The Development of β-Glucanase and Degradation of β-Glucan in Barley Grown in Scotland and Spain

The barley mutant TR49 and the cultivar from which it was derived, Troubadour, were grown in Scotland and Spain and harvested in 1991 and 1992. The development of β-glucanase together with the breakdown of β-glucan and the reduction in milling energy were followed during malting. While similar amounts of β-glucan were found in samples from both sites, TR49 showed less response to environmental conditions. Grain from Spain showed higher levels of β-glucanase activity, differences being apparent after steeping and 1–2 days of germination. The milling energy of grain was the same, but, during malting, samples from Spain showed a greater reduction in milling energy than those from Scotland. The most extreme environment in the study was the 1991 season at the Spanish site and was the driest and hottest. But even in the cooler, wetter season of 1992, Spanish grown material showed a greater production of β-glucanase than Scottish grown samples. These findings have important implications for plant breeding as well as the growing and trading of malting barley on a European scale.     

High (1→3,1→4)-β-Glucan Barley Fractions in Bread Making and their Effects on Human Glycemic Response

Barley flour (BF) from whole naked grain and two (1→3,1→4)-β-glucan-enriched fractions, a sieved fraction (SF) and a water-extracted fraction (WF), were produced and mixed with bread wheat flour (BW), for bread-making quality evaluation. Bread was baked in a pilot plant and analysed for sensory properties, proximate composition and (1→3,1→4)-β-glucan content. Four kinds of bread were produced from different mixtures of barley ingredients and bread wheat flour: a 100% BW ((1→3,1→4)-β-glucan content: total, 0·1%; soluble, 0·1%); a 50% BW and 50% BF (2·4%; 2·0%); a 50% BW and 50% SF (4·2%; 2·8%); an 80% BW and 20% WF (6·3%; 5·7%). Eight adults were fed test meals of each of the four breads, containing the same amount (50 g) of available carbohydrate, and glycemic indices calculated from finger-prick capillary blood samples. A linear decrease in glycemic index was found for increasing (1→3,1→4)-β-glucan content. The 20% WF bread had a 28% lower glycemic index than the plain BW and also showed the best scores for sensory attributes. This research confirms the effectiveness of viscous (1→3,1→4)-β-glucan in reducing postprandial blood glucose levels, even in foods with a high glycemic index. The enrichment technique, and water extraction/freeze-drying technique, could enable the use of barley as a source of a high-value fibre for reducing the glycemic index of traditional wheat-based foods such as bread, without negatively affecting their sensory characteristics.     

Effect of High β-Glucan Barley on Serum Cholesterol Concentrations and Visceral Fat Area in Japanese Men—A Randomized,Double-blinded,Placebo-controlled Trial

This study investigated whether the consumption of a diet in which high-β-glucan barley replaced rice would reduce the visceral fat area as well as the serum low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) in hypercholesterolemic Japanese men. A randomized, double-blinded, placebo-controlled intervention study was conducted in 44 hypercholesterolemic Japanese men with a body mass index (BMI) >22 kg/m². The subjects were randomly assigned to groups consuming either rice (placebo group) or a mixture of rice and pearl barley with a high β-glucan content (test group, 7.0 g β-glucan per day) for 12 weeks. Blood samples were taken, and CT scan obtained before the trial and every four weeks during the trial. The pearl barley intake significantly reduced serum concentrations of LDL-C (P = 0.041) and TC (P = 0.037) during the trial. Significant differences between the test and placebo groups were found for the visceral fat (P = 0.039), BMI (P = 0.015), and waist circumference (P = 0.011) at the end point. The consumption of pearl barley with a high β-glucan content reduces not only LDL-C but also visceral fat area.     

