Effect of γ-irradiation on soya bean proteins

The properties of soya bean proteins following γ-irradiation (5–20 kGy) were investigated in connection with protein denaturation. Irradiation doses above 10 kGy caused a decrease in 7S and 11S components and an increase in 2S and 15S components (P < 0.05). However, subunit patterns determined by electrophoresis were not changed appreciably over the entire irradiation dose range. In the differential scanning calorimetry thermogram, the denaturation temperatures of 11S and 7S components were not affected by γ-irradiation, while increased irradiation dose caused a decrease in the enthalpy values of 11S and 7S components due to protein denaturation. Changes in the circular dichroism spectra and tryptophan fluorescence intensity (P < 0.05) were observed only at 20 kGy.     

Reduction in flatulence factors in mung beans (Vigna radiata) using low‐dose γ‐irradiation

Mungbeans (Vigna radiata), control and γ‐irradiated at insect disinfestation dose levels (0.25 and 0.75 kGy) were germinated (0–6 days) and the qualitative and quantitative changes in soluble carbohydrates were studied in detail. The key flatulence‐producing raffinose family oligosaccharides in mungbeans were degraded in the irradiated samples at the onset of the germination (0–2 days) compared to the control where it occurred much later (>4 days). However, the reducing sugars, mainly glucose, fructose and galactose, which are metabolised easily, were enhanced in the irradiated samples. At low dose (0.25 kGy), irradiation had no effect on germination and sprout length, indicating that irradiated beans are suitable for use as sprouted beans. These observations clearly indicate that γ‐irradiation at insect disinfestation dose levels improved the digestibility and nutritional quality of mung beans by reducing the content of oligosaccharides responsible for intestinal gas production. © 1999 Society of Chemical Industry     

Total inactivation of lipoxygenase in whole soya bean by pulsed light and the effect of pulsed light on the chemical properties of soya milk produced from the treated soya beans

The inactivation of lipoxygenase (LOX) in the whole soya bean prevents lipid oxidation that produces an off‐flavour of soya food. The inactivation of lipoxygenase in the whole soya bean by pulsed light (PL) was examined with three distances (5, 7 and 9 cm) from the PL strobe and for different durations. Soya bean was treated with PL with and without ice surrounding the soya bean sample tray for limiting the rise in sample temperature. Results show that without ice surrounding the sample tray, the lowest LOX residual activity was 4.7%, 0.4% and 0.0% for 80‐s duration at 5 cm distance from the PL strobe, 110 s at 7 cm from the strobe and 150 s at 9 cm from the strobe, respectively; the soya bean temperature after treatment was 109.6, 116.3 and 114.8 °C, respectively. The instantaneous temperatures of the soya bean core measured during PL operating were above 100 °C. The lipoxygenase band was disappeared after longest PL treatments of each distance compared with the LOX band control as assessed by electrophoresis. The pulsed light had no negative effect on peroxide value of produced soya milk. However, PL reduced significantly the total solid amount and changed the colour of the produced soya milk. The residual activity with sample cooling by ice during treatment was 79.0%, 98.8% and 95.7%, with sample temperatures of 81.7, 91.2 and 66.9 °C, respectively. This study indicates that PL illumination could fully inactivate LOX in whole soya beans, with the photo‐thermal effect of PL as the main factor responsible for the inactivation of LOX.     

Response of intestinal proteinase activities to the feeding of isolated winged bean (Psophocarpus tetragonolobus) and soya bean (Glycine max) trypsin inhibitors in rats

The antinutritional activities of trypsin inhibitors (TIs) were compared between winged beans (Psophocarpus tetragonolobus) and soya beans (Glycine max). The inhibitors of the two beans were isolated by trypsin‐bound Sepharose 4B, and 50 mg of lyophilised powders were intubated intragastrically into 24 h fasted rats. The activities of trypsin and chymotrypsin were compared after 30, 60 and 180 min in the washings of the upper, middle and lower parts of the small intestine. The elution profiles of TI and non‐TI compounds in the affinity chromatography were similar in the two beans, and the antitryptic activities were concentrated 5.5 and 6.2 times (based on specific activity) for winged beans and soya beans respectively. Regardless of the TI fed to rats, trypsin activity in the upper intestine was suppressed to almost undetectable levels at 30 and 60 min after intubation. The activities in the middle and lower intestines were also substantially lowered when rats were fed winged bean TI, and significant differences were detected at 30 and 60 min after intubation when compared with rats fed soya bean TI. However, at 180 min after feeding, no differences were found in the trypsin activity in any gut segments. Similar inhibitory properties of isolated TIs were observed in chymotrypsin activities in the small intestine. The results suggest that winged bean TI may have greater inhibitory activity on the intestinal proteinase compared with soya bean TI. © 2001 Society of Chemical Industry     

