The effect of thermal treatment of whole soybean flour on the conversion of isoflavones and inactivation of trypsin inhibitors

Evaluation of antinutrients, nutritional, and functional properties in sacha inchi (Plukenetia volubilis L) cake treated with hydrothermal processes

Applying heat treatments using an autoclave and hot air sterilization can alter the proximal composition, technofunctional properties, and antinutrient content of Sacha inchi (P. volubilis) oil press cake. The autoclave and hot air treatments significantly reduced antinutrients compared to the control. The samples treated with autoclave and hot air sterilization exhibited a significant decrease in alkaloids, nitrates, tannins, saponins, and trypsin inhibitors compared to the control sample. However, the 20-min autoclave treatment did not significantly reduce the saponin antinutrients. Phytic acid significantly decreased in the 30-min hot air sample and autoclave 20-min/hot air treatments, respectively. On the other hand, the levels of antinutrients oxalate and thiocyanates did not significant difference between the control and hot air treatments. However, the autoclave treatment resulted in a significant reduction in oxalates. The study found that hydrotreatments at temperatures of 121 °C with humid heat - autoclave showed significant differences in protein content compared to the control sample, with content of 37.75 + 0.2 g/100g. Samples treated with an autoclave for 10, 20, and 30 min showed values of protein 53.19 + 0.28, 66.08 + 2.6, and 70.12 + 0.48 g/100g, respectively. Meanwhile, samples treated with dry heat showed significant differences with the sample treated for 10 min having a protein content of 60.21 + 6.80 g/100g. The techno-functional properties analyzed in the study demonstrated a significant decrease in hydrating properties such as water holding capacity (WHC), water retention capacity (WRC), and swelling capacity (SC) due to changes in the solubility of proteins for the two treatments and the oil holding capacity (OHC) property showed a significant increase. Finally, water's presence during hydrothermal treatments significantly reduces antinutrients, providing guidance for analyzing other study variables.

Effect of Germination on the Digestion of Legume Proteins

As one of the main sources of plant protein, it is important to improve the protein digestibility of legumes. Faced with population growth and increasing environmental pressures, it is essential to find a green approach. Germination meets this requirement, and in the process of natural growth, some enzymes are activated to make dynamic changes in the protein itself; at the same time, other substances (especially anti-nutrient factors) can also be degraded by enzymes or their properties (water solubility, etc.), thereby reducing the binding with protein, and finally improving the protein digestibility of beans under the combined influence of these factors The whole process is low-carbon, environmentally friendly and safe. Therefore, this paper summarizes this process to provide a reference for the subsequent development of soybean functional food, especially the germination of soybean functional food.

Recent innovations and emerging technological advances used to improve quality and process of plant-based milk analogs

The worldwide challenges related to food sustainability are presently more critical than ever before due to the severe consequences of climate change, outbreak of epidemics, and wars. Many consumers are shifting their dietary habits toward consuming more plant-based foods, such as plant milk analogs (PMA) for health, sustainability, and well-being reasons. The PMA market is anticipated to reach US$38 billion within 2024, making them the largest segment in plant-based foods. Nevertheless, using plant matrices to produce PMA has numerous limitations, including, among others, low stability and short shelf life. This review addresses the main obstacles facing quality and safety of PMA formula. Moreover, this literature overview discusses the emerging approaches, e.g., pulsed electric field (PEF), cold atmospheric plasma (CAP), ultrasound (US), ultra-high-pressure homogenization (UHPH), ultraviolet C (UVC) irradiation, ozone (O3), and hurdle technology used in PMA formulations to overcome their common challenges. These emerging technologies have a vast potential at the lab scale to improve physicochemical characteristics, increase stability and extend the shelf-life, decrease food additives, increase nutritional and organoleptic qualities of the end product. Although the PMA fabrication on a large scale using these technologies can be expected in the near future to formulate novel food products that can offer green alternatives to conventional dairy products, further development is still needed for wider commercial applications.

Ultrasound-enhanced interfacial adsorption and inactivation of soy trypsin inhibitors

