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Human saliva contains numerous salivary components that are fundamental for a healthy oral environment and the oral processing of foods. To study a possible differential influence of orosensory stimulation and metabolic activation on salivary composition, human parotid salivary flow, pH, A280, and α-amylase activity were measured before, during and after real or sham (sip-and-spit) sucrose intakes. Variations in these salivary characteristics were related to perceived satiety. Sucrose, as either real or sham intake, increased salivary flow and pH and decreased A280 before returning to pre-intake levels. Increased salivation was dependent on the sucrose concentration and was accompanied with a higher pH and lower A280. After sucrose ingestion, the salivary α-amylase activity increased, while no increase occurred after sham sucrose intake. Similarly, rated satiety increased with real but not by sham sucrose intake. This indicated that salivary α-amylase is associated with perceived satiety controlled by caloric perception downstream of the oral cavity. © 2009 Informa UK Ltd.

The role of friction in food texture sensations are reviewed with the focus on results from our own laboratory, concentrating on texture sensations that are affected by the lubricative properties (e.g., roughness and creaminess), by the viscosity (e.g., melting and thickness) and by the used thickeners (e.g., airiness and heterogeneity). A food's lubricative properties are affected by its fat content, fat droplet size, particle size and shape and thickener. Foods with lower fat contents, larger fat droplets, larger particles and specific thickeners exhibited higher friction while their creaminess and fattiness sensations, associated with good lubrication, are reduced. Roughness and dryness sensations, associated with poor lubrication, are increased. Taste and flavor compounds also affected these texture sensations, albeit via a different mechanism. Specific compounds can affect the lubricative properties of saliva resulting in friction-related sensations, such as astringency. Astringent compounds interact with proline-rich proteins in saliva, causing precipitation that may be sensed as discrete particles and/or increased roughness. Alternatively, the compounds may precipitate dead cells and other debris present in saliva. Astringent compounds may also directly affect the surface properties of the oral mucosa. © 2006, Blackwell Publishing.

In isolated embryos from dormant barley grains, synergistic effects of fusicoccin (FC) and gibberellic acid (GA3) were observed on the induction of α-amylase mRNA expression. However, no α-amylase mRNA expression could be induced by both agents in embryos from non-dormant grains. Both light- and electron-microscopy studies demonstrated that there were large numbers of starch granules present in mature embryos (mainly in scutellum) from dormant barley grains but none or almost none in embryos from non-dormant grains. Furthermore, the content of reducing sugars in embryos from dormant grains was about half of that from non-dormant grains. In contrast to GA3, FC was able to induce a strong acidification of extracellular pH (pH(e)). Clamping the pH(e) to prevent FC-induced acidification, by using 50 mM MES buffer (pH 5.6), caused an inhibition of GA3- or FC-induced α-amylase mRNA expression but did not affect the germination of embryos from dormant grains. In addition, in MES buffer, addition of FC or a combination of FC and GA3 increased the germination rate of embryos isolated from dormant grains, though large numbers of starch granules were still present in these embryos. Based on these observations, the presence of starch granules and a low reducing sugar level in embryos from dormant grains is not a factor for control of grain dormancy and germination.

Introduction: Exposure to flour dust has been reported as an important risk factor for allergic respiratory disease among bakery workers. A high prevalence of allergic sensitization and asthma was recently reported in South African supermarket bakeries. The aim of this study was to conduct a detailed exposure assessment of these bakeries so as to provide the baseline for a broader intervention study.Methods: A total of 211 full-shift personal samples were collected on randomly selected individuals within five different job categories in 18 bakeries. The samples were analyzed for particulate mass and specific flour dust allergens (wheat, rye, and fungal alpha-amylase). Exposure models were developed using job, bakery size, tasks, and specific ingredients used. Bakery and worker were regarded as random effect components.Results: Bread bakers had the highest average (geometric mean) exposures (1.33 mg m ^-3 flour dust particulate, 13.66 µg m^-3 wheat allergens, and 5.14 µg m^-3 rye allergens). For alpha-amylase allergens, most samples were below the limit of detection for several occupational titles. In the mixed effect models, the significant predictors of elevated exposure to inhalable dust particulate as well as wheat and rye allergen concentrations were large bakery size, bread baking, and use of cereal flours, while tasks such as confectionery work were negatively correlated with these exposure metrics. Weighing tasks and use of premix products were associated with increased exposure to fungal alpha-amylase. A high correlation between particulate dust and wheat (r = 0.84) as well as rye (r = 0.86) was observed, with a much lower correlation between particulate dust and fungal alpha-amylase (r = 0.33). Overall, a low proportion (39%) of bakery stores implemented various control measures to reduce dust exposures in the bakeries.Conclusions: This study confirms that current exposure control strategies in supermarket bakery stores are inadequate in reducing dust exposures to protect the health of bakery workers.

