EFFECTS OF GLUCOSE OXIDASE, HEMICELLULASE AND ASCORBIC ACID ON DOUGH AND BREAD QUALITY

ABSTRACT

In this study, glucose oxidase alone or its combinations with hemicellulase or ascorbic acid were used in bread making. Glucose oxidase alone mainly decreased dough extensibility. It produced stiffer and less extensible dough. Combinations of glucose oxidase–hemicellulase presented lower extensibility and were more resistant to extension than glucose oxidase alone. When glucose oxidase–ascorbic acid combinations were used, the softening degree significantly decreased, regardless when added the lowest glucose oxidase in combination with ascorbic acid. Glucose oxidase–ascorbic acid combinations significantly modified dough resistance. The glucose oxidase alone significantly increased specific loaf volume. The Dallman value of loaves made with glucose oxidase alone was found higher than for control. The most dramatic effect of additives on specific loaf volume was observed when glucose oxidase–hemicellulase combinations were added. This effect has been ascribed to redistribution of water from the hemicellulose to gluten, which would render the gluten more extensible. Specific loaf volume showed a significant enhancement when glucose oxidase–ascorbic acid combinations were added, but this effect was not as good as glucose oxidase–hemicellulase. The effects of glucose oxidase and its combinations with ascorbic acid and hemicellulase on dough rheology and bread quality are highly dependent on the amount of enzyme and the original wheat flour quality.

PRACTICAL APPLICATION

In practice, appropriate combinations of glucose oxidase with hemicellulase can be used as improvers in bread making, depending on their combination levels. This study will show the way to new research about glucose oxidase, ascorbic acid and hemicellulose.

     

PITCHING RATES RELATED TO GLUCOSE AND FRUCTOSE UTILIZATION IN Saccharomyces cerevisiae

Pitching rates, in the range 1.5 g/litre to 24 g/litre of yeast in high gravity sucrose adjunct laboratory-scale wort fermentations, are directly proportional to the natural logarithm of glucose utilization throughout fermentation, whereas this relationship only holds for fructose utilization during the intermediate phases. The natural logarithmic rate of fructose utilization in the latter stages of fermentation remains constant irrespective of the pitching rate used. Adjustment of the pitching rate allows residual fructose concentrations at the end of fermentation to be regulated such that they remain below the fructose taste threshold in beer. The difference in utilization rates produced by the preferential utilization of glucose over fructose appears to remain constant irrespective of the pitching rate used. This differential may be ascribed to the competitive inhibition of fructose transport by glucose for their common hexose constitutive facilitated diffusion membrane transport system in S. cerevisiae.     

DIRECT ENZYMATIC CONVERSION OF LACTOSE TO ACID: GLUCOSE OXIDASE AND HEXOSE OXIDASE

The conversion of lactose directly to an acid by glucose oxidase and hexose oxidase as a method of milk acidification was studied. Under the appropriate conditions, both enzymes demonstrated the capability to catalyze the conversion of sugar in milk to an acid, producing coagulation. A uniform distribution of oxygen under quiescent conditions was essential for the reaction and could be accomplished with the addition of hydrogen peroxide in the presence of catalase. Commercial samples of glucose oxidase caused a gradual decrease in pH of skim milk containing added glucose or lactase, (beta-galactosidase). Hexose oxidase, which can react with galactose and lactose as well as glucose, produced acid at a very slow rate in skim milk alone. When lactase was incorporated into the milk, the rate of reaction increased significantly.     

