In this study, large amplitude oscillation shear (LAOS) test was used to investigate the nonlinear behavior of collagen (COL) over a wide range of mass fractions. The original COL material is used in food industry with mass fraction of 7.6% (w/w) and another six mass fractions (1.5%, 2%, 3%, 4%, 5%, and 6%) were prepared by diluting. The structure of COL was evaluated via Fourier transform infrared spectroscopy and COL surface morphology was studied via scanning electron microscope (SEM). The results showed that the storage and the loss modulus increase with increasing COL mass fraction and COL showed a weak strain overshoot behavior. The Lissajous-Bowditch curves showed a gradual transition from narrow elliptical to wider elliptical shaped loops as the strain amplitude increases and the third-order Fourier coefficients G3 '$$ {G}_3<^>{\prime } $$, G3 ''$$ {G}_3<^>{\prime \prime } $$ values were changed significantly with the collagen mass fraction. The morphology results showed that dilution does not affect the internal structure of the COL gels. The results from this work are important since the nonlinear rheological response under LAOS of industrial collagen with a high mass fraction has not been reported.Highlights The viscoelasticity is tested and quantified for different mass fractions of COL. Tested COL is used in the food industry and has a high mass fraction (MF) The novelty for COL is in the combination of MF and evaluation methods. The structure of COL is evaluated via Fourier transform infrared spectroscopy. The surface morphology was studied via a scanning electron microscope.
High-pressure processing (HPP) represents a promising alternative to conventional Holder pasteurisation (HoP) used by human milk banks worldwide. The objective of this study was to identify whether the HPP would achieve the same or better retention of the content of selected analytes than the HoP. Samples collected from 15 breast milk donors were processed in four ways: i) no treatment; ii) HoP; iii) HPP in cycles (350 MPa, 4 cycles); iv) continuous HPP (350 MPa, 20 min). The content of secretory immunoglobulin A (sIgA), lactoferrin and lysozyme was determined using commercially available ELISA kits, and the lipase activity was assessed using an A-lipase activity assay kit. Data were compared statistically using paired t-tests. HoP significantly reduced the content of lysozyme and lactoferrin as well as lipase activity (P < 0.001). Cycled HPP significantly decreased lipase activity (P = 0.002), while continuous HPP led to a significant decrease in lysozyme content (P = 0.001) and lipase activity (P = 0.014). Cycled HPP showed high retention of pretreatment levels of lysozyme-median 99 (88; 99%), lactoferrin-84 (66; 105%), and sIgA content-83 (28; 117%). Among the studied treatment regimens, the best preservation of initial levels of bioactive components was achieved using HPP at 350 MPa in cycles.
This study examines the effect of electron beam irradiation on behaviour of low-concentration collagen at varying boundary conditions under the squeezing flow. Two models are considered: perfect lubrication (ideal slip) and no-slip conditions. The experimental data were used to evaluate the parameters of a modified mathematical model. The results showed a significant impact of high irradiation doses on collagen material and the perfect lubrication model provided a better overall fit to the experimental data. This contribution enhances the understanding of the viscoelastic properties of low-concentration collagen under squeezing flow, providing insights into its flow behaviour which is essential for applications.
The substitution of illegal fish species poses economic, health and environmental risks. Identifying fish species, particularly closely related ones lacking external features, is a challenge. This study introduces an alternative approach using nuclear gene markers for positive detection, identification, and quantification of mitochondrial gene markers common in existing assays. We developed a universal primer targeting the parvalbumin (pvalb) beta gene, a common fish allergen with an amplicon size of 117 bp long. The developed fish-specific primer assay was tested on a diverse panel of 54 fish species, including commonly consumed species such as salmon, carp, and cod, along with non-fish species such as Buffalo, chicken and pork, and vegetables such as wheat, celery, and mint. The assay consistently identified the fish pvalb gene, demonstrating our assay's high specificity and effectiveness in detecting this gene in a variety of fish species. The assay exhibited a low limit of detection (LOD) of 5 pg, detecting trace DNA quantities. The assay also effectively quantified parvalbumin with good efficiency and linearity. These findings highlight pvalb as a reliable forensic tool for the identification of fish species. Implementing nuclear gene markers mitigates fish mislabelling and fraud, reducing economic and environmental impacts.
Chitin is a water insoluble nitrogen-containing polysaccharide made from N-acetyl-D-glucosamine containing β-(1→4)-linkages. In food, chitin is considered as a source of fiber with prebiotic properties to gut microflora. Chitin content varies widely in nature from 1% (yeasts) up to 64% (butterfly cuticles) and is mostly found in filamentous or mushroom forming fungi, insects and crustaceans. This spectrophotometric method is suitable for chitin quantitation (reported as glucosamine) in food raw materials like insects (mealworm larvae, crickets), shrimps, mushrooms and fungi in a research (non-routine) laboratory. To remove interferences, the sample is defatted (Soxhlet) prior to acid hydrolysis in 6M HCl. The color complex is developed after the addition of Katano's reagent (a mix of 0.05 mol/L sodium metasilicate, 0.6 mol/L sodium molybdate, 30% dimethyl sulfoxide and 1.42 mol/L acetic acid) at 70°C for 30 min and measured at 750 nm against blank. A five-point linear calibration (5-100 µg/mL) is used. Limit of detection is 3 µg GLCN/mL. The correlation (R2) with an HPLC method for chitin analysis is at least 0.93. • a reliable alternative to an HPLC method • does not require expensive equipment • deproteination by alkali is not necessary for most matrices - saves about 30% of time
