Spectroscopy analysis of phenolic and sugar patterns in a food grade chestnut tannin.

Tannin of chestnut (Castanea sativa Mill.) wood, commonly used in winemaking was characterised with a spectroscopy qualitative approach that revealed its phenolic composition: several vibrational diagnostic bands assigned using the Attenuated Total Reflectance-Infrared Spectroscopy, and fragmentation patterns obtained using the Laser-Desorption-Ionization Time-of-Flight technique evidenced polygalloylglucose, e.g. castalagin/vescalagin-like structures as the most representative molecules, together with sugar moieties. The implication of these findings on winemaking application and the potential influence of the chemical structure on the sensory properties of wine are discussed.

Comparison of two quantitation methods in HPLC: standardless versus calibration with external standards. Application to the analysis of amino acids in fruit juices.

A distinctive method of high-performance liquid calibration peak-area quantitation, called the standardless or absolute method, allows the absolute number of moles of the main amino acids found in twenty-six commercial fruit juices to be determined. The theory of the standardless model is briefly illustrated. The results found with this alternative method are compared with the reference procedure (calibration with external standards) by using difference plots and regression analysis. The presence of both systematic, constant, and proportional errors between the two methods is disclosed and discussed.

High-performance liquid chromatographic analysis of free amino acids in fruit juices using derivatization with 9-fluorenylmethyl-chloroformate.

A simple, rapid, and reliable reversed-phase high-performance liquid chromatographic method for the analysis of 16 amino acids of main interest in commercial fruit juices (pear, orange, grapefruit, pineapple, peach, and apricot) is described. No sample cleanup is required. The pH of the fruit juices is adjusted to alkaline value (8.5) using 200 mM borate buffer, then amino acid is converted to stable derivatives using 9-fluorenylmethyl-chloroformate. The excess of derivatization reagent is removed by a hydrophobic amine, 1-amino-adamantane hydrochloride. The derivatization procedure is simple, fast, and described in detail. Amino acids are detected at 263 nm and eluted within 35 min. The calibration, precision (< or = 6.1%), and recovery (102% +/- 4%) of the method are reported. The conditions of separation are optimized; however, serine partially overlapped with aspartic acid. The amino acid profile of fruit juices is consistent with data from the literature.

Stilbene compounds and stilbene synthase expression during ripening, wilting, and UV treatment in grape cv. Corvina.

The content of selected phenolic compounds including resveratrol (trans-3,5,4'-trihydroxystilbene) and its cis-isomer and glucosides (piceides) were monitored in grape (Vitis vinifera L. cv. Corvina) berry skin during ripening in the vineyard and in response to the post-harvest drying process (wilting). Four wilting conditions were compared (traditional, mixed, low-temperature, and high-temperature) to verify the eliciting effect of drying on resveratrol production. During fruit ripening the cis-piceid was the major stilbene found in berry skins, and a weak accumulation of stilbene synthase (STS) mRNA was observed, whereas UV-light irradiation greatly stimulated STS transcript of unripe berries. A time-course experiment showed the highest STS mRNA accumulation and resveratrol content (34 microg/g fresh weight at 58 days) occurring in berry skins in a mixed wilting process.

Removal of ochratoxin A in red wines by means of adsorption treatments with commercial fining agents.

The presence in wine of the fungal metabolite, ochratoxin A (OTA), represents a serious risk for consumer health. A variety of fining agents, including activated carbon, silica gel, potassium caseinate, egg albumin, and gelatin, was evaluated in relation to their abilities to remove OTA in fortified wines. Freundlich adsorption isotherms were used to model the adsorption behavior between ochratoxin A and the fining agent. Potassium caseinate and activated carbon were found to be the best fining agents that could be used to remove OTA in wine. Potassium caseinate removed up to 82% of OTA when used at 150 g/hL, whereas activated carbon showed the highest specific adsorption capacity due to a high surface area per mass and low adsorption of total polyphenols.

A simple high-performance liquid chromatography method for the analysis of glucose, glycerol, and methanol in a bioprocess.

A reliable high-performance liquid chromatography-refractive index detection method for the simultaneous analysis of glucose, methanol, and glycerol in a bioprocess fermentation media using direct injection is presented. The validation studies show a satisfactory selectivity, linearity, accuracy, and recovery of the method. The lowest concentration detectable for glucose and methanol is 3.5 and 6.7 mg/100 mL, respectively. This method could be an attractive choice for the analysis of these compounds not only in fermentation media but also in biomedical and environmental samples.

Phloretin glycosides: bioactive compounds in apple fruit, purées, and juices.

ABSTRACT Phloretin glycosides are bioactive compounds naturally present in apple fruits. The highest amount of phloretin glycosides was significantly found in apple pureées and commercial juices as a consequence of the processing conditions.