Preserving quality of fresh-cut products using safe technologies

Food preservation is critical for keeping the global food supply safe and available for consumers. Food scientists study production and processing to develop new technologies that improve the quality and quantity of healthy food products, with the main objective of increasing food production without affecting food quality and environment, while fulfilling consumer expectations. Nowadays consumers want their food to be fresh, nutritious, safe, and attractive, low priced, and ready-to-eat. That is the case of fresh-cut products; however, maintaining the quality of these products is not an easy task, since minimally processed products experience increased ethylene production and respiration rates, with the consequent lost of quality. New effective and inexpensive technologies to safely preserve the quality of fresh-cut products are needed. In the last two decades, food scientists have attempted to solve problems in fresh-cut processing and quality preservation, and rapid advances in scientific knowledge on fresh-cut product preservation have been developed. The present review describes the use of emerging technologies such as ultraviolet irradiation (UV-C), edible coatings, active packaging and natural additives, to preserve the quality of fresh-cut fruits; highlighting the areas in which information is still lacking, and commenting on future trends.     

Preserving quality of fresh-cut products using safe technologies

Food preservation is critical for keeping the global food supply safe and available for consumers. Food scientists study production and processing to develop new technologies that improve the quality and quantity of healthy food products, with the main objective of increasing food production without affecting food quality and environment, while fulfilling consumer expectations. Nowadays consumers want their food to be fresh, nutritious, safe, and attractive, low priced, and ready-to-eat. That is the case of fresh-cut products; however, maintaining the quality of these products is not an easy task, since minimally processed products experience increased ethylene production and respiration rates, with the consequent lost of quality. New effective and inexpensive technologies to safely preserve the quality of fresh-cut products are needed. In the last two decades, food scientists have attempted to solve problems in fresh-cut processing and quality preservation, and rapid advances in scientific knowledge on fresh-cut product preservation have been developed. The present review describes the use of emerging technologies such as ultraviolet irradiation (UV-C), edible coatings, active packaging and natural additives, to preserve the quality of fresh-cut fruits; highlighting the areas in which information is still lacking, and commenting on future trends.     

Development and characterization of Poly (vinyl alcohol) based hydrogels for potential use as an articular cartilage replacement

Hydroxyapatite (HA) reinforced Poly(vinyl alcohol) (PVA) hydrogel composites has been proposed as a promising biomaterial to replace diseased or damaged articular cartilage. Here, PVA/in-situ produced HA hydrogels with 0, 3 and 7.5 wt.% of HA content were obtained by freezing/thawing technique. Thermal, structural and mechanical characterizations were carried out. SEM micrographs revealed that HA was homogeneously distributed in PVA until 3 wt.% whereas partial agglomeration was observed for higher contents (7.5 wt.%). No significant changes were observed in the glass transition temperature (the average value was near to 78 °C ± 3 °C), the melting point and structural water content whereas the gel fraction slightly increased (from 0.72 to 0.78) with the increase the content of HA. The absorbed water decreased (from 85.7% to 80.5%) as a function of HA content The stress–strain curves were really different in hydrated and non-hydrated conditions, changing from non-linear, in presence of water, to linear behavior in a dried state, being in the first case consistent with the articular cartilage . The lowest friction coefficient was obtained for samples with 3 wt. % HA (0.067 ± 0.049), which is, together with a high resistance (721 ± 25 kPa), an important property for materials that will be used as articular replacement. The results indicate that this hydrogel could be used, after other studies, as articular cartilage replacement.     

