Non-linear rheological (LAOS) behavior of sourdough-based dough

Effect of oleic acid-rich rapeseed oil on the physicochemical, rheological, and structural characteristics of wheat dough

Some wheat-based foods require different doses of oil to moderate quality of dough during processing and the influence mechanisms remain unclear. Therefore, the effect of rapeseed oil addition on physicochemical characteristics and fine structure of dough and underlying mechanism were elucidated by rheometer, scanning microscope and molecular spectroscopic method. Results showed that compared with native dough (without exogenous rapeseed oil), the addition of rapeseed oil changed the fine structure, improved extensibility, but reduced viscoelasticity of the dough. Moreover, high addition especially 20 wt% oil (based on wheat flour) significantly changed gelatinization and retrogradation behaviors of the dough, whilst disrupted gluten network and increased random coil content (32.1%) of dough except that decreased its α-helix (21.2%), β-sheet (23.1%), disulfide bond (7.9 μmol/g) compared with native dough which were 16.3%, 29.2%, 33.1%, 11.0 μmol/g, respectively. Results in the study could provide a certain understanding for application of vegetable oils in wheat-based products.

Functionality differences between esterified and pregelatinized esterified starches simultaneously prepared by octenyl succinic anhydride modification and its application in dough

Octenyl succinic anhydride (OSA)-modified starches have gained widespread interest, but the modification can produce two starches with different states ignored. Herein, the two types of starches, esterified starch (ES) and pregelatinized esterified starch (PES), prepared by OSA modification were separated, and their structural and functional characteristics were comprehensively explored. Results showed that compared with native starch (NS), ES and PES exhibited high water-holding capacity, solubility, and swelling power and significantly decreased pasting temperature and thermal stability. Dynamic rheological tests illustrated that OSA modification changed the rheological behavior of starches. Fourier transform infrared spectroscopy confirmed that PES with higher degree of substitution showed more obvious ester carbonyl and carboxylate groups than ES. Laser confocal micro-Raman spectroscopy revealed that the short-range molecular order of ES, especially PES, decreased after modification. X-ray diffraction indicated that OSA modification disrupted the crystalline structure of starch, and that more amylose-lipid complex was formed in PES. Scanning electron microscopy showed that OSA modification eroded starchs surface and reduced its smoothness, and significantly disrupted PES integrity. ES and PES could be developed as food additives for retrogradation inhibition of dough. These results provide new insights into OSA modification and expand its functional application in foods.

Identification and biotechnological characterisation of yeast microbiota involved in spontaneous fermented wholegrain sourdoughs

BACKGROUND

New strategies in the cereal-based industry has brought about the elaboration of new sourdoughs with better microbial stability and safety as well as nutritional value such as those based on wholegrain flours. This has led to an increasing interest in the selection of adapted yeasts for using them as new starters. Therefore, this study aimed to isolate, identify, and characterise diverse yeast strains from wholegrain spontaneous sourdoughs.

RESULTS

Three wholegrain sourdoughs (wheat, rye, and oat) were fermented and monitored for 96 h. Minimum pH values ranged from 3.1 to 3.5 while maximum yeast counts were reached at 72 h. A total of 76 yeast isolates were identified by polymerase chain reaction random amplification of polymorphic DNA (PCR-RAPD) and catalogued in six different species by sequencing the internal transcribed spacer (ITS) region. The major species were Candida glabrata, Saccharomyces cerevisiae, Kazachstania unispora, and Wickerhamomyces anomalus. The studied kinetic parameters of the growth curves (λ, G, ODmax , and μmax ) and the fermentation capacity allowed to ascertain that 12 and 5 strains, respectively, were better than baker's yeast control. The fibre assimilation ability (cellulose, xylose, and β-glucan) was observed in the 27% of the strains and only four strains showed phytase activity.

