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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    A framework for selecting and designing policies to reduce marine plastic pollution in developing countries
    Alpizar, F. ; Carlsson, F. ; Lanza, G. ; Carney, B. ; Daniels, R.C. ; Jaime, M. ; Ho, T. ; Nie, Z. ; Salazar, C. ; Tibesigwa, B. ; Wahdera, S. - \ 2020
    Environmental Science & Policy 109 (2020). - ISSN 1462-9011 - p. 25 - 35.
    behavioral change - developing countries - Plastic pollution - policy tools

    The polluting of marine ecosystems with plastics is both a global and a local problem with potentially severe consequences for wildlife, economic activity, and human health. It is a problem that originates in countries’ inability to adequately manage the growing flow of waste. We use an impact pathway framework to trace the flow of plastics through the socio-ecological system and identify the role of specific policy instruments in achieving behavioral changes to reduce marine plastic waste. We produce a toolbox for finding a policy that is suitable for different countries. We use the impact pathway and toolbox to make country-specific recommendations that reflect the reality in each of the selected countries.

    Digital soil mapping and GlobalSoilMap. Main advances and ways forward
    Arrouays, Dominique ; Poggio, Laura ; Salazar Guerrero, Osvaldo A. ; Mulder, Vera Laetitia - \ 2020
    Geoderma Regional 21 (2020). - ISSN 2352-0094
    Achievements - Challenges - Digital soil mapping - GlobalSoilMap - Multiple soil classes - Working plans

    In this concluding paper, we summarize the main advances coming forward from the joint conference of the International Union of Soil Sciences (IUSS) Working Groups (WG) “Digital Soil mapping” (DSM) and “GlobalSoilMap”. We outline the increased availability of data and covariates. Large efforts to rescue legacy data and to put them in a harmonized format are ongoing in many parts of the world. New countries are joining the GlobalSoilMap initiative. During the same time, significant progress have been made in the countries which were among the first to develop GlobalSoilMap products. We stress the recent trends in tools used for predictive mapping of soil properties. Some solutions were proposed to solve issues about data privacy. We give examples on how to move from DSM soil digital soil mapping assessment. Aligning our research with ongoing activities within the Global Soil Partnership of the FAO has been proven successful. A need was expressed to work on the uncertainty of indicators of prediction performances and to re-evaluate validation strategies. It is necessary to develop more intuitive metrics for uncertainty assessment for interpreting and evaluating soil maps. The main progresses, remaining issues and challenges and the way forward are summarized and we propose ambitious working plans and road-maps for the two WGs and stress their complementarities.

    Warmtebehandeling raapzaad onderzoek: promotie onderzoek Sergio Salazar Villanea
    Salazar Villanea, Sergio - \ 2020

    Promotieonderzoek Sergio Salazar Villanea

    Processing temperature and sugar type affect the nutritional value, the extent and the rate of proteolysis of a soy protein isolate
    Salazar Villanea, S. ; Bruininx, E.M.A.M. ; Poel, A.F.B. van der - \ 2019
    In: Book of Abstracts IFTC 2019 - 1st International Feed Technology Congress. - - p. 28 - 28.
    Molecular characterization of Ecuadorian quinoa (Chenopodium quinoa Willd.) diversity : implications for conservation and breeding
    Salazar, Juan ; Jaramillo Roman, Viviana ; Gutierrez, Bernardo ; Loo, E.N. van; Lourdes Torres, María de; Torres, Andrés Francisco - \ 2019
    Euphytica 215 (2019)3. - ISSN 0014-2336
    Breeding - Ecuador - Genetic diversity - Population structure - Quinoa - SSR

    Quinoa (Chenopodium quinoa Willd.) is recognized as an important crop to improve global food security. It has gained international recognition because of the nutritional value of its seeds and its broad agronomic resilience. Although several studies have attempted to characterize the genetic diversity of quinoa, none have focused on evaluating germplasm from Ecuador; the latter considered a relevant subcenter of diversity for the species. In this study, 84 accessions representing the species’ cultivated range in the Ecuadorian Andes were characterized using 15 species-specific SSR markers. The extent of allelic richness (196 alleles) and genetic heterozygosity (H E = 0.71) detected for these accessions demonstrate that Ecuadorian quinoa is highly diverse. Phenetic analyzes structured Ecuadorian germplasm into 3 subgroups; each containing genotypes from all surveyed provinces. Average expected heterozygosity was high for all 3 subgroups (0.53 ≤ H E ≤ 0.72), and Nei-pairwise comparisons showed significant genetic divergence among them (0.31 ≤ Nei DST ≤ 0.84). The lack of a clear geographic pattern in the genetic structure of Ecuadorian quinoa led us to believe that the 3 reported subgroups constitute independent genetic lineages representing ancestral landrace populations which have been disseminated throughout Ecuador via informal seed networks. Nevertheless, a Wilcoxon test showed that at least one subgroup had been subject to intensive inbreeding and selection; and possibly corresponds to the local commercial variety INIAP-Tunkahuan. Our results show that ancestral quinoa diversity in Ecuador has prevailed despite the introduction of commercial varieties, and should be preserved for future use in breeding programs.

