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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Comparison of Protein Extracts from Various Unicellular Green Sources
Teuling, Emma ; Wierenga, Peter A. ; Schrama, Johan W. ; Gruppen, Harry - \ 2017
Journal of Agricultural and Food Chemistry 65 (2017)36. - ISSN 0021-8561 - p. 7989 - 8002.
amino acid composition - carbohydrate composition - cyanobacteria - Microalgae - physicochemical properties - single-cell protein
Photosynthetic unicellular organisms are considered as promising alternative protein sources. The aim of this study is to understand the extent to which these green sources differ with respect to their gross composition and how these differences affect the final protein isolate. Using mild isolation techniques, proteins were extracted and isolated from four different unicellular sources (Arthrospira (spirulina) maxima, Nannochloropsis gaditana, Tetraselmis impellucida, and Scenedesmus dimorphus). Despite differences in protein contents of the sources (27-62% w/w) and in protein extractability (17-74% w/w), final protein isolates were obtained that had similar protein contents (62-77% w/w) and protein yields (3-9% w/w). Protein solubility as a function of pH was different between the sources and in ionic strength dependency, especially at pH < 4.0. Overall, the characterization and extraction protocol used allows a relatively fast and well-described isolation of purified proteins from novel protein sources.
Extensive dry heating-induced changes in physicochemical and immunological properties of whey proteins
Liu, Fahui - \ 2016
Wageningen University. Promotor(en): Tiny van Boekel; Jan Wichers, co-promotor(en): Kasper Hettinga; Gosia Teodorowicz. - Wageningen : Wageningen University - ISBN 9789463430012 - 146
whey protein - heating - physicochemical properties - immune tolerance - antibodies - allergens - wei-eiwit - verwarming - fysicochemische eigenschappen - immunotolerantie - antilichamen - allergenen

Baked milk products, e.g. milk-protein containing muffins or baked cheese, can be tolerated by most cow’s milk allergic subjects. These products were also reported to contribute to the development of immune tolerance in allergic subjects. The main objective of this thesis was to investigate the effects of heating under dry conditions on the physicochemical and immunological properties of whey proteins. A simplified heating model, consisting of whey proteins and lactose, was used to reproduce baking conditions. Most of the Maillard reaction sites were found to be located in the reported conformational epitopes on whey proteins. Therefore, the structural changes subsequently resulted in a decreased IgG-binding capacity. The binding of glycation products to the receptor of AGE (RAGE) increased with heating time. Next, the formation of AGEs was further studied. Formation of sRAGE-binding ligands depended on the aggregation, “pH”, and aw of the samples. Moreover, the sRAGE-binding activity of the samples after digestion was changed and correlated with the digestibility of samples. Based on these results, a correlation between the formation of AGEs and their immunogenicity was hypothesized. Thus, the macrophage immunogenicity of glycated BLG was furtherly studied. The IgE-binding capacity of glycated samples and their influence on the polarization and gene expression of macrophages were studied in vitro. Glycation of BLG was found to reduce the expression of pro-inflammatory TNF-α, and increase the expression of anti-inflammatory TGF-β in M1 and M2 macrophages. The immunomodulatory potential of glycated BLG was further studied, as described. The uptake of glycated BLG by dendritic cells (DCs) was studied. Results showed that glycated BLG inhibited the degranulation of basophils in a dose-dependent manner. Glycation of BLG enhanced its uptake by DCs. However, the degradation of glycated BLG was faster than unheated BLG, indicating a retarded allergen-presentation efficiency of glycated BLG by DCs.

In conclusion, this thesis showed that extensive dry heating induces profound and specific effects on the physicochemical and immunological properties of whey proteins. Conditions during heating, such as aw and “pH”, affect the consequences of heating on whey proteins and their subsequent functions in interacting with immune cells. Compared to unheated and nonglycated samples, glycated BLG can be more efficiently taken up and degraded by DCs. In addition, glycation confers immunomodulatory properties on whey proteins, as tested in macrophages. These results might have consequences for preparing extensively dry heated allergens that can be used in oral immunotherapy. The data in this thesis also provided a better understanding on the mechanism underlying the observation that the development of immune tolerance can be accelerated by baked milk.