Reversed phase HPLC analysis of α- and β-carotene from selected raw and cooked vegetables

Traditional AOAC colorimetric procedures for carotenoid analysis are known to lack specificity and accuracy. Newer HPLC methods provide the investigator with a more precise tool for carotenoid quantification in foods and tissues. In the present studies, reverse phase HPLC was utilized to evaluate the - and -carotene content in raw and cooked leaves of lettuce, spinach and winged bean as well as in the carrot root. The vegetables were boiled or steamed and the true retention of - and -carotene in the cooked products was determined. Boiling for 30 minutes resulted in a 53 and 40% loss of -carotene from lettuce and carrots, respectively. Full retention or even an increase in -carotene content in boiled winged bean leaves and spinach was noted. Steaming resulted in very good retention of - and - carotene in all vegetables (83–139% retention). Thus, although cooking procedures (especially boiling) may result in oxidative loss of carotenoids in some vegetables, heat treatment increases the chemical extractability of - and -carotene in others. The presence of carotenoproteins in some vegetables may effect the heat stability of extractability of - and - carotene.     

Effect of β-glucans on viscoelastic properties of barley kernels and their relationship to structure and soluble dietary fibre

The stress relaxation behaviour of barley kernels with differences in β-glucan was studied using the generalized Maxwell model for explaining the differences in quality. The relaxation moduli show that cultivar significantly affected the relaxation times (τ₂ and τ₃) and compressional viscosity (η_E2 and η_E3) of the 3 Maxwell elements and the pure elastic component (E₀). These data were twice as high in cultivars with high β-glucans compared to low β-glucans. Protein and malt extract, as well as β-glucan, showed similar patterns to the corresponding cultivars from the same locations. Malt extract was correlated with both insoluble fibre (−0.71; P < 0.0007) and total fibre (−0.66; P < 0.006). High β-glucan cultivars presented relatively high soluble fibre, wort viscosity and presented higher relaxation times. Soluble fibre and the wort viscosity were correlated with relaxation times τ₁, τ₂, τ₃. Also, β-glucans were correlated with τ₃ and viscosity η_E3. The overall importance of the effect of β-glucans on viscoelasticity, malting and food quality as shown in this investigation is in agreement with earlier investigations.     

Effect of β-glucans on viscoelastic properties of barley kernels and their relationship to structure and soluble dietary fibre

The stress relaxation behaviour of barley kernels with differences in β-glucan was studied using the generalized Maxwell model for explaining the differences in quality. The relaxation moduli show that cultivar significantly affected the relaxation times (τ₂ and τ₃) and compressional viscosity (η_E2 and η_E3) of the 3 Maxwell elements and the pure elastic component (E₀). These data were twice as high in cultivars with high β-glucans compared to low β-glucans. Protein and malt extract, as well as β-glucan, showed similar patterns to the corresponding cultivars from the same locations. Malt extract was correlated with both insoluble fibre (−0.71; P < 0.0007) and total fibre (−0.66; P < 0.006). High β-glucan cultivars presented relatively high soluble fibre, wort viscosity and presented higher relaxation times. Soluble fibre and the wort viscosity were correlated with relaxation times τ₁, τ₂, τ₃. Also, β-glucans were correlated with τ₃ and viscosity η_E3. The overall importance of the effect of β-glucans on viscoelasticity, malting and food quality as shown in this investigation is in agreement with earlier investigations.     

Some Characteristics of β-D-Xylopyranosidases, α-L-Arabinofuranosidases and an Arabinoxylan α-L-arabinofuranohydrolase from Wheat Bran and Germinated Wheat