In this study, liquid-liquid interfacial protein adsorption was proposed as a means of inactivating soy trypsin inhibitors (TIs, including Kunitz (KTI) and Bowman-Birk inhibitor (BBI)). Hexane-water was first selected as a model system to compare three emulsification methods (hand shaking, rotor-stator and ultrasound mixing). Ultrasound could generate the smallest and least polydisperse emulsion droplets, resulting in highest interfacial adsorption amount of KTI and BBI as well as the highest inactivation percentage of TIs (p < 0.05). Therefore, ultrasound was selected to further explore the effect of the non-aqueous phase on interfacial adsorption and inactivation kinetics of TIs in a food emulsion system containing vegetable oil (VTO). The adsorption amounts of KTI and BBI in the VTO-aqueous emulsion increased by ∼ 25 % compared to the hexane-aqueous emulsion. In addition, the adsorption amounts of KTI and BBI were rapidly increased as a function of sonication time, especially for the hexane-aqueous emulsion system. This result suggests that such inactivation of TIs could be implemented in continuous systems for large-scale processing. Finally, the pathways of interface-induced inactivation of BBI and KTI were investigated based on separate experiments on individual BBI and KTI systems. The results showed that the interface adsorption caused the changes in the secondary and tertiary structure of KTI that led to its activitation. However, BBI was quite stable at the liquid-liquid interface without significant conformational change. Overall, ultrasound-assisted interfacial adsorption can be considered a rapid and highly efficient method to inactivate KTI.

Plant-based milk: unravel the changes of the antioxidant index during processing and storage - a review

As a nutrient rich emulsion extracted from plant materials, plant-based milk (PBM) has been the latest trend and hot topic in the food industry due to the growing awareness of consumers toward plant-based products in managing the environmental (carbon footprint and land utility), ethical (animal well-fare) and societal (health-conscious) issues. There have been extensive studies and reviews done to discuss the distinct perspective of PBM including its production, health effects and market acceptance. However, not much has been emphasized on the valuable antioxidants present in PBM which is one of the attributes making them stand apart from dairy milk. The amounts of antioxidants in PBM are important. They offered tremendous health benefits in maintaining optimum health and reducing the risk of various health disorders. Therefore, enhancing the extraction of antioxidants and preserving their activity during production and storage is important. However, there is a lack of a comprehensive review of how these antioxidants changes in response to different processing steps involved in PBM production. Presumably, antioxidants in PBM could be potentially lost due to thermal degradation, oxidation or leaching into processing water. Hence, this paper aims to fill the gaps by addressing an extensive review of how different production steps (germination, roasting, soaking, blanching, grinding and filtration, and microbial inactivation) affect the antioxidant content in PBM. In addition, the effect of different microbial inactivation treatments (thermal or non-thermal processing) on the alteration of antioxidant in PBM was also highlighted. This paper can provide useful insight for the industry that aims in selecting suitable processing steps to produce PBM products that carry with them a health declaration.

Long-term exposure to genistein inhibits the proliferation of gallbladder cancer by downregulating the MCM complex

Soy isoflavones are natural tyrosine kinase inhibitors closely associated with decreased morbidity and mortality of various tumors. The activation of tyrosine kinases such as ERBB2 is the mechanism by which cholecystitis transforms into gallbladder cancer (GBC), therefore, it is important to investigate the relationship between long-term exposure to soy isoflavones and the occurrence and progression of GBC. This case-control study (n = 85 pairs) found that the high level of plasma soy isoflavone-genistein (GEN) was associated with a lower risk of gallbladder cancer (≥326.00 ng/mL compared to ≤19.30 ng/mL, crude odds ratio 0.15, 95% CI 0.04-0.59; P for trend = 0.016), and that the level of GEN exposure negatively correlated with Ki67 expression in GBC tissue (n = 85). Consistent with these results, the proliferation of GBC cells was inhibited in the long-term exposure models of GEN in vitro and in vivo. The long-term exposure to GEN reduced the tyrosine kinase activity of ERBB2 and impaired the function of the PTK6-AKT-GSK3β axis, leading to downregulation of the MCM complex in GBC cells. In summary, long-term exposure to GEN associated with soy products intake might play a certain role in preventing GBC and even inhibiting the proliferation of GBC cells.

Impact of Pulsed Electric Field Pre-Treatment on the Isoflavone Profile of Soymilk

In this study, pulsed electric fields (PEFs) were evaluated as extraction-aiding technology during soymilk manufacturing to improve its isoflavone profile. Low-intensity PEFs were applied at different processing conditions in two stages of the soymilk extraction process, hydrated soybeans (HSB) and soybean slurry (SBS), with the soymilk extracted from the conventional process as control (CSM). Overall, resultant soymilk samples from PEF-HSB and PEF-SBS presented lower concentrations of glucosides isoflavones and greater aglycone content than those in CSM. In contrast to genistin (Gin) and daidzin (Din), which decreased around 18.5–52.6% and 10.9–54.6%, respectively, an increase in genistein (Ge, 12.3–64.4%) and daidzein (Da, 9–55.8%) was observed. The total isoflavone content (TIC) of most soymilk samples prepared from PEF-HSB was lower than that of the CSM. Conversely, when PEF-SBS was used, the TIC of resultant soymilk was not significantly affected or slightly decreased. However, PEF treated HSB at 10 kVcm−1/100 pulses and SBS at 6 kVcm−1/10 pulses led to a significant augment in TIC, of up to 109 ± 2.39 and 110 ± 1.26 μg/g, respectively, in the extracted soymilk samples. These results indicated that low-intensity PEF is a potential technology that could be implemented during soymilk manufacturing processing to modify the isoflavone profile and content of soymilk, mainly increasing its aglycone concentration.

