Refractance Window Research Articles

Effect of cyclic vacuum-steam blanching on the quality characteristics and functional properties of Malabar spinach (Basella alba) dried by non-water infrared Refractance window drying

In the present work, an effluent-free novel method including cyclic vacuum-steam pulsed blanching (VSPB) pretreatment and non-water infrared refractance window drying (non-water IR-RWD) was employed to explore its effect on enzyme inactivation, drying behavior, quality and functional properties of dried Malabar spinach. The highest inactivation of peroxidase (90.23 %) and polyphenol oxidase (94.58 %) was observed in the 4th cycle of the VSPB pretreatment. With the increase in VSPB cycles from 1 to 5, the drying time was significantly reduced by 27.27 % to 55.45 % compared to the untreated sample. The color change values (ΔE) of VSPB pretreated non-water IR-RWD samples varied from 7.37 to 8.03. The findings in the current work indicated that vacuum-steam pulsed blanching combined with a non-water IR-RWD process is a promising technique for Malabar spinach powder production.

Smart next-gen drying solution: A study of design, development and performance evaluation of IoT-enabled IR-assisted refractance window dryer

Refractance window drying is a technique that has great potential to dry commodities, with better quality at an affordable cost. However, there is still a lack of awareness regarding its use and implementation in academic curricula as well as in industry. This study aims to design and develop a low-cost and effective Internet of Things (IoT) enabled Infrared (IR) assisted refractance window dryer. The effect of different flexible materials used as membranes with the same thickness was also investigated. Then, experiments were conducted on papaya pulp to study the performance of the developed dryer. The drying time (reduced moisture content up to 4%) was observed for the papaya pulp sample by employing Low-density polyethylene (LDPE), Polypropylene (PP), Polytetrafluoroethylene (PTFE), White Polyethylene Terephthalate (W-PET) and Transparent polyethylene terephthalate (T-PET) material as a membrane were 300, 330, 360, 330, and 300 min respectively. After thoroughly testing membrane materials properties, it is concluded that the T-PET membrane has superior thermal, mechanical, and optical properties. After an exhaustive examination of the marketplace scrutiny, the payback period was found to be 0.55 years.

Evaluation of drying techniques for postharvest residue utilization in 'Nufar' Basil (Ocimum basilicum L.) production

In this study, drying techniques including lyophilization, forced convection, marquee with polyshade, and refractive window were evaluated in the post-harvest residue of Nufar variety basil (Ocimum basilicum L.) in the department of Tolima, Colombia. The physicochemical and bromatological analysis showed that lyophilization and forced convection better maintained the organoleptic properties of dry basil, while the marquee with polyshade technique did not affect the phenolic content and antioxidant capacity. The refractive window technique showed higher rehydration capacity but lower essential oil content. In the sensory evaluation, the infusions of dried leaves in the marquee with polyshade method were highly accepted. The results suggest that drying by forced convection and marquee with polyshade are effective methods to preserve the quality of dried basil, presenting a viable alternative for the use of post-harvest residue and improving the useful life of the product, benefitting local producers by increased employability and added value.

Refractance window drying of Spanish cherry (Mimusops elengi Linn) pulp: Impacts on drying kinetics, color, and phytochemical properties

In present study, Spanish cherry pulp (SCP) was dried using refractance window (RW) dryer at varying temperatures (50 to 90 °C) to investigate the impacts on drying kinetics and physicochemical properties and compared with freeze-dried samples. An increasing RW drying temperature from 50 to 90 °C reduced drying time from 320 to 80 min. The water and oil absorption capacity showed no significant (p < 0.05) changes in RW-dried SCP samples. Noticeable changes in color values, ascorbic acid, β-carotenoid, total phenol content, total flavonoid content, and antioxidant activity were observed on increasing RW drying temperature. As per results, compared to control, RW drying at 50 °C retained most of the nutrients. From nutrient retention perspective, RW drying at 80 and 90 °C may not be suitable SCP samples. From multivariance analysis, RW drying of SCP samples can be performed at 60 °C instead of 70 °C for better nutrient contents.

Determination of Drying Characteristics and Physicochemical Properties of Mint (Mentha spicata L.) Leaves Dried in Refractance Window.

