Fungal Α-amylase Research Articles

Effect of enzymes on baking quality of wheat dough and storage quality of toast bread

SummaryToast is a nutrient‐rich consumer staple with a unique taste. However, retrogradation affects its storage quality and shelf life. Therefore, in this study, we aimed to investigate the effects of enzymes on the baking quality of wheat dough and the storage quality of baked bread. Fungal α‐amylase (FAM), lipase (LIP), and maltose amylase (MAM) were added to wheat dough under quadruple fermentation to evaluate their effects on the quality of wheat dough and toasted bread during storage. FAM reduced the water absorption and stability of wheat flour, whereas LIP and MAM improved its properties. Moreover, all three enzymes increased the fermentation height and gas‐holding capacity of the dough, resulting in toast with a larger specific volume and low hardness. Toast containing 15 mg kg−1 MAM had the highest number of air holes and the best elasticity. Furthermore, 9 mg kg−1 FAM, 45 mg kg−1 LIP, and 15 mg kg−1 MAM retarded the retrogradation of toast during storage, reduced its hardness, and decreased the short‐range order and relative crystallinity. These findings indicate that enzymes can delay retrogradation in toast to extend its shelf life. These results further suggest that enzymes inhibit recrystallisation to delay toast ageing. Thus, this study provides theoretical references for the practical application of enzymes in bakery products.

Unveiling the Proximate, Sensory, Microbial, And Shelf Life of Leavening Agent Modified Gluten-Free Cookies Formulated With Indigenous Nepalese Hill Grains

The prevalence of gluten-related disorders has risen due to the increased consumption of bakery products made from refined flour in recent decades. This study focused on employing indigenous hill grain flours, such as Taichung 176 rice flour, maize flour, sweet buckwheat flour, and finger millet flour from Nepal, to create gluten-free cookies by incorporating fungal αamylase, baking powder, and baker's yeast as modified leavening agents, in contrast to the typical refined flour-based cookies. 16 different composite flours were made by combining millet, maize, buckwheat, and glutinous rice flours in a 75:25 percentage, then subjected to 30°C proofing for 1 hour for food grade fungal α-amylase with an improver and baker's yeast treated sample before blending with cream and baking for 20 minutes at 200°C.The ash content, moisture content, sensory qualities, microbial load, and shelf life of cookies were studied and compared with control cookies. Over 60-days storage period, most formulated cookies had moisture content below 5%, except BWBY cookies (6%to 8.37%). The ash percentage of cookies significantly increased from 0.81% to 2.59%. The highest ratings for taste (8.0), texture (7.6), and crunchiness (8.1) were achieved for cookies produced with 75:25% Millet: Taichung 176 rice flour, treated with fungal α-amylase, improver, and baker’s yeast.Utilization of proofing techniques in that sample improved their color, taste and resolved the gritty texture issue Formulated gluten-free cookies (GFC) had higher ash and moisture but were still acceptable despite increased microbial load and moisture until the 60th day of storage. Overall acceptability (OAC) score slightly dropped but remained good (7 of 9) after 2 months of storage. Notably, gluten-free cookies exhibited higher nutritional value and retained their acceptability for up to 60 days when stored at ambient temperature (25 ± 2°C).

Solid state malic acid esterification on fungal α-amylase treated corn starch: Design of a green dual treatment

For the first time, the current work applied fungal α-amylase treated corn starch in granular form to produce solid state malate-esterified starch (MES). The pores and channels created on the granules after the enzymatic modification could provide more possibilities for malic acid to esterify the starch, resulting in the increase of substitution degree (0.084) and reaction efficiency (86.6%) compared to NS. Based on the obtained results, the dual treatment significantly increased solubility, amylose content, and syneresis, but reduced transparency, viscosity, digestibility rate, and swelling power compared to those of NS. The occurrence of esterification onto starch chains was confirmed by FT-IR at 1720 cm−1. Other techniques including SEM, XRD, and DSC were employed to examine changes in the structure of starch granules after applying each treatment. Also, the greenness of the combined modification (score: 77) was proved by using a new methodology named Eco-Scale.