    Correction to: Molecular characterization of Ecuadorian quinoa (Chenopodium quinoa Willd.) diversity: implications for conservation and breeding
    Salazar, Juan ; Roman, Viviana Jaramillo ; Gutierrez, Bernardo ; Loo, Eibertus Nicolaas van; Lourdes Torres, María de; Torres, Andrés Francisco - \ 2019
    Euphytica 215 (2019)12. - ISSN 0014-2336

    Due to an unfortunate error of miscommunication, two of the co-authors of this manuscript were omitted from the original publication. The correct representation of the authors and their affiliations are listed here and should be treated as definitive. Juan Salazar1, Viviana Jaramillo Roman2, Bernardo Gutierrez1,3, Eibertus Nicolaas van Loo2, Mari´a de Lourdes Torres1, Andre´s Francisco Torres1,2 1. Laboratorio de Biotecnologi´a Vegetal, Colegio de Ciencias Biolo´gicas y Ambientales, Universidad San Francisco de Quito USFQ, Diego de Robles y Vi´a Interocea´nica, Cumbaya´, Ecuador 2. Wageningen UR Plant Breeding, Wageningen University and Research, PO Box 386, 6700 AJ Wageningen, The Netherlands 3. Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK Furthermore, the acknowledgments section has been adapted to match the changes in authorship. The corrected acknowledgements, presented below, are definitive: This research was funded with a Chancellor’s Grant (2015) from Universidad San Francisco de Quito USFQ (Quito-Ecuador). Germplasm access and research permit were granted by the Ministry of Environment of Ecuador (MAE-DNB-CM-2016- 0044). The authors would like to acknowledge the technical assistance offered by researchers at the Plant Biotechnology Laboratory (COCIBA, USFQ), as well as Dr. Leonardo Zurita for his assistance with georeferenced mapping. The authors would also like to acknowledge Dr. Gerard van der Linden (Wageningen University and Research) for supporting our efforts to search and collect quinoa germplasm throughout the Andes of Ecuador.

    Invited response to keynote 'Labor Regimes of Indenture - Migrant Domestic Work' by Rhacel Salazar Parreñas
    Lin, Trista - \ 2018
    An anatomy of colonial states and fiscal regimes in Portuguese Africa: long-term transformations in Angola and Mozambique, 1850s-1970s
    Alexopoulou, Kleoniki - \ 2018
    Wageningen University. Promotor(en): E.H.P. Frankema; E.J.V. van Nederveen Meerkerk, co-promotor(en): J.M.H.M. Santos. - Wageningen : Wageningen University - ISBN 9789463433747 - 220

    This thesis studies colonial state formation and transformations of fiscal regimes in Portuguese Mozambique and Angola, from the military occupation of the coastal regions during the 1850s-1880s to the era of independence granted, after a long war, in the 1960s-1970s. It focuses on three key questions. First, how did Portugal effectively occupy the African territories of Angola and Mozambique, secure revenue and maintain its colonies for such a long period, and why did it rely on heavy coercion and repression over long-term efforts to build consensus and enhance the legitimacy of colonial rule? Second, what were the similarities and differences between the two colonies of Angola and Mozambique in the process of fiscal capacity building? Third, how can the challenge to secure Portuguese Africa in military and fiscal terms be conceptualized in the broader context of European imperialism in Sub-Saharan Africa, especially given the limited military, economic and diplomatic leverage of the metropole?

    To answer these questions I have collected data from archival and published sources and reconstructed annual time series showing long-term fiscal trends. I study the impact of the Portuguese metropolitan identity and local African conditions, such as geography, demography as well as access to land, capital and labour, on the design of colonial fiscal systems. I use comparative historical methods and perspectives, with a focus on the similarities and differences with Britain and British colonial Africa. I also compare taxation patterns, non-tax public revenue sources, government expenditure and investment policies and practices between the two colonies of Angola and Mozambique. My comparisons involve questions regarding the per capita amount of revenue, the observed expenditure priorities in absolute and relative terms and the changing foci of colonial investment programs. This international perspective allows me to assess how ‘extractive’, ‘minimalist’ or ‘developmental’ colonial policies in Mozambique and Angola were in different phases of Portuguese rule.

