Design of Continuous Flow Osmotic Dehydration and its Performance on Mass Transfer Exchange During Osmotic Dehydration of Broccoli Stalk Slices

Investigating intermittent immersion during osmotic dehydration of mango (Mangifera indica L. Moench). Part B mathematical modeling of D2I and D3I kinetics in mango (Mangifera indica L. Moench) slices

This work aims to investigate the dynamics of water loss (WL) and solute gain (SG) during dehydration impregnation by immersion (D2I) and intermittent immersion (D3I). WL and SG of mango slices, 4 × 1 × 1 cm3 in size, during dehydration immersion impregnation (D2I) and dehydration impregnation by intermittent immersion (D3I) were determined at 35, 45 and 55 °C for 270 min. Mango slices were immersed in a hypertonic sucrose solution of (61.6 ± 0.2) °Brix at a ratio of 6 mL of hypertonic solution per gram of fruit. Five semi-empirical models, two of which have been modified, were used to study mass transfer during D2I and D3I, namely the Azura, Weibull, Crank, Modified Crank I, and Modified Crank II models. The equilibrium water loss (WL ∞ ), the equilibrium solute gain (SG ∞ ), the diffusion coefficient, and activation energy were determined using the Modified Crank II model which was the best of all the tested models. Equilibrium water loss during D2I decreased with increasing temperature, while during D3I it increased with temperature. TheSG ∞ during D2I and D3I increases with temperature but was higher in D2I than in D3I. The average water diffusion coefficients were (6.02 ± 2.62) × 10-8 m2 s-1 for D2I and (4.89 ± 0.55) × 10-8 m2 s-1 for D3I and the average solute diffusion coefficients were (4.45 ± 0.53) × 10-8 m2 s-1 for D2I and (8.33 ± 0.79) × 10-8 m2 s-1 for D3I. The activation energies for WL in D2I and D3I were respectively 38789 J mol-1 and 9503 J mol-1. The respective values for SG were 9037 J mol-1 and 7327 J mol-1. This work demonstrates that mass transfers in D3I are better than those in D2I, and it highlights that, unlike the D2I process, the D3I process is less sensitive to temperature variations, making it particularly advantageous for processing products with high nutritional value.

Review of osmotic dehydration: Promising technologies for enhancing products' attributes, opportunities, and challenges for the food industries

Osmotic dehydration (OD) is an efficient preservation technology in that water is removed by immersing the food in a solution with a higher concentration of solutes. The application of OD in food processing offers more benefits than conventional drying technologies. Notably, OD can effectively remove a significant amount of water without a phase change, which reduces the energy demand associated with latent heat and high temperatures. A specific feature of OD is its ability to introduce solutes from the hypertonic solution into the food matrix, thereby influencing the attributes of the final product. This review comprehensively discusses the fundamental principles governing OD, emphasizing the role of chemical potential differences as the driving force behind the molecular diffusion occurring between the food and the osmotic solution. The kinetics of OD are described using mathematical models and the Biot number. The critical factors essential for optimizing OD efficiency are discussed, including product characteristics, osmotic solution properties, and process conditions. In addition, several promising technologies are introduced to enhance OD performance, such as coating, skin treatments, freeze-thawing, ultrasound, high hydrostatic pressure, centrifugation, and pulsed electric field. Reusing osmotic solutions to produce innovative products offers an opportunity to reduce food wastes. This review explores the prospects of valorizing food wastes from various food industries when formulating osmotic solutions for enhancing the quality and nutritional value of osmotically dehydrated foods while mitigating environmental impacts.

Influence of physical and chemical modifications on granule size frequency distribution, fourier transform infrared (FTIR) spectra and adsorption isotherms of starch from four yam (Dioscorea spp.) cultivars

Abstract

In this work, the effect of the modifications (annealing, acid hydrolysis and citric acid substitution) on starch granule size frequency distribution, Fourier Transform Infrared (FTIR) spectra, and adsorption isotherm of starches of four yam cultivars were studied. The native and modified white yam, water yam, and yellow yam starches had a normal distribution frequency profile for the granule sizes, which were similar among the cultivars. In contrast, the native and modified bitter yam starch granules were not normally distributed. The modifications resulted in a left shift in normal distribution frequency profiles for the granules sizes of the white, water and yellow yam starches due to broadening of the range of granule sizes. The FTIR spectra revealed that additional bands at 1726.95-1729.49 cm^-1 were introduced due to citric acid modification of the yam starches. The modifications also caused weakening of the FTIR band representing -CH₂ and -OH stretching at 2927.85-2932.94 cm^-1 and 3259.42-3437.33 cm^-1, respectively. The native, annealed and acid hydrolyzed yam starches all had similar adsorption isotherms at 28 °C. On the other hand, the citric acid-substituted yam starches showed a different adsorption isotherm, because they had significantly higher equilibrium moisture content at water activity (a _w ) above 0.9. All the adsorption isotherms were type III, J-shaped isotherms. The adsorption isotherms data of the yam starches fitted best to the Guggenheim-Anderson-De Boer (GAB) model. The GAB model monomolecular moisture content ranged between 0.0165 and 0.0597 g/g db.

