An improved common-mode feedback loop for the differential-difference amplifier

Unconditional stability of the high-gain amplifiers is a mandatory requirement for a reliable steady-state condition of time-discrete systems, especially for all blocks designed to sample-and-hold (S/H) circuits. Compared to differential path, the common-mode feedback loop is often affected by poles and zeros shifting that degrades the large signal response of the amplifiers. This drawback is made worse in some well-known topologies as the difference-differential amplifier (DDA) that shows non-constant transconductance and poor linearity. This work proposes a body-driven positive-feedback frequency compensation technique (BD-PFFC) to improve the linearity for precision DDA-based S/H applications. Theoretical calculations and circuit simulations carried out in a 0.13 μm process are also given to demonstrate its validity.     

Self-organized Ce(1-x)Gd(x)O(2-y) nanowire networks with very fast coarsening driven by attractive elastic interactions

Assembling arrays of ordered nanowires is a key objective for many of their potential applications. However, a lack of understanding and control of the nanowires' growth mechanisms limits their thorough development. In this work, an appealing new path towards self-organized epitaxial nanowire networks produced by high-throughput solution methods is reported. Two requisites are identified to generate the nanowires: a thermodynamic driving force for an unrestricted elongated equilibrium island shape, and a very fast effective coarsening rate. These requirements are met in anisotropically strained Ce(1-x)Gd(x)O(2-y) nanowires with the (011) orientation grown on the (001) surface of LaAlO(3) substrates. Nanowires with aspect ratios above ≈100 oriented along two mutually orthogonal axes are obtained leading to labyrinthine networks. A very fast effective nanowire growth rate (≈60 nm min(-1)) for ex-situ thermally annealed nanostructures derives from simultaneous kinetic processes occurring in a branched network. Ostwald ripening and anisotropic dynamic coalescence, both promoted by strain-driven attractive nanowire interaction, and rapid recrystallization, enabled by fast atomic diffusion associated with a high concentration of oxygen vacancies, contribute to such an effective growth rate. This bottom-up approach to self-organized nanowire growth has a wide potential for many materials and functionalities.     

A Rapid Size-Exclusion Solid-Phase Extraction Step for Enhanced Sensitivity in Multi-Allergen Determination in Dark Chocolate and Biscuits by Liquid Chromatography–Tandem Mass Spectrometry

Enhanced sensitivity for the simultaneous determination of five nut allergens in biscuit and in dark chocolate complex matrices was obtained by introduction of a rapid size-exclusion solid-phase extraction-based step before liquid chromatography–electrospray ionization-tandem mass spectrometry (LC-ESI-MS²) analysis. A very fast and efficient separation (<12 min) of marker peptides with selected reaction monitoring detection was obtained. Limits of detection in the 0.1–1.3 mg nut/kg and 5–15 mg nut/kg ranges for biscuit and dark chocolate samples as well as high recoveries (84(±6)–106(±4)% for biscuits and 98(±5)–108(±6)% for dark chocolate) proved the excellent capabilities of the exploited sample treatment method combined with the LC-MS² analysis. Good precision in terms of intra- and inter-day repeatability was calculated, being always lower than 19 % (n?=?75). Linearity was demonstrated up to four and three orders of magnitude for biscuit and dark chocolate, respectively. Finally, the validated method was successfully applied to the investigation of hidden nut trace allergens in commercially available biscuits and chocolates of different brands aiming to ascertain possible discrepancies between allergen content and food allergen labelling.     

Modelling the survival of starter lactic acid bacteria and Bifidobacterium bifidum in single and simultaneous cultures

The inactivation kinetics at 4 degrees C of Bifidobacterium bifidum, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, cultured alone or consociated in a laboratory medium (modified MRS broth), were modelled through the Weibull model and a second-order polynomial equation. The initial cell number of S. thermophilus and L. delbrueckii subsp. bulgaricus was approximately 6-7log (CFU/ml); the viability loss after 30 days of storage was 2.87 and 1.99log (CFU/l) for L. delbruckii subsp. bulgaricus and S. thermophilus, cultured alone, respectively; whereas the consociation of lactobacilli and streptococci with bifidobacteria reduced viability loss during storage (0.28 and 0.54log CFU/l for lactobacilli and streptococci, respectively). Finally, the consociation of lactobacilli and streptococci with B. bifidum improved their oxygen uptake.     

Estimation of rheological properties of gelato by FT-NIR spectroscopy

The control of gelato powder mixture production usually is carried out evaluating the gelato liquid phase. The rheological measurements from the present study were conduced on gelato unfrozen liquid phase in order to indirectly evaluate its rheological properties by FT-NIR spectroscopy applied on gelato powders. The calibration set was composed by samples obtained from different recipes having increasing percentage of thickeners, maintaining the proportions of the others compounds constant. After the NIR acquisitions the powders were mixed with warm milk, blended and than settled in order to obtain the unfrozen liquid phase needed for the rheological measurements. For each of the 60 tested recipes three batches with the same thickeners concentration were prepared. The flow curves were obtained with a rotational viscosimeter and were evaluated by using the Ostwald de Waele’s equation and the goodness of fit was evaluated by the R², which was above 0.95. Predictive models of rheological parameters were set up by means of PLS regressions in order to predict the apparent viscosity (η), the consistency coefficient (K) and the flow behaviour index (n) from spectral acquisitions. A high correlation of calibration was found between NIR spectra and apparent viscosity with R² of 0.943. A good correlation was also found between the NIR spectra and the consistency coefficient (K) and flow behaviour index (n), with a determination coefficient (R²) of 0.895 and 0.874, respectively.The good prediction of the models encourages applying them to reduce significantly the time of the powder mixing control during production.     

