Kinetic modelling of drying and conversion/degradation of isoflavones during infrared drying of soybean

Green extraction of isoflavones from okara using subcritical water: Kinetics, optimization, and comparison with other water-based sustainable methods

Water has been explored as a green extraction agent for isoflavone extraction from okara. First, subcritical water (subW) was explored using two different okaras: (1) washed and dried (OKW) and (2) non-pretreated (OKC). Genistein family was the most abundant, with very low quantities in the glycitein family. Kinetic data revealed interconversion of malonyl-glycosides to β-glycosides in subW, with increasing degradation rate constants for all isoflavones with temperature. A maximum of 1229 μg isoflavone/g of dried okara was obtained at 120 °C after 30 min for OKC. Microwave (MAE) and ultrasound (UAE) technologies achieved 72.8 % and 75.4 %, of the yield of subW. Productivity at the maximum was of 41.0, 82.5 and 92.8 μg isoflavone/g dry okara min for subW, MAE, UAE. However, higher fraction of the more bioavailable forms β-glycoside + aglycone was obtained by subW.

Functional characterization and structural basis of a reversible glycosyltransferase involves in plant chemical defence

Plants experience numerous biotic stresses throughout their lifespan, such as pathogens and pests, which can substantially affect crop production. In response, plants have evolved various metabolites that help them withstand these stresses. Here, we show that two specialized metabolites in the herbaceous perennial Belamcanda chinensis, tectorigenin and its glycoside tectoridin, have diverse defensive effects against phytopathogenic microorganisms and antifeeding effects against insect pest. We further functionally characterized a 7-O-uridine diphosphate glycosyltransferase Bc7OUGT, which catalyses a novel reversible glycosylation of tectorigenin and tectoridin. To elucidate the catalytic mechanisms of Bc7OUGT, we solved its crystal structure in complex with UDP and UDP/tectorigenin respectively. Structural analysis revealed the Bc7OUGT possesses a narrow but novel substrate-binding pocket made up by plentiful aromatic residues. Further structure-guided mutagenesis of these residues increased both glycosylation and deglycosylation activities. The catalytic reversibility of Bc7OUGT was also successfully applied in an one-pot aglycon exchange reaction. Our findings demonstrated the promising biopesticide activity of tectorigenin and its glycosides, and the characterization and mechanistic study of Bc7OUGT could facilitate the design of novel reversible UGTs to produce valuable glycosides with health benefits for both plants and humans.

Thermal conversion kinetics and solubility of soy isoflavones in subcritical water extraction

The conversion of isoflavones during subcritical water extraction were studied using first-order reaction kinetics modeling. Isoflavones were extracted from soybean using temperatures from 100℃ to 180℃ for 3 to 30 min. It was found that malonylgenistin was the most thermally unstable, with little being detected above 100℃. The optimal extraction temperatures for acetylgenistin (AG), genistin (G), and genistein (GE) were 120℃, 150℃, and 180℃, respectively. A larger sum of the numbers of both hydroxyl groups and oxygen molecules was associated with a lower melting point and optimal extraction temperature. Kinetics modeling of reaction rate constant k and activation energy E_a showed that all of the reaction rates tended to increase with temperature, with the relationship fitted well by a first-order model in nonlinear regression. For temperatures between 100℃ and 150℃, AG → G and AG → GE conversions showed the highest rate constants, but G → GE and G → D₃ (degraded G) conversions became dominant at 180℃. Chemical compounds studied in this article: genistein (PubChem CID: 5280961), genistin (PubChem CID: 5281377), 6″-O-malonylgenistin (PubChem CID: 15934091), 6″-O-acetylgenistin (PubChem CID: 5315831).

Acidic natural deep eutectic solvents as dual solvents and catalysts for the solubilization and deglycosylation of soybean isoflavone extracts: Genistin as a model compound

This study investigated the possibility of using green solvent natural deep eutectic solvents (NADESs) as dual solvent-catalysts for the solubilization and deglycosylation of soybean isoflavones. The deglycosylation behavior of genistin as a model compound in NADESs was compared. Acidic NADESs showed moderate solubility for genistin and could hydrolyze it to form genistein. The onset temperature of deglycosylation in the choline chloride/malic acid (Ch-Ma) was 60 °C. The solubilities of genistin in the Ch-Ma system were modeled. The dissolution process was endothermic and mainly enthalpy-driven. The deglycosylation followed first-order kinetics with a half-life (t_1/2) of 40 min at 90 °C. The method was validated using soybean isoflavone extracts as a substrate and the ratio of glycoside to aglycone in the extracts could be adjusted by changing the conditions. The methods have great potential in the extraction and preparation of ready-to-use isoflavone extracts from soybean and other legumes.

