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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    Amylase increases energy and nutrient density of Super Cereal Plus porridge as prepared and accepted by Rwandan caregivers
    Broersen, Britt ; Sinamo, Sisay ; Nsabimana, Jules ; Mahamadou, Tanimoune ; Gatete, Edgar ; Prigge, Shane ; Hoan, Nguyen Van; Pee, Saskia de - \ 2019
    Maternal and Child Nutrition 15 (2019)2. - ISSN 1740-8695
    alpha-amylase - complementary feeding - energy density - porridge preparation - Rwanda - Super Cereal Plus

    Adding amylase to Super Cereal Plus (SC+A) improves energy and nutrient intake as porridge energy density reaches 1.0 kcal/g, meeting the recommended ≥0.8 kcal/g for prepared foods for young children. Caregiver response to SC+A in terms of adjusting porridge preparation using printed pictogram instructions was not yet investigated. The study assessed (a) porridge preparation by caregivers; (b) porridge energy density; (c) sensory porridge acceptability; and (d) understanding of preparation instructions. An 8-day follow-up intervention study was conducted amongst caregivers of children aged 6–23 months (n = 238) in Rwanda. Caregivers prepared porridge using SC+A whilst referring to printed pictogram instructions at the study site on Days 1 and 8 and received flour for preparation at home on Days 2–7. At the site, data were collected on porridge preparation procedures, energy density, consistency, acceptability, and interviews (n = 12), and focus group discussions (n = 6) were conducted. Mean porridge dry matter (DM) increased from 21.3 ± 4.4% (Day 1) to 25.1 ± 4.8% (Day 8; p < 0.0005). Flour and water were mixed before cooking by 95% of the participants, as per printed instructions. Sensory porridge acceptability was high, and the printed instructions enabled caregivers to prepare an accepted and energy dense porridge. The preferred water/flour volume ratio was 2.5 instead of 3. In conclusion, Rwandan caregivers prepared well-accepted SC+A porridges with a preferred consistency and mean DM content of 25.1% (1.0 kcal/g), after 1 week practicing at home. This supports introducing SC+A with the tested instructions at scale.

    Pearling barley to alter the composition of the raw material before brewing
    Donkelaar, L.H.G. van; Noordman, T.R. ; Boom, R.M. ; Goot, A.J. van der - \ 2015
    Journal of Food Engineering 150 (2015). - ISSN 0260-8774 - p. 44 - 49.
    hull-less barley - liquid-chromatography - phenolic-compounds - hordeum-vulgare - rich fractions - alpha-amylase - malt extracts - dietary fiber - quality - components
    Partly replacing malt with unmalted barley is a trend in brewing. The use of unmalted barley, however, leads to issues such as haze and high mash viscosity, due to its higher content of undesired components. Pearling, an abrasive method to remove the outer layers of the barley kernels has been shown to reduce the content of insoluble fibre, ash, protein and polyphenols; the ß-amylase activity and starch content of the remaining kernel were hardly affected. Removing the outer 5% of the kernel, for example, results in a 15% reduction of insoluble arabinoxylans, 23% of the insoluble fibre content and 25% of the water holding capacity of the non-starch components. It also reduces the ash content by 19% and the polyphenol content by 11%, but only 0.20% of the starch is pearled off. A relation was found between the insoluble fibre content and the water holding capacity of a fraction. Lower fibre content reduces the water holding capacity and thus the volume of the spent grains, which implies that less wort and sugar are lost during filtration. In addition, that the bran fraction remains dry, implies a reduction in energy required to dry the spent grains.