Isoflavone Changes in Immature and Mature Soybeans by Thermal Processing

The isoflavone changes occurring in mature soybeans during food processing have been well studied, but less information is available on the changes in immature soybeans during thermal processing. This study aimed to determine the effect of thermal processing by dry- or wet-heating on the changes in the isoflavone profiles of immature and mature soybeans. In the malonylglycoside forms of isoflavone, their deglycosylation was more severe after wet-heating than after dry-heating regardless of the soybean maturity. The malonyl forms of isoflavones in the immature seeds were drastically degraded after a short wet-heating process. In the acetylglycoside forms of isoflavone, dry-heating produced relatively low amounts of the acetyl types in the immature soybeans compared with those in the mature soybeans. These results were explained by the content of acetyldaidzin being relatively less changed after dry-heating immature soybeans but increasing four to five times in the mature soybeans. More of the other types of acetylglycoside were produced by dry-heating soybeans regardless of their maturity. Acetylgenistin in wet-heating was a key molecule because its content was unchanged in the immature soybeans during processing but increased in the mature soybeans. This determined the total acetylglycoside content after wet-heating. In contrast, most of the acetyl forms of isoflavone were produced after 90 to 120 min of dry-heating regardless of the seed maturity. It can be suggested that the pattern of isoflavone conversion was significantly affected by the innate water content of the seeds, with a lower water content in the mature soybeans leading to the greater production of acetyl isoflavones regardless of the processing method even if only applied for a relatively short time. The results suggested that the isoflavone conversion in the immature soybeans mainly follows the wet-heating process and can be promoted in the application of stronger processing.

Targeted inactivation of soybean proteinase inhibitors using zinc

In this study the potential targeted use of zinc to inactivate proteinase inhibitors (PI) has been investigated as an alternative to the widely applied heat treatment used industrially for inactivation of PI. Zinc was utilized for the reduction of disulfide bonds leading to the structural changes in proteins, thus affecting the decreased affinity between PI and proteinases. The protein disulfide bond reduction mechanism was studied using a newly developed micellar electrokinetic capillary chromatography (MECC) with the glutathione redox reaction with dithiothreitol (DTT) as model system. This model proved efficient in monitoring the reduction of disulfide bonds in the Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI). The use of zinc as a reductant resulted in a significant reduction of trypsin inhibitor activity (TIA) of 72% for KTI and 85% for BBI, highlighting zinc as a promising potential agent to reduce the activity of PI as an alternative to heat treatment.

Isolation of individual isoflavone species from soybean by solvent extraction followed by the combination of macroporous resin and aluminium oxide separation

Growing interest in the health benefits of soy isoflavones has led to research in the isolation of individual isoflavone species for further application. Herein, we develop a new strategy to isolate daidzein, genistein, daidzin and genistin in soybean. We investigated the impact of solvents used and the extraction time on the extracted isoflavone contents from soybean. A 30-min extraction with 65% aqueous methanol gave a total isoflavone yield of 345 mg/100 g soybean, the highest value among tested conditions. Further, we proposed a two-stage adsorption/desorption chromatography comprising macroporous resin and aluminium oxide to isolate isoflavone. First, HP-20 resin was used to separate the glucosidic and aglyconic forms of isoflavone, then individual species of isoflavone could be isolated using aluminium oxide by specific retention of 5-hydroxy isoflavone. This process achieved overall high recovery (82-97%) and purity (92-95%) of the four isoflavones, which confirms a high separating efficiency for isoflavones from soybean.

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.

