Characterisation of lipoxygenase from pea seeds (Pisum sativum var. Telephone L.)

Lipoxygenase (LOX) from pea seeds (Pisum sativum var. Telephone L.) was extracted and studied of biochemical properties. The molecular mass of purified lipoxygenase was 93 kDa. The effects of substrate specificity, pH, and sensibility to various inhibitors: caffeic acid, ferulic acid, benzoic acid, catechin, quercetin and kaempferol of LOX were investigated. Lipoxygenase showed the highest activity toward linoleic acid and the lowest toward oleic acid as substrates. Kinetic studies indicated that V_max of the LOX activity was 151.5 U/min and corresponding K_m value of 0.44 × 10⁻³ M. Optimum pH of lipoxygenase was reported at 5.5. Caffeic acid was the most effective inhibitor and kaempferol was the least effective.     

Applicability of DATEM for Chinese steamed bread made from flours of different gluten qualities

BACKGROUD: The diacetyl tartaric acid ester of monoglycerides (DATEM) is an anionic oil‐in‐water emulsifier. The effects of DATEM on bread vary with the type of flour. However, there is insufficient information concerning the effects of DATEM on the qualities of Chinese steamed bread (CSB) even though it is also sold as a CSB improver. RESULTS: The effects of DATEM on CSB varied with flours. The overall qualities of CSB made from either weak or strong wheat flours were improved by the use of the additive, but the effects for medium strong flours were slight and uncertain. The effects of DATEM on individual parameters, such as specific volume, skin and inner structure, were similar to those on overall quality. The addition of DATEM increased the gluten strength and the dough stability of weak flour, whereas it weakened gluten strength and strengthened dough stability of strong flour. The addition of DATEM weakened the gluten strength and gave variable effects on dough stabilities for two medium strong flours. CONCLUSION: The effects of DATEM on CSB quality varied with flour type, by affecting flour characteristics, such as gluten strength, dough stability and lipid content. Copyright © 2008 Society of Chemical Industry     

Development of Chinese steamed bread enriched in bioactive compounds from barley hull and flaxseed hull extracts

Hull from cereal and oilseed grains represent low-cost agricultural materials that have not be fully explored as functional food ingredients. The objectives of the present study were to investigate the phytochemical profile and antioxidant activity of Chinese steamed bread (CSB) containing extracts of barley hull and flaxseed hull. HPLC and LC–MS/MS analyses showed that the phytochemical profile of CSB containing barley hull extract was enriched in ferulic and p-coumaric acids. The flaxseed hull extract introduced secoisolariciresinol diglucoside (SDG), ferulic acid glucoside (FeAG) and coumaric acid glucoside (CouAG) into CSB. All the major phenolic compounds originating from the two types of hulls were found in CSB when barley–flaxseed hull co-extracts were added to the formulation. The total phenolic content was improved by 83.1, 138.3 and 70.3%, respectively when barley, flaxseed, and barley–flaxseed hull extracts were added. The antioxidant activity of CSB containing hull extracts was increased by 34.5–90.7% compared to the control. CSB containing hull extracts had significantly higher (p < 0.05) DPPH radical scavenging activity compared to the control. However, barley–flaxseed hull co-extracts resulted in the highest enhancement of ORAC values of the CSB, although no significant differences were found (p < 0.05). The findings indicate that extracts from barley hull, flaxseed hull and barley–flaxseed can be targeted for development as functional food ingredients that can enhance the phytochemical content of refined flour products, such as steamed bread.     

Effect of endoxylanases on dough properties and making performance of Chinese steamed bread

Two kinds of endoxylanase (XYL), one is a solid-phase enzyme (S-XYL) and the other a liquid-phase enzyme (L-XYL), were used to test their effect on the properties of dough and the quality of Chinese steamed bread (CSB). The textural properties of wheat dough made with the two enzymes were investigated. Parameters from the texture profile analysis (TPA) were determined after mixing the dough at 0th, 5th, 10th, 15th and 20th min, respectively. Both enzymes decreased farinograph parameters. They also influenced mixograms including decreasing time to peak and peak height. It was apparent that the decrease in hardness of the dough by adding S-XYL and L-XYL, respectively was more than that of the control sample and the sample with added yeast. It was found that the longer the time of fermentation, the lower the hardness of the dough. The mixing time was reduced by adding L-XYL by about 27.5%. The fermentation time was decreased by adding S-XYL or L-XYL. The addition of S-XYL and L-XYL on CSB resulted in increased specific volume, spread ratio and decreased crumb softness. A decreasing trend in L* value, a slightly increasing tendency in a* value and a slightly decreasing trend in b* value exist in crumb colour.     