Drying is one of the most common and effective techniques for preserving the quantitative and qualitative characteristics of medicinal plants in the post-harvest phase. Therefore, in this research, the effect of the new refractance window (RW) technology on the kinetics, thermodynamics, greenhouse gasses, color indices, bioactive properties, and percentage of mint leaf essential oil was investigated in five different water temperatures in the form of a completely randomized design. This process was modeled by the methods of mathematical models and artificial neural networks (ANNs) with inputs (drying time and water temperature) and an output (moisture ratio). The results showed that with the increase in temperature, the rate of moisture removal from the samples increased and as a result, the drying time, specific energy consumption, CO2, NOx, enthalpy, and entropy decreased significantly (p < 0.05). In addition, the drying water temperature had a significant effect on the rehydration ratio, color indices, bioactive properties, and essential oil percentage of the samples (p < 0.05). The highest value of rehydration ratio was obtained at 80 °C. By increasing temperature, the main color indices such as b*, a*, L*, and Chroma decreased significantly compared to the control (p < 0.05). However, with the increase in temperature, the overall color changes (ΔE) and L* first had a decreasing trend and then an increasing trend, and this trend was the opposite for the rest of the indicators. The application of drying water temperature from 50 to 70 °C increased antioxidant, phenol content, and flavonoid content, and higher drying temperatures led to a significant decrease in these parameters (p < 0.05). On the other hand, the efficiency of the essential oil of the samples was in the range of 0.82 to 2.01%, and the highest value was obtained at the water temperature of 80 °C. Based on the analysis performed on the modeled data, a perceptron artificial neural network with 2-15-14-1 structure with explanation coefficient (0.9999) and mean square error (8.77 × 10-7) performs better than the mathematical methods for predicting the moisture ratio of mint leaves.

Comparison of Mango (Mangifera indica) Dehydration Technologies: A Systematic Review

The convective hot-air drying technology can cause physicochemical, nutritional, and organoleptic losses in the mango (Mangifera indica). The present Systematic Review was carried out with the objective of comparing mango dehydration technologies to identify the effects on the physicochemical, nutritional, and organoleptic properties of the fruit. Through a review of published scientific and conference papers in the Scopus database, adjusted to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) methodology, a total of 134 documents dated between 2000 and December 6 of 2022 were obtained; 76 of these documents were finally included in the bibliographic and theoretical analysis. Selection parameters emphasizing the relationship between the articles and the research topic, evidenced by including at least one of three dehydration technologies and the fruit of interest with an experimental or theoretical approach to the dehydration subject; review articles and surveys were excluded. Correlation graphs of bibliographic variables were made using the data mining software VantagePoint (version 15.1) , which was graphically restructured in Microsoft Excel with the support of statistical analysis. Of the resulting articles, it was found that the countries with authors who participated most in scientific production like India, Brazil, Colombia, the United States, and Thailand, were those related to mango production or importation. Furthermore, the freeze-drying technology allows operating at lower temperatures than convective hot-air drying, contributing to the preservation of ascorbic acid, among other compounds. The refractance window has the shortest operation time to obtain moisture values between 10 and 20%. The dehydrated samples using the refractance window are smooth, homogeneous, non-porous, and comparable to the color obtained with freeze-drying, which is acceptable for industrial applications.

Synergistic Effect of Advanced Refractance Window Drying on Quality Characteristics of Potato Slices and Numerical Process Optimization

Synergistic Effect of Advanced Refractance Window Drying on Quality Characteristics of Potato Slices and Numerical Process Optimization

Evaluation of energy efficiency and quality parameters by drying beets with a refractive window (Betavulgaris)

This study evaluated the energy efficiency associated with drying by refractance window™ and its effect on the physical and chemical properties of beetroot in two different physical states, in semisolid (puree type) and solid (slices) were compared. The refractance window™ drier was compared to a tray dryer at 70 °C on the food surface. The drying time was calculated through the kinetics in both dryers in both physical states of the beetroot determining the moisture content at the beginning and the end of the drying process after which water activity and color retention were determined. Total polyphenol and flavonoid contents respectively, and antioxidant activity were evaluated. Overall energetic efficiency for both dryers was calculated. The beetroot dried in semisolid state using the refractance window™ technology retained color and showed no differences when compared with fresh beetroot. No significant differences in total polyphenol content and total flavonoid content when compared with the fresh sample after application of the refractance window™ were found. The overall energetic efficiency was higher after using refractance window™ drying in beetroot in the two physical states and produced greater retention of quality parameters when compared with the tray dryer.