Background Thickening of foods and fluids is commonly used in the management of dysphagia to reduce the risk of aspiration. The use of starch-based thickeners is established. However, the use of gums in thickeners is gaining interest as they are resistant to salivary amylase, which may promote safer swallowing. Aims To compare the effect of human saliva on the consistency of drinks thickened with a gum-containing (GC) thickener with that of drinks thickened with four starch-based (SB) thickeners. Methods & Procedures Three drinks (artificial tap water, hot coffee and full-fat milk) were thickened to custard consistency with the different thickeners. Compression force and amount of thin liquid formed were determined after 10 and 50 min of contact with human saliva with standardized amylase activity and compared with a control inoculated with water. Outcomes & Results Drinks thickened with GC thickener were significantly less sensitive to thinning by human saliva compared with drinks thickened with all four SB thickeners (p < 0.05). Moreover, incubation of SB-thickened drinks with human saliva resulted in the formation of at least 10 g of decantable liquid, while for GC-thickened drinks, almost no liquid was formed. Conclusions & Implications These results show that GC thickeners contain their consistency better in contact with human saliva than SD thickeners. This may enhance the swallowing safety of people with dysphagia. © 2014 Royal College of Speech and Language Therapists.

Currently known fungal α-amylases are well-characterized extracellular enzymes that are classified into glycoside hydrolase subfamily GH13_1. This study describes the identification, and phylogenetic and biochemical analysis of novel intracellular fungal α-amylases. The phylogenetic analysis shows that they cluster in the recently identified subfamily GH135_5 and display very low similarity to fungal α-amylases of family GH13_1. Homologues of these intracellular enzymes are present in the genome sequences of all filamentous fungi studied, including ascomycetes and basidiomycetes. One of the enzymes belonging to this new group, Amy1p from Histoplasma capsulatum, has recently been functionally linked to the formation of cell wall α-glucan. To study the biochemical characteristics of this novel cluster of α-amylases, we overexpressed and purified a homologue from Aspergillus niger, AmyD, and studied its activity product profile with starch and related substrates. AmyD has a relatively low hydrolysing activity on starch (2.2 U mg-1), producing mainly maltotriose. A possible function of these enzymes in relation to cell wall α-glucan synthesis is discussed. © 2007 SGM.

The role of salivary α-amylase in odour, flavour, and oral texture sensations was investigated in two studies in which the activity of salivary amylase present in the mouth of human subjects was either increased by presenting custards with added α-amylase or decreased by presenting custards with added acarbose, an amylase inhibitor. For starch-based vanilla custard desserts, amylase resulted in increased melting and decreased thickness sensations, whereas acarbose had the opposite effect, i.e., decreased melting and increased thickness. Other affected attributes included creamy mouth feel, creamy after feel, and fatty after feel. Creaminess, which is considered to be a highly desirable food quality, decreased by as much as 25% with added amylase and increased by as much as 59% with added acarbose. Neither additional amylase nor acarbose affected sensations for a nonstarch-based carboxy methylcellulose (CMC) vanilla custard dessert. This indicates that the effects of amylase on viscosity-related sensations of starch-based custards, such as perceived melting and thickness, are caused by amylase-induced breakdown of starch. Partial Least Square (PLS) analysis indicated that the effects of amylase and acarbose on perceived creaminess are not only driven by their effects on perceived melting and thickness, but also by their effects on perceived flavour. © 2004 Elsevier Inc. All rights reserved.