    Chapter 2 provides an overview of the fiscal policies and practices in Portuguese Mozambique and Angola from the 1850s to 1970s. It discusses the constraints to fiscal centralization and unification and shows how colonial investments prioritized security, administration and infrastructure over welfare services. It took a long time before the colonial states consolidated their power in Portuguese Africa. Local African leaders employed diverse strategies from resistance to cooperation to survive and maintain their local power, while concession companies controlled certain regions. As a result, these zones remained out of the supervision of the colonial state apparatus, especially during the early colonial era (1890s-1920s). This led to less centralization in decision-making and tax management. Fiscal modernization, including the capacity of the state to fund larger development projects, was also curbed by the elimination of long-term debt and the dogma of budget balance, which were core principles of Salazar’s authoritarian regime (1932-1968). Public revenues that were not allocated to military forces and administration, went mainly into infrastructural projects that facilitated imperial trade. Finally, there was no representative government to ensure legitimacy and tax compliance, neither in the metropole nor in the colonies. Portuguese Africa passed from peasant or feudalist societies to capitalist production, without developing modern political and fiscal institutions.

    Chapter 3 presents a case of colonial state formation without integration. It builds on Samir Amin’s (1972) division of the African continent into three “macro-regions of colonial influence” with distinct socio-economic systems and labour practices: Africa of the colonial trade or peasant economy, Africa of the concession-owning companies, and Africa of the labour reserves. I claim that Mozambique incorporated all three different “macro-regions” in a single colony (north-center-south). Different labour systems operated in the three geographic zones since early colonization, and these differences were maintained under colonial rule, also for the purpose of tax collection. The empirical analysis demonstrated that the south, which operated as a labour reserve for the mines of South Africa, had significantly higher tax capacity than the peasant and concession economies in the north and centre, and this pattern persisted over time. Colonial rule did not alter the conditions underlying fiscal inequality between the three zones. Instead, the colonial policies and practices concerning administration, taxation, and most importantly labour, reinforced the regional differences. Over the early decades (1890s-1930s), the colonial state delegated administrative tasks to concession companies in central and northern Mozambique and until as late as 1960 used forced labour schemes. In parallel, in southern Mozambique the colonial state institutionalized labour migration to the mines in South Africa and taxed migrant incomes.

    Chapter 4 focuses on the high militarization of Portuguese Africa. Specifically, it presents the results of a thorough comparison of military capacity building in Portuguese and British Africa from 1850 to 1940. It tests the hypothesis that Portugal, as an imperial “jackal” and financially weaker metropole, had to make relatively large investments in the securitization of its colonies in order to establish an internal monopoly on violence as well as to confront external threats from imperial “lions”, such as Britain. It shows that heavy military expenses in Portuguese Africa hampered long-term welfare investments. Also, organisation of colonial armies and forced labour schemes were interconnected. The colonial governments in Angola and Mozambique used private companies and local chiefs as intermediaries in military recruitment and contractual conditions were inclined to remain a dead letter.

    Chapter 5 explores the political economy of railway construction in Portuguese Africa, thus the involvement of colonial, indigenous and foreign (e.g. British) actors with different interests. It shows that in some cases the colonial governments and the metropole succeeded to attract private investors. When mineral exploitation was at stake, capitalists stepped in more easily. The colonial governments, however, had a broader agenda: they aimed at effectively occupying hinterland, creating new settler communities and increasing consent of the governed. By the 1930s, infrastructures were still concentrated around urban areas populated by considerable shares of white settlers, neglecting the remote rural areas inhabited by the vast majority of native Africans. After Salazar rose to power in Portugal, the states took over the operation of most railway lines in the two colonies and funded them either out of their ordinary colonial budgets or via loans usually raised in the metropole. Railways, however, were expensive investments. I argue that in both colonies the construction of the lines relied heavily on indigenous African labourers forcibly recruited. Africans also paid hut and poll taxes to finance infrastructural projects (or service debts). Especially in Mozambique, native taxation was a crucial source of revenue, while Angola could rely more on private capital and indirect taxes on exports.

    From the empirical evidence presented in this thesis, I draw the conclusion that Portugal widely used coercive institutions to enforce law in its African colonies, exactly because it was weaker than the other metropolitan powers in economic and diplomatic terms. The early colonial era is characterized by a combination of minimalist and extractive fiscal regimes in Portuguese Mozambique and Angola, that aimed at either securing order at minimum cost or at extracting resources via native taxation and forced labour; while the late colonial era is indicated by an incomplete transition from fiscal minimalism to a developmental agenda, that was actually undermined by the very means of development. The empirical evidence demonstrated that Portuguese colonialism in Africa was exceptional in the sense that a weak metropolitan power managed to sustain its authority as late as the 1970s, by building minimalist and extractive fiscal states that did not develop into welfare states even during the global post-war boom. The colonial states of Mozambique and Angola - despite their differences driven by local conditions - were both based on extreme systems of securitization and an exceptionally heavy tax burden, especially due to a continuing reliance on (direct) native taxation and forced labour.