Enhancement of Fungal Enzyme Production by Radio-Frequency Electromagnetic Fields.

Enzyme production by microorganisms on an industrial scale has demonstrated technical bottlenecks, such as low efficiency in enzyme expression and extracellular secretion. In this study, as a potential tool for overcoming these technical limits, radio-frequency electromagnetic field (RF-EMF) exposure was examined for its possibility to enhance production of an enzyme, α-amylase, in a filamentous fungus, Aspergillus oryzae. The RF-EMF perfectly resonated at 2 GHz with directivity radiation pattern and peak gain of 0.5 dB (0.01 Watt). Total protein concentration and activity of α-amylase measured in media were about 1.5-3-fold higher in the RF-EMF exposed (10 min) sample than control (no RF-EMF) during incubation (the highest increase after 16 h). The level of α-amylase mRNA in cells was approximately 2-8-fold increased 16 and 24 h after RF-EMF exposure for 10 min. An increase in vesicle accumulation within fungal hyphae and the transcription of some genes involved in protein cellular trafficking was observed in RF-EMF-exposed samples. Membrane potential was not changed, but the intracellular Ca2+ level was elevated after RF-EMF exposure. Our results suggest that RF-EMF can increase the extracellular level of fungal total proteins and α-amylase activity and the intracellular level of Ca2+.

Biodegradation Study of Potato Starch-Based Bioplastic

Background: Plastics are indispensable for our society. The extensive use of petroleumbased plastic and dumping of the same in soil and water body greatly affects our environment and biodiversity. However, biodegradable plastics can reduce the volume of waste in packaging materials. Therefore, biomass-derived polymers are promising alternatives to the petroleum-based non-degradable polymer to address the environmental issues. Objective: A large number of reports on the synthesis and characterization of starch-based bioplastic are available in the literature. However, a detailed biodegradation study of the starchbased bioplastic is rarely reported. We have prepared potato starch-based bioplastic with the combination of various plasticizers (glycerol, sorbitol, and xylitol) through hydrogel formation and carried out their biodegradation study. Method: Present study investigated the biodegradation of potato starch-based bioplastic in the natural environment, in cultured bacteria, and with fungal α-amylase. Results: Starch-based plastic is completely degraded in the natural environment within two months. Bacteria culture in solid media resulted in various types of bacterial colonies. Among the various bacterial colonies, the white circular colony was the major bacteria that degrade starchbased plastic. Furthermore, we screened the starch-based plastic degrading bacteria and isolated the pure culture through the streak plate method. Conclusion: In the presence of cultured bacteria and with fungal α-amylase, starch-based plastic is completely degraded within 96 h and 48 h, respectively.

Characterization of a surfactant-stable α-amylase produced by solid-state fermentation of cassava (Manihot esculenta Crantz) tubers using Rhizopus oligosporus: Kinetics, thermal inactivation thermodynamics and potential application in laundry industries

α-Amylase is a foremost hydrolytic enzyme used for various industrial processes. In the present study, Rhizopus oligosporus α-amylase (ROAA) produced during solid state fermentation of cassava ( Manihot esculenta ) tubers by the fungus was partially purified and biochemically characterized. The kinetic and thermal inactivation thermodynamics properties of the partially purified enzyme were also evaluated as well as the potential application in cloth washing. The ROAA was purified by 4.11-fold and had a molecular weight of 60 kDa. ROAA was optimally active at 60 °C, pH 5.0 and had a salt tolerance of 1–100 mM NaCl for 120 min. The activity of the α-amylase was significantly (p < 0.05) increased in the presence of various inorganic salts especially at 10 mM. Ethylenediaminetetraacetic acid (EDTA), urea and thiourea enhanced ROAA activity. Triton X-100 enhanced ROAA activity by 141.97%, whereas sodium dodecyl sulphate (SDS) decreased it by 28.58%. Tween 20 and Tween 80 did not significantly affect ROAA activity at 1 mM. V max , K m and K cat of ROAA were 37.59 U/mg protein, 16.39 mg/mL and 0.016 s −1 , respectively. Thermal stability indicators such as half-life, D-value at 70 °C and Z-value were 101.91 min, 338.70 min, and 48.78 °C, respectively. Cloth washing efficiency of a mixture of the isolated enzyme and commercial detergents was high relative to detergent-only trial. The enzyme had high thermal stability, optimized activity in the presence of some inorganic salts, and resistance to several surfactants and a chelating agent. The fungal α-amylase reported in this study would find relevance not only in starch-based industries but also in laundry. • R. oligosporus secreted α-amylase during the SSF of cassava tubers. • The α-amylase was optimally active at 60 °C and pH 5, activated by EDTA. • Thermal inactivation thermodynamics followed first order kinetics. • The α-amylase (ROAA) produced was moderately thermally stable (D-value, Z-value). • ROAA showed resistance to the inhibitory action of some surfactants.

