal Consisted of Fat, Wild Meat, and Cereals

The history of humankind is marked by the constant adoption of new dietary habits affecting human physiology, metabolism, and even the development of nutrition-related disorders. Despite clear archaeological evidence for the shift from hunter-gatherer lifestyle to agriculture in Neolithic Europe [1], very little information exists on the daily dietary habits of our ancestors. By undertaking a complementary -omics approach combined with microscopy, we analyzed the stomach content of the Iceman, a 5,300-year-old European glacier mummy [2, 3]. He seems to have had a remarkably high proportion of fat in his diet, supplemented with fresh or dried wild meat, cereals, and traces of toxic bracken. Our multipronged approach provides unprecedented analytical depth, deciphering the nutritional habit, meal composition, and food-processing methods of this Copper Age individual.

Analyzing μ-Calpain induced proteolysis in a myofibril model system with vibrational and fluorescence spectroscopy

Degree of post-mortem proteolysis influences overall meat quality (e.g. tenderness and water holding capacity). Degradation of isolated pork myofibril proteins by μ-Calpain for 0, 15 or 45 min was analyzed using four spectroscopic techniques; Raman, Fourier transform infrared (FT-IR), near infrared (NIR) and fluorescence spectroscopy. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to determine degree of proteolysis. The main changes detected by FT-IR and Raman spectroscopy were degradation of protein backbones manifested in the spectra as an increase in terminal carboxylic acid vibrations, a decrease in CN vibration, as well as an increase in skeletal vibrations. A reduction in β-sheet secondary structures was also detected, while α-helix secondary structure seemed to stay relatively unchanged. NIR and fluorescence were not suited to analyze degree of proteolysis in this model system.

Use of Fourier transform infrared spectroscopy for monitoring the shelf life of ham slices packed with probiotic supplemented edible films after treatment with high pressure processing

The aim of the present study was to investigate the potential use of Fourier transform infrared (FTIR) spectroscopy to quantify biochemical changes occurring in ham slices packed with probiotic supplemented edible films and treated with High Pressure Processing (HPP), in monitoring spoilage. Details regarding the data collection and experimental procedure were presented by Pavli et al. (2017). A series of Partial Least Squares (PLS) models were developed to correlate spectral data from FTIR analysis with ham spoilage during storage under vacuum at different temperatures (4, 8 and 12°C). FTIR spectra were collected from the surface of the ham samples in parallel with microbiological analysis of total viable counts (TVC) and lactic acid bacteria (LAB). Qualitative interpretation of spectral data was based on a sensory evaluation, using a hedonic scale, classifying the samples in three quality classes, fresh, semi-fresh and spoiled. The scope of the modeling approach was to discriminate the ham slices in their respective quality class and additionally to predict the microbial population directly from spectral data. The results obtained demonstrated that the processing of the samples affected the performance of classification in the sensory classes, with better results observed in the case of for ham slices packed with probiotic supplemented (PS) edible films and of control samples without HPP. The performance of PLS regression models on providing quantitative estimations of microbial counts were based on specific figures of merit (bias factor, accuracy factor, root mean square error, percentage of prediction error). Bias and accuracy factors were close to unity for both microbial groups tested for samples without HPP, whereas for HPP treated samples the values of these indices ranged from 0.963 to 1.332, depending on the case and indice. The results of this study demonstrated for the first time that although FTIR can be used reliably for the rapid assessment of sliced ham, additional processes such as HPP can affect its performance.

Structural changes evaluation with Raman spectroscopy in meat batters prepared by different processes

A comprehensive study was conducted to evaluate the structural changes of meat and protein of pork batters produced by chopping or beating process through the phase-contrast micrograph, laser light scattering analyzer, scanning electronic microscopy and Raman spectrometer. The results showed that the shattered myofibrilla fragments were shorter and particle-sizes were smaller in the raw batter produced by beating process than those in the chopping process. Compared with the raw and cooked batters produced by chopping process, modifications in amide I and amide III bands revealed a significant decrease of α-helix content and an increase of β-sheet, β-turn and random coils content in the beating process. The changes in secondary structure of protein in the batter produced by beating process was thermally stable. Moreover, more tyrosine residues were buried, and more gauche-gauche-trans disulfide bonds conformations and hydrophobic interactions were formed in the batter produced by beating process.

