Drying characteristics of foamed alphonso mango pulp in a continuous type foam mat dryer

Influence of microwave drying on quality parameters of foamed Nagpur Mandarin (Citrus reticulata) juice

In the world of industrial drying processes, foam mat microwave drying is a significant and valuable approach. Its advantages include increased drying effectiveness, preservation of product quality, energy and cost savings, flexibility in application, and improved safety. Development of Nagpur mandarin juice powder is tedious and time-consuming due to its bitter test and less total soluble solid, therefore the present research carried out with the process parameters for microwave drying include microwave power levels (180, 360, 540, 720, and 900 W) and drying bed thicknesses (2, 4, and 6 mm). Foamed juice is produced using soy protein isolate (2.10 %), GMS (2.75 %), CMC (1.75 %), and sugar (5.10 %), with whipping times of 8 min. Additional foaming agents include guar gum (0.45 %), soy protein isolate (3.30 %), and sugar (10 %) with whipping times of 6 min. The optimal conditions for drying Nagpur mandarin juice were determined through analysis using Design-Expert 11.0.4.1 software. These conditions include 540 W of microwave power, a drying bed thickness of 3 mm, and the use of a foaming agent comprising 2.10 % soy protein isolate, 2.75 % GMS, 1.75 % CMC, and 5.10 % sugar, with an 8-min whipping period. Under these optimized conditions, the resulting powder exhibited the following characteristics: color b value of 19.59, ΔE (change in color) of 6.24, acidity of 0.40 %, ascorbic acid content of 36.64 mg/100 g, water activity of 0.26, drying time (in minutes), and overall acceptability rating of 7.77. These findings highlight the effectiveness of the optimized process parameters in achieving desirable quality attributes for Nagpur mandarin juice powder production.

Preserving nutrient content in red cabbage juice powder via foam-mat hybrid microwave drying: Application in fortified functional pancakes

Red cabbage, a highly nutritious cool-season cruciferous vegetable, is rich in anthocyanins; however, the instability of anthocyanins during processing and storage poses challenges. This study aimed to optimize the foam-mat drying process of red cabbage juice (RCJ) with a high anthocyanin content using a hybrid microwave hot air-drying system (MW-HAD) as a dehydration method compared to conventional techniques (HAD) using response surface methodology (RSM). Additionally, the produced red cabbage juice powder (RCJP) was used to enrich the pancake formulation. The developed model exhibited a high degree of reliability with optimal conditions and was determined for microwave power, temperature, foaming agent carboxymethylcellulose (CMC), and egg white protein (EWP) as 360 W, 60°C, 0.3%, and 1.2%, respectively. Moisture content (%) was decreased from 93.47 to 8.62 at optimum process conditions. In comparison to the control (60°C), foam mat drying with the MW-HAD hybrid system reduced the drying time (DT) by more than 90.9% due to the higher drying rate, while many physicochemical properties, especially total anthocyanin content (TAC), were better preserved. Utilization of RCJP in the production of anthocyanin-rich functional pancakes resulted in enhanced nutritional qualities compared to control pancakes with increased protein (35.07%), total phenolic (75.8%), dietary fiber (82.9%), and anthocyanin content (100%). In conclusion, MW-HAD demonstrates significant potential as a promising drying method to reduce the DT and preserve the physicochemical properties of RCJP. Furthermore, the application of the optimized RCJP in anthocyanin-rich functional pancakes highlights improved nutritional qualities, making a substantial contribution to the advancement of functional foods.

Optimization of foaming process for development of modified aloe polysaccharide (MAP) juice and powder using foam-mat drying

The present study was performed to optimize the modified aloe polysaccharide (MAP) foaming process and to determine the effect of drying process parameters on the quality of obtained MAP powder. The studied process parameters were glycerol monostearate (GMS), carboxymethyl cellulose (CMC), and whipping time (WT) which was varied between 1 and 4% w/v, 0.1-0.5% w/v, and 1-5 min, respectively. The optimized values of foaming process parameters were 3.87% GMS, 0.39% CMC, and 4.89 min WT with a desirability of 0.889. The optimized foamed MAP juice was dried at different foam thicknesses (FT) (1, 3, and 5 mm) and drying temperatures (DT) (50, 60, and 70 °C) to develop MAP powder and compared with non-foamed aloe powder developed under the same drying condition. Based on functional properties, the best GMS foamed MAP powder was achieved at 50 °C DT and 1 mm FT, recording powder yield (16%), solubility (20.85%), and polysaccharide content (282 mg/L).

