Multiscale analysis of triglycerides using X-ray scattering: implementing a shape-dependent model for CNP characterization.

In the last decade, research has focused on examining the fundamental interactions occurring in triglycerides, aiming to comprehend the self-assembly of crystalline nanoplatelets (CNPs) and their role in forming larger hierarchical structures essential for fat functionality. Microscopy research on CNPs frequently requires disruptive preparatory techniques, such as deoiling and sonication, to achieve quantitative outcomes. Conversely, X-ray scattering has proven to be an advantageous method for studying triglycerides, as little sample is needed to quantify the system's hierarchical structures. Specifically, ultra-small-angle X-ray scattering (USAXS) has emerged as a fitting technique for studying CNPs, owing to its length scale range falling between 25 nm and 3.49 µm. In this study, we characterized four different 30% fat dilutions of stearic acid-based fats in triolein, with various purities and preparation protocols. Samples were characterized by combining diverse microscopy techniques (cryo-SEM, TEM, polarized light and phase contrast microscopy) with synchrotron-radiation X-ray scattering (WAXS, SAXS, and USAXS). A shape-dependent model for the interpretation of USAXS data is proposed, overcoming some of the drawbacks linked to previously utilized models. CNPs are modeled as polydisperse parallelepipeds, and the aggregates are characterized by fractal dimensionality. This model offers novel insights into CNP cross-section, as well as aggregation. In the long run, we hope that the model will increase our understanding of CNP conformation and interactions, helping us design new fat systems on the mesoscale.

Effects of Genotype, Nitrogen, and Sulfur Complex Fertilization on the Nutritional and Technological Characteristics of Buckwheat Flour.

The present study investigated the effect of nitrogen fertilization (NF) at the levels of 0, 45, and 90 kg·ha-1 combined with selected sulfur complex fertilization (SCF) levels of 0 and 45 kg·ha-1 on the nutritional and technological characteristics of buckwheat flour from five varieties. The results showed that the genotype was a critical factor affecting the chemical composition and physicochemical properties of buckwheat flour. NF significantly increased protein, total starch, and amylose content as well as mineral composition but decreased particle size, color value, and water hydration properties. However, SCF enhanced the ash content and decreased the protein content but had no significant effect on the pasting temperature. In addition, the combination of NF and SCF significantly reduced granule size, water solubility, viscosity, and rheological properties with increasing fertilization levels. This study can guide the cultivation of buckwheat with the desired physicochemical properties and provide information for buckwheat-based products in the food industry.

From Nucleation to Fat Crystal Network: Effects of Stearic-Palmitic Sucrose Ester on Static Crystallization of Palm Oil.

Palm oil (PO), a semi-solid fat at room temperature, is a popular food ingredient. To steer the fat functionality, sucrose esters (SEs) are often used as food additives. Many SEs exist, varying in their hydrophilic-to-lipophilic balance (HLB), making them suitable for various food and non-food applications. In this study, a stearic-palmitic sucrose ester with a moderate HLB (6) was studied. It was found that the SE exhibited a complex thermal behavior consistent with smectic liquid crystals (type A). Small-angle X-ray scattering revealed that the mono- and poly-esters of the SE have different packings, more specifically, double and single chain-length packing. The polymorphism encountered upon crystallization was repeatable during successive heating and cooling cycles. After studying the pure SE, it was added to palm oil, and the crystallization behavior of the mixture was compared to that of pure palm oil. The crystallization conditions were varied by applying cooling at 20 °C/min (fast) and 1 °C/min (slow) to 0 °C, 20 °C or 25 °C. The samples were followed for one hour of isothermal time. Differential scanning calorimetry (DSC) showed that nucleation and polymorphic transitions were accelerated. Wide-angle X-ray scattering (WAXS) unraveled that the α-to-ß' polymorphic transition remained present upon the addition of the SE. SAXS showed that the addition of the SE at 0.5 wt% did not significantly change the double chain-length packing of palm oil, but it decreased the domain size when cooling in a fast manner. Ultra-small-angle X-ray scattering (USAXS) revealed that the addition of the SE created smaller crystal nanoplatelets (CNPs). The microstructure of the fat crystal network was visualized by means of polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM). The addition of the SE created a finer and space-filling network without the visibility of separate floc structures.

