Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Starch meets biotechnology : in planta modification of starch composition and functionalities
Xu, Xuan - \ 2016
University. Promotor(en): Richard Visser, co-promotor(en): Luisa Trindade. - Wageningen : Wageningen University - ISBN 9789462579200 - 169
starch - potato starch - potatoes - solanum tuberosum - plant biotechnology - biotechnology - genetic engineering - transgenic plants - modified starches - phosphate - arabidopsis thaliana - plant breeding - zetmeel - aardappelzetmeel - aardappelen - plantenbiotechnologie - biotechnologie - genetische modificatie - transgene planten - gemodificeerd zetmeel - fosfaat - plantenveredeling

Storage starch is an energy reservoir for plants and the major source of calories in the human diet. Starch is used in a broad range of industrial applications, as a cheap, abundant, renewable and biodegradable biopolymer. However, starch needs to be modified before it can fulfill the required properties for specific industrial applications. Genetic modification of starch, as a green technology with environmental and economic advantages, has attracted increasingly attention. Many achievements obtained from earlier studies have demonstrated the feasibility and potential of using this approach to produce starches with novel properties (Chapter 2).

The main objective of this research was to produce novel starches with enhanced functionalities through genetic modification, while gaining a better understanding of storage starch biosynthesis. A focus on potato was warranted as it represents a superior model system for storage starch biosynthesis studies and for the production of starches with novel properties. To this end, a number of enzymes from various sources have been expressed in potato tubers to modify starch phosphate content and polysaccharide structure, since these two characteristics have long been recognized as key features in starch properties.

To modify starch phosphate content and explore starch (de)phosphorylation, a human phosphatase enzyme named laforin, and modifications of it, were introduced into potato (Chapter 3). Interestingly, modified starches exhibited a significantly higher phosphate content rather than the expected lower phosphate content. Transcriptome analysis showed that the increase in phosphate content was a result of upregulation of starch phosphorylating genes, which revealed a compensatory response to the loss of phosphate content in potato starch. Furthermore, the increase of phosphate content in potato starch was reached to a threshold level. This was in line with the observations in the modified starches from overexpressed- Glucan water dikinase (GWD1) transgenic plants (Chapter 4). Furthermore, overexpression of two starch dikinases from Arabidopsis thaliana, glucan water dikinase 2 and 3 (AtGWD2 and AtGWD3), did not result in a significant increase in phosphate content of potato starch (Chapter 5). Taken together, these results indicated that phosphate content of potato starch is under strict control.

Morphological analysis of starch granules containing different levels of phosphate content confirmed the indispensible role of phosphate content in the normal formation of starch granules, since cracked granules were observed in the starches containing low phosphate content, while irregular bumpy shaped granules were observed in the tubers from plants containing high phosphate content. Interestingly, further analyses on the expression level of genes involved in starch metabolism and sugar-starch conversion suggested that starch phosphorylation might affect starch synthesis by controlling the carbon flux into starch while simultaneously modulating starch-synthesizing genes. Further studies are needed to confirm this finding (Chapter 4).

To produce starches with novel structures, an (engineered) 4, 6-α-glucanotransferase (GTFB) from Lactobacillus reuteri 121 was introduced into potato tubers (Chapter 6). The resulting starches showed severe changes in granule morphology, but not in starch fine structure. Transcriptome analysis revealed the existence of a self-repair mechanism to restore the regular packing of double helices in starch granules, which possibly resulted in the removal of novel glucose chains potentially introduced by the (engineered) GTFB.

This research successfully generated starches with various functionalities, including altered gelatinization characteristics (Chapter 3 and 4), improved freeze-thaw stability (Chapter 4) and higher digestibility (Chapter 6). The exploitation of relationships between starch characteristics and starch properties revealed that starch properties represent the outcome of the combined effect of many factors and are highly dependent on the genetic background in which the modification has been performed.

In conclusion, the research described in this thesis demonstrates the great potential of genetic modification in producing starches with novel properties. Meanwhile, these results revealed the presence of complex and exquisite molecular regulation mechanisms for starch biosynthesis in potato. In future research, these regulations need to be taken into account for the relational design of starch in planta. Certainly, a better understanding of the process of starch metabolism in storage organs would be a great step forward towards tailoring starch in an economically important crop such as potato.