A thermostable extracellular α-amylase from Aspergillus flavus S2-OY: Purification, characterisation and application in raw starch hydrolysis

An amylolytic fungus was isolated locally from the soil of a cassava waste dumpsite. It was identified as Aspergillus flavus S2-OY using 18S rRNA gene sequencing with gene bank accession number MZ267053.1. α-Amylase was produced from the fungus through solid substrate fermentation of potato (Solanum tuberosum L.) peel, a cheap and renewable substrate. The fungal enzyme was purified 13.41-fold by ammonium sulphate and ion exchange chromatography (CM Sephadex C-50), with final yield of 13.41%. Apparent molecular weight of 55.0 kDa was obtained for the purified enzyme, using SDS-PAGE. Optima pH (6.0) and temperature (70 °C) of α-amylase activity were determined for the enzyme which also showed thermal stability up to 70 °C, with 80% residual activity after 120 min. The enzyme exhibited a wide range of pH stability (4.0 to 7.0). Kinetic parameters Km and Vmax values obtained with soluble starch were 158 µg/ml/min and 1.51 mg/ml, respectively. The enzyme was slightly inhibited by Mg2+. Mn2+, Zn2+, Na+, K+, Hg2+ and the chelating agent, EDTA, at 5.0 mM concentration. However, it was activated by Sn2+. The enzyme hydrolysed gelatinised and ungelatinized raw yam, corn, rice and millet starches strongly but cassava starch moderately. These results revealed that cost-effective α-amylase production from Aspergillus flavus S2-OY could be realised with the use of potato peel as a cheap substrate, under solid substrate fermentation condition. Also, the fungal α-amylase is a raw starch-hydrolysing, acid to neutral and thermostable enzyme with potential for broad biotechnological applications.

Nutritional evaluation of Sphenostylis stenocarpa flour, its bread and effect of additives.

The present research sought to experiment the effect of additives such as dry gluten powder (DGP), fungal α-amylase (FAA), sodium stearoyl-2-lactylate (SSL) and their combination (GAS) on the rheological and nutritional profile of bread. The incorporation of varied percentage (0-20%) of stenostylis stenocarpa flour (ssF) into WF(Wheat Flour) was optimized at 15%. The results showed that the incorporation of 15% ssF decreased the farinograph dough stability and extensograph resistance to extension. There was protein matrix disruption in 15% ssF dough contrary to 15% ssF + GAS dough as shown in scanning electron micrograph (SEM). However, the addition of GAS to 15% ssF produced bread with an improved quality score that competed favourably with control bread. The organoleptic evaluation revealed an overall quality score of 52.5, 40 and 49% for control, 15% ssF and 15% ssF + GAS bread respectively. Furthermore, 15% ssF + GAS revealed a higher value of ash, protein, dietary fibre, total phenol contents and IC50 of DPPH radical scavenging activity in comparison to control bread. Hence, the present study showed that partial replacement of WF with 15% ssF + GAS has a positive effect on the overall sensorial acceptability and nutritional value of bread.