Characteristics of wheat dough and Chinese steamed bread added with sodium alginates or konjac glucomannan

In this study, wheat flour was dry-blended with sodium alginates (ALG) and konjac glucomannan (KGM) at 0.2% and 0.8% w/w flour as-is moisture basis. Dough mixing and stretching properties were assessed by farinograph and extensograph, respectively. Chinese steamed bread (CSB) samples prepared were compared in terms of spread ratio, specific volume and staling behaviour. In general, ALG and KGM addition was found to produce dough with rigid and weak network, respectively. Chinese steamed bread with ALG (0.2%) or KGM (0.8%) addition was relatively low in spread ratio and specific volume, but softer and more resistant to staling on storage as compared to the control sample.     

Cloning of a thermostable xylanase from Actinomadura sp. S14 and its expression in Escherichia coli and Pichia pastoris

A thermophilic xylan-degrading Actinomadura sp. S14 was isolated from compost in Thailand. Hemicellulase activities such as endo-1,4-β-xylanase, β-xylosidase and α-arabinofuranosidase were induced with xylan-containing agriculture wastes and oat spelt xylan. The gene encoding xylanase consisting of 687bp was cloned from Actinomadura sp. S14. The deduced amino acid sequence contained a signal peptide of 41 amino acids and a probable mature xylanase of 188 amino acids. An open reading frame (xynS14) corresponding to a mature xylanase was expressed in Escherichia coli and Pichia pastoris. The specific activity of purified XynS14 (P. pastoris) was 2.4-fold higher than XynS14 (E. coli). Both XynS14s showed the same basic properties such as optimal pH and temperature (pH 6.0 and 80°C) and stability in a broad pH range (pH 5.0-11.0) and at high temperatures up to 80°C. Both XynS14s showed approximately the same substrate specificity and K(m) values toward various xylans, but XynS14 (P. pastoris) showed higher V(max) and K(cat) than XynS14 (E. coli). Higher specific activities of XynS14 (P. pastoris) may be due to protein-folding in the host. Purified XynS14 showed more endo-1,4-β-xylanase activity on xylan and xylooligosaccharides than on xylotriose.     

Characterisation of trypsin purified from the viscera of Tunisian barbel (Barbus callensis) and its application for recovery of carotenoproteins from shrimp wastes

Trypsin was purified from the viscera of barbel by precipitation using ammonium sulphate (0-80%), Sephadex G-100, and Mono Q-Sepharose ion exchange chromatography. The trypsin was purified 27-fold, with 79 U/mg specific activity and 31% recovery. The enzyme had a molecular weight of 24 kDa; purified trypsin appeared as a single band on native-PAGE. The optimum pH and temperature for enzyme activity were pH 10.0 and 55 °C with BAPNA used as a substrate. The N-terminal amino acid sequence of the first 12 amino acids of the purified trypsin was IVGGYECTPYSQ. The Michaelis-Menten constant (K_m) and catalytic constant (k_cat) values of the enzyme were 0.018 mM and 1.21 s⁻¹, respectively. The study also investigated the effects of purified trypsin on the recovery of carotenoproteins from shrimp (Parapenaeus longirostris) shells through hydrolysis using 1.0 U barbel trypsin/g shrimp shells for 1 h at 30 °C. The freeze-dried carotenoproteins recovered contained 71.09% protein, 16.47% lipid, 7.78% ash, and 1.79% chitin.     

