Search

The consumption of two vital resources (e.g., water and energy) during home pasta cooking has so far received limited attention. The main focus of this work was to assess how the instrumental and sensory quality of cooked pasta is affected by the water-to-dried pasta ratio (WPR) using a model cooking system with three commercial brands of spaghetti. At WPR equal to 10 or 3 L/kg, the three sensory attributes of firmness, stickiness, and bulkiness, as well as the overall cooking quality, displayed no statistically significant sensitivity towards WPR. Cooked pasta water uptake, diameter, hardness at 90% deformation, and resilience were more influenced by the raw protein content of dried pasta than by WPR, while the cooking loss was regarded as approximately constant. Using the model cooking system that assured mild mixing of spaghetti to avoid their sticking during cooking, it would be possible to use 70% less cooking water and consume about 65% less electricity, the latter cutting significantly the climate change potential of home pasta cooking. [ABSTRACT FROM AUTHOR]

Beer foam is one of the first characteristics consumers visually perceive. Even if their opinions vary, generally, beer foam should be stable and long lasting. In this work, the conventional foam head retention method developed by Rudin (1957) was improved by resorting to three different automatic data acquisition systems. The first one made use of a mouse time tracking software offered at no cost. The second one was an Accurate Image Analysis system using a high-definition camera and a script written in MATLAB. Finally, the third one was an automatic low-cost image analysis (LCIA) system incorporating a Raspberry Pi single-board computer and a camera module (Raspberry Pi Foundation, UK). The latter was able not only to acquire the whole foam decay curve but also to fit the time course of the beer-foam interface position and extract the characteristic beer foam half-life ( t ). All the data acquisition systems yielded t values practically coincident at the probability level of 0.05, this confirming their substantial equivalence. Once the lager beer had been laced with increasing doses of a foam agent (i.e., tetrahydro-iso-α-acid) to enhance its foam persistence, the resulting foam half-life, as estimated using the above Rudin-based methods, was highly correlated ( r = 0.99) to the foam collapse time, as derived from the NIBEM Foam Stability Tester. Finally, thanks to the LCIA acquisition system developed here, the Rudin test might represent a fast, flexible, and cheaper alternative to the generally recommended but expensive NIBEM tester, as well as other commercial automated Rudin apparatuses. [ABSTRACT FROM AUTHOR]

In this work, the cross-flow microfiltration (CFMF) performance of a rough pale lager, produced in the industrial brewery Birra Peroni Srl (Rome, Italy), was assessed in a bench-top rig, equipped with a 0.8-μm ceramic hollow-fiber membrane module, to overcome the recognized inefficacy of back-flushing cleaning techniques in ceramic multi-channel monolithic modules. In total recycle CFMF trials, as the transmembrane pressure difference (TMP) was increased from 0.59 to 3.56 bar, the quasi-steady-state permeation flux ( J*) tended to a limiting value increasing with the cross-flow velocity ( v). To minimize the overall membrane surface to be installed for a prefixed permeate recovery, it was found to be expedient to operate at the aforementioned high cross-flow velocity and TMP of 3.56 bar, thus obtaining quite a high quasi-steady-state permeation flux (mean, μ = 173 L m h; standard deviation, sd = 7 L m h; number of observations, N = 12). The energy consumption per liter of permeate collected was found to be practically independent of the operating variables v and TMP selected ( μ = 55 W h L; sd = 2 W h L; N = 21). Yet, a permeate flux greater than 100 L m h was achieved on condition that TMP was greater than 2 bar and v varied from 4 to 6 m s. A few validation batch CFMF tests, carried out using pre-centrifuged, PVPP-stabilized, and cartridge-filtered rough pale lager at TMP = 3.56 bar, v = 6 m s, and 10 °C under a predefined CO backwashing program, resulted in an average permeation flux ( μ = 239 L m h; sd = 24 L m h; N = 2) by far greater than that (50-100 L m h) claimed at 0-2 °C by the three CFMF processes commercially available. Finally, it was proved the easy transferability of the lager beer clarification and stabilization process, previously developed in a single-tube membrane module, to a ceramic hollow-fiber membrane module industrially upscalable. [ABSTRACT FROM AUTHOR]