    Salivary lipase and a-amylase activities are higher in overweight than in normal weight subjects: Influences on dietary beharior
    Mennella, I. ; Fogliano, V. ; Vitaglione, P. - \ 2014
    Food Research International 66 (2014). - ISSN 0963-9969 - p. 463 - 468.
    alpha-amylase - food-consumption - oral-sensitivity - lingual lipase - fat perception - taste - questionnaire - responses - humans - women
    Mounting evidence shows that hedonic eating, leading to overeating just for pleasure, can be driven by oro-sensory factors through the activation of reward processing and learning in the brain. Foods rich in sugars and fats are potent rewards and saliva composition influences oral taste, texture and aroma perception. A role for salivary a-amylase and lipase in the gustatory system and a link between salivary a-amylase activity and dietary habits were recently hypothesized. The objective of this study was to verify the relationship among salivary lipase and a-amylase activities as well as zinc concentration with food preference and choice of people with different body mass indices. Forty-two (23 normal weight and 19 overweight) healthy subjects participated in the study. Data showed that a-amylase and lipase were 1.8 and 2.4 folds higher in overweight than in normal weight subjects, respectively. On the other hand, overweight subjects showed a 33% reduced salivary zinc concentration compared to normal weight subjects. Only lipase activity positively correlated with individual preference for high-fat foods and with fat content of the diets. All in all data suggested that high salivary lipase activity in overweight subjects could be an adaptive response to the low fat-taste perception related to the reduced zinc concentration. It cannot be ruled out that other factors but diet might influence salivary a-amylase activity in overweight subjects.
    Individually Modified Saliva Delivery Changes the Perceived Intensity of Saltiness and Sourness
    Heinzerling, C.I. ; Stieger, M.A. ; Bult, J.H.F. ; Smit, B. - \ 2011
    Chemosensory Perception 4 (2011)4. - ISSN 1936-5802 - p. 145 - 153.
    flow-rate - taste sensitivity - alpha-amylase - perception - secretion - stimuli - texture - starch - acids - ph
    Individuals vary largely in their salivary flow and composition, and given the importance of saliva on perception of taste, this might influence how the tastant stimuli are perceived. We therefore hypothesise that altering the individual salivary flow rates has an impact on the perceived taste intensity. In this study, we investigated the role of saliva amount on the perceived taste intensity by excluding parotid saliva and adding artificial saliva close to the parotid duct at preset flow rates. Significant decreases in perception with increasing salivary flow rates were observed for citric acid and sodium chloride. This can partially be explained by a dilution effect which is in line with previous studies on detectable concentration differences. However, since the bitterness and sweetness remained unaffected by the salivary flow conditions and the dilution effect was comparable to that of saltiness, further explanation is needed. Furthermore, we investigated whether the suppression of taste intensity in binary mixtures (taste–taste interactions) could possibly be caused by the increased salivary flow rate induced by an additional taste attribute. The results show, however, that suppression of taste intensity in binary mixtures was not affected by the rate of salivation. This was more likely to be explained by psychophysics
    Relating the effect of saliva-induced emulsion flocculation on rheological properties and retention on the tongue surface with sensory perception
    Vingerhoeds, M.H. ; Silletti, E. ; Groot, J. de; Schipper, R.G. ; Aken, G.A. van - \ 2009
    Food Hydrocolloids 23 (2009)3. - ISSN 0268-005X - p. 773 - 785.
    oil-in-water - custard desserts - alpha-amylase - oral texture - creaminess - protein - tannin - model - viscosity - lysozyme
    Perception of food emulsions can often not be directly related to the structure of the products before consumption. Taking into account the changing product structure upon oral processing might increase understanding of the relation between perception and product properties. This study aims to gain insight in the effect of saliva-induced flocculation on perception of emulsions at neutral pH. Whey protein (WPI)-stabilized emulsions flocculating in a reversible manner with saliva were compared with lysozyme-stabilized emulsions that irreversible flocculate with saliva. The main emulsion variables, besides the emulsifying protein, were oil content (2.5% oil vs 10% oil), and the effect of emulsion thickening with guar gum (at 10% oil). To relate perception to processes occurring in the oral cavity, the emulsions were characterized before and after oral processing with respect to morphology and rheological properties (viscosity, storage and loss moduli). In addition, insight in retention of emulsion droplets on the tongue surface was obtained by measuring emulsifier and oil content in tongue swabs. Saliva-induced emulsion flocculation clearly shows a large effect on perception of the here studied emulsions. WPI-stabilized emulsions showed little retention on the tongue surface and perception was characterized by creaminess, fattiness and thickness. Guar gum thickening further increased perception of these attributes. On the other hand, for lysozyme-stabilized emulsions perception was largely related to attributes like dryness, roughness and astringency. In addition, a large viscosity increase upon oral processing and clear retention of emulsion droplets on the tongue surface was observed. Guar gum thickening decreased the effects of irreversible flocculation, likely because of its lubricating properties and increased viscosity. Although the amount of mucins recovered from the tongue surface was unaffected by orally processing of lysozyme-stabilized emulsions, the sensory characteristics of these emulsions reminds one of astringency perception of e.g. tannins that precipitate salivary proteins.
