Effect of Heating Time of Soybean on Vitamin B-6 and Folacin Retention, Trypsin Inhibitor Activity, and Microstructure Changes

Heating treatments of boiling 20 min or autoclaving 5 min, 10 min, or 20 min, of soaked (25°C for 10 hr) soybeans, significantly influenced vitamin B-6, free folacin, trypsin inhibitor activity, water absorption, moisture content and blue, green and amber color values in the cooked soybeans. Analysis of covariance showed a relationship (P≤0.05) between water absorption after cooking with total folacin in cooked soybeans and water absorption after cooking with blue color values. Other relationships (P≤0.05) were observed in cooked soybeans between texture and total folacin, moisture and trypsin inhibitor activity, and trypsin inhibitor activity and free folacin.     

Presence of Nonprotein Trypsin Inhibitor in Soy and Winged Beans

The total trypsin inhibitor was determined in extracts of 11 cultivars of soybeans and 11 strains of winged beans. The proteins in the extracts were precipitated by 16% trichloroacetic acid (w/v), and nonprotein trypsin inhibitor activities were determined in the protein-free supernatants. The nonprotein trypsin inhibitor activities varied between 10.32 ± 1.39 and 24.41 ± 1.04 units/mg defatted soybean samples and in winged beans ranged between 2.65 ± 0.62 and 6.79 ± 0.27 units/mg defatted samples. The nonprotein trypsin inhibitor composed 27–55% of the total trypsin inhibitor activity in the soybeans, and 5–14% of the total activity in winged beans.     

Composition,toxic and antinutritional factors of newly developed cultivars of Brazilian soybean (Glycine max)

Five different recently released Brazilian soybean cultivars (Bays, BR-10, Rio Balsas, Serido and Tropical) were compared for their proximate analyses and presence of antinutritional or toxic factors. As expected, the seeds are rich in proteins, varying from 360·7 to 485·4 g kg⁻¹ flour, and they also have a high amount of fat (from 183·0 to 215·3 g kg⁻¹ flour). Crude extracts from seeds of Bays, BR-10, Serido and Tropical were highly toxic to mice within 1–12 h, depending on the administration route (intraperitoneal, intramuscular or subcutaneous) and dose used while Rio Balsas was not. These acute effects were very similar to those produced by the soytoxin, a neurotoxin that has been recently purified from the commercial soybean sold in Brazil. The amount of trypsin inhibited in the presence of crude extracts ranged from 28·5 to 62·5 g kg⁻¹ flour. Urease was also present and the seed lectin agglutinated preferentially rabbit erythrocytes. A heat treatment at 92°C for 1 min destroyed completely the toxic activity while the haemagglutinating and trypsin inhibitor activities were abolished within 5 min. At these conditions urease was still active. Due to its high protein content, lack of soytoxin, and low levels of trypsin inhibitor, lectin, and urease it is suggested that Rio Balsas could be an alternative for breeding programmes aimed to improve the nutritional quality of soybeans. ©1997 SCI     

A simple blanch-dry process for lipoxygenase inactivation in soybean cotyledons

Full-fat flour from unblanched soybeans develops a beany flavour during milling due to lipoxygenase activity; the flour also becomes bitter during storage. The minimum thermal treatment necessary to inactivate lipoxygenase in soybeans before milling was determined. Soybeans were dehulled and cotyledons blanched in water between 80 and 99.3°C. Water blanching for 3 min at 99.3°C was necessary when blanched cotyledons were subsequently sun dried, and the flour had a nitrogen solubility index (NSI) of 37.8% and residual trypsin inhibitor activity (TIA) of 64.2%. Only 1.5 min blanching was necessary to inactivate lipoxygenase in soy cotyledons if they were dried subsequently at 60°C; NSI of this flour was 32.7%, with 44.7% residual TIA.     