耐高糖面包酵母的研究

实验表明 ,蔗糖酶活力低的菌株 ,在高糖面团中发酵力较好 ;而麦芽糖适应性好的菌株 ,在无糖面团中起发速度较快。从 12株原始菌株中选出蔗糖酶活力最低 ,且麦芽糖适应性较好的BY 6菌进行DES诱变 ,以葡萄糖氧化酶 辣根过氧化物酶 邻联茴香胺偶联反应平板作为初筛平板 ,经蔗糖酶活力复筛得到 4株酶活力降低了的突变株。其中M 2 6菌蔗糖酶活力降低幅度最大 ,比BY 6菌降低了 2 7 0 4 % ,且麦芽糖适应性有所提高。经测定 ,4株突变株的发酵性能良好     

TRIALS ON THE ANTIBACTERIAL EFFECT OF GLUCOSE OXIDASE ON CHICKEN BREAST SKIN AND MUSCLE

Use of glucose oxidase as a possible means to inhibit microbial growth on processed poultry was evaluated. Muscle and skin sections of chicken breast were inoculated with Pseudomonas spp. or Salmonella typhimurium and subjected to either: (1) 60 s dip in 2 units of glucose oxidase without glucose supplementation or (2) 60 s dip in 2 units of glucose oxidase with 4% glucose supplementation. Control groups were dipped in sterilized, distilled water. The Pseudomonas and Salmonella populations were determined for each section. Neither enzyme treatment reduced the initial Pseudomonas or Salmonella populations nor did the treatments inhibit the growth of Pseudomonas during the storage period . Salmonella was inhibited by the low temperature. Therefore, a glucose oxidase enzyme treatment has little potential for extending the shelf-life of chicken .     

基于纳米酶技术检测柑桔果实中葡萄糖

目的建立纳米酶检测体系快速检测葡萄糖含量的技术。方法采用甲烷氧化细菌的发酵代谢产物甲烷氧化菌素(methanobactin,MB)与Cu²⁺、纳米金(AuNPs)、葡萄糖氧化酶(glucose oxidase,Gox)进行配位结合形成具有过氧化物酶和葡萄糖氧化酶性质的纳米酶检测体系,并对柑桔果实中葡萄糖含量进行测定。结果Gox浓度0.81 U/mL、MB-Cu@AuNPs模拟酶浓度2×10^-5mol/L、对苯二酚浓度5×10^-4mol/L、反应温度60℃、pH 8为最佳检测条件;反应时间5 min,葡萄糖浓度线性范围为1×10^-3-5×10^-2mol/L。结论纳米酶检测体系对柑桔果实中葡萄糖含量的测定具有良好的稳定性,相比较常规快速血糖仪检测速度更快。     

Biosensors fob food industry

Novel biosensor systems were constructed for food industry. In order to determine fish freshness, a multifunctional enzyme sensor system was developed by combining a double membrane consisting of a 5'‐nucleotidase membrane and a nucleoside phosphorylase‐xanthine oxidase membrane with an oxygen electrode. Each nucleotide concentration was determined as the current decreased. One assay was completed within 20 min. Good comparative results were observed between the KI values determined by the sensor proposed and by the conventional method. An enzyme sensor for meat freshness consisted of a monoamine oxidase‐collagen membrane and an oxygen electrode. The response time of the electrode was 4 min. A linear relationship was observed between the amine (tyramine) concentration in the range 50–200 μM and the difference in current. Monoamine in meat extract was determined by the enzyme sensor. Micro‐glutamate sensor was constructed using silicon fabrication technology. Calibration curve for glutamate sensor was obtained in a glutamate concentration range between 5–50 mM. Moreover, an immuno sensor based on piezoelectric crystal was applied to the determination of toxic bacterium C. albicans. The frequency shift is correlated with C. albicans concentration in the range 10⁶ 5×10⁸ cell/ml.     

Ascorbate oxidase from starfruit (Averrhoa carambola): preparation and its application in the determination of ascorbic acid from fruit juices

A study was conducted to utilize ascorbate oxidase (AAO) from very immature starfruit for the enzymatic determination of ascorbic acid (AsA) in colored samples. The enzyme preparation was carried out by a combination of (NH₄)₂SO₄ fractionation, DEAE-Toyopearl 650 M and ultrafiltration. A calibration curve for AsA was constructed by plotting the amount of AsA oxidized by the enzyme at a specified reaction time against the absorbance. The curve showed a linear relationship in the range of 0–100 μg ml⁻¹ AsA used. Using the plot, the values of AsA in juice samples were determined and compared with the conventional 2,6-dichloroindophenol method.     

