Heinar Schmidt

Handheld Raman spectroscopy has potential for rapid, non-destructive characterization of meat, but the application of handheld Raman spectroscopy to the histological characterization of skeletal muscle has not yet been systematically investigated. This pilot study investigated porcine m. adductor (AD) and m. semimembranosus (SM), which differ markedly in muscle fiber composition. Meat samples from six commercial pigs of the German Landrace × Pietrain crossbred line, all female and with similar body weight were analysed by handheld Raman spectroscopy and histology. Histological analysis showed significantly different fiber-type composition between SM and AD: SM contained 9.56% slow-twitch oxidative, 14.44% fast-twitch oxidative, and 75.99% fast-twitch glycolytic fibers, compared with 24.94%, 24.91%, and 50.15%, respectively, in AD (all P ≤ 0.002). Principal components analysis (PCA) of Raman spectra showed clear separation of AD and SM, with the first two principal components explaining 82.29% of the total variance. The separation was associated with differences in protein-related spectral features, particularly amide I and amide III, and with haem- and phosphate-associated signals. Separate PCA analyses of AD and SM revealed within-muscle spectral variation. These preliminary findings indicate that handheld Raman spectroscopy can capture spectral differences between porcine muscles with contrasting fiber-type composition. The results provide an initial basis for further investigation of whether specific Raman spectral features can be associated with muscle fiber-type composition. Future studies should include larger numbers of animals, a wider range of muscles, and Raman measurements of individual muscle fiber types to assess the specificity and generalizability of these observations.

Interactions of microplastic particles with cells are key prerequisites for their cellular internalization, tissue translocation, and potential hazards. Numerous studies have investigated cellular interactions of microplastics, but most relied on model particles, typically pristine polystyrene microspheres, which do not reflect environmentally relevant microplastics. In natural environments, microplastic particles undergo weathering processes that alter their physicochemical properties. These include abiotic weathering, such as photooxidation, and biotic weathering, including the formation of an eco-corona. Both processes have been shown individually to influence particle–cell interactions, yet their combined effects remain poorly understood. In this study, we investigated the individual and combined effects of abiotic and biotic weathering on particle-cell interactions, including the internalization of microplastic particles. Pristine polystyrene microspheres were subjected to accelerated abiotic weathering using UV radiation and subsequently exposed to environmental media to simulate biotic weathering, leading to eco-corona formation. Weathering significantly altered particle size, shape, surface roughness, ζ-potential, and chemical surface composition. In general, particles increased in size, became less spherical, developed rougher surfaces, and showed modified surface chemistry after weathering. Abiotic weathering appeared to be the primary driver of altered binding affinity and adhesion strength to cells, mainly due to electrostatic interactions governed by the ζ-potential. In contrast, biotic weathering largely determined the probability of particle internalization, likely due to the acquisition of a biological identity through eco-corona formation. These findings provide mechanistic insight into the interactions between environmentally relevant microplastic particles and cells, contributing to improved assessment of their potential environmental and biological impacts.

To speed-up monitoring of the hygienic status of meat, fast and non-invasive measuring techniques are required. In this work, the feasibility was investigated to quantify the bioburden of minced meat with a hand-held fluorescence spectrometer. In two independent trials, 144 (165) minced pork samples from 18 (23) batches were stored at 2 ℃ for up to 8 (7) days. Fluorescence spectra, L*a*b* colour and total viable mesophilic plate counts (TVC) were measured in parallel. TVC varied from 2.7 to 10.4 log(TVC/g) in this period. Correlation of the fluorescence spectra with log(TVC/g) using partial least squares regression yielded cross-validated predictions with R2cv = 0.72 (0.83) and a prediction error of RMSECV = 0.97 (0.69) log(TVC/g). Cross-validated limits of detection and quantification were determined as 1.0 (0.9) and 3.4 (3.2) log(TVC/g), respectively. This would allow for a quantification well below the alarm threshold of 5.7–6.7 log(TVC/g). The spectra were strongly correlated with storage time with R2cv = 0.81 (0.67), but less strong with L*a*b* colour. Storage time was identified as interference which was reduced in the second trial by modifying the sampling.