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01354-6.

Study of functional, biochemical, and sensory qualities of jackfruit pulp powder produced through optimized foam-mat drying parameters

Jackfruit (Artocarpus heterophyllus) production is abundant during the summer season in Southeast Asia and is also produced throughout the year in some parts of South India. Attributed to the absence of viable process technology, the pulp is predominantly consumed fresh and has not been used effectively for other applications such as in ice cream, beverages, custard preparations, or as a flavor enhancer. The conversion of the high sugar-containing pulp to powder is difficult. Hence, the foam-mat drying of jackfruit pulp was carried out using different foaming agents and stabilizers. The effect of maltodextrin (MD; 3%, 4%, and 5% w/w), glycerol-monostearate (GMS; 2%, 3%, and 4% w/w), or soy protein (SP; 0.5%, 1%, and 1.5% w/w), and 0.5% methylcellulose added to the pulp at a concentration of 8 °Brix on foam expansion (FE; %), foam retention (FR; %), total carotenoids (TC; mg/100 g pulp), and overall acceptability (OA) were investigated, and their levels were optimized using central composite design of response surface methodology. The foam mats were dried at a drying air temperature of 70°C along with a foam thickness of 4 mm. The samples were evaluated based on drying time, foaming, functional, biochemical, and sensory qualities. The optimum levels of MD and GMS were 3.96% (4.0%) and 3.01% (3.0%), respectively, which led to the foam-mat-dried jackfruit powder with properties within the desirable range. At these optimum conditions, the predicted FE, FR, TC, and OA were 69.84%, 89.42%, 0.152 mg/100 g pulp, and 7.73, respectively. The optimum levels of MD and SP were 3.95% (4.0%) and 1.02% (1.0%), respectively, and the corresponding properties (considered as responses) of this foam-mat-dried jackfruit powder such as FE, FR, TC, and OA were 74.45%, 84.80%, 0.14 mg/100 g pulp, and 7.6, respectively. PRACTICAL APPLICATION: This study is one of the few studies that is focused on the development of a technique for the long-term preservation of jackfruit powder for further applications that will also reduce the wastage of jackfruit attributed to its fast perishability. This technology can be replicated in other parts of the world. This article has demonstrated foam-mat drying as a useful technique to achieve high-quality jackfruit pulp powders with desirable drying, foaming, functional, biochemical, and sensory qualities using different foaming agents and stabilizers.

Mathematical Models to Describe the Foam Mat Drying Process of Cumbeba Pulp (Tacinga inamoena) and Product Quality

The present study investigated the mathematical modeling foam-mat drying kinetics of cumbeba pulp and the effect of drying conditions on the color and contents of ascorbic acid, flavonoids, and phenolic compounds of the powder pulps obtained. Foam-mat drying was carried out in a forced air circulation oven at temperatures of 50, 60, and 70 °C, testing foam-mat thicknesses of 0.5, 1.0, and 1.5 cm. The increase in the water removal rate is a result of the increase in air temperature and the decrease in the thickness of the foam layer. Among the empirical and semi-empirical mathematical models, the Midilli model was the one that best represented the drying curves in all conditions evaluated. Effective water diffusivity ranged from 1.037 × 10⁻⁹ to 6.103 × 10⁻⁹ m² s⁻¹, with activation energy of 25.212, 33.397, and 36.609 kJ mol⁻¹ for foam thicknesses of 0.5, 1.0, and 1.5 cm, respectively. Cumbeba powders showed light orangish colors and, as the drying temperature increased from 50 to 70 °C, for all thicknesses, the lightness value (L*) decreased and the values of redness (+a*) and yellowness (+b*) increased. Foam-mat drying at higher temperatures (60 and 70 °C) improved the retention of ascorbic acid and flavonoids, but reduced the content of phenolic compounds, while the increase in thickness, especially for flavonoids and phenolic compounds, caused reduction in their contents. The foam-mat drying method allowed obtaining a good-quality cumbeba pulp powder.