    Modelling oral conditions and thickness perception of a starch product
    Heinzerling, C.I. ; Smit, G. ; Dransfield, E. - \ 2008
    International Dairy Journal 18 (2008)8. - ISSN 0958-6946 - p. 867 - 873.
    alpha-amylase - flavor perception - custard desserts - saliva flow - texture - viscosity - release - creaminess - behavior - taste
    Food components stimulate salivation, and the flow and composition of the saliva also affect the perception of the food product. In starch-containing foods, salivary ¿-amylase breaks down the starch and this may cause thinning in semi-solid foods. The aims were to determine the importance of salivary composition to perceived thickness. Vanilla custard was assessed for taste intensity, creaminess and thickness. To extend the range of saliva composition and flow, an ¿-amylase inhibitor was added to the samples at different concentrations and the pH of the samples was lowered by adding citric acid. From each collected spat-out bolus, temperature, pH, dilution factor and ¿-amylase activity were measured. Addition of amylase inhibitor reduced saliva ¿-amylase activity and increased perceived thickness and creaminess. Acidification increased mechanical thickness prior to testing and perceived thickness but did not reduce the in situ ¿-amylase activity because the saliva stimulated by acidified custards was also more concentrated in ¿-amylase. Alpha-amylase activity varied widely among subjects and so decreasing oral ¿-amylase activity would not guarantee an increase in perceived thickness and creaminess of starch-based foods.
    How emulsions composition and structure affect sensory perception of low-viscosity model emulsions
    Vingerhoeds, M.H. ; Wijk, R.A. de; Zoet, F.D. ; Nixdorf, R.R. ; Aken, G.A. van - \ 2008
    Food Hydrocolloids 22 (2008)4. - ISSN 0268-005X - p. 631 - 646.
    oil-in-water - perceived oral texture - cream style dressings - 20 aroma compounds - custard desserts - alpha-amylase - saliva - release - flavor - mouth
    The oral residence time of low-viscosity emulsions, like milk, is relatively short. Despite this short residence time, people can easily perceive differences between these emulsions. Our research is dedicated to unravel the oral behaviour of emulsions in relation to sensory perception. The aim of this study is to thoroughly evaluate the sensory perception of low-viscosity emulsions in relation to a range of emulsion engineering control parameters. A standard, 10% sunflower containing emulsion stabilised by whey protein isolate was modified with respect to fat type (sunflower oil, palm fat and milk fat), fat content (0¿40%), droplet size and addition of guar gum or particles. Fat-related attributes, like creaminess, fattiness, satiation and coating after feel were affected by fat type, fat content and guar gum addition. Increasing fat content and/or replacing sunflower oil by solid fat, which melts around body temperature, were the most effective ways to increase fat and creamy perception of low-viscosity emulsions. Control of emulsion perception by varying droplet size in the range from 0.5 to 6 ¿m did not affect fat-related attributes.