Effect of temperature and time during steam treatment on the protein quality of full-fat soybeans from different origins

Soybeans (Glycine max) of Argentinian and Chinese origin were steam-processed at 102°C, 118°C and 136°C for various durations with the use of a laboratory-scale steam toaster. Samples of raw and processed soybeans were analysed for dry matter (DM), crude protein (CP), trypsin inhibitor activity (TIA), protein dispersibility index (PDI) and reactive lysine content. Chinese raw soybeans showed higher levels of CP, TIA and PDI, and a lower level of reactive lysine than Argentinian raw soybeans (366 vs 357 g kg⁻¹, 20.6 vs 15.2 mg g⁻¹, 87.6 vs 85.6% and 17.4 vs 19.4 g kg⁻¹, respectively). Both the TIA and PDI of the two soybean samples were decreased following a logarithmic pattern with the lengthening of the heating time when beans were steam heated at various temperatures. The reduction rates for TIA and PDI, however, were different between the two origins of soybeans. Chinese soybeans required a longer time or a higher temperature to reduce their TIA to a safe level in comparison with Argentinian soybeans. In the case that the beans were heated at 136°C, the difference in PDI between Chinese and Argentinian soybeans was smaller. It is concluded that the two soybeans origins need different processing conditions to improve their protein properties. © 1998 SCI.     

Biologically Active Components Inactivation and Protein Insolubilization during Heat Processing of Soybeans

Inactivation of lipoxygenase, trypsin inhibitor, urease and retention of protein solubility during water blanching of dehulled soybeans at 90°, 95° and 100°C were investigated. Lipoxygenase was the most heat labile, followed by urease and then trypsin inhibitor. Processing time based on “acceptable inactivation time” (AI) was proposed. AI value was longest for trypsin inhibitor, followed by urease and then lipoxygenase. The combined effect of heat on protein solubility and biologically active components inactivation was expressed as “PDI at acceptable inactivation time” (PDIAI). PDIAI value for the processing “limiting factor,” trypsin inhibitor inactivation, at the three temperatures were 36.7%, 42.5%, and 34.8%, respectively.     

Roasting of Navy Beans (Phaseolus vulgaris) by Particle-to-Particle Heat Transfer

A rotating chamber dry roaster using pre-heated ceramic beads as heat transfer media was used to roast navy beans. Processing conditions were: beads temperature, 240 and 270°C; bean-to-bead ratio, 1/10 and 1/15 and contact times of 1 and 2 min. Product temperatures achieved ranged from 92–125°C for the eight runs. Heat transfer coefficients varied from 3.6–23.4 W/(m²) (°C). Roasted products showed reduced water-soluble nitrogen content and gel forming capacity, increased water-holding capacity and cold paste viscosities, and no changes in available lysine and degree of starch damage. Residual trypsin inhibitor (TIA) and hemagglutinin activity varied from 92 to 22%, and 48 to 1%, respectively. A correlation was found to exist between nitrogen solubility index and TIA of products. Roasting caused fracture and separation of hulls, and facilitated their removal.     

Phytochemical profiles of black and yellow soybeans as affected by roasting

The current research aimed to compare the changes of phytochemicals, antioxidants, and anti-nutritional factors of yellow and black soybeans upon roasting. Yellow soybean was roasted at 210°C for 35 min and 230°C for 25 min, and black soybean was roasted at 210°C for 30 min and 230°C for 25 min. Isoflavones were significantly increased after the roasting process, while trypsin inhibitor was significantly decreased. The roasting process combined with the soaking process led to decrease in anthocyanin, soyasaponin, and antioxidant capacities. Black soybeans had more apparent variations in compounds than the yellow soybeans. For black soybeans, the processing under 230°C for 25 min presented more decrease in trypsin inhibitor and anthocyanin content. The roasting at a high temperature and short time produced products with a light color. Roasting combined with the soaking process had negative impacts on both yellow and black soybeans, but there were slight differences in the resultant compounds between different roasting temperatures.     

