Deep-fat frying : novel stategies for lowering oil uptake and minimising oil quality deterioration

This thesis represents a study on the application of vacuum during post-frying stage with the aim of lowering oil content in fried food. Using potato chips as an illustrative product, several protocols were initially screened, either towards the end of frying or after frying. Lowering the pressure when the product was removed from the oil resulted in a significant reduction in oil uptake. Applying vacuum triggered a continuous water vapour release from the product as a result of lower water saturation temperature, and this prevented the surface oil from penetrating into the product structure. The image generated by con focal laser scanning microscopy showed a visible boundary between the core and the crust regions, and the oil distribution was only concentrated in the crust with insignificant trace of oil in the core region. Despite the amount of oil being absorbed into fried food, the ability of oil to withstand high temperatures at the extended frying period must also be taken into consideration. Interestingly, vacuum drainage significantly inhibited the free fatty acid formation while the total oxidation value was slightly lowered, which in turn showed minimal reductions in the total colour difference value, viscosity and polar compounds. We also explored the possibility of combining moderate vacuum frying with high vacuum drainage to lower the oil uptake in fried food. As expected, high vacuum drainage significantly lowered the amount of oil taken by the potato chips, regardless to the vacuum frying conditions applied. It was also noted that the head space temperature also plays a significant role in the continuous release of water vapour from the product, aside from the product temperature. An attempt to develop fat free product was accomplished when sorbitol was used to substitute oil as frying medium. In sorbitol fried French fries, a crust was formed, similarly to oil fried product and the colour and texture developments were comparableEThOS - Electronic Theses Online ServiceGBUnited Kingdo

Harnessing the energy of molecular recognition in a nanomachine having a photochemical on/off switch

Copyright © 2006 American Chemical Society6A-Deoxy-6A-(N-methyl-3-phenylpropionamido)-beta-cyclodextrin operates as a molecular machine, where the amide group serves as a torsion bar to harness the work output resulting from extraction of 1-adamantanol and consequent complexation of the aryl substituent by the cyclodextrin, when the latter behave as the piston and cylinder, respectively, of a molecular pump. At 25 degrees C, the complexation changes the ratio of the amide (Z)- and (E)-isomers from 2.4:1 to 25:1, on which basis the work performed on the amide bond is calculated to be 1.4 kcal mol-1. trans-6A-Deoxy-6A-(N-methylcinnamido)-beta-cyclodextrin and the cis isomer function as a more advanced version of the machine, with the alkene moiety serving as a photochemical on/off switch. Irradiation at 300 nm converts the trans cinnamide to the cis isomer, while the reverse process occurs at 254 nm. With the cis isomer there is little interaction of the phenyl group with the cyclodextrin cavity, so in that mode the machine is turned off. By contrast, complexation of the aryl substituent by the cyclodextrin occurs with the trans cinnamide and changes the ratio of the amide (Z)- and (E)-isomers from 2.6:1 to 100:1. Consequently, in this mode the machine is turned on, and the work harnessed by the amide bond is 2.1 kcal mol-1.Roger J. Coulston, Hideki Onagi, Stephen F. Lincoln, and Christopher J. Easto

Installation of a ratchet tooth and pawl to restrict rotation in a cyclodextrin rotaxane

The definitive version may be found at www.wiley.comEight new [2]rotaxanes have been prepared, incorporating an -cyclodextrin as the rotor, a stilbene as the axle, and trinitrophenyl substituents as capping groups. Strategies have been devised to elaborate these by linking the rotor to the axle, to produce two new [1]rotaxanes. Rotational motion in a selection of these rotaxanes has been investigated through the application of two-dimensional NMR spectroscopy by performing TOCSY, DQF-COSY, ROESY and HMQC experiments. This has shown that a methoxyl group incorporated on the stilbene and a succinamide joining the stilbene and the cyclodextrin behave analogously to a ratchet tooth and pawl, respectively, to restrict rotation.Hideki Onagi, Christopher J. Blake, Christopher J. Easton, Stephen F. Lincol

Molecular reactors and machines - Applications, potential, and limitations

The definitive version may be found at www.wiley.comMolecular reactors are miniature vessels for the assembly of reactants at the molecular level, in order to change the nature of chemical transformations. It seems probable that those that will find most immediate applications are those that change product ratios or give products which would not readily form in the absence of the reactors, and thereby afford easy access to materials that are otherwise difficult to obtain. Molecular machines consist of interrelated parts with separate functions and perform some kind of work, at the molecular level. Practical examples are likely to be relatively uncomplicated and not based on individual functions of single-molecule devices. Instead they will probably rely on extensive redundancy of the molecular components and their interactions and reactions, as well as of the machines themselves.Christopher J. Easton, Stephen F. Lincoln, Lorna Barr, Hideki Onag

A cyclodextrin-based photoresponsive molecular gate that functions independently of either solvent or potentially competitive guests