    Food colloids under oral conditions
    Aken, G.A. van; Vingerhoeds, M.H. ; Hoog, E.H.A. de - \ 2007
    Current Opinion in Colloid and Interface Science 12 (2007)39572. - ISSN 1359-0294 - p. 251 - 262.
    transmission electron-microscopy - human saliva proteome - proline-rich protein - flavor release - rheological properties - emulsion flocculation - tannin interactions - texture-perception - sensory perception - alpha-amylase
    Recent studies have made clear that structural and rheological changes of soft foods when they are processed in the mouth play a crucial role in sensory perception. This applies to soft solid products (fracturing behaviour and exudation of fluid) as well as more liquid food systems (breakdown of starch by salivary amylase, saliva-induced droplet aggregation, deposition and retention of food material on the tongue surface).
    Fatty versus creamy sensations for custard desserts, white sauces and mayonnaises
    Wijk, R.A. de; Prinz, J.F. - \ 2007
    Food Quality and Preference 18 (2007)4. - ISSN 0950-3293 - p. 641 - 650.
    perceived oral texture - flavor release - alpha-amylase - salivary flow - perception - astringency - foods - taste - ph
    Perceived fattiness and creaminess plus other texture and flavor attributes were assessed for a group of vanilla custard desserts, white sauces, and mayonnaises that differed widely in ingredients, fat content (0¿72%), and consumption temperatures. In addition, the foods were measured instrumentally with regard to their lubricative properties, infra-red reflectance and turbidity of rinse water. Despite the variety in foods, fat content showed strong correlations with the instrumental measures, and perceived fattiness, and weaker but still significant correlations with creamy mouth and after-feel. Friction and infra-red reflectance demonstrated that properties of the surface of the oral food bolus are important for fat-related attributes via mechanisms such as lubrication. Turbidity of rinse water suggested that properties of the bulk of the food bolus are important as well. Creamy after-feel related less well to instrumental measures, fat content and other sensory attributes suggesting that the creaminess of oral coatings is not only affected by fat but also by other unknown properties
    Process development for gelatinisation and enzymatic hydrolysis of starch at high concentrations
    Baks, T. - \ 2007
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Anja Janssen. - [S.l.] : s.n. - ISBN 9789085046943 - 208
    zetmeel - verwerking - hydrolyse - alfa-amylase - starch - processing - hydrolysis - alpha-amylase - cum laude
    cum laude graduation (with distinction) Enzymatic hydrolysis of starch is encountered in day-to-day life for instance in the dishwasher during removal of stains with detergents or in our mouth during chewing of starch-based foods in the presence of saliva. The reaction is also important for the (food) industry, for example for the production of beer or bio-ethanol. In industry, it is usually preceded by gelatinisation to make the starch molecules available for the enzymes. Both gelatinisation and hydrolysis are usually carried out at a starch concentrations of 30 weight-%. Increasing the starch concentration during these processes can lead to a higher productivity, lower energy consumption, lower use of water and a higher enzyme stability. However, the drawback is that the gelatinisation temperature and the viscosity increase at these conditions. By using the proper process equipment, it is possible to overcome these drawbacks and to perform the gelatinisation and hydrolysis at high starch concentrations leading to the advantages mentioned above. The purpose of this study was therefore to develop a process for gelatinisation and enzymatic hydrolysis of wheat starch at high starch concentrations (more than 40 weight-%). Besides the development of such a process, analysis methods were developed to measure the main process parameters at these conditions.
    The effect of saliva composition on texture perception of semi-solids
    Engelen, L. ; Keybus, P.A.M. van den; Wijk, R.A. de; Veerman, E.C.I. ; Nieuw Amerongen, A.V. ; Bosman, F. ; Prinz, J.F. ; Bilt, A. van der - \ 2007
    Archives of Oral Biology 52 (2007)6. - ISSN 0003-9969 - p. 518 - 525.