豆浆中抗营养因子的去除方法

采用碱液浸泡、微波处理、加热处理、去皮等方法,对去除豆浆中抗营养因子的效果进行比较。其中,88℃恒温热处理10min可将豆浆中脂肪氧化酶活性降至常温下的14.20%,100℃恒温热处理20min可将豆浆中的胰蛋白酶抑制剂降低到9.96%。微波处理(2450MHz,800W)2min可以将脂肪氧化酶活性降至8.86%,处理8min可以将胰蛋白酶抑制剂活性降低到11.24%,处理4min即可将尿素酶活性降低至1%。相比于常规的热处理,微波处理可以更快速地破坏豆浆中的抗营养因子,缩短处理时间。此外,采用0.5%NaHCO3溶液浸泡、去皮等措施也可去除豆浆中的抗营养因子,可结合常规热处理、微波处理应用,以缩短加工时间。     

Effect of soaking,dehulling, and cooking methods on certain antinutrients and in vitro protein digestibility of bitter and sweet lupin seeds

Effect of several physical treatments (soaking, dehulling, ordinary cooking, microwave cooking, and autoclaving) on the level of antinutrients and in vitro protein digestibility of bitter and sweet lupin seeds were investigated. The raw bitter and sweet lupin seeds were found to contain phytic acid, tannins, trypsin inhibitor activity, and lectin activity, but α-amylase inhibitor was absent. Dehulling significantly increased the levels of phytic acid (PA), trypsin inhibitor activity (TIA), and tannins, but lectin activity was not changed. Also soaking in bitter (for 96 hr) and sweet (for 24 hr) seeds caused a significant increase in these factors except lectin activity. Cooking methods differently affected the levels of the antinutrients. Thus, PA increased but tannins were not changed, on the other hand TI and lectin activities were inactivated; ordinary cooking and autoclaving were the most effective in both seeds. For combination effect, soaking following cooking treatments significantly decreased PA, tannins, and lectin activity, but increased TIA in both seeds. Moreover, dehulling following soaking and cooking methods resulted in a significant increase of PA, TIA, and tannins. In vitro protein digestibility (IVPD) of raw bitter and sweet lupin seeds were 78.55 and 79.46%, respectively and it was improved by all processing methods; soakingdehulling after autoclaving was the most effective in both seeds. Although some treatments increased the level of antinutrients, they improved IVPD. Therefore, the studied antinutrients are not the only responsible factor for lowering IVPD.     

Factors affecting the in vitro protein digestibility of chickpea albumins

In vitro protein digestibility (IVPD) of chickpea albumins and its possible relationship to their structure and the presence of trypsin inhibitor activity (TIA) have been studied. Trypsin digestion of the albumin fraction under non‐reducing conditions was incomplete, while the reduction of inter‐ and intramolecular disulphide bonds caused an improvement in the accessibility of sites susceptible to trypsin digestion. Trypsin inhibitor activity in the chickpea albumin fraction was dependent upon both temperature and heating time. Although heating the albumin fraction at 100 °C for 30 min reduced the TIA by more than 50% with respect to the initial activity, an important TIA rate was attributable to heat‐resistant trypsin inhibitor. The TIA decrease was not related to an increase in the rate of IVPD. However, we observed a significant (P ≤ 0.05) increment in IVPD in the presence of β‐ME, confirming the essential role of disulphide bonds in stabilising the protein structure of the albumin fraction. © 2000 Society of Chemical Industry     

Quality attributes of vegetable soybean as a function of boiling time and condition

Vegetable soybeans are marketed fresh or frozen, either shelled or in pods. The objective of this research was to characterise the change in quality attributes of vegetable soybean with boiling time (0–20 min), and presence/absence of pods, using an electrical-resistance stove or a steam-jacketed kettle. Trypsin inhibitor activity (TIA), texture, colour, soluble sugars, nitrogen, calcium and iron content were analysed. Blanching using a steam-jacketed kettle for approximately 2 min rendered 80% inactivation of TIA, and resulted in high colour, texture and sucrose. There were no differences between blanching in pods or shelled for TIA, colour and texture; however, blanching in pods prevented losses of sucrose. Blanching did not affect iron, mono- and oligosaccharide levels, but increased nitrogen and calcium content. Additionally, we observed that all traits decreased linearly with cooking time when using an electrical-resistance stove, except for calcium and nitrogen that increased, and oligosaccharides that remained constant.     

