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Chemical composition and antioxidant activity of cured chestnuts from three sweet chestnut (Castanea sativa Mill.) ecotypes from Italy
No full textThe composition of commercial marrons from three Italian sweet chestnut ecotypes, 'Marrone di Castel del Rio', 'Marrone di Marradi', and 'Marrone di Valle Castellana', from Emilia Romagna, Tuscany and Abruzzi region, respectively, was studied during two consecutive years (2003-2004). Results showed a great variability of moisture content. The average content in nutrients (expressed in dry weight) was in the normal range for this type of product, but compositional data showed great variability as a function both of variety and of harvest year. Marrone di Valle Castellana showed the highest content in sucrose and fibre. Marrone di Castel del Rio presented the highest protein content, probably due to the schistose soil of the region. Marrons of Valle Castellana presented the lowest calcium content as a result of the specific nature of the soil in the area of origin. Linear discriminant analysis achieved high recognition percentages for the classification of marrons according to the ecotype, with 100% recognition for each of the three ecotypes. The content in antioxidant compounds (ascorbic acid and total polyphenols) and the antioxidant activity of the nuts were investigated. All the ecotypes showed a low polyphenol content but were high in ascorbic acid level, which accounted for a discrete antioxidant activity (3.02 - 3.11 TEACg(f.w.)(-1)) of the nuts
Effect of trehalose on peroxidase and pectinesterase activity of blanched and frozen carrots
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Effect of semolina particle size on the cooking kinetics and quality of spaghetti
No full textA durum wheat was milled in order to obtain medium (M), medium coarse (MC) and coarse (C) semolinas with an average particle size of 275, 375 and 475 mu m respectively. The three semolinas were characterized for their chemical and physical properties. The M semolina showed higher ash, protein and gluten content, a higher gluten extensibility but a lower gluten index and yellow colour than coarser semolinas. Spaghetti were produced with the three semolinas. Dried spaghetti were characterized for their diameter, hardness and colour and eventually tested for their cooking quality. Spaghetti from MC and C semolina showed higher optimum cooking time (OCT) than spaghetti from M semolina. Cooking time being equal, the weight and diameter increase was higher in spaghetti from coarser semolinas. Within OCT, the hardness of spaghetti from MC and C semolina was higher than that of spaghetti from M semolina. The high OCT and hardness (before OCT) of the semi-cooked pasta obtained from MC and C semolina could be useful in two-step cooking processes in which pasta is pre-cooked and cooled before the final cooking step. (c) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of 11th International Congress on Engineering and Food (ICEF 11) Executive Committee
Influence of water activity and system mobility on peroxidase activity in maltodextrin solutions
No full textMaltodextrins influenced the enzymatic activity
in aqueous solutions by affecting the water activity (aw) and
mobility as described by viscosity and T’g. In diluted
solutions, viscosity being equal, (1) maltodextrin with
dextrose equivalents (DE) of 33 was more effective than
glucose in limiting horseradish peroxidase (HRP) activity;
(2) an increase in the maltodextrin chain length from DE 33
to DE 8.7 did not further limited enzymatic activity; (3) the
maltodextrin with the highest chain length (DE 2.5)
determined the highest enzyme inhibition. In general, the
increase of molecular weight negatively affected the HRP
activity by increasing the viscosity and T’g (decreasing
molecular mobility) but it positively affected the aw and, in
some cases, this compensated the HRP activity inhibition.
In concentrated solutions (apparent viscosity≈40 mPa s) the
HRP activity decreased with the increase of the maltodextrin
molecular weight, and it showed a dependence on T’g
which could be described by a William, Landel and Ferry
(WLF)-type equation. On the contrary, in the solution
added with the maltodextrin with the highest chain length
(DE 2.5) the HRP activity was much higher than that
predicted by the WLF-type equation. The maltodextrin with
DE 2.5 contains intact starch fragments and in water forms a
suspension. In such a discontinuous system, the viscosity in
the vicinity of the protein is lower than the bulk viscosity,
and thus, the enzyme activity is higher than expected.
