Browsing by Subject "Characterization"

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Characterization of the rehydration behavior of food powders
(2019) Wangler, Julia; Kohlus, Reinhard
The rehydration behavior of food powders is of high importance in terms of powder processing and product quality. Rehydration of powders mainly depends on the physical powder characteristics particle size, porosity and wettability, the latter being expressed by the contact angle between solid and rehydrating liquid. With focus on food powders, it could be shown that the rehydration behavior is strongly influenced by dynamic changes of these physical characteristics. This includes the initiation of dissolution and swelling directly after powder-liquid contact. Especially in case of biopolymers, which were investigated in detail by the example of xanthan gum, guar gum and alginate, these processes are important to describe their rehydration behavior. Due to the special characteristics of these biopolymers dissolution and swelling result in an increase of viscosity as well as in a decrease of bulk porosity. The kinetics and interactions of these processes significantly affect the individual steps of rehydration and have to be considered in describing the process of food powder rehydration. For inert powder-liquid systems capillary liquid uptake into a powder bulk can be described by the Washburn equation which equates the capillary pressure and the hydrodynamic flow resistance. This approach was used as basic equation to describe capillary liquid uptake of food powders. The validity of the original approach is restricted to the case of constant powder and liquid properties. With regard to food powders, changes within the powder-liquid system were considered by a stepwise adaption of the variables of the Washburn equation. Thus, the first part of this thesis focused on establishing and defining methods to characterize the dynamics of the physical properties particle size, bulk porosity, viscosity and contact angle. This enabled a more detailed characterization of the interactions between food powder and liquid during rehydration. Wettability of food powders in contact with dist. water was assessed by contact angle measurements. Contact angles were 52° for alginate, 58.1° for xanthan gum and 70° for guar gum which confirmed their hydrophilic character. To describe the change of the bulk porosity a rheological measurement set-up was constructed to quantify the swelling behavior. Influence of viscosity on rehydration was determined by measuring the concentration dependent viscosity increase and the rate of viscosity increase over time. The change of viscosity as a consequence of dissolution allowed conclusions about the dissolution rate of biopolymers in highly concentrated situations. These results indicated that rehydration of guar gum is mainly influenced by viscosity effects whereas swelling has the highest impact on the rehydration behavior of xanthan gum and alginate. Further methods such as Nuclear Magnetic Resonance analysis enabled a more detailed characterization concerning the dynamics of powder-liquid interactions and the strength of water binding within these biopolymer gels. The strength of water binding was found to correlate with the stability of highly concentrated biopolymer aggregates. The aggregate stability was determined by rheological analyses and is of importance, particularly with regard to powder dispersability. To predict food powder rehydration, a model was established using a VoF approach. To simulate capillary liquid rise based on physical characteristics, dynamic changes were resolved both spatial and temporally. To describe particle and liquid properties more precisely, a model system consisting of biopolymer coated glass beads was developed by fluid bed technology. By the variation of the coating layer thickness and the coating material, dynamic changes within the system could be controlled which enabled a more differentiated description. A parameter variation study was conducted to simulate the influence and interaction of dynamic processes on capillary liquid uptake into such powder systems. Capillary liquid uptake into the coated glass beads was investigated experimentally. It could be shown that even with coating layers of 0.5 µm dynamic effects are sufficiently strong to cause a stop of capillary liquid uptake. It has been shown that viscosity development dominates guar gum rehydration whereas swelling is the prevalent mechanism in xanthan gum and alginate rehydration. Simulation of capillary liquid rise demonstrated that the influence of the coating layer thickness is not significant. This result could be explained by the slow dissolution rates of the biopolymer samples. Calculations indicated that even a coating layer of 0.5 µm could only be dissolved partially after a dissolution time of 250 s. This explains the little impact of coating layer thickness on viscosity development and thus on capillary liquid uptake. Further explanations focus on biopolymer swelling. Simulation showed that coating layers of 0.5 µm are sufficient to cause swelling-induced pore-blocking conditions.