Enzymes from wheat bran and germinated wheat involved in the degradation of arabinoxylan and arabinoxylooligosaccharides were investigated. Fourp-nitrophenyl-α-l-arabinofuranoside hydrolysing activities (ArafI-IV) and threep-nitrophenyl-β-d-xylopyranoside hydrolysing activities (XylpI-III) were identified in wheat kernels and germinating wheat. Two of these activities, ArafI and XylpII, were purified about 10 000-fold from wheat bran. Both enzymes were inactive towards polymeric arabinoxylan. ArafI produced no arabinose but some xylose from arabinoxylooligosaccharides, while XylpII gave only xylose upon incubation with this substrate. An arabinoxylan arabinofuranohydrolase (AXH) was found in wheat bran and germinated wheat. This enzyme was active towards the polymeric substrate, but was unable to hydrolysep-nitrophenyl-α-l-arabinofuranoside. TheM_rs of these enzymes were determined by size exclusion chromatography and were in the range of 40–50 000, except for ArafIII, for which aM_rof 104 000 was determined. During germination, the levels of these enzymes increased markedly between the third and fifth day, after which some of them decreased again by the seventh day. ArafI-IV were inhibited strongly by arabinonic acid-γ-lactone, while xylonic acid-γ-lactone was a good inhibitor of XylpI-III. The latter lactone also inhibited ArafI. Neither of these lactones inhibited AXH. Endoxylanase activity was demonstrated but not quantified.     

In Vitro Accessibility and Intake of β-Carotene From Cooked Green Leafy Vegetables and Their Estimated Contribution to Vitamin A Requirements

Provitamin A carotenoids from green leafy vegetables constitute a major dietary source of vitamin A in Tanzania. The efficiency of different vegetable preparations in contributing to the daily safe intake level of vitamin A for children was evaluated in the present study. The amount of bioaccessible (available for absorption) all-trans--carotene from green leafy vegetable dishes prepared either traditionally in households or with an improved method was estimated by an in vitro digestion method that simulates human digestion. The median vegetable portion size consumed by 34 children (2--12 years old) in the surveyed households was determined by weighing. The amount of all-trans--carotene available for absorption from the same type of vegetables cooked without oil by traditional or a modified method ranged from 5 to 12% and 4 to 15%, respectively. Vegetables cooked with modified method with oil had 2–5 times higher amount of in vitro accessible all-trans--carotene than vegetables cooked without oil. A median portion (84 g) of such a relish then provided 88–477% of the daily safe intake level of vitamin A, while portions cooked without oil only provided between 23 and 46%. In this study, a wide variation in all-trans--carotene content and bioaccessibility among studied green leaves was obtained. Still, to supply daily safe intake level of vitamin A for children from a median vegetable relish portion it is necessary to add oil in the preparation.     

Bioavailability trials of β-carotene from fresh and dehydrated drumstick leaves (Moringa oleifera) in a rat model

Male albino rats (Charles Foster, n = 40) were fed a synthetic diet deficient in vitamin A for 4 weeks. Six rats died during the depletion period. Of the 34 surviving, 5 rats were continued on the vitamin A deficient diet for 4 more weeks and 24 were repleted with vitamin A (4000 IU/kg diet) in the form of vitamin A acetate (group A, n = 8), fresh drumstick leaves (group B, n = 8) or dehydrated drumstick leaves (group C, n = 8) for 4 weeks. The remaining 10 rats were continued on the vitamin A adequate diet for 4 (n = 5) and 8 weeks, respectively (n = 5). A marked reduction in food intake, body weight, accompanied by clinical signs of vitamin A deficiency and a decline in serum vitamin A (29.2 to 19.1 g/dL) and liver vitamin A (3.7 to 2.0 g/dL) were seen at the end of 4 weeks of feeding a vitamin A deficient diet. On repletion significant improvements in clinical signs, food intake and body weights were noted in the three groups compared to the baseline (n = 5) and at the end of 4 weeks of depletion. The gain in body weight was highest for the group repleted with dehydrated drumstick leaves. Among the repleted groups, the serum vitamin A was highest for group A (34.7 g/dL) given synthetic vitamin A, compared to group B (25.8 g/dL) and group C (28.2 g/dL) given drumstick leaves. All these were significantly higher than the serum vitamin A values seen at the end of 4 weeks of depletion (19.1 g/dL). A significant improvement was also observed in the liver retinol levels on repletion for 4 weeks in the three groups, compared to the vitamin A depleted rats. These results imply that -carotene from drumstick leaves was effective in overcoming vitamin A deficiency although serum vitamin A levels remained somewhat lower compared to the group repleted with vitamin A acetate. In terms of growth parameters, the fresh and dehydrated drumstick leaves were better than the synthetic vitamin A. It is therefore concluded that in the developing countries like India, sources of vitamin A such as drumstick leaves are valuable in overcoming the problem of vitamin A deficiency.     