    Conservación de suelos y aguas
    Lince Salazar, Luz Adriana ; Castra Quintero, Andrés Felipe ; Castaño Castaño, Wadi Andrey ; Bedoya Rojas, Mónica María ; Wolters, W. ; Miguel Ayala, L. - \ 2018
    Bogota : APC Columbia - ISBN 9789588490281 - 148
    Apparent ileal digestibility of Maillard reaction products in growing pigs
    Salazar-Villanea, Sergio ; Butré, Claire I. ; Wierenga, Peter A. ; Bruininx, Erik M.A.M. ; Gruppen, Harry ; Hendriks, Wouter H. ; Poel, Antonius F.B. van der - \ 2018
    PLoS ONE 13 (2018)7. - ISSN 1932-6203

    The absorption of Maillard reaction products (MRP) from dietary origin has been linked to the occurrence of chronic diseases. The aim of the present study was to determine the effects of toasting time of rapeseed meal (RSM) and the processing method of the diets (pelleting and extrusion) that included RSM on the apparent ileal digestibility (AID) of total lysine, fructosyl-lysine (FL), carboxymethyl-lysine (CML), carboxyethyl-lysine (CEL), lanthionine (LAN) and lysinoalanine (LAL) in growing pigs. The study consisted of a 2×3 factorial design with toasting time of RSM (60, 120 min) and diet processing method (mash, pelleted, extruded) as factors. Fifty growing pigs were individually fed one of the experimental diets for 4.5 consecutive days. Following euthanasia, samples of digesta were collected from the terminal 1.5 m of the small intestine. Increasing the toasting time of RSM increased the contents of FL, CML and CEL, whereas the additional effects of the diet processing methods were relatively small. Lysinoalanine and lanthionine were not detected in the diets; therefore, digestibility of these compounds could not be determined. The contents of FL, CML and CEL in the ileal chyme were positively correlated to their contents in the diets. The AID of the MRP from thermally-treated RSM were overall low and were not related to their contents in the diets. The AID of FL ranged between -8.5 and 19.1%, whilst AID of CML and CEL ranged from -0.2 to 18.3 and 3.6 to 30%, respectively. In conclusion, thermal treatments have clear effects on the contents of MRP in the diets. These compounds have relatively low digestibility in growing pigs.

    Apparent ileal digestibility of Maillard reaction products in growing pigs
    Salazar Villanea, S. - \ 2018
    digestibility - Maillard reaction - pigs
    Data used for the calculation of apparent digestibility values of Maillard reaction products for each experimental unit
    Integrative analysis of gut microbiota composition, host colonic gene expression and intraluminal metabolites in aging C57BL/6J mice
    Lugt, Benthe van der; Rusli, Fenni ; Lute, Carolien ; Lamprakis, Andreas ; Salazar, Ethel ; Boekschoten, Mark V. ; Hooiveld, Guido J. ; Müller, Michael ; Vervoort, Jacques ; Kersten, Sander ; Belzer, Clara ; Kok, Dieuwertje E.G. ; Steegenga, Wilma T. - \ 2018
    Aging-US 10 (2018)5. - ISSN 1945-4589 - p. 930 - 950.
    Aging - Colonic gene expression - Gut microbiota - Host-microbe interactions - Metabolites

    The aging process is associated with diminished colonic health. In this study, we applied an integrative approach to reveal potential interactions between determinants of colonic health in aging C57BL/6J mice. Analysis of gut microbiota composition revealed an enrichment of various potential pathobionts, including Desulfovibrio spp., and a decline of the health-promoting Akkermansia spp. and Lactobacillus spp. during aging. Intraluminal concentrations of various metabolites varied between ages and we found evidence for an increased gut permeability at higher age. Colonic gene expression analysis suggested that during the early phase of aging (between 6 and 12 months), expression of genes involved in epithelial-to-mesenchymal transition and (re)organization of the extracellular matrix were increased. Differential expression of these genes was strongly correlated with Bifidobacterium spp. During the later phase of aging (between 12 and 28 months), gene expression profiles pointed towards a diminished antimicrobial defense and were correlated with an uncultured Gastranaerophilales spp. This study demonstrates that aging is associated with pronounced changes in gut microbiota composition and colonic gene expression. Furthermore, the strong correlations between specific bacterial genera and host gene expression may imply that orchestrated interactions take place in the vicinity of the colonic wall and potentially mediate colonic health during aging.

