Effect Of Convective Drying Research Articles

Effect of Convective Drying and Far-Infrared Radiation on the Physical Properties and Microstructure of Yacón Chips (Smallanthus sonchifolius)

Convective drying is widely used in the food industry due to its simplicity and versatility, as it allows for better temperature control and heat distribution, which is essential for maintaining product quality. However, this method can be slower compared to infrared drying. The aim of this research was to evaluate the effect of convective and infrared drying on the physical properties and microstructure of yacón chips. An infrared dryer and a convection dryer were used to this effect, setting temperatures of 60, 70, and 80 °C for both methods. The color and texture properties, as well as the microstructure, changed with the increase in temperature. The greatest color variation in the yacón samples was reported by infrared drying at a temperature of 80 ° C. Regarding texture, there were no differences between the two methods. The microstructure of the yacón samples dried by hot air exhibited more significant cell damage, especially at 60 °C, in comparison with infrared drying, which showed a more microporous and compact structure. The results indicate that the method used impacted shrinkage: infrared drying produced a higher level of shrinkage when compared to convective drying. It is important to note that this is a significant physical change that can adversely affect the quality of dehydrated food. Infrared drying produced greater rehydration in comparison with convective drying. Similarly, improved rehydration was observed at a temperature of 70 ºC. In conclusion, the infrared drying method, coupled with appropriate drying conditions, constitutes a good alternative for drying yacón chips.

Kinetic simulation of convection drying for its effect on nutritional, functional, and phytochemical profiling of Colocasia antiquorum and Nasturtium officinale leaves of the Himalayan region

AbstractColocasia antiquorum (Taro) and Nasturtium officinale (Watercress) leaves are highly potent indigenous crops with rich nutritional and phytochemical profiles. The leaves were mathematically modeled, using thin‐layer models, to study the process kinetics for convection drying and its cumulative effect on the physico‐chemical, nutritional, functional, phytochemical, and targeted metabolite profiles. The best‐fit model for C. antiquorum was the two‐term model, whereas for N. officinale, Page model showed the best adequacy with the determination of least Chi‐square and high co‐efficient along with root mean square error. The color and pigment degradation were the prominent changes observed in the quality characteristics of C. antiquorum and N. officinale leaves depicted by the color degradation study. The nutritional composition was significantly affected by the convective drying with reduced ash, protein, and phenolic contents. The extraction yields were however higher along with some elevated metabolite contents estimated for convection drying in comparison to freeze‐dried leaves.Practical applicationsThis study explores the drying kinetic behavior for the progression of moisture loss occurring over the drying time and moderation of drying to achieve a desired moisture content at certain drying rates. The quality characterization before and after selected drying conditions revealed the sensitivity of the chlorophyll/carotenoid pigments, nutrients, and phenolics retained significantly after the end point of drying. Also, the effect of convective drying on the physicochemical, nutritional, and phytochemical contents was significant, which edifies the extent of alterations occurring due to convective drying on the quality characteristics of Colocasia antiquorum (Taro) and Nasturtium officinale (Watercress) leaves. Consequently, these two leafy vegetables hold good potential as crops to be promoted for nutritional security and health and wellness due to their rich bioactive profiles.

Drying of pears in CO2 modified atmosphere

One of the biggest problem encountered in drying area of food processing are the losses in food quality. While drying process is held, there is an important damage done to vitamins, polyphenols and other important nutriments. Being easily affected by high temperature and oxygen exposure, our concern was to find out what will be the effect of convective drying in air flow and CO2 modified atmosphere upon pears, “Conference” variety quality. Testing took place with temperatures between 60 and 100°C for both drying methods, one also used three different CO2 concentration regimes for the modified atmosphere approach, namely 30, 60, and 80%. The usage of carbon dioxide instead of air inside the drying chamber is expected to reduce oxygen exposure of the product during drying process, thus reducing oxidative reactions. Using CO2 as air substituent for convective drying showed good results from the organoleptic point of view by preserving a more natural pear color closer to the row material one, reduced damage done to ascorbic acid and total polyphenols concentration presumably thanks to reducing oxygen concentration and a slight drying duration reduction. There was deducted and established a mathematical model for the convective modified CO2 drying atmosphere as well as a pilot drying installation was designed for combined dying methods equipped with a CO2 recycling system.

