Soy Milk Treatments Research Articles

Pulsed electric field treatment of soymilk: Impact on Kunitz trypsin inhibitor allergenicity, antinutritional factor, and aroma characteristics.

Allergens, antinutritional factors, and lipoxygenase (LOX) enzyme present in soymilk limit its consumption as vegan milk. Therefore, the present study focuses on reducing these limiting factors using pulsed electric field (PEF) treatment. In this regard, 20-40kV/cm electric field was applied to soymilk for the effective treatment periods of 450, 1350, and 2250ms. After the treatment, a reduction in pH (6.60±0.10 to 6.47±0.12) and an increase in the conductivity (173.03±0.40 to 177.33±0.72 µS) were observed. Furthermore, FTIR (Fourier Transform Infrared Spectroscopy), UV (Ultra Violet)intrinsic spectra, and CD (Circular Dichroism)spectra (α-helix reduction and β-sheet increase) data indicated mild structural changes in the proteins of soymilk. As a result, PEF treatment reduced the soymilk allergenicity (67.33±20.48%), LOX activity (69.45±9.38%), and trypsin inhibitor activity (75.61±4.04%). Apart from that, the color, viscosity, and volatiles of soymilk also had significant changes due to PEF treatment. The aroma changes in PEF-treated soymilk were highly influenced by two major principal component (PC1 & PC2) groups and they accounted for about 70% of the aroma variations. However, these changes were mild and did not induce any off-flavors and the treatment remained effective against the quality hazards like allergens, antinutritional factors, and LOX enzyme. PRACTICAL APPLICATION: PEF treatment of soymilk reduces the possible allergic reactions in human body at least by 30%. Further, it reduces the antinutritional factor and off-odor inducing compounds. Therefore, the PEF treatment can be used in industries as a pre-treatment to produce allergen and antinutritional compounds free protein isolates from soybeans.

Changes of hexanal content in fermented soymilk: Induced by lactic acid bacterial fermentation and thermal treatment

To study the causes of beany off-flavor regeneration after fermented soymilk was thermal treated. Hexanal was soymilk beany off-flavor and analyzed using headspace solid phase microextraction. The hexanal removal and regeneration during fermentation and heat treatment of soymilk and soy protein solutions were analyzed. Soymilk contained both free and protein-bound hexanal. Both 7 S and 11 S could bind to hexanal, and the amount of bound hexanal to 11 S was approximately five times that to 7 S. pH decreased to approximately 4.5 or enzymatic hydrolysis could effectively weaken the binding of hexanal to soy protein, but not capable of dissociating them. Further heat treatment was required for hexanal volatilized from protein. Lactic acid bacteria could completely remove free hexanal, but the removal ability of protein-bound hexanal was weak, which varied among bacterial species. The results will be valuable for improving flavor qualities of fermented soymilk and its beverage products. This result revealed the mechanism behind the fact that the off-flavor of heated fermented soymilk was difficult to be removed. Thus, the results will be valuable for improving flavor qualities of fermented soymilk and its beverage products. Practical applications This result revealed the mechanism behind the fact that the off-flavor of heated fermented soymilk was difficult to be removed. Thus, the results will be valuable for improving flavor qualities of fermented soymilk and its beverage products.

A statistical strategy for optimizing the production of α-galactosidase by a newly isolated Aspergillus niger NRC114 and assessing its efficacy in improving soymilk properties

Backgroundα-Galactosidase is widely distributed in plants, microorganisms, and animals, and it is produced by different fungal sources. Many studies have confirmed the valuable applications of α-galactosidase enzymes for various biotechnological purposes, like the processing of soymilk. ResultsAspergillus niger NRC114 was exploited to produce the extracellular α-galactosidase. One factor per time (OFT) and central composite design (CCD) approaches were applied to determine the optimum parameters and enhance the enzyme production. The CCD model choices of pH 4.73, 1.25% mannose, 0.959% meat extract, and 6-day incubation period have succeeded in obtaining 25.22 U/mL of enzyme compared to the 6.4 U/mL produced using OFT studies. Treatment of soymilk by α-galactosidase caused an increase in total phenols and flavonoids by 27.3% and 19.9%, respectively. Antioxidant measurements revealed a significant increase in the enzyme-treated soymilk. Through HPLC analysis, the appearance of sucrose, fructose, and glucose in the enzyme-treated soymilk was detected due to the degradation of stachyose and raffinose. The main volatile compounds in raw soymilk were acids (45.04%) and aldehydes (34.25%), which showed a remarkable decrease of 7.82% and 20.03% after treatment by α-galactosidase. ConclusionsTo increase α-galactosidase production, the OFT and CCD approaches were used, and CCD was found to be four times more effective than OFT. The produced enzyme proved potent enough to improve the properties of soymilk, avoiding flatulence and undesirable tastes and odors. Graphical Abstract▪