    Pelleting and extrusion can ameliorate negative effects of toasting of rapeseed meal on protein digestibility in growing pigs
    Salazar-Villanea, S. ; Bruininx, E.M.A.M. ; Gruppen, H. ; Hendriks, W.H. ; Carré, P. ; Quinsac, A. ; Poel, A.F.B. van der - \ 2018
    Animal 12 (2018)5. - ISSN 1751-7311 - p. 950 - 958.
    digestibility - extrusion - growing pigs - pelleting - rapeseed meal
    Toasting time (TT) of rapeseed meal (RSM), the diet processing (DP) method and the interaction between both on the apparent CP digestion along the gastrointestinal tract and the apparent ileal digestibility (AID) of amino acids of growing pigs were investigated. The experiment consisted of a 3×3 factorial design of TT of RSM (0, 60 and 120 min) and DP method (mash, pelleting and extrusion). In total, 81 boars with a starting BW of 20 kg were euthanized 4 h after their last feeding. The gastrointestinal tract was dissected and the small intestine divided in three sections of similar length. Samples were collected from the stomach, 1.5 m from the ends of each of the three sections of the small intestine, and the rectum. The apparent digestibility (AD) of CP for each of the small intestine sections was used to calculate the rate of CP digestion. Increasing the TT of RSM resulted in lower protein solubility, lower lysine/reactive lysine contents and higher protein denaturation, indicative of the occurrence of protein aggregation and Maillard reactions. There were significant effects (P⩽0.01) of TT on the AD of CP in the different sections of the gastrointestinal tract. The rate of CP digestion of the 0 min toasted RSM diets was 23% and 35% higher than that of the 60 and 120 min toasted RSM diets, respectively. There was a significant interaction (P=0.04) between TT and DP for the AID of CP. Although pelleting of the 0 and 60 min toasted RSM diets did not change the AID of CP with respect to the mash diets, pelleting of the 120 min toasted RSM diet increased the AID of CP by 9.3% units. Extrusion increased the AID of CP of the 0 and 60 min toasted RSM diets by 3.4% and 4.3% units with respect to the mash diets, whereas extrusion of the 120 min toasted RSM diet increased the AID of CP by 6.9% units. Similar positive effects of pelleting and extrusion were obtained for the AID of lysine and reactive lysine, especially in the diets with higher TT. In conclusion, processing (pelleting and extrusion) of RSM containing diets can ameliorate the negative effects of RSM toasting on protein and amino acid digestibility; these effects were larger for the RSM toasted for longer times.
    These baby worms are good news for future Mars settlers, New experiment suggests worms could thrive in Martian soil.
    Wamelink, Wieger - \ 2017