Aqueous fractionation yields chemically stable lupin protein isolates
Berghout, J.A.M. ; Marmolejo-Garcia, C. ; Berton-Carabin, C.C. ; Nikiforidis, C.V. ; Boom, R.M. ; Goot, A.J. van der - \ 2015
Food Research International 72 (2015). - ISSN 0963-9969 - p. 82 - 90.
in-water emulsions - seed oil bodies - oxidative stability - antioxidant properties - lipid oxidation - physicochemical properties - functional-properties - quality - acids - polysaccharides
The chemical stability of lupin protein isolates (LPIs) obtained through aqueous fractionation (AF, i.e. fractionation without the use of an organic solvent) at 4 °C or 20 °C was assessed. AF of lupin seeds results in LPIs containing 2 wt.% oil. This oil is composed of mono- and poly-unsaturated fatty acids and the isolate may thus be prone to lipid and protein oxidation. Lipid and protein oxidation marker values of LPIs obtained at 4 °C and at 20 °C were below the acceptability limit for edible vegetable oils and meat tissue protein; the level of lipid oxidation markers was lower at 20 °C than at 4 °C. The fibre-rich pellet and the protein-rich supernatant obtained after AF also had lower levels of oxidation markers at 20 °C than at 4 °C. This is probably the result of a higher solubility of oxygen in water at lower temperature, which could promote lipid oxidation. The differences between fractions can be explained by the differences in their composition; the fibre-rich pellet contains polysaccharides that potentially have an anti-oxidative effect, while the protein-rich supernatant is rich in sulphur-rich proteins that may scavenge metal ions and free radicals from the aqueous phase. Additionally, the differences in solubility of metal ions and metal-chelating properties of protein at pH 4.5 and pH 7.0 explain the higher level of oxidation in the LPI at pH 4.5 compared with the LPI at pH 7.0. The application of a heat treatment to reduce oxidation decreased the protein and oil recovery values, and increased oxidation values above the acceptability limit. Therefore, AF at 20 °C is the most suitable process to obtain chemically stable LPIs.
A study on the potential of insect protein and lipid as a food source
Yi, L. - \ 2015
Wageningen University. Promotor(en): Tiny van Boekel; Arnold van Huis, co-promotor(en): Catriona Lakemond. - Wageningen : Wageningen University - ISBN 9789462572560 - 186
eiwitbronnen - nieuwe voedingsmiddelen - insecten als voedsel - extractie - eiwitten - vleesvervangers - fysicochemische eigenschappen - protein sources - novel foods - insects as food - extraction - proteins - meat alternates - physicochemical properties

Propositions

Propositions belonging to the thesis, entitled:‘A study on the potential of insect protein and lipid as a food source’. Liya Yi

Wageningen, 9 February 2015.High protein quality is, next to high protein content, a major argument to use insects as an alternative protein source. (this thesis)

With respect to aqueous extraction, proteins from Tenebrio molitor behave similarly as proteins from meat and fish. (this thesis)

In contrast to what Pascucci & Magistris (2013) claim, consumer information is not enough to achieve consumer acceptance of novel food.

Pascucci, S., & Magistris, T. d. (2013). International Food and Agribusiness Management Review, 16, 1-16.

Reducing environmental impact by changing human diet into a plant-based diet (Joyce, Dixon, Comfort, & Hallett, 2012) will not result in meeting the increasing global food demand.Joyce, A., Dixon, S., Comfort, J., & Hallett, J. (2012). Journal of Environmental and Public Health, 2012, 7.

Scientific evidence and the availability of technology are not guarantees for a change in human behaviour.

The statement of the Finnish writer Sebastyne Young “We all want to be extraordinary and we all just want to fit in. Unfortunately, extraordinary people rarely fit in.” applies to science where generation of extraordinary knowledge results in less fitting in.

