Browsing by Person "Jekle, Mario"

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Application of two-dimensional fluorescence spectroscopy for the on-line monitoring of teff-based substrate fermentation inoculated with certain probiotic bacteria
(2022) Alemneh, Sendeku Takele; Emire, Shimelis Admassu; Jekle, Mario; Paquet-Durand, Olivier; von Wrochem, Almut; Hitzmann, Bernd
There is increasing demand for cereal-based probiotic fermented beverages as an alternative to dairy-based products due to their limitations. However, analyzing and monitoring the fermentation process is usually time consuming, costly, and labor intensive. This research therefore aims to apply two-dimensional (2D)-fluorescence spectroscopy coupled with partial least-squares regression (PLSR) and artificial neural networks (ANN) for the on-line quantitative analysis of cell growth and concentrations of lactic acid and glucose during the fermentation of a teff-based substrate. This substrate was inoculated with mixed strains of Lactiplantibacillus plantarum A6 (LPA6) and Lacticaseibacillus rhamnosus GG (LCGG). The fermentation was performed under two different conditions: condition 1 (7 g/100 mL substrate inoculated with 6 log cfu/mL) and condition 2 (4 g/100 mL substrate inoculated with 6 log cfu/mL). For the prediction of LPA6 and LCGG cell growth, the relative root mean square error of prediction (pRMSEP) was measured between 2.5 and 4.5%. The highest pRMSEP (4.5%) was observed for the prediction of LPA6 cell growth under condition 2 using ANN, but the lowest pRMSEP (2.5%) was observed for the prediction of LCGG cell growth under condition 1 with ANN. A slightly more accurate prediction was found with ANN under condition 1. However, under condition 2, a superior prediction was observed with PLSR as compared to ANN. Moreover, for the prediction of lactic acid concentration, the observed values of pRMSEP were 7.6 and 7.7% using PLSR and ANN, respectively. The highest error rates of 13 and 14% were observed for the prediction of glucose concentration using PLSR and ANN, respectively. Most of the predicted values had a coefficient of determination (R2) of more than 0.85. In conclusion, a 2D-fluorescence spectroscopy combined with PLSR and ANN can be used to accurately monitor LPA6 and LCGG cell counts and lactic acid concentration in the fermentation process of a teff-based substrate. The prediction of glucose concentration, however, showed a rather high error rate.
Effect of refrigerated storage on some physicochemical characteristics of a teff‐based fermented beverage and the viability of the fermenting Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus used
(2022) Alemneh, Sendeku Takele; Emire, Shimelis Admassu; Jekle, Mario; Hitzmann, Bernd
Probiotic beverages made from cereals become interesting in the recent food industries. In this contribution, a fermented teff-based probiotic beverage was produced using the whole grain teff flour and co-culture strains of Lactiplantibacillus plantarum (LPA6) and Lacticaseibacillus rhamnosus GG (LCGG). Then, the effect of 25 days of refrigerated storage on cell viability (LPA6 and LCGG), and contents of sugars, organic acids, and titratable acidity (TA), as well as pH values were examined. Furthermore, pathogenic microorganisms, hygiene indicators, and sensory tests of the beverage were analyzed. Presumptive cell counts of LPA6 and LCGG were observed to decrease throughout refrigerated storage. Glucose, lactic acid, maltose, and acetic acid contents were significantly (p < 0.05) increased over storage time. Also, pH reduction and TA increment were observed in storage time. Examined pathogenic microorganisms and hygiene indicators were not detected in the beverage. Sensory analysis of the beverage after 10 days of refrigerated storage was accepted by the panelists. Novelty Impact Statement Throughout refrigerated storage of teff-based probiotic beverage sugars and organic acids were produced. Sensory attributes of the newly produced teff-based probiotic beverage were accepted by the panelist after 10 days of refrigerated storage. The pH of the teff-based probiotic beverage became more acidic throughout 25 days of refrigerated storage.