Isolation, characterization and potential agro-pharmaceutical applications of phorbol esters from Jatropha curcas oil
(2012) Devappa, Rakshit K.; Becker, Klaus
Biodiesel is generally prepared from renewable biological sources such as vegetable oils by transesterification. Jatropha curcas seed oil is a promising feedstock for biodiesel production. During biodiesel production from Jatropha oil, many co-products such as glycerol, fatty acid dis-tillate and seed cake, among others, are obtained. The efficient use of these co-products would enhance the economic viability of the Jatropha based biofuel industry. However, the possible presence of phorbol esters (PEs) in these co-products restricts their efficient utilization. During biodiesel production, Jatropha oil is subjected to many treatments (stripping, degumming and esterification) wherein PEs present in the oil undergo partial or complete destruction depending on the treatment conditions. One of aims of this study was to develop and integrate methodolo-gies for using the PEs as a value added product instead of simply allowing them to be destroyed during biodiesel production. Potential uses of the phorbol ester enriched fraction (PEEF), ob-tained from Jatropha oil in agro-pharmaceutical applications were also investigated. The reason for choosing this group of compounds (PEs) was that they are highly bioactive both in vitro and in vivo, but they are currently considered to be merely toxic, unwanted biomaterial in the Jatro-pha biodiesel production chain. The recent increase in the cultivation of Jatropha cultivation means that there are potentially huge quantities of PEs that could be used for many purposes. This study revealed that a large proportion (85.7%) of PEs was localized in the endosperm portion of the Jatropha seed. Interestingly, the kernel coat contained PEs in high concentration. The endosperm portion of the kernel also contained antinutritional factors such as phytate (96.5%) and trypsin inhibitor (95.3%). The presence of high levels of antinutritional/toxic com-ponents in the kernel was presumed to be one of the factors that protect Jatropha seeds against predatory organisms during post harvest storage. Based on the presence or absence of PEs, a qualitative method was developed to differentiate between toxic/nontoxic Jatropha genotypes. In this method the methanol extract of seeds is passed through a solid phase extraction (SPE) column and the absorption (280 nm) of the result-ing eluate is measured. After screening Jatropha seeds collected from different parts of the world for toxic and non-toxic genotypes using the pre-established HPLC method for PEs, a cut off value of the absorbance was set up to differentiate toxic and nontoxic genotypes. Raw kernels whose SPE eluates had an absorbance ≥0.056 were considered as toxic and ≤0.032 as nontoxic. Corresponding absorbances for the SPE eluates of defatted kernel meal were ≥0.059 (toxic) and ≤0.043 (nontoxic). However, confirmation of the presence of PEs especially in Jatropha products for food applications should be carried out using the pre-established and validated HPLC method. The developed qualitative method could find its applications for screening the toxicity of products and co-products obtained from the Jatropha biodiesel industry. Conditions were optimized for the extraction of PEs as a phorbol ester enriched fraction (PEEF) from Jatropha oil using methanol as a solvent and a magnetic stirrer/Ultra-turrax as ex-traction tools. The extent of PE reduction in Jatropha oil was >99.4% using methanol as the sol-vent. The PEEF obtained (48.4 mg PEs/g) was 14 fold higher in PEs than in the original oil and this fraction was highly bioactive as determined by the most sensitive snail bioassay (LC100, 1 ppm) (see below). As the removal of PEs from oil took 60 min, which might be considered a long time in an industrial process, further conditions were optimized to extract maximum PEs in the shortest possible time with minimum solvent. The tools used for PE extraction (Ultra-turrax and magnetic stirrer) were effective with a treatment time of 2 and 5 min, resulting in 80 and 78% extraction of PEs, respectively. The biodiesel prepared from both the residual oils met European (EN 14214:2008) and American biodiesel standard (ASTM D6751-09) specifications. It was evident from the study that PEs could be easily extracted by either of the two methods with a high yield and the residual oil could be processed to produce high quality biodiesel. Also the residual oil with a lower PE content is expected neither to harm the environment nor the workers who had to handle it. The extracted PEEF was evaluated for its agricultural potential as a bio control agent. The PEEF had a high biological activity in aquatic bioassays using snails (Physa fontinalis), brine shrimp (Artemeia salina) and daphnia (Daphnia magna), when compared with microorganisms. The EC50 (48 h) of the PEEF was 0.33, 26.48 and 0.95 ppm PEs for snail, brine shrimp and daphnia respectively. High MIC (minimum inhibitory concentration) values (≥215 ppm) and EC50 values (≥58 ppm) were obtained for both the bacterial and fungal species. Among the bio-assays tested, the snail bioassay was the most sensitive, producing LC100 at 1 μg of PEs/ml. The snail bioassay could be used to monitor the presence of PEs in various Jatropha derived products, contaminated soil and other matrices in the ecosystem that might be involved in the