    human glandular salivas - custard desserts - whole saliva - alpha-amylase - flavor - flow - mouthfeel - mucins - foods - attributes
    Saliva is expected to be of significance for the perception of food stimuli in the mouth. Mixing the food with saliva, including breakdown and dilution, is considered to be of large importance for semi-solids as these products are masticated without chewing. It is known that there are large variations in composition of saliva originating from different glands and different subjects. In this study we investigated how variations in salivary characteristics affect sensory perception. Eighteen trained subjects participated in the study. Saliva was collected at rest and during three types of stimulation (odour, parafilm chewing and citric acid), and flow rates were determined. The collected saliva was analyzed for protein concentration, buffer capacity, mucin level and ¿-amylase activity. The salivary components measured in this study varied considerably among subjects, but also within subjects as a result of different means of stimulation. Variations in salivary components were correlated with sensory perception of a number of flavour, mouth feel and after feel attributes in the semi-solids mayonnaise and custard dessert. Total protein concentration and ¿-amylase activity were observed to correlate most strongly with texture perception.
    Relations between rheological properties, saliva-induced structure breakdown and sensory texture attributes of custards
    Janssen, A.M. ; Terpstra, M.E.J. ; Wijk, R.A. de; Prinz, J.F. - \ 2007
    Journal of Texture Studies 38 (2007)1. - ISSN 0022-4901 - p. 42 - 69.
    perceived oral texture - semisolid foods - flow properties - alpha-amylase - fluid foods - perception - model - viscosity - mayonnaise - creaminess
    The relevance of initial rheological properties and mechanical and enzymatic structure breakdown in determining selected sensory texture attributes of custards was studied. The so-called structure breakdown cell was used to characterize saliva-induced breakdown, i.e., by monitoring digestion of starch by amylase from saliva. Based on rheological parameters, some attributes could be predicted well, while others more poorly or were not predicted. Predictable attributes were primarily determined by bulk properties; poorly and nonpredictable attributes originated from properties of the outer low-viscosity surface layers or were not related to rheological properties. Both mechanical and enzymatic breakdown were important for creaminess, thickness and melting. Enzymatic breakdown was the dominant mechanism involved in the perception of fattiness, roughness and stickiness but not heterogeneity. Creaminess was the only attribute that was also determined by initial rheological properties and mechanical and enzymatic breakdown. Custards displaying high creaminess ratings had high initial stiffness, the structure broke down at low stress and enzymatic breakdown was slow. Microstructural organization of starch plays a dominating role in defining rheological and breakdown behavior of custards and in this way determines creaminess to a high extent.
    Heterologous protein production in the yeast Kluyveromyces lactis
    Ooyen, A.J.J. van; Dekker, P. ; Huang, M. ; Olsthoorn, M.M.A. ; Jacobs, D.I. ; Colussi, P.A. ; Taron, C.H. - \ 2006
    FEMS Yeast Research 6 (2006)3. - ISSN 1567-1356 - p. 381 - 392.
    human serum-albumin - saccharomyces-cerevisiae - molecular-cloning - yarrowia-lipolytica - expression systems - beta-galactosidase - engineered yeasts - secreted proteins - gene-expression - alpha-amylase
    Kluyveromyces lactis is both scientifically and biotechnologically one of the most important non-Saccharomyces yeasts. Its biotechnological significance builds on its history of safe use in the food industry and its well-known ability to produce enzymes like lactase and bovine chymosin on an industrial scale. In this article, we review the various strains, genetic techniques and molecular tools currently available for the use of K. lactis as a host for protein expression. Additionally, we present data illustrating the recent use of proteomics studies to identify cellular bottlenecks that impede heterologous protein expression.
    Effects of added fluids on the perception of solid food
    Pereira, L.J. ; Wijk, R.A. de; Gaviao, M.B.D. ; Bilt, A. van der - \ 2006
    Physiology and Behavior 88 (2006)4-5. - ISSN 0031-9384 - p. 538 - 544.
