Conventionally Dried Research Articles

Effect of osmodehydration on the quality attributes of plum (Prunus domestica)

Plum (Prunus domestica) is a seasonal nutraceutical fruit rich in many functional food nutrients such as vitamin C, antioxidants, total phenolic content, and minerals. Recently, researchers have focused on improvised technologies for the retention of bioactive compounds during the processing of perishable fruits; plum is one of these fruits. This study looked at how the percentage of moisture content and percentage of acidity were affected by conventional drying and osmotic dehydration. Total phenolic content (mg GA/100 g of plum), total anthocyanin content (mg/100 g), and vitamin C (mg/100 g) Conventional drying of fruit was carried out at 80.0 ℃ for 5 h. At various temperatures (45.0 ℃, 50.0 ℃, and 55.0 ℃) and hypertonic solution concentrations (65.0 B, 70.0 B, and 75.0 B), the whole fruit was osmotically dehydrated. It was observed that the osmotically treated fruit retains more nutrients than conventionally dried fruit. The total phenolic content of fruit significantly increased with the increase in process temperature. However, vitamin C and total anthocyanin content of the fruit decreased significantly with process temperature, and hypertonic solution concentration was observed. Hence, it was concluded that osmodehydration could be employed for nutrient retention in plum fruit over conventional drying. This process needs to be further refined, improvised, and optimised for plum processing.

Relevance of drying treatment on the extraction of high valuable compounds from invasive brown seaweed Rugulopteryx okamurae

The present paper is focused on the dehydration of the invasive brown seaweed Rugulopteryx okamurae comparing conventional and innovative techniques to maximize the alga potential. The optimized microwave hydrodiffusion and gravity (MHG) treatment allowed an adequate drying of the seaweed together with the recovery of antioxidant and gelling fractions. Chemical and structural profiles of the fresh and dried raw material, dehydration kinetics and the corresponding modelling, antioxidant characteristics of the gathered liquid phases or mechanical properties of the developed formulations were determined. Results indicated that MHG treatment (600 W for 5 min and 200 W for 15 min) involved a dramatic reduction in processing time (from 180 h for sunlight dehydration to 30 h for conventional oven drying and to 20 min for MHG treatment). All drying kinetics were successfully (R2 > 0.94) fitted with two-model parameters, being Page's model (R2 > 0.96) the one that provided the best fits. MHG suggested the recovery of liquid fractions with higher yields and antioxidant potential when compared with those obtained after ethanolic solid liquid extraction of conventionally dried seaweed. Slightly lower mineral content was identified in solid phases remained after MHG treatment. Alginates present in MHG liquid phases exhibited similar structural profiles to their commercial counterparts, featuring lower molecular weight distributions. It was possible to prepare alginate-based hydrogels with smoother viscoelastic properties than those commercially available, incorporated with microparticulate selected extracts after spray-drying treatment.

Cytotoxicity Assay of Dètente Instantanée Côntrolée Pre-Dried Pandanus conoideus Lam. Extracts

Red fruit (Pandanus conoideus Lam.) contains antioxidant compounds in high levels, including beta-carotene and tocopherol, which neutralize free radical compounds which can cause cancer. Red fruit contains 46% water so red fruit can only last 5 days in this condition. To maintain its stability, it is necessary to dry it with various methods, for example détente instantanée contrôlée (DIC) is a revolutionary pressure drop drying procedure. Every procedure for drying raw material can affect its quality and activity, for example the anticancer activity of red fruit. In-vitro cytotoxicity of DIC pre-dried red fruit extracts on HeLa cells has never been tested, so it is important to study. Red fruit which was obtained from Klamono, Sorong, a highland in Papua was extracted with ethanol or hexane which previously dried by DIC pre-drying or conventional drying methods were weighed then dissolved in DMSO. Cytotoxicity assays was conducted using method the MTT with five levels of extract concentration. Result of this research showed that cytotoxicity assay of red fruit extracts on HeLa cells showed that red fruit extract can inhibit cell viability. The conventionally dried red fruit extract shows stronger cytotoxicity against HeLa cells than the DIC pre-dried extract. Red fruit extract cytotoxicity against HeLa cells: ethanolic extract of red fruit previously dried by conventional drying technique > ethanolic extract of red fruit previously dried by DIC pre-drying process > hexane extract of red fruit previously dried by conventional drying method > hexane extract of red fruit previously dried by DIC pre-drying process.

