Publications Search Results

Now showing 1 - 10 of 57
  • Publication
    Enzymatic hydrolysis and fermentation of pea protein isolate and its effects on antigenic proteins, functional properties, and sensory profile
    ( 2022)
    Arteaga, Verónica García
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    Demand, Victoria
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    Schweiggert-Weisz, Ute
    Combinations of enzymatic hydrolysis using different proteolytic enzymes (papain, Esperase®, trypsin) and lactic fermentation with Lactobacillus plantarum were used to alter potential pea allergens, the functional properties and sensory profile of pea protein isolate (PPI). The order in which the treatments were performed had a major impact on the changes in the properties of the pea protein isolate; the highest changes were seen with the combination of fermentation followed by enzymatic hydrolysis. SDS-PAGE, gel filtration, and ELISA results showed changes in the protein molecular weight and a reduced immunogenicity of treated samples. Treated samples showed significantly increased protein solubility at pH 4.5 (31.19-66.55%) and at pH 7.0 (47.37-74.95%), compared to the untreated PPI (6.98% and 40.26%, respectively). The foaming capacity was significantly increased (1190-2575%) compared to the untreated PPI (840%). The treated PPI showed reduced pea characteristic off-flavors, where only the treatment with Esperase® significantly increased the bitterness. The results from this study suggest that the combination of enzymatic hydrolysis and lactic fermentation is a promising method to be used in the food industry to produce pea protein ingredients with higher functionality and a highly neutral taste. A reduced detection signal of polyclonal rabbit anti-pea-antibodies against the processed protein preparations in ELISA furthermore might indicate a decreased immunological reaction after consumption.
  • Publication
    Nanocomposite coatings based on polyvinyl alcohol and montmorillonite for high-barrier food packaging
    ( 2022)
    Schiessl, Stefan
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    Kucukpinar, Esra
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    Cros, Stéphane
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    Miesbauer, Oliver
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    Materials with high barrier properties against oxygen are required for the packaging of many sensitive foods. Since commodity polymers lack these properties, additional barrier materials are used in plastic-based barrier packaging. These are usually more expensive than commodity polymers and, in higher fractions, also make recycling more difficult. Current developments, therefore, aim at barrier layers that are as thin as possible but retain the barrier properties. One approach is to incorporate nanoparticles into these layers. In this study, the barrier properties of nanocomposite coatings, consisting of unmodified polyvinyl alcohol (PVA), and dispersed stick-shaped halloysite (Hal) or platelet-shaped montmorillonite (MMT) silicate nanoparticles, were investigated. The PVA was dissolved in aqueous nanoparticle dispersions, which were prepared by mechanical shearing, to produce the so-called ""nanolacquer."" Nanolacquers with nanoparticle concentrations of 7, 30, and 47 vol% with respect to PVA were applied in a single process step with k-bar on a polypropylene substrate film. The integration of 30 vol% platelet-shaped MMT enhances the barrier performance in comparison to pure PVA by a factor of 12 and 17 for oxygen and helium, respectively. Scanning electron microscopy (SEM) shows a homogeneous distribution and a parallel alignment of the nanoparticles within the coated layer. An increase in the crystallinity of PVA was observed due to the nanoparticle integration as demonstrated by x-ray diffraction (XRD) measurements. The investigation by Fourier transform infrared (FTIR) spectroscopy and the activation energy of the permeation coefficient indicate an interaction between the nanoparticles and the PVA. The theoretically calculated values for barrier enhancement accord well with the experimental values, which emphasizes that the gas barrier improvement for oxygen and helium is mainly dominated by the tortuous path effect.
  • Publication
    Effects of extrusion processing on the physiochemical and functional properties of lupin kernel fibre
    Lupin kernel fibre is an underutilised by-product of lupin protein isolation rich in insoluble dietary fibre. By means of extrusion technology, insoluble fibres can be converted in soluble fibres, which are considered the most effective dietary fibre fraction for human health. Lupin kernel fibre was processed at various barrel temperatures, feed moistures and screw speeds. The physiochemical (dietary fibre composition, colour, water and oil binding capacities) and functional (viscosity and bile acid interactions) properties of the lupin fibres after extrusion were evaluated compared to the non-extruded fibre. Due to extrusion processing, the soluble fraction of dietary fibre was increased from 1.9 g/100 g DM to up to 37.7 g/100 g DM, water binding capacity was increased by up to 95%, while oil binding capacity significantly decreased. Moisture content, followed by barrel temperature were identified as the most relevant extrusion parameters to influence physiochemical properties. To estimate effects of extrusion on fibre functionality, extrudates were digested under simulated gastro-intestinal conditions. Viscosity of in vitro digesta was increased for most extruded fibres. Accordingly, diffusion of bile acids was decreased, which may improve cholesterol lowering properties. Molecular interactions of lupin compounds with bile acids were not affected by the extrusion treatment. The results indicate that extrusion caused solubilisation of hydrophilic pectin-like polymers, which exhibit high hydration properties and thus increase the viscosity at physiological conditions. These findings suggest that extrusion could be a practical technology to enhance health benefits of lupin kernel fibre.