The yield,fatty acid composition and physical properties of milk fat obtained by feeding soya oil to dairy cows

The presence in the bovine mammary gland of a desaturase specific for the conversion of stearic to oleic acid allows the manipulation of the physical properties of milk fat by varying the dietary intake of C₁₆ and C₁₈ fatty acids. In particular, feeding the dairy cow an oil with a high C₁₈: C₁₆ ratio should allow the proportion of milk fat that is liquid at 5°C to be increased, with a consequent improvement in the low-temperature spreadability of butter. In this paper, the effect of feeding concentrate rations containing (a) soya oil as the free oil and as cracked soya beans; (b) various levels of soya oil, the ration being offered twice or 24-times daily, on the thermal properties of the milk fat and on the yield of milk constituents is examined in detail. Feeding ratios containing free soya oil greatly increased the proportion of milk fat liquid at 5°C, whereas cracked soya oil gave only slight increases. Proportion and yield of milk fat were decreased by feeding soya oil twice daily but were increased by continuous feeding.     

Preservation of iced refrigerated sea bream (Sparus aurata) by irradiation: microbiological, chemical and sensory attributes

Quality and shelf life of non-irradiated and irradiated (2.5 and 5 kGy) sea bream in ice conditions and stored at +4 °C were investigated by measurement of microbiological, chemical and sensory analysis. Microbial counts for non-irradiated sea bream samples were higher than respective irradiated fish. Total volatile base nitrogen (TVB-N) values increased value of 38.64 mg/100 g for non-irradiated, sea bream during iced storage whereas for irradiated fish lower values of 13.48 and 12.06 mg/100 g were recorded at 2.5 and 5 kGy, respectively (day 19). Trimethylamine (TMA-N) values and thiobarbituric acid (TBA) values for irradiated samples were lower than non-irradiated samples. Acceptability scores for odour, taste and texture of cooked decreased with storage time. The sensory scores of sea bream stored in control and 2.5–5 kGy at +4 °C were 13 and 15 days, respectively. The results obtained from this study showed that the shelf life of sea bream stored in ice, as determined by overall acceptability all data, is 13 days for non-irradiated sea bream and 15 days for 2.5 kGy irradiated and 17 days for 5 kGy irradiated sea bream.     

Compositional and quality characteristics of paneer made from soya beans and buffalo milk under different heat treatments

Soya—buffalo milk (SBM) paneer was prepared from an admixture (1: 1 w/w, wet basis) of buffalo milk and tofu, the latter made by two methods (boiling and pressure cooking). Calcium sulphate (20 g litre^?1) and citric acid (100 g litre^?1) were used as coagulants for tofu and SBM-paneerpreparations, respectively. Significant differences (P0.05) were observed in the yield of okara and hulls of soya beans in the two methods. However, no significant differences were observed in the yield and composition of tofu. SBM-paneer( unfried and fried) showed no significant difference in composition between the methods, excepting the moisture and fat levels in the unfried SBM-paneer. Fried SBM-paneer prepared by pressure cooking showed a significant difference in the sensory score. Comparative appraisal of the composition of tofu, SBM-paneer ( fried and unfried) and whey obtained in the two methods are presented.     

Preparation and characterisation of soya milk enriched with isoflavone aglycone fermented by lactic acid bacteria combined with hydrothermal cooking pretreatment

A fermented soya milk (FSM) enriched with isoflavone aglycone (FSM‐SPIA) was prepared from heated soya protein isolate (SPI)‐isoflavone complex. After 48 h of fermentation, FSM‐SPIA contained higher contents of living bacteria, free amino acids and aglycone compared with the FSM of SPI (FSM‐SPI) and the FSM of SPI‐isoflavone complex (FSM‐Mix). In the in‐vitro digestion experiment, FSM‐SPIA showed higher antioxidant capacity and isoflavones (ISO) bioavailability than FSM‐SPI and FSM‐Mix. This was likely due to the soya milk containing a higher level of amino acid, peptides and the presence of soya bean isoflavone. The improved protein digestibility, the interaction and binding ability between proteins and ISO may affect the properties of the protein and the fermented products. The FSM enriched with isoflavone aglycone can be used as a functional fermented drink, as well as an auxiliary food for menopausal women during a specific pathological period.     