Energy-saving new drying technology: Interval starting accessibility drying (ISAD) used to intensify dehydrofreezing efficiency

The aim of this study is to develop a new emerging technique to solve the main problem of conventional drying which is energy consumption. Interval Starting Accessibility Drying (ISAD) is based on subjecting food samples to an instantaneous action of hot air close to the starting accessibility time, during very short time followed by tempering periods (< 5 min). Quince samples have been submitted to ISAD with a temperature of 40 °C and different air flow velocities (2; 3.5; and 5 m/s), with 15 s of active time and tempering periods between 1 and 5 min. The impact of ISAD compared to conventional drying has been significant in terms of effective drying time and energy consumption. Hence, ISAD treatment significantly reduces the effective drying time by about 89% to reach the same final water content for conventionally dried quince samples. These results have promoting technological impact: a significant gain of energy is gotten by inserting short tempering periods. Consequently, ISAD can be considered as a relevant way for intensifying the internal resistance to water transfer during pre-drying process of fruits.

Omega–3 encapsulation by PGSS-drying and conventional drying methods. Particle characterization and oxidative stability

Particles from Gas-Saturated Solutions (PGSS)-drying has been used as a green alternative to encapsulate omega–3 polyunsaturated fatty acids (n–3 PUFAs) at mild, non-oxidative conditions. PGSS-dried particles have been compared to those obtained by conventional drying methods such as spray-drying and freeze-drying, finding encapsulation efficiencies (EE) up to 98% and spherical morphology for PGSS- and spray-dried particles. Freeze-dried powders showed irregular morphology and EE from 95.8 to 98.6%, depending on the freezing method. Differential scanning calorimetry (DSC) analysis revealed glass-transition and melting peaks of OSA-starch and a cold-crystallization peak corresponding to the encapsulated n–3 PUFA concentrate. Compared to conventionally dried powders, PGSS-dried microparticles showed lower primary and secondary oxidation after 28 days of storage at 4 °C. Ascorbic acid addition combined with the mild processing conditions of PGSS-drying yielded particles with a maximum peroxide value of 2.5 meq O2/kg oil after 28 days of storage at 4 °C.

Influence of Carbonic Maceration Pre-treatment on Functional Quality of Dried Tomato Quarters

As a novel pre-treatment, carbonic maceration (CM) was investigated in this study to figure out its effect on functional quality of conventionally dried tomato quarters (60 °C, 1.3 m/s air velocity). Carotenoids, tocopherols, total flavonoid, total phenolic and DPPH radical scavenging potential were determined for dried tomato samples (directly dried as a control and CM treated samples). Lycopene and β-carotene contents of CM treated tomato quarters were high compared to control samples (only conventionally dried). β-, γ-Tocopherol contents in dried tomato were raised with CM pre-treatment, as α-tocopherol decreased. Total flavonoid was found to be more than 2.5 times higher for CM treated samples compared to that in fresh tomato. CM displayed a promoter effect on total phenolic content and antioxidant activity of hydrophilic extracts, whereas there was no difference between those values determined for lipophilic extracts from control and pre-treated samples. CM has a potential as a pre-treatment before conventional drying of tomato to improve its nutritional contents and functional potential.

Finite element analysis of stress-related degrade during drying of Corymbia citriodora and Eucalyptus obliqua

With the use of experimental wood properties and input moisture content field data, a predictive 3D stress–strain finite element analysis (FEA) model was developed allowing to predict the development of stress-related end splitting and surface checking degrade during conventional and vacuum wood drying. Simulations were carried out for two Australian hardwood species, messmate (Eucalyptus obliqua) and spotted gum (Corymbia citriodora), as these species contrast, in terms of wood properties, drying rates and stress degrade susceptibility. The simulations were performed using a 1/8 symmetry model where the full board dimensions are 1900 mm long × 30 mm thick × 100 mm wide. Moisture content field data model simulations were utilised in a three-dimensional FEA model by extruding a 2D moisture content field computed in the T–L plane across the radial direction to create a 3D model. Material mechanical properties and shrinkage were calculated in relation to moisture content, over discrete time intervals, using a quasi-static solver. End split failure was investigated at the board end, and surface check failure at the board surface, using a Tsai–Wu failure criterion. Simulations showed that messmate was more susceptible to end splitting than spotted gum and that conventionally dried messmate was more susceptible to surface checking than vacuum-dried messmate. The same results were observed from drying trials. The locations of predicted surface check failure also matched drying trials and are compared.

