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May R Berenbaum - One of the best experts on this subject based on the ideXlab platform.
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Patterns of Genetic Diversity in the Globally Invasive Species Wild Parsnip (Pastinaca sativa)
Invasive Plant Science and Management, 2015Co-Authors: Tania Jogesh, Rhiannon Peery, Stephen R. Downie, May R BerenbaumAbstract:Wild parsnip is an invasive species with a global distribution in temperate climates. Parsnips are native to Eurasia and have been cultivated for more than five centuries. It is unclear whether the global invasion of this species is a consequence of escape from cultivation or the accidental introduction of a Eurasian wild subspecies. In this study, we used nuclear ribosomal DNA internal transcribed spacer (ITS) and chloroplast DNA (cpDNA) markers to evaluate the genetic structure of wild parsnip in its native range (Europe) and in three distinct geographic regions where it is considered invasive: eastern North America, western North America, and New Zealand. We also compared wild and cultivated parsnips to determine whether they are genetically distinct. From 112 individuals, we recovered 14 ITS and 27 cpDNA haplotypes. One ITS haplotype was widespread; few haplotypes were rare singletons. In contrast, at least two lineages of cpDNA haplotypes were recovered, with several novel haplotypes restricted to Eu...
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generalist and specialist host parasitoid associations respond differently to wild parsnip Pastinaca sativa defensive chemistry
Ecological Entomology, 2011Co-Authors: Evan C. Lampert, Arthur R. Zangerl, May R Berenbaum, Paul J OdeAbstract:1. Plant defensive chemistry is predicted to have a more negative effect on generalist herbivores and their parasitoids than on specialist herbivores and their parasitoids. 2. This prediction was examined by comparing the effects of the wild parsnip (Pastinaca sativa L.) toxin, xanthotoxin, on a generalist herbivore–parasitoid association [the cabbage looper, Trichoplusia ni Hubner, and its polyembryonic parasitoid, Copidosoma floridanum (Ashmead)] and a specialist herbivore–parasitoid association [the parsnip webworm, Depressaria pastinacella (Duponchel), and its polyembryonic parasitoid, Copidosoma sosares (Walker)]. 3. Copidosoma floridanum brood sizes were smaller and experienced lower survivorship when reared in a host feeding on an artificial diet containing a low concentration of xanthotoxin. No T. ni hosts, parasitised or unparasitised, survived on a diet high in xanthotoxin. In contrast, C. sosares brood size and survivorship were unaffected by the presence of low levels of xanthotoxin in the host diet. Copidosoma sosares experienced reduced brood size and survivorship only when its host consumed a diet containing 15 times the level of xanthotoxin as the diet adversely affecting its congener. 4. The differences in response to xanthotoxin exhibited by C. floridanum and C. sosares are explained partly by a differential reduction in host quality and partly by differential exposure to xanthotoxin in host haemolymph. Unlike D. pastinacella, T. ni experienced reduced pupal weight and survivorship and prolonged developmental time on a low-xanthotoxin diet. More xanthotoxin passed unmetabolised into the haemolymph of T. ni than into the haemolymph of D. pastinacella.
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Autotoxic effects of essential oils on photosynthesis in parsley, parsnip, and rough lemon
CHEMOECOLOGY, 2005Co-Authors: May R Berenbaum, Evan H. Delucia, Arthur R. ZangerlAbstract:Many plant species contain essential oils with allelochemical properties, yet the extent to which these same chemicals can be autotoxic is unclear. In this study, we tested the toxicity of several essential oil components to three species that produce them— Pastinaca sativa and Petroselinum crispum (Apiaceae), and Citrus jambhiri (Rutaceae). The effects of exogenous application of small amounts of essential oil components to the surface of foliage, followed by a pinprick to allow entry into the leaf, were monitored by chlorophyll fluorescence imaging. Rapid and spatially extensive declines in photosynthetic capacity were detected within 200 s. The most toxic constituents were monoterpenes. Two sesquiterpenes, caryophyllene and farnesene, and the phenylpropanoid myristicin, by comparison, were not toxic. Autotoxicity of endogenous essential oil was investigated by slicing through containment structures (glands or tubes); significant toxicity, manifested by reduced photosynthetic activity, was observed in all three species but was most pronounced in P. sativa and P. crispum , both of which possess oil tubes.
