Degradation of Sulfhydryl Groups in Soymilk by Lipoxygenases during Soybean Grinding

The process of degradation of sulfhydryl (SH) groups in soymilk was investigated by using Glycine max var. Suzuyutaka (wild type) and the following seven mutant lines lacking lipoxygenase(s): L-1-, L-2-, L-3-, L-1,-2-, L-2,-3-, L-1,-3-, and L-1,-2,-3-null. The soymilk prepared from the L-1,-2,-3-null line of all the mutants had the highest SH content. The content of SH groups was the lowest with the L-1,-3-null line of the three double-null lines and the highest with the L-2-null line of the three single-null lines. These results show that lipoxygenases strongly participated in the degradation of SH groups in soymilk and that the L-2 isozyme had the greatest SH-degrading capability. When these soybean samples were ground under low-temperature conditions and in a nitrogen (N₂) atmosphere to inhibit the degradation of SH groups caused by lipoxygenases, SH degradation of the L-2,-3- and L-1,-3-null lines was strongly inhibited at low temperature, while that of the L-1,-2-null line was strongly inhibited in the N₂ atmosphere. In view of the strong inhibition of SH degradation in an N₂ atmosphere with Suzuyutaka (wild type), which has three L-1,-2,-3 isozymes, these results suggest that not only the L-2 isozyme but also that the L-3 isozyme of the three in Suzuyutaka played an important role in SH degradation during soybean grinding.     

大豆豆乳和豆腐产量、品质及有关加工性状的遗传变异

采用全国各地的261个大豆品种为材料,研究豆乳和豆腐产量、品质及有关加工性状的遗传变异.结果表明豆乳和豆腐加工过程中每100g干籽粒平均生产干豆乳71.92g,生产干豆腐51.80g,损失豆渣干物质25.76g,损失乳清干物质20.12g.干豆乳蛋白质、脂肪和总糖的含量分别为51.85%、22.55%和18.42%,干豆腐蛋白质、脂肪和总糖的含量分别为46.22%、24.58%和19.36%.豆乳和豆腐产量、品质及有关加工性状在品种间的差异均达到极显著水平,变异系数都较大,从中筛选出一批优异种质.     

Rapid measurement of phytate in raw soymilk by mid-infrared spectroscopy

The phytate content in soymilk is known to affect tofu curdling. A rapid measurement of phytate from a water extract of soybean (raw soymilk) in an early stage of tofu processing was investigated using mid-infrared spectroscopy (IR) with an ATR accessory. IR absorption of phytate was observed from 1200 cm-1 to 900 cm-1, and saccharide and protein in the extract also had IR absorption in the same region. In order to separate phytate from other components, the phytate was precipitated completely by the addition of calcium under alkaline condition (pH 11.5). The precipitate was dissolved in citrate buffer (pH 6.0) and then used for IR measurement. The absorbance at 1070 cm-1 correlated well with the phytate content of the soymilk. The measurement of phytate in raw soymilk can be done rapidly by FT-IR measurement with an ATR accessory and gives reproducible values, which can be used for the measurement of phytate content in various soybeans for tofu making.     

Changes in soybean phytate content as a result of field growing conditions and influence on tofu texture

It is known that tofu quality tends to vary among soybeans even of the same variety. Cultivation environments can affect the contents of the soybeans. Twenty-seven soybean varieties were grown in a drained paddy field and an upland field, and then their protein and phytate contents were determined using the Fourier transfer infrared spectroscopy (FT-IR) method. The phytate contents of 12 varieties were higher in the drained paddy field than in the upland field. On the other hand, the environmental factor had little effect on the protein contents. In order to determine whether the difference in phytate content affected tofu texture, the hardness of the tofu made from phytate-added soymilk was measured. The tofu texture having more phytate became softer in the range of the common coagulant concentration. We concluded that the difference in the phytate content of the soybeans among the environmental conditions is a factor that causes fluctuation in tofu quality.     

Hydrolysis of Galacto-oligosaccharides in Soymilk by κ-carrageenan-entrapped α-galactosidase from Aspergillus Oryzae

Summary α-Galactosidase was immobilized in κ-carrageenan. The optimum pH of the soluble enzyme and immobilized enzyme was 4.8. The optimum temperature of the soluble enzyme was 50 °C and that of the immobilized enzyme was increased to 53 °C. The immobilized enzyme was used in batch, repeated batch, and in the continuous mode to degrade the raffinose family sugars present in soymilk. Two hours incubation with free and immobilized α-galactosidase resulted in 88 and 75% reduction in raffinose family oligosaccharides in soymilk respectively. In the repeated batch, 61% reduction was obtained in the fourth cycle. A fluidized bed reactor was designed to treat soymilk continuously. The performance of immobilized α-galactosidase was also tested in a fluidized bed reactor at different flow rates and 92% reduction of raffinose family oligosaccharides in soymilk was obtained at 25 ml h⁻¹ flow rate. The study revealed that immobilized α-galactosidase in continuous mode is efficient in reducing the oligosaccharides present in the soymilk.     