Effect of γ-irradiaton on the volatile compounds of licorice (Glycyrrhiza uralensis Fischer)

The volatile compounds of non-irradiated and 1, 3, 5, 10 and 20 kGy γ-irradiated roots of licorice (Glycyrrhiza uralensis Fischer) were isolated by simultaneous distillation–extraction (SDE) technique and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 61 volatile compounds belonging to the chemical classes of acid (2), alcohol (16), aldehyde (8), ester (6), furan (2), hydrocarbon (14), ketone (10) and N-containing compounds (3) were identified in non-irradiated licorice. The prime volatile compound of licorice was 2-ethoxy-1-propanol, which makes up to 22.82% of the total composition. Over a dose of 1 kGy, another compound, benzaldehyde appeared, whereas other compounds, 3,5-dimethyl octane and phenethyl alcohol, disappeared at the dose of 20 kGy. Though the content of several volatile compounds increased after γ-irradiation, the content of major volatile compounds such as 4-terpineol, myrtenal, tetramethylpyrazine, hexanoic acid, azulene and p-cymene decreased. In comparison to non-irradiated licorice, 10 kGy dose of irradiation induced the maximum level of total yield of volatile compounds by 12%, but slightly decreased at 20 kGy. Therefore, the application of γ-irradiation is feasible without major qualitative and quantitative loss of volatile compounds when exposed at 10 kGy.     

Irradiation temperature influences product quality factors of frozen vegetables and radiation sensitivity of inoculated Listeria monocytogenes

Four frozen vegetables (broccoli, corn, lima beans, and peas) were gamma irradiated at subfreezing temperatures ranging from -5 to -20 degrees C to determine (i) the radiation sensitivity of an inoculated outbreak strain of Listeria monocytogenes (ATCC 49594), (ii) the effect of changing irradiation conditions (i.e., temperature) on that sensitivity, and (iii) the effect of the recommended radiation dose on the texture and color of irradiated frozen vegetables. The amounts of radiation necessary to reduce the bacterial population by 90% (D10-values) for L. monocytogenes differed significantly among vegetables at each irradiation temperature. D10 increased significantly with decreasing temperature for all vegetables, with each vegetable showing a different response pattern. At an irradiation temperature of -5 degrees C, D10 ranged from 0.505 kGy for broccoli to 0.613 kGy for corn. At -20 degrees C, D10 ranged from 0.767 kGy for lima beans to 0.916 kGy for peas. At -20 degrees C, radiation doses sufficient to achieve a 5-log10 kill (3.9 to 4.6 kGy) caused significant softening of peas and broccoli stems but not of corn or lima beans. Lower doses of comparable antimicrobial efficacy delivered at -5 degrees C (2.5 to 3.1 kGy) did not cause significant changes in texture in any vegetable. Color varied significantly among the dose-temperature combinations only for broccoli florets; this variation did not demonstrate a clear pattern of quality changes in response to irradiation.     

Saponin content of soya beans and some commercial soya bean products

Quantitative thin layer chromatography has been used to estimate the saponin content of whole soya beans (Glycine max L. Merrill, cv. Williams) and a number of commercial soya bean products such as protein isolates and lecithin. Saponins were present in all these materials at concentrations ranging from 56 g kg-¹ (on a dry weight basis) for whole soya beans to 3 g kg-¹ for the protein isolate ?Promine-D’?. Previous estimates indicate a saponin content of whole soya beans of only about 5 g kg-¹. It is suggested that this is an underestimate resulting from loss of material during the extraction procedures used in earlier methods of analysis.     

Saponin content of soya and some commercial soya products by means of high-performance liquid chromatography of the sapogenins

Quantitative high-performance liquid chromatography of the sapogenins was used to estimate the saponin content of soya beans (Glycine max (L.) Merr.) and commercially prepared soya flours, protein concentrate, protein isolate and soya milks. The level of saponin in whole soya beans as estimated (0.47%) was in agreement with other recent estimates. Saponins were also found in the various soya flours (0.43–0.67%), protein isolate (0.76%), soya milks (0.022–0.026%) but not in the protein concentrate.     