Effect of ultrasound treatment on properties of gluten-based film

Gluten films obtained in acid conditions display some protein dispersion difficulties. Ultrasound treatment (UT) could represent an interesting strategy for improving gluten film appearance. Different UT exposure times were applied to film-forming dispersion. The aim of this work was to investigate the effect of ultrasound treatment on gluten-based films at molecular and mesoscopic levels. Distribution in gliadin and glutenins was determined with SE-HPLC. The UT improved protein dispersion and final film appearance. Sonication did not lead to large changes in various gluten fractions, which suggests absence of important protein breakdown at the molecular level. Gluten showed high tolerance to UT. Surface properties of untreated and treated films were investigated by contact angle measurement: sonication promoted hydrophilic surface properties.Industrial relevanceBio-based packaging has been receiving increasing attention in view of its beneficial impact on the environment. Among proteins, gluten resulted as a very interesting film-forming material. Gluten films prepared in acid conditions showed problems in protein dispersion. Sonication represents a physical strategy which allowed us to obtain gluten-based films without the addition of chemical additives, such as sodium sulphite.     

Rapid and Simultaneous Analysis of Xanthines and Polyphenols as Bitter Taste Markers in Bakery Products by FT-NIR Spectroscopy

The food industry has a direct interest into bitter-tasting substances either for the identification of negative off-flavors or for the monitoring of a desired organoleptic quality. A rapid technique, based on Fourier transform-near infrared (FT-NIR) spectroscopy and able to detect taste molecular markers in bakery commodities, was developed, focusing the attention on biscuits category. Xanthines (caffeine, theobromine, and theophylline) and polyphenols (catechins and epicathechins), considered as mainly responsible for the bitter-taste of coffeecocoachocolate based products, were firstly checked using a confirmatory liquid chromatography (LC)-ESImass spectrometry (MS)-MS procedure after hot methanol–water extraction. Correspondent data were used for the calibration of the FT-NIR through PLS regression. Values of the standard errors of prediction (lower than 10 %) were comparable to the values of the standard errors of cross-validation. Coefficients of determination indicated a good predictive power in the calibration model (R ² xanthines?=?0.97, R ² polyphenols?=?0.96) and a satisfying discriminating power among different contents in the validation models (R ² xanthines?=?0.96, R ² polyphenols?=?0.96). A testing phase on the generated model was executed by a comparison of LC-MS and sensory panel data with FT-NIR responses recorded on unknown biscuits: differences between found and predicted levels were generally below 5 % and the best predictability was achievable in chocolate-based biscuits. This methodology is able to work directly on solid products, has the potential to be expanded on other categories of gustative molecular markers (like sugars) and can be conceived as applicable for a routine control of a standardized bitter taste quality in a real industrial production.     

Classification of juices and fermented beverages made from unripe,ripe and senescent apples based on the aromatic profile using chemometrics

The aim of this study was to assess differences between apple juices and fermented apple beverages elaborated with fruits from different varieties and at different ripening stages in the aroma profile by using chemometrics. Ripening influenced the aroma composition of the apple juice and fermented apple. For all varieties, senescent fruits provided more aromatic fermented apple beverages. However, no significant difference was noticed in samples made of senescent or ripe fruits of the Lisgala variety. Regarding the juices, ripe Gala apple had the highest total aroma concentration. Ethanal was the major compound identified in all the samples, with values between 11.83 mg/L (unripe Lisgala juice) and 81.05 mg/L (ripe Gala juice). 3-Methyl-1-butanol was the major compound identified in the fermented juices. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied and classified the juices and fermented juices based on physicochemical and aroma profile, demonstrating their applicability as tools to monitor the quality of apple-based products.     

Exploitation of Polyphenolic Extracts from Grape Marc as Natural Antioxidants by Encapsulation in Lipid-Based Nanodelivery Systems

Phenolic compounds were extracted from grape marc by means of high pressure and temperature extraction. In order to increase their dispersability in the aqueous phase, the polyphenolic extracts were encapsulated at a final concentration of 0.1 % (w/w) in nanoemulsion-based delivery systems, which were formulated with natural ingredients, using either a liquid (sunflower oil) or a solid (palm oil) lipid phase, as well as the combination of a hydrophilic and hydrophobic emulsifier, and were produced by high-pressure homogenization. The delivery systems were characterized in terms of physicochemical stability under accelerated ageing (storage at 4 °C, 30 °C, and 55 °C for 14 days), by recording the evolution of the mean droplet size, the creaming index as well as the UV–vis absorption spectra of the encapsulated polyphenols. The antioxidant activity of the encapsulated extracts was measured with two different chemical assays (FRAP and ORAC) and a cellular antioxidant assay. Sunflower oil-based nanoemulsions resulted to be the most physically and chemically stable, with no significant variation of the mean droplet size and no degradation of the encapsulated compounds under the different conditions tested. The FRAP and ORAC assays showed that the antioxidant compounds, when encapsulated, are as available as unencapsulated polyphenols in scavenging the peroxyl radicals (ORAC), but are less available in reducing the ferric tripyridyltriazine complexes (FRAP). Remarkably, the cellular antioxidant activity was significantly higher for the encapsulated grape marc polyphenols than for the unencapsulated ones, suggesting the fundamental role of the nanoemulsions in favoring the delivery through the biological membranes.