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Summary This study reports the characterization of the Tetrasphaera duodecadis bacteria and the techniques used therein. In order to evaluate the morphological characteristics of the T. duodecadis bacteria scanning electron microscope (SEM) was used throughout its different growth stages. These microorganisms were grown in vitamin B12 broths with 1% tryptone, 0.2% yeast extract, and 0.1% glucose. The turbidimetric method was employed for the determination of bacterial concentration and growth curve. The SEM results show small agglomerates of 0.8 ± 0.05 µm during the lag phase, and rod‐like shapes during the exponential phase with similar shapes in the stationary phase. SCANNING 36:547–550, 2014. © 2014 Wiley Periodicals, Inc.

In this study, low density and high porosity aerogels were produced through freeze drying of cellulose nanofiber (CNF) dispersions with 0.6, 0.9 and 1.2 wt% concentration and modified via chemical vapor deposition (CVD) of hexadecyltrimethoxylan (HDTMS) to absorb and remove oil and organic pollutants from the water. Aergels were evaluated by density and porosity measurement, BET analysis, scanning electron microscopy, contact angle, oil absorption capacity and mechanical tests. The densities of unmodified and modified aerogels were in the range of 8.0–13.8 and 11–17.5 mg cm −3 , respectively. The porosities of aerogels, before and after modification, were 99.1–99.5 and 98.8–99.3%, respectively. The porous structure formation via successful self assembling of CNF was also evidenced by the scanning electron microscopy images. All of the modified aerogels, regardless of the initial CNF concentration, had contact angle values greater than 90° and were classified as hydrophobic materials. The 0.6% sample revealed the highest adsorption capacities of 78.8 and 162.4 g g −1 for motor and cooking oils, respectively and the 1.2% aerogel exhibited the maximum values of stress and Young’s modulus in compression test. The results of this investigation indicated that ultra-light, hydrophob and superabsorbent materials based on chemically modified cellulosic aerogels with this type of silanated material were successfully produced. Graphical abstract

This study focused into vacuum freeze dryer technology for increasing food shelf life in a drying food technology. The determinants of energy consumption increase as the energy density of food production and storage increases. Reducing the amount of energy used for drying, freezing, chilling, refrigeration, and air conditioning is becoming more important. The objective of this study was to extend food’s shelf life utilizing creative and novel technical approaches, such as vacuum freeze-drying’s energy-efficient process. Despite being a part of this investigation, the vacuum freeze drier was created using environmentally benign energy sources. To minimize the carbon footprint of food preservation, it is essential to use eco-friendly energy sources in chilling storage. According to the first law of thermodynamics, the energy efficiency at 1 atm pressure and 25 [°C] temperature (neglecting potential and kinetic energies) in the dead state is calculated under thermal equilibrium conditions. In this study, the energy efficiency was shown according to 5 different scenarios. The results of energy efficiencies are as follows: η 1 is from 14.3 to 21.4%, η 2 is from 20.7 to 31.0%, η 3 is from 27.3 to 40.9%, η 4 is from 32.1 to 48.1%, and η 5 is from 34.6 to 51.9%, respectively. This analysis demonstrates that the energy efficiency improved from 12 to 18 h. In this study, optimizations with scenarios were employed considering vacuum freeze-drying technology in the plant with sustainable energy sources can considerably improve food shelf life while limiting our environmental impact.

Drying uniformity, microstructure, apparent density, rehydration, and texture properties were measured to evaluate the quality of stem lettuce slices dried in a pulse-spouted bed microwave freeze dryer. Drying was carried out in a 5-cm (o.d.) vacuum chamber at 80 ± 5 Pa, mean microwave power level of 3.2 W g −1 and pulse-spouting time interval of 10 min. Results show that microwave freeze-dried products in the pulse-spouted mode dried more uniformly as compared to those dried in steady spouted bed mode. Pulse-spouted bed mode also resulted in dried stem lettuce slices with lower discoloration, more uniform and compact microstructure, higher rehydration capacity (RC) as well as greater hardness after rehydration over shorter drying time relative to those obtained in a steady spouting condition.

The effects of novel Pulse-Spouted Bed Microwave Freeze Drying (PSMFD) technology on the quality on natural food products have been investigated. The objective of this research was to study effects of this novel technology on dielectric properties and quality characteristics (moisture content, porosity, microstructure, texture, color, and flavor) of apple cuboids as compared with the conventional drying technologies (air drying and freeze drying). During the first 45 min of drying, the dielectric properties increased due to partial conversion of water from ice to liquid, and then gradually decreased due to the moisture removal. Microwave energy increased sample temperature from minus 20 °C to + 67 °C, which resulted in fast drying to 0.09 g/g within 270 min. Porosity increased almost linearly, reaching 0.87 at equilibrium moisture content. Hardness of apple cuboids increased to 350–450 kPa due to the glass transition in the final period of drying. Better preservation of apple color and volatile compounds demonstrated the benefits of the hybrid PSMFD technology for the production of premium quality dried fruits compared to air drying and freeze drying.