UPTAKE AND TURNOVER OF 14C GLUCOSE BY YEAST DURING WORT FERMENTATIONS

The incorporation of randomly labelled ¹⁴C glucose, or substances derived from it, into various cell components was followed during a brewery type fermentation, using a yeast polysaccharide fractionation technique in conjunction with liquid scintillation. The labelled glucose, when added to wort, was assimilated by brewer's yeast, most of it being fermented to ¹⁴C ethanol. A small but significant amount of the ¹⁴C glucose, or its metabolites, was incorporated into the polysaccharide fractions of the yeast. Employment of a simple “swop-over” technique has shown that in two of these fractions, the low molecular weight acid-soluble material and the mannan, there was a substantial turnover, reflecting respectively the transient metabolic status of the former and the special role of mannan in the structure of the outer layer of the cell wall. Glucan, as would be expected from its function as the principal structural component of the cell wall complex, was completely stable. Glycogen was also stable, and showed no evidence of turnover, even during the later stages of the fermentation. Hence it is unlikely that it could function as an energy reserve in this strain (N.C.Y.C. 240) during primary fermentation of brewer's wort.     

The effect of pretreatment on the fermentation of honeybush tea (Cyclopia maculata)

Different pretreatments (bruising, hot and cold water) were used to study their effect on fermentation as measured by the quality parameters of honeybush tea (Cyclopia maculata). Bruising and pretreatment with water (hot and cold) were investigated as means to increase the fermentation rate and to improve product quality. The development of the desired dark-brown colour and honey-like flavour during fermentation was faster in hot and cold water treated material and gave a more uniform coloured product than with the bruising pretreatment. Liquor characteristics also improved with water pretreatment. A red–brown extract, compared with the light yellow–brown of untreated samples, was obtained with the water pretreatment. Hot water pretreatment inactivated the enzymes polyphenol oxidase (PPO) and peroxidase (POD), but did not terminate or impair fermentation. The inactivation of the enzymes, together with high temperature (>60°C) fermentation, indicated a chemical oxidation process rather than an enzymatic reaction in honeybush tea fermentation. © 1998 SCI.     

Determination of Glucose in Food by the Ionic Liquid and Carbon Nanotubes Modified Dual-Enzymatic Sensors

A sensitive electrochemical glucose biosensor based on chitosan (CS)/glucose oxidase (GOx)/catalase (CAT)/CS?+?carboxylic multi-walled carbon nanotubes (MWCNTs-COOH)?+?ionic liquid (IL) film modified glassy carbon electrode has been developed and its characteristics were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Hydrogen peroxide (H₂O₂) generated during the enzymatic reaction of GOx with glucose could be decomposed by catalase, resulting in the higher sensitivity. The linear range and detection limit were found to be 0.5–100 and 0.2 μmol L^?1, respectively. The proposed biosensor was successfully applied for the determination of glucose in drink and food samples with the spiked recoveries in the range of 95.5 to 101.5 %.     

THE EFFECTS OF GLUCOSE ADJUNCT IN HIGH GRAVITY FERMENTATION BY SACCHAROMYCES CEREVISIAE 2036

Laboratory fermentations of 16°Plato glucose adjunct worts by Saccharomyces cerevisiae 2036 demonstrated the absence of “glucose repression” of maltose and maltotriose uptake. However, when compared to worts in which maltose syrup was employed as an adjunct, residual glucose was present at the end of fermentation, maltose and maltotriose uptake rates were enhanced, fructose uptake was blocked and the sequence of sugar uptake was changed. These findings partially explain residual glucose and fructose that sporadically appear in commercial beers. Further research suggests that the physiological quality of the yeast is of prime importance in carbohydrate metabolism, and that critical concentrations of glucose vary with different physiological conditions for this brewing strain in 16°P wort .     