Effect of amylolysis on the formation, the molecular, crystalline and thermal characteristics and the digestibility of retrograded starches

This study evaluated the effect of amylases on the formation, and characteristics of retrograded starches using sweet potato (SPS), cassava (CAS) and high amylose maize (HAS) starches. The starches were gelatinized, hydrolyzed with fungal or maltogenic α-amylase, de-branched and retrograded. The modified starches were then analyzed for digestibility, chain size distribution, relative crystallinity and crystallite size, thermal properties and the proportion of double helices. CAS was the most susceptible and HAS the most resistant to the action of both enzymes. Amylolysis was efficient in forming resistant starch type 3 (RS3) and high levels (> 60%) were found for all starches. RS3 content was highly correlated with the proportion of chains with degrees of polymerization between 13 and 30 for all starches, especially for the root starches, while for HAS, the high amylose content and reduction in the size of amylose chains and very long amylopectin chains also deeply contributed for the RS3 formation. These sizes (DP 13–30) are best suited for the formation of a more crystalline, more perfect, and more strongly bonded structure, composed of larger crystallites, and with a higher concentration of double helices. High correlation coefficients were found between RS3, relative crystallinity, crystallites size, and enthalpy change.

Evaluation of in-vitro antidiabetic activity of leaf juice of Plectranthus amboinicus (lour.)

Diabetes mellitus ‘the disease of modern civilization’ is characterized by chronic hyperglycaemia. The management of elevated post prandial glucose is critical to control the sequale of complications and α-amylase, α-glucosidases are responsible for elevated plasma glucose. Enzyme inhibitors in current clinical practice like acarbose, voglibose etc. are known to cause various gastrointestinal side effects. The present study was aimed to screen for potential α-amylase and α-glucosidase inhibitors from natural sources by in–vitro antidiabetic assays to overcome the side effects and toxicity. Different concentrations of leaf juice of Plectranthus amboinicus Lour. (20, 40, 60, 80 &amp;amp;100 μg/ml) were tested against fungal α-amylase and α-glucosidases isolated from albino rat small intestine and a prominent dose dependent inhibition of the enzymes was observed comparable with the marketed product, Acarbose. The IC50 values of LJPA and acarbose on fungal α-amylase was found to be 83.15 &amp;amp;52.15 μg/ml respectively. The IC50 values of LJPA and acarbose on α-glucosidase was found to be 92.44 &amp;amp;54.84 μg/ml respectively. The protein concentration of leaf juice was found to be 10.6 mg/ml.

Improving the thermostability and acid resistance of Rhizopus oryzae α-amylase by using multiple sequence alignment based site-directed mutagenesis.

Higher thermostability or acid resistance for fungal α-amylase will help to improve the sugar-making process and cut down the production costs. Here, the thermostability or acid resistance of Rhizopus oryzae α-amylase (ROAmy) was significantly enhanced by site-directed evolution based on multiple sequence alignment (MSA) method. For instance, compared with the wild-type ROAmy, the optimum temperature of mutants G136D and A144Y was increased from 50 to 55°C, whereas for mutants V174R and I276P, the optimum temperature was increased from 50 to 60°C. The optimum pH of mutants G136D and A144Y shifted from 5.5 to 5.0, whereas for mutants V174R and T253E, the optimum pH changed from 5.5 to 4.5. The results showed that mutant V174R had a 2.52-fold increase in half-life at 55°C, a 2.55-fold increase in half-life at pH 4.5, and a 1.61-fold increase in catalytic efficiency (kcat /Km ) on soluble starch. The three-dimensional model simulation revealed that changes of hydrophilicity, hydrogen bond, salt bridge, or rigidity observed in mutants might mainly account for the improvement of thermostability and acid resistance. The mutants with improved catalytic properties attained in this work may render an accessible and operable approach for directed evolution of fungal α-amylase aimed at interesting functions.

Antioxidant and antifungal activity of phenolic compounds and their relation to aflatoxin B1 occurrence in soybeans (Glycine max L.).