Destabilization of a model O/W/O double emulsion: From bulk to interface.

Oil-in-water-in-oil (O/W/O) double emulsions are considered an advanced oil-structuring technology that can accomplish multi-functions to improve food quality and nutrition. However, this special structure is thermodynamically unstable. This study formulated a model O/W/O double emulsion with standard surfactants, Tween 80 (4 %) and polyglycerol polyricinoleate (PGPR, 5 %), using a traditional two-step method with different homogenization parameters. Cryo-SEM and GC-FID results show that O/W/O emulsions were successfully formulated, and the release rate (RR) of medium-chain triglycerides (MCT) oil from the inner oil to the outer oil phase increased significantly with 2nd homogenization speed increasing, respectively. Interestingly, the RR of all samples reached about 75 % after 2 months of storage, suggesting that O/W/O emulsions were highly unstable. To explain the observed instability, dynamic interfacial tension and interfacial rheology were performed using a drop shape tensiometer. Results demonstrated that unadsorbed Tween 80 in the intermediate aqueous phase was a key factor in markedly decreasing the interfacial properties of the outer PGPR-assembled film by affecting the interfacial rearrangement. Additionally, it was found that the MCT release showed a positive correlation with the Tween 80 concentration, demonstrating that the formed Tween 80 micelles could transport oil molecules to strengthen the emulsion instability. Taken together, this study reveals the destabilization mechanism of model O/W/O surfactants-stabilized emulsions from bulk to interface, providing highly relevant insights for the design of stable O/W/O double emulsions.

An Impact Assessment of Par-Baking and Storage on the Quality of Wheat, Whole Wheat, and Whole Rye Breads.

Par-baking technology increases the production efficiency of bread. However, the degree of par-baking can vary significantly amongst product types and intended sales markets, leading to substantial differences in the quality attributes of the finished product. The objective of this study was to explore the impact of the degree of par-baking on the technological quality of wheat, whole wheat, and whole rye bread (95, 75, and 50% of full baking time). More specifically, this study focused on the starch pasting behavior of different flour formulations, the crumb core temperature during par-baking, and the influence of the degree of par-baking on the bread characteristics of (composite) wheat bread as a function of storage time. The quality attributes of par-baked bread (0 and 4 days after par-baking) and fully baked bread (0 and 2 days after full baking) were assessed. A reduction in the degree of par-baking from 95 to 50% resulted over time in 19.4% less hardening and 8.6% more cohesiveness for the re-baked wheat breads. Nevertheless, it also negatively impacted springiness (-9.1%) and adhesion (+475%). It is concluded that using the core temperature to define the degree of par-baking is not sufficient for bread loaves intended to be consumed over time, but the results indicate that reducing the degree of par-baking can be beneficial for certain quality aspects of the breads.

Lactiplantibacillus plantarum enables blood urate control in mice through degradation of nucleosides in gastrointestinal tract.