Orange peel waste was converted into ethanol by consecutive acid-catalyzed steam-explosion (ACSE), enzymatic saccharification, and fermentation with Saccharomyces cerevisiae F15. With the aim of increasing the concentration of fermentable sugars in the hydrolysate and to fully recycle the spent acid liquor as the suspending medium for saccharification, the technical feasibility of increasing the solid loading in the ACSE step from 160 to 480 g L was assessed. At high solid loading in the ACSE pretreatment (HSLAP), the solubilization degrees of polysaccharides were lower while those of potential inhibitors (e.g., acetic and formic acids and phenols) were generally higher than those found at low solid loading (LSLAP). However, residual solids from both solid loadings showed similar susceptibility to enzymatic saccharification (ES) in a 7-L stirred-tank reactor (STR) (cellulase, 12 FPU g cellulose; pectinase, 25 IU g dry matter; 72 h incubation at 50 °C). Fermentation was performed in a 1-L STR along five repeated batches with the first one being used to enable yeast proliferation. By using the hydrolysates arising from the HSLAP-ES combination, it was possible to rely on a fermentation medium with a 2.5-fold higher concentration of simple sugars and to double the ethanol concentration in the final beer to be distilled of. However, the higher content of inhibitory compounds in hydrolysates from HSLAP-ES than in the LSLAP-ES ones led to a reduction in the ethanol yield per unit substrate consumed (0.49 vs. 0.41 g g, respectively) and overall productivity (3.4 vs. 2.7 g h, respectively). [ABSTRACT FROM AUTHOR]

In this work, the crossflow microfiltration (CFMF) performance of different lots of lager beer, produced in a pilot scale at the Italian Brewing Research Centre (CERB, Perugia, Italy), was assessed in a bench-top plant, equipped with a 0.8-μm ceramic tubular membrane module, under constant crossflow velocity of 6 m s, transmembrane pressure difference of 3.74 bar, temperature of ~10 °C, and periodic CO backflushing. By feeding different beer samples (i.e., as such, precentrifuged (C), or pretreated with a commercial enzyme preparation to degrade the original arabinoxylans and β-glucans and then centrifuged (EC) to minimize the fouling contribution of yeast cells, aggregates, and polysaccharides), it was possible to increase the average permeation flux (expressed as mean value ± standard deviation) from 112 ± 13 to 199 ± 17 or 330 ± 22 L m h, respectively. Only when using the EC-pretreated beer specimens, the permeate turbidity at 20 °C approached the limiting one (<0.6 EBC unit) recommended by the European Brewery Convention standards. As expected, the permeate chill haze at 0 °C was generally higher than the above haze target. By submitting EC-pretreated beer seeded with 0.5 g L of regenerable polyvinylpolypyrrolidone (PVPP) to CFMF, it was possible to reduce the initial total polyphenol content by 30 % and permeate chill haze to 0.60 ± 0.01 EBC unit, but the average permeation flux fell to 84 ± 4 L m h. By performing sequentially EC pretreatments, PVPP stabilization, cartridge filtration, and CFMF, it was possible not only to re-enhance the average permeation flux at about 230 L m h near to those achievable with DE filters, but also to obtain a chill haze-free permeate ready for aseptic packaging. [ABSTRACT FROM AUTHOR]