Protein aggregation and Ca2+-induced gelation of soymilk after heat treatment under slightly alkaline conditions

Alkaline heat treatment of soymilk is widely used in the production of soy products. This study aimed to clarify the effect of the thermal aggregation state of proteins on the coagulation characteristics of soymilk. Soymilk with different pH levels (6.6–8.0) was preheated, and the gelation processes induced by CaSO4·2H2O and the gel properties were investigated. Results showed that the aggregation and binding pattern of proteins changed after slightly alkaline heat treatment. The ability of 7S and the acidic (A) subunit of 11S to bind to the basic (B) subunit of 11S weakened. These subunits converted into non-particulate proteins, which decreased particulate protein content and particle size. The number of sulfhydryl groups on the protein surface reduced by 45%–62%, and more disulfide bonds formed in the protein subunits during recombination. During gelation, the soymilk after alkaline heat treatment exhibited a slow intermolecular binding in the “pre-aggregation” stage, which led to late gelation onset and a uniform gel network. With the increase in non-gelable protein content in the gel, the water holding capacity (WHC) enhanced and but the hardness decreased. When the pH was further increased (pH ≥ 7.8) to the isoelectric point of the B subunit, the B subunit excessively aggregated and formed large and dense aggregates, which increased gel hardness and produced a rough and uneven network.

Effect of high-intensity ultrasound soymilk pretreatment on the physicochemical properties of microbial transglutaminase-catalyzed tofu gel.

Tofu prepared by conventional methods often has a bitter taste and poor water-holding capacity (WHC). To improve the quality of the product, alternative processes must be developed. Herein, the effect of ultrasound pretreatment on the properties of soymilk and tofu gel derived thereof were investigated. Treatment of soymilk with ultrasound gave rise to a reduction in the particle size and an enhancement in the surface hydrophobicity, whereby optimum values were obtained after 15min treatment. Subsequently, microbial transglutaminase (MTG) was added to ultrasound-treated soymilk to promote the soy protein crosslinking. The gel strength, WHC, and nonfreezable water content of MTG-catalyzed tofu gel obtained from treated soymilk increased with the extension of the ultrasound pretreatment time, whereas the free sulfhydryl content decreased because of the formation of disulfide bonds. Fourier transform infrared spectroscopy demonstrated variations in the secondary structure of MTG-catalyzed tofu gel. Furthermore, soymilk's exposure to high-intensity ultrasound pretreatment led to a tofu gel with a dense, homogenous, and stable network structure, as evidenced by scanning electron microscopy. Therefore, this study answers for the theoretical support of the industrial production of MTG-catalyzed tofu gel from ultrasound-treated soymilk. PRACTICAL APPLICATION: High-intensity ultrasound pretreatment improved the texture properties of MTG-catalyzed tofu gel. The resulting MTG-catalyzed tofu gel has potential application in industrial production.

Identification of an Invertase With High Specific Activity for Raffinose Hydrolysis and Its Application in Soymilk Treatment.