Oven-drying reduces ruminal starch degradation in maize kernels
Ali, M. ; Cone, J.W. ; Hendriks, W.H. ; Struik, P.C. - \ 2014
Animal Feed Science and Technology 193 (2014). - ISSN 0377-8401 - p. 44 - 50.
physicochemical properties - microwave irradiation - gas-production - rumen fluid - corn-silage - digestibility - grain - degradability - moisture - protein
The degradation of starch largely determines the feeding value of maize (Zea mays L.) for dairy cows. Normally, maize kernels are dried and ground before chemical analysis and determining degradation characteristics, whereas cows eat and digest fresh material. Drying the moist maize kernels (consisting mainly of starch) at high temperatures can influence their physical properties and thus their degradation dynamics in the rumen. We compared the in vitro degradability of dried maize kernels with that of fresh kernels after incubation in rumen fluid. Maize kernels were obtained from genotypes diverse in starch structure, composition and type of endosperm. These genotypes were grown in greenhouses at different temperatures during starch accumulation, and harvested at different maturity stages, in two experiments. Starch content was assessed using the amyloglucosidase method. Fermentation in rumen fluid was measured using an in vitro gas production technique. Starch degradation of the kernels was calculated after 6, 12 and 20 h of incubation in rumen fluid. Oven-drying influenced (P <0.0001) the in vitro degradation of starch in maize kernels at the different incubation times, with more starch being degraded in the fresh than in the oven-dried maize kernels, although the differences were small (11–15%). There was a consistent interaction (P <0.009 to 0.0002) between oven-drying and genotype, with the high-amylose genotype showing larger effects of oven-drying than the other genotypes. The vitreous genotype showed a lower starch degradation than the non-vitreous type. At earlier maturity stages, the difference between oven-dried and fresh kernels was larger than at later maturity stages. The temperature during grain filling affected (P <0.0001) starch degradation but did not affect the difference between fresh and oven-dried samples. Oven-drying reduced the in vitro rumen starch degradation of maize kernels regardless of growing conditions, genotype and maturity stage, but its effect depends on genotype and maturity.
Starch degradation in rumen fluid as influenced by genotype, climatic conditions and maturity stage of maize, grown under controlled conditions
Ali, M. ; Cone, J.W. ; Hendriks, W.H. ; Struik, P.C. - \ 2014
Animal Feed Science and Technology 193 (2014). - ISSN 0377-8401 - p. 58 - 70.
hull-less barley - in-vitro - physicochemical properties - gas-production - dairy-cows - nutritive characteristics - ruminal degradability - high-temperature - amylose content - cereal-grains
Starch is the major component of maize kernels, contributing significantly to the feeding value of forage maize when fed to ruminants. The effects of genotype, climatic conditions and maturity stage on starch content in the kernels and on in vitro starch degradability in rumen fluid were investigated. Kernels of six maize genotypes, differing in amylose content and vitreousness, grown under three contrasting day/night temperature regimes during grain filling, and harvested at different maturity stages from two greenhouse experiments were investigated. Starch content was measured using an enzymatic method and the gas production technique was used to assess starch degradation in rumen fluid of dairy cows. The extent of starch degradation at different incubation times (6, 12 and 20 h) was calculated from measured gas production data (6, 12 and 20 h, respectively) and a published equation. Gas production (ml gas/g OM) showed a positive linear relationship with starch content in the kernels up to a certain level of starch accumulation. At each maturity stage, whole kernel and starch degradation in rumen fluid depended on the genotype (P <0.0001), growing conditions (P <0.0001), starch content (P <0.0001) and starch amount (P <0.0001) in the kernels. While starch content increased with advancing maturity, starch degradation similarly increased up to a certain level of starch content. In vitro starch degradation of the maize kernels in rumen fluid was affected by the starch composition, e.g. amylose and amylopectin content. Starch degradation was inversely related to the amylose content and vitreousness. Higher starch degradation was observed in the waxy (no amylose) and non-vitreous genotypes. The highest starch degradation was observed when plants were grown at intermediate temperatures in both experiments. The difference in starch degradability of each genotype at the same accumulated thermal time, i.e. maturity stage, was due to differences in grain filling rate, caused by the different temperature regimes. This effect of genotype and climatic conditions was consistent for all incubation times (P <0.0001). Rumen in vitro starch degradation is significantly influenced by genotypic, differences in starch content of the maize kernels and their growing conditions.
Comparison of waxy and normal potato starch remaining granules after chemical surface gelatinization: Pasting behavior and surface morphology
Huang, J. ; Chen Zenghong, ; Xu, Yalun ; Li, Hongliang ; Liu, Shuxing ; Yang, Daqing ; Schols, H.A. - \ 2014
Carbohydrate Polymers 102 (2014). - ISSN 0144-8617 - p. 1001 - 1007.
atomic-force microscopy - internal structure - physicochemical properties - noodle quality - yellow pea - amylose - maize - acetylation - sites - wheat