Influences of drying temperature and storage conditions for preserving the quality of maize postharvest on laboratory and field scales

Drying and storage methods are fundamental for maintaining the grain quality until processing. Therefore, the aim of this study was to evaluate the associations of the drying temperature with storage systems and conditions as a strategy for preserving the quality of maize grain postharvest on laboratory and field scales. An increase in temperature accelerated the reduction in grain moisture, but increased the deterioration. The wetting during the storage period reduced the grain quality. Hermetic and aerated storage systems maintained the chemical quality of the grains. The control with healthy and whole corn dried at 80 °C and stored in silos with natural aeration provided a satisfactory quality, equivalent to those of controlled drying and storage under airtight conditions and at low temperatures. Different conditions of drying and storage of corn on the laboratory and field scales were evaluated, which provides an appropriate management of these operations to maintain the grain quality.

Enzymatic pretreatment in the extraction process of soybean to improve protein and isoflavone recovery and to favor aglycone formation

This research aimed to evaluate the pretreatment of soybean with the carbohydrase multi-enzyme complex "Viscozyme L", during the extraction process; in order to improve the recovery of proteins and isoflavones in soybase, and reduce the loss of these compounds through the okara residue. Three concentrations of enzyme were studied at 50 °C, along with an experiment carried out without enzyme addition (control experiment). The results were also evaluated in relation to standard soybase processing. In comparison to the standard and control processes, the enzymatic pretreatment reduced up to 85% the total amount of okara residue. Due to the action of the multi-enzyme complex, protein and total isoflavone recovery increased from 42% to 83% and from 59% to 93%, respectively. The application of Viscozyme L also favored the conversion of conjugated forms of isoflavone to aglycone in the soybase, representing up to 50% of the total isoflavones. The enzymatic pretreatment of soybean with carbohydrase improved the nutritional quality of the soybase, while at the same time reducing residue generation; showing that the proposed food process can be considered environmentally friendly method.

Infrared drying of dill leaves: Drying characteristics, temperature distributions, performance analyses and colour changes

Thin-layer drying behaviour of dill leaves samples under three different infrared radiation power intensities was investigated. Diffusion Approach was found to be the best model that describes the drying behaviour of dill leaves. Effective diffusivity values were 6.97 × 10^-9, 6.84 × 10^-9 and 8.96 × 10^-9 m²/s for power intensities of 1790, 1970 and 2070 W/m², respectively. According to the first and second law efficiencies, the infrared drying system was more efficient at higher power intensities (p < 0.05). However, the total colour change was maximum at the highest power intensity. For the investigated infrared drying conditions, 1970 W/m² was recommended as the best-infrared power intensity applied for drying of dill leaves by taking into account both performance analyses and quality changes.

Optimization and kinetics modeling of okara isoflavones extraction using subcritical water

In this study, the soybean milk and tofu byproduct okara was subjected to subcritical water extraction with the intention of recovering isoflavones with minimal degradation. Response Surface Methodology (RSM) of the extraction variables indicated that optimized conditions would be T = 146.23 °C, P = 3.98 MPa, and α = 20 mg (solid)/mL (extractant). Mathematical models for the conversion and degradation of isoflavones were solved as a set of simultaneous equations leading to rate constants and time-dependent concentration profiles for each genistein- and daidzein-based compound. These kinetic analyses suggested that an optimum extraction time, under RSM-optimized conditions, would be 213.5 ± 8.7 min. The results of our study suggest that okara byproducts could be valorized efficiently, as a source of bioactive isoflavone aglycones, using subcritical water. The mathematical models and optimized extraction conditions that we established in this study could be employed, as process control-optimized variables, in the exploitation of okara, specifically in the isolation of genistein and daidzein.

Changes in Phenolic Acid and Isoflavone Contents during Soybean Drying and Storage

The changes in phenolic acid and isoflavone profile of soybean genotypes ( Nidera 5909 RR and BMX Força RR) dried at different temperatures and stored for 12 months were investigated. In both cultivars, there was a reduction of the germination capacity and an increase of fungal incidence with the increase of drying temperature and storage time. Multivariate analysis of phenolic acids allowed for the differentiation among treatments. Cultivar Nidera 5909 RR, dried at 110 °C, showed an interaction with characters of greater relevance for differentiation, being influenced by the increase of bound coumaric, and syringic, and free-hydroxybenzoic, syringic, and coumaric acids. Multivariate analysis of isoflavones showed a strong affinity of the aglycone isoflavones (genistein, glycitein, and daidzein) within the Nidera 5909 RR cultivar at all drying temperatures and with BMX Força RR cultivar at the highest temperatures. These results indicate that the release and interconversion of isoflavone malonyl-β-glucosides and β-glucosides into aglycone forms are simultaneous reactions during storage.