Effect of convective drying on texture, rehydration, microstructure and drying behavior of yam (<em>Dioscorea pentaphylla</em>) slices

Drying is a critical primary processing technique in enhancing and maintaining the quality and storability of Dioscorea pentaphylla . The present work investigated the effect of forced convective drying at three drying temperatures (50, 60, and 70℃). Ten drying and four-color kinetics models were used to fit the drying data to study the drying behavior and the effect of temperature and time on color change. Moisture diffusivity increased with hot air temperature (4.88526 × 10 −10 – 8.8069×10 −10 m 2 /s). For Dioscorea pentaphylla slices, 27.04 (kJ/mol) of activation energy was found. Hii and others model gives the superior fitting for all the drying temperatures followed by logarithmic and Avhad and Marchetti model. Color kinetics was evaluated using L, a, and b values at a specified time during whole drying process. Temperature and time influenced the Lightness (L), yellowness (b), a value, chroma, hue, and browning index (BI). Dried slices from 70℃ showed more color change, whereas those from 50℃ had a medium-light brown. The modified color model is best fitted with high R 2 and lower chi-square. Potassium metabisulfite (K 2 S 2 O 5 ) pre-treatment and boiling significantly affected the drying time and final color of slices. The study reveals that drying at 50℃ exhibits better color retention and could be effectively used to dry Dioscorea pentaphylla . Dried Dioscorea pentaphylla can be utilized in both food and pharmaceutical industries for several applications for formulations food products and health supplements.

Convective drying performance of porous moist objects under turbulent flow conditions: effects of object shape and material

PurposeThe purpose of this paper is to examine the coupled heat and mass transport of different shaped porous moist objects in a rectangular channel under the effects of convective drying. Numerical simulations were performed under turbulent conditions for cylindrical, triangular and rectangular shaped different food products in a two-dimensional channel.Design/methodology/approachFinite element method was used for the unsteady problem and, effects of drying air velocity (AV) and temperature on transport mechanism were evaluated. Three different food materials were used for the circular shaped object and drying performance of the products under different conditions was compared.FindingsResults showed that, changing the air temperature has an important effect on drying for all shaped objects and all materials. The same effect was seen for the AV as, increasing the velocity had positive effects on drying. Two identical objects were placed in the channel one behind the other, and this configuration showed that location of the object in the channel is also important for drying. The moisture content in the object at the front is lower than in the object behind at the end of drying.Originality/valueThis paper can provide technical support to optimize drying performance in the industry with comprehensive data for the process.

Effects of convective drying and freeze-drying on the release of bioactive compounds from beetroot during in vitro gastric digestion.

Drying may alter the microstructure of vegetables and influence the release of bioactive compounds during digestion. The effects of convective drying (at 60 °C and 2 m s-1; CD) and freeze-drying (at -50 °C and 30 Pa; FD) on the microstructure (evaluated using scanning electron microscopy (SEM) and image analyses with ImageJ software) of beetroot and the kinetics of biocompound release (total polyphenol content (TPC) and antioxidant activity (AA)) during 180 min of in vitro gastric digestion have been studied. Raw beetroot was used as the control. Drying promoted the collapse of cell walls causing volume shrinkage that resulted in a greater cell number per area unit; meanwhile in vitro digestion caused cell structure disruption, which resulted in a lower cell number per area unit. Drying promoted decreases of TPC (42% in CD and 29% in FD) and AA (66% in CD and 63% in FD) of beetroot. However, release of TPC and AA from dried samples during digestion was 82% (CD) and 76 (FD) % higher than from the raw sample. The Weibull model allowed the satisfactory modelling of the TPC and AA release kinetics (mean relative error of simulation lower than 8.5%).