Effect of wet fractionation conditions and pulsed electric field on arabinoxylan and protein recovery from maize
(2025) Sukop, Ulrich; Hoefler, Katharina; Bender, Denisse; D’Amico, Stefano; Jekle, Mario; Schoenlechner, Regine; Domig, Konrad J.; Wang, Lili; Cao, Ruge
Maize wet fractionation by-products are primarily used as feed but offer potential for food applications. Arabinoxylans (AXs) and proteins are particularly valuable due to their network-forming properties, which depend on their molecular structure. This study assessed the effect of the steeping conditions (acid type and pH variation) combined with a pulsed electric field (PEF) as a strategy for recovering these polymers, while also evaluating their effect on the recovery yield, fraction composition, and key AX characteristics. The physical properties were studied in selected fractions to investigate the process-induced structural changes. Lactic acid and hydrochloric acid (pH 2.5) were most effective in enhancing AX and protein recovery in fiber-rich (FF) and protein-rich (PF) fractions, respectively, while acetic acid exhibited the lowest efficiency. However, bound polyphenols were best retained in the FF when lactic acid was used, indicating the lowest structural damage to AXs, compared to other acids and using a higher pH. Additional PEF pre-treatment significantly enhanced the release of proteins, dietary fiber, and fat from the FF while inducing physical modifications to the fractions (PF: higher protein unfolding, FF: improved water-binding, pasting when using PEF). These findings highlight the potential of optimizing the processing conditions to adjust the recovery of proteins and AXs from maize, while minimally affecting their functionality.
Four-dimensional (4D) printing of dynamic foods - definitions, considerations, and current scientific status
(2023) Fahmy, Ahmed Raouf; Derossi, Antonio; Jekle, Mario
Since its conception, the application of 3D printing in the structuring of food materials has been focused on the processing of novel material formulations and customized textures for innovative food applications, such as personalized nutrition and full sensory design. The continuous evolution of the used methods, approaches, and materials has created a solid foundation for technology to process dynamic food structures. Four-dimensional food printing is an extension of 3D printing where food structures are designed and printed to perform time-dependent changes activated by internal or external stimuli. In 4D food printing, structures are engineered through material tailoring and custom designs to achieve a transformation from one configuration to another. Different engineered 4D behaviors include stimulated color change, shape morphing, and biological growth. As 4D food printing is considered an emerging application, imperatively, this article proposes new considerations and definitions in 4D food printing. Moreover, this article presents an overview of 4D food printing within the current scientific progress, status, and approaches.
Hydration-induced reduction strategies of acrylamide in bakery products
(2025) Świacka, Jagoda; Jekle, Mario
Bread is a product made from cereals and/or cereal-based ingredients, which are combined with water or other water-containing liquids. Also, additional ingredients such as oilseeds, legumes, potato products, dairy products, spices, and vegetables may be incorporated into the dough. Products containing these ingredients can be referred to as special bakery products. However, the use of these additional ingredients has been raising food-safety concerns, particularly because of the possibly elevated levels of acrylamide detected in the final products. Acrylamide is a process contaminant, considered undesirable due to its potential carcinogenicity and is currently subject to various European food safety regulations. However, the acrylamide mitigation strategies defined so far for standard bakery products do not appear to be sufficiently effective for special bakery products. This is presumably due to the high levels of precursor molecules and the varying quality of the special ingredients. As a result, there are large variations in the levels of precursors, namely reducing sugars and asparagine in the dough, which consequently lead to unpredictably elevated acrylamide contamination. To address these problems and to gain a deeper understanding of