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Genetic variation in primary metabolites of Pastinaca sativa; can herbivores act as selective agents?
Journal of chemical ecology, 2004Co-Authors: Arthur R. Zangerl, May R BerenbaumAbstract:Although insect herbivory has been shown to act as a selective agent on plant secondary metabolism, whether primary metabolites contribute to resistance and can respond to selection by herbivores remains untested. In the wild parsnip (Pastinaca sativa), its principal herbivore, Depressaria pastinacella, acts as a selective agent on furanocoumarin resistance factors. In this study, we determined whether webworms can, by causing differential reductions in fitness, act as selective agents on parsnip primary metabolites. Estimates of narrow-sense heritabilities were significantly different from zero for C18 fatty acids in buds and developing fruits, fructose and sorbitol in buds, fructose, myoinositol, bergapten, and psoralen in fruits. Wild parsnips protected from webworms by insecticide produced 2.5 times as much seed biomass as unsprayed plants; that webworms accounted for this difference in plant fitness was indicated by a significant negative relationship between reproductive effort and an index of webworm damage. Only a handful of metabolites influenced resistance to webworms; these included osthol, sorbitol, and protein in developing fruits as well as previously documented furanocoumarins. Osthol, a coumarinic compound, enhanced resistance, as did protein content, while sorbitol lowered resistance. Other primary metabolites may affect resistance to webworms but their effect was context-dependent, that is, their effect depended on concentrations of other metabolites (epistasis). Susceptible plant phenotypes were found to have average chemical compositions. Although there was genetic variation in some of the primary metabolites in parsnips, the epistatic nature of their involvement in resistance and the lack of genetic variation in some suggest that selection on them from webworms will be either inconsistent or ineffective.
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Fathers, fruits and photosynthesis: pollen donor effects on fruit photosynthesis in wild parsnip
Ecology Letters, 2003Co-Authors: Arthur R. Zangerl, May R Berenbaum, Evan H. DeluciaAbstract:Chlorophyll is frequently present in plant reproductive tissues and indicates that photosynthesis is occurring in these parts. Photosynthesis by a reproductive organ can contribute as much as 65% to its own growth. Given the advantages that increased photosynthetic rates might have on development of individual seeds competing for resources, selection can be expected to favour the ability of offspring to influence photosynthetic rates of the tissues surrounding them. We report in this study the first evidence that the pollen genotype can influence the rate of photosynthesis in the fruit tissues surrounding the developing offspring. Using a novel chlorophyll fluorescence imaging instrument to quantify quantum efficiency of photosystem II, we found significant differences in photosynthetic rates among fruits in wild parsnip, Pastinaca sativa L, associated with different pollen genotypes.
Arthur R. Zangerl - One of the best experts on this subject based on the ideXlab platform.