Effect of foaming and drying temperature on the physical, chemical, and functional properties of egg white powders produced using refractance window drying

This study investigated the effect of drying form (natural and foamed) and temperature (50–100 °C) on the physical, chemical, and functional properties of egg white powder produced using refractance window drying. The egg whites were dried in 4-55 min, depending on the drying conditions. On the one hand, the drying form was effective on the color properties, densities (bulk, tapped, or particle), Carr index, Hausner ratio, porosity, hygroscopicity, solubility, and foaming capacity of egg white powders. On the other hand, the drying temperature was effective for all analyzed properties except hygroscopicity, moisture content, and water activity of samples. The study demonstrated that foaming before refractance window drying enhances the color of the egg white powders and provides better solubility and foaming capacity. However, it has a detrimental effect on the flow properties of the powders evaluated according to the Carr index and Hausner ratio. Increasing the drying temperature until a certain extent (80 °C) generally provided better color, protein content, surface hydrophobicity, and functional properties. The study shows that egg powders suitable for different purposes (better foaming, low protein denaturation, better gelling, etc.) can be obtained if the drying form and temperature conditions are fine-tuned.

Moisture sorption isotherm and thermodynamic analysis of egg powders dried by foam-mat-assisted refractance window drying.

In the designed study, the moisture sorption isotherm and thermodynamic properties of refractance-window-dried egg white powder (EWP), egg yolk powder (EYP) and whole egg powder (WEP) were determined. The adsorption isotherm of egg powders was classified as type II, giving a sigmoidal shape. Peleg showed the highest goodness of fitting for egg powder. The monolayer moisture content of egg powders varied between 0.02 and 0.09 g g-1. According to the thermodynamic analysis, an increase in moisture content led to a decrease in net isosteric heat of sorption (qst), and the highest decrease was observed in EWP. The qst of EWP was calculated as 18 637 kJ mol-1, while it decreased to 3104 kJ mol-1 at 0.2 g g-1 moisture content. Like qst, sorption entropy decreased from 52.07 to 7.14 J mol-1 K-1 with increasing water activity (aw) for EWP. Increasing temperature caused a decrease in spreading pressure and was higher in EWP samples. Increasing moisture content and temperature also decreased Gibbs free energy level. Moisture sorption isotherm (MSI) is used to predict the amount of bound water in a material at a specific relative humidity and temperature. To inhibit chemical and microbiological spoilage, the drying process must continue until the monolayer moisture content is reached. In this study, the monolayer moisture content of powdered eggs for safe storage was demonstrated by MSI. Additionally, by determining the thermodynamic functions of egg powder, valuable information was obtained related to predicting the energy requirement in drying processes. © 2024 Society of Chemical Industry.

Optimization of process parameters of refractance window drying for aonla slices and comparison with other drying techniques.

Aonla is as a good source of antioxidants due to its high ascorbic acid and polyphenol contents. However, because of its high acidity and astringent taste, aonla is rarely consumed in its fresh form. As the constituents in aonla are heat sensitive, it is essential to find a suitable drying method for preservation. Therefore, refractance window drying (RWD) of aonla slices was studied as it has the potential of retaining heat-sensitive compounds. The effect of RWD process variables, namely water temperature (75, 82.5, 90 °C) and slice thickness (2, 4, 6 mm), on different quality parameters of dehydrated aonla was studied. Increasing water temperature resulted in significantly higher ascorbic acid content, titratable acidity and product temperature, while total phenolic content, free radical scavenging activity and moisture content decreased. With the exception of product temperature, higher slice thickness led to an increase in the values of all the parameters. At the optimized processing conditions of 83 °C water temperature and 4 mm slice thickness, the ascorbic acid content, total phenolic content, free radical scavenging activity, titratable acidity and moisture content values were found to be 269.03 mg (100 g)-1, 242.33 mg (100 g)-1, 87.11%, 3.62% and 4% respectively. The aonla slices subjected to RWD also possessed 4-6% higher phytochemical content than osmotically dried and hot-air-dried samples. This research highlights the effectiveness of RWD in preserving heat-sensitive compounds in food like aonla. The RW-dried slices had a smoother and more uniform microstructure compared to osmotically dried and hot-air-dried samples. © 2024 Society of Chemical Industry.

Development of an Apple Snack Enriched with Probiotic Lacticaseibacillus rhamnosus: Evaluation of the Refractance Window Drying Process on Cell Viability.