Carbon molecular sieve membranes supported on non-modified ceramic tubes for hydrogen separation in membrane reactors

Supported carbon membranes have been regarded as more competitive than traditional gas separation materials due to the versatile combination of different pyrolyzable polymers and supports which in turn leads to high separation factors and mechanical stability. In order to determine the extent to which supported carbon membranes are more competitive, the transport mechanism of supported carbon membranes was investigated in the range 32–150 °C and 1–2.5 bar. Polyimide (Matrimid 5218) material was coated and pyrolyzed under N₂ atmosphere on TiO₂-ZrO₂ macroporous tubes (Tami) that had not been structurally modified in any way. The supported carbon membrane was studied to determine its permeation for low molecular weight gases such as H₂, CH₄, CO, N₂ and CO₂. For these gases, the permeance of the composite supported carbon membranes obtained after pyrolysis at 550 °C increased with inverse square root of molecular weight. The temperature dependence of the permeance was described using an Arrhenius law with the negative activation energies for hydrogen, carbon dioxide and nitrogen providing evidence of a non-activated process. The ideal separation selectivity computed from single gas measurements leads to values slightly lower than the Knudsen because of the influence of viscous flow. The coexistence of more than one transport mechanism in the composite membrane was confirmed. After plugging the possible defects with Polydimethylsiloxane (PDMS), the supported carbon membranes obtained at a pyrolysis temperature of 650 °C showed evidence of a molecular sieving mechanism. This paper shows the separation properties of a crack-free supported carbon membrane obtained using a simple fabrication method that does not require modification of the mesoporous support. The permeance and selectivity values were compared with those of other hydrogen selective materials. Finally, the membranes were applied to methanol steam reforming (MSR).     

Capsaicin accumulation is related to nitrate content in placentas of habanero peppers (Capsicum chinense Jacq.)

BACKGROUND: The presence of capsaicin, the pungent principle of peppers, is restricted to the fruits of hot cultivars. This compound, which is produced in the fruits' placenta, requires 3 mol of nitrogen to be formed. Hence nitrogen availability may affect pepper pungency through its content in the fruit tissues. On the other hand, potassium may also affect pepper pungency given its positive effect on fruit development. In order to address this issue, plants of habanero pepper (Capsicum chinense Jacq.) were hydroponically cultured with various doses of nitrate and potassium and the contents of these ions and capsaicin were analyzed in the different fruit tissues. RESULTS: Treatments did not produce major effects on pod yield or size during the experimental period, and pepper pods from plants growing under low nitrate concentrations presented no significant differences in total nitrate content. However, lower nitrate, as well as low capsaicin contents, were found in the isolated placentas from peppers grown on the lowest nitrate doses. Variations in potassium availability resulted in differences in pod production per plant, but not in capsaicinoid accumulation. CONCLUSION: Under the assayed conditions, nitrate content in the placenta affects capsaicin synthesis. Copyright © 2010 Society of Chemical Industry     

Airmed-cardio: a GSM and Internet services-based system for out-of-hospital follow-up of cardiac patients.

A platform built around three information entities (patient, health-care_agent, and central_station) was designed to enable patients with chronic heart disease (in stable condition; emergency situations were excluded deliberately) to complete specifically defined protocols for out-of-hospital follow-up and monitoring. The patients belonged to one of four specific risk groups: arterial hypertension, malignant arrhythmias, heart failure, and postinfarction rehabilitation. They were provided with portable recording equipment and a cellular phone that supported data transmission [electrocardiogram (ECG)] and wireless application protocol (WAP) (remaining parameters and ad hoc questionnaires). The central station was an automatized platform, with no human operator. The information received was organized chronologically in patient folders. The health-care_agents had continuous and secure access to the patient folders, through tools based on the world wide web and WAP, and to short messages sent by their patients. A pilot project was conducted with 89 patients (mean length of participation: 50.1 days). A total of 2168 ECGs (mean duration transmission = 2 min/30 s; network errors < 0.1%) and 4011 short messages (none lost, in 95% of cases 30 s < delay < 1 min) were transmitted; 6083 WAP sessions (mean duration = 3 min 11 s; network failures < 0.1%) were The functionality of the platform was also evaluated, analyzing the subjective component of usability, showing the evolution of patient acceptance over time.     