    alpha-amylase - salivary secretion - human mastication - texture - flow - behavior - flavor - model
    The production of sufficient saliva is indispensable for good chewing. Recent research has demonstrated that salivary flow rate has little influence on the swallowing threshold. We examined the hypothesis that adding fluid to a food will influence the chewing process. Twenty healthy subjects chewed on melba toast, breakfast cake, carrot, peanut and Gouda cheese. In addition they chewed on these foods after we added different volumes of tap water or a solution of ¿-amylase. We measured jaw muscle activity and the number of cycles until swallowing. Furthermore, we obtained visual analogue scale (VAS) scores for texture and sound attributes for all foods and fluid conditions. The additional fluids significantly lowered muscle activity and swallowing threshold for melba, cake and peanut. The effect of ¿-amylase in the solutions was rather limited. Doubling the volume of tap water had a larger effect. Several texture and sound attributes of melba, cake and peanut were also significantly affected by the additional fluids. For melba, cake, and peanut we observed significant correlations between the physiology parameters and several attributes for the various fluid conditions. This indicates that the added fluid affects both the physiology (muscle activity and number of cycles) and the sensory perception of a number of texture and sound attributes. Adding fluid facilitates the chewing of dry foods (melba, cake), but does not influence the chewing of fatty (cheese) and wet products (carrot)
    Effects of germination on the activities of amylases and phenolic enzymes in sorghum varieties grouped according to food end-use properties
    Dicko, M.H. ; Gruppen, H. ; Zouzouho, O.C. ; Traore, A.S. ; Berkel, W.J.H. van; Voragen, A.G.J. - \ 2006
    Journal of the Science of Food and Agriculture 86 (2006)6. - ISSN 0022-5142 - p. 953 - 963.
    phenylalanine ammonia-lyase - polyphenol oxidase - beta-amylase - cyanide contents - alpha-amylase - burkina-faso - peroxidase - cultivars - malt - viscosity
    Fifty sorghum varieties were screened to determine the effects of germination on levels of starch, -amylase, -amylase, phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO). Germination decreased starch content, with amylose being more degraded than amylopectin. In germinated grain, -amylase activity increased several-fold in all varieties, whereas -amylase activity did not increase uniformly and even decreased in some varieties. Activity of the key enzyme in phenolic biosynthesis, PAL, was detected in only half of the varieties before germination but in all of them after germination. PPO was not activated in germinated sorghum grains, whereas POX activity increased up to tenfold in some varieties. Zymography revealed that germination induced de novo synthesis of several POX isoenzymes, among which an anionic POX isoenzyme (pI 3.1) was ubiquitously present. Amylase and phenolic enzyme activities could be correlated with grain and plant agronomic characteristics. The use of sorghum varieties for local dishes such as tô, dolo, couscous and thin porridge could be correlated with amylase and phenolic enzyme activities and the contents of their substrates. The biochemical constituents determined are useful markers for selection of varieties for food utilisation with special emphasis on infant porridges.
    Sorghum grain as human food in Africa: relevance of content of starch and amylase activities
    Dicko, M.H. ; Gruppen, H. ; Traore, A.S. ; Voragen, A.G.J. ; Berkel, W.J.H. van - \ 2006
    African journal of biotechnology 5 (2006)5. - ISSN 1684-5315 - p. 384 - 395.
    bicolor l moench - beta-amylase - alpha-amylase - kernel characteristics - protein digestibility - functional ingredient - chemical-composition - partial-purification - cultivated sorghum - fermented sorghum
    Sorghum is a staple food grain in many semi-arid and tropic areas of the world, notably in Sub-Saharan Africa because of its good adaptation to hard environments and its good yield of production. Among important biochemical components for sorghum processing are levels of starch (amylose and amylopectin) and starch depolymerizing enzymes. Current research focus on identifying varieties meeting specific agricultural and food requirements from the great biodiversity of sorghums to insure food security. Results show that some sorghums are rich sources of micronutrients (minerals and vitamins) and macronutrients (carbohydrates, proteins and fat). Sorghum has a resistant starch, which makes it interesting for obese and diabetic people. In addition, sorghum may be an alternative food for people who are allergic to gluten. Malts of some sorghum varieties display a-amylase and ß-amylase activities comparable to those of barley, making them useful for various agro-industrial foods. The feature of sorghum as a food in developing as well as in developed countries is discussed. A particular emphasis is made on the impact of starch and starch degrading enzymes in the use of sorghum for some African foods, e.g. ¿tô¿, thin porridges for infants, granulated foods ¿couscous¿, local beer ¿dolo¿, as well agro-industrial foods such as lager beer and bread.
