No abstract

Controlling the quality of cheese involves monitoring its taste, texture, stability and appearance. One method of doing so involves the analysis of cheese microstructure. This research investigated the use of confocal Raman microscopy for observing the microstructure of processed cheese including the distribution of additives therein. Reference Raman spectra were obtained for several additives commonly present in processed cheese including: trisodium citrate (TSC), sorbic acid, paprika and corn starch. Low and high spatial resolution Raman images were obtained from commercial and custom formulated processed cheeses. These were created using band integrals and principal component analysis scores values. Results of this investigation show that fat, protein, water, TSC, paprika and starch distributions can be imaged effectively using the many Raman imaging methods, including high spatial resolution Raman microscopy. Copyright © 2016 John Wiley & Sons, Ltd.

A highly efficient synthesis of 2-formyl-5,10,15,20-tetraarylporphyrins, 1 and 2, that can be carried out on multi-gram scales is reported. The key steps in the sequence involve use of copper(II) chelation to ensure very efficient electrophilic substitution, and the demetalation of the intermediate iminium salt that results from Vilsmeier-Haack formylation of the copper(II) porphyrins prior to base-catalyzed hydrolysis of the salt to the corresponding free-base 2-formylporphyrin. This sequence avoids the formation of by-products that inevitably result when the formyl group is subjected to acidic conditions. Borohydride reduction of (metallo)-2-formylporphyrins give the corresponding 2-hydroxymethyl-porphyrins in quantitative yield. Catalytic reduction of copper(II) 2-hydroxymethyl-5,10,15,20-tetraphenylporphyrin 15 with hydrogen under acidic conditions affords 2-methyl-5,10,15,20-tetraphenylporphyrin 20 in 60% yield. Treatment of 2-hydroxymethyl-porphyrins with thionyl chloride in dry pyridine yields the corresponding 2-chloromethyl-porphyrins in good yields. The 2-chloromethyl-porphyrins give the corresponding triphenyl[(porphyrin-2-yl)methyl]phosphonium chlorides in 90% yield on treatment with PPh 3 in boiling chloroform. These salts are useful building blocks for the synthesis of conjugated porphyrin dimers and higher oligomers.

The reaction of ((tetraphenylporphyrinyl)methyl)triphenylphosphonium chloride and benzaldehydes (CHO−C6H4−R; R = H, NO2, NMe2, OMe, Me, CHO) yields the styryl porphyrin derivatives. These new styryl-substituted porphyrins have been studied using electrochemistry, electronic absorbance, and resonance Raman spectroelectrochemical techniques. The substituents on the styryl group have a modest perturbation on the electronic spectrum of the porphyrin core. The resonance Raman data suggest that a charge-transfer interaction is observed between the porphyrin core and the NO2 group for the 4-NO2 compound.

A building block approach towards porphyrin arrays is used to construct pentameric and nonameric porphyrin arrays in one step.