Rapid quantitative determination by 13C NMR of the composition of acetylglycerol mixtures as byproduct in biodiesel synthesis

Commercially available partly acetylated glycerols (mono- and diacetin) are mixtures of glycerol, 1- and 2-acetylglycerol, 1,2- and 1,3-diacetylglycerol, and triacetin. Diacetin and monoacetin are by-products of the biodiesel and triacetin production using glycerol esterification with acetic acid or triglyceride interesterification with methyl acetate. Usually, primary analytical methods involve chromatography (HPLC or GC), spectroscopy (MS or NIR), and wet chemical techniques (potentiometric, iodometric titration) which are often time-consuming due to sample preparation, extended analysis time and/or complicated data analysis. Moreover, these methods require pure mono- and diacetin as standard, which are commercially unavailable.In this work, a complete ³¹P and ¹³C chemical shift data for glycerol, mono-, di- and triacetin (including isomers) allows for the identification and quantification of these components in the commercial mixtures. This experimental protocol allows for rapid analysis of mixtures that include these six components. Quantitative ³¹P NMR and ¹³C NMR results were validated to those obtained with other analytical methods, such as GC and HPLC-ELSD. ¹³C NMR is preferred due to allows to measure the content of triacetin, which has no free hydroxyl group, and no signal was detected by ³¹P NMR.     

Taximeter verification with GPS and soft computing techniques

Until recently, local governments in Spain were using machines with rolling cylinders for verifying taximeters. However, the condition of the tires can lead to errors in the process and the mechanical construction of the test equipment is not compatible with certain vehicles. Thus, a new measurement device needs to be designed. In our opinion, the verification of a taximeter will not be reliable unless measurements taken on an actual taxi run are used. GPS sensors are intuitively well suited for this process, because they provide the position and the speed with independence of those car devices that are under test. But there are legal problems that make difficult the use of GPS-based sensors: GPS coordinate measurements do not match exactly real coordinates and, generally speaking, we are not given absolute tolerances. We can not know whether the maximum error is always lower than, for example, 7 m. However, we might know that 50% of the measurements lie on a circle with a radius of 7 m, centered on the real position. In this paper we describe a practical application where these legal problems have been solved with soft computing based technologies. In particular, we propose to characterize the uncertainty in the GPS with fuzzy techniques, so that we can reuse certain recent algorithms, formerly intended for being used in genetic fuzzy systems, to this new context. Specifically, we propose a new method for computing an upper bound of the length of the trajectory, taking into account the vagueness of the GPS data. This bound will be computed using a modified multiobjective evolutionary algorithm, which can optimize a fuzzy valued function. The accuracy of the measurements will be improved further by combining it with restrictions based on the dynamic behavior of the vehicles.     

Highly Efficient Rubrene–Graphene Charge‐Transfer Interfaces as Phototransistors in the Visible Regime

Atomically thin materials such as graphene are uniquely responsive to charge transfer from adjacent materials, making them ideal charge‐transport layers in phototransistor devices. Effective implementation of organic semiconductors as a photoactive layer would open up a multitude of applications in biomimetic circuitry and ultra‐broadband imaging but polycrystalline and amorphous thin films have shown inferior performance compared to inorganic semiconductors. Here, the long‐range order in rubrene single crystals is utilized to engineer organic‐semiconductor–graphene phototransistors surpassing previously reported photogating efficiencies by one order of magnitude. Phototransistors based upon these interfaces are spectrally selective to visible wavelengths and, through photoconductive gain mechanisms, achieve responsivity as large as 10⁷ A W^?1 and a detectivity of 9 × 10¹¹ Jones at room temperature. These findings point toward implementing low‐cost, flexible materials for amplified imaging at ultralow light levels.     

Empirical approximation of Nash equilibria in finite Markov games with discounted payoffs

This paper deals with finite nonzero-sum Markov games under a discounted optimality criterion and infinite horizon. The state process evolves according to a stochastic difference equation and depends on players' actions as well as a random disturbance whose distribution is unknown to the players. The actions, the states, and the values of the disturbance are observed by the players, then they use the empirical distribution of the disturbances to estimate the true distribution and make choices based on the available information. In this context, we propose an almost surely convergent procedure—possibly after passing to a subsequence—to approximate Nash equilibria of the Markov game with the true distribution of the random disturbance.