Soybean is widely used in food formulations; however, few studies on fungal or mycotoxin contamination have been undertaken. Free, conjugated, and bound phenolic compounds, and their antioxidant and antifungal potential, were therefore evaluated together with the occurrence of aflatoxin B1 (AFB1 ) in soybeans. The conjugated and bound phenolic soybean extracts were more efficient for the inhibition of the 2,2 diphenyl-1-picryl-hydrazyl (DPPH) radical, the peroxidase enzyme, and the fungal α-amylase enzyme. Aflatoxin B1, detected at low levels (0.96 to 1.67 ng g-1 ), confirmed the protective effect of soybean phenolic compounds against mycotoxigenic contamination. Principal component analysis confirmed that syringic, p-hydroxybenzoic, p-coumaric acids and vanillin were essential for antioxidant and antifungal activities. This study presented new insights into the functionality of phenolic compounds in soybeans, regarding their potential to protect the crops naturally against fungal contamination, avoiding aflatoxin production, as attested by the correlations between phenolic compounds and antioxidant mechanisms. © 2019 Society of Chemical Industry.

Prediction of Pasting Properties of Dough from Mixolab Measurements Using Artificial Neuronal Networks.

An artificial neuronal network (ANN) system was conducted to predict the Mixolab parameters which described the wheat flour starch-amylase part (torques C3, C4, C5, and the difference between C3-C4and C5-C4, respectively) from physicochemical properties (wet gluten, gluten deformation index, Falling number, moisture content, water absorption) of 10 different refined wheat flours supplemented bydifferent levels of fungal α-amylase addition. All Mixolab parameters analyzed and the Falling number values were reduced with the increased level of α-amylase addition. The ANN results accurately predicted the Mixolab parameters based on wheat flours physicochemical properties and α-amylase addition. ANN analyses showed that moisture content was the most sensitive parameter in influencing Mixolab maximum torque C3 and the difference between torques C3 and C4, while wet gluten was the most sensitive parameter in influencing minimum torque C4 and the difference between torques C5 and C4, and α-amylase level was the most sensitive parameter in predicting maximum torque C5. It is obvious that the Falling number of all the Mixolab characteristics best predicted the difference between torques C3 and C4.

Improvement of the aroma of lily rice wine by using aroma-producing yeast strain Wickerhamomyces anomalus HN006

A fruity aroma-producing yeast strain was isolated with the aim of improving the aroma of fermented lily rice wine, and identified as Wickerhamomyces anomalus HN006. In addition, the effects of adding solid residues of previous fermentation cycles, and of fungus α-amylase and W. anomalus HN006 supplementation on the biochemical parameters of lily rice wine were evaluated. The optimum quality of the wine, in terms of ethanol and residual sugar content, acidity levels and aroma, was obtained with 5% (w/v) solid residue addition, and supplementation with 10 U/g fungal α-amylase and 2% (v/v) W. anomalus inoculum on the 4th day of fermentation. Volatile compound profiles, the total amount of amino acids and the sensory characteristics of the lily rice wines produced by the two fermentation processes were also evaluated and compared. The lily rice wine obtained from our optimized experimental technology produced higher amounts of some esters, free fatty acids, alcohols, aldehydes, ketones, alkenes, volatile phenol and thiazole, in addition to higher total amino acid content and sensory scores compared to the traditionally brewed wine. Our process resulted in an intensification and improvement of lily rice wine aroma.

Influence of molecular structure on the susceptibility of starch to α-amylase

The effect of the molecular structure of sweet potato (SPS), cassava (CAS) and high amylose maize (HAS) starches on the susceptibility to fungal and maltogenic α-amylases was investigated. The logarithm of the slope (LOS) and non-linear least-squares (NLLS) methods were used for fitting hydrolysis kinetics data. The malto-oligosaccharides released during hydrolysis were quantified and the hydrolysis residues were analyzed. The hydrolysis kinetic curves were well fitted to the LOS and NLLS models. SPS, CAS and HAS were hydrolyzed in one single phase by fungal α-amylase while two hydrolysis phases were identified for the root starches and a single phase for HAS, when maltogenic α-amylase was used. The lowest percentage of residual starch was found for CAS, independent of enzyme source, due to the high proportion of amylopectin short chains in this starch. On the other hand, the high proportion of HAS long chains contributed to its increased starch degradation rate coefficient during fungal α-amylase hydrolysis, while the high amylose content favored the endo-action pattern of maltognic α-amylase. Independent of starch source, malto-oligosaccharides of different sizes, especially G2-G5, were released after the fungal α-amylase action which hydrolyzes mainly inner and long amylopectin chains. Mainly maltose was produced in the maltogenic α-amylase hydrolysis which breaks the outer amylopectin chains by exo-action and amylose chains by endo-action. The starch molecular structure strongly interferes in both enzyme susceptibility and the action mechanism, as well as in the distribution and amount of products released.