Moreover, since T’g is a property of the soluble phase, it
does not explain the mobility in discontinuous systems
Chemical Composition and Functional Properties of Three Sweet Chestnut (Castanea sativa Mill.) Ecotypes from Italy
No full textInfluence of water activity and molecular mobility on peroxidase activity in salt and sorbitol-maltodextrin systems
No full textSolvent composition, system mobility and viscosity play a central role in the regulation of enzymatic activity.The aim of this study was to investigate the individual and combined effect of water activity (aw), bulk viscosity and glass transition temperature (T’g) on the activity of horseradish peroxidase (HRP) in buffered solutions. For this purpose, the water activity of the solutions was modulated using both a ionic (sodium chloride) and a non-ionic (sorbitol) ligand and viscosity changed upon the addition of maltodextrin.In viscous solutions characterized by different compositions, the effectiveness of a solute in the inhibition of the HRP activity was dependent both on the chemical properties of the solution, as described by aw, and on the mobility of the system, as described by the inverse of viscosity and T-T’g. Viscosity was the most important factor in the inhibition of HRP activity in solutions characterized by the same T’g value, but when T’g was changed, due to changes in the solutes composition, the latter became a key factor in the regulation of the enzyme activity. In salt-maltodextrin systems the water activity reduction limited HRP activity with higher efficiency at low viscosities whilst in sorbitol–maltodextrin systems, characterised by different T’g values, the aw lowering by sorbitol addition resulted in the increase of HRP activity depending on its effect on T’g.[...
Activity of horseradish peroxidase and bovine lactoperoxidase as affected by physical properties of the solution
No full textIntroduction Enzymatic activity in solution is largely influenced by environmental factors such as the physical properties of the system. Viscosity is referred to as an index of the mobility of a system since it is related to the translational diffusion by the Stokes relationship. Kramers’ theory [1] predicts that the rate for the dynamics should have an inverse relationship with viscosity. Even if a large body of work indicates that Kramers’ theory does not always predict protein dynamics properly [2], large amplitude (global) protein motions and, in particular, those involving exterior portions of the protein, appear to follow Kramers’ relation at viscosities above ≈ 1 cP [3,4] whilst diffusive motions involving smaller portions of the protein are less likely to follow Kramers’ relation at high viscosities [2]. Deviations from Kramers’ relation for exterior protein motions has been attributed to solvent composition and viscosity in the immediate vicinity of the protein.Independently of viscosity, other physical variables could affect the enzyme kinetics in solutions. In particular, in highly viscous concentrated solutions, water activity, which is a thermodynamical variable extensively used to describe the chemical potential of water in binary and complex systems, could play a significant role [5].The aim of this study was to investigate and compare the effect of viscosity and water activity (aw) on the activity of horseradish peroxidase (HRP) and bovine lactoperoxidase (LPO) in buffered solutions. HRP (44,173.9 Da) is an enzyme with an highly accessible active site whilst LPO is a larger enzyme (78,431 Da) with a deeply buried active site with a restrictive substrate access channel which should limit the influence of physical properties of the solution (such as viscosity and water activity) on enzymatic catalysis.ExperimentalConcentrated binary and ternary buffered solutions with were prepared by using 0.1 M potassium phosphate buffer, maltose, trehalose and maltodextrins ( : 30.000).HRP and LPO activity was tested in buffered solutions using the method of Keesey [6]. Viscosity was measured using a falling ball viscometer while water activity was measured using a dew point hygrometer. All measurements were carried out at 25 °C. Differential scanning calorimetry was used for the T’g determination. Thermograms were obtained after annealing at T’g + 10 °C. ResultsIn viscous solutions characterized by different composition, the inhibition of the HRP activity was dependent both on the thermodynamical properties of the solution, as described by water activity, and on the mobility of the system, as described by the inverse of viscosity and T-T’g. Viscosity was the most important factor in the inhibition of enzymatic activity in solutions characterized by the same T’g value, but when T’g was changed, due to changes in the solutes composition, the latter became the key factor in the regulation of the enzyme activity. HRP activity was much more influenced by changes in the water activity than LPO activity which, in turn, was much more influenced by changes in viscosity. The results of this study suggest that for large enzymes the translational diffusivity which, according to the Stokes-Einstein law, is inversely related to viscosity and molecular weight, is a far more critical factor than the accessibility of the active site. On the other hand, the water status of the solution seems to be a far more critical factor for the activity of enzymes with an active site highly accessible and expose to the external environment
Chemical composition and functional properties of sweet chestnuts (Castanea sativa, Mill.) ecotypes from Italy
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