Foam mat drying: Recent advances on foam dynamics, mechanistic modeling and hybrid drying approach

Drying is one of the oldest and most widely used methods for food preservation. It reduces the availability of moisture and inhibits microbial and enzymatic spoilage in food products. Foam mat drying is a mild drying technique used for semiliquid and liquid foodstuff. It is useful for heat-sensitive and sticky liquid food products. In this process, liquid food is converted into foam using surfactant additives, which can be a foaming agent or foam stabilizer. These additives are surface-active compounds of vegetative and animal origins. The foamed material is then convectively dried using hot air. The foam mat drying is an efficient and economical technique. With the emergence of different hybrid techniques such as foam mat freeze drying, foamed spray drying, foamed vacuum drying, and microwave assisted foam mat drying, the powders' physical, chemical, and functional properties have enhanced many folds. These strategies have shown very promising results in terms of cost and time efficiency in almost all the cases barring a few exceptions. This review article attempts to comprehensively summarize the mechanisms dictating the foam mat drying process, novel technological tools for modeling, mathematical and computational modeling, effects of various foaming additives, and various hybrid techniques employed to foam mat drying.

Mathematical modeling and multivariate analysis applied earliest soybean harvest associated drying and storage conditions and influences on physicochemical grain quality

Anticipating the harvest period of soybean crops can impact on the post-harvest processes. This study aimed to evaluate early soybean harvest associated drying and storage conditions on the physicochemical soybean quality using of mathematical modeling and multivariate analysis. The soybeans were harvested with a moisture content of 18 and 23% (d.b.) and subjected to drying in a continuous dryer at 80, 100, and 120 °C. The drying kinetics and volumetric shrinkage modeling were evaluated. Posteriorly, the soybean was stored at different packages and temperatures for 8 months to evaluate the physicochemical properties. After standardizing the variables, the data were submitted to cluster analysis. For this, we use Euclidean distance and Ward's hierarchical method. Then defining the groups, we constructed a graph containing the dispersion of the values of the variables and their respective Pearson correlations for each group. The mathematical models proved suitable to describe the drying kinetics. Besides, the effective diffusivity obtained was 4.9 × 10-10 m2 s-1 promoting a volumetric shrinkage of the grains and influencing the reduction of physicochemical quality. It was observed that soybean harvested at 23% moisture, dried at 80 °C, and stored at a temperature below 23 °C maintained its oil content (25.89%), crude protein (35.69%), and lipid acidity (5.54 mL). In addition, it is to note that these correlations' magnitude was substantially more remarkable for the treatments allocated to the G2 group. Furthermore, the electrical conductivity was negatively correlated with all the physicochemical variables evaluated. Besides this, the correlation between crude protein and oil yield was positive and of high magnitude, regardless of the group formed. In conclusion, the early harvest of soybeans reduced losses in the field and increased the grain flow on the storage units. The low-temperature drying and the use of packaging technology close to environmental temperatures conserved the grain quality.

Stability of Foams in Vacuum Drying Processes. Effects of Interactions between Sugars, Proteins, and Surfactants on Foam Stability and Dried Foam Properties

The hypothesis was that saccharides mediate interactions between surface-active components and that this will have an impact on foam decay during the drying process. Static light scattering was performed to determine changes in interactions between the foam stabilizer on a molecular level. Furthermore, pendant drop and oscillating drop measurements were performed to examine the surface tension and surface rheology. Foams were dried in conventional dryers as well as microwave-supported vacuum dryers. Final foam properties were determined. It was shown that the addition of sugars, often added as protective substances for sensitive organic molecules, resulted in lower repulsion between different types of surface-active components, namely polysorbate 80 and β-lactoglobulin (β-lg). Differences in impact of the types of sugars and between different types of surfactant, protein, and small molecules were observed influencing the foam decay behavior. The interfacial properties of polysorbate 80 and β-lg were influenced by the type of the used sugars. The surface elasticity of protein stabilized surfaces was higher compared to that of polysorbate stabilized systems. Protein stabilized systems remained more stable compared to polysorbate systems, which was also affected by the used saccharide. Overall, a correlation between molecular interactions and foam decay behavior was found.

Foam Structure Preservation during Microwave-Assisted Vacuum Drying: Significance of Interfacial and Dielectric Properties of the Bulk Phase of Foams from Polysorbate 80-Maltodextrin Dispersions

This study aimed at examining the cause of differences in the structure preservation of polysorbate 80–maltodextrin foams during microwave-assisted vacuum drying (MWVD) versus conventional vacuum drying (CVD). Aqueous dispersions of 3% polysorbate 80 and 0–40% maltodextrin were characterized for their dielectric and interfacial properties, and results were related to their drying performance in a foamed state. Surface tension and surface dilatational properties as well as dielectric properties clearly responded to the variation in the maltodextrin content. Likewise, the foam structure preservation during CVD was linked to the maltodextrin concentration. Regarding MWVD, however, foams collapsed at all conditions tested. Nevertheless, if the structure during MWVD remained stable, the drying time was significantly reduced. Eventually, this finding could be linked to the dielectric properties of polysorbate 80 rather than its adsorption kinetics and surface film viscoelasticity as its resonant frequency fell within the working frequency of the microwave drying plant.