BACKGROUND: Lactobacillus species in gut microbiota shows great promise in alleviation of metabolic diseases. However, little is known about the molecular mechanism of how Lactobacillus interacts with metabolites in circulation. Here, using high nucleoside intake to induce hyperuricemia in mice, we investigated the improvement in systemic urate metabolism by oral administration of L. plantarum via different host pathways. RESULTS: Gene expression analysis demonstrated that L. plantarum inhibited the activity of xanthine oxidase and purine nucleoside phosphorylase in liver to suppress urate synthesis. The gut microbiota composition did not dramatically change by oral administration of L. plantarum over 14 days, indicated by no significant difference in α and ß diversities. However, multi-omic network analysis revealed that increase of L. plantarum and decrease of L. johnsonii contributed to a decrease in serum urate levels. Besides, genomic analysis and recombinant protein expression showed that three ribonucleoside hydrolases, RihA-C, in L. plantarum rapidly and cooperatively catalyzed the hydrolysis of nucleosides into nucleobases. Furthermore, the absorption of nucleobase by intestinal epithelial cells was less than that of nucleoside, which resulted in a reduction of urate generation, evidenced by the phenomenon that mice fed with nucleobase diet generated less serum urate than those fed with nucleoside diet over a period of 9-day gavage. CONCLUSION: Collectively, our work provides substantial evidence identifying the specific role of L. plantarum in improvement of urate circulation. We highlight the importance of the enzymes RihA-C existing in L. plantarum for the urate metabolism in hyperuricemia mice induced by a high-nucleoside diet. Although the direct connection between nucleobase transport and host urate levels has not been identified, the lack of nucleobase transporter in intestinal epithelial cells might be important to decrease its absorption and metabolization for urate production, leading to the decrease of serum urate in host. These findings provide important insights into urate metabolism regulation. Video Abstract.

Carnauba Wax and Beeswax as Structuring Agents for Water-in-Oleogel Emulsions without Added Emulsifiers.

This research aims to explore the potential of waxes as ingredients in the formulation of food-grade water-in-oleogel emulsions without added emulsifiers. The effects of the wax type, wax concentration and water concentration were tested on systems containing exclusively water, sunflower oil, and wax. Beeswax and carnauba wax were used in the formulation of water-in-oleogel emulsions with 20%, 30% and 40% w/w of water. For the continuous phase, three different levels of wax were used, namely 50%, 100%, and 150% of the critical gelling concentration. More specifically, carnauba wax emulsions were prepared at 2.5%, 5.0% and 7.5% of wax, while concentrations of 0.75%, 1.5% and 2.25% of wax were utilized for the beeswax experiments. Samples were assessed over time regarding stability, rheology and microstructure (polarized light microscopy, cryo-scanning electron microscopy and confocal scanning laser microscopy). Our findings suggest that, if present in sufficient concentration, carnauba wax and beeswax can stabilize emulsions in the absence of additional added emulsifiers. The resulting systems were inherently different based on the wax used, as crystal morphology and droplet configurations are determined by wax type. The yield strain was dictated by the nature of the wax, while the complex modulus was mostly influenced by the wax concentration. To test the scaling-up potential, systems were crystallized in a pilot-scale scraped surface heat exchanger, resulting in notably smaller crystal sizes, reduced rigidity and a storage stability of over one year. These findings represent a starting point for the formulation of scalable water-in-oleogel emulsions without added emulsifiers.

In vitro bioaccessibility and uptake of ß-carotene from encapsulated carotenoids from mango by-products in a coupled gastrointestinal digestion/Caco-2 cell model.

ß-carotene is a carotenoid with provitamin A activity and other health benefits, which needs to become bioavailable upon oral intake to exert its biological activity. A better understanding of its behaviour and stability in the gastrointestinal tract and means to increase its bioavailability are highly needed. Using an in vitro gastrointestinal digestion method coupled to an intestinal cell model, we explored the stability, gastrointestinal bioaccessibility and cellular uptake of ß-carotene from microparticles containing carotenoid extracts derived from mango by-products. Three types of microparticles were tested: one with the carotenoid extract as such, one with added inulin and one with added fructooligosaccharides. Overall, ß-carotene was relatively stable during the in vitro digestion, as total recoveries were above 68 %. Prebiotics in the encapsulating material, especially inulin, enhanced the bioaccessibility of ß-carotene almost 2-fold compared to microparticles without prebiotics. Likewise, ß-carotene bioaccessibility increased proportionally with bile salt concentrations during digestion. Yet, a bile salts level above 10 mM did not contribute markedly to ß-carotene bioaccessibility of prebiotic containing microparticles. Cellular uptake experiments with non-filtered gastrointestinal digests yielded higher absolute levels of ß-carotene taken up in the epithelial cells as compared to uptake assays with filtered digests. However, the proportional uptake of ß-carotene was higher for filtered digests (24 - 31 %) than for non-filtered digests (2 - 8 %). Matrix-dependent carotenoid uptake was only visible in the unfiltered medium, thereby pointing to possible other cellular transport mechanisms of non-micellarized carotenoids, besides the concentration effect. Regardless of a filtration step, inulin-amended microparticles consistently resulted in a higher ß-carotene uptake than regular microparticles or FOS-amended microparticles. In conclusion, encapsulation of carotenoid extracts from mango by-products displayed chemical stability and release of a bioaccessible ß-carotene fraction upon gastrointestinal digestion. This indicates the potential of the microparticles to be incorporated into functional foods with provitamin A activity.