CONCLUSIONS

The yeast population in the three wholegrain sourdoughs were variable along the fermentation time. Genetic identification showed that strains and species presented a different trend for each sourdough although common species were determined (e.g., W. anomalus). Candida glabrata (4T1) and Saccharomyces cerevisiae (3A6) showed, respectively, better kinetics and impedance results than the positive control, while W. anomalus (C4) was notorious in fibre assimilation and phytase degradation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A critical study of the nonlinear rheological properties in major classes of foods using the Sequence of Physical Processes (SPP) method and the Fourier Transform Coupled with Chebyshev Decomposition (FTC) method

The nonlinear rheological behaviors of three different classes of foods (emulsion, suspension, and elastic network) were studied and analyzed using the Rogers Sequence of Physical Processes (SPP) method and the Ewoldt-McKinley method of coupling Fourier Transform with Chebyshev Decomposition (FTC). SPP analysis led to instantaneous rheological parameters G't and G″t at any point in time, providing a more accurate picture of the linear viscoelastic region and crossover points by the 3D amplitude sweep. When G't is plotted against G″t, the resulting graph is a deltoid which offers a detailed and distinctive intracycle behavior of each class of food. Analyzing the revolution of deltoids with increasing strain allows for the determination of a critical strain, beyond which irreversible network breakdown occurs. The strain range between the linear viscoelastic limit and the critical strain found in SPP is comparable to the MAOS region as determined with FTC. Under increasing amplitude, predominantly elastic networks showed a gradual structural rearrangement, while more erratic and abrupt changes were observed in the suspension and emulsion we studied. Under increasing frequency, elastic responses dominate viscous responses in all samples due to the shorter experimental time, allowing less relaxation.

Effect of Cold Atmospheric Pressure Argon Plasma Jet Treatment on the Freeze-Dried Mucilage of Chia Seeds (Salvia hispanica L.)

In the present study, the effects of the treatment of chia seeds with a cold atmospheric pressure plasma jet (CP) using argon as a working gas for different times (30, 60, and 120 s) on the rheological, structural, and microstructural properties of the freeze-dried mucilages at -54 °C were investigated. All mucilage gels showed pseudoplastic flow behavior, and CP treatment of chia seeds increased the viscosity of mucilages, probably due to the cross-linking between polymer molecules. The dynamic rheological analysis revealed that all mucilages were elastic gels and that CP treatment improved the elastic properties in a treatment time-dependent manner. Large amplitude oscillatory shear (LAOS) results showed that freeze-dried mucilages showed Type I strain-thinning behavior. Similar to small amplitude oscillatory shear (SAOS) results, CP treatment has affected and improved the large deformation behavior of mucilages depending on treatment time. Meanwhile, Fourier transform infrared spectroscopy (FTIR) revealed the incorporation of hydroxyl groups onto the surface and the formation of C-O-C glycosidic bonds during plasma treatment. Scanning electron microscope (SEM) micrographs showed the formation of denser structures with CP treatment time. Regarding color properties, CP treatment decreased the lightness values of mucilages. Overall, this study showed that CP is an effective way to modify both the SAOS and LAOS properties of freeze-dried chia mucilage and improve viscosity.

Temperature-dependent properties of fat in adipose tissue from pork, beef and lamb. Part 2: rheology and texture

Matching the texture of fat in plant-based meat alternatives requires an in-depth understanding of the rheology of animal adipose tissue which, to-date, remains under-studied. Here, we characterised the small and large deformation behaviour of back fat from pork, beef, and lamb, with the underlying goal being the establishment of the temperature-dependent structure-function relationship governing the texture and rheology of adipose tissue. The dynamic rheological behaviour of the back fats was characterised via frequency and amplitude sweeps and large amplitude oscillatory strain (LAOS), as well as texture analysis via puncture tests. At 20 °C, prior to heating, the small and large deformation properties of adipose tissue were dominated by the solid fat phase within the adipose cells. Upon heating to 80 °C, with the fat phase molten, the protein network underpinning the structure of the back fats conferred elastic behaviour to the tissues, and the now-molten oil partly leaked from the adipocytes into the surrounding interstitial space. Upon re-cooling, a bicontinuous network of fat crystals and protein contributed to back fat rheology. Large deformation rheology revealed animal species-specific differences. Prior to heating, pork back fat was characterised by soft yielding behaviour while beef and lamb back fat showed abrupt yielding and intra-cycle strain stiffening. Post-heating, lamb showed the highest stiffness, compared to pork and beef, as well as non-linearities in its stress-strain relationship obtained via LAOS. Such fundamental understanding is essential to provide the required insights to replicate the functionality of adipose tissue using plant-based materials.