The hydrolyzation of raffinose into melibiose by using invertases under mild conditions improves the nutritional value of soybean products. However, this strategy has received little attention because a suitable invertase remains lacking. In this study, a novel invertase named InvDz13 was screened and purified from Microbacterium trichothecenolyticum and characterized. InvDz13 was one of the invertases with the highest specific activity toward raffinose. Specifically, it had a specific activity of 229 U/mg toward raffinose at pH 6.5 and 35°C. InvDz13 retained more than 80% of its maximum activity at pH 5.5–7.5 and 25–40°C and was resistant to or stimulated by most cations that presented in soymilk. In soymilk treated with InvDz13 under mild conditions, melibiose concentration increased from 3.1 ± 0.2 to 6.1 ± 0.1 mM due to raffinose hydrolyzation by InvDz13. Furthermore, the prebiotic property of InvDz13-treated soymilk was investigated via in vitro fermentation by human gut microbiota. Results showed that InvDz13 treatment increased the proportion of the beneficial bacteria Bifidobacterium and Lactobacillus by 1.6- and 3.7-fold, respectively. By contrast, the populations of Escherichia and Collinsella decreased by 1.8- and 11.7-fold, respectively. Thus, our results proved that the enzymatic hydrolysis of raffinose in soymilk with InvDz13 was practicable and might be an alternative approach to improving the nutritional value of soymilk.

Effect of ozone treatment on microbiological and physicochemical properties of soymilk beverage

Ozone is a strong oxidant and potent desinfecting agent. An ozonation process for microbial inactivation in some beverages has been done. Accordingly, the ozonation process was performed in soymilk. Soymilk was ozonated under different exposure time: 1, 3, 5, 10, and 15 minutes and evaluated for the changes of microbiological and physicochemical properties. The assays were carried out by using an experimental design fully randomized and results were statistically evaluated by Duncan’s Multiple Range test (p < 0.05). Following the ozone treatment, a significant reduction in pH occurred at 1 minute treatment, whereas a significant increasement was recorded after 3 minutes treatment. A significant increasement in total dissolve solid was observed at 5, 10, and 15 minutes. Microbial reduction was recorded 0.19 log cycles at 1 min., 0.35 log cycles at 3 min, and 0.57 log cycles at 5 minutes ozone treatment. In contrast, an increase of microbial population occurred at 10 and 15 minutes. The findings presented here could be a prelude for the potential application of ozone treatment of soymilk in the food industry.

Effect of selective thermal denaturation and glycosylation on the textural properties and microstructure of vegetable tofu

AbstractThe impact of selective thermal denaturation and glycosylation on the textural properties and microstructure of vegetable tofu made from carrot and seaweed was investigated. Thermal denaturation treatment (80 °C for 5 min) could significantly enhance the hardness and gumminess of carrot–seaweed tofu (p &lt; .05) and made its network structure more homogeneous and denser. Moreover, glycosylation treatment (1% glucose, 100 °C for 10 min) could remarkably improve the textural properties and network structure of carrot–seaweed tofu. Therefore, the thermal denaturation and glycosylation treatment of soymilk could be an effective way to improve the texture and microscopic structure of carrot–seaweed tofu.Practical applicationsTofu is a soybean protein gel with rich nutrition and can complement protein, vitamins, and minerals needed by human body. Vegetable tofu made from carrot and seaweed is a novelty tofu product with the beautiful color, rich nutrition value, and moderate taste, possessing better market application prospect. In addition, selective thermal denaturation and glycosylation can effectively improve the texture and microstructure of carrot–seaweed tofu. Accordingly, selective thermal denaturation and glycosylation can cater to consumer demand for tofu nutrition and diversity, besides producing the better quality carrot–seaweed tofu.

Exploratory analysis of the human breast DNA methylation profile upon soymilk exposure

Upon soy consumption, isoflavone metabolites attain bioactive concentrations in breast tissue possibly affecting health. Though in vitro epigenetic activity of soy metabolites has been described, the in vivo impact on the epigenome is largely unknown. Therefore, in this case-control study, the breast glandular tissue DNA methylome was explored in women undergoing an aesthetic breast reduction. After a run-in phase, 10 generally healthy Belgian or Dutch women received soymilk for 5 days. MethylCap-seq methylation profiles were compared with those of 10 matched controls. Isoflavones and their microbial metabolites were quantified in urine, serum, and glandular breast tissue (liquid chromatography-mass spectrometry) and 17β-estradiol in glandular breast tissue (immunoassay). Global DNA methylation levels were obtained for 6 cases and 5 controls using liquid chromatography-mass spectrometry. Although lower MethylCap-seq coverages were observed, mass spectrometry results and computational LINE-1 methylation analysis did not provide evidence supporting global methylation alterations upon treatment. At a false discovery rate of 0.05, no differentially methylated loci were identified. Moreover, a set of previously identified loci was specifically tested, but earlier reported results could not be validated. In conclusion, after a 5-day soymilk treatment, no major general epigenetic reprogramming in breast tissue could be found in this exploratory study.