In vitro protein digestibility of developing and mature sorghum grain in relation to α-, β-, and γ-kafirin disulfide crosslinking

Sorghum (P721N, 1992) was harvested at selected days after half-bloom (DAHB) and at maturity, and analyzed for protein and moisture contents, protein digestibility, α-, β-, and γ-kafirin contents, and unextractable disulfide-bound complexes. α-Kafirin synthesis began before 10 DAHB, and β- and γ-kafirin at 20 DAHB. All the kafirins were as abundant at 40 DAHB as at maturity. Protein digestibilities of uncooked flour were about 90%, and dropped to 73% at maturity. Digestibilities of cooked flour dropped markedly at 35 DAHB, 40 DAHB and maturity. A comparison of 1992 and 1987 data indicates that digestibility decreases with moisture content, not days of development. The amount of disulfide “crosslinked” β- and γ-kafirins was insignificant at the earlier stages, though increased as the grain matured. Since kafirin synthesis is complete by 40 DAHB, we suggest that the decrease in digestibility in maturing grain is due to the drying effect and formation of disulfide-bound complexes involving β- and γ-kafirins. Cooking the flour may further promote protein interactions, particularly after kafirin synthesis has ceased.     

Overexpression and Characterization of a Novel Thermostable β-Agarase YM01-3, from Marine Bacterium Catenovulum agarivorans YM01T

Genome sequencing of Catenovulum agarivorans YM01^T reveals 15 open-reading frames (ORFs) encoding various agarases. In this study, extracellular proteins of YM01^T were precipitated by ammonium sulfate and separated by one-dimensional gel electrophoresis. The results of in-gel agarase activity assay and mass spectrometry analysis revealed that the protein, YM01-3, was an agarase with the most evident agarolytic activity. Agarase YM01-3, encoded by the YM01-3 gene, consisted of 420 amino acids with a calculated molecular mass of 46.9 kDa and contained a glycoside hydrolase family 16 β-agarase module followed by a RICIN superfamily in the C-terminal region. The YM01-3 gene was cloned and expressed in Escherichia coli. The recombinant agarase, YM01-3, showed optimum activity at pH 6.0 and 60 °C and had a K_m of 3.78 mg mL⁻¹ for agarose and a V_max of 1.14 × 10⁴ U mg⁻¹. YM01-3 hydrolyzed the β-1,4-glycosidic linkages of agarose, yielding neoagarotetraose and neoagarohexaose as the main products. Notably, YM01-3 was stable below 50 °C and retained 13% activity after incubation at 80 °C for 1 h, characteristics much different from other agarases. The present study highlights a thermostable agarase with great potential application value in industrial production.     

pH-, Temperature- and Time-dependent Activities of Endogenous Endo-β-D-Xylanase, β-D-Xylosidase and α-L-Arabinofuranosidase in Extracts from Ungerminated Rye (Secale cereale L.) Grain

Activities of endogenous β-D-xylosidase (EC.3.2.1.37), α-L-arabinofuranosidase (EC. 3.2.1.55) and endo-β-D-xylanase (EC.3.2.1.8) were quantified in extracts from ungerminated rye (Secale cereale Lvar. Amando) grain. pH- and temperature optimum and stability of the unpurified enzymes were examined. The activity of β-xylosidase and α-arabinofuranosidase against p-nitrophenyl-glycosides was 180 and 346 pkatal/g grain, respectively (pH 4·5; 30 °C) and that of the endo-xylanase against RBB-xylan was 11 pkatal/g grain (pH 4·5; 40 °C). The pH optimum of each of the enzymes was 4·5, which is similar to the pH of a rye dough. The temperature optima for the enzymes were 40 °C (endo-xylanase), 70 °C (β-xylosidase) and 60 °C (α-arabinofuranosidase), respectively. Sodium chloride (0·5–3·0%, w/v) had no effect on enzyme activities. The enzymes were relatively stable at pH 4·5 and room temperature for at least 24 h. The enzymes showed no significant decrease in activity when extracts were incubated at pH 4·5 and 30–40 °C for 80–120 min. Incubation at temperatures higher than 40 °C resulted in a significant decrease in activity. The rate of hydrolysis of the respective p -nitrophenyl glycosides and RBB-xylan was high under conditions typical for the rye dough production stages but decreased at temperatures typically encountered in the baking process.     