production or use of Jatropha and its products. The study also demonstrated that the PEs exhibit molus-cicidal, antifungal and antibacterial activities. The shelf life of the PEEF was investigated. The PEEF was more susceptible to degradation when stored at room temperature (50% degradation after 132 days) than when stored at 4 °C or -80 °C (8% and 4% degradation respectively). Similarly, the PEEF lost biological activity (the snail bioassay) more rapidly at room temperature becoming ineffective after 260 days; while at 4 °C and -80 °C, only 27.5% and 32.5% activity was lost after 870 days. The degradation of PEs was due to auto-oxidation. Changes in fatty acid composition, increase in peroxide value and decrease in free radical scavenging activity of the PEEF reflected the auto-oxidation. Inclusion of antioxidants as additives (butylated hydroxyanisole (BHA), Baynox and α-tocopherol) pro-tected the PEs against degradation. The study demonstrated that the PEEF was susceptible to oxidation and addition of antioxidant stabilised the PEs during storage. In soil, PEs present in both the PEEF (2.6 mg/g soil mixture) (silica was used to adsorb PEs) and Jatropha seed cake (0.37 mg/g soil mixture) were completely degraded as the temperature and moisture content of the soil increased. PEs from silica-bound PEEF were completely de-graded after 19, 12, 12 days (at 13% moisture) and after 17, 9, 9 days (at 23% moisture) at room temperature (22 −23°C), 32 °C and 42 °C respectively. Similarly, at these temperatures, PEs from seed cake were degraded after 21, 17 and 17 days (at 13% moisture) and after 23, 17, and 15 days (at 23% moisture). The toxicity of PE-amended soil extracts when tested using the snail bioassay decreased with the decrease in PE concentration. The study demonstrated that PEs pre-sent in the PEEF or Jatropha seed cake are completely biodegradable in soil and the degraded products are innocuous. In preliminary studies, the PEEF exhibited potent insecticidal activity against Spodoptera frugiperda, which is a common pest in corn fields damaging maize crop across the tropi-cal/subtropical countries such as Mexico and Brazil. The PEEF produced contact toxicity with an LC50 of 0.83 mg/ml (w/v). The PEEF at higher concentration (0.25 mg/ml, w/v) also reduced food consumption, relative growth rate and food conversion efficiency (FCE) by 33%, 42% and 38% respectively. The study demonstrated that the PEEF has a potential to be used as a bio-control agent. Further in-depth field experiments on the effects of the PEEF on S. frugiperda will pave the way for its use under field conditions. The pharmaceutical potential of Jatropha PEs was also investigated. The PEs from Jatropha oil were purified. At least six purified PEs (designated as factors C1 to C6) were present in Jatropha oil. The identities of the purified PEs (factors C1 and C2) were confirmed by NMR. Whereas, factor C3 and factors (C4 + C5) were both obtained as mixtures. However, comparison of peak areas for phorbol 12-myristate 13-acetate (PMA) and Jatropha factor C1 in the HPLC method showed a difference in sensitivity of absorption at 280 nm of 41.3 fold. All the individual purified Jatropha PEs (factors C1, C2, C3mixture and (C4+C5)) and PEs-rich extract (factors C1 to (C4 + C5)) were biologically active when tested in the snail and brine shrimp bioassays. In ad-dition, all the Jatropha PEs produced platelet aggregation in vitro with an effective order of (based on ED50 (μM)): Jatropha factor C2 < factor C3mixture < factor C1 < factor (C4+C5). The PEs-rich extract (contains factor C1 to C6) was toxic to mice upon intra gastric administration, with an LD50 of 27.34 mg/kg body mass as PMA equivalent or 0.66 mg/kg body mass as factor C1 equivalent. The prominent histopathological symptoms were observed in lung and kidney. The Jatropha purified PEs-rich extract, purified PEs (factor C1, factor C2, factor C3mixture and factors (C4+C5)) and toxic Jatropha oil produced severe cellular alterations/disintegration of the epithelium and also increased the inflammatory response (interleukin-1α and prostaglandin E2 release) when applied topically to reconstituted human epithelium (RHE) and human corneal epithelium (HCE). In RHE, the nontoxic oil (equivalent to the volume used for toxic oil) pro-duced a lower cellular and inflammatory response than the toxic oil and the response increased with an increase in concentration of the PEs. In HCE, nontoxic oil (equivalent to the volume used for toxic oil) produced marked cellular alterations. The study demonstrated that the pres-ence of PEs in Jatropha oil increased the toxicity, both towards RHE and HCE. In addition, all the purified Jatropha PEs gave positive responses in the tumour promotion assay and negative responses in the tumour initiation assay in vitro (the assay was based on foci formation in Bhas 42 cells). In the tumour promotion assay, the order of transformed foci/well formation was: PEs-rich extract > factor (C4+C5) > factor C3mixture > factor C1 > factor C2. The tumour promotion ac-tivity was mediated by the hyper activation of protein kinase C (PKC). The aforementioned studies demonstrated that Jatropha PEs are toxic when administered orally or when applied topically to the skin or eye tissues. The data obtained should help in establishing safety measures for people working with Jatropha PEs. The potential of Jatropha PEs as a feedstock intermediate for the synthesis of