Gelation properties of myofibrillar protein under malondialdehyde-induced oxidative stress

BACKGROUND

The structure of myofibrillar protein (MP) can be readily altered by oxidation, leading to the unfolding of MP structure, which further promotes protein-protein interactions, and thus influences the MP gelling properties. The objective of the study was to investigate the effect of malondialdehyde-induced oxidative stress on the gelation properties of myofibrillar protein (MP). Structural changes of the oxidised MPs were evaluated by the contents of carbonyl and total sulfhydryls, surface hydrophobicity, SDS-PAGE and Fourier transform infrared spectroscopy. The oxidative stability of the MP gels as indicated by lipid hydroperoxide was also determined.

RESULTS

With the addition of an MDA concentration less than 10 mmol L^-1 , the MP gels showed an improved elasticity, gel strength, water holding capacity, and oxidative stability. Nevertheless, higher MDA concentration (25-50 mmol L^-1 ) significantly reduced the gel quality, probably due to the formation of excessive covalent bonds in the system.

CONCLUSION

Results suggested that protein aggregation occurred in the oxidised system. Myosin was involved in gel formation through non-disulfide covalent bond. © 2016 Society of Chemical Industry.

A Multiscale Vibrational Spectroscopic Approach for Identification and Biochemical Characterization of Pollen

BACKGROUND

Analysis of pollen grains reveals valuable information on biology, ecology, forensics, climate change, insect migration, food sources and aeroallergens. Vibrational (infrared and Raman) spectroscopies offer chemical characterization of pollen via identifiable spectral features without any sample pretreatment. We have compared the level of chemical information that can be obtained by different multiscale vibrational spectroscopic techniques.

METHODOLOGY

Pollen from 15 different species of Pinales (conifers) were measured by seven infrared and Raman methodologies. In order to obtain infrared spectra, both reflectance and transmission measurements were performed on ground and intact pollen grains (bulk measurements), in addition, infrared spectra were obtained by microspectroscopy of multigrain and single pollen grain measurements. For Raman microspectroscopy measurements, spectra were obtained from the same pollen grains by focusing two different substructures of pollen grain. The spectral data from the seven methodologies were integrated into one data model by the Consensus Principal Component Analysis, in order to obtain the relations between the molecular signatures traced by different techniques.

RESULTS

The vibrational spectroscopy enabled biochemical characterization of pollen and detection of phylogenetic variation. The spectral differences were clearly connected to specific chemical constituents, such as lipids, carbohydrates, carotenoids and sporopollenins. The extensive differences between pollen of Cedrus and the rest of Pinaceae family were unambiguously connected with molecular composition of sporopollenins in pollen grain wall, while pollen of Picea has apparently higher concentration of carotenoids than the rest of the family. It is shown that vibrational methodologies have great potential for systematic collection of data on ecosystems and that the obtained phylogenetic variation can be well explained by the biochemical composition of pollen. Out of the seven tested methodologies, the best taxonomical differentiation of pollen was obtained by infrared measurements on bulk samples, as well as by Raman microspectroscopy measurements of the corpus region of the pollen grain. Raman microspectroscopy measurements indicate that measurement area, as well as the depth of focus, can have crucial influence on the obtained data.

Raman spectroscopic study of structural changes upon chilling storage of frankfurters containing olive oil bulking agents as fat replacers

Technological properties and structural characteristics of proteins and lipids, using Raman spectroscopy, of frankfurters formulated with olive oil bulking agents as animal fat replacers were examined during chilling storage. Frankfurters reformulated with oil bulking agents showed lower (P<0.05) processing loss and higher (P<0.05) hardness and chewiness. Purge loss during chilling storage was relatively low, demonstrating a good water retention in the products. β-Sheet structures were enhanced by the use of olive oil bulking agents, and this effect was more pronounced in samples containing inulin. Reformulated frankfurters contained the least turns (P<0.05). A significant decrease of β-sheets and an increase of turns were observed after 85 days of chilled storage. The lowest (P<0.05) values of IνsCH2/IνasCH2 were recorded in frankfurters reformulated with oil bulking agents, which suggests more lipid acyl chain disorder. Structural characteristics were correlated to processing losses, hardness, and chewiness.