The objective of this study was to develop a dried apple snack enriched with probiotics, evaluate its viability using Refractance Window (RWTM) drying, and compare it with conventional hot air drying (CD) and freeze-drying (FD). Apple slices were impregnated with Lacticaseibacillus rhamnosus and dried at 45 °C using RWTM and CD and FD. Total polyphenol content (TPC), color (∆E*), texture, and viable cell count were measured, and samples were stored for 28 days at 4 °C. Vacuum impregnation allowed for a probiotic inoculation of 8.53 log CFU/gdb. Retention values of 6.30, 6.67, and 7.20 log CFU/gdb were observed for CD, RWTM, and FD, respectively; the population in CD, RWTM remained while FD showed a decrease of one order of magnitude during storage. Comparing RWTM with FD, ∆E* was not significantly different (p < 0.05) and RWTM presented lower hardness values and higher crispness than FD, but the RWTM-dried apple slices had the highest TPC retention (41.3%). Microstructural analysis showed that RWTM produced a smoother surface, facilitating uniform moisture diffusion and lower mass transfer resistance. The effective moisture diffusion coefficient was higher in RWTM than in CD, resulting in shorter drying times. As a consequence, RWTM produced dried apple snacks enriched with probiotics, with color and TPC retention comparable to FD.

Effect of Refractance Window™ and oven drying on physicochemical and sensory properties of peach (Prunus persica L.) surplus.

Currently, approximately 34% of fruit is lost and wasted in emerging economies due to inefficient post-harvest processes, technological shortcomings, lesser valorization of surpluses, and byproducts. Peach (Prunus persica L.) is a fruit with a good yearly growth rate but higher postharvest losses in Colombia. One way to take advantage of this type of product is through the application of drying processes that increase its shelf life and its inclusion in the food chain. Refractance Window Drying (RWD) is a fourth generation drying technique implemented by the food industry in the last few decades and has been applied to several dehydrated food products. This study compared the effects of different drying methods on the physical and sensory properties of peaches surplus. Treatments consisted of (i) peaches were sliced (1, 2, and 3 mm thickness) and dried using RWD at 86°C, (ii) peach pulp mixed with maltodextrin (MD) (0.12-0.33 kg of MD/kg of sample) and RWD (RWD-MD), and (iii) conventional oven drying (OD) at 60°C (3 mm thick) dried for 24 h. The study found that the drying method significantly (p < 0.05) affected the texture, color, and general taste of peaches. The results showed that processing treatments combined with different drying conditions affected the physical properties of the peach. RWD in slices reduced water content to 0.05 kg H2O/kg in 40 min, showing fewer effects on color attributes. A surface response analysis on RWD showed good correlations for water activity (R2 = 0.8652-0.9894) and moisture content (R2 = 0.7048-0.9826). A higher diffusion coefficient (1.63 × 10-6 m2 s-1) was observed for RWD in slices with 3 × 10-3 m of thickness; however, for RWD-MD, differences in diffusion coefficients were present for the lowest MD addition (0.12 kg/kg), vitamin C was not detected on the dried slices, and higher concentration of β-carotene (175.88 μg/100 g) was found on the thinner slices. Principal component analysis showed that RWD in the slices was the most suitable drying process, followed by OD. Sensory analysis showed good acceptability for RWD slices after 30 days of storage.

Combined refractance window and far infrared radiation drying of Spirulina platensis biomass: Drying behavior, moisture and thermal diffusivity, and biochemical characterization

A 2 mm thin layer of wet Spirulina platensis biomass was dried using two methods: refractance window drying (RW) and combined RW and FIR drying (RWF). The effect of drying temperature (40–60 °C) and proximity to FIR heaters (5 and 10 cm) was evaluated on falling rate drying characteristics. The moisture (Deff) and thermal (α) diffusivity coefficients were obtained in the range 1.728 × 10−8 to 5.289 × 10−9 and 1.322 × 10−8 to 4.169 × 10−9 m2 s−1, respectively (R 2, 0.921–0.984). RW drying at ≥50 °C caused loss of color, phytopigments, and lipid peroxidation. At 40 °C, RW drying led to a long drying period (300.50 ± 3.53 min), poor drying rate (0.039 ± 0.002 g-H2O/min), lowest Deff and α (5.289 × 10−9 and 4.169 × 10−9 m2 s−1), and chlorophyll loss (32.2%). Combined RW and FIR drying at 40 °C and 5 cm proximity (RWF40-5cm) reduced drying time (15.1%), increased drying rate (27.8%), improved α (15%), and Deff (14.9%). RWF40-5cm dried biomass showed excellent retention of color (ΔE = 4.64 ± 1.32), protein (93.8%), γ-linolenic acid (90.1%), chlorophyll (87.9%), and phycocyanin (86.7%) from freeze-dried biomass (FD). Low-temperature RWF40-5cm drying could be a potential alternative to freeze-drying for effective and safe drying of heat-sensitive Spirulina platensis biomass.