Stress–Relaxation Properties of Mixograph Semolina–Water Doughs from Durum Wheat Cultivars of Variable Strength in Relation to Mixing Characteristics,Bread- and Pasta-making Performance

Stress–relaxation behaviours of Mixograph semolina–water doughs prepared from Canadian durum wheat cultivars with diverse gluten strength were investigated and related to mixing characteristics, large deformation properties, and bread- and pasta-making quality. Semolina from «strong» (S) and «moderately strong» (MS) durum wheat cultivars required a longer Mixograph mixing time (4–5 min) and higher work input (140–196 Arbitrary Units) to mix to peak dough resistance (PDR) than «weak» (W) and «very weak» (VW) durum cultivars (2–3 min and 80–117 AU). Extensigraph maximum resistance to extension (R_max/E ratio) and Alveograph P/L (tenacity to length ratio) values were higher for doughs from S cultivars than for MS, W, and VW cultivars. Doughs from S cultivars exhibited higher storage modulus (G′) and lower tan δ values at all frequencies, and slower rates of stress relaxation as compared to MS, W, and VW cultivars. Stress relaxation (times to relax 50% (t₅₀) and 75% (t₇₅) of initial stress) indicated that stronger doughs, which had higher proportions of glutenins, took longer to reach these iso-relaxation states, regardless of their initial relaxation modulus value. The parameters t₅₀and t₇₅were also strongly correlated with dough mixing properties, Extensigraph R_max/E, Alveograph P/L, mixing energy, mixing time and loaf volume obtained by a long and a short bread-making process. However, for S cultivars loaf volume was 10 to 20% lower than that expected of bread wheat of comparable protein content. Stress relaxation data demonstrated no simple correlation to pasta cooking quality indicating that stronger gluten did not translate into a superior pasta cooking quality. Results are interpreted in the context of multimodal networks and transient networks with reversible crosslinks.     

Susceptibility to Insecticides and Ecological Fitness in Resistant Rice Varieties of Field Nilaparvata lugens Stl Population Free from Insecticides in Laboratory

A population of rice brown planthopper(BPH) Nilaparvata lugens collected from a paddy field in Hangzhou was successively reared on susceptible rice Taichung Native 1(TN1) in a laboratory free from insecticides for more than 14 generations. The changes in susceptibility to insecticides and ecological fitness on different resistant rice varieties were monitored in each generation. The resistance ratio to imidacloprid sharply declined with the succession of rearing generations without insecticides from 359.94-fold at F1 to 6.50-fold at F14 compared with the susceptible strain, and the resistance ratio to chlorpyrifos was from 9.90-fold at F1 to 5.94-fold at F14. Nymphal duration and weights of newly hatched female adults were significantly affected by rice variety, generation and their interactions, but nymphal survival was significantly affected by the generation only. The ratio of brachypterous adults in males was affected by the generation and generation × variety interaction, whereas no difference was found in females. Nymphal duration extended with increasing generations, and the female nymphal duration was shorter in the susceptible variety TN1 than those in the resistant varieties IR26 and IR36. In addition, the female adult weight in TN1 was higher than those in IR26 and IR36. These results indicated that the resistance of field BPH population to insecticides was reversed after several generations of no-exposure to insecticides, and the ecological fitness in TN1 was higher than those in IR26 and IR36. These findings suggested the rational and reduced use of insecticides in combination with the manipulation of resistant rice varieties would be effective for BPH management.