Recent progress in oil-in-water-in-oil (O/W/O) double emulsions.

Oil-in-water-in-oil (O/W/O) double emulsions are recognized as an advanced design route for oil structuring that shows promising applications in the pharmaceutical, cosmetic, and food fields. This review summarizes the main research advances of O/W/O double emulsions over the past two decades. It mainly focuses on understanding the preparation strategies, stabilization mechanism, and potential applications of O/W/O double emulsions. Several emulsification strategies are discussed, including traditional two-step emulsification method, phase-inversion approach, membrane emulsification, and microfluidic emulsification. Further, the role of interfacial stabilizers and viscosity in the stability of O/W/O double emulsions will be discussed with a focus on synthetic emulsifiers, natural biopolymer sand solid particles for achieving this purpose. Additionally, analytical methods for evaluating the stability of O/W/O double emulsions, such as advanced microscopy, rheology, and labeling assay are reviewed taking into account potential limitations of these characterization techniques. Moreover, possible innovative food applications are highlighted, such as simulating fat substitutes to decrease the trans- or saturated fatty acid content and developing novel delivery and encapsulation systems. This review paves a solid way for the exploration of O/W/O double emulsions toward large-scale implementation within the food industry.

An extrusion-based 3D food printing approach for generating alginate-pectin particles.

In the present study, alginate-pectin (Al-P) hydrogel particles containing varied total gum concentrations (TGC) at a constant Al:P ratio of 80:20 were formed utilizing an innovative extrusion-based 3D food printing (3DFOODP) approach. The 3DFOODP conditions, namely, TGC (1.8, 2.0, and 2.2 wt%) and nozzle size (0.108, 0.159, and 0.210 mm) were investigated. The 3DFOODP approach was compared with the conventional bead formation method via a peristaltic pump. All Al-P printing inks exhibited a shear-thinning behavior. The increased apparent viscosity, loss and storage moduli were associated with the increase in the TGC. The size of the wet 3D-printed Al-P hydrogel particles ranged between 1.27 and 1.59 mm, which was smaller than that produced using the conventional method (1.44-1.79 mm). Freeze-dried Al-P particles showed a porous structure with reduced crystallinity. No chemical interaction was observed between alginate and pectin. This is the first report on generating Al-P-based beads using a 3DFOODP technique that can create delivery systems with high precision and flexibility.

Ultra-stable high internal phase emulsions stabilized by protein-anionic polysaccharide Maillard conjugates.

This paper reports the production of O/W high internal phase emulsions (HIPEs) using protein-anionic polysaccharide Maillard conjugates. First, Maillard conjugates were prepared from soy protein isolate (SPI) or sodium caseinate (SC) proteins and Alyssum homolocarpum seed gum (AHSG) or kappa-carrageenan (kC) polysaccharides. The conjugation process was confirmed and monitored by UV spectrophotometry, Fourier transform infrared, circular dichroism, fluorescence spectroscopies, and differential scanning calorimetry. Under the optimized reaction conditions, SC-AHSG conjugates exhibited the highest glycation degree and emulsifying properties. Next, HIPEs were made using the optimized conjugates, and their microstructure, droplet size, and physical stability were evaluated. The emulsion stabilized by SC-AHSG conjugate had the lowest mean droplet size (363.07 ± 34.56 nm), orderly-packed oil droplets with monomodal distribution, the highest zeta potential (-27.70 ± 0.70 mV), high storage stability (no creaming or oil-off) and was ultra-stable against environmental stresses. Results of this research are helpful for development of emulsion-based foods with novel functionality.