Effects of instant controlled pressure drop treatment combined with refractance window drying on infusion quality of made green tea.

The study aimed to determine the effects of instant controlled decompression of steam pressure, termed as ICPD (instant controlled pressure drop) on fresh tea leaves, when combined with refractance window drying (RWD) of rolled green teas during green tea manufacturing. The ICPD steam treatment pressure (TP; 0.1-0.3 MPa), treatment time (TT; 10-20 s) and refractance window drying temperature (RWDT; 70-90 °C) were used as the processing parameters for manufacturing of green tea. Response surface methodology was employed to enumerate the effects of ICPD process conditions and temperature of RWD on total phenolic content (TPC), total flavonoid content (TFC) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity of the green tea infusion. An optimum condition for green tea processing was found at TP 0.2 MPa, TT 20 s with RWDT at 70 °C. In comparison to made green tea manufactured without ICPD treatment, the ICPD treated green tea showed enhanced TPC, TFC and DPPH radical scavenging activity along with better colour and sensory attributes. The microstructural study of ICPD treated green tea samples showed more deformed cell surface integrity, larger stomatal pore size and cracks at the leaf surface in comparison with non-treated green tea sample. Present study reveals that an ICPD treatment at 0.2 MPa for 20 s can be used as an alternative to the traditional enzyme inactivation step of hot water treatment, for green tea leaves to improve the infusion quality in terms of increased levels of TPC and TFC and DPPH radical scavenging activity. © 2024 Society of Chemical Industry.

Response Surface Optimization of Refractance Window Drying of Bitter Gourd Slices

This study was conducted to investigate the drying behavior of bitter gourd (Momordica charantia L.) slices in a refractance window dryer. Various drying parameters such as water temperature (70, 80 and 90 °C), sample thickness (1, 2 and 3 mm) and blanching time (2, 3 and 4 min) were investigated for their effects on drying time, dehydration ratio and color change. Out of the 18 experimental runs determined by the Box Behnken design, six central experiments, often referred to as center points, were specifically chosen to assess the reliability of results. Four different empirical models viz. Exponential, Henderson and Pabis, Page's, and Power law model were selected based on their established applicability in similar studies, and fitted to the kinetics data of refractance window drying of bitter gourd. Adequacy of fit was assessed using the coefficient of determination (R2 ) and standard error of estimate (SEE). Page’s model demonstrated an excellent fit to the experimental drying data with a higher R2 value of 0.996 and correspondingly lower SEE of 0.0217 compared to the other three models. Furthermore, the drying process parameters were optimized for the responses using the Response Surface Methodology (RSM). The best values (within the chosen range) of water temperature, sample thickness and blanching time were found to be 90 °C, 1 mm and 4 min, respectively at desirability value of 0.889. At above condition of water temperature (90 °C), sample thickness (1 mm) and blanching time (4 min), the predicted values for the drying time, dehydration ratio and color change were found to be 52.2 min, 9.7 and 55.25, respectively. The findings of this study will be useful for refractance window drying of bitter gourd in particular and for high moisture foods in general.

Viability of Lactobacillus reuteri DSM 17938 Encapsulated by Ionic Gelation during Refractance Window® Drying of a Strawberry Snack.

The selection of appropriate probiotic strains is vital for their successful inclusion in foods. These strains must withstand processing to reach consumers with ≥106 CFU/g, ensuring effective probiotic function. Achieving this in commercial products is challenging due to sensitivity to temperature during processing. In this work, Lactobacillus reuteri DSM 17938 was microencapsulated by ionic gelation (with alginate or pectin) followed by polymeric coating (with whey protein concentrate or chitosan). Then, such microcapsules were incorporated into a strawberry puree, which was subsequently dehydrated at three temperatures (40 °C, 45 °C, and 50 °C) by Refractance Window®. The ultimate aim was to demonstrate the efficacy of the proposed methods from a technological point of view. Kinetic curves of the probiotic's viability showed a high cell loading (>109 CFU/g). Additionally, an average encapsulation efficiency of 91% and a particle size of roughly 200 µm were found. A decrease in the viability of the microorganism was observed as drying temperature and time increased. As a demonstration of the above, in a particular case, drying at 45 °C and 50 °C, viable cells were found up to 165 min and 90 min, respectively; meanwhile, drying at 40 °C, viable cells were reported even after 240 min. The greatest viability preservation was achieved with Refractance Window® drying at 40 °C for 240 min when microcapsules coated with whey protein concentrate were incorporated into puree; this procedure showed great potential to produce dehydrated strawberry snacks with moisture (15%), water activity (aw < 0.6), and viability (≥106 CFU/g) suitable for functional foods. The membrane-stabilizing properties of whey protein concentrate could prevent cell damage. In contrast, probiotics in chitosan-coated capsules showed reduced viability, potentially due to antimicrobial properties and the formation of cracks. These findings signify a breakthrough in the production of dehydrated snacks with the addition of probiotics, addressing challenges in preserving the viability of these probiotics during processing; thus, opening the possibility for the development of a probiotic strawberry snack.