o understand the contribution of granule inner portion to the pasting property of starch, waxy potato starch and two normal potato starches and their acetylated starch samples were subjected to chemical surface gelatinization by 3.8 mol/L CaCl2 to obtain remaining granules. Native and acetylated, original and remaining granules of waxy potato starch had similar rapid visco analyzer (RVA) pasting profiles, while those of two normal potato starches behaved obviously different from each other. All remaining granules had lower peak viscosity than the corresponding original granules. Contribution of waxy potato starch granule's inner portion to the peak viscosity was significant more than those of normal potato starches. The shell structure appearing on the remaining granule surface for waxy potato starch was smoother and thinner than that for normal potato starches as observed by scanning electron microscopy, indicating a more regular structure of shell and a more ordered packing of shell for waxy potato starch granules. The blocklet size of waxy potato starch was smaller and more uniform than those of normal potato starches as shown by atomic force microscopy images of original and remaining granules. In general, our results provided the evidence for the spatial structure diversity between waxy and normal potato starch granules: outer layer and inner portion of waxy potato starch granule had similar structure, while outer layer had notably different structure from inner portion for normal potato starch granule.
Effect of Glycation on the Flocculation Behavior of Protein-Stabilized Oil-in-Water Emulsions
Delahaije, R.J.B.M. ; Gruppen, H. ; Nieuwenhuijzen, N.H. van; Giuseppin, M.L.F. ; Wierenga, P.A. - \ 2013
Langmuir 29 (2013)49. - ISSN 0743-7463 - p. 15201 - 15208.
bovine serum-albumin - beta-lactoglobulin - physicochemical properties - adsorption dynamics - disjoining pressure - alpha-lactalbumin - interfaces - particles - thickness - size
Glycation of proteins by the Maillard reaction is often considered as a method to prevent flocculation of protein-stabilized oil-in-water emulsions. The effect has been suggested, but not proven, to be the result of steric stabilization, and to depend on the molecular mass of the carbohydrate moiety. To test this, the stabilities of emulsions of patatin glycated to the same extent with different mono- and oligosaccharides (xylose, glucose, maltotriose, and maltopentaose) were compared under different conditions (pH and electrolyte concentration). The emulsions with non-modified patatin flocculate under conditions in which the zeta potential is decreased (around the iso-electric point and at high ionic strength). The attachment of monosaccharides (i.e., glucose) did not affect the flocculation behavior. Attachment of maltotriose and maltopentaose (Mw > 500 Da), on the other hand, provided stability against flocculation at the iso-electric point. Since the zeta potential and the interfacial properties of the emulsion droplets are not affected by the attachment of the carbohydrate moieties, this is attributed to steric stabilization. Experimentally, a critical thickness of the adsorbed layer required for steric stabilization against flocculation was found to be 2.29–3.90 nm. The theoretical determination based on the DLVO interactions with an additional steric interaction coincides with the experimental data. Hence, it can be concluded that the differences in stability against pH-induced flocculation are caused by steric interactions.
Effect of matrix and particle type on rheological, textural and structural properties of broccoli pasta and noodles
Silva, E. ; Sagis, L.M.C. ; Linden, E. van der; Scholten, E. - \ 2013
Journal of Food Engineering 119 (2013)1. - ISSN 0260-8774 - p. 94 - 103.
sweet-potato starch - scanning microscopy clsm - physicochemical properties - gluten network - asian noodles - quality - flour - spaghetti - products - dough
Durum wheat semolina (DWS) pasta and sweet potato starch (SPS) noodles were incorporated with dif ferent volume fractions and types of broccoli powder (up to 20% v/v). The incorporation of high volume fractions of broccoli powder produced in-house in SPS noodles increases the modulus of the dough and the stiffness and strength of the noodles as these broccoli particles can swell to up to 7.6 times their original volume. This effect is smaller when commercially available broccoli powder is used, as this powdercan only swell 2.6 times. These results are confirmed by CLSM images. The incorporation of the two types of broccoli powder in DWS shows little effect on the rheology of this system. Since there is no difference between the water binding capacity of SPS and DWS, the small effects on rheology observed in the DWS system are due to the strong gluten network that can prevent the broccoli particles from swelling.
Emulsion properties of algae soluble protein isolate from Tetraselmis sp.
Schwenzfeier, A. ; Helbig, A. ; Wierenga, P.A. ; Gruppen, H. - \ 2013
Food Hydrocolloids 30 (2013)1. - ISSN 0268-005X - p. 258 - 263.
in-water emulsions - diffusing wave spectroscopy - whey-protein - physicochemical properties - stabilized emulsions - flocculation - emulsifiers - adsorption - microalgae - pectin
To study possible applications of microalgae proteins in foods, a colourless, protein-rich fraction was isolated from Tetraselmis sp. In the present study the emulsion properties of this algae soluble protein isolate (ASPI) were investigated. Droplet size and droplet aggregation of ASPI stabilized oil-in-water emulsions were studied as function of isolate concentration (1.25–10.00 mg/mL), pH (3–7), and ionic strength (NaCl 10–500 mM; CaCl2 0–50 mM). Whey protein isolate (WPI) and gum arabic (GA) were used as reference emulsifiers. The lowest isolate concentrations needed to reach d32 = 1 µm in 30% oil-in-water emulsions were comparable for ASPI (6 mg/mL) and WPI (4 mg/mL). In contrast to WPI stabilized emulsions ASPI stabilized emulsions were stable around pH 5 at low ionic strength (I = 10 mM). Flocculation only occurred around pH 3, the pH with the smallest net droplet ¿-potential. Due to the charge contribution of the anionic polysaccharide fraction present in ASPI its droplet ¿-potential remained negative over the whole pH range investigated. An increase in ionic strength (=100 mM) led to a broadening of the pH range over which the ASPI stabilized emulsions were unstable. GA emulsions are not prone to droplet aggregation upon changes in pH or ionic strength, but much higher concentrations are needed to produce stable emulsions. Since ASPI allows the formation of stable emulsions in the pH range 5–7 at low protein concentrations, it can offer an efficient natural alternative to existing protein–polysaccharide complexes.
Effect of combining in vitro estrogenicity data with kinetic characteristics of estrogenic compounds on the invivo predictive value