In this work, laboratory-made green beers were produced using a commercial hopped malt extract and used to study their cross-flow microfiltration (CFMF) performance in a bench-top plant, appropriately designed and equipped with ceramic tubular membrane modules with nominal pore size of 0.4, 0.8, or 1.2 μm, under different values of the initial green beer turbidity ( H ≡ 0.7-61.9 European Brewery Convention (EBC) unit), feed superficial velocity ( v ≡ 2-6 m s), and transmembrane pressure difference (TMPD ≡ 0.97-4.73 bar) under constant temperature (~10 °C). Whatever the membrane pore size and rough beer turbidity, the minimum quasi-steady-state value of the overall membrane resistance $$ \left({\mathrm{R}}_{\mathrm{T}}^{*}\right) $$ was obtained at TMPD of 3 to 4 bar and v = 6 m s. The 0.8-μm pore membrane was selected for the loss in the permeate density, and color was limited, while the volumetric permeation flux was high enough. Then, it was used to assess a double logarithmic trend between the quasi-steady-state permeation flux ( J*) and beer turbidity with a limiting flux of 63 ± 6 L m h for H > 21 EBC units. Precentrifuged beer feeding resulted in 2.7- to 4.1-fold increase in J* with respect to the above limiting flux, provided that the haze level of rough beer had been reduced to 1.0 or 0.7 EBC unit, respectively. The cake filtration fouling mechanism was identified as the main reason for flux decline by analyzing mathematically the time course of both the experimental permeate volume and permeation flux data. By operating with the aforementioned clarified green beers at TMPD of 3.73 bar, v of 6 m s, and periodic CO backflushing, the average permeation flux (300-385 L m h) resulted to be from three to five times higher than that (80-100 L m h) at 0-2 °C claimed by the three commercial CFMF processes currently available. [ABSTRACT FROM AUTHOR]

In this work, the main features of electrodialytic (ED) desalting of microfiltered samples of a traditional soy sauce under constant electric current in the range of 1.25 to 6.5 A were quite well reconstructed using a mathematical model based on the Nernst-Planck equation. Amino nitrogen migration was characterised by a small effective transport number ( t = 0.070 ± 0.01), resulting in an average loss in amino nitrogen of about 30% whatever the electric current tested. The sodium chloride transport number ( t = 0.969 ± 0.05) and diffusion rate ( L ≈ 0), as well as the effective membrane surface area, essentially coincided with those previously established when dealing with concentrated model brines. On the contrary, there was a significant diversity in the water transport number ( t = 8.3 ± 0.1) and diffusion rate [ L = (6.9 ± 0.2) × 10 mol m s bar], as well as in the anion- and cation-exchange membrane resistances ( R = R ≈ 0.04 Ω). The experimental procedure and mathematical model described in this work may be recommended not only to optimise the ED desalination of soy sauce but also to generate a first-cut design for ED desalting of other natural seasonings. [ABSTRACT FROM AUTHOR]

In this work, the rheometrical behaviour of Tarocco orange fruit was assessed via stress-relaxation testing under constant engineering strain ( ε) in the range of 5-20% of the initial fruit height, each test being prolonged for 15 min and replicated 20 times. The time course of the experimental dimensionless relaxation modulus (G*) was typical of a viscoelastic solid and was reconstructed by considering two Maxwell elements in parallel to an elastic spring element. In a more restricted ε range (i.e. 5-10%), the dimensionless viscoelastic constants ( A) were found to be approximately constant, the elastic component responsible for the equilibrium residual stress representing about 42% of the initial relaxation modulus. After any orange fruit had been submitted to stress-relaxation testing and decompressed for 5 min, it exhibited a practically negligible mass loss (0.04 ± 0.03%) and a permanent volume contraction rising from 1.7 ± 1.0% to 3.0 ± 0.9% as ε was increased from 5% to 10%. Thus, by tasting the orange fruit firmness at ε ≤5%, fruit response, being of the viscoelastic type, is expected to give rise to nearly irrelevant deformations. [ABSTRACT FROM AUTHOR]