Trypsin Inhibitor Activity and Tannin Content Do Not Affect Calcium Bioavailability of Three Commonly Consumed Legumes

Calcium bioavailability from legumes containing a range in trypsin inhibitor activity (TIA) and tannin concentration was studied. Three cultivars (Phaseolus vulgaris) were hydroponically grown and intrinsically labeled with ^4SCa. Raw and cooked legumes were fed to six groups of 6-wk old male Sprague-Dawley rats. Another group received an intraperitoneal (IP) injection of ⁴⁵Ca. An eighth group was fed a casein metal extrinsically labeled with ⁴⁵Ca. The absorption of calcium from legumes by rats averaged 47.1 ± 7.5% of IP dose. Average phytate content of the legumes was 1.7% and oxalate 0.37%. Raw legumes had an average of 15000 TIA units/g of whole bean, which were completely removed by cooking. Calcium absorption was unaffected by TIA or tannin content. Reduced availability of bean calcium was likely due to phytate and/or oxalate present in legumes.     

Relationship between physicochemical and cooking properties,and effects of cooking on antinutrients,of yellow field peas (Pisum sativum)

The relationship between the physicochemical and cooking properties of yellow peas was examined in this study. A positive correlation was found between seed weight and water hydration capacity. The Peleg model, which was modified, could be used to describe the water absorption characteristics of peas and could be used to predict the rate of water absorption in the initial water absorption period. Cooking time could be measured objectively using the Mattson cooker. Cooking time was found to decrease with an increase in water hydration capacity. Hardness of cooked peas, measured using a texture analyser, was negatively correlated with both seed weight and water hydration capacity. Seed coats had a significant effect on water hydration and cooking quality of peas. Peas with relatively thin seed coats exhibited higher water hydration capacity, shorter cooking times and softer texture after cooking. The effects of soaking and cooking on trypsin inhibitor activity (TIA) and oligosaccharide levels in peas were also studied. Cooking was more effective than soaking in reducing TIA levels and oligosaccharides (raffinose, stachyose and verbascose) in peas. Copyright © 2003 Society of Chemical Industry     

Influence of processing on available carbohydrate content and antinutritional factors of chickpeas

 The effect of chickpea processing (soaking, soaking plus cooking and dry heating) on the content of available carbohydrate (monosaccharides, disaccharides and starch) and antinutritional factors (α-galactosides and trypsin inhibitor activity) was studied. Soaking produced a reduction in available carbohydrates (19–20%) and α-galactosides (16–27%), and either did not affect or caused a slight reduction of trypsin inhibitor activity (TIA) in chickpeas. Soaking plus cooking brought about a larger decrease in available carbohydrates (23–24%) and α-galactosides (45–58%), and completely eliminated TIA. Dry heating caused a 24% reduction in available carbohydrates, a 46% decrease in α-galactosides and a 27% decrease in TIA. Overall, cooking the presoaked seeds in water, acidic or basic solution seems to be adequate to obtain a chickpea flour with a large reduction in antinutritional factors (α-galactosides and TIA) and also a high level of available carbohydrate content. Received: 22 April 1999 / Revised version: 28 June 1999     

Processing peas for producing macaroni

 Pea flour from green and yellow mature pea seeds (Pisum sativum) was processed by adding emulsifiers (Glycerol-monostearate GMS, and Amidan 250B polar type monoglyceride, A250). Doughs obtained were cooked for 15 min and 30 min in order to investigate the effect of the presence of emulsifiers and cooking treatment. The quality of macaroni was examined, cooking properties were defined and sensory assessment established. Changes in protein structure were studied by solution fractioning and SDS-PAGE. Modification of the monosaccharide, disaccharide and α-galactoside contents and trypsin inhibitor activity (TIA) were also studied. The addition of emulsifiers improved dough quality. Emulsifiers fundamentally change the solubility of protein fractions, and they were able to promote the soluble fraction molecular weight distribution and the infiltration of low molecular weight fractions into the protein network. The soluble carbohydrate content was not modified by the addition of emulsifiers whilst cooking time affected its content. α-Galactoside content and TIA were reduced after the addition of emulsifiers and the cooking of peas. Received: 2 November 1995/Revised version: 12 February 1996     

