Sergio Galassi

AN IMPROVED HPLC METHOD FOR THE ANALYSIS OF ORGANIC ACIDS, CARBOHYDRATES, AND ALCOHOLS IN GRAPE MUSTS AND WINES

An improved high performance liquid chromatography (HPLC) method for the analysis of the main organic compounds in musts and wines is presented. A column packed with hydrogen sulfonated divinyl benzene-styrene copolymer and two detectors connected in series were used (UV at 210 nm and RI, respectively). The addition of acetonitrile (6%) to the mobile phase (0.045N H2SO4) allowed the simultaneous separation and quantification of several organic acids, glucose, fructose, glycerol, and ethanol. Direct injection and sample clean-up with a SAX cartridge was tested and compared. The SAX fractionation gave satisfactory results, however the direct injection of diluted wine (1:20) provided the best precision (CV ≤ 2.1%) and accuracy of analysis. Statistical analysis (paired t-test) disclosed significant differences only for glucose, fructose, α-ketoglutaric, and pyruvic acid. The role of column temperature for the analysis of vitamin C (ascorbic acid) was also investigated. Vitamin C underwent thermal degradation during analysis with column temperature ≥ 30°C.

Level of single bioactive phenolics in red wine as a function of the oxygen supplied during storage.

Abstract The influence of three levels of oxygen supply on the phenolic composition of Sangiovese wine was evaluated during 6 months of storage. Oxygenation reduced the total phenolics content and increased the concentration of red polymeric compounds. Saturation with oxygen every 30 days significantly improved the wine colour density as compared to the control. The individual behaviour of phenolic compounds such as (+) catechin, (−) epicatechin, quercetin, caffeic acid, and anthocyanins showed a significant depleting effect of oxygen on wine phenolic composition when wines were oxygenated every month. The supply of oxygen every 60 days limited the oxidation of low molecular weight phenolic compounds and slightly influenced the wine colour. This confirmed that oxygenation could improve the evolution of red wines during ageing, but its control is necessary to reduce detrimental effects upon single bioactive phenolic compounds.

A preliminary comparison between nanofiltration and reverse osmosis membranes for grape juice treatment

Abstract Nanofiltration (NF) and reverse osmosis (RO) systems were compared using grape juice as feed solution. The initial permeate flux (J) was 7.4, 8.1, and 1.7 dm 3 m −2 h −1 with NF membranes DS and DK, and RO membrane SWC, respectively. The exponential decay of J in the above NF and RO membranes was characterized by a fouling index equal to 0.16, 0.22, and 0.24, respectively. The permeability of NF membrane DS doubled by increasing the working pressure from 32 to 45 bar. Despite the additional power (+30%) required to work at the higher pressure value there was an energy saving per unit permeate of approximately 35%. The working pressure and temperature affected the selectivity of NF membranes. As expected, a direct relationship between membrane permeability and working temperature occurred; the permeate flux of NF membrane DS increased by about 3% per degree of temperature rise.

Characterisation of peach juices obtained from cultivars Redhaven, Suncrest and Maria Marta grown in Italy

Abstract The compositions of three peach juices obtained from the cultivars Redhaven, Suncrest and Maria Marta, respectively, were studied. The fruits were grown in the Emilia-Romagna region (Italy). The juices were characterised by pH, CIE L *, a *, b * colour values, soluble solids, individual carbohydrates, organic acids, and phenolic compounds. Univariate analysis disclosed some significant differences among the compositions of the varietal peach juices. Principal component revealed clear group structures in the data matrix, the most relevant variables being glucose, fructose, sorbitol, malic acid, L * and b *-values. Suncrest peach juice was clearly distinguished from Redhaven and Maria Marta juices.

Rapid analysis of ascorbic and isoascorbic acids in fruit juice by capillary electrophoresis

Abstract The application of capillary zone electrophoresis with UV–VIS and diode array detection for simultaneous analysis of l -ascorbic and d -isoascorbic acids was investigated. The method of analysis was simple, fast and its performance was tested in terms of linearity, sensitivity and detection limit. Twenty-six samples representative of three types of apricot commercial juices (organic, integrated and conventional) were analysed for their ascorbic acid content and data were reported (range n.d.–486 mg/l).

Concentration of Grape Must by Nanofiltration Membranes

In this study the selectivity of two nanofiltration (NF) membranes was tested with the aim of increasing the sugar content of grape must used for wine production. The composition of grape must, concentrate, permeate and the rejection values for selected physicochemical parameters is presented. In particular, the NF membranes provided a high rejection for sugars (range 77–97%), whereas the malic acid was retained to a low extent (range 2–14%). A two-stage NF process of grape must remove a permeate volume of 14%, thus allowed concentration of the sugars, i.e. the potential alcohol, to ca. 16%. The wine obtained from a grape must treated by NF membrane was high in total plyphenols and DO (optical density) at 420 nm.

HPAEC–PAD analysis of oligogalacturonic acids in strawberry juice

Abstract High performance anion-exchange chromatography (HPAEC), coupled with pulsed amperometric detection (PAD), was used to identify and quantify oligogalacturonic acids (OGAs) in strawberry juice. This method allowed good separation and detection of OGAs with degree of polymerization (DP) ® MAX enzyme, for 2 h at 45°C, produced juice with by far the highest concentration of OGAs. Moreover, treatment with Grindamyl Pectinase ™ LM was also extended to 4 and 6 h to measure the time course of pectinase activity and verify the stability of OGA. This enzyme generated high levels of pectin breakdown products proportionately with time (monitored up to 6 h) and increased the total level of OGAs with DP ⩾4 units from 78 to 771 mg/l. ©

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.

The determination of total SO2 in grape juice. A comparison among five methods

The EC official method of total SO2 analysis in grape juice was modified in 1990. The main improvements concerned the amount and concentration of H3PO4 used during the distillation to recover the combined SO2 and the standardization of the distillation time at 15min. This comparative study evaluated the total SO2 level of 12 grape juices determined by five methods, including distillation, iodimetric and enzymatic-based methods. Attention was focused on the total SO2 legal limit of 10mg/l fixed in Europe for grape juice. Analysis of variance disclosed a significant difference among the total SO2 content in grape juices determined by five methods. Each analytical method showed limits in relation of their ability to release the combined SO2. In particular, the SO2 bonded to phenolic compounds is partially released at low pH in the acidified juice leading to higher results.

Characterization of Uva Longanesi Red Wine by Selected Parameters Related to Astringency

This research represents a first attempt to chemically characterize wines produced from the autochthonous grape variety, Uva Longanesi, based upon the phenolic compounds responsible for its high astringency as confirmed by preliminary sensory analysis. In addition, a wine produced from Sangiovese, the most popular grape variety in the Emilia-Romagna region, was analyzed for comparative purposes. Results showed that Uva Longanesi wine had a higher pH, alcohol concentration, and total dry extract than the Sangiovese wine. With regards to phenolic constituents, the Uva Longanesi wine had higher color parameters and greater concentrations of total phenolics, including monomeric anthocyanins, small polymeric pigments, and tannins. The phenolic composition of Uva Longanesi wine was found to be responsible for the high reactivity of the wine during fining trials.