Zetmeelkorrels als droogtebuffer
Hoekzema, Gerard ; Kroonen, Marc - \ 2016
starch - maize - zetmeel - maïs
Electrostatic separation for functional food ingredient production
Wang, J. - \ 2016
University. Promotor(en): Maarten Schutyser, co-promotor(en): Remko Boom. - Wageningen : Wageningen University - ISBN 9789462576513 - 176 p.
particles - fractionation - separation - electrostatic separation - sieving - nitrogen - polystyrenes - wheat gluten - arabinoxylans - starch - milling - lupinus - rice bran - food - experiments - deeltjes - fractionering - scheiding - elektrostatische scheiding - zeven (activiteit) - stikstof - polystyrenen - tarwegluten - arabinoxylanen - zetmeel - maling - rijstzemelen - voedsel - experimenten

Summary

Dry fractionation is a promising alternative to wet extraction processes for production of food ingredients, since it uses hardly any water, consumes less energy and retains the native functionality of the ingredients. It combines milling and dry separation to enrich agro-materials in specific components such as protein. Electrostatic separation recently emerged as a novel dry separation process and it relies on electrostatic forces for separation. Though the potential of electrostatic separation to fractionate agro-materials has been demonstrated, the effectiveness in terms of purity and yield and the influence of process parameters on charging and separation of food ingredients have not yet been systematically studied. Therefore, the objective of this thesis was to gain better understanding of the charging and separation behaviour of model and agro-materials, provide insight in the critical factors for successful electrostatic separation and explore the potential of this separation method to different agro-materials.

The charging step is critical to the effectiveness of electrostatic separation and is influenced by many factors. Chapter 2 presents characterization of the charging behaviour of single-component model particles in nitrogen gas flowing through aluminium tubes, using a lab-scale electrostatic separator. Polystyrene particles and wheat gluten were used as model particles. Higher gas velocities led to a higher specific charge by increasing the normal component of impact velocity. Smaller particles gained more specific charge than larger ones because of their higher surface to volume ratio and their sensitivity towards gas flow pattern changes. Longer charging tube lengths allowed more contact between the particles and the wall and therefore resulted in higher specific charge. The relative humidity of the nitrogen gas flow within the range 0 – 60% had no influence on the charging behaviour of both model particles.

Chapter 3 demonstrates the potential of applying electrostatic separation to enrich arabinoxylans from wheat bran with the same lab-scale electrostatic separator. A combination of larger particle size, higher gas velocity and shorter charging tube was preferred for separation, because it sufficiently charged the particles while agglomeration was minimized. Electrostatic separation with the optimum setting achieved a similar enrichment in arabinoxylans (from 23% to 30% dry matter basis) as sieving does. However, the combination of electrostatic separation and sieving further improved the enrichment and resulted in a fraction with an arabinoxylans content of 43% dry matter basis, which is around the maximum achievable purity that can be reached by dry fractionation.

To allow better defined charging and separation experiments, a bench-scale electrostatic separator was designed and constructed. With this custom-built separator, the charging and separation of model mixtures prepared from wheat gluten and starch were studied in chapter 4. The net charge of gluten-starch mixtures was not simply the sum of the charge of the two individual components, indicating that particle-particle interactions play an important role. We hypothesized that the formation of agglomerates between oppositely charged particles negatively influenced separation, which was supported by the fact that the dispersibility for mixtures of the two components was lower compared to that of individual components. We found that during electrostatic separation of mixtures, it is important to find the optimal condition that provides sufficient charge to charges, but avoids agglomeration between oppositely charged particles. This could be achieved by the combination of lower dosing rate and higher gas flow rate.

Chapter 5 reports on dry fractionation by combining milling and electrostatic separation with the custom-built bench-scale separator, providing an alternative to wet extraction of protein from lupine seeds. Relatively coarse milling was preferred because it disclosed sufficient protein bodies from the matrix, while avoiding poor dispersibility of the powder due to its very fine particle size. With the optimal settings of single-step electrostatic separation, a fraction with 57.3 g/100 g dry solids could be obtained. The protein content was further improved to 65.0% dry matter basis after two more separation steps, which is 15% higher than obtained by air classification. The yield of the protein enriched fraction was further increased by recycling the fractions from the filter bags, but this was accompanied by a decrease in protein content and vice versa. A significant shift towards better yield and purities was achieved by re-milling the flour that was not collected on the electrodes. A final fraction with a protein content of 65.1% dry matter basis and a yield of 6% was obtained, which recovered 10% of the protein in the original flour.

Chapter 6 explores the possibility of enriching dietary fibre from defatted rice bran by dry fractionation, where the custom-built bench-scale electrostatic separator was used. All three tested separation routes produced fibre-enriched fractions with similar yield (20 – 21 % of the milled flour) and fibre content (67 – 68 % dry matter basis), which recovered 42 – 48 % of the fibre from the original flour. The enriched fractions obtained by a two-step electrostatic separation process contained more small particles compared to the other two, which resulted in different functional properties. Compared to the total dietary fibre extracted by the enzymatic-gravimetric method, the enriched fractions by dry fractionation had a similar water retention capacity and oil binding capacity. This suggests that the fibre-enriched fractions by dry fractionation can be applied in foods and provide similar technological properties and physiological effects as the wet-extracted dietary fibre does.