High-power ultrasound as pre-treatment in different stages of soymilk manufacturing process to increase the isoflavone content

Ultrasound (US) was applied as a pre-treatment in hydrated soybeans (HSB) and soybean slurry (SBS) during soymilk elaboration process to evaluate the feasibility of increasing the isoflavone content (IC) in the resultant soymilk. A predictive model and optimum US processing conditions were obtained by response surface methodology (RSM) using a three-level-three-factor Box-Behnken statistical design (BBD) in which US amplitude (50, 75, and 100%), temperature (30, 45, and 60 °C), and time (20, 40, and 60 min) were selected as independent variables. Most of the US treatments applied in the HSB or SBS caused a significant increase (3-62%) in the total IC of the obtained soymilks over the control soymilk (6.97 mg/100 mL). However, the IC of the resultant soymilks from sonicated HSB (11.38 mg/100 mL) was significantly higher than that in soymilk prepared from US-treated SBS (8.66 mg/100 mL). Experimental data were fitted into a 2nd-order-polynomial model and processing parameters were optimized (100% amplitude, 30 °C, 20 min) to get the highest predicted and experimental IC, 11.38 and 12.8 mg/100 mL, respectively. These results indicated that US is a potential technology that could be implemented during soymilk manufacturing processing as pre-treatment of HSB to obtain soymilk with high isoflavone content and consequently better functionality.

Drying Characteristics of Soybean (Glycine Max) Using Continuous Drying and Intermittent Drying

The effects of drying temperature by continuous and intermittent drying on the drying characteristics of soybean were determined in this study. Among the thin-layer drying models, the Midilli–Kucuk model showed the best fit (R2> 0.99) to describe the drying of soybean. At 300 min of the effective drying time, the moisture content of continuous drying at 35, 40, and 45 ºC were 9.38 (±0.00), 8.69 (±0.17), and 7.70 % (±0.48), respectively; while the moisture content of intermittent drying at 35, 40, and 45 ºC were 8.28 (±0.21), 7.31 (±0.41), and 6.97 % (±0.07), respectively. The image analysis method for detection of the crack in soybean demonstrated that at the target moisture content (7.7 %), cracked grain ratios with intermittent drying at 35, 40, and 45 ºC were reduced by 52.08, 27.59, and 18.24 %, respectively. With the effective drying time, the activation energy for intermittent drying (9.33 kJ/mol) was significantly lower than that value for continuous drying (21.23 kJ/mol).

Effects of moisture and temperature during grain storage on the functional properties and isoflavone profile of soy protein concentrate

The objective of this study was evaluate the effects of moisture and temperature during grain storage on the functional properties and isoflavone profile of soy protein concentrate. The protein concentrate was extracted from soybeans on the first day of storage and after 12months of storage, at 12 and 15% moisture and at temperatures of 11, 18, 25, and 32°C. The protein concentrate obtained from grains stored at 32°C showed decreased extraction yield (51.6% with 15% of moisture) and protein solubility (24.8% with 15% of moisture) with increased emulsifying capacity (52.2% with 12% of moisture) and foam formation, compared with sample obtained at the start of the storage period. The isoflavone profile showed a decrease in the concentrations of glycosylated, malonyl, and acetyl isoflavones and a corresponding increase in the concentrations of aglycone isoflavones, with the magnitude of these changes increasing with increasing storage temperature and moisture content.

Submicrometric hypromellose acetate succinate particles as carrier for soy isoflavones extract with improved skin penetration performance

In this study, hypromellose acetate succinate (HPMCAS) stable submicronic particles loaded with a soy isoflavones extract have been obtained by nano spray drying technology. HPMCAS has been used as excipient able to increase both stability and supersaturation levels of the active ingredients hence able to enhance skin penetration performance of genistein and daidzein. The influence of polymer/extract ratio as other process variables, on particle size, morphology and permeation performance, have been investigated. Particles in submicronic range (mean size around 550nm) and narrow size distribution with high encapsulation efficiency (up to 86%) were obtained. HPMCAS was able to improve amorphization of genistein during the atomization process and avoid recrystallization during storage, even in harsh environmental condition. Moreover, the enhanced affinity of the optimized formulations with aqueous media, strongly increased isoflavones penetration through membrane with diffusive properties well-correlated to human skin, up to 10-fold higher than pure soy isoflavones extract raw material.

Drying Kinetics and Quality Attributes of Peach Cylinders as Affected by Osmotic Pretreatments and Infrared Radiation Drying

The effect of osmotic dehydration (OD) and ultrasound-assisted osmotic dehydration (ULOD) on drying kinetics and quality of peach cylinders by infrared radiation drying were investigated. The moisture state and redistribution after osmotic pretreatments and subsequent drying process were also studied by low field nuclear magnetic resonance. The water loss and solute gain increased with osmotic time, and ULOD could promote water transfer. The signal amplitude of free water and immobile water diminished and shifted to the left for samples pretreated by both ULOD and OD. The brightness in T2-weighted images appeared a declining trend with increasing osmotic time of ULOD and OD, indicating the moisture content reduced gradually. During dying process, the free water of all samples was removed completely after drying for 120 min. ULOD and OD could increase water activity and decrease shrinkage of samples. Long pretreatment of ULOD and OD improved the color of dried peach cylinders.