Optimization of osmotic dehydration of pear followed by conventional drying and their sensory quality

The best condition for the osmotic dehydration of pears was evaluated by an experimental design as: sucrose osmotic solution at 45° Brix, 1:4 (g:g) of fruit:osmotic solution, 1.0 g/100 mL of CaCl2 and 3 h of immersion without agitation at room temperature. This condition resulted in about 20 g/100 g of solids gain and 30 g/100 g of water loss. When the osmotic dehydration (OD) was combined with a conventional drying (CD) (60 °C, until a final moisture of around 20 g/100 g), it resulted in dried pear slices with a 7.6 score for the overall sensory acceptance, a value 17% higher than the only conventionally dried pear. Furthermore, the time to reach 20 g/100 g final moisture using combined OD and CD was 41.8% lower than those dried only with CD.

Effect of Infrared and Conventional Drying Methods on Physicochemical Characteristics of Stored White Rice

The objective of this study was to investigate the effect of infrared (IR) drying followed by tempering and natural cooling on the change of physicochemical characteristics of white rice during up to 10 months of storage. The physicochemical characteristics of IR‐dried rice were also compared with those of conventionally dried rice. It took only 58 s to heat the rough rice from room temperature to 60°C with IR, and 2.17 percentage points of moisture was removed. After four months of storage, the increases in yellowness index, water uptake ratio, and volume expansion ratio of the rice dried with IR were 73.8, 63.9, and 55.3% those of rice dried with an ambient air drying method, respectively. IR drying slightly decreased the gelatinization temperature, enthalpy, and viscosities, reduced the changes in microstructure, and maintained cooking characteristics during storage. Therefore, the IR drying process is recommended to maintain the quality of white rice during storage.

Effect of drying technology on aspen wood properties

This article reports the impacts of three different drying treatments on selected physical and mechanical properties of European (Populus tremula L.) and hybrid (P. tremula x tremuloides) aspen wood. The material originates from 5 European aspen stands and 7 hybrid aspen stands in southern and central Finland. After processing the logs at a saw mill, sawn timber samples were dried using 1) conventional warm air drying, 2) press drying, or 3) heat treatment into Thermo-S grade by the Finnish Thermowood® method. Finally, small clearwood specimens were manufactured from different within-stem positions for the measurements of physical and mechanical properties. Both press dried and heat treated specimens absorbed water at significantly slower pace than the conventionally dried specimens. In normal climate, the conventionally dried, press dried and heat treated specimens conditioned at equilibrium moisture contents of 12.2, 8.7, and 8.9 per cent, respectively. It appears that the butt logs between 2–6 metres contain the lightest and, thus, weakest wood in aspen stems. Radial compression strength was at its highest in heat treated specimens, whereas conventionally and press dried specimens did not differ from each other. Press dried specimens had the highest longitudinal compression strength, also heat treated specimens showed higher values than the conventionally dried ones. Radial Brinell hardness of press dried specimens was higher than that of conventionally dried or heat treated specimens. Both modulus of elasticity and modulus of rupture were at their highest in press dried specimens. Irrespective of the drying treatment, the tangential shear strength of European aspen specimens was approximately 5% higher than that of hybrid aspen. Heat treated specimens indicated significantly lower tangential shear strength values than the conventionally dried ones. In case of both aspen species, the longitudinal tensile strengths of heat treated specimens were significantly lower than those of conventionally and press dried specimens. Heat treated specimens had the highest variability among the results. The inherent flaws in aspen wood material, e.g., wetwood and density

Nanocrystalline MgO powder materials prepared by sol-gel studied by X-ray diffraction and electron microscopy

Materials with MgO nanocrystallites were prepared by sol-gel synthesis. Alcogels were dried either supercritically at 538 K or in supercritical CO2. Conventional drying was also applied. Structure studies were performed by X-ray diffraction, scanning and transmis- sion electron microcopies. Nitrogen adsorption/desorption measurements were also per- formed. Calcination of dry gels at 723 K under vacuum yielded MgO nanocrystallites. In the studied materials the presence of the amorphous phase was observed. It is also stated that MgO nanocrystallites are immersed in an amorphous matrix. Morphology of supercritically dried samples is similar; rough surface of powder particles is observed. Powder particles of conventionally dried sample are more compact. Size of MgO crystallites is generally similar for all samples and equal to about 7 nm despite the drying conditions of alcogels. The specific surface area and the volume of mesopores are the great- est for the sample supercritically dried at 538 K.