OPTIMIZATION THE PARAMETER PROCESS OF SOLID-STATE FERMENTATION TO PRODUCE THE FUNGAL Α-AMYLASE ON AGRO-INDUSTRIAL BY-PRODUCTS

The present work is concerned with optimization the process parameter of the production of fungal α-amylase enzyme by Aspergillus niger ATCC 102 and Aspergillus oryzae NRRL 6270 using solid-state fermentation (SSF) process on two agro-industrial by-products. Different cultural parameter and conditions such as moisture content of prepared agro-industrial by-product (30 to 70%), fermentation period (12 to 120 h.) and incubation temperature (25-35°C) were optimized to obtain the maximum yield of α-amylase activity. The study is concerned to produce fungal αamylase on agro-industrial by-products such as inner layers of sugarcane bagasse (Saccharum officinarum) (SCB) and corn gluten meal (Zea mays) after addition of germ cake and corn steep liquor (CGM ) were used as solid substrates. The optimum conditions for SSF as follows temperature at 30°C and two moisture content level (60 - 30%) for SCB by Aspergillus niger and CGM after addition of germ cake and corn steep liquor by two fungal strains, respectively and incubation period of 72, 48, 24 hours for SCB by Aspergills niger, CGM by two fungal strains, respectively and SCB by Aspergillus oryzae, producing α-amylase activity 3.49U/g (solid substrate) with SCB by SSF after 24 hours by Aspergillus niger, whereas 3.78U/g (solid substrate) by Aspergillus oryzae after 48 hours. The highest record of amylase activity was obtained on SCB by SSF 3.49U/g (solid substrate) after 24 hours by Aspergillus niger, whereas 3.78U/g (solid substrate) by Aspergillus oryzae after 48 hours. Optimum α-amylase enzyme activity was observed at 30°C. Utilization of agroindustrial by-product provides an alternative method and value-addition in cost effectiveness of bioprocess. The obtained results demonstrated that, the potential application of the used strategy for αamylase enzyme production from agro-industrial by-products.

Engineering the protein secretory pathway of Saccharomyces cerevisiae enables improved protein production

Baker's yeast Saccharomyces cerevisiae is one of the most important and widely used cell factories for recombinant protein production. Many strategies have been applied to engineer this yeast for improving its protein production capacity, but productivity is still relatively low, and with increasing market demand, it is important to identify new gene targets, especially targets that have synergistic effects with previously identified targets. Despite improved protein production, previous studies rarely focused on processes associated with intracellular protein retention. Here we identified genetic modifications involved in the secretory and trafficking pathways, the histone deacetylase complex, and carbohydrate metabolic processes as targets for improving protein secretion in yeast. Especially modifications on the endosome-to-Golgi trafficking was found to effectively reduce protein retention besides increasing protein secretion. Through combinatorial genetic manipulations of several of the newly identified gene targets, we enhanced the protein production capacity of yeast by more than fivefold, and the best engineered strains could produce 2.5 g/L of a fungal α-amylase with less than 10% of the recombinant protein retained within the cells, using fed-batch cultivation.

Use of fungal alpha amylase and ascorbic acid in the optimisation of grain amaranth-wheat flour blended bread.

Grain amaranth–wheat flour bread was optimised using ascorbic acid (0.03% dry weight basis) and fungal α-amylase (10 ppm) to investigate their effects on sensory properties of the breads. Six formulations were used in the ratios of 5:95, 10:90, 15:85, 20:80 and 25:75 grain amaranth to wheat flour compositions, while the control bread had 100% wheat flour. Consumer acceptability and preference ranking tests were conducted to describe and evaluate preference and acceptability of the breads. Analysis of consumer acceptability data revealed that there were significant differences (p < 0.05) for all the samples in all the attributes tested. Overall consumer acceptability results showed no difference at 25% for all improvers. Principal component analysis for descriptive tests performed by a trained panel demonstrated variations among the breads in graininess, elasticity, crumb colour, stickiness and crumb moistness regardless of the improvers used. The study concludes that using improvers to optimise grain amaranth–wheat flour bread can help improve both the nutritional and organoleptic properties of bread.

