Food Analytical Methods最新文献

This work proposes a fast and accurate method based on near-infrared (NIR) spectroscopy with partial least-squares discriminant analysis (PLS-DA) and aquaphotomics to identify toxic honeys. PLS-DA was used to construct an optimal model for distinguishing toxic honey from a non-toxic honey. The models based on preprocessed NIR spectra have an accuracy of 92.73% and were more accurate than the model based on raw NIR spectra. Based on the aquaphotomics analysis of the first overtone of water (1300–1600 nm), we found that the 1398 nm, 1440 nm, and 1472 nm bands can be used as markers to distinguish toxic honeys. Compared to non-toxic honeys, gelsemium elegans -containing toxic honeys have a significantly smaller number of water molecules with multiple hydrogen bonds, due to the hydrogen bonding of the C–O–C, C = O, and NH₂ groups of gelsemine and koumine. These groups replace hydrogen bonds between glucose/polysaccharide molecules and water.

In this study, a validated analytical method based on liquid chromatography/electrospray ionization-selected reaction monitoring/mass spectrometry (LC/ESI-SRM/MS) was developed for dipeptides in a functional food, fermented brown rice and rice bran with Aspergillus oryzae (FBRA). The aim of this study was to screen and quantify dipeptides in the water-soluble fraction of FBRA. There are few studies focusing on dipeptides in FBRA, even though FBRA is expected to contain bioactive peptides: FBRA or its aqueous extract has shown variety of biological activities. An anti-hypertensive dipeptide was found in similar rice bran products digested by thermolysin. Dipeptides are the smallest class of peptides, and many show a variety of biological activities. Some bioactive peptides are widely found in fermented foods. However, because dipeptides are generally too polar to be retained on versatile LC columns, such as octadecylsilyl columns, dipeptides have been often overlooked and not quantified because of the analytical difficulties. The LC was performed using a porous graphitic carbon column with the mobile phases of 0.1% formic acid/0.1% trifluoroacetic acid/1% tetrahydrofuran in water and acetonitrile. The stable isotope-labeled internal standards and SRM for dipeptides made it possible to develop a validated method. Five dipeptides were identified and quantified in FBRA in much higher concentrations than related materials (malted brown rice, rice bran, brown rice, and white rice) as follows: Ile-Arg, 82.1 µg/g; Ala-Phe, 27.8 µg/g; Ala-Tyr, 31.6 µg/g; Val-Phe, 46.3 µg/g; and Ile-Tyr, 49.9 µg/g. This method was simple and robust and would be applicable for other functional foods.

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Thermosonication is a treatment that combines ultrasound power and mild temperatures. In this study, thermosonication was used to identify a new optimized model to maximize phenolic content, antioxidant capacity, and balsam yield of extract. A central composite design was employed to investigate the effects of ethanol concentration (50–100%), temperature (30–70 °C), time (10–50 min), and solid solvent ratio (1:100–1:300 g/mL). The effectiveness of the optimized method was compared to conventional solid-liquid extraction methods that carried out following condition: 75% ethanol concentration, 50 °C, and 1:200 g/mL solid solvent ratio during 24 h. Under optimal conditions (90% ethanol, 51 °C, 32 min, and 1:300 g/mL solid solvent ratio), total phenolic content (252.74 mg GAE/g), flavonoid content (222.32 mg CE/g), antioxidant activity (1.43 mmol TEAC/g), and (71.99%) were greater than the conventional extraction. The quality of propolis extract varies greatly depending on the source, extraction parameters, and processing procedures. Therefore, balsam yield, which represents the soluble fraction of propolis, might be considered as a crucial quality measurement. Thirteen bioactive compounds were quantified by LC-MS/MS. Ferulic acid (5.31–6.55 mg/g propolis) was found major phenolic acid while quercetin (0.14–0.15 mg/g propolis) was the major flavonoid. Also, taxifolin was identified for the first time in propolis. In addition, close R² and adj-R² values and the results of validation study demonstrated that the new model was fitted well and highly efficient method to produce high-quality propolis extract.

Monitoring the quality of food products is very important, due to the fact that substances potentially harmful to consumers may be formed during production and storage. In addition, vegetal oils are subject to falsification, which is based mainly on mixing and adding other, usually cheaper equivalents or providing false data on the composition and origin. In this way, the path from a very healthy product to a product that has a negative impact on the human body is very short. In this study fluorescence spectra and fluorescence decay kinetics of selected cold-pressed oils were characterized and the origin of the observed fluorescence bands was discussed. The obtained fluorescence characteristics were found to be the unique fingerprints of the individual oils and showed evident differences which arise from specific qualitative and quantitative compositions of the oils. The most apparent differences in the shape of fluorescence bands were observed in the emission spectrum at excitation wavelength 350 nm and in the excitation spectrum recorded at emission wavelength 500 nm. The obtained results show the utility of the applied steady-state and time –resolved fluorescence measurements in the identification of the tested vegetal oils.

