Food Structure-Netherlands最新文献

Crystallization behavior within oil-in-water emulsion is a key factor for the properties and stability of many food products. Confocal Raman microscopy is a promising method to study such complex structures in situ. This study aimed at evaluating the feasibility of confocal Raman microscopy for visualizing milk fat crystallization and establishing a reliable data acquisition and processing methodology. Milk fat globules from raw milk were fixated in an agarose gel and crystallized at different temperatures. Confocal Raman microscopy was applied to collect two-dimensional area scans and supporting images were obtained by polarized light microscopy. The results revealed differences in lipid characteristics, crystal formation, and spatial distribution as a result of crystallization. Specific C-C stretching vibrations at 1063, 1083, and 1125 cm-1 were found to indicate lipid chain mobility and provide quantitative information on crystallinity. Additionally, the study successfully identified the triple-layered milk fat globule membrane. Different approaches for processing spectroscopic data were compared, emphasizing the importance of proper data handling. This novel spectroscopy imaging approach has significant potential in enhancing our understanding of structural heterogeneities of crystallized structures within complex food matrices.

Polyethylene terephthalate (PET) is a commonly used polymer in many industry sectors including confectionery industry. In the latter, PET is utilized for single-use moulds for chocolate manufacturing. Despite the broad application of PET in these areas, information regarding its influence on chocolate gloss and surface properties is not available. Meanwhile, it is already well established that fat crystal modification influence these properties (including gloss) distinctly. To bridge this disparity, this study examined how amorphous and glycol-copolymerized PET sheets influence non-pre-crystallised and pre-crystallised dark chocolate properties throughout a 28-day storage period. Polymorphic properties of cocoa butter were analysed via DSC. Non-pre-crystallised and pre-crystallised chocolate surfaces were characterised regarding colour, gloss, polarity, adhesion, roughness, and topography. While pre-crystallised chocolate shows consistent results, non-pre-crystallised chocolate experiences considerable changes in surface properties due to fat crystal transitions during storage. The findings show that the polymorphic state had a major impact on chocolate surface properties. Furthermore, results demonstrated that the type of PET had a significant impact on chocolate surface properties as well. Pre-crystallised chocolate gloss was significantly impacted by the choice of PET contact material. As a result, pre-crystallised chocolates exhibited a larger tendency to gloss inhomogeneities following amorphous PET monolayer sheet contact.

The gelation behaviour of two different pea protein isolates and one soy protein isolate were investigated with a focus on the role of the protein properties. Protein solubility was the lowest in pH 3 citrate-phosphate buffer (<10% w/w), increased in pH 7.4 phosphate-buffered saline (12–21% w/w), and was the highest in pH 7.6 MilliQ water (∼20–40% w/w). Heat-induced gelation conditions for the protein sources were sensitive to both the soluble and the insoluble fractions as obtained during extraction. At low protein concentrations (≤5% w/v), the proteins started to lose their viscoelastic behaviour and exhibited predominantly viscous properties. Fitting of the fractional Kelvin-Voigt model to the frequency sweeps showed an increase in the fractal gel strength with increasing protein concentration. Secondary structures of the soluble species showed mostly unordered proteins, suggesting that the proteins were denatured during the commercial extraction process although gelation has to date been suggested to be highly dependent on the denaturation of soluble proteins. Synchrotron Radiation Circular Dichroism measurements of the insoluble proteins showed a significant amount of ordered protein structures. SEM imaging of the gels also suggested a new gelation pathway in which insoluble proteins act as dispersed fillers within a continuous matrix of soluble proteins. This research elucidated the role of different protein fractions, globulins and albumins, and their secondary structure in the formation of a gel network and how this affects their viscoelastic behaviour.

Gloss is an important criterion for chocolate quality and hence consumer acceptance. Gloss inhomogeneities, meaning glossy and matt spots on chocolate surfaces, remain a problem as they occur even after apparently optimal pre-crystallisation and cooling of chocolates. The presented study dealed with clarifying the complex interactions between dark chocolate with different surface-active substance (SAS) in contact with several mould materials by focusing on changes in chocolate surface properties and formation of gloss inhomogeneites. Contact materials used were polycarbonates (PC) and silicone. They varied in surface properties, specifically in roughness and surface free energy (SFE). PGPR, soy, and sunflower lecithin were used as SAS to alter the chocolate mass’ interface properties. Beside mould material’s surface properties, gloss (inhomogeneities), color, surface topography, roughness, and SFE were examined. Results showed that gloss and its inhomogeneities were significantly influenced by the contact material. Compared to PC, silicone had a significantly different impact on chocolate’s SFE and roughness. Topography images obtained by Atomic Force Microscopy revealed microstructural variations in the different gloss areas. Contact material and SAS had an impact on the microstructure as well. A statistical analysis further revealed that the contact materials' SFE and its dispersive share influence the formation of gloss inhomogeneites.