Acetic Acid Fermentation of Soybean Molasses and Characterisation of the Produced Vinegar

Soybean molasses is a by-product from the production of protein concentrate from soybean meal that predominantly contains sugars, with sucrose as the major component. In Brazil, soybean molasses is used for animal feed or it is discarded, although some industries use it to produce ethanol. This study aims to evaluate the parameters required for the acetic acid fermentation of soybean molasses, and characterise the resultant vinegar. To study the most suitable parameters for the acetic acid fermentation, vinegar was produced from the alcohol fermentation of soybean molasses through eight fermentation cycles: five for adaptation and three for production. The average acidity of the acetic acid fermentation product was 50.60 g/L, with an acetic acid fermentation yield, total yield of acetic acid in broth and productivity 65.01%, 92.76% and 0.033 g/(L·h), respectively. The vinegar produced from soybean molasses has an acidity of 5.07% (m/V), residual ethanol content 0.17% (m/V), sugars 7.86% (m/V), dry extract 14.67% (m/V), ash 2.27% (m/V) and a density of 1.023 g/cm³. The contents of total phenolics and isoflavones decreased after the alcohol and acetic acid fermentations. Moreover, the isoflavones profile of the fermented product comprised only three forms: daidzein, glycitin and genistin. According to our results, 3460 L of vinegar can be produced for every tonne of soy molasses, with an acetic acid concentration of 40 g/L, the minimum required by the legislation on vinegar production. Thus, these findings demonstrate that soy molasses represents a useful raw material for the production of vinegar.

The bio-processing of soybean dregs by solid state fermentation using a poly γ-glutamic acid producing strain and its effect as feed additive

Soybean dregs are restricted as feed additives because they contain anti-nutrient factors. Herein, soybean dreg was bio-transformed by solid-state fermentation (SSF) using a poly γ-glutamic acid (γ-PGA) producing stain Bacillus amyloliquefaciens NX-2S. The maximum γ-PGA production of 65.79 g/kg was reached in a 5 L fermentation system while the conditions are 70% initial moisture of soybean dregs with addition of molasses meal, 12% inoculum size, 30 °C fermentation temperature, initial pH of 8, and 60 h fermentation time. Meanwhile, continuous batch fermentation was proved feasible. After SSF, the anti-nutritional factors such as trypsin inhibitor, phytic acid and tannin were reduced by 98.7%, 97.8%, and 63.2%, respectively. Compared with unfermented soybean dregs, adding fermented soybean dregs to feed increased the average weight gain of rats by 15.6% and reduced the ratio of feed to meat by 11.3%. Therefore, this study provided a feasible strategy for processing soybean dregs as feed additive.

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.

Micellar systems of aliphatic alcohol ethoxylates as a sustainable alternative to extract soybean isoflavones

Ethoxylated aliphatic surfactants belonging to the Genapol and Tergitol series were assessed as extraction systems of isoflavones. They showed good extraction properties when compared with different solvents, the Genapol X-080 exhibiting the best performance. Available commercial isoflavone pills were used, as a starting simple matrix, to determine the parameters that affect the extraction procedure. The temperature and the surfactant concentration showed to be factors that favored significantly the extraction performance. The application of optimized variables (Genapol X-080 11% m/m, pH 4.5; extraction temperature of 54 °C and extraction time of 60 min) on soybean flour (natural) allowed extracting 3.237 ± 0.173 mg of isoflavone per gram of treated flour. This result was three times what it was for methanol under identical conditions. Extraction with these micellar systems represents a sustainable alternative methodology for industrial purposes due to its low cost, biodegradability, non-toxicity and easy scaling up.

Comparison of Conventional and Microwave Treatment on Soymilk for Inactivation of Trypsin Inhibitors and In Vitro Protein Digestibility

Soymilk is lower in calories compared to cow’s milk, since it is derived from a plant source (no cholesterol) and is an excellent source of protein. Despite the beneficial factors, soymilk is considered as one of the most controversial foods in the world. It contains serine protease inhibitors which lower its nutritional value and digestibility. Processing techniques for the elimination of trypsin inhibitors and lipoxygenase, which have shorter processing time and lower production costs are required for the large-scale manufacturing of soymilk. In this study, the suitable conditions of time and temperature are optimized during microwave processing to obtain soymilk with maximum digestibility with inactivation of trypsin inhibitors, in comparison to the conventional thermal treatment. The microwave processing conditions at a frequency of 2.45 GHz and temperatures of 70 °C, 85 °C and 100 °C for 2, 5 and 8 min were investigated and were compared to conventional thermal treatments at the same temperature for 10, 20 and 30 min. Response surface methodology is used to design and optimize the experimental conditions. Thermal processing was able to increase digestibility by 7% (microwave) and 11% (conventional) compared to control, while trypsin inhibitor activity reduced to 1% in microwave processing and 3% in conventional thermal treatment when compared to 10% in raw soybean.