Effect of Convective Dryness Combined with Osmotic Dehydration, Blanching, Microwave and Ultrasonic Treatment on Bioactive Compounds and Rehydration Capacity of Dried Plums

Increasing interest in keeping bioactive compounds (anthocyanins, vitamin C) and dried fruit quality has motivated the researchers to investigate new combined drying technologies. The objective of this study was to evaluate the effects of convective drying combined with osmotic dehydration, bleaching, microwave treatment and ultrasonic treatment of bioactive compounds (anthocyanins, vitamin C), rehydration capacity and prune drying rate. Osmotic dehydration was achieved by maintaining plums for 1 hour in sucrose solution (300Brix). For microwave treatment, the plums were kept at 400 W for 80 s. For ultrasonic treatment, plums were immersed in distilled water and sonicated for 30 min at 40 kHz and 200 W. The blanching consists of immersing plums in hot water at 900C for 20 s and cooling them rapidly. Convective drying was carried out at 700C. Blanching led to the largest amount of evaporated water. The lowest reduction in anthocyanins, of 34.5%, was obtained for osmotic dehydrated plums. The prunes blanched before drying have had the highest rehydration capacity.

Convective Drying Kinetics and Quality Parameters of European Cranberrybush

In this research, the effects of convective drying (60, 70, 80 and 90 °C) techniques on the drying kinetics, color, antioxidant capacity and total phenolic content of European cranberrybush were investigated in detail. To choose the best thin-layer drying models for the drying treatments, 10 mathematical models were compared for the experimental data. Depending on the evaluation by statistical tests, the Midilli et al model was determined to be the best suitable model to explain the drying behavior of European cranberrybush samples. All of the colorimetric parameters were influenced by drying temperatures. Antioxidant capacity and total phenolic content values of European cranberrybush samples displayed a significant reduction at low-temperature levels (60 and 70 °C) with regard to those at high-temperature levels (80 and 90 °C). In addition, the correlation analysis between antioxidant capacity and total phenolic content exhibited a high degree of correlation (R2= 0.8656).

Functional relationships between phytochemicals and drying conditions during the processing of blackcurrant pomace into powders

The effect of convective drying, microwave-vacuum drying and their combination applied to blackcurrant by-product on the quality being measured in terms of the content of phytochemicals in the powders was examined. Convective drying, along with the increase in the temperature, linearly reduced the content of anthocyanins, flavonols and chlorogenic acids. Microwave vacuum drying significantly shortened the drying time, and resulted in higher retention of bioactive compounds at higher temperatures in comparison to convection. No functional relationship was observed between bioactive compounds and the power of magnetrons thus between the processing temperature and the content of individual groups of polyphenols, apart from delphinidin-3-O-rutinoside and delphinidin-3-O-glucoside. During the dehydration of blackcurrant pomace the exponential formation of hydroxymethylfurfural was noticed. The antioxidant capacity decreased along with the increase in drying temperature and in parallel with the decrease in anthocyanins content, thus suggesting that those polyphenols considerably influence the antioxidant potential of final products.

Effect of Convective Drying on Quality of Lemon Balm (Melissa Officinalis L.)

The effect of the conditions of drying air on the quality of lemon balm (Melissa officinalis L.) leaves such as colour, rosmarinic acid and essential oil content was investigated in this research. Fresh leaves with a moisture content of approximately 80% wet basis were dried to a final moisture content of 10% wet basis. The thin-layer drying experiments were conducted in a high precision through flow laboratory dryer at air temperatures of 30, 35, 40, 45, 50, 60 and 70°C and the corresponding relative humidity by maintaining 10g water per kg of dry air. The effect of the increased humidity of drying air was also investigated at 15, 20, 25 and 30g/kg specific humidity. For all drying trials the air velocity flowing through the sample was kept constant at 0.2 m/s. Although drying of leaves at 30°C preserved their medicinal qualities and colour, the duration of the process was comparably long. On the contrary, high drying air temperatures caused considerable colour degradation, a decrease in rosmarinic acid content and significant essential oil losses. The effect of relative humidity of drying air on the overall quality was found to be insignificant. A temperature limit of 40°C can be imposed for convective drying of lemon balm in order to protect the heat-sensitive active ingredients and maintain the green colour of the leaves.