Immobilization of <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> α-galactosidase in gelatin and its application in removal of flatulence-inducing sugars in soymilk

Raffinose oligosaccharides (RO) are the major factors responsible for flatulence following ingestion of soybean-derived products. Removal of RO from seeds or soymilk would then have a positive impact on the acceptance of soy-based foods. In this study, α-galactosidase from Aspergillus oryzae was entrapped in gelatin using formaldehyde as the hardener. The immobilization yield was 64.3% under the optimum conditions of immobilization. The immobilized α-galactosidase showed a shift in optimum pH from 4.8 to 5.4 in acetate buffer. The optimum temperature also shifted from 50°C to 57°C compared with soluble enzyme. Immobilized α-galactosidase was used in batch, repeated batch and continuous mode to degrade RO present in soymilk. In the repeated batch, 45% reduction of RO was obtained in the fourth cycle. The performance of immobilized α-galactosidase was tested in a fluidized bed reactor at different flow rates and 86% reduction of RO in soymilk was obtained at 25 ml h⁻¹ flow rate. The study revealed that immobilized α-galactosidase in continuous mode is efficient in reduction of RO present in soymilk.     

Immobilization of phytase on epoxy-activated Sepabead EC-EP for the hydrolysis of soymilk phytate

In this work, an active phytase concentrated extract from soybean sprout was immobilized on a polymethacrylate-based polymer Sepabead EC-EP which is activated with epoxy groups. The immobilized enzyme exhibited an activity of 0.1 U/g of carrier and activity yield of 64.7%. The optimum temperature and pH for the activity of both free and immobilized enzymes were found as 60 °C and pH 5.0, respectively. The immobilized enzyme was more stable than free enzyme in the range of pH 3.0–8.0 and more than 70% of the original activity was recovered. Both the enzymes completely retained nearly about 84% of their original activity at 65 °C. The K_m and V_max values were measured as 5 mM and 0.63 U/mg for free enzyme and 12.5 mM and 0.71 U/mg for immobilized enzyme, respectively. Free and immobilized soybean sprout phytase enzymes were also used in the biodegradation of soymilk phytate. The immobilized enzyme hydrolysed 92.5% of soymilk phytate in 7 h at 60 °C, as compared with 98% hydrolysis observed for the native enzyme over the same period of time. The immobilization procedure on Sepabead EC-EP is very cheap and also easy to carry out, and the features of the immobilized enzyme are very attractive that the potential for practical application is considerable.     

Production and Properties of a Soymilk-clotting Enzyme System from a Microorganism

Some microorganisms, including some bacteria isolated from soil, were found to secrete an extracellular soymilk-clotting enzyme. Among them, strain No. K-295G-7 showed the highest soymilk-clotting activity and stability of the production of the soymilk-clotting enzyme. The enzyme system (culture filtrate) coagulated protein in soymilk, a curd being formed at pH 5.8~6.7 and at 55~75°C. The optimum temperature for the soymilk-clotting activity was 75°C and the enzyme system was stable at temperatures below 50°C down to 35°C. About 80~100% of the original activity remained after 1 hr at pH 5~7 and 35°C.     

Heat shock induced proteins in plant cells

Tobacco (Nicotiana tabacum) and soybean (Glycine max) tissue culture cells were exposed to a heat shock and protein synthesis studied by SDS-polyacrylamide gel electrophoresis after labeling with radioactive amino acids. A new pattern of protein synthesis is observed in heat-shocked cells compared to that in control cells. About 12 protein bands, some newly appearing, others synthesized in greatly increased quantities in heat-shock cells, are seen. Several of the heat-shock proteins (HSPs) in both tobacco and soybean are similar in size. One of the HSPs in soybean (76K) shares peptide homology with its presumptive 25°C counterpart, indicating that the synthesis of at least some HSPs may not be due to activation of new genes. The optimum temperature for maximal induction of most HSPs is 39–40°C. Total protein synthesis decreases as heat-shock temperature is increased and is barely detectable at 45°C. The heat-shock response is maintained for a relatively short time in tobacco cells. After 3 hr at 39°C, a decrease is seen in the synthesis of the HSPs, and after 4 hr practically no HSPs are synthesized. After exposure to 39°C for 1 hr, followed by a return of tobacco cells to 26°C, recovery to the control pattern of synthesis requires greater than 6 hours. These results indicate that cells of flowering plants exhibit a heat-shock response similar to that observed in animal cells.     