In this work, the effect of the weight ratio (YE/C) between transglutaminase (TGase) and sodium caseinate on the main engineering properties and microstructure of maltodextrin/caseinate/glycerol-based films, as well as crosslinking kinetics of the corresponding film-forming mixtures, was assessed. In the absence of TGase, the film forming solution did not jelly at all even after a 20-h gel cure experiment at 30 °C. As YE/C was increased from 0.5 to 8.3 mg/g, the gel point time exhibited quite a hyperbolic dependence on YE/C, whereas the pseudo-first order reversible kinetic constant rate of casein reticulation linearly increased with the enzyme concentration. Despite a certain data scattering, the initial and equilibrium complex shear moduli appeared to be practically constant and independent of YE/C. This finding was also extended to the mechanical and water barrier properties of the films under study. This was also indirectly confirmed by scanning electron microscopy, the film structure being quite compact, dense, and about free of air bubbles. In particular, their complex tensile modulus (E*) resulted to be not only independent of the cross-linking agent dosage but also interconvertible with the elastic modulus (E) determined in the quasi-static mode at an initial strain rate equal to the angular frequency. The water vapor permeability (WVP) for all the films examined was found to be extremely dependent on the water, desiccant, or Permatran-W standard methods used as well as on the difference in water activity (aW) at the inside (aWi=1.0 or 0) and outside (aWoi=0 or ~0.5) of the test cup. By maintaining aWoi=0 and aWoi=0.5, the Permatran-W method yielded practically constant WVP values (30±4 pg m-1 s-1 Pa-1) whatever the enzyme/ caseinate ratio used. Nevertheless, TGase appeared to decrease the water vapor permeability of not cross-linked maltodextrin--caseinate films. [ABSTRACT FROM AUTHOR]

The fermentation of potato starch by Schwanniomyces castellii IMAT 3754 was studied at differentsubstrate concentrations, pH values, and nutrient supplementation in a shaken-flask fermenter in a composite design experiment. The experimental biomass yields were fitted to the only two significant factors ('substrate inhibition' and 'nutritional' factors) with a mean percentage error smaller than 10% by means of multiple regression analysis. The optimal conditions for maximum cell yield were first established experimentally, and then applied to other starchy materials, such as soluble maize starch, maize starch, tapioca and rice flour. They were then scaled-up in a laboratory fermenter, thus allowing a preliminary kinetic analysis of this fermentation process to be performed. [ABSTRACT FROM AUTHOR]

The fermentation of grape must by Candida utilis ISS 28 was studied at different substrate concentrations, pH values, and nutrient supplementation in a shaken-flask fermenter, by using a composite design experiment. The experimental biomass yields were fitted to the only statistically significant factors with a mean standard error less than 8%, by using multiple regression analysis. Optimal conditions for maximum cell yield were established by plotting a series of loci at constant biomass yield and then verified experimentally, thus confirming the remarkable accuracy of the model [ABSTRACT FROM AUTHOR]

The scale-up of a whey fermentation by Kluyveromyces fragilis was carried out in order to reproduce on a larger scale (100-l fermenter) the results obtained on a smaller scale (15-l fermenter). Using a standard procedure for inoculum development and medium pasteurization, the effects of mixing and lactose concentration on yeast growth, lactose consumption, COD reduction and dissolved oxygen have been studied. The most successful operation for this fermentation was found to be associated with high stirring rates and low lactose concentrations, since the process was controlled by both oxygen and lactose concentrations. [ABSTRACT FROM AUTHOR]

The biomass yields (y) and COD reduction efficiencies (η) of a whey fermentation by Kluyveromyces fragilis were studied in a 100-1 fermenter at various stirrer speeds and lactose concentrations, and compared to those obtained in 10-1 and 15-1 fermenters at constant values of the oxygen transfer coefficient (ka) and air velocity. The empirical models previously constructed by using the 15-1 fermenter data could be used to predict the yields on the other scales by calculating for each run the 15-1 fermenter which would provide the same oxygen transfer coefficient measured by the sulphite method on each fermenter under study. To make this model independent of stirrer speeds used in each generic fermenter, the effect of aeration and mixing was incorporated into an overall parameter (ka) and the values of y and η were correlated only with temperature, lactose level and k a, since these variables were approximately orthogonal. The validity of this model was finally checked against the yields reported by Wasserman et al. (1961) in a 6-m fermenter, thus confirming the capability of the model to provide a reliable basis for further scale-up on the production scale. [ABSTRACT FROM AUTHOR]