Chapter 7 concludes the thesis with a general discussion on the main findings, based on which two schemes for protein enrichment and fibre enrichment were proposed. Subsequently the challenges to achieve a successful electrostatic separation for agro-material and up-scaling are discussed. Finally, the chapter ends with an outlook on future research.

This thesis provided insight in the key factors for successful electrostatic separation. It demonstrated the potential of applying this separation method for functional ingredient production from different agro-materials and also gave directions for further improvement and scaling-up.

Low emission feed : opportunities to mitigate enteric methane production of dairy cows
Hatew, B. - \ 2015
University. Promotor(en): Wouter Hendriks, co-promotor(en): Jan Dijkstra; Andre Bannink; Wilbert Pellikaan. - Wageningen : Wageningen University - ISBN 9789462574458 - 228
melkkoeien - rundveevoeding - methaanproductie - milieueffect - pensfermentatie - voer - zetmeel - maïskuilvoer - graskuilvoer - diervoeding - dairy cows - cattle feeding - methane production - environmental impact - rumen fermentation - feeds - starch - maize silage - grass silage - animal nutrition

As global demand for high-quality food originating from animal production is expected to rise due to an increasing human population and consumer income level, the expected role of ruminants in meeting this demand brings multiple challenges. Ruminant production needs to adapt to environmental changes and, at the same time, reduce its impact on the environment. Ruminants production systems have a major impact on the environment through the emission of greenhouse gases such as methane (CH4), nitrous oxide and carbon dioxide. Microbial fermentation of feeds in the gastrointestinal tract, known as enteric fermentation, is the main source of CH4 emissions from dairy production. Enteric CH4 emission is strongly related to the amount of feed fermented in the rumen, which depends on feed intake, feed composition and rumen fermentation conditions associated to the intrinsic characteristics of these feeds and the characteristics of the whole diet. Important gaps in knowledge remain however. The prime aim of this thesis was to investigate the effects of various feeding strategies to mitigate enteric CH4 emissions of dairy cows.

First experiment was conducted to investigate the effects of type and level of starch in the concentrate. Inclusion of a high level (53%) of starch in the concentrate that accounted for 40% of the total mixed ration dry matter (DM) produced lower CH4 per unit of estimated rumen fermentable organic matter (eRFOM) than a low level (27% of DM) of starch (43.1 vs. 46.9 g/kg of eRFOM). Methane production per kg of eRFOM also was lower for diets based on rapidly fermentable starch (gelatinized maize grain) compared to diets based on slowly fermentable starch (native maize grain) (42.6 vs. 47.4 g/kg of eRFOM). However, inclusion of 53% of starch in the concentrate from both types of starch did not affect CH4 emission intensity (CH4 Ei) (CH4 emission per kg of fat- and protein-corrected milk; FPCM). In a subsequent experiment, maize silage was prepared from whole-plant maize harvested at a very early (25% DM), early (28% DM), medium (32% DM) and late (40% DM) stage of maturity and fed to dairy cows as an alternative to concentrate as starch source. Diet consisted of (on DM basis) 75% maize silage, 20% concentrate and 5% wheat straw. Increasing harvest maturity of maize silage linearly decreased CH4 yield (21.7, 23.0, 21.0 and 20.1 g/kg of DM intake) and CH4 emission as a fraction of gross energy intake (6.3, 6.7, 6.3 and 6.0%). Methane Ei tended to decrease linearly with maturity (13.0, 13.4, 13.2 and 12.1 g/kg FPCM). In another experiment grass silage as roughage source was tested. This experiment was designed to investigate the effects of N fertilisation of grassland and maturity of grass at cutting on CH4 emission in dairy cows. Two N fertilisation rates (65 vs. 150 kg of N/ha) were examined in combination with three stages of grass maturity (early, 28 days of regrowth; mid, 41 days of regrowth; and late, 62 days of regrowth). Diet contained 80:20 ratio (on DM basis) of grass silage (mainly ryegrass) and concentrate. Dry matter intake decreased with N fertilisation and maturity, and FPCM decreased with maturity but was unaffected by N fertilisation. Methane Ei (mean 15.0 g/kg of FPCM) increased by 31% and CH4 per unit digestible OM intake (mean 33.1 g/kg of DOMI) increased by 15% with increasing maturity. Methane yield (mean 23.5 g/kg of DM intake) and CH4 as a fraction of gross energy intake (mean 7%) increased by 7 and 9% with maturity, respectively, which implies an increased loss of dietary energy with progressing grass maturity. Rate of N fertilisation had no effect on CH4 Ei and CH4 yield.