Physicochemical design rules for the formulation of novel salt particles with optimised saltiness

Novel sodium reduction strategies are urgently required by the food industry. We hypothesised that redesigning salt crystals (size, density, hydrophobicity and flow properties) will offer a new route to increase saltiness and therefore reduce sodium. Eight salts were compared with different physicochemical properties, the resultant particles were characterised and adhesion to product, loss in-pack, rate of dissolution and ultimately saltiness perception were evaluated. Principle findings included that particle adhesion was driven by particle size (r = -0.85, p = 0.008), bulk density (r = -0.80, p = 0.017) and flow properties (r = 0.77, p = 0.015); loss in-pack was associated with particle size and hydrophobicity of the salt particle while dissolution and/or saltiness perception was also driven by particle size and hydrophobicity of the salt particle. The findings offer a new set of design rules for future ingredient design for the food and flavour industries.

Prototype continuous microwave foam-mat dryer: design and fabrication

A prototype microwave foam mat dryer with continuous operation was fabricated for tomato and guava. Results of preliminary studies on microwave foam mat drying of tomato and guava were used to design the prototype. The continuous foaming operation was achieved with the help of a submersible pump controlled by a time switch which ensured the delivery of pulp into foaming container and streamlined the delivery of foam on the drying surface (belt). The drying section presented a combination of hot air and microwaves, which resulted in accelerated heating and subsequently drying of the foam. Dried flakes were collected at the exit with the scrapper blade, which ensured appreciable recovery. The quality evaluation of guava pulp and tomato pulp dried at different microwave powers and inlet air temperatures revealed that the products dried at 1000 W microwave power and 50 °C exhibited excellent physicochemical properties in both the cases. Performance evaluation study depicted that the capacity of the dryer for guava drying was 4.84 l/h, the final moisture retention in the dried powder was 0.059 g H₂O/g d.m, recovery was 98.34% and energy consumption was 1.32 kWh/l. Similarly, for tomato drying the capacity, final moisture content, recovery and energy consumption were 4.03 l/h, 0.062 g H₂O/g d.m, 91.29% and 1.49 kWh/l respectively.

Water Vapor Pathways during Freeze-Drying of Foamed Product Matrices Stabilized by Maltodextrin at Different Concentrations

This study aimed to identify the water-vapor transport mechanisms through an aerated matrix during microwave freeze-drying. Due to the larger surface area and lower water vapor transport resistance of an aerated product compared to the solution, foam structures dry faster. Different foam structures were produced with different maltodextrin (MD) concentrations (10–40%) as a foam-stabilizing agent. Depending on the initial viscosity of the solution prior to foaming, the samples differed in overrun (41–1671%) and pore size (d50 = 58–553 µm). Experiments were partially performed in a freeze-drying chamber of a light microscope to visualize structural changes in-situ. Different mechanisms were identified explaining the accelerated drying of foams, depending on the MD concentration, above or below 30%. At lower MD concentration, high overruns could be produced prior to freezing with big bubbles and thin lamellae with short diffusion pathway length. At 40% MD concentration, the viscosity was too high to integrate much air into the product. Therefore, the foam overrun was low and the bubble size small. Under these conditions, the water vapor generates high pressure, resulting in the formation of channels between bubbles, thus creating the pathways with low resistance for a very fast water vapor mass transfer. In addition, microwave freeze-drying experiments using a pilot plant unit were conducted to validate the findings of the freeze-drying microscope. A reduction of the drying time from 150 min (10% MD) to 78 min (40% MD) was achieved.

