Assessment of water relaxometry of meat under different ageing processes using time domain nuclear magnetic resonance relaxometry.

This study assessed water relaxometry of beef exposed to different ageing techniques by examining the inner and surface regions using time-domain nuclear magnetic resonance (TD-NMR) relaxometry. Beef strip loins were aged under vacuum (Wet), under vacuum using moisture absorbers (Abs), under vacuum using moisture absorbers and with mechanical tenderisation (AbsTend), or without any packaging (Dry). The ageing technique significantly influenced various meat parameters, including dehydration, total loss, and the moisture content of the meat surface. The transverse (T2) relaxation times provided a more sensitive indicator of the changes in meat water relaxometry than the longitudinal (T1) relaxation times. The Dry samples exhibited distinct differences in the T2 signals between the surface and inner regions of the meat. In particular, for the inner region, there were significant differences in signal areas between the Wet and Dry samples, and the Abs and AbsTend samples were positioned closely together between the Dry and Wet samples. The principal component analysis supported these findings: it indicated some differentiation among the ageing techniques in the score plot, but the differentiation was more pronounced when analysing the surface region. Additionally, there was a strong correlation between dehydration and the T2 values, leading to a clustering of the samples based on the ageing technique. The overlap between the Abs and AbsTend samples, situated between the Dry and Wet samples, suggests the potential of these treatments to produce meat with properties that are intermediate to Wet and Dry meat. Furthermore, tenderisation did not lead to greater dehydration.

Non-Invasive Method to Predict the Composition of Requeijão Cremoso Directly in Commercial Packages Using Time Domain NMR Relaxometry and Chemometrics.

Low Field Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry was used to determine moisture, fat, and defatted dry matter contents in "requeijão cremoso" (RC) processed cheese directly in commercial packaged (plastic cups or tubes with approximately 200 g). Forty-five samples of commercial RC types (traditional, light, lactose-free, vegan, and fiber) were analyzed using longitudinal (T1) and transverse (T2) relaxation measurements in a wide bore Halbach magnet (0.23 T) with a 100 mm probe. The T1 and T2 analyses were performed using CWFP-T1 (Continuous Wave Free Precession) and CPMG (Carr-Purcell-Meiboom-Gill) single shot pulses. The scores of the principal component analysis (PCA) of CWFP-T1 and CPMG signals did not show clustering related to the RC types. Optimization by variable selection was carried out with ordered predictors selection (OPS), providing simpler and predictive partial least squares (PLS) calibration models. The best results were obtained with CWFP-T1 data, with root-mean-square errors of prediction (RMSEP) of 1.38, 4.71, 3.28, and 3.00% for defatted dry mass, fat in the dry and wet matter, and moisture, respectively. Therefore, CWFP-T1 data modeled with chemometrics can be a fast method to monitor the quality of RC directly in commercial packages.

Recent advances on determination of milk adulterants.

Milk adulteration is a current fraudulent practice to mask the quality parameters (e.g. protein and fat content) and increase the product shelf life. Milk adulteration includes addition of toxic substances, such as formaldehyde, hydrogen peroxide, hypochlorite, dichromate, salicylic acid, melamine, and urea. In order to assure the food safety and avoid health risks to consumers, novel analytical procedures have been proposed for detection of these adulterants. The innovations encompass sample pretreatment and improved detection and data processing, including chemometric tools. This review focuses on critical evaluation of analytical approaches for assay of milk adulteration, with emphasis on applications published after 2010. Alternatives for fast, environmentally friendly and in-situ detection of milk adulterants are highlighted.

Interaction of para-tert-butylcalix[6]arene molecules in Langmuir films with cadmium ions and their effects on molecular conformation and surface potential.

In this paper, we employ the surface-specific polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation (SFG) methods with surface pressure and surface potential isotherms to determine the organization of p-tert-butylcalix[6]arene molecules and their interaction with Cd(2+) ions in Langmuir monolayers. The area per molecule was estimated to be 135 Å(2), which corresponds to the Calix6 axis perpendicular to the air-water interface with most OH groups parallel to the interface. This area is larger than predicted by molecular modeling with quantum chemical calculations with a PM3 Hamiltonian (109 Å(2)), which is ascribed to the repulsion between Calix6 molecules. The incorporation of Cd(2+) ions in the subphase leads to drastic changes in the dipole moment contribution of the monolayer surface potential. Rather than increasing with incorporation of Cd(2+) ions owing to a decrease in the negative double-layer potential, the measured surface potential decreased monotonically with increasing ion concentration. This unexpected result was ascribed to a strong interaction with Cd(2+) ions that induced the calyx of the molecule to adopt a more open conformation at the air/water interface and affected the orientation of hydration water molecules, according to the SFG data. This finding allows us to understand the reason why the Gouy-Chapman model fails to explain surface potential results for subphases containing divalent or trivalent ions, and may be relevant for the application of calixarenes in sensing.

Application of hand-held and portable infrared spectrometers in bovine milk analysis.

A simple and fast method for the detection and quantification of milk adulteration was developed using portable and hand-held infrared (IR) spectrometers. Milk samples were purchased from local supermarkets (Columbus, OH, USA) and spiked with tap water, whey, hydrogen peroxide, synthetic urine, urea, and synthetic milk in different concentrations. Spectral data were collected using mid-infrared (MIR) and near-infrared (NIR) spectrometers. Soft independent modeling of class analogy (SIMCA) classification models exhibited tight and well-separated clusters allowing the discrimination of control from adulterated milk samples. Partial least-squares regression (PLSR) was used to estimate adulteration levels, and results showed high coefficients of determination (R(2)) and low standard errors of prediction (SEP). Classification and quantification models indicated that the tested MIR systems were superior to NIR systems in monitoring milk adulteration. This method can be potentially used as an alternative to traditional methods due to their simplicity, sensitivity, low energy cost, and portability.