Effect of Sorbed Water on the Thermal Stability of Soybean Protein

A soybean protein isolate (SPI), and its β-conglycinin and glycinin componets were obtained from defatted soybean flour by applying dissolution and precipitation based on the difference in their solubility depending on each isoelectric point. The purity evaluated by SDS–PAGE of the β-conglycinin and glycinin preparations was about 84% and 80%, respectively, resulting in a clear difference in the pH dependence on solubility. A BET plot derived from the water sorption isotherm at 25 °C showed that the amount of the monolayer adsorption of these preparations was about 6–9%, the value for the β-conglycinin preparation being about 1.5 times higher than that for the glycinin preparation. The β-conglycinin and glycinin preparations were respectively denatured at around 75 °C and 86 °C in the presence of excess water, whereas the denaturation temperature of both preparations was markedly increased by decreasing sorbed water content below 40%, corresponding well with the unfrozen water content.     

Ethylene action blockade and cold storage affect ripening of ‘Golden’ papaya fruit

The purpose of this work was to evaluate the effects of ethylene action blockade and cold storage on the ripening of ‘Golden’ papaya fruit. Papayas harvested at maturity stage 1 (up to 15% yellow skin) were evaluated. Half of the fruits, whether treated or not treated with 100 nL L⁻¹ of 1-methylcyclopropene (1-MCP), were stored at 23°C, while the other half were stored at 11°C for 20 days prior to being stored at 23°C. Non-refrigerated fruits receiving 1-MCP application presented a reduction in respiratory activity, ethylene production, skin color development and pectinmethylesterase activity. Even with a gradual increase in ethylene production at 23°C, fruits treated with 1-MCP maintained a high firmness, but presented a loss of green skin color. Cold storage caused a decrease in ethylene production when fruits were transferred to 23°C. The results suggest that pulp softening is more dependent on ethylene than skin color development, and that some processes responsible for loss of firmness do not depend on ethylene.     

Arabidopsis: Sensitivity of growth to high temperature

Arabidopsis thaliana seedlings as measured by an electrolyte leakage assay, have been found to be extremely sensitive to high temperature stress as compared to a high temperature tolerant variety (Tracy) of soybean. Over 50% ion leakage occurred in Arabidopsis leaves during a 15-minute exposure to 50°C, indicating a heat killing time of less than 15 minutes. In contrast, the heat killing time for soybean at 50°C was over five times longer. When soybean or Arabidopsis seedlings in culture plates were exposed to 37°C for 2 hours and then returned to 23°C, they suffered no apparent short-term or long-term damage. Soybean seedlings given a 42°C, treatment for 2 hours also showed no damage. Arabidopsis seedlings after a 42°C treatment for 2 hours showed no apparent immediate damage, but 48 hours after return to 23°C severe damage symptoms were visible and after 96 hours all the seedlings were dead. Both soybean and Arabidopsis seedlings synthesize heat shock proteins (hsps) when exposed to 42°C for 2 hours. The hsps synthesized are of similar molecular weights, although the relative abundances of the different size classes are very different in the two plants. Even though hsps are produced in Arabidopsis seedlings after a 2 hour exposure to 42°C their presence is not sufficient for the seedlings to recover from the effects of rhe heat shock when returned to 23°C. Our results show that Arabidopsis has a heat sensitive genotype. This along with its other characteristics should make it a good model system in which to assay in transgenic plants, the functions of homologous and heterologous genes that might be candidates for determining heat tolerance in plants.     

Structural Contribution of the Carbohydrate Moiety to the Alkaline Hydrolysis of Aryl Glycosylamine Linkages

Differential scanning calorimetry (DSC) thermograms of soybean protein isolate developed two peaks corresponded to 11S and 7S globulin, the denaturation temperatures of which were 93.3 and 76.5°C, respectively, with 94% water. These peaks shifted to higher temperatures with lower water contents of the sample. At 47% water, there were two peaks, at 149 and 118.7°C, and at 11% water, there was one peak at 180°C. The DSC thermogram measured during cooling and reheating gave no peak. The soybean protein isolate was heated with 24.5% water at 100°C and then mixed with more water to the water contents of 94%. This sample gave two peaks at temperatures close to those of the original soybean protein, indicating that the soybean protein was not denatured at temperatures even above 100°C when the water content was low.     