    Onderzoek van Wieger Wamelink wordt aangehaald

    Effect of selection methods on seed potato quality
    Gunadi, N. ; Pronk, A.A. ; Karjadi, A.K. ; Prabaningrum, L. ; Moekasan, T.K. - \ 2017
    Wageningen : Wageningen Plant Research (vegIMPACT report 37) - 23
    Potato is one of the most important crops in the world. Although it ranks fourth after rice, wheat and maize, the major food crops in the world, either in production or in the economic value, in terms of energy and protein production per hectare and per unit of time, the potato ranks first which is significantly above cereals, pulses and cassava (CIP 1984). In many countries potato is considered a vegetable, but the interest for potato as staple crop increases especially in developing countries, including Indonesia which is the largest potato producer in Southeast Asia. At present, the potato areas in Indonesia varies between 60,000 and 70,000 ha with a total production of about 1.2 - 1.3 million tons per year. The potato has been considered a priority crop in the strategic plan of research and development program of the Indonesian Agency for Agricultural Research Development (IAARD) in the last 30 years because of its potential as alternative carbohydrate source in food diversification and for export markets. The potato originally comes from the cool tropical highlands of the Andes in South America (Horton and Anderson 1992) and therefore the potatoes in Indonesia are mainly grown in the highland areas (> 1,000 m). The main potato variety in Indonesia since the 1980’s is Granola, which covers 80 to 85% of the potato area. The moderate resistance of Granola to PLRV and PVY appear to have contributed in making it a successful variety in Indonesia (Chujoy 1995). Seed is the most costly component of potato production, and potato profitability often depends on access to quality seed. Seed accounts for 30-40% of the total costs of potato production in Indonesia (De Putter, et al. 2014; Pronk, et al. 2017a; Van den Brink, et al. 2015). High quality seed is relatively expensive and is not affordable by most farmers. Therefore, most potato farmers often use potato seed tubers saved from their previous crops. Small tubers are usually selected and saved for seeds for planting in the following season. This unhygienic practice results in carrying over diseases (e.g. viruses and bacteria contained in the small seed tubers) with the result that yields decrease over time. Farmers will need to buy seed tubers from other farmers or traders when their own seed stock has degenerated due to build up diseases. The degeneration of seed stock depends on the seed selection and also on the variety grown. Varieties differ in levels of resistance to virus infections and virus particle multiplication within the plant (Salazar 1996). One method to reduce the degeneration rate is through so-called positive selection (Gildemacher, et al. 2007). In this method, the best potato plants in a field are marked before crop senescence and they serve as mother plants for seed potatoes used in the following season. Positive selection in Kenya gave an average yield increase in farmer-managed trials of 34%, corresponding to a 284 € increase in profit per hectare at an additional production cost of only 6 € /ha (Gildemacher, et al. 2011). Within the vegIMPACT program demonstration trials have been carried out to show farmers the potential benefits of positive selection on the seed potato quality in the subsequent season. The demonstrations showed potato farmers the importance of plant selection in one planting season in order to obtain good quality seeds in the following planting season. Positive selection is a technique to maintain good quality seeds by reducing the degeneration rate of farm saved seed. This technique potentially reduces the costs for the most costly input, i.e. seed potatoes, in potato production.
    Effects of Toasting Time on Digestive Hydrolysis of Soluble and Insoluble 00-Rapeseed Meal Proteins
    Salazar-Villanea, Sergio ; Bruininx, Erik M.A.M. ; Gruppen, Harry ; Carré, Patrick ; Quinsac, Alain ; Poel, Thomas van der - \ 2017
    Journal of the American Oil Chemists Society 94 (2017)4. - ISSN 0003-021X - p. 619 - 630.
    Hydrolysis rate - Maillard - Protein solubility - Rapeseed meal - Toasting
    Thermal damage to proteins can reduce their nutritional value. The effects of toasting time on the kinetics of hydrolysis, the resulting molecular weight distribution of 00-rapeseed meal (RSM) and the soluble and insoluble protein fractions separated from the RSM were studied. Hydrolysis was performed with pancreatic proteases to represent in vitro protein digestibility. Increasing the toasting time of RSM linearly decreased the rate of protein hydrolysis of RSM and the insoluble protein fractions. The extent of hydrolysis was, on average, 44% higher for the insoluble compared with the soluble protein fraction. In contrast, the rate of protein hydrolysis of the soluble protein fraction was 3–9-fold higher than that of the insoluble protein fraction. The rate of hydrolysis of the insoluble protein fraction linearly decreased by more than 60% when comparing the untoasted to the 120 min toasted RSM. Increasing the toasting time elicited the formation of Maillard reaction products (furosine, Nε-carboxymethyl-lysine and Nε-carboxyethyl-lysine) and disulfide bonds in the insoluble protein fraction, which is proposed to explain the reduction in the hydrolysis rate of this fraction. Overall, longer toasting times increased the size of the peptides resulting after hydrolysis of the RSM and the insoluble protein fraction. The hydrolysis kinetics of the soluble and insoluble protein fractions and the proportion of soluble:insoluble proteins in the RSM explain the reduction in the rate of protein hydrolysis observed in the RSM with increasing toasting time.
    Of proteins and processing: mechanisms of protein damage upon rapeseed processing and their effects on nutritional value
    Salazar Villanea, Sergio - \ 2017
    Wageningen University. Promotor(en): Wouter Hendriks; Harry Gruppen, co-promotor(en): Thomas van der Poel; E.M.A.M. Bruininx. - Wageningen : Wageningen University - ISBN 9789462579873 - 182
    animal nutrition - rapeseed - rapeseed protein - feed processing - proteins - digestion - pigs - diervoeding - raapzaad - raapzaadeiwit - voedermiddelbewerking - eiwitten - spijsvertering - varkens

    Hydrothermal processing is a common practice during the manufacture of protein-rich feed ingredients, such as rapeseed meal (RSM), and feeds. This processing step can induce physical and chemical changes to the proteins, thereby reducing the digestibility and utilization of crude protein (CP) and amino acids (AA). Whilst most literature has linked the chemical changes to the proteins with negative effects on protein digestibility, the effects of the physical changes of the protein conformation have not been considered simultaneously. Hence, the aim of this thesis was to provide further insight into the mechanisms of protein damage during ingredient/feed processing and their effects on protein hydrolysis/digestibility. In Chapter 2, the available literature on the physical changes that occur to vegetable proteins used in swine diets after processing was reviewed. Overall, hydrothermal processing increases the contents of intermolecular/intramolecular β-sheets and disulfide bonds, which were negatively correlated to protein digestibility. The correlations, however, were dependent on the type of protein analysed. When the physico-chemical changes in the proteins occur during processing of the ingredients, proteins usually become less responsive to further processing treatments. Rapeseed proteins were used as model, as this oilseed is hydrothermally processed during the oil extraction process and is further processed when incorporated in animal diets.