Effects of hydrothermal processing on rutin retention and physicochemical properties of Tartary buckwheat enriched dough and Chinese steamed bread

Effects of hydrothermal processing on content changes of rutin, quercetin and total flavonoids and physicochemical properties of Tartary buckwheat (TB) enriched dough and Chinese steamed bread (CSB) were investigated. Rutin loss and bitterness in CSB made from mixed wheat flour and hydrothermally processed TB flour decreased markedly compared with control. Total flavonoids were increased in dough after fermentation but decreased afterwards in CSB significantly (P < 0.05). The development time, stability time, extensibility, storage and loss moduli and tan δ of TB enriched dough, along with the volume, textural properties, sensory evaluation and bitterness of derived CSB, were significantly affected by hydrothermal processing temperature and time. Hydrothermal processing of TB flour at 100 °C for 20 min, compared with 100 °C for 10 min, 30 min or 121 °C for 10 min, 20 min, 30 min, was suggested to be a relatively better pretreatment condition for the present TB enriched CSB.     

Purification and characterization of a novel thermostable phytase from the thermophilic Geobacillus sp. TF16

A novel phytase from thermophilic Geobacillus sp. TF16 was puri?ed approximately 5-fold using ammonium sulfate precipitation and ion exchange chromatography, and determined as a single band 106.04 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Optimum temperature and optimum pH were found to be 85°C and 4.0, respectively. The enzyme is highly thermostable and V_max and K_m values were calculated as 526.28 U/mg and 1.31 mM, respectively. It was also found that the enzyme exhibited a broad substrate selectivity and resistance toward proteases and effectively hydrolyzed soymilk phytate. These results suggest that this study provides an alternative phytase enzyme with enhanced properties.     

Characterisation of esterolytic activity from two wild mushroom species, Amanita vaginata var. vaginata and Tricholoma terreum

Characterisation of esterase activities from the edible mushroom species, Amanita vaginata var. vaginata and Tricholoma terreum, were investigated. Native electrophoresis of the crude extracts prepared from both mushroom samples showed the presence of esterolytic activities. The extracts had the greatest activity in the presence of p-nitrophenyl butyrate (pNPB) as a substrate. pH and temperature optima were found to be 8.0 and 30 °C for both enzymes, respectively. V_max and K_m values were determined as 14.2 U/l and 71 μM for A. vaginata var. vaginata and 34.6 U/l and 9.6 μM for T. terreum, respectively. The pH-stability profile showed a stationary line between 3.0 and 10.0 for both enzymes. The esterolytic activities from the extracts were maintained between 10 and 40 °C for 4 h and started to decrease at 50 °C. The effects of EDTA, NaN₃, DTT and PMSF on the enzyme activity were also investigated.     

微细化麦麸膳食纤维制备及其对面制品品质影响

该文报道以麦麸为原料制备膳食纤维工艺,确定最佳技术条件并制备微细化麦麸膳食纤维;且在面粉中分别添加5%、8%、10%、12%和15%麦麸膳食纤维配制膳食纤维面粉。按我国传统工艺技术制备不同麦麸膳食纤维添加量的馒头和中式面条样品,并据行业标准分别进行品质评价;结果表明,添加麦麸膳食纤维使馒头体积及感官指标评价得分均呈下降趋势,当其添加量为8%时,馒头总体品质评价得分高于80%;麦麸膳食纤维添加量不超过5%的麦麸膳食纤维面条,其感官品质指标与空白样面条接近,都可被市场所接受。     

Application of Kluyveromyces marxianus, Lactobacillus delbrueckii ssp. bulgaricus and L. helveticus for sourdough bread making

The application of Kluyveromyces marxianus (IFO 288), Lactobacillus delbrueckii ssp. bulgaricus (ATCC 11842) and Lactobacillus helveticus (ATCC 15009) as starter cultures for sourdough bread making was examined. Production of lactic and acetic acids, bread rising, volatile composition, shelf-life and organoleptic quality of the sourdough breads were evaluated. The amount of starter culture added to the flour, the dough fermentation temperature and the amount of sourdough used were examined in order to optimise the bread making process. The use of mixed cultures led to higher total titratable acidities and lactic acid concentrations compared to traditionally made breads. Highest acidity (3.41 g lactic acid/kg of bread) and highest resistance to mould spoilage were observed when bread was made using 50% sourdough containing 1% K. marxianus and 4% L. delbrueckii ssp. bulgaricus. The use of these cultures also improved the aroma of sourdough breads, as shown by sensory evaluations and as revealed by GC–MS analysis.     