The photoinduced interconversion between cinnamido-substituted cyclodextrins constitutes a gating switch through which the substituent moves to open or block access to the cyclodextrin cavity. Most unusually for a cyclodextrin-based device, the operation of this gate is solvent-independent and unaffected by potentially competitive guests. It occurs in MeOH and DMSO, as well as in water. This contrasts with other cyclodextrin inclusion phenomena that are usually driven by hydrophobic effects and limited to aqueous media.Ka-Heng Loh, Nicole M. Smith, Hideki Onagi, Stephen F. Lincoln and Christopher J. Easto

Separated and aligned molecular fibres in solid state self-assemblies of cyclodextrin [2]rotaxanes

The original publication can be found at www.springerlink.comThe conformations of two [2]rotaxanes, each comprising α-cyclodextrin as the rotor, a stilbene as the axle and 2,4,6-trinitrophenyl substituents as the capping groups, have been examined in solution and in the solid state, using ¹H NMR spectroscopy and X-ray crystallography, respectively. In solution, introducing substituents onto the stilbene prevents the cyclodextrin from being localized over one end of the axle. Instead the cyclodextrin moves back and forth along the substituted stilbene. In the solid state, the axles of the rotaxanes form extended molecular fibres that are separated from each other and aligned along a single axis. The molecular fibres are strikingly similar to those formed by the axle component of one of the rotaxanes in the absence of the cyclodextrin, but in the latter case they are neither separated nor all aligned.Hideki Onagi, Benedetta Carrozzini, Giovanni L. Cascarano, Christopher J. Easton, Alison J. Edwards, Stephen F. Lincoln and A. David Ra

Molecular fibers and wires in solid-state and solution self-assemblies of cyclodextrin [2]rotaxanes

Copyright © 2008 American Chemical SocietyCyclodextrin [2]rotaxanes have been prepared by coupling dimethylanilines with dicarboxylic acids using DMT-MM, in aqueous solutions of alpha-cyclodextrin, and the example illustrated shows unusual fluorescence emission and other spectroscopic behavior characteristic of the formation of molecular wires in solution, similar to the fibers observed in the solid state.Subashani Maniam, Marta M. Cieslinski, Stephen F. Lincoln, Hideki Onagi, Peter J. Steel, Anthony C. Willis and Christopher J. Easto

Centrosymmetric and non-centrosymmetric packing of aligned molecular fibers in the solid state self assemblies of cyclodextrin-based rotaxanes

© 2006 Taylor & FrancisTwo [2]-rotaxanes each comprising α-cyclodextrin as the rotor, and with either 3,3′-difluoro- or 3,3′-dichloro-stilbene as the axle and trinitrophenylamino substituents as the blocking groups at the 4- and 4′-positions, were prepared and their structures analyzed in solution and the solid state using 1H NMR spectroscopy and X-ray crystallography, respectively. With each rotaxane, in solution the stilbene rotates freely within the cyclodextrin annulus. In the solid state the 3,3′-dichlorostilbene- based rotaxane adopts two very similar conformations, each having the chlorines in the anti,anti -orientation. By comparison, the 3,3′-difluorostilbene- based rotaxane adopts anti,anti-, anti,syn- and syn,syn-orientations of the substituents. The crystal packing of each rotaxane displays aligned molecular fibers, which are centrosymmetrically orientated in the case of the difluoride due to the head-to-head/tail-to-tail alignment of the cyclodextrins. By contrast, all of the cyclodextrins in the dichloride are aligned head-to-tail along a single axis to give a polar, non-centrosymmetric crystal. © 2006 Taylor & Francis.Marta M., Steel, Peter J., Lincoln, Stephen F., Easton and Christopher

Nitrone [2]rotaxanes: Simultaneous chemical protection and electrochemical activation of a functional group

We report on the use of the hydrogen bond accepting properties of neutral nitrone moieties to prepare benzylic-amide-macrocycle-containing [2]rotaxanes in yields as high as 70 %. X-Ray crystallography shows the presence of up to four intercomponent hydrogen bonds between the amide groups of the macrocycle and the two nitrone groups of the thread. Dynamic 1H NMR studies of the rates of macrocycle pirouetting in nonpolar solutions indicate that amide-nitrone hydrogen bonds are particularly strong, ~1.3 and ~0.2 kcal mol-1 stronger than similar amide-ester and amide-amide interactions, respectively. In addition to polarizing the N-O bond through hydrogen bonding, the rotaxane structure affects the chemistry of the nitrone groups in two significant ways: The intercomponent hydrogen bonding activates the nitrone groups to electrochemical reduction, a one electron reduction of the rotaxane being stablized by a remarkable 400 mV (8.1 kcal mol-1) with respect to the same process in the thread; encapsulation, however, protects the same functional groups from chemical reduction with an external reagent (and slows down electron transfer to and from the electroactive groups in cyclicvoltammetry experiments). Mechanical interlocking with a hydrogen bonding molecular sheath thus provides a route to an encapsulated polarized functional group and radical anions of significant kinetic and thermodynamic stability