Background: Occupational allergen exposure assessment usually requires airborne dust sampling at the worksite followed by dust extraction and enzyme immunoassay (EIA) analysis at the laboratory. Use of semiquantitative lateral flow immunoassays (LFIAs) may allow a more rapid detection procedure with direct on-site demonstration of a bioallergen exposure hazard. Objective: In a field study, we evaluated a recently developed LFIA for fungal α-amylase, an important bakery allergen. Methods: Airborne and surface dust (wipe) samples and samples from flours and baking additives used at the workplace were collected in 5 industrial bakeries and tested in the LFIA for fungal amylase. For comparison, amylase was measured in sample eluates with the reference EIA method. Results: Sensitivity of the LFIA was 1 to 10 ng/mL, and of EIA, ∼25 pg/mL. In LFIA, most flour samples, 84% of wipe samples, 26% of personal airborne dust, and none of the 26 ambient air dust samples produced a visible reaction. Wipe samples from dough-making areas and flour samples gave the strongest reactions. All extracts with >5 ng allergen per milliliter showed a positive LFIA reaction. Conclusion: The LFIA for fungal amylase is an easy and rapid method to demonstrate the allergen directly at the worksite in less than 10 to 20 minutes. Similar LFIA methods may be used for other occupational allergens in other work environments. Clinical implications: Lateral flow immunoassays for occupational allergens may be of great value in occupational hygiene surveys to demonstrate directly to workers and supervisors the hazards of work-related bioallergen exposure. © 2006 American Academy of Allergy, Asthma and Immunology. Chemicals / CAS: amylase, 9000-90-2, 9000-92-4, 9001-19-8; Air Pollutants, Occupational; alpha-Amylase, EC 3.2.1.1; Antigens, Fungal; Dust

The isolation and purification of α-amylase from an industrial enzyme sample is described using crosslinked starch powder as an affinity adsorbent. The process was studied with regard to the stability of the adsorbent, the stability of the enzyme, and the capacity of the adsorbent for the enzyme. The adsorbent was used in a repeated adsorption-desorption process to evaluate the binding capacity and stability of the adsorbents in continuous processes. The adsorption kinetics of the matrix was improved because during the repeated process the diffusion resistance of the matrix decreased. This effect was accompanied by an increase of the capacity of the adsorbent for the enzyme, yielding adsorption levels up to 0.5 mg protein per mg adsorbent. The matrix itself was slowly degraded, but no decline of the adsorption levels was observed during 90 cycles under the experimental conditions used. The lifetime of the matrix was estimated to be 140 repeated runs. Approximately 10-40 kg of pure α-amylase can be obtained with 1 kg of adsorbent. This may yield an economically attractive purification process because the adsorbent is cheap and easy to prepare, as it consists of starch crosslinked with epichlorohydrin.

Saliva is expected to be of significance for the perception of food stimuli in the mouth. Mixing the food with saliva, including breakdown and dilution, is considered to be of large importance for semi-solids as these products are masticated without chewing. It is known that there are large variations in composition of saliva originating from different glands and different subjects. In this study we investigated how variations in salivary characteristics affect sensory perception. Eighteen trained subjects participated in the study. Saliva was collected at rest and during three types of stimulation (odour, parafilm chewing and citric acid), and flow rates were determined. The collected saliva was analyzed for protein concentration, buffer capacity, mucin level and α-amylase activity. The salivary components measured in this study varied considerably among subjects, but also within subjects as a result of different means of stimulation. Variations in salivary components were correlated with sensory perception of a number of flavour, mouth feel and after feel attributes in the semi-solids mayonnaise and custard dessert. Total protein concentration and α-amylase activity were observed to correlate most strongly with texture perception. © 2006 Elsevier Ltd. All rights reserved.

The aim of this study is to determine the release of lysozyme from oxidized starch microgels and subsequently test its antimicrobial activity. The gels are made of oxidized potato starch polymers, which are chemically cross-linked by sodium trimetaphosphate (STMP). The microgel is negatively charged and interacts with positively charged lysozyme by electrostatic attraction. Application of the lysozyme-containing starch particles to environments contaminated with microbes, may lead to hydrolysis of the starch by microbial enzymes. As a result, lysozyme is released in the environment where it inhibits microbial growth. In this study, first bacteria were screened for amylase production and lysozyme sensitivity. Then, the bacteria were mixed with empty gel particles (i.e., without lysozyme) in a Nutrient Broth liquid medium to test whether the bacteria that can produce amylase are also able to degrade oxidized starch gel. Subsequently the amylase-producing lysozyme sensitive bacteria, Bacillus licheniformis 7558 and Bacillus subtilis 168, were selected for further quantification of the antimicrobial activity of the gel-lysozyme particles after incubation with these bacteria in Nutrient Broth liquid suspensions. The results prove that the starch microgel has a potential as antimicrobial carrier targeting amylase-producing and lysozyme-sensitive bacteria. The controlled antimicrobial delivery for inactivating undesired microorganisms may find applications in food related systems, where amylase-producing bacteria may be abundantly present. © 2011 Elsevier Ltd.