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LETTER Fathers, fruits and photosynthesis: pollen donor effects on fruit photosynthesis in wild parsnip
2014Co-Authors: Arthur R. Zangerl, Evan H. Delucia, May RAbstract:Chlorophyll is frequently present in plant reproductive tissues and indicates that photosynthesis is occurring in these parts. Photosynthesis by a reproductive organ can contribute as much as 65 % to its own growth. Given the advantages that increased photosynthetic rates might have on development of individual seeds competing for resources, selection can be expected to favour the ability of offspring to influence photosynthetic rates of the tissues surrounding them. We report in this study the first evidence that the pollen genotype can influence the rate of photosynthesis in the fruit tissues surrounding the developing offspring. Using a novel chlorophyll fluorescence imaging instrument to quantify quantum efficiency of photosystem II, we found significant differences in photosynthetic rates among fruits in wild parsnip, Pastinaca sativa L, associated with different pollen genotypes
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generalist and specialist host parasitoid associations respond differently to wild parsnip Pastinaca sativa defensive chemistry
Ecological Entomology, 2011Co-Authors: Evan C. Lampert, Arthur R. Zangerl, May R Berenbaum, Paul J OdeAbstract:1. Plant defensive chemistry is predicted to have a more negative effect on generalist herbivores and their parasitoids than on specialist herbivores and their parasitoids. 2. This prediction was examined by comparing the effects of the wild parsnip (Pastinaca sativa L.) toxin, xanthotoxin, on a generalist herbivore–parasitoid association [the cabbage looper, Trichoplusia ni Hubner, and its polyembryonic parasitoid, Copidosoma floridanum (Ashmead)] and a specialist herbivore–parasitoid association [the parsnip webworm, Depressaria pastinacella (Duponchel), and its polyembryonic parasitoid, Copidosoma sosares (Walker)]. 3. Copidosoma floridanum brood sizes were smaller and experienced lower survivorship when reared in a host feeding on an artificial diet containing a low concentration of xanthotoxin. No T. ni hosts, parasitised or unparasitised, survived on a diet high in xanthotoxin. In contrast, C. sosares brood size and survivorship were unaffected by the presence of low levels of xanthotoxin in the host diet. Copidosoma sosares experienced reduced brood size and survivorship only when its host consumed a diet containing 15 times the level of xanthotoxin as the diet adversely affecting its congener. 4. The differences in response to xanthotoxin exhibited by C. floridanum and C. sosares are explained partly by a differential reduction in host quality and partly by differential exposure to xanthotoxin in host haemolymph. Unlike D. pastinacella, T. ni experienced reduced pupal weight and survivorship and prolonged developmental time on a low-xanthotoxin diet. More xanthotoxin passed unmetabolised into the haemolymph of T. ni than into the haemolymph of D. pastinacella.
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Autotoxic effects of essential oils on photosynthesis in parsley, parsnip, and rough lemon
CHEMOECOLOGY, 2005Co-Authors: May R Berenbaum, Evan H. Delucia, Arthur R. ZangerlAbstract:Many plant species contain essential oils with allelochemical properties, yet the extent to which these same chemicals can be autotoxic is unclear. In this study, we tested the toxicity of several essential oil components to three species that produce them— Pastinaca sativa and Petroselinum crispum (Apiaceae), and Citrus jambhiri (Rutaceae). The effects of exogenous application of small amounts of essential oil components to the surface of foliage, followed by a pinprick to allow entry into the leaf, were monitored by chlorophyll fluorescence imaging. Rapid and spatially extensive declines in photosynthetic capacity were detected within 200 s. The most toxic constituents were monoterpenes. Two sesquiterpenes, caryophyllene and farnesene, and the phenylpropanoid myristicin, by comparison, were not toxic. Autotoxicity of endogenous essential oil was investigated by slicing through containment structures (glands or tubes); significant toxicity, manifested by reduced photosynthetic activity, was observed in all three species but was most pronounced in P. sativa and P. crispum , both of which possess oil tubes.
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Genetic variation in primary metabolites of Pastinaca sativa; can herbivores act as selective agents?
Journal of chemical ecology, 2004Co-Authors: Arthur R. Zangerl, May R BerenbaumAbstract:Although insect herbivory has been shown to act as a selective agent on plant secondary metabolism, whether primary metabolites contribute to resistance and can respond to selection by herbivores remains untested. In the wild parsnip (Pastinaca sativa), its principal herbivore, Depressaria pastinacella, acts as a selective agent on furanocoumarin resistance factors. In this study, we determined whether webworms can, by causing differential reductions in fitness, act as selective agents on parsnip primary metabolites. Estimates of narrow-sense heritabilities were significantly different from zero for C18 fatty acids in buds and developing fruits, fructose and sorbitol in buds, fructose, myoinositol, bergapten, and psoralen in fruits. Wild parsnips protected from webworms by insecticide produced 2.5 times as much seed biomass as unsprayed plants; that webworms accounted for this difference in plant fitness was indicated by a significant negative relationship between reproductive effort and an index of webworm damage. Only a handful of metabolites influenced resistance to webworms; these included osthol, sorbitol, and protein in developing fruits as well as previously documented furanocoumarins. Osthol, a coumarinic compound, enhanced resistance, as did protein content, while sorbitol lowered resistance. Other primary metabolites may affect resistance to webworms but their effect was context-dependent, that is, their effect depended on concentrations of other metabolites (epistasis). Susceptible plant phenotypes were found to have average chemical compositions. Although there was genetic variation in some of the primary metabolites in parsnips, the epistatic nature of their involvement in resistance and the lack of genetic variation in some suggest that selection on them from webworms will be either inconsistent or ineffective.