Evaluation of rheological properties,microstructure and water mobility in buns dough enriched in aleurone flour modified by enzyme combinations

This study aimed to explore the differences between single enzyme and combined enzymes in improving buns dough quality characterised by changes in rheological properties, microstructure and water mobility. The results indicated that xylanase (60 μg g⁻¹)–glucose oxidase (GOX) (40 μg g⁻¹) and xylanase (60 μg g⁻¹)–glucose oxidase (40 μg g⁻¹)–cellulase (30 μg g⁻¹)-modified dough can improve the negative effects of the single enzyme on the dough in terms of extensibility, tenacity and stability, leading to the formation of a softer gluten matrix. This may be due to xylanase (60 μg g⁻¹)–GOX (40 μg g⁻¹) and xylanase (60 μg g⁻¹)–GOX (40 μg g⁻¹)–cellulase (30 μg g⁻¹)-modified dough reduced the free sulfhydryl and significantly increased water-extractable arabinoxylan content (P < 0.05) and enhanced more less-tightly bound water availability. The microstructure observation showed that xylanase (60 μg g⁻¹)–GOX (40 μg g⁻¹) and xylanase (60 μg g⁻¹)–GOX (40 μg g⁻¹)–cellulase (30 μg g⁻¹) modified dough exhibited a more compact and continuous gluten matrix.     

Depletion of glucose in Egyptian egg white before dehydration

Glucose was completely removed from egg white in h by using Streptococcus lactis and 0.2% yeast extract at pH 6.0 and 30 °C. A distinct objectionable odour was developed accompanied by a change in the appearance of egg white. Using Aerobacter aerogenes at pH 7.0 and 37 °C, glucose depletion was completed after 3 to 4 h depending on the initial number of bacteria used. The undesirable changes in odour and appearance of egg white were not observed. Saccharomyces cerevisiae succeeded, in presence of 0.2% yeast extract, in depleting sugar in egg white in 9 h. The optimum pH for the reaction was in the range of 6.0 to 7.5 at 32 °C. Glucose oxidase powder of fungal origin was also used for glucose depletion. Glucose was completely removed after 8 h by adding 3.8 glucose oxidase units/100 ml egg white at pH 7.3 and 14.5 °C. 1.9 and 0.95 glucose oxidase units per ioo ml egg white were not enough for complete glucose removal. No objectionable odour or undesirable changes in egg white were observed.     

The Characterization of Starch and its Components. Part 2. The Semi-Micro Estimation of the Starch-Content of Cereal Grains and Related Materials

A rapid, semi-micro method has been developed for the estimation of the amount of starch in cereal grains. The method is suitable for samples of flour in the range 7.5–20 mg, and hence the amount of starch in a single grain can be readily determined. The procedure – which is given in detail – involves first solubilizing the starch by hot aqueous calcium chloride, and then subjecting the extract to the concurrent action of a-amylase and amyloglucosidase. A quantitative determination of the resultant glucose is then made by the use of glucose oxidase. Relatively few manipulations are involved. This technique is applicable to a wide range of cereals, including the high-amylose-content, genetic mutants of maize. The method has a reproduceability of ± 1.5 %. The new procedure has been compared with methods based on polarimetry and perchloric acid extraction.     

IMPROVEMENT OF THE WHEAT AND CORN BRAN BREAD QUALITY BY USING GLUCOSE OXIDASE AND HEXOSE OXIDASE

The effects of addition of wheat (10, 20 and 30%) and corn bran (10 and 20%) on rheological and bread making properties of flour were examined. To improve dough and bread properties, glucose oxidase (GO) and hexose oxidase (HO) (15–30 and 45 mg/kg) were used separately in each bran-wheat flour formula with L-ascorbic acid at 75 mg/kg, glucose at 0.5% and vital gluten at 9.2%. Water absorption and development time increased as the amount of wheat and corn bran increased, while dough stability, maximum resistance to extension, extensibility, energy and loaf volume decreased. Corn bran was found to be more detrimental to dough rheology and bread characteristics than wheat bran. Corn bran and wheat bran could be used at bread making up to levels of 10 and 20%, respectively. Addition of 30 mg/kg of HO in combination with constant additives was most effective in improving dough and bread characteristics and GO with its 15 mg/kg usage level followed it. Further increasing of enzyme levels led to over oxidizing of doughs and breads.