Despite the importance of in vitro gas production technique for evaluating feeds, in vitro study as a stand-alone approach was considered inadequate to fully evaluate the potential effect of feeds and rumen fermentation modifiers on CH4 production, because in vitro studies are frequently performed separately rather than in parallel with in vivo studies. To test this hypothesis, both in vitro and in vivo CH4 measurements were measured simultaneously using cows in the first experiment that were fed (and adapted to) the same dietary material used as a substrate for in vitro incubation, as donor for microbial inoculum. It was found that 24-h in vitro CH4 (mL/g of incubated organic matter) correlated well with in vivo CH4 when expressed per unit of eRFOM (R2 = 0.54), but not when expressed per unit of organic matter ingested (R2 = 0.04). In the same experiment, results showed that incubation of the same substrate with rumen inocula obtained from donor cows adapted to different diets produced a variable amount of CH4 suggesting that it is important to consider the diet of the donor animal when collecting rumen inocula for in vitro incubation. Even though the in vitro technique has limitations to represent in vivo conditions, it is useful for screening of large sets of animal feeds or feed additives to be used as a CH4 mitigation strategy. In this thesis, two in vitro experiments were conducted to examine the effects of variation in structural composition of condensed tannins (CT) in sainfoin accessions collected from across the world on CH4 production, and CT extracts obtained from a selected sainfoin accessions on CH4 production. Results revealed substantial variation among CT in their effect on in vitro CH4 production and this variation was attributed to differences in chemical structure of CT. Condensed tannins evaluated in this thesis showed to have potential to reduce in vitro CH4 production, but require further investigations to fully evaluate their in vivo effects.

In conclusion, results from the research work conducted in this thesis show that changes in the basal diet of dairy cows and in roughage production management can substantially reduce the amount of enteric CH4 produced and thereby influence the impact of dairy production on the environment.

Kinetic modelling of enzymatic starch hydrolysis
Bednarska, K.A. - \ 2015
University. Promotor(en): Tiny van Boekel; Remko Boom, co-promotor(en): Anja Janssen. - Wageningen : Wageningen University - ISBN 9789462573086 - 159
hydrolyse - enzymen - zetmeel - stochastische modellen - verwerking - hydrolysis - enzymes - starch - stochastic models - processing

Kinetic modelling of enzymatic starch hydrolysis – a summary

K.A. Bednarska

The dissertation entitled ‘Kinetic modelling of enzymatic starch hydrolysis’ describes the enzymatic hydrolysis and kinetic modelling of liquefaction and saccharification of wheat starch. After the background information about the enzymes, the substrate and the basics of the model in the first chapter, we describe a model predicting the outcome of wheat starch liquefaction by α-amylase from Bacillus licheniformis at 50°C in chapter 2. We demonstrate the ability of the model to predict starch hydrolysis products larger than the oligosaccharides considered in the existing models. The model in its extended version follows all the products of wheat starch hydrolysis separately, and despite the quantitative differences, the qualitative predictions are satisfactory. We also show that the difference between the experimental and computed data might stem from the inaccuracy of the subsite map.

In the following chapters the model is used to find a better description of the hydrolysis data at two temperatures (50°C and 80°C), by varying the energy values of the subsite map and evaluating the inhibition. We hypothesize that a subsite map that is based on the cleavage patterns of linear, short molecules does not account for the complexity of hydrolysis of amylopectin. The branched structure of amylopectin molecules influences the composition of the hydrolysis products by restricting the access to some of the bonds. The presence of branches creates steric obstacles for the enzyme. The used α-amylase has difficulties hydrolysing and accommodating α-(1,6)-glycosidic bonds, which imposes on the hydrolysis of the α-(1,4)-glycosidic bonds located in its proximity. On this basis, we analyse the subsite maps in detail and suggest which of the subsites are crucial when making predictions about the product composition of starch hydrolysates. On top of that we propose new subsite maps that allow a quantitative description of the experimental data.

After the model was shown to work at different experimental conditions, we also test it at increased the dry matter content during wheat starch hydrolysis. We follow both the liquefaction by BLA and the saccharification process by glucoamylase from Aspergillus niger at low moisture content. The liquefaction model, is used to predict all of the products of wheat starch hydrolysis at higher dry matter contents (30-60 w/w%). The liquefaction model also creates the substrate matrices representing maltodextrins to be used in the saccharification model. The saccharification of liquefacts to glucose is followed with a new mechanistic model, also using the assumptions of the subsite theory. The saccharification model predicts all of the reaction products using the subsite maps of glucoamylase available in literature.