Analysis of the Anthocyanin Degradation in Blue Honeysuckle Berry under Microwave Assisted Foam-Mat Drying

Changes in nutrient content and bioactivity are important indicators to evaluate the quality of products. Berries are rich in antioxidant anthocyanins, which are prone to degradation during drying. The effects of different variables on the stability of anthocyanins in berry puree during microwave assisted foam-mat drying (MFD) was investigated by path analysis and degradation kinetics analysis. The experimental results showed that the degradation of anthocyanins mainly occurred in the last drying stage. The temperature and the moisture content have both direct and indirect effects on the anthocyanin stability. The direct path coefficient of the moisture content on anthocyanins was 0.985, and the direct path coefficient of temperature on anthocyanins was −0.933. The moisture content to temperature ratio (M/T) was first put forward to estimate the anthocyanin degradation. The results of the regression analysis confirmed that the anthocyanins were stable at M/T of 0.96–3.60. A finite element simulation model was established to predict the anthocyanin degradation rate and content. These research results could provide a theoretical reference for use in optimizing the MFD processing technologies.

Foaming properties of custard apple pulp and mathematical modelling of foam mat drying

Foaming of custard apple pulp was carried out using foaming agent and stabilizer for drying of pulp in thin layers. The effect of parameters was studied and optimization was performed using response surface methodology. The concentration of egg albumen (0-20%, w/w) as foaming agent with methyl cellulose (0.0-0.50%, w/w) as stabilizer were added for whipping time (5-25 min). The foam properties were influenced by concentration of foaming agent and whipping time. The desirable foaming properties (high foam expansion, lower foam density and high foam stability) was observed at 15% of egg albumen, 0.37% of methyl cellulose for a whipping time of 17.32 min. Dehydration of optimized foamed pulp was completed within 100-140 min for 60-75 °C temperatures at 2 mm thickness of pulp. Average effective diffusivities remained 2.01-9.67 × 10^-08 m²/s and activation energy was 29.99 kJ/mol.

The Concept of Microwave Foam Drying Under Vacuum: A Gentle Preservation Method for Sensitive Biological Material

Microwave vacuum drying as compared to conventional vacuum drying has evinced advantages regarding drying time, while comparable product characteristics were achieved when drying sensitive biological material. Due to the volumetric microwave input, a time reduction of up to 90% is possible. When drying viscous liquids, a foamed structure that remains stable during drying exhibits further advantages as the diffusion-limited third drying step is enhanced by the porous structure. As foams not only have to be thermally resistant during microwave vacuum processing, but also withstand the vacuum, a specific process for foam drying by microwaves under low pressure conditions was developed. Foam formation and stabilization was achieved by using a synergistic mixture of proteins and carbohydrates; Lactobacillus paracasei ssp. paracasei F19 (L. paracasei) served as a model sensitive substance. Investigation of surface activity and foaming properties as a function of L. paracasei concentration revealed a significant positive contribution of the bacterial cells. It was shown that L. paracasei directly adsorbed at the air-water interface. Besides, a structuring of the liquid lamellae was assumed. Moreover, drying time was reduced to at least 50% compared to microwave vacuum drying without foaming. It was further observed that the slight loss in survival was mainly due to the relatively high moisture content and high vacuum levels at the beginning of the process. However, foaming, vacuum application, and final drying, respectively, did not affect viability of the bacterial cells. Thus, by incorporation of lactic acid bacteria into foam structures, drying can be carried out in a fraction of time, and further results in high-product quality. PRACTICAL APPLICATION: The application of continuous foam drying offers an efficient and energy-saving alternative to the currently applied techniques for the processing of sensitive material. The process could be applied for the preservation of starter cultures and probiotics as well as in the pharmaceutical industry, when sensitive material such as therapeutic proteins is dried. This process is especially suitable for freezing-sensitive and thermolabile substances.

Eating Habits and Sustainable Food Production in the Development of Innovative “Healthy” Snacks

In recent years, science about nutrition and food technology has grown enormously. These advances have provided information about the human body’s need for certain nutrients and the impact of human nutrition on quality of life and health. New technologies enable the production of many new products that meet the expectations of food consumers. To meet the challenges posed by consumers, food producers are developing new food products that are included in the next generation food. Changing nutritional trends force the food industry and technologists to look for innovative products that are not only ready for immediate consumption, but are also unique in terms of nutritional value and contain a minimum number of additives. Existing research trends are intended to develop innovative products, which can be considered a healthy snack that can help in the fight against obesity, especially among children. Such products are freeze-dried fruit or vegetable gels, fruit skins or edible films. The aim of the work is to present a review of the problem of increasing childhood obesity, the place of snacks in the daily diet and the possibility of replacing unhealthy, high-calorie snacks with alternative products with beneficial properties, in which balanced production is used. For example, the use of freeze-drying and the addition of only natural hydrocolloids provides an “clean label” healthy snack that is appreciated by conscious consumers.