The efficiency of Chemical Oxygen Demand (COD) reduction η in the fermentation of whey by Kluyveromyces fragilis IMAT 1872 was studied at various temperatures, lactose concentrations, air dilution ratios and stirring speeds. Their effects on the biomass yield (y) has been determined previously (Moresi et al. in press). Two different optimal sets of these variables were found according to whether the objective was the production of cell mass or the reduction of COD. The two sets were then compared to establish a strategy for the industrial development of this fermentation process. The experimental efficiencies of COD removal were submitted to analysis in a composite design. Only the first two principal axes (i.e., the 'oxygen transfer coefficient' factor and the 'stripping' factor) of canonical analysis were found to be significant by an F-test. Therefore, the observations were fitted with a quadratic expression by using only these factors: the mean standard error was less than 6%. The yield of cells, expressed as g of dried cells/g of COD removed, varied in this fermentation, but this parameter may be particularly useful for analyzing and optimizing any fermentation process when the culture medium is a mixture of carbohydrates or the main substrate is fully utilized during the initial stages of fermentation. [ABSTRACT FROM AUTHOR]

The fermentation of whey by Kluyveromyces fragilis IMAT 1872 was studied in a 15-l jar fermenter to assess the influence of temperature, lactose concentration, aeration and agitation on the biomass yield. Optimization of the operating parameters resulted in a 57.2% yield. The observations were analyzed in a 'composite' design. Canonical analysis and an F-test showed that only the first two principal axes (i.e., 'oxygen transfer coefficient' and 'lactose inhibition' factors) of the system under study were significant. Therefore, the observations were fitted to a quadratic expression, by using only these factors: 86% of the data fall within a 10% deviation band. This empirical model allowed the formulation of an operating strategy to select the set of conditions yielding the maximum value of biomass. [ABSTRACT FROM AUTHOR]

Factor analysis was applied to fermentation of whey by Kluyveromyces fragilis IMAT 1872 allowing a screening of the experimental variables (temperature, pH, ammonium sulphate, potassium phosphate, yeast extract and lactose concentration and fractional filling of the flasks). The lactose level and the ratio of the solution and flask volumes have a marked effect on the biomass yield, as they control the oxygenation level of the culture media. Nutritional supplementation and environmental conditions have only a marginal effect on yield in this fermentation process. The best fit obtained by regression analysis between the biomass yield and the first principal component of factor analysis (oxygenation factor) showed a linear relationship: 64% of the data fall within a 25% deviation band. [ABSTRACT FROM AUTHOR]

A composite design technique was used to optimize the fermentation of whey by Kluyveromyces fragilis IMAT 1872. The experimental variables (temperature T, salts NP, yeast-extract YE and lactose level L), but not pH, were found to be significant at a level of 5%. The optimal operating conditions were determined (T=36.4°C, pH=5.1, NP=0.47% w/v, YE=0.114% w/v, and L=24.75 g/l). Temperature and lactose level exhibited a great influence on the biomass yield about the stationary point. Canonical analysis showed that these variables are not mutually independent. The optimal conditions will be used as starting point for a factorial design on a jar fermenter. [ABSTRACT FROM AUTHOR]

Gluconic acid production from corn starch hydrolysates by immobilised mycelia of Aspergillus niger was studied in a laboratory-scale stirred fermentor at different concentrations of glucose ( S) and dissolved oxygen (DO) in the culture broth. Its evolution was simulated quite well by applying the same unstructured model set up in previous experiments using stirred and airlift fermentors. In particular, increasing S in the range 70-160 g/l, although uninfluential upon the yield coefficient, resulted in an exponential decrease in the gluconic acid formation rate constant. Nevertheless, the greater the oxygen transfer rate used in the fermentor, the smaller the inhibitor effect of the higher concentrations of glucose on gluconate productivity became. This was achieved by enriching the inlet air with pure oxygen so as to maintain the DO level above 75% saturation throughout the fermentation. [ABSTRACT FROM AUTHOR]