Identification and stability of trypsin inhibitor isoforms in pea (Pisum sativum L.) cultivars grown in New Zealand

Trypsin inhibitor activity (TIA) of 17 spring-sown field pea cultivars grown in New Zealand ranged from 0.33 to 0.75 TIU/mg DM. These values were much lower than those reported for most European pea cultivars. After soaking and cooking, values fell by 42–91%, with an average reduction of 78% (0.07–0.19 TIU/mg DM). After heat treatment, the residual percentage of TIA was negatively correlated to the amount of TIA in the raw seed. Six to ten trypsin isoinhibitors were observed in each cultivar of the raw extracts, with isoelectric points ranging from 4.6 to 7.6. Only three of the isoinhibitors, with isoelectric points of 5.1, 5.9 and 7.6, remained after heat treatment.     

Effects of Water,Steam and Shear Conditioning on the Protein Quality of Soy Grits

The effect of adding steam (at 0·6 and 1·2 bar) and water (1·9% and 64% of the flux of soy grits) in a conventional barrel type conditioner and its effects on protein dispersibility index (PDI), nitrogen solubility in 0·2% KOH and trypsin inhibitor activity (TIA) of commercial soy grits was studied. In addition, conditioned soy grits were subjected to expander treatment at two different screw speeds (2 and 3 rps) and PDI, NSI and TIA were measured. Analysis of variance was used to determine the effects of steam pressure, water addition and screw speed on the mentioned protein quality parameters. In addition, resultant temperature from steam addition was used in an analysis of covariance to determine the effects of temperature as a covariate, water addition and screw speed on protein quality parameters. A significant interaction for steam pressure and water addition was found on all parameters. The highest denaturation or inactivation of the protein was found at the combination incorporating high steam and high water addition. Screw speed during expander treatment did not significantly affect protein quality parameters. It was concluded both from this study and from literature that PDI is a better parameter to evaluate technological treatments when low amounts of motor power are dissipated (<110 kJ kg^-1) and that NSI in 0·2% KOH is a better parameter to discriminate between technological treatments when moderate to high amounts of motor power are dissipated in soy grits. TIA decreased with increasing water or steam content. The effect of trypsine inhibitor inactivation in soy grits was highest at higher temperatures and was not affected by screw speed of the expander. © 1997 SCI     

Acid Inactivation of Soybean Lipoxygenase With Retention of Protein Solubility

The use of acids to inactivate lipoxygenase in soybeans with retention of protein solubility was investigated. Inactivation of lipoxygenase was found to be irreversible when treated at pH 3.0 and below, irrespective of the acids used. The SDS-PAGE pattern showed the disappearance of lipoxygenase bands when soybeans were acid-treated at pH 3.0 and below. Acid treatment showed no effect on trypsin inhibitor and 60% trypsin inhibitor activity was removed by whey separation. Activity of urease was reduced to below 0.2 pH, when lipoxygenase was inactivated. PDI's of 70–76% were retained in the neutralized full-fat soy flour after treatment with acids at about pH 3.0 while full-fat soy material was 52–55%.     

豆浆中脲酶活性测定方法的建立及酶学性质的研究

生豆浆中的胰蛋白酶抑制因子在实验室中较难检测,但其活性与脲酶活性呈正相关。对此建立了豆浆中脲酶的定量检测方法,并对其酶学性质进行研究。结果表明,采用纳氏试剂测定豆浆脲酶活性的最适条件为:波长415nm,显色剂用量1mL,尿素浓度3%,反应温度35℃,反应时间7min。豆浆中脲酶的最佳作用pH为7.0,最适反应温度为35℃,脲酶在25～40℃之间贮存3h有较好的热稳定性,酶活保留率在80%以上。利用Lineweaver-Burk双倒数作图法求得脲酶的Vmax为0.173mmol/min,Km为0.0172mol/L。