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Fathers, fruits and photosynthesis: pollen donor effects on fruit photosynthesis in wild parsnip
Ecology Letters, 2003Co-Authors: Arthur R. Zangerl, May R Berenbaum, Evan H. DeluciaAbstract:Chlorophyll is frequently present in plant reproductive tissues and indicates that photosynthesis is occurring in these parts. Photosynthesis by a reproductive organ can contribute as much as 65% to its own growth. Given the advantages that increased photosynthetic rates might have on development of individual seeds competing for resources, selection can be expected to favour the ability of offspring to influence photosynthetic rates of the tissues surrounding them. We report in this study the first evidence that the pollen genotype can influence the rate of photosynthesis in the fruit tissues surrounding the developing offspring. Using a novel chlorophyll fluorescence imaging instrument to quantify quantum efficiency of photosystem II, we found significant differences in photosynthetic rates among fruits in wild parsnip, Pastinaca sativa L, associated with different pollen genotypes.
Célia Krieger - One of the best experts on this subject based on the ideXlab platform.
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molecular evolution of parsnip Pastinaca sativa membrane bound prenyltransferases for linear and or angular furanocoumarin biosynthesis
New Phytologist, 2016Co-Authors: Ryosuke Munakata, Célia Krieger, Alexandre Olry, Fazeelat Karamat, Vincent Courdavault, Akifumi Sugiyama, Yoshiaki DateAbstract:In Apiaceae, furanocoumarins (FCs) are plant defence compounds that are present as linear or angular isomers. Angular isomers appeared during plant evolution as a protective response to herbivores that are resistant to linear molecules. Isomeric biosynthesis occurs through prenylation at the C6 or C8 position of umbelliferone. Here, we report cloning and functional characterization of two different prenyltransferases, Pastinaca sativa prenyltransferase 1 and 2 (PsPT1 and PsPT2), that are involved in these crucial reactions. Both enzymes are targeted to plastids and synthesize osthenol and demethylsuberosin (DMS) using exclusively umbelliferone and dimethylallylpyrophosphate (DMAPP) as substrates. Enzymatic characterization using heterologously expressed proteins demonstrated that PsPT1 is specialized for the synthesis of the linear form, demethylsuberosin, whereas PsPT2 more efficiently catalyses the synthesis of its angular counterpart, osthenol. These results are the first example of a complementary prenyltransferase pair from a single plant species that is involved in synthesizing defensive compounds. This study also provides a better understanding of the molecular mechanisms governing the angular FC biosynthetic pathway in apiaceous plants, which involves two paralogous enzymes that share the same phylogenetic origin.