Antioxidant properties of methanolic extracts from Antrodia camphorata with various doses of γ-irradiation

The mycelia of Antrodia camphorata (Chang & Chou) Wu, Ryvarden & Chang were irradiated with gamma rays at doses of 2.5, 5, 10, 15 and 20 kGy and the antioxidant properties of the methanolic extracts were studied. At 2.5 mg/ml, antioxidant activities of methanolic extracts from 10 to 20 kGy-irradiated mycelia were significantly higher than those of the non-irradiated control. Reducing powers of methanolic extracts from unirradiated and 0.5–7.5 kGy-irradiated mycelia were comparable except for the 20 kGy-irradiated mycelia. At 2.5 mg/ml, all methanolic extracts showed excellent scavenging abilities of 92.3–103% on DPPH radicals. Scavenging abilities of methanolic extracts from 2.5 to 20 kGy irradiated mycelia were better than that of the unirradiated control at 10 mg/ml. With irradiation at 5–20 kGy, mycelia possessed higher chelating ability on ferrous ions than did the unirradiated control. The EC₅₀ values were below 15 mg/ml, except for values of scavenging ability of the unirradiated control on hydroxyl radicals. Total phenols were the major naturally occurring antioxidant components found in the range of 13.0–15.5 mg/g. In summary, γ-irradiation not only maintained the antioxidant properties of mycelia but also enhanced the antioxidant properties to some extent.     

Postharvest changes in physicochemical characteristics and free amino acids content of immature vegetable soya bean (Glycine max L.) grains

The aim of this study was to investigate the changes in physicochemical characteristics and free amino acid profile occurring in immature vegetable soya bbean during postharvest storage under three temperatures [5, 10 and 20 (control), ±1 °C] for 7 days. The results showed that a lower temperature provided an effective control in reducing weight loss, maintained firmness, delayed changes in the pod colour and soluble sugars concentration. Twenty‐two free amino acids in immature soya beans also identified by the ¹H NMR spectroscopy were strongly affected by postharvest temperature, and there were time‐specific differences in the concentration. Those significant differences in free amino acids concentration among storage conditions were closely associated with aspartate and glutamate degradation. Additionally, after 7‐day storage at 5 and 10 °C, the soya bean grains accumulated the highest amount of some essential and flavour amino acids, which revealed storage conditions selected should be dictated by the goal.     

Trypsin inhibitory activity of raw soya bean after incubation with rumen fluid

Four soya bean (Glycine max Merr) inbreds, two of which (Williams 82 and Amsoy 71) capable of synthesising the Kunitz trypsin inhibitor (high trypsin inhibitory activity (TIA)) and two (L81–4590 and L83–4387), nearly isogenic to the former but lacking this particular function (low TIA) were used. In-vitro trials were performed to evaluate the residual TIA of flours incubated with runem fluid and the possible effect of proteinase inhibitors on rumen microbial fermentation, estimated by gas production. Only a slow fall in TIA was observed after short incubation times (5–10% at 2 h and 10–18% at 6 h), but after this period the rate of decline of TIA accelerated to give residual TIA of about 50% after 12 h and undetectable values after 48 h. Significant differences between genetic backgrounds were observed only at 2 h, when the Williams 82 background had a faster initial loss of TIA (89.1 versus 97.5% of the original activity, P < 0.01). Different patterns of TIA degradation were observed according to the presence/absence of the Kunitz inhibitor: inbreds lacking the Kunitz inhibitor initially had a higher residual TIA (95.9 versus 90.7%, P < 0.01) while at 12 and 24 h the residual TIA was considerably lower with respect to the other inbreds (45.4 versus 60.8 and 10.7 versus 20.4, respectively, P < 0.01). Gas production after 2 and 6 h of incubation was similar across treatments, whereas slightly but consistently more (P < 0.05) gas was produced at longer incubation times for inbreds lacking the Kunitz inhibitor. The results indicated that the proteinase inhibitors contained in raw soya bean are degraded at a much slower rate than previous nylon bag studies have suggested and that the presence of the Kunitz inhibitor leads to a higher residual TIA after rumen degradation and slightly lower microbial gas production.     

