Polyphenolic Compounds in Canned Tomato Pastes

SUMMARY– Polyphenolic compounds in canned pastes made from W-14.5 tomatoes ( Lycopersicum esculentum , Mill) were extracted with methanol and ethyl acetate. The compounds. were separated by two-dimensional paper chromatography with n-butanol-acetic acid-water (4:1:5 v/v) and 2% acetic acid as solvents. Twelve spots were found when the chromogenic reagent was FeCl₃K₃Fe(CN)₆. The individual compounds were identified by their R, values and color reactions with Fecl₃K₃Fe(CN)₆, diazotized paranitroaniline, Hoepfner, sodium borohydride, and vanillin-HCI reagents, fluorescent behavior, and absorption spectra. Present in the extracts of tomato pastes were two chlorogenic acid isomers, two caffeic acid derivatives, rutin, naringenin, caffeic acid, and ferulic acid. Naringenin and trans-chlorogenic acid were present in larger amounts than the other polyphenolic compounds.     

Characterisation and evolution of grape polyphenol profiles of Vitis vinifera L. cv. Tannat during ripening and vinification

Background and Aims: Changes in different polyphenol families during grape ripening and vinification were determined in Tannat grapes. This was done to establish a polyphenol profile for Tannat grapes during ripening and for young wines. Methods and Results: We demonstrated, by high‐performance liquid chromatography with diode array detection and mass spectrometry (HPLC‐DAD‐MS) analysis, that the content of flavan‐3‐ols in Tannat seeds was higher than that reported for a large number of other grape varieties analysed. Forty per cent of the total flavan‐3‐ols in seeds were galloylated compounds, whereas the flavan‐3‐ol profile in skins was characterised by the absence of galloylated forms. Prodelphinidins in skins ranged between 30 and 35% with very low values for epigallocatechin. Epicatechin gallate was not detected in Tannat wine and galloylated forms represented a low percentage of total flavan‐3‐ols. Tannat grapes had very high concentrations of anthocyanins in skins with levels increasing during ripening. Eleven phenolic acids were identified in Tannat grape skins and wines, but only gallic and protocatechuic acids were found in the seeds. Conclusions: Tannat wines were shown to have one of the highest levels of phenolic compounds reported for vinifera grape varieties. The profiles for different polyphenol families present in Tannat grapes (skins and seeds) and wines were determined. Significance of the Study: The results presented will help to better understand the phenolic winemaking potential of this variety and its functional properties within food chemistry.     

SOY AND MEAT PROTEINS AS FOOD EMULSION STABILIZERS 1. VISCOELASTIC PROPERTIES OF CORN OIL-IN-WATER EMULSIONS INCORPORATING SOY OR MEAT PROTEINS

The creep compliance-time response of 50% (wt/wt) corn oil-in-water emulsions has been studied at a constant stress of 47.8 dyne cm⁻² over the pH range 2.5–7.5. The emulsions were stabilised by acid precipitated (APSP), 7S(7SPRF) or 11S(11SPRF) soy protein fractions, water soluble (WSMP) or salt soluble (SSMP) meat protein fractions. All the emulsions exhibited viscoelasticity. WSMP emulsions exhibited the highest initial viscoelasticity parameter values and this was attributed to the strong interlinking of WSMP loops adsorbed on the surfaces of adjacent oil drops. The parameter values of all the emulsions increased during the first 5–7 days storage and then they decreased. At any selected pH the 7SPRF emulsions exhibited the largest relative increase in parameter values. The changes in viscoelasticity during storage were explained on the basis of the relative effects of further protein loop interlinkage and drop coalescence.     

SOY AND MEAT PROTEINS AS FOOD EMULSION STABILIZERS 2. INFLUENCE OF EMULSIFICATION TEMPERATURE, NaCl AND METHANOL ON THE VISCOELASTIC PROPERTIES OF CORN OIL-IN-WATER EMULSIONS INCORPORATING ACID PRECIPITATED SOY PROTEIN

The rheological properties of concentrated corn oil-in-water emulsions stabilised by acid precipitated soy protein have been studied as a function of emulsification temperature, methanol and salt concentration. Viscoelasticity parameters were derived from the creep compliance-time response of the emulsions at a constant stress of 47.8 dyne cm⁻². All of the emulsions exhibited higher parameter values, both immediately after preparation and during storage, than comparable emulsions prepared at ambient temperature in the absence of methanol or NaCl. This was attributed to the increased unfolding of adsorbed protein molecules which permits greater interlinking, by hydrophobic bonds, of molecular segments projecting from the surfaces of adjacent oil drops.     

Oxygen Sensors Based on the Electrical Conductivity of the Solid Solutions (Mg1–xFex)O and(Mg1–xCox)O

Solid solutions of general compositions (Mg_{1- x}Fe_x)O and (Mg_1-xCo_x)O (0.05 ≤ x ≤ 0.25) were investigated with regard to the dependence of their specific electrical conductivity on the oxygen partial pressure (10⁻¹⁷≤ po₂≤ 10⁵ Pa) at 900^c and 800°C. The experimental results, especially the slopes of plots of log σ vs log po₂ and the stability of the solid solutions studied, indicate that some of these compositions could be used as oxygen sensors at high temperatures.