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identification moleculaire et caracterisation fonctionnelle d une nouvelle sous famille de cytochromes p450 cyp71az impliquee dans la synthese de furanocoumarines et coumarines chez Pastinaca sativa
2014Co-Authors: Célia KriegerAbstract:Les furanocoumarines (FCs) sont des metabolites secondaires principalement synthetises chez quatre familles botaniques et derivent de la voie de biosynthese des phenylpropanoides. Ces phytoalexines interviennent dans les processus de defense de la plante et presentent un fort potentiel therapeutique. Des travaux realises dans les annees 1960 sur des cultures cellulaires en parallele de l’utilisation de precurseurs radiomarques ont permis de demontrer que de nombreuses enzymes impliquees dans cette voie appartenaient a la famille des cytochromes P450 (P450s). Seules deux d’entre elles avaient pu etre identifiees d’un point de vue moleculaire au debut de ce travail de these. Afin de generer des informations concernant le genome de plantes productrices de FCs, nous avons fait sequencer les ARNm extraits de feuilles de Pastinaca sativa, de Ruta graveolens et de Cullen cinereum. L’analyse in silico de ces trois banques de donnees a permis d’identifier pres de 800 fragments d’ADNc codants pour des P450s. Des travaux anterieurs realises au laboratoire et l’analyse comparative des transcriptomes de ces 3 plantes nous ont amenes a nous focaliser sur la sous-famille CYP71AZ au travers d’une etude fine de CYP71AZ3 et CYP71AZ4. La caracterisation fonctionnelle de ces enzymes a ete realisee dans un systeme d’expression heterologue eucaryote : Saccharomyces cerevisiae. Les resultats obtenus ont permis de montrer que CYP71AZ4 avait une specificite de substrat assez large puisqu’elle pouvait metaboliser au moins une FC et 4 coumarines. L’analyse et la comparaison des constantes cinetiques pour chacun de ces substrats indiquent neanmoins que le psoralene est le substrat preferentiel. La caracterisation fonctionnelle de CYP71AZ3 a mis en evidence que cette enzyme pouvait hydroxyler l’esculetine, une coumarine, mais ne jouait aucun role dans la synthese de FCs. Ces travaux mettent en evidence la diversite fonctionnelle au sein d’une meme sous-famille enzymatique et permettent d’emettre des hypotheses nouvelles quant a l’apparition de cette voie de biosynthese chez les Apiacees d’une part, et chez les autres familles botaniques d’autre part
Ivana Plačková - One of the best experts on this subject based on the ideXlab platform.
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Can soil seed banks serve as genetic memory? A study of three species with contrasting life history strategies.
PloS one, 2012Co-Authors: Bohumil Mandák, Petr Zákravský, Václav Mahelka, Ivana PlačkováAbstract:We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testing the hypothesis that standing (aboveground) plants represent a nonrandom sample of the seed bank. We sampled multilocus allozyme genotypes from three species with different life history strategies: Amaranthus retroflexus, Carduus acanthoides, Pastinaca sativa. In four populations of each species we analysed the extent to which allele and genotype frequencies vary in consecutive life history stages including the summer seed bank, which has been overlooked up to now. We compared the winter seed bank (i.e., seeds collected before the spring germination peak), seedlings, rosettes, the summer seed bank (i.e., seeds collected after the spring germination peak) and fruiting plants. We found that: (1) All three species partitioned most of their genetic diversity within life history stages and less among stages within populations and among populations. (2) All genetic diversity parameters, except for allele frequencies, were similar among all life history stages across all populations in different species. (3) There were differences in allele frequencies among life history stages at all localities in Amaranthus retroflexus and at three localities in both Carduus acanthoides and Pastinaca sativa. (4) Allele frequencies did not differ between the winter and summer seed bank in most Carduus acanthoides and Pastinaca sativa populations, but there was a marked difference in Amaranthus retroflexus. In conclusion, we have shown that the summer seed bank is not genetically depleted by spring germination and that a majority of genetic diversity remains in the soil through summer. We suggest that seed banks in the species investigated play an important role by maintaining genetic diversity sufficient for recovery rather than by accumulating new genetic diversity at each locality.
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Population genetic characteristics of Pastinaca sativa.
2012Co-Authors: Bohumil Mandák, Petr Zákravský, Václav Mahelka, Ivana PlačkováAbstract:Comparison of allelic richness (RS), observed heterozygosity (HO), gene diversity (HS) and inbreeding coefficient (FIS) for individual life history stages of Pastinaca sativa at four localities. * Significant differences among life history stages within a locality were determined by two-sided t-tests after 10 000 permutations (analysis performed using FSTAT [47]).
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Location of Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa populations.
2012Co-Authors: Bohumil Mandák, Petr Zákravský, Václav Mahelka, Ivana PlačkováAbstract:Map showing the location of the 20 populations of each of the three species under study, i.e. Amaranthus retroflexus (empty circles), Carduus acanthoides (empty squares) and Pastinaca sativa (empty triangles). Four localities of each species were selected and used in the present study (highlighted by full symbols).