Binding of phytate to soybean protein during the heat treatment of soymilk and its effect on protein aggregation

To investigate the interactions between phytates and soybean proteins during heat treatment, as well as their effects on the heat-induced protein aggregation and the formation of soymilk protein particles, the amount of free phytate, calcium, and magnesium in both unheated and heated soymilk were measured by equilibrium dialysis. It was found that about one-third of the free phytate became attached to proteins and was transferred to the particulate protein fraction after heat treatment. By heating purified soy protein solutions, it was shown that the soy glycinin had considerably higher phytate-binding capacity than β-conglycinin and that the binding reaction only occurred when the glycinin was denatured by being either heated to a temperature higher than 75 °C or treated with urea and SDS. It was assumed that when soymilk was heated to high temperatures, there was a critical “opening period” when the compact structure of glycinin unfolded and dissociated into the basic and acidic polypeptides, with plenty of the inner basic amino acids exposed to the surface, which attracted phytate and other denatured negatively charged protein fractions. The competitive binding of phytate with the basic polypeptides inhibited the binding of α/α’ subunits and acidic polypeptides to some extent, resulting in a smaller ratio of particulate proteins. Phytate enhanced the solubility and inhibited the thermal aggregation of glycinin by increasing the negative charges on the protein surface.

Immobilization of an alpha-galactosidase from Debaryomyces hansenni UFV-1 in cellulose film and its application in oligosaccharides hydrolysis

Debaryomyces hansenii UFV-1 α-galactosidase was partially purified and immobilized in a cellulose film. The immobilization preserved 97% of the initial enzyme activity. The optimal pH levels of free and immobilized α-galactosidases were 5.0 and 4.0, respectively, and the optimal temperatures were 60 and 85°C, respectively. The immobilized α-galactosidase exhibited higher stability at 85°C for a period of 40h. The α-galactosidase maintained above 80% of its original activity even after ten consecutive reuse of the film. The storage of the film at room temperature preserved the enzyme activity. The soymilk treatment with immobilized enzyme for 16 and 20h, at 60°C, with or without agitation, respectively, reduced stachyose and raffinose contents completely.

The protective effects of probiotic-fermented soymilk on high-fat diet-induced hyperlipidemia and liver injury

The effects of probiotic-fermented soymilk (fermented by mixture of Bifidobacterium bifidum, Lactobacillus casei, and L. plantarum) on high-fat diet (HFD)-induced hyperlipidemia and liver injury were examined. C57BL/6N mice were randomly assigned into four groups that were treated with different diets: normal chow (NC), HFD, HFD with probiotic-fermented soymilk and HFD with non-fermented soymilk. After treatment for 6weeks, probiotic-fermented soymilk treatment significantly reduced HFD-induced body weight gain, hyperlipidemia, liver fat accumulation and reactive oxygen species (ROS) production. In addition, probiotic-fermented soymilk consumption significantly reduced the levels of serum alanine aminotransferase (ALT), lipopolysaccharide (LPS), and liver tumor necrosis factor-α (TNF-α) compared with the HFD treatment. Further, probiotic-fermented soymilk significantly increased the serum leptin level. In conclusion, probiotic-fermented soymilk reduced hyperlipidemia and liver injury induced by HFD. The role of probiotic-fermented soymilk may decrease the production of liver LPS, TNF-α, and oxidative stress and induce adipose leptin and triacylglycerol hydrolase (TGH) production.

Hypolipidaemic and renoprotective effects of Glycine max (Soy bean) against lipid profile and renal biochemical alterations in hypercholesterolemic rat