acrylamide formation in special bakery products, further investigation is essential. Therefore, this thesis aimed to identify specific acrylamide precursors, to analyze acrylamide levels, and to assess the effectiveness of hydration-based approaches as mitigation measures for special bakery products. Mitigation was to be achieved either by eliminating the precursors or by adjusting processing conditions. After a theoretical introduction in Chapter I, a systematic investigation of two special ingredients, with a focus on their specific acrylamide precursors, was presented in Chapter II and Chapter III. Particular attention was drawn to potato flakes, known for their high asparagine content, and carrot strips, awaited to be high in reducing sugars. The effects of these ingredients in combination with varying water additions as hydration approach, were investigated using a model dough recipe. The model dough consisted of wheat flour type 550, water, NaCl, yeast and selected special ingredients. After baking, both bread crust and crumb were analyzed for acrylamide and in parallel, baking qualities of these bakery products were evaluated. Considering acrylamide contamination, increased water addition showed highly raw material-specific effects. In high-asparagine doughs, higher dough water addition tended even to increase acrylamide formation, presumably due to enhanced mobility of precursors. Interestingly, for the carrot-based doughs, the polyphenols emerged as a potential factor significantly reducing acrylamide formation at higher water additions, highlighting their relevance for future mitigation strategies. Due to the significant differences in the qualities of available carrot strips, shown in Chapter III, Chapter IV described the effects of origin, processing and drying methods on different quality features of dried carrot strips. For that, three carrot varieties were purchased and processed. Processing steps included blanching and drying methods, such as hot-air drying, vacuum drying, or freeze-drying. The impact of each processing method on quality of carrot strips, their acrylamide-forming potential, and the resulting acrylamide levels in model bakery products was analyzed. Blanching in particular, significantly reduced the acrylamide formation potential of the carrot strips. Freeze-drying consistently resulted in the highest concentrations of sugars, free asparagine, and β‑carotene for all carrot varieties, whereas the retainment of these compounds was inconsistent with other drying methods. Asparagine levels during storage were shown to fluctuate, with an initial increase and a following decrease, underlining the importance of timed processing to warrant constant product quality. Overall, the potential of carrot strips for acrylamide formation depended mostly on their variety and storage conditions, which determined primarily their precursor profile. To investigate a variety-unspecific acrylamide mitigation strategy, soaking was evaluated in Chapter V as an approach for products with dried carrot strips. Additionally, ultrasound-assisted rehydration was investigated as a method to enhance the diffusion of carrot matrix constituents. Regular soaking was compared with ultrasound-assisted rehydration (ultrasonic bath or sonotrode) regarding rehydration rate and leaching of sugars from the carrot strips. The kinetics of rehydration and diffusion were modelled using the ExpAssoc and the Peleg equations. Rehydrated carrot strips were then implemented in model breads and acrylamide concentration in the crust along with baking qualities were analyzed. Overall, longer rehydration led to higher water retention in the carrot strips and increased leaching of sugars and polyphenols. Both ultrasound-assisted rehydration and regular soaking led to reduced acrylamide levels in model breads up to 75%. Summarizing, this thesis systematically examined the addition of potato flakes and carrot strips to bakery products, identifying their critical acrylamide precursors, expected acrylamide levels, and characteristic changes in bread quality. It proved that rehydration is an effective acrylamide mitigation strategy for special bakery products, primarily by promoting precursor leaching and influencing reaction conditions. Overall, this thesis provides guidance on the target raw material qualities and presents (easy-to-apply) mitigation approaches for various manufacturers.