Evaluation of refractance window-dried type 3 sourdough as an alternative to liquid sourdough in bread production

The aim of this study was to produce type 3 sourdough using refractance window drying (RWD) and to compare the effects of dried and liquid sourdough on bread quality. The drying experiments resulted in a similar viability loss in the total LAB counts of type 3 sourdough samples (p < 0.05), with a 3-log reduction, and the lowest loss in yeast viability was determined in spontaneous sourdough samples. The specific bread volume was in the range of 3.18–3.24 mL/g in the usage of liquid sourdough and 2.75–3.12 ml/g in type 3 sourdough, respectively. The incorporation of type 3 sourdough increased the hardness of bread. The total cell counts, and area was statistically similar in bread produced using liquid spontaneous sourdough and dried Lb. fermentum. When sensory parameters were evaluated, it became evident that sourdough bread produced by dried sourdough exhibited superior organoleptic qualities when compared to those produced by the liquid ferment. As a conclusion, the findings of this study suggest that the application of RW-dried type 3 sourdough can be considered as an alternative to liquid sourdough, without any adverse effect on the physical and sensory attributes of the sourdough bread.

Modified refractance window drying of jamun pulp (Syzygium cumini) based on innovative infrared and microwave radiation techniques

The present study aimed to dry jamun pulp (Syzygium cumini) by combining infrared and microwave energy in refractance window drying. The two different sets of experiments were planned using the hybrid design. The three independent parameters considered for the infrared refractance window drying (IR-RWD) included infrared lamp power (30–70% of the 1000 W lamp), pulp layer thickness (1–3 mm), and distance between the lamp and pulp layer (3.42–6.60 cm). In microwave refractance window drying (MW-RWD), the independent variables were oven-set microwave power (150–450 W), pulp layer thickness (1–3 mm), and power density (1–2.5 W g−1). The optimum conditions in IR-RWD were 40.75% infrared lamp power, 1 mm pulp layer thickness, and 3.42 cm distance between the lamp and pulp layer, resulting in dry jamun flakes with 17.93 ± 0.32 mg GAE g−1 total phenolic content, 4.37 ± 0.13 color change, 8.90 ± 0.22 mg QE g−1 total flavonoid content, and 179.05 ± 2.17 C3G mg/100g total anthocyanin content. In the case of MW-RWD, the optimum conditions were 212.4 W oven-set microwave power, 3 mm pulp layer thickness, and 2.2 W g−1 power density, resulting in 15.68 ± 0.28 mg GAE g−1 total phenolic content, 8.47 ± 0.25 color change, 8.20 ± 0.21 mg QE g−1 total flavonoid content, and 149.72 ± 1.81 C3G mg/100g total anthocyanin content. The Page model can precisely describe the jamun pulp drying behavior of IR-RWD and MW-RWD. Also, apparent moisture diffusivity was estimated in both drying methods. IR-RWD was found to be a better drying method than MW-RWD in terms of drying rates and the quality parameters of the dry jamun flakes.

Conductive hydro drying of ripened papaya: optimization and product characterization.

This study addresses the product-process characterization of refractance window drying of ripened papaya, considering the abundant availability and underutilization of the perishable product. A statistical design approach with varied drying temperature, time and sample thickness has been adopted to characterize moisture content, total phenolic content, total flavonoid content, vitamin C, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. The model fitting, analysis of variance, and numerical optimization showed that the quadratic model was the most suitable model for the response variables. The optimum process parameters were attained at a drying temperature of 90°C, time 86.92min, and sample thickness of 2.93mm. The optimal responses were moisture content 2.81%, total phenolic content 305.58mg GAE/g, total flavonoid content 51.92mg QUE/g, DPPH radical scavenging activity 91.56% and vitamin C 219.88mg/100g. With such high essential nutrients, refractance window dried ripened papaya can be utilized for commercially viable value-added food products.