Freeze drying technique for microencapsulation of Garcinia fruit extract and its effect on bread quality

Microencapsulation is an enduring technology for protection and controlled release of food ingredients. The Garcinia cowa fruit rinds are rich source of (−)-hydroxycitric acid (HCA), which is reported to have various health benefits. But, HCA is hygroscopic in nature and thermally sensitive. Hence, G. cowa fruit extract was microencapsulated using three different wall materials such as whey protein isolate (WPI), maltodextrin (MD) and combination of whey protein isolate and maltodextrin (WPI + MD in 1:1 ratio) by freeze drying at 30% concentration. The microencapsulated powders were evaluated for their impact on bread quality and free HCA concentration. The microcapsules exhibited wider particle size range of 15–100 μm and HPLC analysis showed that all the three encapsulates yielded higher free (above 85%) and net (above 90%) HCA recovery. Moreover, bread with WPI encapsulates exhibited higher volume, softer crumb texture, desirable colour and sensory attributes and had higher free HCA concentration. This indicated that WPI has excellent encapsulation efficiency than other two wall materials during bread baking.     

Purification and characterisation of exo- and endo-inulinase from Aspergillus ficuum JNSP5-06

Three exoinulinases (Exo-I, Exo-II, and Exo-III) and two endoinulinases (Endo-I and Endo-II) were purified from the culture broth of Aspergillus ficuum JNSP5-06 by ammonium sulphate precipitation, DEAE-cellulose column chromatography, Sepharose CL-6B column chromatography and preparative electrophoresis. The molecular weights of Exo-I, Exo-II, Exo-III, Endo-I, and Endo-II were determined to be 70 kDa, 40 kDa, 46 kDa, 34 kDa, and 31 kDa, respectively. Using inulin as the substrate, their K_m values were 43.1 mg/ml, 31.5 mg/ml, 25.3 mg/ml, 14.8 mg/ml, and 25.6 mg/ml, respectively. These five inulinases were stable below 50 °C with optimum activity at 45 °C, and were stable at a pH range of 4–8 with an optimum pH at 4.5 for exoinulinase and at 5.0 for endoinulinase. The inulinase activity was completely inhibited by Ag⁺ and strongly inhibited by Fe²⁺ and Al³⁺, whereas K⁺, Ca²⁺, Li²⁺, EDTA and urea had no significant influence on the inulinase activity.     

Partial purification and characterisation of endoglucanase from an edible mushroom, Lepista flaccida

A crude extract was prepared from the fruiting body of Lepista flaccida, an edible mushroom and endoglucanase activity of the extract was increased 14-fold with ammonium sulphate precipitation. Maximum enzyme activity was seen at pH 4.0 and 50 °C when carboxymethylcellulose was used as a substrate. K_0.5 and V_max values of the partially purified endoglucanase were 7.7 mg/ml and 25 ± 0.9 U/mg protein, respectively. The enzyme was quite stable over a broad range of pH (2.0–9.0) at 4 °C. When it was incubated at temperatures between 20 °C and 60 °C for 12 h, it conserved much of its original activity (over 40%). The activity of the enzyme increased by 234 ± 3.6% in the presence of 1 mM Mn²⁺. The endoglucanase was inhibited by EDTA, PMSF, β-ME and DDT. In conclusion, pH and thermal stability of the L. flaccida endoglucanase could make it useful for industrial purposes.     

Fatty acid profiles of vegetable oils from four different plant sources and their effects on dough rheology and Chinese steamed bread quality

Fatty acids (FAs) of soya bean oil (SO), corn oil (CO), peanut oil (PO), and rapeseed oil (RO) and their effects on dough rheology and Chinese steamed bread (CSB) quality were elucidated. PO, containing the most appropriate proportions of saturated (12.73%) and unsaturated (87.27%) FAs, had the most positive effects, conferring dough with an optimal viscosity and elasticity ratio, springiness, and recovery capacity. Concomitantly, the resultant CSB exhibited a nearly 15% larger specific volume, 33% softer texture, 5% lower mean cell area, 104% higher cell density, and 91% enhanced cell-to-total area ratio than control bread with commercial shortening. Furthermore, PO contained an optimal ω-6/ω-3 essential FA ratio of 6.28 for health benefits. For these reasons, PO could serve as a potential improver for CSB production to replace commercial shortening and compensate for essential nutrient deficiencies.