高效液相色谱法测定大豆发酵制品中的生物胺

目的从生物胺角度初步探讨大豆发酵制品的食用安全性,为确定大豆发酵制品的推荐安全摄入水平提供初步参考。方法采用柱前衍生高效液相色谱法检测大豆发酵制品中生物胺的含量,以0.4 mol/L高氯酸为提取液,以丹酰氯为衍生试剂,紫外检测波长254 nm。结果样品组分分离及测定结果重现性较好,豆豉、豆酱、酱油3种大豆发酵制品均有部分品牌组胺含量超过危害作用水平(即500 mg/kg),8个样品中有7种超过100 mg/kg,同类不同品牌大豆发酵制品间组胺含量没有明显差别;色胺均未检出;除组胺外,3种大豆发酵制品中尚可能存在2-苯乙胺、腐胺及尸胺。结论大豆发酵制品的色胺未检出,组胺含量较高,大量食用可能影响人体健康。     

Changes in the colour and the acidity number of egg yolk upon irradiation

Eggs from laying hens were irradiated using radioactive Co-60 at a dose of 1 kGy, 2.5 kGy, and 5 kGy, with a dose input of 3.21 kGy h^–1. Parameters describing the colour of egg yolk such as L*, a*, and b*, were determined spectrophotometrically using the CIELAB system with the help of the portable spectrophotometer Superchroma S-Spex without gloss. The levels of all three parameters dropped upon ionizing radiation. While at a dose of 1 kGy the difference in the parameters was not statistically conclusive, after irradiation using doses of 2.5 kGy and 5 kGy, the levels of the parameters L*, a*, and b* showed a statistically conclusive decrease which was also accompanied with changes in sensorial properties such as decolouration and decreased colour. The colour of the yolk was evaluated according to the Roche scale, showing that more significant changes occurred upon irradiation at doses of 2.5 and 5 kGy (the value decreased from 6 to 5). The number of acidity estimated in egg yolk (mg KOH/g of fat) increased with the increasing dose, being conclusively higher only for doses of 2.5 kGy and 5 kGy.     

Textural modification of soya bean/corn extrudates as affected by moisture content, screw speed and soya bean concentration

A Clextral BP‐10 (type BC45) co‐rotating twin‐screw extruder was used for texture modification of extrudates. Dry materials were mixed in a mixer for 15 min at low speed before extrusion. Moisture content 21–23% and addition of soya bean flour (0–40%) showed significant influences on the texture of the extrudates. Addition of soya bean flour in the range from 0 to 40% increased the diametrical expansion ratio (P < 0.01), decreased the hardness (P < 0.01) and modifies specific volume and chewing behaviours of the extrudates. Increasing moisture content in the range from 21 to 23%, however, significantly decreased specific volume (P < 0.01), and increases hardness (P < 0.01) of the extrudates. The hardness and crispness of the extrudates at fracturability of 110 g were graded higher than 6.0 by 30 and 27 of 34 consumer panelists, respectively. Consumer purchase intent showed the highest score of 5.5 in a 9‐point hedonic scale when sample fracturability was at 110 g.     

Dose dependence and fading effect of the thermoluminescence signals in γ-irradiated paprika

The thermoluminescence (TL) method can be used to discriminate irradiated and non-irradiated paprika. This study reports the polymineral composition of the dust adhered to paprika; radiation-specific luminescence is emitted by the inorganic material (mainly quartz, feldspars and calcite). On the basis of the shape of the TL curves (or glow curves) some physical parameters are evaluated. Natural TL curves, from non-irradiated samples, show three very low intensity peaks while induced TL curves, from irradiated paprika, seem to consist of five overlapping peaks. TL spectra reveal a very important difference in intensity and in the position of the peaks between irradiated and non-irradiated paprika. Fading observations of TL after irradiation at 5, 10 and 21 kGy, show the same behaviour in all the cases: an initial rapid decay to maintain a certain stability from 300–400 h onwards. © 1998 SCI.     

Combined acid‐ and rennet‐induced gelation of a mixed soya milk–cow's milk system

The objective of this study was to better understand the gelation behaviour of a mixed soya milk–cow's milk system, by forming different reactive protein particles using rennet and glucono‐δ‐lactone. The formation of the structure of these mixed gels was followed, for the first time, using diffusing wave spectroscopy and rheology. When only one protein source was induced to gel, protein aggregation was hindered, as shown by the slower increase in apparent radius after the gel point. Confocal microscopy analysis of the gel networks suggested that while milk gels exhibited large pores with interconnecting strands of protein, soya gels appeared as densely packed protein aggregates, and mixed soya milk gels appeared as a network of aggregated proteins. This study demonstrated that by modulating the reactivity of the building blocks, it is possible to fine‐tune structure formation of these mixed protein gels.