Food Biophysics

Cesàro, Attilio; Brady, John W.

doi: 10.1007/s11483-013-9319-ypmid: N/A

This special issue is based on a collection of papers from a Conference on Water Biophysics which attempts to develop a fundamental understanding on how peculiar the interaction of water with biomolecules is. The Conference highlighted the great relevance of fundamental biophysical concepts in the various aspects that characterize the behavior of water in food, pharmaceutical, and biochemical systems.

Franzese, Giancarlo; Bianco, Valentino

doi: 10.1007/s11483-013-9310-7pmid: N/A

We analyze the role of water at biological and inorganic interfaces. In fields like food processing, food preservation or bionanotechnology the fluctuations in density and entropy due to hydration water have consequences that go from damaging the tissues to reducing the cell death for dehydration to regulating the food stability to controlling the heat-exchange at the nanoscale. We focus on the thermodynamics of hydration water at cryopreservation temperatures and its effects on the dynamics of nano-confined and protein-hydration water. We consider the relevance of confining heterogeneities for controlling the physical properties of hydration water and the effects of interfacial water on protein stability. To this aim, we describe a coarse-grained model of water that allows us to perform theoretical calculations and numerical simulations, presenting our latest results and the work in progress. Our investigation is at the frontier of knowledge in Physics, Chemistry and Biology, with a potential impact on fields such as Nanoscience, Nanotechnology and Food Science.

Bellavia, Giuseppe; Paccou, Laurent; Achir, Samira; Guinet, Yannick; Siepmann, Jürgen; Hédoux, Alain

doi: 10.1007/s11483-013-9294-3pmid: N/A

We describe a method for analyzing protein hydration by Raman spectroscopy on the model protein lysozyme. The analysis of the protein hydration shell is made possible by dissolving the protein in D2O, providing via isotopic exchange the uncoupled O – H stretching spectrum of water molecules early bound to the protein, which are thereafter spread into the solvent. The spectrum of the hydration water can be obtained by subtracting the spectrum of the contribution of D2O from that of the aqueous lysozyme solution in the intramolecular O – D stretching vibrations region (2,200–2,800 cm−1). Raman investigations were simultaneously carried out in the amide I region (1,500–1,800 cm−1) and in the O – D/H stretching spectrum (3,200–3,800 cm−1) during thermal denaturation of lysozyme, to analyze structural changes of the protein in relation to the physical properties of hydration water. It was found that the H-bond network of hydration water is slightly distorted compared to the bulk water at room temperature, with a loss of the tetrahedral local order. The difference between hydration and bulk water is significantly enhanced at T = 90 °C in the denaturated state of the protein. The quantification of water molecules in direct interaction with the protein provides the temperature dependence of the solvent-accessible surface area during the denaturation process. Both kinds of information on hydration water and protein structure lead to a detailed description and overall understanding of the mechanism of protein denaturation.

Fioretto, D.; Comez, L.; Corezzi, S.; Paolantoni, M.; Sassi, P.; Morresi, A.

doi: 10.1007/s11483-013-9306-3pmid: N/A

The concentration dependence of hydration numbers of molecules modelled as nearly spherical particles is studied by simple analytic and numerical approaches, in the ideal limit of absence of intermolecular interactions. It is shown that the random close-to-contact condition achieved by solute molecules, noticeably affects the average hydration numbers. Comparison with experimental results obtained by light scattering in glucose and trehalose water solutions shows a reduction of the hydration number that is twice faster than that calculated in absence of interactions, suggesting important aggregation phenomena to occur in both systems, even at relatively low solute concentration. The effect of concentration on shear viscosity is also reported, suggesting that the leading contribution to the increase of viscosity arises from hydration water.

Fonzo, Silvia; Masciovecchio, Claudio; Gessini, Alessandro; Bencivenga, Filippo; Cesàro, Attilio

doi: 10.1007/s11483-013-9308-1pmid: N/A

The collective dynamics of concentrated aqueous solutions of the three well-known homologous disaccharides, namely, maltose, sucrose and trehalose, have been studied in an unexplored frequency region by Brillouin ultraviolet light scattering, as a function of temperature and concentration. In trehalose solutions, for water concentrations close to the sugar hydration number, the structural relaxation time above the freezing point of water proves to be 10 % smaller than in maltose/sucrose solutions, presaging a different reorganisation of the sugar matrix. This effect could help in reducing both desiccation stresses and ice formation in anhydrobiotic organisms. The relevance of this behaviour in bioprotection is briefly discussed.