The findings described in the thesis are summarized and put in context in the general discussion. We demonstrate how the parameters of the liquefaction model at low moisture contents were chosen. The outcomes of the model are also compared with the experimental data at 30-60 w/w%. Next, we test our liquefaction model with starch hydrolysis data at 5 and 60 w/w% taken from literature, to verify both the approach we used and the validity of the parameters we obtained in previous chapters. The method used to improve the subsite maps is also tested on another enzyme, Bacillus amyloliquefaciens α-amylase. After discussing the factors that influence saccharification at high dry matter contents, we conclude the chapter with describing the potential of stochastic modelling and its practical use.

Autogenerative high pressure digestion : biogass production and upgrading in a single step
Lindeboom, R.E.F. - \ 2014
University. Promotor(en): Jules van Lier, co-promotor(en): Jan Weijma; Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789461738608 - 208
biogas - spijsvertering - druk - methaanproductie - kooldioxide - zetmeel - hydrolyse - digestion - pressure - methane production - carbon dioxide - starch - hydrolysis
BOGO van groene grondstoffen naar biobased materialen. Van zetmeel naar plastic.
Broek, L.A.M. van den - \ 2013
Wageningen : FBR Wageningen
lesmaterialen - zetmeel - biopolymeren - bioplastics - handleidingen - chemie op basis van biologische grondstoffen - biobased economy - beroepsopleiding (hoger) - teaching materials - starch - biopolymers - guide books - biobased chemistry - professional education
Practicumhandleiding voor hbo. Met behulp van commercieel zetmeel is het mogelijk om gelen te maken. Door het toevoegen van glycerol tijdens het proces kan men de gel flexibeler maken.
Starch identification supported by expert system determinator
Raamsdonk, L.W.D. van; Hekman, W.E. ; Pinckaers, V.G.Z. ; Vliege, J.J.M. ; Ruth, S.M. van - \ 2012
zetmeel - gemodificeerd zetmeel - identificatie - voedselanalyse - starch - modified starches - identification - food analysis
Identification of starch as ingredient is important for a range of purposes. The Starch Identification System as implemented in the platform Determinator is helpful in this respect since it allows consistent identification of starch in a large variety of products.
Smart microgels for controlled uptake and release
Li, Y. - \ 2011
University. Promotor(en): Martien Cohen Stuart; Willem Norde, co-promotor(en): Mieke Kleijn. - [S.l.] : S.n. - ISBN 9789085859994 - 173
gels - zetmeel - colloïden - lysozym - gecontroleerde afgifte - starch - colloids - lysozyme - controlled release

This dissertation describes a systematic study on oxidized starch microgel particles. It begins with the preparation and characterization of oxidized starch gels in terms of some important physical-chemical properties, with the aim to select an optimum gel for further investigation of protein uptake. The gel with the highest degree of oxidation DO100% is chosen for lysozyme uptake because of its high protein uptake capacity and low swelling capacity. In addition, DO30% gels have been used in many experiments, since DO30% starch allows for preparation of well-defined spherical microgel particles and because it is enzymatically degradable. The two main aspects of interest are the protein binding affinity and protein saturation. Neutral pH and low salt concentration are found to be the optimum protein uptake conditions for high protein saturation. For more detailed studies, spherical microgels with a narrow size distribution have been made by optimizing the preparation process. The mobility of lysozyme molecules inside those microgel particles has been investigated. The main conclusion is that high salt and high pH increase the mobility of lysozyme in the gel particles. It implies that high pH and high salt concentration are potential triggers for lysozyme release from the gel. Subsequently, the kinetics of protein release by high pH and high salt concentration is presented. For the aim of application, the antimicrobial activity of lysozyme containing starch gel particles against some bacterial strains is determined. Finally, the deposition of poly-lysine/poly-glutamic acid complex layer around microgel surface is used to stabilize the microgel particle and optimize our system.