Ingenious wheat starch/Lepidium perfoliatum seed mucilage hybrid composite films: Synthesis, incorporating nanostructured Dy₂Ce₂O₇ synthesized via an ultrasound-assisted approach and characterization
(2025) Zinatloo-Ajabshir,Sahar; Yousefi, Alireza; Jekle, Mario; Sharifianjazi, Fariborz
In this study, Dy₂Ce₂O₇ nanostructures were fabricated using an environmentally friendly, ultrasound-assisted method. These nanostructures were then incorporated into a blend of wheat starch (WS) and Lepidium perfoliatum seed mucilage (LPSM), along with sodium montmorillonite (Na-MMT) nanoparticles. The composite films were produced through a casting method, combining these components to enhance the films' structural and functional properties. FTIR results confirmed the chemical interactions between the NPs and the biopolymeric matrix of the nanocomposites. SEM surface morphology and XRD crystallography results indicated that up to a 1 % weight ratio, the dispersion of Dy₂Ce₂O₇ in the nanocomposite matrix was uniform, while at higher percentages, due to nanoparticle aggregation, crystallinity increased. Interestingly, the elongation of nanocomposites containing Dy₂Ce₂O₇ increased, while their tensile strength and elastic modulus decreased. More than 92 % of UV radiation in the 240–360 nm range was absorbed with the inclusion of 1 % wt. Dy₂Ce₂O₇, and the water vapor permeability (WVP) significantly decreased. Among the Dy₂Ce₂O₇-based nanocomposites, TGA results showed that the WS/LPSM/MMT/Dy1 % sample had the highest thermal stability. Overall, based on the results of this study, the WS/LPSM/MMT/Dy1 % sample was introduced as a composite film with suitable physicochemical and mechanical properties for food and pharmaceutical packaging.
An innovative approach in the baking of bread with CO2 gas hydrates as leavening agents
(2022) Srivastava, Shubhangi; Kollemparembil, Ann Mary; Zettel, Viktoria; Claßen, Timo; Mobarak, Mohammad; Gatternig, Bernhard; Delgado, Antonio; Jekle, Mario; Hitzmann, Bernd
Gas (guest) molecules are trapped in hydrogen-bonded water molecules to form gas hydrates (GH), non-stoichiometric solids that resemble ice. High pressure and low temperature are typical conditions for their development, with van der Waals forces joining the host and guest molecules. This article study investigates the application of CO2 gas hydrates (CO2 GH) as a leavening agent in baking, with particular reference to the production of wheat bread. The main intention of this study is to better understand the complex bread dough formed by CO2 GH and its impact on product quality. This may enable the adaptation of CO2 GH in baking applications, such as those that can specifically influence wheat bread properties, and so the final bread quality. The present research further examines the comparative evaluation of yeast bread with the GH bread’s impact on bread quality parameters. The amount of GH was varied from 10 to 60%/amount of flour for the GH breads. The GH breads were compared with the standard yeast bread for different quality parameters such as volume, texture, and pore analysis. The results show that the bread with 20% and 40% GH obtained the best results in terms of volume and pore size. Moreover, this article also sheds some light on the future applications of the use of CO2 GH as leavening agents in foods. This knowledge could help to create new procedures and criteria for improved GH selection for applications in bread making and other bakery or food products.
Micro-scale shear kneading: Gluten network development under multiple stress-relaxation steps and evaluation via multiwave rheology
(2022) Vidal, Leonhard Maria; Braun, Andre; Jekle, Mario; Becker, Thomas
To evaluate the kneading process of wheat flour dough, the state of the art is a subsequent and static measuring step on kneaded dough samples. In this study, an in-line measurement setup was set up in a rheometer based on previously validated shear kneading processes. With this approach, the challenge of sample transfer between the kneader and a measurement device was overcome. With the developed approach, an analysis of the dynamic development of the dough is possible. Through consecutive stress–relaxation steps with increasing deformation, a kneading setup in a conventional rheometer is implemented. Fitting of the shear stress curve with a linearization approach, as well as fitting of the relaxation modulus after each kneading step, is a new way to evaluate the matrix development. Subsequently, multiwave rheology is used to validate the kneading process in-line. The shear kneading setup was capable of producing an optimally developed dough matrix close to the reference kneading time of 150 ± 7.9 s (n = 3). The linearization approach as well as the power-law fit of the relaxation modulus revealed gluten network development comparable to the reference dough. With this approach, a deeper insight into gluten network development and crosslinking processes during wheat flour dough kneading is given.