Article Highlights

Native and modified yam starches' granules size were normally distributed except bitter yam starchFTIR revealed additional bands and molecular rearrangements were introduced due to modificationsAdsorption isotherms revealed type III, GAB-model isotherms with low monomolecular moisture.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-021-05200-7.

Dataset on influence of drying variables on properties of cassava foam produced from white- and yellow-fleshed cassava varieties

Freshly harvested cassava has a tendency to deteriorate rapidly in its physiological properties after harvest. Therefore, cassava is often processed using a number of unit operations in order to derive a stable, storable product of acceptable eating quality. Among the unit operations employed, drying is considered as one of the oldest and most important process in arresting deterioration of cassava. In recent times, more researchers are considering foam mat drying as a drying technique for tuber or root crops, although the technique is used, ideally, for fruit juices and dairy. Cassava foam production from white and yellow cassava varieties has been optimized in our previous work [1]. Our data were procured from experimentally measuring mass of cassava foams of white and yellow cassava varieties dried at different temperatures (50, 65, 80 °C) and foam thicknesses (6, 8, 10 mm) over regular drying intervals until no considerable mass change was observed. The mass measurements are the primary datasets used in determination of secondary datasets presented here as moisture removal ratio (MR), effective moisture diffusivity (D_eff), and drying rate (DR). The MR data were fitted to four thin-layer drying models (Henderson-Pabis, Page, Newton, Two-term), and Page model described the experimental drying data best. The Page model coefficients were analyzed by multiple linear regression (MLR) analysis to show how they are influenced by the drying variables. Drying rate was also fitted by Rational model to fit the DR data and to reflect the two falling rates found. Statistical accuracy and significance were calculated as coefficient of determination (R²), root mean square error (RMSE) and Chi square (χ²) and an analysis of variance (ANOVA). Data obtained here are useful as primary data in process and dryer designs and processing of cassava in the cassava industry.

Effect of Drum-Drying Conditions on the Content of Bioactive Compounds of Broccoli Pulp

This work studied the effect of drum-rotation frequency, drum temperature, and water-to-pulp ratio in a double-drum drier on the content of sulforaphane, glucoraphanin, total phenolic compounds, ascorbic acid, and antioxidant activity of broccoli pulp through a multilevel factorial design with one replicate. Drum-drying conditions did not significantly affect sulforaphane content, unlike glucoraphanin, however the poor adherence of broccoli pulp resulted in a final product with undefined shape and heterogeneous color. On the other hand, antioxidant activity was unevenly affected by drying conditions; however, drum-rotation frequency affected it in the same way that phenolic compounds and ascorbic acid, showing a concordant behavior. The ascorbic acid content decreased significantly after drying, and it was highly dependent on the experimental factors, resulting in a regression model that explained 90% of its variability. Drum-rotation frequency of 5 Hz, drum temperature of 125 °C, and water-to-pulp ratio of 0.25 resulted in an apparent increase of sulforaphane and phenolic compounds content of 13.7% and 47.6%, respectively. Drum drying has great potential to fabricate dehydrated broccoli-based foods with functional properties. Besides, since drum drying has low investment and operation costs, it represents a very attractive option for the industrialization of broccoli derivatives.

Osmotic dehydration kinetics of biofortified yellow-flesh cassava in contrast to white-flesh cassava (Manihot esculenta)

In recent times, the cultivation, processing and consumption of biofortified yellow-flesh cassava is of significant interest to breeders and food processors due to its relatively high pro-vitamin-A content, compared to the conventional white-flesh cassava. In light of this, osmotic dehydration (OD) kinetics of a recently released biofortified yellow-flesh cassava was compared to that of a white-flesh cassava, using salt, sugar, and salt-sugar solutions at different temperatures (30, 45, 60 °C) and fixed cube/solution-ratio. Water loss (WL) and solids gain (SG) data were fitted by non-linear regression using four models (Page, Weibull, Azuara, and Peleg). Azuara model was most appropriate in describing OD kinetics for both cultivars. Azuara estimates for equilibrium WL and equilibrium SG, respectively, ranged between 0.101-0.120 and 0.049-0.094 g/g for salt solution, 0.158-0.212 g/g and 0.107-0.268 g/g for sugar solution and 0.234-0.306 g/g and 0.189-0.276 g/g for salt-sugar solution. The best conditions for OD of both cultivars by salt solution and sugar solution was at 60 °C and 45 °C, respectively, while that for salt-sugar solution varied with cultivar. Increasing temperature increased water loss and solids gain. Salt-OD conformed to Arrhenius temperature dependence of diffusivity, but sugar-OD and salt-sugar-OD did not. Micrographs reveal biofortified yellow-flesh cassava was more susceptible to cell wall collapse than white-flesh cassava. Extent of dehydration by OD agents ranked: salt-sugar > sugar > salt. Osmotic dehydration may be useful as a means of dehydration for cassava prior to drying, and is especially relevant for the carotenoids-rich biofortified yellow cassava.