Enhancement of the thermophilic stage in cattle waste composting by addition of tofu residue

The microbial degradation and temperature rise during the composting of a cattle waste and rice straw mixture blended with tofu (soybean curd) residue was investigated using an insulated and unheated in-vessel composter (effective volume, 12 1) and a static pile with passive aeration. The addition of 11% (dry weight basis) of tofu residue shortened the time required for temperature to reach the thermophilic phase and increased the duration of the temperatures above 55 degrees C significantly, but the maximum temperature was not affected by the additive level. As shown by the change in BOD, most of the easily biodegradable matter in the tofu residue was consumed during 12 days of composting. The same results were observed in the temperature profile of the static pile with passive aeration. Tofu residue addition yielded a higher maximum temperature and a nearly two times longer duration of temperatures above 55 degrees C in almost all locations of the pile. The use of tofu residue as a co-composting material would promote thermophilic degradation throughout the entire composting mass.     

花生粕脂肪含量对豆腐品质的影响

为了确定适用于制备花生豆腐的原料的脂肪含量,以低温花生粕为原料,采用谷氨酰胺转氨酶（transglutaminase,TG）和高温微压煮浆（high-temperature pressure cooking,HTPC）工艺制备花生豆腐,研究不同花生粕脂肪含量（6.89%、10.12%、15.43%、20.28%和25.54%）对豆腐质构的影响,对比花生豆腐与市售大豆豆腐的耐煮性和色泽,并分析加工过程中花生蛋白的结构变化。结果表明,花生粕脂肪含量对豆腐质构有显著影响（P<0.05）,除脂肪含量为25.54%的花生粕外,其他脂肪含量的花生粕均可用于制备花生豆腐。当花生粕脂肪含量为6.89％时,可制得与市售大豆石膏豆腐的质构、耐煮性相当的花生豆腐产品,且其黄度值b（8.38）显著小于大豆石膏（15.86）和卤水（16.56）豆腐（P<0.05）,具有色泽优势。而对于花生蛋白结构变化的分析表明,当花生粕脂肪含量相对较低（6.89%~20.28%）时,TG对花生蛋白的作用效果较好,进一步施加HTPC处理可使花生蛋白完全变性,并且通过形成疏水相互作用和二硫键以维持豆腐凝胶结构。研究结果为花生豆腐的加工提供了技术指导和理论支撑。     

Studies on the physiological effects of viruses on sweet potato yield in Kenya

Much of the economic value of soybean (Glycine max) is based on the amount of protein and oil produced in the seeds. To examine the influence of temperature on seed oil and protein concentration, immature soybean seeds (cv. Williams 82) were grown in vitro at temperatures of 17°C, 21°C, 25°C, 29°C and 33°C. Dry growth rate (DGR) was calculated to be maximal at 23.7°C. Oil and protein concentration and seed growth rate did not show statistical difference (P > 0.05) within the temperature range from 21–29°C. Across all temperatures, however, a quadratic regression on oil concentration (R2 = 0.66) showed a minimum at 24.1°C and a quadratic regression on protein concentration (R2 = 0.59) showed a minimum at 24.3°C. Dilution by increased dry matter accumulation in the seed accounted for much of the variation in oil and protein concentration and the two concentrations were equally affected across temperatures. Consequently, oil and protein concentrations were positively related over the tested range of temperature. It was concluded that under these conditions the rate of dry matter accumulation by soybean seeds was critical in influencing seed oil and protein concentrations.     

Quality characteristic of spray-drying egg white powders

Spray drying is a useful method for developing egg process and utilization. The objective of this study was to evaluate effects on spray drying condition of egg white. The optimized conditions were spraying flow 22 mL/min, feeding temperature 39.8 °C and inlet-air temperature 178.2 °C. Results of sulfydryl (SH) groups measurement indicated conformation structure have changed resulting in protein molecule occur S–S crosslinking phenomenon when heating. It led to free SH content decreased during spray drying process. There was almost no change of differential scanning calorimetry between fresh egg white and spray-drying egg white powder (EWP). For a given protein, the apparent SH reactivity is in turn influenced by the physico-chemical characteristics of the reactant. The phenomenon illustrated the thermal denaturation of these proteins was unrelated to their free SH contents. Color measurement was used to study browning level. EWP in optimized conditions revealed insignificant brown stain. Swelling capacity and scanning electron micrograph both proved well quality characteristic of spray-drying EWP. Results suggested spray drying under the optimized conditions present suitable and alternative method for egg processing industrial implementation. Egg food industrialization needs new drying method to extend shelf-life. The purpose of the study was to provide optimal process of healthy and nutritional instant spray-drying EWP and study quality characteristic of spray-drying EWP.     