Microbacterium aurum strain B8.A was isolated from the sludge of a potato starch-processing factory on the basis of its ability to use granular starch as carbon- and energy source. Extracellular enzymes hydrolyzing granular starch were detected in the growth medium of M. aurum B8.A, while the type strain M. aurum DSMZ 8600 produced very little amylase activity, and hence was unable to degrade granular starch. The strain B8.A extracellular enzyme fraction degraded wheat, tapioca and potato starch at 37 °C, well below the gelatinization temperature of these starches. Starch granules of potato were hydrolyzed more slowly than of wheat and tapioca, probably due to structural differences and/or surface area effects. Partial hydrolysis of starch granules by extracellular enzymes of strain B8.A resulted in large holes of irregular sizes in case of wheat and tapioca and many smaller pores of relatively homogeneous size in case of potato. The strain B8.A extracellular amylolytic system produced mainly maltotriose and maltose from both granular and soluble starch substrates; also, larger maltooligosaccharides were formed after growth of strain B8.A in rich medium. Zymogram analysis confirmed that a different set of amylolytic enzymes was present depending on the growth conditions of M. aurum B8.A. Some of these enzymes could be partly purified by binding to starch granules. © 2011 The Author(s).

A description is given of the solid-state fermentation of wheat bran by Trichoderma reesei QM9414 at constant temperature and relative humidity. Glucosamine, the oxygen consumption rate (OCR), the carbon dioxide production rate (CPR), changes in wheat bran composition and the production of four enzymes were measured during 125 h of fermentation. A C balance was set up between CO2 production, based on CPR measurements, CO2 production as expected on the basis of substrate composition changes and substrate elemental composition in combination with dry-matter weight loss. Glucosamine was used as the measure of biomass. The results indicate that the glucosamine content of fungi in liquid culture cannot be used to estimate the biomass content in solid-state fermentations. Using glucosamine, correlations between fungal growth and respiration kinetics could only partly be described with the linear-growth model of Pirt. A decline in OCR and CPR started the moment the glucosamine level was 50% of its maximum value. After the glucosamine level had reached its maximum OCR and CPR continued to decline. The activities of xylanase and protease are linearly related to the glucosamine level. No clear correlations between glucosamine and carboxylmethylcellulose-hydrolysing enzyme activity and amylase activity were found.

The effect of adding saliva or a saliva-related fluid (α-amylase solution and water) to custard prior to ingestion on the sensory ratings of odour, flavour and lip-tooth-, mouth- and after-feel sensations was investigated. Saliva had previously been collected from the subjects and each subject received his/her own saliva. Sixteen subjects from a trained panel assessed 17 flavour and texture attributes of soy- and milk-based custard desserts. Immediately prior to administration, two different volumes (0.25 and 0.5 ml) of three different saliva-related fluids (saliva, α-amylase solution and water) were added to the product. The added volumes represented an approximately 33% and 66% increase of the volume of saliva present in the mouth during ingestion. The results show that addition of a fluid affected the mouth-feel attributes of melting, thickness and creamy. Melting was the only attribute on which the type of fluid had an effect, where saliva elicited a stronger melting effect than the α-amylase solution and water. The volume of the added fluid affected a number of attributes (thick and creamy mouth-feel and fatty after-feel). It can be concluded that in general the sensory attributes of semisolids were relatively stable. Mouth- and after-feel sensations were partly affected, while odour, flavour and lip-tooth-feel sensations were not affected by an increase in volume of saliva or other saliva-related fluid during ingestion. © 2003 Elsevier Science Inc. All rights reserved.

Instrumentally measured in vitro friction in semi-solid foods was related to oral texture sensations. Increased fat content resulted in lower sensations of roughness, higher sensations of creaminess, and lower friction, suggesting that lubrication is the mechanism by which fat affects oral texture in low fat foods. Starch breakdown by salivary amylase in low fat foods resulted in reduced friction, possibly through the release of fat from the starch food matrix, and the migration of fat to the surface of the bolus where it becomes available for lubrication. No evidence was found that salivary mucins or salivary viscosity play a role in lubrication. Astringent sensations may be related to reduced lubrication and increased friction caused by particles, either resulting from precipitation of salivary protein rich proteins or from flocculation of dead cells. © 2004 Elsevier Ltd. All rights reserved.