Punt, A. ; Brand, W. ; Murk, A.J. ; Wezel, A.P. van; Schriks, M. ; Heringa, M.B. - \ 2013
Toxicology in Vitro 27 (2013)1. - ISSN 0887-2333 - p. 44 - 51.
rat uterotrophic bioassay - human-liver-microsomes - bisphenol-a - physicochemical properties - er-alpha - antiestrogenic activity - drug-discovery - receptor-alpha - oecd program - binding
With the ultimate aim of increasing the utility of in vitro assays for toxicological risk assessment, a method was developed to calculate in vivo estrogenic potencies from in vitro estrogenic potencies of compounds by taking into account systemic availability. In vitro estrogenic potencies of three model compounds (bisphenol A, genistein, and 4-nonylphenol) relative to ethinylestradiol (EE2), determined with the estrogen receptor alpha (ERa) transcriptional activation assay using hER-HeLa-9903 cells, were taken from literature and used to calculate the EE2 equivalent (EE2EQ) effect doses in the predominantly ERa-dependent rat uterotrophic assay. Compound-specific differences in hepatic clearance relative to the reference compound EE2 were determined in vitro to examine whether in vivo estrogenic potencies reported in literature could be more accurately estimated. The EE2EQ doses allowed to predict in vivo uterotrophic responses within a factor of 6-25 and the inclusion of the hepatic clearance further improved the prediction with a factor 1.6-2.1 for especially genistein and bisphenol A. Yet, the model compounds still were less potent in vivo than predicted based on their EE2 equivalent estrogenic potency and hepatic clearance. For further improvement of the in vitro to in vivo predictive value of in vitro assays, the relevance of other kinetic characteristics should be studied, including binding to carrier proteins, oral bioavailability and the formation of estrogenic metabolites
Production of oligosaccharides from extruded wheat and rye biomass using enzymatic treatment
Makaravicius, T. ; Basinskiene, L. ; Juodeikiene, G. ; Gool, M.P. van; Schols, H.A. - \ 2012
Catalysis today 196 (2012)1. - ISSN 0920-5861 - p. 16 - 25.
secale-cereale l. - dietary fiber - nonstarch polysaccharides - extrusion-cooking - physicochemical properties - extractable arabinoxylans - xylo-oligosaccharides - functional-properties - eucalyptus wood - harvest year
Research on prebiotics and other novel healthpromoting food components has been active for over a decade. Arabinoxylan (AX) derived arabinoxylooligosaccharides (AXOS), which may have various chemical structures, depending on the xylan source and the degradation method used, stand increasingly in the spotlight as potential prebiotics. During the past decade, the studies of the possibilities to produce the AXOS by using biocatalytic conversion have received more attention. In addition, there is an interest in the use of novel cereal biomass for the production of AXOS. The aim of this study was to investigate the influence of various commercial enzyme preparations on the degradability of insoluble arabinoxylans in wheat and rye wholemeal treated by extrusion, identify and quantify xylooligosaccharides (XOS) and arabinoxylooligosaccharides (AXOS) in treated media. The enzymatic degradation of rye and wheat cell wall materials was monitored by HPSEC, HPAEC and MALDITOFMS techniques. It was noticed that there is no significant difference between extruded and natural cereals, and type of cereals had not significant influence on XOS and AXOS production. The most effective biocatalysts were hemicellulases expressed in the enzyme preparations from Trichoderma and Aspergillus spp. (Depol 692), Humicola and Bacillus spp. (Ceremix Plus). Degradability of rye and wheat cell wall materials by these enzyme preparations obtained break down percentages of 70–87% and 67–77%, respectively. After enzymatic treatment, only small amounts of xylose, xylobiose, and xylotriose was eluted compare to the amount of more complex oligosaccharides with higher degree of polymerization (DP). The mass spectra of oligosaccharides indicated the presence of a homologous series of pentoses ranging from DP 4 to 15. This indicates that chosen enzyme preparations acted well on wheat and rye biomass, and released quite high amounts of XOS and AXOS.
Molecular and Morphological Aspects of Annealing-Induced Stabilization of Starch Crystallites
Gomand, S.V. ; Lamberts, L. ; Gommes, C.J. ; Visser, R.G.F. ; Delcour, J.A. ; Goderis, B. - \ 2012
Biomacromolecules 13 (2012)5. - ISSN 1525-7797 - p. 1361 - 1370.
x-ray-scattering - intermediate water-content - heat-moisture-treatment - potato starches - physicochemical properties - maize starches - wheat starches - amylose-free - polymers - gelatinization
A unique series of potato (mutant) starches with highly different amylopectin/amylose (AP/AM) ratios was annealed in excess water at stepwise increasing temperatures to increase the starch melting (or gelatinization) temperatures in aqueous suspensions. Small-angle X-ray scattering (SAXS) experiments revealed that the lamellar starch crystals gain stability upon annealing via thickening for high-AM starch, whereas the crystal surface energy decreases for AM-free starch. In starches with intermediate AP/AM ratio, both mechanisms occur, but the surface energy reduction mechanism prevails. Crystal thickening seems to be associated with the cocrystallization of AM with AP, leading to very disordered nanomorphologies for which a new SAXS data interpretation scheme needed to be developed. Annealing affects neither the crystal internal structure nor the spherulitic morphology on a micrometer length scale.
The relation between farming practices, ecosystem, and white spot in syndrome virus (WSSV) disease outbreaks in penaeus monodon farms in the Philippines
Tendencia Alapide, E. - \ 2012
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Roel Bosma; J.H. Primavera. - S.l. : s.n. - ISBN 9789461733702 - 135
garnalen - witte-vlekken-syndroom-virus - garnalenteelt - uitbraken (ziekten) - epidemiologie - infectieziekten - dierziektepreventie - aquatische ecosystemen - fysicochemische eigenschappen - mangroves - filippijnen - shrimps - white spot syndrome virus - shrimp culture - outbreaks - epidemiology - infectious diseases - animal disease prevention - aquatic ecosystems - physicochemical properties - philippines