Background : Hyperlipidemia can be defined as concentration of lipids in the blood of a fasted (>12hrs) patient that exceeds the upper range of normal for that species. Studies have showed that rats with hypercholesterolemia are prompt to the development of cardiovascular diseases (CVD). Methods: Twenty-four (24) male albino Wister rats were used in this study. The rats weighed between 180-190g and were randomly divided into four (4) groups (A-D) with six (6) rats per group. For hypercholesterolemia induction, rats in group B, C and D were administered with HCD (2000mg/kg) once daily in the presence of carbimazole (1.35mg/kg) for 14days. Group B (test group) were treated with soymilk (2000mg/kg) and group C (positive control) with atorvastatin (20mg/kg) for 14 days. Group A (normal control) received water and vital feed only. At the end, fasting blood specimens were collected from all the animals in all the groups for estimation of lipid profile and renal biochemical parameters. The biochemical parameters of lipid profile: Total Cholesterol (TC), High density lipoprotein (HDL), Low density lipoprotein (LDL), Very low density lipoprotein (VLDL) and Triglycerides (TG) were assayed. Results : Results showed that the test group (soymilk) showed a non-significant decrease in TC, TG, LDL, VLDL and a non-significant increase in HDL concentrations but not as much as group C (Atorvastatin) which showed a significant decrease in TC and LDL (p<0.01), TG (p<0.05), VLDL and also a significant increase in HDL concentrations (p<0.05) when compared to the negative control group (HCD alone).Renal injury was assessed by measuring serum Na + , K + , Cl - , HCO 3 - , creatinine and urea levels. The HCD treatment resulted in marked elevation of: K + (8.670.77mmol/l); creatinine (2.070.23mg/dl); and urea (89.0014.42mg/dl) and caused deranged renal functions which were significantly improved by soymilk treatment: K + (6.510.34mmol/l); creatinine (1.030.24mg/dl); and urea (46.676.89mg/dl) with [P<0.05 or p<0.01]. Conclusion: Arguably, the phytochemicals in soy prevented dyslipidaemia and protected the kidney against the oxidative stress and the resultant renal dysfunction produced by hypercholesterolemia.

Nitrogen, cobalt-codoped carbon electrocatalyst for oxygen reduction reaction using soy milk and cobalt salts as precursors

Nitrogen and cobalt codoped carbon electrocatalyst using soy milk and cobalt salts as precursors has been examined for its electrocatalytic activity toward oxygen reduction reaction (ORR). Carbon dots (C-d) were first synthesized via hydrothermal treatment of soy milk. Then, cobalt (II) nitrate was incorporated with C-d via heat treatment to generate nitrogen and cobalt codoped carbon composites (Co/C). When polypyrrole was introduced in the synthetic process, carbon composites with higher nitrogen and cobalt contents (Co/N/C) than Co/C were obtained, which exhibited high electrocatalytic activity, excellent methanol crossover effect, and good stability toward ORR in alkaline solutions.

Effect of Enzymatic Protein Deamidation on Protein Solubility and Flavor Binding Properties of Soymilk

The effect of enzymatic deamidation by protein-glutaminase (PG) on protein solubility and flavor binding potential of soymilk was studied. Treatment of soymilk with PG for 2 h (temperature of 44 °C and enzyme:substrate ratio (E/S) of 40 U/g protein) resulted in high degree of protein deamidation (66.4% DD) and relatively low degree of protein hydrolysis (4.25% DH). Deamidated (DSM) and control soymilks (CSM) did not differ with respect to aroma, but differed in taste characteristics by sensory evaluation. Protein solubility in DSM was enhanced at weakly acidic conditions (pH 5.0), but did not differ from non-deamidated soymilk at pH values of 3.0 and 7.0. Odor detection thresholds for the flavor compounds vanillin and maltol were approximately 5 and 3 fold lower, respectively, in DSM than in CSM. Dose-response curves (Fechner's law plots and n exponents from Stevens's power law) further demonstrated that DSM had a lower flavor binding potential than CSM. PG deamidation has the potential to reduce flavor binding problems encountered in high protein-containing foods and beverages. The findings of this study can help lead to the development of technology to produce protein-containing foods with improved functional properties, especially protein solubility, and potentially decreased flavor fade problems associated with flavor-protein interactions, especially with carbonyl containing flavor compounds.