In this paper, a novel nanocrystalline composite material of hydroxyapatite (HA)/polyvinyltrimethoxysilane (PVTMS)/iron(II)chloride tetrahydrate (Cl2FeH8-O4) with hexagonal structure is proposed for the fabrication of a gas/temperature sensor. Taking into account the sensitivity of HA to high temperatures, to prevent the collapse and breakdown of bonds and the leakage of volatiles without damaging the composite structure, a freeze-drying machine is designed and fabricated. X-ray diffraction, FTIR, SEM, EDAX, TEM, absorption and photoluminescence analyses of composite are studied. XRD is used to confirm the material structure and the crystallite size of the composite is calculated by the Monshi–Scherrer method, and a value of 81.60 ± 0.06 nm is obtained. The influence of the oxygen environment on the absorption and photoluminescence measurements of the composite and the influence of vaporized ethanol, N2 and CO on the SiO2/composite/Ag sensor device are investigated. The sensor with a 30 nm-thick layer of composite shows the highest response to vaporized ethanol, N2 and ambient CO. Overall, the composite and sensor exhibit a good selectivity to oxygen, vaporized ethanol, N2 and CO environments.

Freeze-drying is an excellent method for dehydration due to its benefits, including increased shelf-life, unique texture, and, in particular, good nutritive quality. However, the applicability of traditional freeze-drying systems in the food industry is still challenging owing to their prolonged drying duration, extraordinary energy usage, and high process cost. Therefore, the need to upgrade or develop conventional freeze-dryers for common or sophisticated food structures is ever-increasing. Enhancements to the freeze-drying process can significantly speed up drying and reduce energy consumption while maintaining phytochemicals, physical quality, and sensory attributes in final products. To overcome the downsides of conventional freeze-drying, hybrid freeze-drying methods were introduced with a great potential to provide food products at shorter drying durations, lower costs, and environmental friendliness while resulting in the same nutritive and sensory qualities as that of conventional freeze-drying in special circumstances. An overview of the most current improvements, adaptations, and applications of hybrid freeze-drying in food dehydration is given here. In this review, comparative studies are offered to characterize the drying process from the standpoint of chemical quality and sensory attributes. All the reviewed studies confirmed that the nutritional and sensory qualities of the end product can be retained using hybrid freeze-drying almost to the same extent as using single freeze-drying. It was also inferred that hybrid freeze-drying can surpass conventional freeze-drying and allow for obtaining dried products with characteristics typical of raw material if operating parameters are optimized based on product quality and energy usage.

Guaco ( Mikania glomerata Sprengel) syrup is one of the most popular herbal medicines used to treat the symptoms of asthmatic bronchitis, cough and hoarseness. The coumarin 2 H -1-benzopyran-2-one, is one of the major constituents of Guaco and contributes to its pharmacological effects. The pharmaceutical capsule form of dry extract of Guaco is recommended by the Brazilian Program of Medicinal Plants and Herbal Medicines and used in primary health care. In order to identify a new protocol to obtain the raw material for Guaco capsule production we evaluated two methods, including a freeze-drying process (lyophilization) and the spray-dryer technique, as well as the use of two adjuvants, Maltodextrins and Aerosil ® , in different concentrations. The coumarin levels of the dried extracts were analyzed by UV-spectrophotometry and HPLC-UV/DAD. The adjuvant Aerosil ® 8% showed better dry powder physical appearance. Lyophilization was observed to be the best process to obtain the dry extract of Guaco based on the measured coumarin levels.

Extracts with antimicrobial and antioxidant properties are limited in their application in food products due to their inability to withstand harsh environmental conditions, such as high temperatures and oxygen exposure. Therefore, the present study investigated the nanoencapsulation of Teucrium polium L. extract using the freeze‐drying method to facilitate its application and protection against environmental factors. In this regard, an emulsion containing Teucrium polium L. extract at concentrations of 10%, 20%, and 30% and a mixture of maltodextrin/Persian gum in three ratios of 1:2, 1:1, and 2:1 as the coating wall were produced and then dried in a freeze dryer. In the following, the properties of emulsions and produced nanocapsules were studied. According to the results, emulsions with high amounts of Persian gum showed more stability, zeta potential, and viscosity. However, their particle size and polydisparity index were lower than those of other emulsions. As the extract concentration increased, there was a decrease in stability, zeta potential, and viscosity, accompanied by an increase in particle size and polydispersity index. Concurrently, elevated concentrations of maltodextrin, Persian gum, and extract resulted in higher humidity, density, encapsulation efficiency, and antioxidant activity of the capsules. The most optimal properties of emulsions and nanocapsules were achieved at the 10% concentration of Teucrium polium L. extract and the 1:1 ratio of maltodextrin/Persian gum mixture as the wall material. It is noteworthy that the release rate of phenolic compounds reached its maximum value (88%) after 60 days. An emulsion containing Teucrium polium L. extract at concentrations of 10, 20, and 30%, and a mixture of maltodextrin/Persian gum (1:2, 1:1, and 2:1) as the coating wall were produced and dried in a freeze dryer. The optimal properties of emulsions and nanocapsules were achieved at the 10% concentration of extract and the 1:1 ratio of maltodextrin/Persian gum as the wall material. The release rate of phenolic compounds reached its maximum value (88%) after 60 days.