The white spot syndrome virus (WSSV) affecting shrimp aquaculture in most producing countries has caused huge economic losses resulting in bankruptcy to both large and small farmers. Studies done on WSSV epidemiology were mostly tank-based and on species other than Penaeus monodon. There is a need to investigate WSSV epidemiology in P. monodon in on-farm situations, thus including both risk and protective factors. This thesis aimed to generate knowledge that can improve prevention against WSSV in shrimp culture through better farm husbandry by studying the epidemiology of WSSV in on-farm situations. To achieve this goal data from cross-sectional and case studies were analysed to identify on-farm WSSV risk and protective factors, and longitudinal studies were done to assess factors affecting water quality and causing WSSV infection to result in an outbreak.

The thesis identified the following WSSV risk factors related to the physico-chemical parameters of the water: low and fluctuating temperature, low and fluctuating salinity, and pH fluctuation. The risk of high temperature and high salinity for an outbreak of WSV disease may be related to fluctuations in these two parameters. Risk factors related to farm husbandry techniques were feeding with molluscs, sludge removal and its deposition on the dike, sharing water source with other farms and having the same receiving and intake water. Identified WSSV protective factors were high mangrove to pond area ratio, feeding with natural food or phytoplankton, and higher percentage of beneficial bacteria like the yellow colonies that grow on thiosulphate citrate bilesalt sucrose agar, a Vibrio selective medium.