Drying Rate and Product Quality Evaluation of Roselle (Hibiscus sabdariffa L.) Calyces Extract Dried with Foaming Agent under Different Temperatures

The utilisation of roselle (Hibiscus sabdariffa L.) calyx as a source of anthocyanins has been explored through intensive investigations. Due to its perishable property, the transformation of roselle calyces into dried extract without reducing their quality is highly challenging. The aim of this work was to study the effect of air temperatures and relative humidity on the kinetics and product quality during drying of roselle extract foamed with ovalbumin and glycerol monostearate (GMS). The results showed that foam mat drying increased the drying rate significantly and retained the antioxidant activity and colour of roselle calyces extract. Shorter drying time was achieved when higher air temperature and/or lower relative humidity was used. Foam mat drying produced dried brilliant red roselle calyces extract with better antioxidant activity and colour qualities when compared with nonfoam mat drying. The results showed the potential for retaining the roselle calyces extract quality under suggested drying conditions.

Foam-Mat Drying of Muskmelon

The Box–Behnken design of experiments under response surface methodology (RSM) was used to optimize the foaming process for the development of foam mat-dried muskmelon powder. The independent variables were the concentration of egg albumen (EA), carboxymethyl cellulose (CMC) and whipping time (WT). The responses were foam density, foam drainage volume and foam expansion. The optimum conditions for foaming process were EA (11.59% w/w), CMC (0.59% w/w) and WT (3.97 min). The unfoamed muskmelon pulp took longer time to dry to the final moisture content of 2% d.b than foamed pulp. The effective diffusivity for the foamed muskmelon pulp was found to be higher than the unfoamed pulp. The unfoamed pulp resulted in a sticky and dark colored powder, whereas the foamed pulp had a free-flowing and light colored powder. The flaky and porous foam-dried product can be used as an ingredient in broad range of food products.

A novel approach for improving the drying behavior of sludge by the appropriate foaming pretreatment

Foaming pretreatment has long been recognized to promote drying materials with sticky and viscous behaviors. A novel approach, CaO addition followed by appropriate mechanical whipping, was employed for the foaming of dewatered sludge at a moisture content of 80-85%. In the convective drying, the foamed sludge at 0.70 g/mL had the best drying performance at any given temperature, which saved 35-41% drying time for reaching 20% moisture content compared with the non-foamed sludge. Considering the maximum foaming efficiency, the optimal CaO addition was found at 2.0 wt%. For a better understanding of the foaming mechanisms, the foamability of sludge processed with other pretreatment methods, including NaOH addition (0-3.0 wt%) and heating application (60-120 °C), were investigated while continuously whipping. Their recovered supernatant phases were characterized by pH, surface tension, soluble chemical oxygen demand (sCOD), protein concentration, polysaccharide concentration and spectra of excitation-emission matrices (EEM). These comparative studies indicated that the sludge foaming was mainly derived from the decreased surface tension by the surfactants and the promoted foam persistence by the protein derived compounds. Further, a comprehensive analysis of the sludge drying characteristics was performed including the surface moisture evaporation, the effective moisture diffusivity and the micromorphology of dried sludge. The results indicated that the drying advantages of foamed sludge were mainly attributed to the larger evaporation surface in a limited drying area and the more active moisture capillary movement through the liquid films, which resulted in longer constant evaporation rate periods and better effective moisture diffusivity, respectively.

Process Optimization for Foam Mat-Tray Drying of Passiflora edulis Flavicarpa Pulp and Characterization of the Dried Powder

Passion fruit (Passiflora edulis flavicarpa) is a seasonal, tropical, pulpy fruit, known for a rich source of Vitamin C, antioxidants, and delicate flavor. Presently, freezing technique has been used to preserve the pulp. This article reports alternate method of preservation by foam mat convective air drying of fruit pulp under moderate temperatures. The optimization of process parameters, particularly air temperature, was done with subsequent mathematical modeling of the process and assessment of quality parameters by retention of physicochemical properties and antioxidant capacity of the fruit powder. Sixty degree Celsius was found to be the optimum temperature, and Henderson and Pabis model showed best fit to the drying characteristics data (R2 = 0.99). Diffusivity characteristics of moisture during drying were also studied. As drying temperature was increased, total color difference and rehydration ratio decreased, whereas non-enzymatic browning index, total phenolic content, and total antioxidant activity showed increase that was attributed to inhibition of oxidative enzymes and biochemical changes. Dried passion fruit powder showed overall acceptability in terms of organoleptic properties and total antioxidant activity.