Characterization and Selection of Potential Antifungal Lactic Acid Bacteria Isolated From Turkish Spontaneous Sourdough

The aim of this research was to investigate the antifungal potential of lactic acid bacteria (LAB) isolated from Turkish spontaneous sourdough collected in summer and winter seasons from 25 different small bakeries in Trabzon, Giresun, Ordu, and Samsun. Lactic acid bacteria (933 isolates) were screened for inhibition of three common food spoilage molds (Aspergillus flavus, Aspergillus niger, and Penicillium expansum). Eight LAB isolates identified as Weissella cibaria 908, Lactiplantibacillus plantarum subsp. plantarum 2114, Leuconostoc pseudomesenteroides 2619, L. plantarum subsp. plantarum 2702, Fructilactobacillus sanfranciscensis 2709, Levilactobacillus brevis 2216Y, L. pentosus Y118, and L. plantarum subsp. plantarum Y201 by 16 S rRNA sequencing, which were found to have high antifungal activity against all the test molds. The antifungal activity of cell free supernatants from LAB isolates was not altered after thermal treatment and proteolytic enzyme proteinase K. The cell free supernatants obtained from LAB showed a high antifungal effect against molds with inhibition zone diameter up to 20 mm at pH 3.0, but no inhibitory activity was determined after pH neutralization. Moreover, all cell free suspension samples were able to maintain their efficacy up to a 1:4 dilution. The antifungal activity of supernatants was mostly related to organic acid content, especially lactic acid ranged from 4.33 to 8.41 g/L. The results indicated that eight bacterial isolates obtained from spontaneous Turkish sourdough could constitute biopreservative cultures, which may be used in food industry.

A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research

The practice of sourdough bread-making is an ancient science that involves the development, maintenance, and use of a diverse and complex starter culture. The sourdough starter culture comes in many different forms and is used in bread-making at both artisanal and commercial scales, in countries all over the world. While there is ample scientific research related to sourdough, there is no standardized approach to using sourdough starters in science or the bread industry; and there are few recommendations on future directions for sourdough research. Our review highlights what is currently known about the microbial ecosystem of sourdough (including microbial succession within the starter culture), methods of maintaining sourdough (analogous to land management) on the path to bread production, and factors that influence the sensory qualities of the final baked product. We present new hypotheses for the successful management of sourdough starters and propose future directions for sourdough research and application to better support and engage the sourdough baking community.

Nonlinear (Large-Amplitude Oscillatory Shear) Rheological Properties and Their Impact on Food Processing and Quality

Large-amplitude oscillatory shear (LAOS) testing has been increasingly used over the past several decades to provide a fuller picture of food rheological behavior. Although LAOS is relatively easy to perform on a wide variety of foods, interpretation of the resulting data can be difficult, as it may not be possible to link the results to food components, microstructural features or changes, or physicochemical properties. Several analysis methods have been developed to address this issue, but there is currently no standard method for foods. In food research, LAOS has mainly been used to investigate connections between food microstructures and rheological behaviors, although there have been some studies on connections between food LAOS behaviors and processing or sensory behaviors. LAOS has the potential to be a valuable tool for investigating food structure-function-texture relationships, but much work remains to develop these relationships, particularly in the area of connecting LAOS to sensory attributes.