A Comparison of the Effects of Microwave Versus Conventional Drying on the Mechanical Properties Distribution of Dried Green Porcelains

The effect of fast microwave drying of electroporcelain insulator component was studied by determining the reliability parameter. The Weibull modulus was calculated using the three‐point bend strength data of a large number of green samples which were dried using microwave energy. The results were compared with those obtained by conventional drying methods. It was observed that in most cases, microwave‐dried components yielded higher Weibull modulus than their conventionally dried counterparts. A high modulus value of &gt;15 was achieved on the microwave‐dried samples. The analysis of the result was useful in understanding the fast drying process in ceramics.

Impacto da secagem com microondas sobre o perfil sensorial de amêndoas de noz macadâmia

Avaliou-se o impacto da secagem com microondas sobre o perfil sensorial de noz macadâmia e comparou-se ao perfil sensorial de noz macadâmia seca convencionalmente, através da realização de análise descritiva quantitativa. O estudo ainda compreendeu a análise da alteração desses perfis após seis meses de armazenamento. Foram utilizadas sete amostras de noz macadâmia secas com microondas e uma seca convencionalmente. Os testes conduzidos após o processamento indicaram que a amêndoa seca convencionalmente apresentou maior gosto de ranço. Para os demais atributos, os tratamentos que utilizaram microondas não diferiram significativamente, em geral, do convencional. As amostras submetidas a microondas não apresentaram diferença estatística entre si, exceto para o atributo aroma de noz. Após seis meses foram observados resultados semelhantes aos encontrados no tempo inicial. Quanto à alteração do perfil sensorial das amostras observou-se perda de intensidade dos atributos sensoriais relativos à textura e intensificação dos atributos relativos à percepção do ranço. Foi possível concluir que, do ponto de vista sensorial, o uso de microondas é viável, pois conduziu a produto semelhante ao convencional. A utilização desta forma de energia conduziu a menores tempos de secagem proporcionando menor impacto, principalmente, na rancificação da noz quando comparado ao produto convencional.

Variation in Drying Behavior and Final Moisture Content of Wood during Conventional Low Temperature Drying and Vacuum Drying of Betula pendula Timber

Conventional and vacuum drying experiments were conducted on Betula pendula timber, which was sawn from trees felled during three different seasons. The influence of the wood procurement season on drying behavior differed, on the one hand, between the drying phases above and below 30% moisture content in the conventional drying, and, on the other hand, between the conventional and vacuum drying methods. During the first steps of the conventional drying process, relative humidity in the kiln, as well as drying time and drying rate, varied according to the felling season. Variations in environmental conditions outside the kiln and the seasonal variation in the physical properties of the wood were presumed to be the reasons for differences in drying behavior. The difference in moisture content gradient, i.e., the difference in final moisture content between the inner wood and the surface layer of boards, was greater in conventionally dried timber than in vacuum-dried timber. In conventionally dried timber there was a clear seasonal variation in the gradient of final moisture content, which was greatest for winter-felled wood. The premature drying of the surface layer during the first steps of the conventional drying process of winter-felled wood was the reason for the higher gradient of moisture content. Storage of wood as logs decreased the standard deviation of the final moisture content.

Effects of log storage and drying on birch (Betula pendula) wood proanthocyanidin concentration and discoloration

In conventional drying, sawn birch (Betula sp.) timber darkens and reddens from the inside while the layer a few millimetres under the yellowish surface remains light in color. Lack of information concerning the chemical basis of the discoloration hinders the development of a reliable solution for this problem. In this study, the role of soluble proanthocyanidins in discoloration of birch wood was investigated because the polymerization and oxidation of these compounds are known to yield insoluble reddish compounds. Different periods of log storage affected the synthesis of soluble proanthocyanidins during conventional drying. Concentration of proanthocyanidins also correlated with changes in the color of birch wood. Discoloration appeared differently in conventionally dried and vacuum-dried wood, which indicates that the discoloration mechanism in these drying methods may differ chemically, and/or the compounds that take part in discoloration may be different at different drying temperatures.