    Protein damage during production of rapeseed meal

    There is high variability in the nutritional value of commercial RSM. The variation is mainly due to the conditions used during the desolventization/toasting step. Therefore, the aim of the experiment in Chapter 3 was to characterize the secondary structure and chemical changes that occur during toasting of RSM and their effects on in vitro protein digestibility. A cold defatted RSM was toasted for 120 min with samples obtained every 20 min. Increasing the toasting time from 0 to 120 min increased protein denaturation by 3-fold and decreased protein solubility by 4-fold, lysine content by 23% and the reactive lysine content by 37%. The proportion of intermolecular β-sheets increased after the initial 20 min of toasting, but steadily decreased thereafter. The contrary was observed for the proportion of α-helices. The changes in the secondary structure of proteins were not correlated to the rest of the physical and chemical changes. Therefore, changes in the secondary structure of proteins cannot be considered good indicators of damage to proteins due to hydrothermal processing. The rate of protein hydrolysis decreased by 2-fold when toasting time was increased from 0 min to 120 min. The changes in protein solubility and lysine/reactive lysine contents were positively correlated to the rate of protein hydrolysis. Changes to the physical conformation of rapeseed proteins occur at faster rates during toasting compared to chemical changes.

    In Chapter 4, it was hypothesized that the decrease in the rate of protein hydrolysis with increasing toasting time was due to the reduction in protein solubility. In order to test this hypothesis, the soluble and insoluble protein fractions from each of the RSM studied in Chapter 3 were separated and hydrolysed. Hydrolysis kinetics and the molecular size distribution of the peptides resulting after hydrolysis were analysed. The extent of hydrolysis of the insoluble protein fraction was 44% higher than that of the soluble protein fraction. The rate of hydrolysis of the soluble protein fraction separated from the hydrothermally treated RSM was 3-9 fold higher than that of the insoluble protein fraction. In the insoluble fraction, formation of both disulfide bonds and Maillard reaction products (MRP) (fructosyl-lysine [FL], carboxymethyl-lysine [CML] and carboxyethyl-lysine [CEL]) was noticed, which explains the decrease in the rate of protein hydrolysis with longer toasting times. Overall, increasing the toasting time of the whole RSM and the insoluble protein fraction increased the size of the peptides resulting after enzymatic hydrolysis. A shift in the mechanism of protein hydrolysis from a more one-by-one type to a more zipper-type likely explained the correlations between the rate of hydrolysis and the molecular size distribution after hydrolysis. Protein solubility seems to be a key parameter for understanding the decrease in the rate of protein hydrolysis with increasing toasting time.

    The correlations between two in vitro protein digestibility methods and the standardised ileal digestibility in growing pigs of severe thermally-treated soybean and rapeseed meals were studied in Chapter 5. Soybean meal and RSM were toasted in the presence of lignosulfonate in order to induce severe thermal damage to the proteins. In vitro protein digestibility was analysed using the two-step enzymatic method (pepsin at pH 2.0 and pancreatin at pH 6.8) and the pH-STAT method. The standardised ileal digestibility values were obtained from a previous experiment, in which ileal-cannulated growing pigs were used. The degree of hydrolysis after 10 min was positively correlated (r = 0.95, P = 0.046) to the standardised ileal CP digestibility. The in vitro rate of protein hydrolysis using the pH-STAT method and CP digestibility using the two-step enzymatic method tended to be positively correlated to the standardised ileal digestibility of CP (r = 0.91, P = 0.09, for both in vitro methods). In conclusion, both in vitro methods might be used for the in vivo digestibility of severe thermally-treated ingredients.

    Effects of diet processing on protein digestibility of RSM with different extents of damage