Concentrated separation of wheat flour into starch and gluten
Zalm, E.E.J. van der - \ 2011
University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - [S.l.] : S.n. - ISBN 9789085858614 - 171
tarwebloem - tarwegluten - zetmeel - scheiding - afschuifkracht - wheat flour - wheat gluten - starch - separation - shear
Fasevoeding met maïsmeel bij biologisch melkvee
Klop, A. ; Zonderland, J.L. ; Riel, J.W. van - \ 2010
Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 302) - 32
biologische landbouw - maïs - energiebalans - melkproductie - melkveehouderij - maïsmeel - veevoeding - krachtvoeding - zetmeel - organic farming - maize - energy balance - milk production - dairy farming - maize meal - livestock feeding - force feeding - starch
Phase feeding with maize meal in a study with organic dairy cattle resulted in a positive energy balance at the start of lactation, but in a disappointing milk production.. In the trial maize meal was used to provide cattle with extra energy at the beginning of the lactation compared to a ration with maize silage. Feed intake by maize meal-cows was higher, but milk yield lower, resulting in a positive energy balance. Cows that were fed maize silage produced more milk and realised higher returns. Concentrate allocation by using Dynamic Linear Models resulted in additional savings on concentrates. The system offers opportunities for measurement feeding of home- (or regionally-) grown crops.
Zetmeelplastics: eigenschappen en toepassingen
Bolck, C.H. ; Bos, H.L. - \ 2010
zetmeel - biobased economy - bioplastics - biopolymeren - starch - biopolymers
Deze info sheet geeft een overzicht van de herkomst en toepassingsmogelijkheden van bioplastics gebaseerd op zetmeel.
Overzicht zetmeelaardappelrassen 2010
Wijnholds, K.H. - \ 2009
Valthermond : Wageningen UR, Praktijkonderzoek Plant & Omgeving
aardappelen - rassen (planten) - zetmeel - zetmeelgewassen - overzichten - potatoes - varieties - starch - starch crops - reviews
Poster met een overzicht van zetmeel-aardappelrassen in 2010.
Zetmeelplastics : markt en milieu-aspecten
Harmsen, P.F.H. ; Patel, M. - \ 2009
zetmeel - kunststoffen - zetmeelverwerkende industrie - industriële toepassingen - duurzaamheid (sustainability) - bioplastics - biobased economy - starch - plastics - starch industry - industrial applications - sustainability
Zetmeelplastics behoren tot de grootste groep van bioplastics in termen van productie volumes binnen Europa. Deze info sheet geeft info over industriële productie, vervangingspotentieel en duurzaamheid van zetmeelplastics.
Development of starch-based materials
Habeych Narvaez, E.A. - \ 2009
University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - [S.l. : S.n. - ISBN 9789085854333 - 144
zetmeel - mechanische eigenschappen - fysicochemische eigenschappen - verwerking - polymeerchemie - biopolymeren - starch - mechanical properties - physicochemical properties - processing - polymer chemistry - biopolymers
Starch-based materials show potential as fully degradable plastics. However, the current
applicability of these materials is limited due to their poor moisture tolerance and
mechanical properties. Starch is therefore frequently blended with other polymers to make
the material more suitable for special or severe circumstances. By varying the components
of the blend and the process conditions, the morphology and hence the properties can be
controlled. A clear understanding over the structure formation process will allow the
development of new, biodegradable blends based on starch-based materials with better
properties. The overall goal of this thesis was thus to develop insight in how the material
(blend) properties depend on the processing, and based on this insight, explore new
processing routes.
Structure-function relationships: exploring a polymer science approach
In Chapter 2, we discuss the relation between the performance of a plasticized starchbased
film, in terms of permeation of volatile components, and its composition. Estimations
of the Maxwell-Stefan diffusion rates of trace volatile components through plasticized
starch films were developed based on free-volume theory and the Flory-Huggins-Maxwell-
Stefan (FHMS) equation. The model correctly predicted the order of magnitude of the
permeation fluxes of diacetyl and carvone through starch films. The results of this chapter
show that blending of starch with hydrophobic polymers could be an effective way to
improve the barrier properties of the film.
In Chapter 3, the influence of alternative plasticizers (i.e., glucose and glycerol) on the
gelatinization and melting of concentrated starch mixtures was studied, using differential
scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). The results were
interpreted using an extended form of the well-known Flory-Huggins equation. The chapter
exemplified the possibilities of using theories that were traditionally applied to synthetic
polymers, to biomaterials, in spite of their much greater complexity. This approach led to
quantitative and qualitative understanding of the influence of small plasticizers of industrial
relevance on the gelatinization and melting of starch. Comparing the Flory-Huggins model
results with experimental results, showed that the approach is useful for interpreting and
predicting the gelatinization and melting behavior of ternary starch-based systems. It also
showed that since the experiments were complex, systems were often not in true
equilibrium and other disturbing effects were easily encountered. Therefore, one should be
cautious to use experimental results for characterizing the thermodynamics of gelatinization
in multicomponent systems.
Processing: the use of simple shear