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Analysis of molecular variance in Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa.
2012Co-Authors: Bohumil Mandák, Petr Zákravský, Václav Mahelka, Ivana PlačkováAbstract:Analysis of molecular variance among populations, among life history stages within populations, and within life history stages of Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa. Significance of variance components were tested by a permutation test (*P
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Genetic diversity of Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa (from other studies).
2012Co-Authors: Bohumil Mandák, Petr Zákravský, Václav Mahelka, Ivana PlačkováAbstract:Comparison of genetic diversity within 20 populations of Amaranthus retroflexus, Carduus acanthoides and Pastinaca sativa based on allozyme loci (data taken from [45], [46] and Mandák et al., unpublished data, respectively). PL = percentage of polymorphic loci. A = average number of alleles per polymorphic locus. Ho = observed heterozygosity. He = expected heterozygosity. F, f, θ = Weir and Cockerham’s estimates of Wright’s F statistics (FIT, FIS and FST, respectively) which represents deviations from Hardy-Weinberg expectations over all populations, deviations within individual populations and the proportion of total genetic diversity partitioned among populations. * Significant deviation (P
Alejandra Castro - One of the best experts on this subject based on the ideXlab platform.
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Physicochemical properties of root fiber suspensions. A comparison between parsnip (Pastinaca sativa) and yacon (Smallanthus sonchifolius)
2013Co-Authors: Alejandra CastroAbstract:Popular Abstract in English The current interest in improving the nutritional benefits of food products and the need to recover undeveloped crops prompted us to study two plant roots: parsnip (Pastinaca sativa) and yacon (Smallanthus sonchifolius). Parsnip is a root native to Europe and Asia, and is often used for culinary purposes and to feed livestock. Parsnip was a popular vegetable in the Middle Ages but the interest in this root declined with the arrival of the potato in Europe. Yacon roots are originally from Andean countries in South America, cultivated since pre-colonial times, and it is commonly eaten raw as a fruit due to its slightly sweet taste and crunchy texture. The cultivation of yacon in Andean countries declined slowly through most of the past century, limiting access to this root and its commercialization. However, interest has been growing steadily in the past ten years due to studies showing its health benefits. The study and evaluation of the properties of these two roots might help to increase interest in these roots and their further industrial use. Parsnip and yacon roots have a dry matter content of 20% and 10%, respectively. The two roots differ in their storage polysaccharide (i.e. the plant’s energy source). The storage polysaccharide in parsnip is starch, whereas the storage polysaccharide in yacon is fructans. These fructans also have dietary fiber properties. The dietary fiber in parsnip mainly comprises the cell wall polysaccharides (cellulose, hemicellulose, and pectin substances), whereas the dietary fiber in yacon is mainly fructans and only a small proportion in the form of cellulose, hemicellulose, and pectin. Parsnip and yacon roots are both a promising source of dietary fiber with relatively high values of about 30% (parsnip) and 45% (yacon) of the dry matter. Yacon in particular is a significant source of fructans. Another difference between these two roots is the amount of dietary fiber determined as soluble and insoluble. Most of the dietary fiber in parsnip is obtained as insoluble dietary fiber while, in yacon, most is obtained as soluble dietary fiber. Parsnip and yacon roots in the form of pastes were used to prepare aqueous suspensions by suspending the paste in distilled water. These aqueous suspensions were subjected to processes such as valve pressure homogenization and heating. These two processes are often used in industrial processing of these types of materials. Properties such as the amount of insoluble particles, the particle size distribution, and the volume fraction of the particles were measured in the suspensions, and then related to the rheological properties. Parsnip and yacon suspensions initially comprised cell clusters, but homogenization broke these cell clusters. After homogenization, parsnip suspensions had smaller cell clusters and some single cells; yacon suspensions after homogenization, besides presenting smaller cell clusters, also presented aggregation of cell fragments. Yacon cells were slightly easier to disrupt by homogenization than parsnip