Microscopic analysis of gluten network development under shear load—combining confocal laser scanning microscopy with rheometry
(2023) Vidal, Leonhard Maria; Ewigmann, Hans; Schuster, Clemens; Alpers, Thekla; Scherf, Katharina Anne; Jekle, Mario; Becker, Thomas
A comprehensive in‐situ analysis of the developing gluten network during kneading is still a gap in cereal science. With an in‐line microscale shear kneading and measuring setup in a conventional rheometer, a first step was taken in previous works toward fully comprehensible gluten network development evaluation. In this work, this setup was extended by an in‐situ optical analysis of the evolving gluten network. By connecting a laser scanning microscope with a conventional rheometer, the evaluation of the rheological and optical protein network evolution was possible. An image processing tool for analyzing the protein network was applied for evaluating the gluten network development in a wheat dough during the shear kneading process. This network evaluation was possible without interruption or invasive sample transfer comparing it to former approaches. The shear kneading system was able to produce a fully developed dough matrix within 125% of the reference dough development time in a classical kneader. The calculated network connectivity values from frequency testing ranged over all samples was in good agreement with traditional kneaded wheat dough just over peak consistency.
Multi‐scale dough adhesion analysis: Relation between laboratory scale, pilot scale and human sensory
(2023) Vogt, Ulrike Therese; Kwak, Ju Eun; Fahmy, Ahmed Raouf; Laukemper, Rita; Henrich, Alexander; Becker, Thomas; Jekle, Mario
Undesired dough adhesion is still a challenge during the production of baked goods. There are various methods for determining the adhesive texture properties of dough. In the majority of scientific papers, dough stickiness is measured analytically by the force‐distance recording of dough detachment. In this study, we describe a new multi‐scale approach to compare dough adhesion phenomena in a laboratory, pilot sale and human sensory assessment. In it, the adhesive material properties of dough were investigated using a pilot scale toppling device representing dough adhesion behavior in the production process, in the laboratory by texture analysis with the Chen–Hoseney method and furthermore with a new, implemented non‐oral human sensory analysis. To simulate different dough adhesion behavior, the dough mechanical and adhesion properties were varied by applying dough‐modifying enzymes and different dough storage times. The structural changes in the different wheat dough system were compared by rheological characterization. By characterizing the different adhesion phenomena of the doughs, the sample with bacterial xylanase showed the highest values after 80 min of storage time in all three methods. Correlation analysis revealed a strong relationship between the detachment time (pilot scale) and human sensory assessment attributes (Force R = 0.81, Time R = 0.87, Distance R = 0.92, Stickiness R = 0.80) after 80 min of storage time. Even though human sensory assessment showed limits in the detectability of differences in dough adhesion behavior compared to the Chen–Hoseney method, it was better suited to predict machinability.
Structure formation in fruit preparations by fruit fermentates produced with exopolysaccharide-forming lactic acid bacteria
(2025) Festini, Silvan; Zipori, Dor; Wallisch, Marc; Weiss, Agnes; Neidhart, Sybille; Schmidt, Herbert; Jekle, Mario
Fruit preparations are intermediate food products that are primarily used in the dairy industry for the production of fruit yogurt or frozen desserts. Typically, they are stabilized by added hydrocolloids like pectins. The objective of this study was to investigate the potential replacement of conventional stabilizers by structure-forming fermentates produced by exopolysaccharides (EPS)-forming lactic acid bacteria (LAB). Peach puree was selected as fermentation matrix. Prior to 72 h of incubation, it was inoculated with either the heterofermentative LAB strain Levilactobacillus brevis TMW 1.2112 or the homofermentative LAB strain Pediococcus parvulus strain LTH 1110, both being known to produce EPS in form of β-D-glucan. The lyophilized fermentates were applied as stabilizers to produce strawberry fruit preparations. Flow curves, viscoelastic behaviour and shear stability were measured to investigate the effect of fermentate incorporation on the rheological properties of the products. A fermentatively induced effect was observed in terms of a 1.3-fold increase in viscosity of strawberry model fruit preparations with 10 % fermentate of Lv. brevis TMW 1.2112 compared to the addition of the same dose of fermentate blank. Further, increasing the fermentate blank dose from 10 % to 15 % resulted in a 2.4-fold viscosity increase of the model fruit preparations. High shear stability was found in all model strawberry fruit preparations. However, fermentation had no clear benefit in terms of viscoelastic behaviour and shear stability of the fruit preparations. Although the fermentatively induced thickening potential was limited, production of viscosity-increasing peach fermentate with minor changes in the sugar and amino acid profiles of the fruit proved to be feasible.