UV-C treatment of soymilk in coiled tube UV reactors for inactivation of Escherichia coli W1485 and Bacillus cereus endospores

Coiled tube UV reactors were used to investigate the influence of tube diameter (1.6mm ID, and 3.2mm ID) and Reynolds number (Re) to inactivate Escherichia coli W1485 and Bacillus cereus spores in raw soymilk (RSM). Four levels of Re (343, 686, 1029 and 1372) were tested in RSM inoculated separately with each bacterium and treated in the UV reactors at a constant residence time of 11.3s with UV-C dose of 11.187mJ/cm2 at 253.7nm. Inactivation efficiency of both microorganisms increased with Re. Maximum reductions of 5.6log10CFU/ml of E. coli and 3.29log10CFU/ml of B. cereus spores were achieved in the 1.6mm ID UV reactor. Inactivation efficiency was higher in the 1.6mm ID UV reactor than the 3.2mm ID UV reactor for both the organisms. Effect of UV-C light on lipid oxidation of untreated RSM, measured as malondialdehyde and other reactive substances (MORS) content, was much higher (95nmol/ml) than the UV-treated (58nmol/ml) and thermally pasteurized (55nmol/ml) RSM during the storage period of 7 days. The UV-C treatment can be effectively used for reducing E. coli cells and B. cereus spores in soymilk without compromising its quality.

Treatment of soy milk with Debaryomyces hansenii cells immobilised in alginate

Whole cells of Debaryomyces hansenii UFV-1 were permeabilised with ethanol and immobilised in calcium alginate hydrogel. The optimum pH and temperature for α-galactosidase activities of permeabilised free (PFC) and permeabilised immobilised cells (PIC) were 4.5 and 60 °C; and 4.0 and 70 °C, respectively. PIC α-galactosidase was more stable than that of PFC. The incubation of PIC at 60 and 70 °C promoted an increase in α-galactosidase activity. The α-galactosidase activity was maintained when PIC was used in three repeated batches. The K m values for PIC and PFC α-galactosidases, with ρNPαGal, were 0.82 mM and 0.30 mM, respectively. Soy milk treatment with PIC for 6 h at 60 °C promoted 100% hydrolysis of raffinose oligosaccharides.

Comparison of folate losses in soybean during the preparation of tempeh and soymilk

AbstractThe changes in undeconjugated and total folate content of soybean during various stages of tempeh and soymilk preparation were studied. Total folate was extracted by the tri‐enzyme technique. The ratio of total folate to undeconjugated folate was compared in all samples. Raw soybeans used for tempeh and soymilk preparation contained 4.04 and 4.50 mg total folate kg−1 respectively. Soaking and boiling soybean caused a significant loss of folate during tempeh and soymilk preparation. Leaching was identified as the major cause of folate loss, as soaking and cooking waters were found to contain a large amount of folate. Rhizopus fermentation of boiled soybean caused an increase of 68 and 100% in undeconjugated and total folate contents respectively. Frying reduced the folate content of tempeh significantly. Milling of boiled soybean in soymilk preparation significantly reduced the undeconjugated folate content of blanched soybean but increased the total folate. UHT treatment of soymilk caused a loss of 9 and 14% of undeconjugated and total folates respectively. The total folate content of deep‐fried tempeh and soymilk was 2.35 and 2.76 mg kg−1 respectively. Analysed values are expressed on a dry weight basis.© 2002 Society of Chemical Industry

Heat Inactivation Kinetics of Trypsin Inhibitors During High Temperature‐Short Time Processing of Soymilk

ABSTRACTHeat treatment of soymilk was studied in the conventional batch boiling process and under High Temperature‐Short Time (HTST) conditions. Reduction in total trypsin inhibitor was assayed enzymatically, and individual inhibitors, the Kunitz and the Bowman‐Birk inhibitor, were assayed by ELISA technique. Standard first‐order reaction kinetics and thermodynamics were applicable for inactivation, and results indicated that the mechanism was not protein unfolding, because entropy changes were zero or negative. The two inhibitors were inactivated at the same rate around 137°C. Therefore, a simple first‐order kinetic model which gave a good, slightly conservative estimate of residual anti‐trypsin activity under HTST conditions could be established.

Simple and efficient procedure for removing the 34 kDa allergenic soybean protein, Gly m I, from defatted soy milk.

The 34 kDa protein in the salted-out fraction of soy milk is shown to be identical to the allergenic soybean protein, Gly m I, by N-terminal amino acid sequencing and immunoblotting, using the monoclonal antibody against Gly m I. Treatment of soy milk with 1 M Na2SO4, acidifying to pH 4.5 and centrifugation removed more than 90% of the 34 kDa protein with an overall yield of 70% of total soy protein.