Central Composite Design-Desirability Function Approach for Optimum Ultrasound-Assisted Extraction of Daidzein and Genistein from Soybean and Their Antimycotoxigenic Potential

Soybean isoflavones have been underestimated about their possible antifungal or antimycotoxigenic potential. In the present investigation, chemometric approaches were used such as the fractioned experimental design, the central composite rotatable design, and the Derringer’s desirability function to optimize a method to extract the isoflavones daidzein and genistein by ultrasound-assisted extraction. The optimized method was validated and applied to ten soybeans. The possible antimycotoxigenic abilities of isoflavones were evaluated by the inhibition of hydrolytic and oxidative enzymes. The multivariate procedures were efficient to determine the optimal extraction conditions, using daidzein and genistein concentration as responses. The best conditions were extraction time, 30 min; frequency, 55 kHz (36 kJ mL−1); hydrolysis time, 20 min; and hydrolysis temperature, 168 °C. The method was validated according to Eurachem guidelines and considered reproducible. The daidzein concentration was higher than genistein in soybeans. Low concentrations of aglycones were capable to inhibit fungal α-amylase (0.1 μg mL−1), highlighting genistein. Daidzein and genistein were able to inhibit oxidative processes in two strands, inhibition of oxidative enzyme and free radical propagation. These properties indicate that these isoflavones are able to contribute to avoid stress situations that could promote fungal contamination and manifestation of their mycotoxigenic potential.

Estimation and Validation of Flour Exposure in Bakeries in Alberta, Canada.

In epidemiological studies of work-related ill-health only current exposures can, at best, be measured. Previous exposures may be estimated using contemporaneous hygiene records or published data. This study aimed to create a job exposure matrix for exposure in bakers for use in an ongoing cohort study. A systematic review was conducted of English language publications on exposures in bakeries. All publications that appeared to contain quantitative measures of exposure to flour dust, wheat allergen, or fungal α-amylase were read independently by two investigators and relevant data extracted. A third investigator reviewed these data and publications were retained that reported full-shift exposures to inhalable dust, wheat allergen, or α-amylase, and for which geometric means (GMs) were given or could be estimated. For each study, the number of sampling results contributing to each GM was recorded together with information on task, bakery size, product, filter type, sampling head, the country in which the study was conducted, and the estimated year of sampling. Multivariable models were elaborated for each exposure using a linear mixed effects approach. The predictive capacity of the model for inhaled particles was tested against samples collected in eight Alberta bakeries. The capacity of exposure intensity, estimated from each of the three models, to predict sensitization was tested against skin prick testing (SPT) for bakery allergens in bakers currently employed in Alberta. One thousand three hundred and ninety-seven publications were identified through the systematic search, of which 27 had data used to create one or more of the predictive models. Weighted GMs were used as outcome variables. For inhalable dust, task, bakery size, type of sampling head, and year of sampling contributed to the final model. For wheat allergen and α-amylase, task, bakery size, sampling head, and year of sampling again contributed. Product (bread rather than confectionary or mixed products) was also important in these two latter measures. The model for inhalable dust was used to predict the concentration in 33 samples from Alberta bakeries. Overall, 91% of observed samples had 95% confidence intervals (CIs) overlapping the 95% CIs of the predicted values. A model including the Alberta samples found no effect attributable to Alberta provenance. Using this model for inhalable dust and the models developed solely from the literature for wheat allergen and α-amylase, a positive SPT for bakery allergens in 57 bakers recruited for this study was significantly related to log cumulative exposure for each of the three outcome variables and to log exposure intensity for wheat allergen and α-amylase. The exposure models developed from the literature provide useful estimates of exposure. Calibration of the models against locally collected samples may be useful for countries poorly represented in the modeling dataset.