Texture modulation of starch‐based closed‐cell foams using 3D printing: Deformation behavior beyond the elastic regime
(2022) Fahmy, Ahmed Raouf; Jekle, Mario; Becker, Thomas
3‐dimensional printing is a novel processing method used for the design and manipulation of food textures. The systematic characterization and modulation of 3D printed food textures is imperative for the future design of sensory profiles using additive manufacturing. For 3D printed closed‐cell food foams, the clarification of the deformation behavior in relation to design parameters is of interest for the processing of customized food textures. For this reason, we studied the deformation behavior of 3D printed and thermally stabilized closed‐cell starch‐based foams beyond the elastic regime. Periodic spherical bubble configurations at different porosity levels were used to modulate the deformation behavior of the printed foams. From a processing perspective, the integration of in‐line thermal stabilization was used to eliminate post‐processing and to control the moisture content of the starch‐based system. Compression analysis combined with FEM simulations were performed to characterize the strain rate dependency of textural properties, the stress relaxation, and the foam's stress–strain behavior with respect to the design porosity and bubble distribution. Results showed that the stress relaxation is solely dependent on cell wall properties while different stress–strain regimes showed distinct dependencies on design parameters such as bubble size and distribution. Consequently, the precise control of the large deformation behavior of foods using 3D printing is challenging due to the superposition of structural and geometrical dependencies. Finally, through the presented approach, the structure‐deformation relations of 3D printed closed‐cell food structures are adequately described.
Towards sustainable biointelligent food design: structuring potential of plant-based materials exemplified using apricot seed oil oleogels and bigels through 3D food printing
(2025) Reinmuth, Evelyn; Fahmy, Ahmed Raouf; Ribette, Olivia; Jekle, Mario
Background/Introduction: Biointelligence in the approach of food additive manufacturing represents a significant advancement, enabling the reverse engineering and design of foods. Legislation restricting trans-fats has accelerated research into alternatives, but ingredients like saturated and trans fats play key roles in food quality and functionality. Oleogels are a promising replacement. Food additive manufacturing introduces a biointelligent approach, combining biological and technical components with information technology to optimize food design. This study investigates 3D printing of oleogel and bigel systems using apricot seed oil, aiming to assess their significance, applicability, and printability as sustainable alternatives to trans fats for innovative, resource-efficient food production. Methods: Apricot seed oil, rich in antioxidants and polyunsaturated fatty acids, was processed into plant-based oleogels and bigels. The material systems were incorporated into 3D printed food structures. Material characterization and techno-functional analysis were conducted to evaluate the suitability of apricot seed oil for structuring 3D printed foods and controlling food texture. Results: Adjusting the type and concentration of oil-gelator mixtures enabled tailored texture and lipid distribution to fit consumer preferences. Sustainability impacts were assessed at intermediate processing steps, demonstrating the value of holistic evaluations beyond technical factors. Discussion: Biointelligent 3D printing offers a platform to optimize sensory and sustainability qualities in food design. The integration of apricot seed oil into novel food matrices enables versatile nutritional product development, supporting researchers and industry stakeholders in advancing consumer-centric, sustainable production and consumption practices.