In Chapter 4, the use of simple shear as an instrument for structure formation of
plasticized starch-protein blends was introduced. A novel shearing device was developed to
explore the formation of new types of microstructures in concentrated starch-zein blends.
This device was used to process different ratios of starch and zein (0–20% zein, dry basis)
to study the influence of the matrix composition and processing conditions on the
properties of the final material. Confocal scanning laser microscopy and field emission
scanning electron microscopy showed that under shearless conditions, the starch-zein blend
forms a co-continuous blend. Shear transformed this structure into a dispersion, with zein
being the dispersed phase. The large deformation properties were examined by tensile tests
in the flow and the vorticity directions; they could be described using a model for blends
having poor adhesion between the continuous and dispersed phases.
In Chapter 5, we studied the effect of compatibilization, i.e., improvement of the adhesion
between the continuous and dispersed phases in starch-zein blends through the
incorporation of a component having affinity for both phases. Aldehyde starch was
synthesized by introducing a reactive functional group (aldehyde). This group then reacted
in the blend with zein (and/or other components), forming a macromolecular compatibilizer
in situ. The effect of this compatabilizer on the interfacial properties of the blend was
studied using different zein ratios. The blends showed improved adhesion between the zein
and starch phases compared to the blends described in chapter 4. The aldehyde starch
however also influenced the properties of the starch matrix (higher viscosity, stronger
molecular breakdown, browning), which indicates that indeed physical or chemical
crosslinks were formed inside the starch matrix, but on the other hand posed a limitation for
practical applicability.
Chapter 6 presented the use of rise bran extract as a food-grade compatibilizer for starchzein
blends. This material was extracted from rice brans using super-critical water,
probably contains Maillard components and shows activity as radical scavenger,
antioxidant and surfactant. The influence of rice bran extract as compatibilizer was
compared with that of aldehyde starch by preparing blends under shear conditions. Field
emission scanning electron microscopy showed that both compatibilizers improved the
adhesion between the zein and starch phases. The mechanical properties of the blends
compatibilized with aldehyde starch showed poorer mechanical properties after storage
under controlled conditions, possibly caused by retrogradation of starch. The use of rice
bran extract as compatibilizer however led to good compatibilization with good stability
during storage. The good compatibilization by rice bran extract was suggested to be caused
by polysaccharide-protein complexes, which are also responsible for its emulsifying
properties.
Application
In Chapter 7, the conclusions of the preceding chapters were collectively interpreted. First,
the use of a heuristic approach for the rational design of thermoplastic starch-based
materials was described. Then the use of the ternary diagram for the system starch-waterglucose
developed in Chapter 3 was used to evaluate alternatives routes for the
intensification of the enzymatic hydrolysis of starch.
Finally, future trends in the development of starch-based materials were presented
following the insights obtained in this thesis. These include the use of established theories
developed for synthetic polymers, further exploration of the concept of compatibilization of
starch-based blends, and the development of new processing equipment dedicated to
material structuring.
Factors affecting wheat nutritional value for broiler chickens
Gutierrez del Alamo Oms, A. - \ 2009
University. Promotor(en): Martin Verstegen; Leonard den Hartog, co-promotor(en): M.J. Villamide Díaz. - [S.l. : S.n. - ISBN 9789085853237 - 167
vleeskuikens - vleeskuikenresultaten - diervoeding - diervoedering - voedergranen - tarwe - zetmeelvertering - zetmeel - voedingswaarde - broilers - broiler performance - animal nutrition - animal feeding - feed grains - wheat - starch digestion - starch - nutritive value
In Europe, broiler chickens are fed with balanced diets where the energy is mainly supplied by wheat. The feed industry considers wheat a moderately uniform raw material and therefore its energy content and nutrient digestibility are taken from feeding tables (tabulated values) and assigned to all wheat grains. However, all major wheat-producing countries report considerable variability in energy content of wheat which invalidates the assumption of uniformity among wheat grains and forces the industry to look for the factors responsible of the variation. This PhD has focused on the study of factors that affect the nutritional value of wheat for broiler chickens. After the literature review, few nutrient components of the wheat grain (starch and non-starch polysaccharides) where selected and deeper studied in different wheat cultivars fed to broiler chickens. Emphasis was put on the rate of wheat starch digestion by broiler chickens and its effect on broiler performance.
Bioplastics: zetmeel
Bolck, C.H. ; Bos, H.L. - \ 2009
zetmeel - zetmeelverwerkende industrie - industriële toepassingen - herkomst - bioplastics - biobased economy - starch - starch industry - industrial applications - provenance
Deze info sheet geeft een overzicht van de herkomst en toepassingsmogelijkheden van bioplastics gebaseerd op zetmeel. De tekst is gebaseerd op het boekje Bioplastics, één van de uitgaven uit de reeks Groene Grondstoffen
Research news : starch and cellulose chemistry and their products