Food structure and addition of encapsulated compounds can impact the gastro-intestinal digestion of food. Flaxseed oil was encapsulated by complex coacervation using soluble pea protein and gum arabic as shell materials, dried by either spray or electrostatic spray drying and incorporated into sourdough dough before baking. Three bread formulations were prepared using spray-dried (B-SD), electrospray-dried coacervates (B-ES) and free ingredients used in the encapsulation (B). The standardised semi-dynamic INFOGEST in vitro digestion method was used. Cumulated protein/free NH₂ release and cumulated free fatty acids (FFA) release were used to assess protein and lipid digestion. Coacervates were resistant to bread preparation since they were visible in B-SD and B-ES. The total release of protein, free NH₂ and FFA by the end of intestinal digestions ranged between 41.58–45.23%, 1.08–1.22 µmol/g protein and 22.26–63.54%, respectively. There were no significant differences between formulations. There was a statistically significant increase (p < 0.5) of about three times in FFA release between the oral and gastric phases. Our findings help to understand the behaviour of coacervates when incorporated into solid food. In this study, the delivery structures did not affect in vitro digestion and may be used to increase the polyunsaturated fatty acid content by 50%.

This study aimed to prepare soybean oil oleogels with glycerol monostearate (GMS) and native surfactin organogelators. The effects of surfactin addition on the properties and microstructure GMS oleogel properties were evaluated. Gelation time, rheological and thermal properties, microscopy, Fourier transform infrared spectra, X-ray diffraction patterns, and oil binding capacity were determined. Results showed that addition of surfactin shortened the gelation time, enhanced hardness, oil binding capacity, apparent viscosity and gel strength, reduced crystals size and melting temperatures, increased crystallization temperature. GMS-surfactin oleogels showed larger mechanical resistance on compression. Hydrogen bonds were the main force for the formation of three-dimension oleogel network. Surfactin addition changed the crystal structure and β and β′ coexisted in oleogels. Oleogels with more stable texture and desirable properties were formed due to the addition of surfactin. Results indicated that surfactin addition could adjust the properties and micro-structure of GMS oleogels.

Lipid oxidation is a major cause of product deterioration in protein stabilised oil-in-water food emulsions. The impact of protein emulsifiers on lipid oxidation and the stability depends on the specific type of protein emulsifiers used and the redox conditions in the emulsion. However, the exact impact of these protein emulsifiers at the oil-water interface on lipid oxidation and the mechanism of lipid-protein co-oxidation are currently unknown. Here, we developed a cryo-correlative light and electron microscopy (cryo-CLEM) platform for co-localising the oxidation of lipids and proteins. For this first implementation of cryo-CLEM for food oxidation studies we optimised specifically the part of cryo-fluorescence microscopy (cryo-FM) by adding parts that prevent fogging on the sample and enable homogeneous laser illumination. We showed that lipid oxidation in food emulsions can be observed at cryogenic temperature using fluorescence imaging of the fluorophore BODIPY 665/676 that we employed earlier as a lipid oxidation sensor at room temperature. Using cryo-transmission electron microscopy (cryo-TEM), we observed that more protein aggregates are found at the droplet interfaces in oxidized emulsions compared to fresh emulsions. Our cryo-CLEM platform paves the way for future cryo-correlative oxidation studies of food emulsions.

This study assessed the changes in processed and natural cheese during heating from 5 to 95 °C, at 2 °C per min, using confocal laser scanning microscopy (CLSM), Raman micro-spectroscopy and rheological analysis. The CLSM images showed that the cheese samples varied in fat droplet size and distribution. CLSM micrographs of processed cheese with lower fat content (<10%) showed no substantial structural changes during heating, which were consistent with the absence of cross-over in temperature rheology sweep curves. Cheese containing starch showed uniformly distributed fat and cohesive protein network, leading to reduced cheese flow. At temperatures > 70 °C, cheeses with a fat content ≥ 25% showed greater coalescence of fat globules, which finally merged into large fat pools. The results of this study demonstrate the potential of dynamic in situ CLSM and rheological analysis for evaluating the changes in cheese matrices during heating. The Raman spectral region corresponding to C-H stretching vibrations (2800–3000 cm^-1) could be used to track fat melting in cheese samples with minimum 10% fat.

Texture profile of meat-analog (MA) based fried food products is a complex structure, and rarely studied subject. MA-based fried products mechanical-texture-profile were considered as “fractal geometry” to characterize their textural properties by employing complex statistical approach namely multifractal analysis (MFA). Wheat and rice flour-based batter systems were used to coat the MA, and were fried (at 180 °C) for 2, 4, and 6 min in canola oil. Instrumental puncture test was employed to get mechanical-texture-profile of MA-based fried products and obtained profile was evaluated by MFA. Results revealed that batter-formulation and frying time (FT) impacts the evolution of textural attributes (hardness, brittleness, crispiness), moisture-fat profile and microstructural properties of MA-based coated fried product. The MFA outcomes (Singularity spectra & Rényi spectra) depicts that breakage structure (force distribution) of studied MA-based fried products are non-homogeneous and possesses multifractal scaling behavior. Higher heterogeneity of force distribution is observed in lower concentration of force at outer-crust region compared to inner-core region of coated MA. Heterogeneity of force distribution are positively correlated with FT. Batter-formulation showed substantial impact on texture-profile of MA-based coated fried products and consequently influenced the obtained multifractal parameters. Principal component analysis (PCA) reveals varying extent of correlation between moisture-fat, textural attribute, microporosity and selected multifractal parameters (Δα, Δfα, R-L, ΔD) of fried MA.

Industrial relevance

Complex structural pattern of batter coated fried meat-analog (MA)s mechanical texture profile have been successfully and statistically characterized by employing multifractal analysis. This study unraveled the interdependencies among batter-formulation, frying process, mass-profile, microstructure, textural attributes and multifractal parameters. Findings of this study could be used to customize textural attributes of the low fat-containing fried foods. Overall, this work will serve as a ground for designing the production process of emerging MA-based batter-coated fried product.