    Improvement of phosphorus availability by microbial phytase in broilers and pigs
    Simons, P.C.M. ; Versteegh, H.A.J. ; Jongbloed, A.W. ; Kemme, P.A. ; Slump, P. ; Bos, K.D. ; Wolters, M.G.E. ; Beudeker, R.F. ; Verschoor, G.J. - \ 2005
    The British journal of nutrition 93 (2005)1. - ISSN 0007-1145 - p. 137 - 152.
    phytic acid - alpha-amylase
    Techniques have been developed to produce microbial phytase for addition to diets for simple-stomached animals, with the aim to improve phosphorus availability from phytate-P in plant sources. The activityof the crude microbial phytase showed pH optima at pH 5-5 and 2·5. The enzyme was able to degradephytate in vitro in soya-bean meal, maize and a liquid compound feed for pigs. When microbial phytasewas added to low-P diets for broilers the availability of P increased to over 60 % and the amount of Pin the droppings decreased by 50%. The growth rate and feed conversion ratio on the low-P dietscontaining microbial phytase were comparable to or even better than those obtained on control diets.Addition of microbial phytase to diets for growing pigs increased the apparent absorbability of P by24%. The amount of P in the faeces was 35% lower.
    Sucrose-specific induction of anthocyanin biosynthesis in Arabidopsis requires the MYB75/PAP1 gene.
    Teng, S. ; Keurentjes, J.J.B. ; Bentsink, L. ; Koornneef, M. ; Smeekens, S. - \ 2005
    Plant Physiology 139 (2005)4. - ISSN 0032-0889 - p. 1840 - 1852.
    transgenic tobacco plants - 3' untranslated region - vitis-vinifera - transcriptional regulation - flavonoid biosynthesis - signal-transduction - bhlh proteins - alpha-amylase - beta-amylase - expression
    Sugar-induced anthocyanin accumulation has been observed in many plant species. We observed that sucrose (Suc) is the most effective inducer of anthocyanin biosynthesis in Arabidopsis (Arabidopsis thaliana) seedlings. Other sugars and osmotic controls are either less effective or ineffective. Analysis of Suc-induced anthocyanin accumulation in 43 Arabidopsis accessions shows that considerable natural variation exists for this trait. The Cape Verde Islands (Cvi) accession essentially does not respond to Suc, whereas Landsberg erecta is an intermediate responder. The existing Landsberg erecta/Cvi recombinant inbred line population was used in a quantitative trait loci analysis for Suc-induced anthocyanin accumulation (SIAA). A total of four quantitative trait loci for SIAA were identified in this way. The locus with the largest contribution to the trait, SIAA1, was fine mapped and using a candidate gene approach, it was shown that the MYB75/PAP1 gene encodes SIAA1. Genetic complementation studies and analysis of a laboratory-generated knockout mutation in this gene confirmed this conclusion. Suc, in a concentration-dependent way, induces MYB75/PAP1 mRNA accumulation. Moreover, MYB75/PAP1 is essential for the Suc-mediated expression of the dihydroflavonol reductase gene. The SIAA1 locus in Cvi probably is a weak or loss-of-function MYB75/PAP1 allele. The C24 accession similarly shows a very weak response to Suc-induced anthocyanin accumulation encoded by the same locus. Sequence analysis showed that the Cvi and C24 accessions harbor mutations both inside and downstream of the DNA-binding domain of the MYB75/PAP1 protein, which most likely result in loss of activity.