Results of the longitudinal studies demonstrated that WSSV infection may not result in outbreaks in greenwater pond and in ponds with mangroves in the receiving environment. Our results did not provide explanations why the WSSV infection did not result in an outbreak in farms with mangroves in the receiving environment. In greenwater ponds, this was attributed to the better water and soil quality, higher plankton count, and higher heterotrophic bacterial count.

A limited set of starch related genes explain several interrelated traits in potato
Werij, J.S. ; Furrer-Verhorst, M. ; Eck, H.J. van; Visser, R.G.F. ; Bachem, C.W.B. - \ 2012
Euphytica 186 (2012)2. - ISSN 0014-2336 - p. 501 - 516.
adp-glucose pyrophosphorylase - physicochemical properties - diploid potato - quality traits - water dikinase - alpha-glucan - amylose-free - tuber - inhibition - synthase
To understand the molecular basis of potato starch related traits and the underlying starch biosynthesis and degradation, a Quantitative Trait Locus (QTL) analysis in combination with a candidate gene approach was performed. The diploid mapping population C × E, consisting of 249 individuals, was assayed over two consecutive years, for chipping colour, cold induced sweetening, starch content, starch granule size, starch gelling temperature, starch enthalpy, amylose content and degree of starch phosphorylation. QTLs were observed for all traits, except enthalpy on eight out of the twelve potato chromosomes. Several QTLs were found to be consistent over 2 years. Clustering of co-localizing QTLs was observed on some chromosomes, indicating common genetic factors for the different traits. On chromosome 2, Soluble Starch Synthase 2 mapped on the same position as QTLs for starch phosphorylation, starch gelling temperature and amylose content. a-glucan, water dikinase co-localizes on chromosome 5 together with QTLs for starch phosphorylation and cold induced sweetening. Furthermore, the genes coding for two phosphorylases (StPho1a and StPho2) coincide with QTLs for starch gelling temperature, chipping colour and starch granule size on chromosome 2 and a QTL for starch phosphorylation on chromosome 9, respectively. The results suggest allelic variation acting on the genetics of the different traits
Substituent distribution within cross-linked and hydroxypropylated sweet potato starch and potato starch
Zhao, J. ; Schols, H.A. ; Chen Zenghong, ; Jin Zhengyu, ; Buwalda, P.L. ; Gruppen, H. - \ 2012
Food Chemistry 133 (2012)4. - ISSN 0308-8146 - p. 1333 - 1340.
waxy maize starch - physicochemical properties - acetyl substitution - amylopectin starch - root starches - populations - granules - linking - tuber
Revealing the substituents distribution within starch can help to understand the changes of starch properties after modification. The distribution of substituents over cross-linked and hydroxypropylated sweet potato starch was investigated and compared with modified potato starch. The starches were cross-linked with sodium trimetaphosphate and/or hydroxypropylated with propylene oxide. The native and modified starches were gelatinized and hydrolysed by pullulanase, ß-amylase, a-amylase and a combination of pullulanase, a-amylase and amyloglucosidase. The hydrolysates were analysed by HPSEC, HPAEC and MALDI-TOF mass spectrometry. Cross-linking had only a slight effect on the enzymatic hydrolysis, where hydroxypropylation evidently limited the enzymatic hydrolysis. The results obtained suggest that the hydroxypropyl substituents are not distributed regularly over the starch chains. Although the average substitution was around 2 hydroxypropyl groups per 10 glucose units, in the enzyme digests of hydroxypropylated starches, oligomer fragments of 10–15 glucose units, carrying 5–8 hydroxypropyl groups, were identified. It is hypothesised that higher levels of substituents are present in the amorphous regions and periphery of clusters of starch granules. This is the first time that the location of hydroxypropyl groups within sweet potato starch has been examined in this detail. Despite significant differences in granule architecture between starches from potato and sweet potato, similar patterns of hydroxypropylation have been found.
Use of reactive materials to bind phosphorus
Chardon, W.J. ; Groenenberg, J.E. ; Temminghoff, E.J.M. ; Koopmans, G.F. - \ 2012
Journal of Environmental Quality 41 (2012)3. - ISSN 0047-2425 - p. 636 - 646.
water-treatment residuals - acid-mine-drainage - ferric hydroxide - organic-matter - waste-water - physicochemical properties - adsorption filters - sorption capacity - agricultural land - aqueous-solution
Phosphorus (P) losses from agricultural soils have caused surface water quality impairment in many regions of the world, including The Netherlands. Due to the large amounts of P accumulated in Dutch soils, the generic fertilizer and manure policy will not be sufficient to reach in time the surface water quality standards of the European Water Framework Directive. Additional measures must be considered to further reduce P enrichment of surface waters. One option is to immobilize P in soils or manure or to trap P when it moves through the landscape by using reactive materials with a large capacity to retain P. We characterized and tested two byproducts of the process of purification of deep groundwater for drinking water that could be used as reactive materials: iron sludge and iron-coated sand. Both materials contain low amounts of inorganic contaminants, which also have a low (bio) availability, and bound a large amount of P. We could describe sorption of P to the iron sludge in batch experiments well with the kinetic Freundlich equation (Q = a × tm × Cn). Kinetics had a large influence on P sorption in batch and column experiments and should be taken into account when iron-containing materials are tested for their capability to immobilize or trap P. A negative aspect of the iron sludge is its low hydraulic conductivity; even when mixed with pure sand to a mixture containing 20% sludge, the conductivity was very low, and only 10% sludge may be needed before application is possible in filters or barriers for removing P from groundwater. Due to its much higher hydraulic conductivity, iron-coated sand has greater potential for use under field conditions. Immobilizing P could be an option for using iron sludge as a reactive material.
