Parsnip (Pastinaca sativa L.): Dietary fibre composition and physicochemical characterization of its homogenized suspensions
2012
Castro, Alejandra | Bergenståhl, Björn | Tornberg, Eva
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<0.001), resulting in smaller cell-clusters. By increasing the degree of homogenization, the area based diameter of large particles (d₃₂L) and the volume percentage of large particles (volL %) decreased, whereas the volume percentage of small particles (volS %) increased. Concentration affected the rheological properties of parsnip suspensions (p<0.001). The volume fraction (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. >100μm, and the smaller are preferably in the voids between the larger ones.
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