The typical quality attributes of chocolate, such as its glossy appearance, hard and brittle texture, sharp melting, and fat bloom resistance, are determined by the process conditions under which solidification occurs. It is therefore reasonable to test the success of this process from their solid form through thermal, textural, and/or optical analysis. However, the solidification process of chocolate consists of a dynamic pre-crystallization step and a subsequent static crystallization step that relies on the crystallization of cocoa butter in its matrix. Each of these crystallization steps has a different mechanism and target. Additionally, the flow parameters such as apparent viscosity and yield stress during each crystallization step change and may affect the subsequent process steps. This work evaluates the possibility of performing rheological tests to follow changes in the flow behavior of dark chocolate during and immediately following pre-crystallization, as well as during solidification. Different tempering protocols, consisting of distinct time and temperature profiles, were performed by manually stirring and scraping the molten chocolate from a glass beaker in temperature-controlled water baths. Selected protocols were mimicked in the rheometer equipped with sandblasted parallel plates by performing a rotational test with temperature ramps to monitor changes in flow behavior. Key experimental settings including gap size, shear rate, pre-conditioning temperature, and residential time are discussed in this paper. Thermal and shear effects attributed to the evolution of apparent viscosity can be monitored within different phases of pre-crystallization. The flow curves of tempered chocolates from corresponding manual and rheometer tempering protocols, as well as the melting profiles upon their solidification, were comparable, reproducible, and indicating well-tempered chocolate characteristics. Furthermore, it was possible to follow up static crystallization in the rheometer after tempering. Thus, rheometrical techniques are proven to be a useful tool to monitor flow behavior changes in different phases of the solidification step in chocolate manufacturing and may provide important rheological data of molten, pre-crystallized, and solid chocolate.

Honey samples have been widely evaluated regarding the presence of degradation products as an index quality control, for example, hydroxymethylfurfural (HMF) in the presence of carbohydrates. The monitoring of HMF strategy can be a challenge; however, catalyst-based electroanalytical approaches can overcome it. This work aims the use of propolis to promote the anchoring of carbon nanotubes and Ni²⁺ onto the electrode surface, as well as the synthesis of nickel oxyhydroxide. The modified electrode was applied as an electrochemical sensor in the determination of HMF and total carbohydrates, and the quantification of HMF in honey samples. The sensor has shown high sensitivity to successive additions of the evaluated species, presenting LOD of 0.18 and 0.051 mmol L⁻¹ for HMF and total carbohydrates, respectively. In the analyses of honey samples, recovery values between 91.8 and 107% of HMF were achieved. Therefore, the proposed modified sensor showed potential for use as a greener alternative for honey quality control.

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Labneh is a dairy product highly consumed in Lebanon, prepared from straining yogurt. Because there is a lack of surveillance of the antimicrobial residues (AMRs) in milk and dairy products in Lebanon, this project was launched to develop a screening method for the detection of AMRs in labneh. In this study, we optimized a multi-residue screening method to detect 71 AMRs based on liquid–liquid extraction using buffered acetonitrile with 2 M ammonium acetate followed by freezing out the supernatant for 30 min at −23 °C. The extracts were then analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). This method was then validated against the Guidance (EU) CRLs 2010/01. The performance of the method showed a good specificity with no false negative rate and detection capabilities (CCβ) were below maximum residue levels (MRLs) for all analytes. In addition, this method demonstrated acceptable recoveries estimated in the range 70–130% for 92% of the analytes and the precision was below 30% except for a few macrolides and some β-lactams with an intra-lab reproducibility ranging between 7.30–40.61% and 2.90–47.85%, respectively. Our results showed that the developed method can be applied as a screening method and with acceptable variation in quantitation for the majority of AMRs.

Increasing worldwide food demand as a result of the increasing population has led to an increase in vegetable oil prices. Olive oil, one of the most popular edible oils, is regrettably commonly adulterated by the addition of a different, less expensive oil to lower its price. As a result, many processes are carried out on edible and olive oil is one of the most cheated products today. Microwave dielectric technique (MW), in parallel with Time Domain Nuclear Magnetic Resonance (TD-NMR) technique, has started to be used in food analysis because it can analyze the content of the product, which cannot be distinguished by sensory characteristics in a simple, fast and high-efficiency way.In this study, spin–lattice (T₁) and spin–spin (T₂) relaxation times of edible oils were measured. Dielectric permittivity constants Ɛ₁ and Ɛ₂ have also been measured from 10 MHz to 20 GHz. It is observed that spin–spin (T₂) and spin–lattice (T₁) relaxation times of pure olive oil are shorter than those of sunflower oil and that T₁ and T₂ are shorter for riviera olive oils than for extra virgin olive oils. It was found that the T₁ and T₂ values increased with the increase in temperature in the measurements based on the investigation of the impact of temperature on the relaxation times. The highest Ɛ₁ values are found in sunflower oils, while the lowest Ɛ₁ values are found in riviera olive oil. As is well known, the amounts of oleic and linoleic acid in edible oils also affect the T₁-T₂, viscosity, and Ɛ₁-Ɛ₂ values. As a result, relaxation times and dielectric parameter constants are used to categorize and distinguish edible oils, particularly extra virgin and riviera olive oils.