cells. Parsnip and yacon suspensions displayed ‘solid-like’ rheological behavior (Gʹ>Gʹʹ) because of the amount of insoluble particles in the suspension. Parsnip suspensions started to present a rather strong particle network when the concentration of insoluble particles (i.e. cell fragments) was quite high (around 2.7 g/100 g suspension). In contrast, yacon suspensions already exhibited a strong particle network at a rather low concentration of insoluble particles (around 0.7 g/100 g suspension). We should remember that yacon contains a significant amount of fructans, but these are mainly found in the soluble fraction (i.e. often not considered as particles but as soluble polysaccharides). Results from our investigation suggested that these ‘soluble’ fructans form small particles with sizes in the nano-range. Besides the amount of particles, particle properties such as rigidity are also important in the rheological properties of concentrated parsnip suspensions (above 2.7 g insoluble particles/100 g suspensions). When parsnip suspensions were heated at 60°C for 40 min, an enzyme (pectin methyl esterase) was activated. This enzyme facilitated the cross-link of pectin chains in cell walls of the particles and so the rigidity of the particles increased. Parsnip suspensions with these types of particles showed enhanced rheological properties. Conversely, when parsnip suspensions were heated at 80°C for 2h, chemical reactions occurred that solubilized pectin. The solubilization of pectin from the cell walls reduced the rigidity of the particles. Parsnip suspensions with these types of particles showed lower elastic properties than suspensions with rigid particles. (Less)
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Effect of heat treatment and homogenization on the rheological properties of aqueous parsnip suspensions
Journal of Food Engineering, 2013Co-Authors: Alejandra Castro, Björn Bergenståhl, Eva TornbergAbstract:Parsnip (Pastinaca sativa) suspensions, at concentrations corresponding to a dilute and concentrated regime, were subjected to pasteurization, and heat treatments that favored beta-elimination reactions and pectin methyl esterase activity. The different heat treatments were combined with homogenization. Physicochemical properties such as content of insoluble/soluble material and insoluble/soluble pectin were measured together with particle and rheological properties. Pectin methyl esterase activity led to a high yield of insoluble material and insoluble pectin, whereas beta-elimination led to a high yield of soluble material and solubilized pectin. Homogenization after heat treatment resulted in increased solubilization of the pectin, especially after beta-elimination reactions. Parsnip suspensions subjected to pectin methyl esterase activity exhibited the highest elastic modulus most likely due to the cross-linked pectin conferring rigidity to the cell walls. The content of insoluble material and the particle properties such as size and rigidity are important factor for the rheological properties of concentrated parsnip suspensions. (Less)
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Parsnip (Pastinaca sativa L.): Dietary fibre composition and physicochemical characterization of its homogenized suspensions
Food Research International, 2012Co-Authors: Alejandra Castro, Björn Bergenståhl, Eva TornbergAbstract:Abstract The dietary fibre composition in parsnip has been determined in the soluble and insoluble fraction, together with the physicochemical properties (morphology of particles, particle size distribution (PSD), volume fraction and rheological properties) of the parsnip suspensions at different paste concentration and degree of homogenization. The content of dietary fibre in parsnip was 30.4% of the dry matter, composed mainly by neutral sugars (18.4%), pectic substances (10.10%) and Klason lignin (1.92%). Homogenization affected the particle size distribution of parsnip suspension (p d 32 L ) and the volume percentage of large particles ( vol L %) decreased, whereas the volume percentage of small particles ( vol S %) increased. Concentration affected the rheological properties of parsnip suspensions (p ϕ ) increased with paste concentration but was reduced with homogenization. By plotting the elastic modulus, G ′, as a function of volume fraction, ϕ , we showed the existence of a diluted and concentrated regime with a transition region at approximately ϕ = 19% for parsnip suspensions. Above the transition region, concentration of particles played an important role for the rheological properties. Based on the results achieved in this investigation we suggest that the gel network is mainly formed by the large particles, e.g. > 100 μm, and the smaller are preferably in the voids between the larger ones.