    Modeling of thickness for semisolid foods
    Terpstra, M.E.J. ; Janssen, A.M. ; Prinz, J.F. ; Wijk, R.A. de; Weenen, H. ; Linden, E. van der - \ 2005
    Journal of Texture Studies 36 (2005)2. - ISSN 0022-4901 - p. 213 - 233.
    oral perception - fluid-mechanics - alpha-amylase - viscosity - texture - mouth - mayonnaise - tongue
    We investigated the relationship between orally perceived thickness and calculated shear stress on the tongue for mayonnaise and custard. To this end, the applicability of the models of Kokini et al. (1977), describing the mechanical breakdown in the mouth, have been tested. Within a limited range of shear stresses (mayonnaise <150 Pa; custard <30 Pa), there was a linear relationship between shear stress and thickness, in accordance with the work of Kokini et al. (1977). Beyond this range, the linear relationship breaks down and the thickness levels off with shear stress for both mayonnaise and custard. The relationship over the entire range of shear stresses used in this paper can be satisfactorily described by a semilogarithmic (Fechner) relation. For both types of products, the quality of the thickness prediction by the decreasing-height model and the constant-height model of Kokini et al. (1977) is similar. For most mayonnaises, the contribution of the lateral movement of the tongue to the shear stress in the decreasing-height model of Kokini et al. (1977) is orders of magnitude larger than the contribution of the squeezing or compression movement of the tongue towards the palate. This difference in magnitude is affected by the low value measured for the compression force and by the high values for material consistency K. The values for K are high because yield-stress behavior has been neglected when the flow curves were analyzed. For custard, the models of Kokini et al. (1977) are found to be less adequate. It is proposed that this is because the models ignore interactions with saliva. Several routes to improve the modeling by incorporating viscoelastic behavior were unsuccessful. Elongational stress and yield stress were neglected in all tested models.
    Towards intensification of starch processing
    Veen, M.E. van der - \ 2005
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - Wageningen : s.n. - ISBN 9789085042181 - 104
    zetmeel - verwerking - microgolfbehandeling - verwarming - hydrolyse - versuikering - glucosesiropen - alfa-amylase - glucaan 1,4-alfa-glucosidase - starch - processing - microwave treatment - heating - hydrolysis - saccharification - glucose syrups - alpha-amylase - glucan 1,4-alpha-glucosidase

    The first topic covers the potential of microwave heating as means for mild preservation of heterogeneous food media. It has been postulated that if micro-organisms are present in domains that contain more moisture, it should be possible to selectively heat those areas and thus achieve the microbial inactivation with a lower overall thermal load onto the product. This concept of selective heating was investigated by an analysis of the dissipation of microwave energy and heat transfer phenomena in heterogeneous systems. The results presented in this thesis indicate that for domains sizes of millimetres or larger, temperature differences>lOK can be established. For smaller domains, large temperature differences are not possible with currently available microwave technology.
    The second topic focussed starch hydrolysis under low water conditions, with emphasis on the liquefaction and saccharification process steps. The results presented in this thesis showed that it is possible to hydrolyse starch in conditions of up to 65% dry matter. Two conceptual process designs were developed to liquefy starch in conditions with maximally 60% dry matter (single stage process) and higher dry solid conditions (two stage process) by means of a thermo-mechanical treatrnent. The effects of shear forces on a-amylase was measured and could be quantitatively described with a relative simple model, incorporating the effect of time, temperature and shear stress. Furthermore, it was reported that saccharification with glucoamylase is possible at very high dry matter concentrations, while hardly any additional inhibition of the enzyme was observed under those conditions. The rate of reaction was found to decrease with increasing dry matter concentration. Simulations showed that at conditions with 70% dry matter initially, still a product of 90 DE could be produced.
    The results were concluded in a process model showing that increasing the dry matter concentration of 35% to 65% resulted in a decrease in water consumption of 87% for a given glucose production, while the reactor productivity was calculated to increase with 17%. Although several aspects have to be studied in more detail before successful implementation of the process, the study reported here reveals that there is clear potential for making the production of glucose from starch more efficient in terms of energy and water consumption.
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