    The processed ingredients (e.g. rapeseed meal) are mixed with other ingredients and processed further during the compound feed manufacturing process. The effects of the diet processing methods (e.g. pelleting and extrusion) on protein digestibility could depend on the extent of the damage of the ingredients used. The aim of Chapter 6 was to test the effects of toasting time of rapeseed meal, diet processing method and the interaction between both on protein digestion along the gastrointestinal tract and apparent/standardised ileal digestibility of CP and AA. Mash, pelleted and extruded diets were manufactured using either 0, 60 or 120 min toasted RSM as the only protein source, for a total of 9 different experimental diets. Whilst increasing the toasting time decreased the contents of lysine and reactive lysine in the diets, no effects were noticed after pelleting or extrusion of the diets compared to the mash. The mean particle size of the diets was reduced from 479 μm in the mash diets to 309 and 211 μm after pelleting and extrusion, respectively. A total of 81 growing boars were individually fed with one of the experimental diets. Following euthanasia, the small intestine was divided in 3 sections of equal length and the contents of the final 1.5 m of each small intestine section were sampled. The apparent CP digestibility for each section of the gastrointestinal tract was used to calculate the rate of CP digestion based on a second order equation. The rate of digestion was higher in the diets containing 0 min toasted RSM compared to the diets that contained 60 or 120 min toasted RSM. The diet processing method tended to affect the rate of protein digestion, with higher rates for the extruded > pelleted > mash diets. Significant effects of the interaction between toasting time and diet processing method were found on the apparent ileal CP digestibility. Whilst a lower apparent ileal CP digestibility was found in the 120 min toasted RSM mash diet compared to the 0 and 60 min toasted RSM mash diets, no differences were observed between the different toasting times in the pelleted and extruded diets. Similar significant interactions were noticed for the apparent ileal digestibility of some dispensable and indispensable AA (e.g. arginine, isoleucine, leucine, methionine, threonine, alanine, glycine, proline, serine). Pelleting of the 60 and 120 min toasted RSM diets increased the standardized ileal digestible CP content by 6 and 15%, respectively, compared to the 60 and 120 min toasted mash diets. Extrusion of the 0, 60 and 120 min toasted RSM diets increased the standardized ileal digestible CP content by 5, 9 and 12%, respectively, compared to the 0, 60 and 120 min toasted mash diets. Similar positive effects of pelleting and extrusion were obtained for the apparent ileal digestible contents of lysine and reactive lysine, especially for the diets that contained RSM toasted for longer times. In conclusion, the severe effects of protein damage during the production of RSM on protein digestibility can be (partially) ameliorated by processing of the diets.

    Processing of ingredients and diets can lead to the formation of early (e.g. FL) and advanced (e.g. CML and CEL) MRP. These MRP have been associated with common metabolic disorders, for example atherosclerosis. Absorption of dietary MRP has been previously estimated based on indirect measurements, such as concentrations in blood, urine and faeces, which could be biased by endogenous formation of MRP and deposition in tissues. Hence, the aim of Chapter 7 was to measure the apparent ileal digestibility of early (FL, determined as furosine after acid hydrolysis) and advanced (CML and CEL) MRP. The same diets and ileal digesta samples as in Chapter 6 were used in this study. The 0 min toasted RSM diets (mash, pelleted and extruded) were excluded from this study. Sucrose was added to these diets immediately before feeding in order to increase their feed intake, which could confound the determination of the apparent ileal digestibility of the MRP for these treatments. The content of FL was higher in the 120 min compared to the 60 min toasted RSM diets, whereas it was lower in the extruded diets compared to the pelleted and mash diets. The decrease in FL content after extrusion of the diets can probably be related to conversion of the early into advanced MRP, as the content of CML was higher in the extruded diets compared to the pelleted and mash diets. The contents of FL, CML and CEL were positively correlated to the contents of these compounds in the ileal chyme. The apparent ileal digestibility of FL, CML and CEL for the different diets ranged from -8.5 to 19.1%, -0.2 to 18.3% and 3.6 to 30%, respectively. In conclusion, the apparent ileal digestibility of the early and advanced MRP from thermally-treated RSM diets in growing pigs were overall low and did not seem to be related to the contents of these compounds in the diets.

    The results of this thesis indicate that the changes to the physical conformation of proteins during toasting of RSM occur at a faster rate than chemical changes. Both types of changes affect protein solubility, which is important in determining the rate of protein hydrolysis. It is suggested in this thesis that the rate of protein hydrolysis of hydrothermally-processed ingredients is probably the main contributing factor for the in vivo protein digestibility. This was demonstrated, as increasing the toasting time of RSM decreased the rate of CP digestion in growing pigs. The negative effects of longer toasting times on CP and AA digestibility, however, could be ameliorated by pelleting and extrusion of the diets. The positive effects of diet processing methods (pelleting and extrusion) on the digestibility of damaged proteins from thermally-treated ingredients should be taken into account in feed evaluation studies and formulation of practical diets.

    Processing of rapeseed meal: effects on protein hydrolysis and digestibility
    Salazar Villanea, Sergio - \ 2016
    Effect of toasting time on proteolysis of soluble and insoluble protein fractions of rapeseed meal
    Salazar Villanea, Sergio - \ 2016
    Effect of toasting time on proteolysis of soluble and insoluble protein fractions of rapeseed meal
    Salazar Villanea, S. ; Bruininx, E.M.A.M. ; Carré, P. ; Quinsac, A. ; Poel, A.F.B. van der - \ 2016
    In: Energy and protein metabolism. - Wageningen Academic Publishers (EAAP publication 137) - ISBN 9789086862863 - p. 279 - 280.
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