Introduction: Recent studies have shown that even low exposure levels to flour dust and related allergens can cause severe respiratory symptoms. In The Netherlands the Dutch government and responsible branch organizations [from bakeries (traditional & industrial), flour mills and bakery ingredient producers] signed a covenant to reduce exposure to flour dust and decrease the prevalence of work-related occupational airway disease. This paper describes a sector wide survey to measure exposure to flour dust, wheat allergens and fungal α-amylase. The results are being used to underpin various elements of the covenant. Methods: A dataset containing 910 personal measurements was compiled from four field studies containing information on exposure and potential determinants. The dataset represents a baseline estimate of exposure for four major flour processing sectors in The Netherlands. Exposure models for all sectors and agents were generated, based on job, tasks and company size, taking into account worker and company as random effect components. Use of control measures and, where possible, their effect were evaluated. Results: Flour dust and enzyme exposures vary strongly between sectors. The job performed and specific tasks were identified as important determinants of exposure. The number of identified control measures during walk-through surveys, and their effectiveness in reduction of dust exposure was generally limited. The exposure models explained significant exposure variability between companies and workers but performed poorly in explaining day to day differences in exposure. Discussion: The dataset serves as a baseline estimate and will be compared with a post intervention survey in the near future. The information obtained on control measures can be used to optimize the intervention scenarios that will be implemented in the different sectors by external occupational hygienists. The predictive exposure models will provide a relevant measure of average personal exposure that will be used in the sector wide health surveillance system. © The Author 2007. Published by Oxford University Press on behalf of the British Occupational Hygiene Society. Chemicals / CAS: amylase, 9000-90-2, 9000-92-4, 9001-19-8; Allergens; Dust; alpha-Amylase, 3.2.1.1

Amylomaltases are glycosyl hydrolases belonging to glycoside hydrolase family 77 that are capable of the synthesis of large cyclic glucans and the disproportionation of oligosaccharides. Using protein crystallography, we have generated a flip book movie of the amylomaltase catalytic cycle in atomic detail. The structures include a covalent glycosyl enzyme intermediate and a covalent intermediate in complex with an analogue of a cosubstrate and show how the structures of both enzyme and substrate respond to the changes required by the catalytic cycle as it proceeds. Notably, the catalytic nucleophile changes conformation dramatically during the reaction. Also, Gln-256 on the 250s loop is involved in orienting the substrate in the +1 site. The absence of a suitable base in the covalent intermediate structure explains the low hydrolysis activity. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.

Introduction: We evaluated the effect on exposure of an intervention programme, which focused on risk education and providing information on good work practices. This intervention programme was enrolled as part of a Dutch covenant in the flour processing industry (industrial bakeries, flour mills, ingredient producers). Methods: Data from several measurement surveys collected pre- and post-intervention were used to evaluate changes in exposure over time. All datasets contained personal measurements analysed for flour dust and fungal α-amylase contents, and contextual information was available on process characteristics, work practice, and use of control measures. Results: Changes in exposure over time varied substantially between sectors and jobs. For bakeries a modest downward annual trend of 22% was found for flour dust and 28% for amylase. For flour mills the annual trend for flour dust was 212%; no significant trend was observed for amylase. For ingredient producers results were generally non-significant but indicated a reduction in flour dust exposure and increase in fungal a-amylase exposure. Modest increase in use of control measures and proper work practices were reported in most sectors, especially the use of local exhaust ventilation and decreased use of compressed air. Conclusions: The magnitude of the observed reductions in exposure levels indicates that the sector-wide intervention strategy implemented during the covenant period had a limited overall effect. This indicates that a more rigorous approach is needed to substantially decrease the exposure levels to flour dust and related allergens and, respectively, the prevalence of associated occupational diseases.

To study the role of the lumenal binding protein (BiP) in the transport and secretion of proteins, we have produced plants with altered BiP levels. Transgenic plants overexpressing BiP showed dramatically increased BiP mRNA levels but only a modest increase in BiP protein levels. The presence of degradation products in BiP overproducers suggests a regulatory mechanism that increases protein turnover when BiP is abundant. Antisense inhibition of BiP synthesis was not successful, demonstrating that even a minor reduction in the basal BiP level is deleterious to cell viability. Overexpression of BiP leads to downregulation of the basal transcript levels of endogenous BiP genes and greatly reduces the unfolded protein response. The data confirm that BiP transcription is regulated via a feedback mechanism that involves monitoring of BiP protein levels. To test BiP activity in vivo, we designed a functional assay, using the secretory protein α-amylase and a cytosolic enzyme as a control for cell viability. During tunicamycin treatment, an overall reduction of α-amylase synthesis was observed when compared with the cytosolic marker. We show that the tunicamycin effect is due to the depletion of BiP in the endoplasmic reticulum because coexpressed BiP alone is able to restore efficient α-amylase synthesis. This is a novel assay to monitor BiP activity in promoting secretory protein synthesis in vivo.