Inactivation Methods of Trypsin Inhibitor in Legumes: A Review

Seed legumes have played a major role as a crop worldwide, being cultivated on about 12% to 15% of Earth's arable land; nevertheless, their use is limited by, among other things, the presence of several antinutritional factors (ANFs - naturally occurring metabolites that the plant produces to protect itself from pest attacks.) Trypsin inhibitors (TIs) are one of the most relevant ANFs because they reduce digestion and absorption of dietary proteins. Several methods have been developed in order to inactivate TIs, and of these, thermal treatments are the most commonly used. They cause loss of nutrients, affect functional properties, and require high amounts of energy. Given the above, new processes have emerged to improve the nutritional quality of legumes while trying to solve the problems caused by the use of thermal treatments. This review examines and discusses the methods developed by researchers to inactivate TI present in legumes and their effects over nutritional and functional properties.

Inactivation of soybean trypsin inhibitor by dielectric-barrier discharge (DBD) plasma

Soybean trypsin inhibitor (STI) is considered as one of the most important anti-nutritional factors in soybeans. The objective of this study was to investigate the impacts and underling mechanisms of dielectric-barrier discharge (DBD) plasma on STI activities. The results shown that DBD plasma treatment significantly induced the inactivation of STI in soymilk and Kunitz-type trypsin inhibitor from soybean (SKTI) in a model system. After exposure to DBD plasma at 51.4W for 21min, the STI activities of soymilk were reduced by 86.1%. Affter being treated by DBD plasma, the intrinsic fluorescence and surface hydrophobicity of SKTI were significantly decreased, while the sulfhydryl contents were increased. It is assumed that DBD plasma-induced conformational changes and oxidative modification might contribute to the inactivation of SKTI. In summary, DBD plasma technology is a potential alternative to heat treatment for the inactivation of anti-nutritional substances in food legumes.

Cooking Has Variable Effects on the Fermentability in the Large Intestine of the Fraction of Meats, Grain Legumes, and Insects That Is Resistant to Digestion in the Small Intestine in an in Vitro Model of the Pig's Gastrointestinal Tract

This study aimed to evaluate the fermentation in the large intestine of indigestible dietary protein sources from animal, insect, and plant origin using an in vitro model of the pig's gastrointestinal tract. Protein sources were used raw and after a cooking treatment. Results showed that the category of the ingredient (meats, insects, or grain legumes) exerts a stronger impact on enzymatic digestibility, fermentation patterns, and bacterial metabolites such as short-chain fatty acids (SCFA) and hydrogen sulfide (H₂S) than the cooking treatment. The digestibility and the fermentation characteristics of insects were more affected by the cooking procedure than the other categories. Per gram of consumed food, ingredients from animal origin, namely, meats and insects, were associated with fewer fermentation end-products (gas, H₂S, SCFA) than ingredients from plant origin, which is related to their higher small intestinal digestibility.

Determination of Isoflavones in Soybean Flour by Matrix Solid-Phase Dispersion Extraction and Liquid Chromatography with UV-Diode Array Detection

A new analytical method, based on liquid chromatography (LC) with UV-diode array detection, for the simultaneous determination of daidzein, genistein, and glycitein and their 7-O-β-D-glucopyranoside (daidzin, genistin, and glycitin, resp.) has been successfully developed. All the calibration curves showed good linearity within the concentration range 0.02–2 μg/ml. The limits of detection and quantitation were 0.057 (genistin and glycitein), 0.124 μg/ml (genistein), 0.190 μg/ml (genistin and glycitein), and 0.410 μg/ml (genistein), respectively. Within-day and between-days precision were found not to be significantly different according to an F-test; values (% RSD) ranged from 2.0 to 2.9%. Extraction and clean-up of soybean flour samples were carried out using matrix solid-phase dispersion extraction (MSPD). The main parameters affecting extraction yield, such as dispersant, type and amount of additives, cosorbent, and extractive solvent, were evaluated and optimized. The average recovery values were between 85.7 and 102.6%. The target isoflavone concentration levels estimated in this work fit existing literature data and were comprised between 39.3 and 345.3 μg/g. The whole procedure has proved to be simple, accurate, precise, and cheap.

Integrated extraction and purification of soy isoflavones by using aqueous micellar systems

In this work, an integration of solid-liquid and liquid-liquid extractions by using aqueous micellar two-phase systems was evaluated as potential tool to purify soy isoflavones. Additionally, the proposed methodology aimed to preserve the protein content of the processed soy flour. The extractive assays were performed in AMTPS formed by Triton X-114 and sodium tartrate. In order to optimize the purification process, temperature and time were evaluated as independent variables. Under optimal working conditions, i.e. 100min and 33°C of incubation, IF were purified with a recovery percentage of 93 and a purification factor of almost 10. More importantly, the obtained sample presented an aglycone proportion superior to the reported by other methodologies. These results open perspectives to the use of aqueous micellar two-phase systems as an integrative methodology to extract, concentrate and purify isoflavones.