Haveren, J. van - \ 2008
zetmeel - cellulose - non-food producten - onderzoek - biobased economy - proceskunde - starch - non-food products - research - process engineering
Agrotechnology and Food Sciences Group aims at developing new processes and products based on carbohydrates via chemical, physical or enzymatic modification. Processes are developed to enhance reactivity and reduce the use of chemicals and solvents and improve product performance. Applications are found in the non-food area.
Rassenbulletin aanbevelende rassenlijst: snijmaïs 2009
Groten, J.A.M. - \ 2008
Lelystad : PPO-AGV; HPA - 4
voedergewassen - gewasopbrengst - rassen (planten) - maïs - bloeidatum - schimmelziekten - helminthosporium - verteerbaarheid - zetmeel - droge stof - rassenlijsten - fodder crops - crop yield - varieties - maize - flowering date - fungal diseases - digestibility - starch - dry matter - descriptive list of varieties
Dit Rassenbulletin is een verslag van het officiële Cultuur- en Gebruikswaarde Onderzoek van Snijmaïs dat Praktijkonderzoek Plant & Omgeving (PPO) onderdeel van Wageningen UR uitvoert in opdracht van Plantum-NL. De resultaten van dit onderzoek vormt de basis voor de Aanbevelende Rassenlijst. In tabel 1 zijn de rassen van de Aanbevelende Rassenlijst Snijmaïs 2009 opgenomen, aangevuld met rassen die drie jaar onderzocht zijn (maar niet aanbevelingswaardig) en rassen die nu twee jaar onderzocht zijn.
Multifunctional starch derivatives: synthesis, characterization and properties
Huijbrechts, A.M.L. - \ 2008
University. Promotor(en): Ernst Sudhölter, co-promotor(en): Carmen Boeriu; Maurice Franssen. - [S.l.] : S.n. - ISBN 9789085852506 - 135
maïs - zetmeel - derivaten - synthese - fysicochemische eigenschappen - biodegradatie - maize - starch - derivatives - synthesis - physicochemical properties - biodegradation
The number of food poisoning cases caused by enteropathogens has increased in recent years. A significant part of the outbreaks associated with the consumption of raw vegetables has been attributed to Escherichia coli O157:H7 and Salmonella enterica subsp. enterica serovar Typhimurium. Bovine manure and slurry are the main environmental sources of these pathogens. Thus, reduction of the multiplication of E. coli O157:H7 and Salmonella serovar Typhimurium in cattle and their survival in manure and slurry are important tasks to minimize the risks of contamination of plant products and outbreaks of food-borne diseases. This thesis describes the influence of various environmental factors on survival of E. coli O157:H7 and Salmonella serovar Typhimurium in manure, slurry and soil amended with manure or slurry. Manure or slurry were inoculated with green fluorescent protein transformed strains of both enteropathogens at 106 - 107 cells g-1 dry weight, and their survival was studied in these substrates and in soil amended with inoculated manure or slurry. Population densities of the pathogens and autochthonous microbial communities were determined by dilution plating. The obtained survival data were fitted to non-linear models such as modified logistic or Weibull models, and estimated survival times in various substrates were compared. Analysis of the estimated parameter values showed that the pathogens survived longer at relatively low temperatures under anaerobic conditions especially at high concentrations of easily available substrate. Salmonella serovar Typhimurium was more resistant to environmental stresses than E. coli O157:H7. Survival of both pathogens significantly declined with increasing temperature amplitudes of daily temperature oscillations. Variations in fluctuations of E. coli O157:H7 populations around the decline curve were evaluated by the Approximate Entropy (ApEn) procedure. The instability of E. coli O157:H7 populations around the decline curve was greater in conventional than in organic and in loamy than in sandy soils, even though the mean survival periods did not differ. Multiple regression analysis of instability of E. coli O157:H7 survival on various soil characteristics showed a positive relation with the ratio of copiotrophic / oligotrophic bacteria, suggesting greater instability at higher available substrate concentrations. Percolation experiments with soil columns showed that surface application of solid manure decreased the risk of contamination of ground water and lettuce roots compared to injection of slurry, as more pathogen cells percolated to greater depths after slurry than after manure application. Detection of E. coli O157:H7 could be improved by incubation of Petri plates in anaerobic conditions, as this resulted in significantly higher numbers of recovered cells in comparison with the common aerobic plating procedure. Finally, a simulation model was developed based on our experimental data. The relative effects of temperature and substrate content were more important than that of oxygen concentration. The interaction with substrate resulted in oscillatory behavior of E. coli O157:H7 populations in manure and manure amended soil. Competition for substrate was the most important factor affecting the final survival time. The model was used to evaluate the effects of various manure and soil management scenarios on the survival of E. coli O157:H7. This simulation model provides a new approach to investigate dynamic changes of invasive microorganisms in natural substrates. The results presented in this thesis can be used for risk assessment of E. coli O157:H7 and Salmonella serovar Typhimurium in dairy farming systems and will help to identify and evaluate potential control strategies to minimize the chance of pathogen spread in the vegetable production chain.

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