Alessandro Parenti

Electrochemical sensor and biosensor for polyphenols detection in olive oils.

Abstract The aim of the work was to compare different techniques, in evaluating the phenolic content of an extra-virgin olive oil with varying storage time and storage conditions. A disposable screen-printed sensor (SPE) was coupled with differential pulse voltammetry (DPV) to determine the phenolic fractions after extraction with a glycine buffer; DPV parameters were chosen in order to study the oxidation peak of oleuropein, which was used as reference compound. A calibration curve of oleuropein was performed in glycine buffer 10 mM, pH=2, NaCl 10 mM (D.L.=0.25 ppm oleuropein, RSD=7%). Moreover a tyrosinase based biosensor operating in organic solvent (hexane) was also assembled, using an amperometric oxygen probe as transducer. The calibration curves were realised using flow injection analysis (FIA) with phenol as the substrate (D.L.=4.0 ppm phenol, RSD=2%). Both of these methods are easy to operate, require no extraction (biosensor) or rapid extraction procedure (SPE), and the analysis time is short (min). The results obtained with these two innovative procedures were compared with a classical spectrophotometric assay using Folin–Ciocalteau reagent and HPLC analysis. Other extra-virgin olive oil quality parameters were investigated using classical methods in order to better define the alteration process and results are reported.

A Predictive Classification Model for the Management of Virgin Olive Oil Filtration at Industrial Scale

Precoat-bodyfeed filtration of virgin olive oil was investigated on an industrial filter-press plant. Several chemical parameters of the unfiltered oil were measured and the relationship with filtration performances was investigated by Principal Component Analysis. Further, Linear Discriminant Analysis was applied to develop a predictive model for oil filterability. Principal Component Analysis allowed the construction of latent variables which were used to separate oil groups and to select variables for Linear Discriminant Analysis. The developed linear model gave an overall correct recognition of about 88%, good enough for a convenient filterability prediction of oil at industrial scale.

A Condenser to Recover Organic Volatile Compounds during Vinification

Escape of carbon dioxide during grape must fermentation leads to loss of volatile compounds, which ultimately affects the wine’s aroma. An innovative condensation device was designed to trap organic volatile compounds that would otherwise be lost. Trials were performed using Sangiovese and Syrah grapes and involved continuous condensation of vapor (condensed fractions, CFs) that escaped from fermentation tanks. Ethanol content and volatile compound composition of CFs were measured daily since 48 hr after the fermentation began. An average of 1.3 g CF per kg fermenting must was recovered, corresponding to a theoretical yield of ~0.37% of condensed product. Mean ethanol content was ~24% by volume, and the total concentration of organic volatile compounds was ~1200 mg/L. Predominant compounds were alcohols and esters of secondary origin, with four compounds (ethyl octanoate, 1-propanol, ethyl acetate, and 2, 3-butanediol) accounting for more than 88% of the final concentration. The CF volatile profile changed as a function of fermentation time. For sensory evaluation, CFs were added back to their respective wines and were statistically shown to be detectable at a rate of 1‰.

Stabilization of Extra-Virgin Olive Oil

The conservation of virgin olive oil quality during its shelf life could be considered a key issue for olive oil industry. To improve the product stability, virgin olive oils should not be stored with considerable amounts of suspended solids and water. The latter have to be removed from oil musts. The chapter reviews the main spread technologies and those recently proposed for the removal of suspended solids and the water from extravirgin olive oils. These technologies are described from an engineering perspective, and their effects on product quality during storage are discussed.

Characterization and comparison of cold brew and cold drip coffee extraction methods: Cold brew and cold drip coffee extraction methods

BACKGROUND Each region of the world has its own methods, protocols, instruments and procedures regarding how to brew coffee. The final result in the cup is strongly affected by the extraction method, and many studies have focused on this subject. However, few studies have investigated slow, cold extraction methods, despite their popularity among baristas. Therefore, the present study aimed to characterize and compare two cold extraction methods: cold brew and cold drip. RESULTS Physical and chemical analyses were used to describe coffee beverages in terms of pH, total solids, refractive index, density and viscosity. Caffeine and cinnamic acids were quantified using high-performance liquid chromatography (HPLC)/diode array detector and HPLC/mass spectrometry. A sensory evaluation included aroma, flavor and textural attributes. CONCLUSIONS Significant differences were found in the chemical and physical parameters, both between and within the two methods, as a function of the extraction temperature and contact time. Similarly, the sensory evaluation found differences in flavor profiles, as measured in terms of bitterness, sweetness, sourness and global intensity.

A Technological Solution to Modulate the Aroma Profile during Beer Fermentation

During the production of fermented alcoholic beverages, such as wine or beer, the loss of aroma active compounds (AACs) has a significant impact on the overall product aroma. This paper presents the results of an experimental technique in which a condenser was placed on the top of the fermenter in order to reduce such losses. AAC concentrations in beers produced in this way were compared with a control produced without a condenser. There were two main findings: (i) some AACs could be recovered during fermentation and (ii) the technique stimulated the de novo synthesis of esters from carboxylic acids and alcohols. In particular, the production of ethyl esters from the reaction between ethanol and organic acids and the production of acetates from the reaction between acetic acid and alcohols were demonstrated. Consequently, the addition of the condenser changed the final aroma of the beverage. The effect was confirmed by a panel test and AAC quantitation using HS-SPME-GC-MS. The technique could be used by brewers as a tool to modulate the flavor and aroma of beer.

What kind of coffee do you drink? An investigation on effects of eight different extraction methods

The chemical composition of brewed coffee depends on numerous factors: the beans, post-harvest processing and, finally, the extraction method. In recent decades, numerous coffee-based beverages, obtained using different extraction techniques have entered the market. This study characterizes and compares eight extraction coffee methods from a chemical-physical point of view, starting from the same raw material. Specifically, three types of Espresso, Moka, French Press, and 3 filter coffee that for the first time are reported in the scientific literature Cold Brew, V60, and Aeropress are compared. Physical measurements included the quantification of total dissolved solids, density, pH, conductivity, and viscosity. Chemical analyses identified 15 chlorogenic acids (CGAs): six caffeoylquinic acids, one p-Coumaroylquinic acid, one Feruloylquinic Acid, four Caffeoylquinic lactones, and three Dicaffeoylquinic acids. Maximum caffeine and CGA concentrations were found in Espresso coffees, while Moka and filtered coffees were three to six times less concentrated. The classic Espresso method was most efficient for caffeine and CGA recovery, with a yield almost double that of other methods. Per-cup caffeine and CGAs were higher in Cold Brew than Espresso coffees, as a function of the volume of beverage, which ranged from 30 mL (for espresso) to 120 mL (for filtered coffees). In light of these results, it is not possible to establish how many cups of coffee can be consumed per day without exceeding the recommended doses, since according to the applied brewing method, the content of the bioactive substances varies considerably.