A combined approach for modifying pea protein isolate to greatly improve its solubility and emulsifying stability.

Pea protein-based delivery systems have drawn much attention in the food and pharmaceutical fields in recent years. However, its broad application faces great limitations because of the low solubility. Here, we present a novel and effective approach to overcome this difficulty and enhance the techno-functional characteristics, especially emulsifying stability, of the pea protein isolate (PPI). By combining pH-shifting with ultrasound and heating (PUH), we concluded that the solubility of PPI greatly increased from 29.5 % to 90.4 %, whereas its surface hydrophobicity increased from 1098 to 3706. This was accompanied by the changes of PPI structure, as shown by circular dichroism and scanning electron microscopy. In addition, the modified PPI was applied to stabilize sunflower oil-in-water emulsions. The droplet size of the emulsion with PUHP was reduced and its emulsion stability was significantly elevated. Taken together, we propose a novel combined approach to prepare modified PPI with high solubility and emulsion stability. We expect our method will have a wider application in modifying plant proteins and improving their industrial processing.

Physicochemical Characterization of Thirteen Quinoa (Chenopodium quinoa Willd.) Varieties Grown in North-West Europe-Part II.

Quinoa cultivation has gained increasing interest in Europe but more research on the characteristics of European varieties is required to help determine their end use applications. A comparative study was performed on 13 quinoa varieties cultivated under North-West European field conditions during three consecutive growing seasons (2017-2019). The seeds were milled to wholemeal flour (WMF) to evaluate the physicochemical properties. The WMFs of 2019 were characterized by the highest water absorption capacity (1.46-2.06 g/g), while the water absorption index (WAI) between 55 °C (2.04-3.80 g/g) and 85 °C (4.04-7.82 g/g) increased over the years. The WMFs of 2018 had the highest WAI at 95 °C (6.48-9.48 g/g). The pasting profiles were characterized by a high viscosity peak (1696-2560 mPa.s) and strong breakdown (-78-643 mPa.s) in 2017. The peak viscosity decreased in 2018 and 2019 (823-2492 mPa.s), while breakdown (-364-555 mPa.s) and setback (19-1037 mPa.s) increased. Jessie, Summer Red, Rouge Marie, Vikinga, and Zwarte WMFs were characterized by low WAIs and high shear resistance. Bastille WMF developed high viscosities and, along with Faro WMF, showed a high breakdown. The wide variation in physicochemical properties suggests that the potential food applications of WMFs depend on the variety and growing conditions.

Yield and Nutritional Characterization of Thirteen Quinoa (Chenopodium quinoa Willd.) Varieties Grown in North-West Europe-Part I.

The cultivation of quinoa has gained increasing interest in Europe. Different European varieties exist, but more research is required to understand the individual variety characteristics for end-use applications. The objective of this study is to evaluate the agronomic performance of 13 quinoa varieties under North-West European field conditions during three growing seasons (2017-2019). Furthermore, seeds were qualitatively characterized based on characteristics and composition. Yield differed among varieties and growing seasons (0.47-3.42 ton/ha), with lower yields obtained for late-maturing varieties. The saponin content varied from sweet to very bitter. The seeds contained high protein levels (12.1-18.8 g/100 g dry matter), whereas varieties had a similar essential amino acid profile. The main fatty acids were linoleic (53.0-59.8%), α-linolenic (4.7-8.2%), and oleic acid (15.5-22.7%), indicating a high degree of unsaturation. The clustering of varieties/years revealed subtle differences between growing seasons but also reflected the significant interaction effects of variety and year. Most varieties perform well under North-West European conditions, and their nutritional content is well within the values previously described for other cultivation areas. However, optimal yield and quality traits were not combined in one variety, illustrating the importance of breeding for adapted quinoa varieties.