Purification and characterization of a soybean-milk-coagulating enzyme from Bacillus pumilus TYO-67

Bacillus pumilus TYO-67 was isolated from tofu (soybean curd) as the best producer of a soybean-milk-coagulating enzyme, induced by the addition of soybean protein to the growth medium. The enzyme was purified approximately 30-fold with an 11% yield. The homogeneous preparation of the enzyme showed that it is a monomer with a molecular mass of about 30 kDa and has an isoelectric point at pH 9.75. The results of amino acid composition analyses showed that the enzyme is rich in alanine, aspartic acid, glycine, serine and valine. Although the amino-terminal amino acid (alanine) was identical with that of subtilisins, the amino-terminal sequence was different from those of subtilisins. The α-helix content of the enzyme was calculated to be 28.2%. The optimum pH and temperature were observed at 6.0–6.1 and 65 °C respectively. The enzyme was significantly activated by the addition of 1 mM Mn²⁺, Ca²⁺, Mg²⁺, and Sr²⁺ ions in the reaction mixture, and its thermal stability was significantly increased by Ca²⁺ ion. Received: 31 August 1998 / Received last revision: 1 December 1998 / Accepted: 20 December 1998     

Bioremediation of Crude Oil–Contaminated Soil By Immobilized Bacteria on an Agroindustrial Waste—Sunflower Seed Husks

This study reports the immobilization and performance of a hydrocarbon-degrading Rhodococcus sp. strain (designated as QBTo) on sunflower seed husks (SH) for the bioremediation of soils polluted with crude oil. The SH performance as inoculants carrier was compared with peat, which is a vegetal material traditionally used in carrier-based inoculants production. The stability of the immobilized culture under storage conditions was assessed by viability at different times when stored at 25°C and 10°C. The catabolic activity of immobilized and free QTBo cells introduced into sandy loam soil, freshly contaminated with crude oil, was studied in microcosms. A higher number of viable QTBo cells were recovered from the inoculants formulated with SH (QTBo-SH) after prolonged storage at 10°C and 25°C. The microcosms amended with QTBo-SH inoculants showed a removal of about 66% of total petroleum hydrocarbons (TPH), whereas in those inoculated with QTBo-peat inoculants, the decrease was of about 47%. In the control microcosms (noninoculated) and liquid culture–amended soils, the TPH removal was about 28%. SH is a waste of edible oil industry, nontoxic, and biodegradable and has demonstrated to confer to the immobilized cultures greater potential to survive not only during storage but also in the soil environment, improving bioremediation process.     

Low temperature acclimation of root fatty acid composition, leaf water potential, gas exchange and growth of soybean seedlings

Abstract Root fatty acid composition, photosynthesis, leaf water potentials, stomatal resistances, leaf specific weights, and root: shoot ratios of soybean were measured in two temperature regimes. Groups of soybean plants were grown in controlled chambers of the Duke University Phytotron under two thermoperiods. One group of the plants was grown from seed for 3 weeks in either 29/23°C or 17/11°C thermoperiods, and another group was grown for 2 weeks in 29/23°C and then transferred to the 17/11°C thermoperiod where it remained for 8 days. Broccoli was also grown in either 29/23°C or 17/11°C thermoperiods. Soybean roots contained more unsaturated fatty acids than broccoli roots, although broccoli roots showed a larger increase in unsaturation than soybean roots with decreased temperature. The fatty acid unsaturation in the roots of soybean began to increase rapidly after the temperature regime was changed. The increase was in the new roots produced in the cold regime rather than in the pre-existing roots. The soybean leaf water and osmotic potentials decreased about 0.4 MPa, beginning one day after the transfer from 29/23°C to 17/11°C, but recovered significantly after 8 d. Plants grown at 17/11 °C had lower rates of photosynthesis and adaxial stomatal resistances, but higher root: shoot ratios and specific leaf weights compared to plants grown at 29/23°C. Plants grown and maintained at 29/23°C showed a steady increase in photosynthetic rates over the 8-d experimental period, whether rates were measured in 1 mol m^?3 or 9 mol m^?3 oxygen. Plants transferred to 17/11°C however maintained constant rates of photosynthesis at 1 mol m^?3 O₂, whereas at 9 mol m^?3 rates declined for 2 d then were constant for the remaining 6 d of the experimental period. These results suggest that changes in membrane fatty acid unsaturation is an important aspect of plant acclimation to chilling temperatures in terms of maintaining root permeability and water uptake. However, the degree of unsaturation is not a good indicator of differences in chilling tolerance among species. The apparent acclimation of photorespiration to a constant percentage of photosynthesis suggests a role of photorespiration in the plant.