  • Publication
    Effect of Acylation of Rapeseed Proteins with Lauroyl and Oleoyl Chloride on Solubility and Film‑Forming Properties
    ( 2021) ;
    Hintermayr, Cornelia
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    Schmid, Markus
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    Rapeseed proteins show good film-forming properties, giving them a promising potential as bio-based ingredients for the technical industry, e. g. for films and coatings. However, their hydrophilicity often poses problems in regard to water-stability of coatings. Protein modification using fatty acids is known to reduce hydrophilicity, however, it has not been tested to improve film-forming properties of rapeseed proteins before. In the present study, a rapeseed protein concentrate (RPC) was acylated at low and high modification degree using lauroyl chloride and oleyol chloride. The protein solubility was determined and the modified RPCs were used for the preparation of cast-films to measure the changes of mechanical properties (tensile strength, elongation at break), surface energy, oxygen permeability and light transmission. The protein solubility in water was lowered from 100% for the non-modified RPC to < 15% for highly modified RPCs at pH 7. The tensile strength of films increased by factors of 3.5 and 4 for highly modified samples, respectively. Surface energy and oxygen permeability revealed an increase of hydrophobicity that correlated with the modification degree. The light transmission was reduced by modification. The results confirm the increased hydrophobicity of acylated RPCs and demonstrate the potential of modified rapeseed proteins as an ingredient for technical products, such as packaging layers, coatings and adhesives.
  • Publication
    How Does the Phenol Structure Influence the Results of the Folin-Ciocalteu Assay?
    Plants produce a diverse array of secondary metabolites that are generally nonessential but facilitate ecological interactions. Fruits, vegetables, seeds and nuts can accumulate bioactive secondary metabolites with health-promoting properties, including the potent antioxidant activities of phenolic compounds. Several in vitro assays have been developed to measure the polyphenol content and antioxidant activity of plant extracts, e.g., the simple and highly popular Folin-Ciocalteu (FC) assay. However, the literature contains a number of different descriptions of the assay and it is unclear whether the assay measures the polyphenol content or reducing capacity of the sample. To determine the influence of phenolic structures on the outcome of the FC assay, we tested phenols representing different subgroups (phenolic acids, flavonols, flavanols, dihydrochalcones and flavanones). We observed different results for each reference substance and subgroup. Accordingly, we concluded that the FC assay does not measure the polyphenol content of a sample but determines its reducing capacity instead. Assigning the substances to five structural classes showed that the FC results depend on the number of fulfilled Bors criteria. If a molecule fulfills none of the Bors criteria, the FC results depend on the number of OH groups. We did not find a correlation with other single electron transfer assays (e.g., ABTS and DPPH assays). Furthermore, the FC assay was compatible with all five subgroups and should be preferred over the DPPH assay, which is specific for extracts rich in dihydrochalcones or flavanones.
  • Publication
    Electrophoretic characterization, amino acid composition and solubility properties of Macauba (Acrocomia aculeata L.) kernel globulins
    ( 2021)
    Toledo e Silva, Sérgio Henrique
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    Bader-Mittermaier, Stephanie
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    Bataglia Silva, Lidiane
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    Macauba palm (Acrocomia aculeata L.) fruits are emerging sources to produce high-quality oils from pulp and kernels. Yet, the protein-rich press cake from the kernels remains underutilized, mainly due to lacking knowledge of protein composition and properties. Therefore, our aim was to characterize the main protein fractions of Macauba kernels. The globulins were the major protein fraction (58.5% of storage proteins), which were further separated into 11 S and 7 S globulins. The subunits of both globulins presented heterogeneity in isoelectric point (5.3-8.3), revealing genetic polymorphism. The 7 S globulins were soluble at low ionic strength (0.1 mol/L), whereas the 11 S globulins required higher salt concentration (0.50-0.75 mol/L) for solubilization, independent on selected salt types. Both globulins were rich in essential amino acids, especially methionine and cysteine, making Macauba kernel proteins a valuable source to complement diets based on pulses and oilseeds.