Comparison of the Chemical and Technological Characteristics of Wholemeal Flours Obtained from Amaranth (Amaranthus sp.), Quinoa (Chenopodium quinoa) and Buckwheat (Fagopyrum sp.) Seeds.

A sound fundamental knowledge of the seed and flour characteristics of pseudocereals is crucial to be able to promote their industrial use. As a first step towards a more efficient and successful application, this study focuses on the seed characteristics, chemical composition and technological properties of commercially available pseudocereals (amaranth, quinoa, buckwheat). The levels of starch, fat, dietary fiber and minerals were comparable for amaranth and quinoa seeds but the protein content is higher in amaranth. Due to the high amount of starch, buckwheat seeds are characterised by the lowest amounts of fat, dietary fibre and minerals. Its protein content ranged between that of amaranth and quinoa. Buckwheat seeds were larger but easily reduced in size. The lipid fraction of the pseudocereals mostly contained unsaturated fatty acids, with the highest prevalence of linoleic and oleic acid. Palmitic acid is the most abundant unsaturated fatty acid. Moreover, high levels of P, K and Mg were found in these pseudocereals. The highest phenolic content was found in buckwheat. Amaranth WMF (wholemeal flour) had a high swelling power but low shear stability. The pasting profile strongly varied among the different quinoa WMFs. Buckwheat WMFs showed high shear stability and rate of retrogradation.

Fat crystallization of blends of palm oil and anhydrous milk fat: A comparison between static and dynamic-crystallization.

The application of dynamic-crystallization (a combination of shear with rapid cooling) often plays an important role in the production of industrial fat-based products such as shortenings/margarines but has been rarely reported. In this study, three blends of palm oil (PO) with anhydrous milk fat (AMF) (0, 25 and 50% AMF, w/w) were rapidly crystallized under static (using freezer) and dynamic conditions (using a benchtop scraped surface heat exchanger). Various techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized light microscopy (PLM), rheology and texture analysis were applied to investigate physicochemical properties of fat blends as well as their crystal morphology upon the long-term storage (4 weeks) at 5 °C and 15 °C. The results revealed that high cooling rate of dynamic-crystallization not only affected melting behavior of fat blends but also prevented the polymorphic transformation from ß' to ß crystals. Besides, the application of shear during fat crystallization helped to improve significantly the gel strength of produced shortenings. Although post-crystallization of low melting triacylglycerols (TAGs) occurred for all produced shortenings during storage at 5 °C which was accompanying with a firmness increase, it was more considerable for samples owning higher AMF content. Moreover, this phenomenon promoted the sintering as well as Ostwald ripening between fat crystals of dynamic-crystallized fat blends resulting in the formation of unwanted large aggregates (or granular crystals) with the size ranging from 100 to 500 µm.

Comparison of the antifungal effect of undissociated lactic and acetic acid in sourdough bread and in chemically acidified wheat bread.

Sourdough is a very interesting natural preservation system to prolong mould free shelf-life of bread. Numerous studies have reported that the antifungal activity of sourdough is mainly correlated with the presence of lactic (LA) and acetic acid (AA), but very few information is available on the effect of undissociated acid concentrations in the aqueous phase of bread (CHA; mmole/L). This study was conducted to provide additional information about the mode of action of the acids in sourdough bread, enabling a better shelf-life prediction. This study was divided into two parts. In part 1, three industrial biological sourdoughs were characterized (dough yield, pH, aw, fermentation quotient, microbiota). During 7 weeks, a shelf-life test with natural flora was conducted with daily checks of visible mould growth (21 °C). In part 2, the effect of the acids present in the antifungal active sourdough breads was validated in chemically acidified wheat breads. Complete growth inhibition was observed in full-baked sourdough bread (30 g/100 g dough) containing Lactobacillus sanfranciscensis and Saccharomyces cerevisiae as dominant sourdough micro-organisms, whereas in control bread the shelf-life was limited to 4.4-9.2 days. These full-baked sourdough breads contained 36 mmole undissociated LA/L and 220 mmole undissociated AA/L. The data were used to make General Linear Regression models for shelf-life prediction and resulted in a fit of R2 = 0.79 when expressing the shelf-life in function of CHA,LA and CHA,AA. In acidified breads, the role of lactic acid was not significant and only impacted shelf-life indirectly through acidification. No difference between antifungal activity of sourdough breads and chemically acidified bread with comparable CHA,AA concentrations was observed. Shelf-life increased when 150-200 mmole undissociated AA/L aqueous phase in bread was present. To conclude, this study showed the importance of the undissociated acid fraction of acetic acid in relation to bread shelf-life, together with bread pH and moisture content.