Application of foam-mat drying with egg white for carrageenan: drying rate and product quality aspects

Drying is a significant step in the production of carrageenan. However, current drying process still deals with too long drying time and carrageenan quality degradation. The foam mat drying is an option to speed up drying process as well as retaining carrageenan quality. In this case, the carrageenan was mixed with egg white (albumin) as foaming agent and methyl cellulose for foam stabilizer. The foam will break the carrageenan gels and creates the porous structure resulting higher surface area for water transfer. This research studied the effect of egg white and methyl cellulose on carrageenan drying at various air temperature, and thickness. As a response, the water content versus time was observed and the drying rate was estimated. Meanwhile, the carrageenan texture was verified by X-RD (X-Ray Diffraction) and TEM (Transmission Electron Microscopy). Results showed that the presence of egg white stablized by methyl cellulose can speed up drying rate as well as retaining the crystalline structure of carrageenan. The higher albumin content, the faster drying rate. However, the addition of albumin and methyl cellulose restricted not more than 30 % in the mixture for keeping carrageenan quality and purity. By adding egg white 20 % and methyl cellulose 10 %, the water diffusion and drying rate can be two fold compared with carrageenan drying without foam. The improvement can be higher at the higher temperature and thinner carrageenan sheets.

Optimization of process parameters for foam-mat drying of papaya pulp

Experiments were carried out to optimize the process parameters for production of papaya powder using foam-mat drying. Papaya pulp was foamed by incorporating methyl cellulose (0.25, 0.5, 0.75 and 1 %, w/w), glycerol-mono-stearate (1, 2, 3 and 4 %, w/w) and egg white (5, 10, 15 and 20 %, w/w) as foaming agents. The maximum stable foam formation was 72, 90 and 125% at 0.75 % methyl cellulose, 3 % glycerol-mono-stearate and 15 % egg white respectively with 9°Brix pulp and whipping time of 20 min. The foamed pulp was dried at air temperature of 60, 65 and 70 °C with foam thickness of 2, 4, 6, 8 and 10 mm in a batch type cabinet dryer. The drying time required for foamed papaya pulp was lower than non-foamed pulp at all selected temperatures. Biochemical analysis results showed a significant reduction in ascorbic acid, β-carotene and total sugars in the foamed papaya dried product at higher foam thickness (6, 8 and 10 mm) and temperature (65 and 70 °C due to destruction at higher drying temperature and increasing time. There was no significant change in other biochemical constituents such as pH and acidity. The organoleptic and sensory evaluation of the quality attributes of papaya powder obtained from the pulp of 9°Brix added with 3 % glycerol-mono-stearate, whipped for 20 min and dried with a foam thickness of 4 mm at a temperature of 60 °C was found to be optimum to produce the foam-mat dried papaya powder.

Mathematical modelling of thin layer hot air drying of carrot pomace

Thin layer carrot pomace drying characteristics were evaluated in a laboratory scale hot air forced convective dryer. The drying experiments were carried out at 60, 65, 70 & 75 °C and at an air velocity of 0.7 m/s. Mathematical models were tested to fit drying data of carrot pomace. The whole drying process of carrot pomace took place in a falling rate period except a very short accelerating period at the beginning. The average values of effective diffusivity ranged from 2.74 × 10(-9) to 4.64 × 10(-9) m(2)/s for drying carrot pomace. The activation energy value was 23.05 kJ/mol for the whole falling rate period.

Effect of air velocity on kinetics of thin layer carrot pomace drying

Carrot pomace is a by-product obtained during carrot juice processing. Thin layer carrot pomace drying was performed in a laboratory scale hot air forced convective dryer. The drying experiments were carried out at the air velocity of 0.5, 0.7 and 1.0 m/s at air temperatures from 60 to 75 °C. It was observed that whole drying process of carrot pomace took place in a falling rate period except a very short accelerating period at the beginning. Mathematical models were tested to fit drying data of carrot pomace. The best fit model was observed on the basis of R2, Chi-square and RMSE values. R2 values for all the selected models were above 0.9783. The average values of effective diffusivity ranged from 2.61 × 10−9 to 3.64 × 10−9 m2/s.