  • Publication
    Fermentation of Lupin Protein Hydrolysates - Effects on their Functional Properties, Sensory Profile and the Allergenic Potential of the Major Lupin Allergen Lup an 1
    ( 2021)
    Schlegel, Katharina
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    Schweiggert-Weisz, Ute
    Lupin protein isolate was treated using the combination of enzymatic hydrolysis (Papain, Alcalase 2.4 L and Pepsin) and lactic acid fermentation (Lactobacillus sakei ssp. carnosus, Lactobacillus amylolyticus and Lactobacillus helveticus) to investigate the effect on functional properties, sensory profile and protein integrity. The results showed increased foaming activity (2466-3481%) and solubility at pH 4.0 (19.7-36.7%) of all fermented hydrolysates compared to the untreated lupin protein isolate with 1613% of foaming activity and a solubility of 7.3 (pH 4.0). Results of the SDS-PAGE and Bead-Assay showed that the combination of enzymatic hydrolysis and fermentation of LPI was effective in reducing L. angustifolius major allergen Lup an 1 to a residual level of <0.5%. The combination of enzymatic hydrolysis and fermentation enables the production of food ingredients with good functional properties in terms of protein solubility and foam formation, with a balanced aroma and taste profile.
  • Publication
    Effect of Physicochemical Properties of Carboxymethyl Cellulose on Diffusion of Glucose
    ( 2021) ;
    Bader-Mittermaier, Stephanie
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    Schweiggert-Weisz, Ute
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    Hauner, Hans
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    Soluble dietary fibers (SDF) are known to reduce the post-prandial plasma glucose levels. However, the detailed mechanisms of this reduced glucose release in the human gut still remain unclear. The aim of our study was to systematically investigate the effect of different types of SDF on glucose release in an in vitro model as a prerequisite for the selection of fibers suitable for application in humans. Three types of carboxymethyl cellulose (CMC) were used to investigate the correlations between fiber concentration, molecular weight (MW), and viscosity on diffusion of glucose using a side-by-side system. CMC solutions below the coil overlap (c*) influenced the glucose diffusivity only marginally, whereas at concentrations above c* the diffusion of glucose was significantly decreased. Solutions of lower MW exhibited a lower viscosity with lower glucose diffusion compared to solutions with higher MW CMC, attributed to the higher density of the solutions. All CMC solutions showed a systematic positive deviation from Stokes-Einstein behavior indicating a greater rise in viscosity than reduction in diffusion. Therefore, our results pave the way for a new approach for assessing glucose diffusion in solutions comprising dietary fibers and may contribute to further elucidating the mechanisms of post-prandial plasma glucose level reduction.
  • Publication
    Common Trends and Differences in Antioxidant Activity Analysis of Phenolic Substances Using Single Electron Transfer Based Assays
    ( 2021) ; ; ;
    Schweiggert-Weisz, Ute
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    Miesbauer, Oliver
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    Numerous assays were developed to measure the antioxidant activity, but each has limitations and the results obtained by different methods are not always comparable. Popular examples are the DPPH and ABTS assay. Our aim was to study similarities and differences of these two assay regarding the measured antioxidant potentials of 24 phenolic compounds using the same measurement and evaluation methods. This should allow conclusions to be drawn as to whether one of the assays is more suitable for measuring specific subgroups like phenolic acids, flavonols, flavanones, dihydrochalcones or flavanols. The assays showed common trends for the mean values of most of the subgroups. Some dihydrochalcones and flavanones did not react with the DPPH radical in contrast to the ABTS radical, leading to significant differences. Therefore, to determine the antioxidant potential of dihydrochalcone or flavanone-rich extracts, the ABTS assay should be preferred. We found that the results of the flavonoids in the DPPH assay were dependent on the Bors criteria, whereas the structure-activity relationship in the ABTS assay was not clear. For the phenolic acids, the results in the ABTS assay were only high for pyrogallol structures, while the DPPH assay was mainly determined by the number of OH groups.
  • Publication
    Sensory profile, functional properties and molecular weight distribution of fermented pea protein isolate
    ( 2021)
    García Arteaga, Verónica
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    Leffler, Sophia
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    Schweiggert-Weisz, Ute
    Pea protein isolate (PPI, from Pisum sativum L.) was fermented with six different lactic acid bacteria strains for 24 ​h and 48 ​h. The fermented samples were analyzed regarding their retronasal aroma and taste, their protein solubility, emulsifying and foaming capacity. Changes in the molecular weight distribution were analyzed to monitor potential effects of fermentation on the main allergenic protein fractions of PPI. After 24-h fermentation, PPI's characteristic aroma attributes and bitter taste decreased for all fermented PPI. However, after 48-h fermentation, cheesy aroma, and acid and salty tastes were increased. The PPI fermented with L. plantarum showed the most neutral taste and the panel's highest preference; instead, fermentation with L. fermentum led to a fecal aroma and was the least preferred. The protein solubility and emulsifying capacity decreased after PPI fermentation, while foaming capacity remained constant in comparison to the untreated PPI. The electrophoretic results showed a reduction in the intensity of the allergenic protein fractions; however, these changes might be attributed to the reduced protein solubility rather than to a high proteolytic effect of the strains. Fermentation of PPI for 24 ​h and 48 ​h might not be a suitable method for the production of highly functional pea proteins. Further modification methods have to be investigated in the future.