Cyclic fed-batch plus batch polygalacturonase production by Aureobasidium pullulans in slurry fermentation systems using raw orange peel as substrate was studied in a 3-dm stirred fermentor by setting the main operating variables ( T=297°K; pH=3.2; OP=3% w/v; n=700 rpm) to optimal values determined previously. In this way, it was possible to stabilize enzyme excretion at 130-140 VU cm. The time course of this fermentation process in terms of cell growth, substrate consumption and enzyme synthesis was reconstructed with a mean standard error less than 10%, by applying an unstructured model set up in a batch run and further refined in a series of cyclic fed-batch plus batch operations. In particular, the enzyme formation rate was related to the effect of reducing sugars as inhibitors at higher concentrations and as activators at lower levels by using an exponential equation. Moreover, the consumption rate of reducing sugars was found to be linearly related to the cell growth rate, its specific date being of pseudo-first order with respect to the reducing sugar concentration. [ABSTRACT FROM AUTHOR]

A whey fermentation by Kluyveromyces fragilis was scaled-up to a 1000-dm stirred fermentor, by varying the stirrer speed, the air-flow rate and the initial concentration of lactose. Its evolution was simulated by applying the same unstructured model (consisting of a microbial specific growth rate of pseudo-first order with respect to the COD concentration and constant biomass yield per unit COD removed) set up in previous experiments using 8- to 80-dm fermentors. Despite the great scale-up ratios, very different operating conditions, and geometric dissimilarity, a series of empirical regressions previously developed allowed approximate, but acceptable prediction of the stoichiometric and kinetic coefficients of the above mathematical model, thus confirming the capability of this model to provide a reliable basis for further scale-up of this fermentation process to a production scale. [ABSTRACT FROM AUTHOR]

The growth behaviour of Fusarium avenaceum (Sect. Roseum Wr.) in slurry fermentation systems using untreated orange peel as substrate was studied in a laboratory-fermenter scale to reproduce the results obtained in a shakenflask fermenter. The eventual effect of impeller speed on mechanical disruption of mycelial hyphae was then assessed by determining mycelial growth, total reducing sugars consumption, TOC reduction, carbon dioxide evolution and oxygen absorption rates. In particular, the main biomass yield coefficient, as well as the apparent specific growth rate, appeared to be independent of the impeller speed, at least within the experimental range of 450 and 900 min (equivalent to peripheral impeller speeds of 3.8-7.5 m sec. [ABSTRACT FROM AUTHOR]

The growth behaviour of Memnoniella echinata and Fusarium roseum was examined in slurry fermentation systems using untreated orange peel as substrate. A composite experiment was then designed to study the effect of orange peel initial concentration and the effect of the nitrogen: peel ratio on crude protein yidld ( Y) and protein enrichment ( Z) of the final biomass. The more concentrated the peel slurry, the greater the substrate inhibitory effect on microbial growth becomes. Finally, multiple regression technique allowed both the experimental values of Y and Z to be reconstructed with mean percentage errors smaller than 4% and 8%, respectively, and the optimal operating strategy for such SCP production process to be determined. [ABSTRACT FROM AUTHOR]

Fungal strains naturally occurring on the wood and leaves of the salt-excreting desert tree Tamarix were isolated and characterized for their ability to produce cellulose- and starch-degrading enzymes. Of the 100 isolates, six fungal species were identified by ITS1 sequence analysis. No significant differences were observed among taxa isolated from wood samples of different Tamarix species, while highly salt-tolerant forms related to the genus Scopulariopsis (an anamorphic ascomycete) occurred only on the phylloplane of T. aphylla. All strains had cellulase and amylase activities, but the production of these enzymes was highest in strain D, a Schizophyllum-commune-related form. This strain, when grown on pretreated Tamarix biomass, produced an enzymatic complex containing levels of filter paperase (414 ± 16 IU/ml) that were higher than those of other S. commune strains. The enzyme complex was used to hydrolyze different lignocellulosic substrates, resulting in a saccha-rification rate of pretreated milk thistle (73.5 ± 1.2 %) that was only 10 % lower than that obtained with commercial cellulases. Our results support the use of Tamarix biomass as a useful source of cellulolytic and amylolytic fungi and as a good feedstock for the economical production of commercially relevant cellulases and amylases. [ABSTRACT FROM AUTHOR]