Prostratin, a promising adjuvant in anti HIV therapy, was evaluated. The studies demonstrated that the Jatro-pha PEs could be synthesized sequentially by converting them first to crotophorbolone and then to prostratin. As analyzed by Nano-LC-ESI-MS/MSR, the prostratin synthesized from Jatropha PEs had similar mass and peak retention time to the reference prostratin (Sigma, St. Louis), The study showed that prostratin could be synthesized from Jatropha PEs. However, further optimi-zation studies are required to ascertain the synthesis reactions and yield of prostratin synthesized from Jatropha PEs. Some of the preliminary requirements for any successful bio-control agent are that it should have a high bioactivity on the target organism, a long shelf-life and a high biodegradability in soil. In addition, the bioactive phytochemical should be available in large quantities, it should be easily extractable and continuously available. The PEEF potentially satisfies these aforesaid re-quirements. The abundance and novelty of PEs present in Jatropha species could form a new ?stock? for the agro-pharmaceutical industries. Considering the projected oil yield of 26 million tons/annum by 2015 (GEXSI, 2008), huge amount of raw materials will be available for both biodiesel and pharmaceutical industries. PEs in the form of the PEEF could be used either as in-sect controlling agents in agricultural applications or as a ?stock? biomaterial for synthesizing prostratin in pharmaceutical applications.
Neu auftretende bakterielle Blattfleckenerreger an Radies und Entwicklung eines Resistenztests als Grundlage für die Züchtung resistenter Sorten
(2014) Scholze, Inka S.; Vögele, Ralf
Radish is one of the most important vegetable crops in Rhineland Palatinate. During the last decades, an increase in bacterial leaf spots on radish has been observed. Although the bulb is unaffected, leaf spot symptoms lead to a decline in sales and profits as German consumers prefer marketable red radish bunches including the freshness-indicating foliage. So far, preventive methods for the control of bacterial pathogens on radish were limited to irrigation strategies (for example drip irrigation) or field hygiene. These methods are, however, often difficult to implement and their effect predominantly insufficient. Resistant or tolerant breeds would provide a solution, however, breeding companies have been lacking the necessary information regarding the causative agents and their biology and epidemiology needed for the development of such breeds. Previous examinations of infested plants and seed lots suggest different pseudomonads and Xanthomonas campestris as possible agents. The main objective of this study was therefore to identify the relevant pathogens causing leaf-spot symptoms on radish. Furthermore, another objective was to clarify the infection and growth requirements of bacterial pathogens on hosts for the development of a screening method for resistance to leaf spot pathogens on radish. On account of increasing compensation claims from breeding companies by farmers, the role of seed transmissibility was also to be determined. during a three year observation, bacterial pathogens from plants and seed lots were isolated and characterized. The characterization of unknown bacterial strains was performed by a combination of physiological and molecular methods. Molecular characterization methods such as 16s rDNA sequence analysis and MLST (multilocus sequence typing) were needed to complete the designation of P. syringae pathovars. In addition, virulence assays clarified the importance of single pathovars. Hence bacterial leaf spot pathogens could be determined as P. syringae pv. maculicola, P. viridiflava, P. cannabina pv. alisalensis and X. campestris whereas the former two species were the most abundant in Rhineland Palatinate. Infection trials on radish plants concluded that the different pathogens induced different typical symptom characteristics. To evaluate the influence of environmental factors such as humidity and temperature, it was demonstrated that inoculations with pseudomonads and a leaf spot inducing X. campestris strain caused successful infection and symptom development under a wide temperature range. Humidity was shown to be the most influential factor limiting infestation intensity with P. viridiflava displaying a higher demand for humid conditions than P. syringae pv. maculicola and X. campestris. All three types induced a higher disease infestation on radish plants in high humidity conditions (~94% rH) contrary to a lower infestation in dry conditions (~63% rH). In a first test series, plants inoculated with P. viridiflava were almost symptom free under dry conditions, whereas P. syringae and X. campestris were still able to induce leaf spots. Based on the results of infections assays, it was possible to develop a screening method on radish plants for resistance to the leaf spot inducing bacterial pathogen P. syringae pv. maculicola. The screening method was based on the spray-inoculation of radish leaves fixed in water filled orchid tubes, incubated under high humidity in a climate chamber at 24 °C day/10 °C night. Determination of resistance was performed 7 to 10 days past inoculation by rating disease intensity of infested leaves. Whereas tests could be performed by inoculations with P. viridiflava and P. cannabina as well as P. syringae, the latter proved to be most suitable for the screening method.