PRACTICAL APPLICATIONS

Corn bran up to 10% and wheat bran up to 20% levels can be used in bread making. To improve dough and bread quality, besides L-ascorbic acid (75 mg/kg) and vital gluten (as a percentage of added bran weight), GO (15 mg/kg) or HO (30 mg/kg) could be incorporated into wheat flour-bran mixtures. However, the amount of enzyme should be carefully chosen because when they are used above the mentioned levels, they cause overoxidation of doughs and small loaf volumes are obtained. As a conclusion; by using the corn bran, which is a by-product of the starch industry, not only could it be possible to offer healthy alternative breads which contain high amounts of dietary fiber to consumers, but it could also be possible to obtain economical value by evaluating such a by-product in the bread industry.     

FERMENTATION OF SYNTHETIC MEDIA CONTAINING GLUCOSE AND MALTOSE BY BREWER'S YEAST

Brewer's yeast previously cultured on either glucose or maltose as the sole source of carbohydrate has a period of exclusive utilization of glucose when grown on synthetic media containing glucose and maltose. Only when glucose has fallen to a low level does fermentation of maltose begin. This behaviour is thought to be due to an effect of glucose on the maltose permease.     

SEMICONTINUOUS ETHANOL FERMENTATION WITH SHOCHU DISTILLERY WASTE*

An effective utilization system using distillery waste discharged from Japanese traditional shochu factory was developed. Mugi (barley) shochu distillery waste discharged from a novel vacuum distillation procedure (35–40°C) contained a large number of viable yeast (7 × 10⁶ cells/ml), glucoamylase activity (19.7 units/ml), acid protease activity (940 units/ml), and neutral protease activity (420 units/ml). Ethanol fermentation was achieved with a mash composed of glucose as the sola carbon source and mugi shochu distillery waste. After ethanol fermentation was completed the fermented broth was again distilled at 35–40°C in vacuo and the non volatile residue used in the next ethanol fermentation. In this way, semicontinuous ethanol fermentation system of more than 10 cycles was developed. Even in the distillate of the mash of the 8th fermentation cycle, 7.9% of ethanol, 33.0 ppm of ethyl acetate, 28.5 ppm of isobutyl alcohol, and other aromatic compounds were present. A semicontinuous ethanol fermentation system has been developed for shochu distillery waste which conventionally is treated as wastewater.     

Selection of lactic acid bacteria for use in vegetable fermentations

The fermentation of brined vegetables traditionally has depended upon growth of naturally occurring lactic acid bacteria to metabolize the vegetable sugars to organic acids which, together with added salt, results in preservation. Starter cultures have been used only to a limited extent commercially. However, recent efforts to improve fermentation vessels and to develop controlled fermentation methods for fermented vegetables has resulted in an increased interest in developing cultures suitable for application in such methods. Rapid and dominant growth, type and extent of acid production, salt tolerance, temperature range, CO₂ production, cell sedimentation, bacteriophage resistance, nutritional value, and ability to survive as concentrated cultures are factors to consider in developing lactic acid bacterial cultures for use in controlled fermentation of vegetables. Recent examples of efforts to improve cultures include development of nonmalate-decarboxylating strains of lactobacilli for use in cucumber fermentation and isolation of a new species of lactobacillus that produces only the L-isomer of lactic acid from the glucose for use in sauerkraut fermentation. Further improvements in starter cultures for fermented vegetables are likely when suitable genetic transfer systems are developed for selective incorporation or deletion of specific traits.