Rheological properties of patatin gels compared with ß-lactoglobulin, ovalbumin, and glycinin
Creusot, N.P. ; Wierenga, P.A. ; Laus, M.C. ; Giuseppin, M.L.F. ; Gruppen, H. - \ 2011
Journal of the Science of Food and Agriculture 91 (2011)2. - ISSN 0022-5142 - p. 253 - 261.
heat-induced gelation - sunflower helianthus-annuus - potato-tuber protein - ionic-strength - whey proteins - egg-white - soy glycinin - physicochemical properties - interchange reactions - induced denaturation
BACKGROUND: The thermal unfolding and rheological properties of patatin gels were compared with those of commonly used proteins (ß-lactoglobulin, ovalbumin, glycinin). RESULTS: A significant difference between these proteins was observed in both the denaturation temperature (59 °C for patatin; about 20 °C lower than the other proteins) and the onset temperature of gel formation (50–60 °C, compared to 70–85 °C for the other proteins). At low ionic strength the minimal concentration was only 6% (w/v) for patatin, compared to 8–11% for the other proteins. This effect was attributed to the relatively high exposed hydrophobicity of patatin as determined by hydrophobic interaction chromatography. For gels compared at ‘iso-strength’, the frequency dependence was found to be close to identical, while small differences were observed in the strain at fracture. CONCLUSIONS: Patatin was found to form gels with comparable small-deformational rheological properties as typical food proteins. In addition, at concentrations where the elastic modulus was similar for all proteins, the frequency and strain dependence were also comparable. From this it is concluded that patatin is a promising protein to be used in food applications as a gelling agent.
Prediction of the state diagram of starch water mixtures using the Flory--Huggins free volume theory
Sman, R.G.M. van der; Meinders, M.B.J. - \ 2011
Soft Matter 7 (2011)2. - ISSN 1744-683X - p. 429 - 442.
glass-transition temperatures - phase-transitions - aqueous-solutions - physicochemical properties - light-scattering - molecular-weight - corn starch - thermal characterization - crystalline polymorph - scanning calorimetry
In this paper we analyse the phase and state transitions of starch and other glucose homopolymers and oligomers using the free volume extension of the Flory–Huggins theory by Vrentas and Vrentas, combined with the Couchman–Karasz theory for the glass transition. Using scaling relations of model parameters with molar weight we have obtained accurate predictions of moisture sorption and the freezing, boiling, and melting data obtained from literature for starch, dextrans, pullulan and maltodextrins. With the estimated model parameters we can construct the complete state diagram for starch, which can now be used as a quantitative tool for design and analysis of food structuring processes.
Genetic parameters for milk coagulation properties in Estonian Holstein cows.
Vallas, M. ; Bovenhuis, H. ; Kaart, T. ; Parna, K. ; Kiiman, H. - \ 2010
Journal of Dairy Science 93 (2010)8. - ISSN 0022-0302 - p. 3789 - 3796.
cheese-making properties - finnish ayrshire cows - somatic-cell count - bovine-milk - chemical-composition - renneting properties - production traits - dairy-cows - physicochemical properties - protein-composition
The objective of this study was to estimate heritabilities and repeatabilities for milk coagulation traits [milk coagulation time (RCT) and curd firmness (E30)] and genetic and phenotypic correlations between milk yield and composition traits (milk fat percentage and protein percentage, urea, somatic cell count, pH) in first-lactation Estonian Holstein dairy cattle. A total of 17,577 test-day records from 4,191 Estonian Holstein cows in 73 herds across the country were collected during routine milk recordings. Measurements of RCT and E30 determined with the Optigraph (Ysebaert, Frepillon, France) are based on an optical signal in the near-infrared region. The cows had at least 3 measurements taken during the period from April 2005 to January 2009. Data were analyzed using a repeatability animal model. There was substantial variation in milk coagulation traits with a coefficient of variation of 27% for E30 and 9% for the log-transformed RCT. The percentage of variation explained by herd was 3% for E30 and 4% for RCT, suggesting that milk coagulation traits are not strongly affected by herd conditions (e.g., feeding). Heritability was 0.28 for RCT and 0.41 for E30, and repeatability estimates were 0.45 and 0.50, respectively. Genetic correlation between both milk coagulation traits was negligible, suggesting that RCT and E30 have genetically different foundations. Milk coagulation time had a moderately high positive genetic (0.69) and phenotypic (0.61) correlation with milk pH indicating that a high pH is related to a less favorable RCT. Curd firmness had a moderate positive genetic (0.48) and phenotypic (0.45) correlation with the protein percentage. Therefore, a high protein percentage is associated with favorable curd firmness. All reported genetic parameters were statistically significantly different from zero. Additional univariate random regression analysis for milk coagulation traits yielded slightly higher average heritabilities of 0.38 and 0.47 for RCT and E30 compared with the heritabilities of the repeatability model.
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