Modelling and validation of the antifungal activity of DL-3-phenyllactic acid and acetic acid on bread spoilage moulds.

Most interesting antifungal compounds from sourdough fermentation are acetic acid (AA) and DL-3-phenyllactic acid (PLA). Although the role of pH on the activity of organic acids has been established long time ago, no information is available on the importance of undissociated acid (HA) expressed on the aqueous phase of bread (CHA, mmole/L). Mostly, concentrations (mmole/kg dough or bread, CTOT) and pH are given side by side. The aim of this study was to show the importance of CHA for adequate comparison of in-vitro growth data with bread shelf-life. Growth of Penicillium paneum and Aspergillus niger was recorded using a micro-dilution assay with optical density measurements. Parameters such as aw (0.94-0.98), pH (4.6-6.0), temperature (10-30 °C), time (0-8 days) and CTOT (0-300 mM) were varied. Growth/no-growth models were developed and shelf-life tests of par-baked breads of 45 days at 20 °C were conducted. The modelled inhibitory concentrations of undissociated acid were comparable with the shelf-life test of bread: (PLA) 50 versus 39-84 mmol/L; (AA) 110 versus 110-169 mmol/L. This study showed the applicability of G/NG models for bread shelf-life prediction and highlighted the importance of CHA. Moreover, it was found that naturally present PLA in sourdough bread is insufficient to increase bread shelf-life.

Growth/no-growth models of in-vitro growth of Penicillium paneum as a function of thyme essential oil, pH, aw, temperature.

The aims of this study were (i) screening of antifungal activity of thyme essential oil on Penicillium paneum; (ii) development of growth/no-growth models (G/NG); and (iii) validation of the G/NG models by performing bread baking trials. The screening method was based on the measurement of fungal growth in a semi-solid medium through optical density. The combined influence of aw (0.88-0.97), pH (4.8-7.0), temperature (22 and 30 °C), time (0-144 h) and varying concentrations of thyme oil (0-2 µL/mL YES) were assessed. Growth of P. paneum at aw 0.88 was significantly reduced compared to aw 0.93-0.97. A slight pH effect was observed at aw 0.93; growth was delayed at pH 6 compared to pH 4.8. The lowest concentration of thyme oil preventing growth during 144 h of incubation was 1 µL/mL medium. According to the results of the shelf-life test of par-baked bread, fungal growth was inhibited for more than 45 days using 0.3 mL thyme oil/100 g dough. To conclude, this study recognized the potential of using G/NG models to develop better product formulations and to facilitate product innovation.

Effect of sourdough addition and storage time on in vitro starch digestibility and estimated glycemic index of tef bread.

The effect of sourdough amount and storage time on starch digestibility and estimated glycemic index (eGI) of tef bread was investigated. The rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) of 0-30% sourdough fresh tef breads ranged from 49 to 58, 16 to 29 and 20 to 26 g/100 g starch, respectively. Storage of tef breads up to 5 days decreased the RDS by more than 2-fold while SDS and RS increased by 2 and 3 fold, respectively. The eGI for fresh and stored breads ranged from 39 to 89. Addition of sourdough increased the eGI of fresh breads while no uniform pattern was seen in the stored breads. As the storage time increased, all the breads showed a decrease in eGI. In vivo study is necessary to further investigate the effect of sourdough on GI of tef bread.