Exploration of the natural waxes-tuned crystallization behavior, droplet shape and rheology properties of O/W emulsions

Lipid crystallization in O/W emulsions is essential to control the release of nutrients and to food structuring. While few information is involved in adjusting and controlling the performance of emulsions by adjusting oil phase crystallization behavior. We herein developed a novel strategy for designing lipid crystallization inside oil droplets by natural waxes to modify the O/W emulsion properties. Natural waxes, the bio-based and sustainable materials, displayed a high efficiency in modifying the crystallization behavior, droplet surface and shape, as well as the overall performance of emulsions. Specifically, waxes induced the formation of a new hydrocarbon chain distances of 3.70 and 4.15 Å and slightly decreased the lamellar distance (d₀₀₁) of the single crystallites, thus forming the large and rigid crystals in droplets. Interestingly, these large and rigid crystals in droplets tended to penetrate the interface film, forming the crystal bumps on the droplet surface and facilitating non-spherical shape transformation. The presence of rice bran wax (RW) and carnauba wax (CW) induced the droplet shape into ellipsoid and polyhedron shape, respectively. Furthermore, the uneven interface and non-spherical shape transformation promoted the crystalline droplet-droplet interaction, fabricating a three-dimensional network structure in O/W emulsions. Finally, both linear and nonlinear rheology strongly supported that waxes enhanced the crystalline droplet-droplet interaction and strengthened the network in O/W emulsions. Our findings give a clear insight into the effects of adding natural waxes into oil phase on the crystalline and physical behavior of emulsions, which provides a direction for the design and control of emulsion performance.

Physicochemical Effects of Lactobacillus plantarum and Lactobacillus casei Cocultures on Soy-Wheat Flour Dough Fermentation

In contemporary food production, an important role is given to the increase in the nutritional quality of foodstuff. In the bakery industry, one of the main cereals used is wheat flour (WF), which creates bread with proper sensory evaluation but is nutritionally poor. Soy-flour (SF) has increased nutrient content, and its consumption is recommended due to several health benefits. Dough fermentation with lactic acid bacteria (LAB) increases bread shelf life, improves flavor, and its nutritional quality, mostly due to its high organic acid production capability. In the present study, the addition of SF to WF, through fermentation with the cocultures of Lactobacillus plantarum and Lactobacillus casei was analyzed. Three different batches were performed by using WF supplemented with SF, as follows: batch A consisting of 90% WF and 10% SF; batch B-95% WF and 5% SF; batch C-100% WF. The fermentation with these two LABs presented several positive effects, which, together with increased SF content, improved the dough's rheological and physicochemical characteristics. The dynamic rheological analysis exhibited a more stable elastic-like behavior in doughs supplemented with SF (G' 4936.2 ± 12.7, and G″ 2338.4 ± 9.1). Organic acid production changes were the most significant, especially for the lactic, citric, and tartaric content.

The Effect of Sodium Reduction by Sea Salt and Dry Sourdough Addition on the Wheat Flour Dough Rheological Properties

The aim of this research was to investigate a technological approach to decrease the sodium content from bakery products in order to respond to the World Health Organization (WHO)'s recommendation to reduce dietary salt intake. Due to the fact that sodium chloride is one of the main ingredients from baking products that affects dough rheology and therefore the technological process of the bakery products, it is important to evaluate these properties. This study analyzes the effect of sea salt with low sodium content (SS) and dry sourdough from wheat flour (SD) as substitutes for sodium chloride on dough rheological properties and on mixing, extension, pasting, and fermentation process by using Farinograph, Extensograph, Amylograph, Falling Number, and Rheofermentometer devices. The results were analyzed using response surface methodology. SS presented a strengthening effect on the gluten network whereas SD presented a weakening one. On extension properties, SS and SD presented a significant positive effect (p < 0.01) on resistance to extension (R50) and maximum resistance to extension (Rmax) values. For pasting properties, SS increased peak viscosity and falling number values whereas SD decreased them. On fermentation properties, SS decreased the maximum height of gaseous production and total CO2 volume production and increased the retention coefficient whereas SD presented an antagonistic effect on these parameters.