Birch (Betula pendula) Wood Discolouration during Drying. Effect of Environmental Factors and Wood Location in the Trunk

Summary Birch wood discolours during artificial drying, which is a considerable problem for the use of birch as raw material in the mechanical wood industry. In this investigation sample boards of Betula pendula were sawn to the dimensions used as raw material for parquet billets. The variables studied were those that may affect wood discolouration: growing site, felling date, length of the storage period for logs and location of the wood in the trunk. Discoloration of birch wood was studied in conventional and vacuum drying processes. The wood layer of about 2–5 mm under the yellow surface of conventionally dried boards remained light-coloured, while the inner wood of the boards became discoloured. During vacuum drying, however, the inner wood of sample boards clearly became discoloured. The radial location of the wood in the trunk affected the colour of dried wood more than the longitudinal location did. To keep the colour of dry wood as light as possible, it may be best to fell birch in winter and store the wood for several weeks before conventional drying. On the other hand, the lightest coloured wood obtained during vacuum drying was from autumnfelled five weeks stored birches, which may indicate differences in the process of discoloration in these two drying methods.

Hot air and freeze-drying of high-value foods: a review

Drying is an ancient process used to preserve foods. Conventional drying (hot air) offers dehydrated products that can have an extended life of a year. Unfortunately, the quality of a conventionally dried product is drastically reduced from that of the original foodstuff. Freeze-drying is based on the dehydration by sublimation of a frozen product. Due to the absence of liquid water and the low temperatures required for the process, most of deterioration and microbiological reactions are stopped which gives a final product of excellent quality. The comparison of both preservation processes, hot air and freeze-drying, was done taking into account several important characteristics such as shrinkage, glass transition temperature, process–quality interaction, drying kinetics, costs and new improvements. An updated bibliographic research served to compare both drying processes. Experimental data as well as theoretical results, from several years of research in the subject, were presented and compiled in order to support conclusions.

Primer cure and adhesion after light organic solvent preservative treatment of Radiata pine

This study examined the effect of preservative treatment and wood drying history on paint primer cure and adhesion for New Zealand radiata pine (Pinus radiata D. Don). Double Vacuum LOSP treatments resulted in a significantly lower LOSP uptake than did Lowry treatments, for both sapwood and heartwood. Wood drying history had no effect on uptake by sapwood, but did affect uptake by heartwood; high-temperature-kiln-dried heartwood retained more solvent than air-dried or conventionally dried heartwood. For sapwood, LOSP treatment method and wood drying history did not significantly affect either primer cure or primer adhesion. For heartwood, primer adhesion in the early stage of cure was better with Double Vacuum treatments. Double Vacuum treatments also resulted in a higher cure of primer, two days after priming, than did Lowry treatment when either conventionally or high-temperature-kiln-dried heartwood was used, but no significant difference was found with air-dried heartwood. It was concluded that, for radiata pine heartwood, Double Vacuum treatment, combined with either air-drying or conventional drying, will reduce LOSP uptake and give better primer performance, so long as effective ventilated solvent removal is achieved before priming.

Titania-Silica Mixed Oxides: I. Influence of Sol-Gel and Drying Conditions on Structural Properties

Mesoporous titania-silica aerogels with highly dispersed titanium have been prepared by an alkoxide-sol-gel process with ensuing semicontinuous extraction using supercritical CO 2. An acidic hydrolysant was added to a solution of tetraisopropoxytitanium(IV) modified by acetylacetonate and tetramethoxysilicon(IV) in isopropanol. The resulting titania-silica gels were dried by different methods, including conventional drying, high-temperature supercritical drying, and extraction with supercritical CO 2 (low-temperature aerogel). The influence of preparation parameters (the hydrolysis route, Ti-content, drying method, and calcination temperature) on the structural and chemical properties of the aero- and xerogels was studied by means of N 2-physisorption, X-ray diffraction, thermal analysis, and vibrational spectroscopy (FTIR, FTRaman). Prehydrolysis of the silicon alkoxide generally led to lower porosity, but did not influence the Si-O-Ti connectivity up to a calcination temperature of 1073 K. The conventionally dried xerogels contained titanium well-dispersed in the silica matrix and were predominantly microporous. High-temperature supercritical drying afforded meso- to macroporous aerogels with negligible microporosity, but undesired segregation of anatase. With the low-temperature aerogels, an increase of the nominal TiO 2 content from 2 to 20 wt% resulted in lower microporosity, higher BET surface area (up to ca. 700 m 2/g), and a rise in the contribution of Si-O-Ti species. Concomitantly the Ti-O-Ti connectivity increased without any indication of long-range ordering from X-ray analysis. The low-temperature aerogel with 20 wt% TiO 2 combined mesoporosity with high Ti dispersion and structural stability up to 873 K in air, properties desirable for epoxidation of olefins.