Panagopoulou, Anna; Molina, Joan; Kyritsis, Apostolos; Pradas, Manuel; Lluch, Anna; Ferrer, Gloria; Pissis, Polycarpos

doi: 10.1007/s11483-013-9295-2pmid: N/A

Glass transition and water dynamics in hydrated hyaluronic acid (HA) hydrogels crosslinked by divinyl sulfone (DVS) were studied by differential scanning calorimetry (DSC), dielectric relaxation spectroscopy (DRS) and water sorption—desorption (ESI) measurements. A critical water fraction of about h w = 0.17 (g of water per g of hydrated HA) for a change in the hydration properties of the material was estimated. Water crystallization was recorded by DSC during cooling and heating for water fraction values h w ≥ 0.31. The glass transition of the hydrated system was recorded in the water fraction region 0.06 ≤ h w ≤ 0.59. The T g was found to decrease with increasing hydration level, starting from T g = −48 °C down to about T g = −80 °C and then to stabilize there, for the hydration levels where water crystallization occurs, suggesting that the origin of the glass transition is the combined motion of uncrystallized water molecules attached to primary hydration sites and segments of the HA chains. DRS studies revealed two relaxation peaks, associated with the main secondary relaxation process of uncrystallized water molecules (UCW) triggering the mobility of polar groups and the segmental mobility of HA chains (α relaxation). The α relaxation was in good agreement with the results by DSC. A qualitative change in the dynamics of the α relaxation was found for h w = 0.23 and was attributed to a reorganization of water in the material due to structural changes. Finally, the dielectric strength of the relaxation of UCW was found to decrease in the water fraction region of the structural changes, i.e. for h w ~ 0.23.

Caponi, S.; Mattarelli, M.; Gambi, C.; Rossi, F.; Montagna, M.

doi: 10.1007/s11483-013-9303-6pmid: N/A

The formation of soft colloidal particles in solution and their aggregation process has been studied by Raman spectroscopy. The soft colloidal particles makes up at room temperature by the Sodium Dodecyl Sulfate (SDS) solution over the critical micellar concentration, while the micellar clustering is obtained adding in solution two different ligands: the Kryptofix 2.2.2 (K222) and crown ether 18-Crown-6 (18C6). The chosen ligands molecules are able to interact with the micellar interface inducing the cluster phase formation. Vibrational peaks fingerprints of the micelles formation have been observed and the evidences of the cluster-phase formation have been also achieved in the case of micelles solution doped with the two different macro-cyclic ligands. The ligands action is however different in the two cases as evinced by the careful analysis of the intensity and wavenumber evolution of characteristic Raman peaks at different ligants concentration values. The cluster phase formation and the effects induced on the hydration layer are analyzed showing how Raman spectroscopy is able to gain insight into self-assembly of soft colloidal particles.

Chen, G.; Östlund, Å.; Nordstierna, L.; Swenson, J.

doi: 10.1007/s11483-013-9297-0pmid: N/A

Ice crystals in frozen bread are substantially shaped by the complex pore structures of crumb. In this study we inspected the breadcrumb porosity of ice-filled pores from the profiles of ice crystals mapped by differential scanning calorimetry and nuclear magnetic resonance. Two types of wheat bread containing different amounts of dietary fiber and sugar were studied after frozen storage at −18 °C for 3 weeks. Both pore sizes and pore size distributions were derived via comparing the measurements to those of water-saturated mesoporous silica (MCM-41 C18) with a well-defined pore size distribution. Good consistency was shown for the crumb pore structures obtained using the two techniques. Both bread types featured broad nanometer ranges of pore sizes characterized with largely bimodal size distributions. Besides, the frozen high-fiber bread displayed a higher proportion of large pores and a broader pore size distribution than the high-sugar bread. By comparing such pore size distributions with those obtained previously for the corresponding fresh bread, it can be concluded that structural differences between the two bread types were produced during the frozen storage, manifesting the disparate freezing performances of bread with different formulations.

Tavagnacco, Letizia; Brady, John; Cesàro, Attilio

doi: 10.1007/s11483-013-9290-7pmid: 24000279

Molecular dynamics simulations were carried out on a system of caffeine interacting with the sugar alcohol sorbitol. The system examined had a caffeine concentration 0.083 m and a sugar concentration 1.08 m. The trajectories of all molecules in the system were collected over a period of 80 ns and analyzed to determine whether there is any tendency for sorbitol to bind to caffeine, and if so, by what mechanism. The results show that the sorbitol molecules have an affinity for the caffeine molecules and that the binding occurred by the interaction of the aliphatic hydrophobic protons of the sugar with the caffeine face. This intermolecular association via face-to-face stacking, as suggested by simulation studies, is similar to that found for sucrose and for D-glucose, which overwhelmingly exists in the pyranose ring chair form in aqueous solution, as well as for caffeine-caffeine association. The sorbitol molecules, however, exist as relatively extended chains and are, therefore, topologically quite different from the sugars sucrose and glucose. The comparison of the average conformation of sorbitol molecules bound to caffeine with that of molecules in the free state shows a substantial similarity.