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Spent coffee grounds (SCGs) are a good source of chlorogenic acid (CGA), which can be hydrolyzed to quinic acid (QA) and caffeic acid (CA). These molecules have antioxidant and neuroprotective capacities, benefiting human health. The hydrolysis of CGA can be done by biotechnological processes, such as solid-state fermentation (SSF). This work evaluated the use of SSF with Aspergillus sp. for the joint release of the three molecules from SCGs.Hydroalcoholic extraction of the total phenolic compounds (TPCs) from SCGs was optimized, obtaining 28.9 ± 1.97 g gallic acid equivalent (GAE) kgSSF represents an alternative to produce extracts with different compositions and, consequently, different antioxidant capacities, which is a potentially attractive fermentation process for different applications. © 2022 Society of Chemical Industry.

The intensification of processes is essential for the sustainability of the biorefinery concept. Enzyme catalysis assisted by ultrasound (US) may offer interesting opportunities in the agri-food sector because the cavitation effect provided by this technology has been shown to improve the efficiency of the biocatalysts. This review presents the recent advances in this field, focused on three main applications: ultrasound-assisted enzymatic extractions (UAEE), US hydrolysis reactions, and synthesis reactions assisted by US for the manufacturing of agri-food produce and ingredients, enabling the upgrading of agro-industrial waste. Some theoretical and experimental aspects of US that must be considered are also reviewed. Ultrasonic intensity (UI) is the main parameter affecting the catalytic activity of enzymes, but a lack of standardization for its quantification makes it unsuitable to properly compare results. Applications of enzyme catalysis assisted by US in agri-foods have been mostly concentrated in UAEE of bioactive compounds. In second place, US hydrolysis reactions have been applied for juice and beverage manufacturing, with some interesting applications for producing bioactive peptides. In last place, a few efforts have been performed regarding synthesis reactions, mainly through trans and esterification to produce structured lipids and sugar esters, while incipient applications for the synthesis of oligosaccharides show promising results. In most cases, US has improved the reaction yield, but much information is lacking on how different sonication conditions affect kinetic parameters. Future research should be performed under a multidisciplinary approach for better comprehension of a very complex phenomenon that occurs in very short time periods.

Galacto-oligosaccharides (GOS) are short oligosaccharides chains containing several galactoses and one terminal glucose. Raw GOS are mixtures containing oligosaccharides, unreacted lactose and monosaccharides; hence nanofiltration is an alternative for product purification. However, poor membrane selectivity towards separation of lactose from GOS is the main drawback. So, in order to improve the purification of enzymatically-produced GOS by nanofiltration, the incorporation of a previous lactose hydrolysis step, to convert the remaining lactose into monosaccharides, is proposed. The purification of raw and hydrolyzed raw GOS was evaluated using two nanofiltration polymeric membranes (Synder NFG and TriSep XN45) at different transmembrane pressures (8–30 bar) in a stirred dead-end cell. Results indicate that the incorporation of the lactose hydrolysis step allows increasing GOS retention and monosaccharides and lactose removal, improving GOS purification. Best operational conditions for hydrolyzed raw GOS nanofiltration were obtained with the TriSep XN45 membrane at 20 bar, 45 °C and 1500 rpm.

A proteolytic susceptibility index was proposed to evaluate the reaction performance of different food by-products with subtilisin. Whey, salmon muscle and feather keratine were hydrolyzed at the same peptide bond concentration at 50 °C and pH 8.0 with different subtilisin concentrations. The logarithmic equation P = 1/b ln(abt+1) was fitted to estimate the kinetic constants a and b. The a/b ratio was proposed as a proteolytic susceptibility index, which was correlated with the chemical structure and conformation of protein sources in increasing order of feather keratin, salmon muscle and whey proteins with corresponding a/b values of 0.1, 8.2 and 14.4 mM2/min, respectively. The methodology proposed in this work can be used to evaluate the proteolytic susceptibility of different protein by-products to different proteases and to evaluate the changes in proteolytic susceptibility after treatment.

Variations in the quality of clarified apple juices subjected to a lab-scale concentration process were assessed. The processing conditions were similar to those used in an industrial three-effects evaporator: 85°C for 25 minutes during the first effect (E1), 75°C for 13 minutes during the second effect (E2) and 58°C for 20 minutes for the third effect (E3). The following parameters were measured at different times from samples of the three effects: Brix content, absorbance spectrum (200 to 670 nm), processing temperature, viscosity, pH, activity of water (Aw) and 5-hydroxymethylfurfural (HMF) concentration (measured via HPLC). The highest increase in HMF occurred during E3, reaching a concentration of 22.26 ± 1.32 mg/kg, with a Brix content of 65.93 ± 0.95. Such HMF concentrations were just below the European Food Regulation Standards. An increase of HMF correlated well with a decrease of Aw and pH. Absorbance spectral values within the UV range increased with increasing processing time, reflecting the non-enzymatic browning effect. Additionally, at measurements above 50° Brix, the effect of temperature and the Brix content had a significant effect on the viscosity. Partial least squares (PLS) regression and pre-processing data under an Orthogonal signal correction OSC + Wavelets (DWT) scenario yielded a multivariate calibration model that accurately predicted the appearance of HMF during the concentration process (R2 0.947). The proposed methodology may serve as an early warning against a critical threshold of HMF by offering a simple and fast physic-chemical analysis conventionally measured by most of the juice processing industry.

Limiting flux (JL) determination is a critical issue for membrane processing. This work presents a modified exponential model for JL calculation, based on a previously published version. Our research focused on skim milk microfiltrations. The processing variables studied were the crossflow velocity (CFV), membrane hydraulic diameter (dh), temperature, and concentration factor, totaling 62 experimental runs. Results showed that, by adding a new parameter called minimum transmembrane pressure, the modified model not only improved the fit of the experimental data compared to the former version (R2 &gt, 97.00%), but also revealed the existence of a minimum transmembrane pressure required to obtain flux (J). This result is observed as a small shift to the right on J versus transmembrane pressure curves, and this shift increases with the flow velocity. This fact was reported in other investigations, but so far has gone uninvestigated. The JL predicted values were correlated with the Reynolds number (Re) for each dh tested. Results showed that for a same Re, JL increased as dh decreased, in a wide range of Re within the turbulent regime. Finally, from dimensionless correlations, a unique expression JL = f (Re, dh) was obtained, predicting satisfactorily JL (R2 = 84.11%) for the whole set of experiments

A direct linear plot was applied to estimate kinetic constants using the product&rsquo, s competitive inhibition equation. The challenge consisted of estimating three kinetic constants, Vmax, Km, and Kp, using two independent variables, substrates, and product concentrations, in just one stage of mathematical treatment. The method consisted of combining three initial reaction rate data and avoiding the use of the same three product concentrations (otherwise, this would result in a mathematical indetermination). The direct linear plot method was highly superior to the least-squares method in terms of accuracy and robustness, even under the addition of error. The direct linear plot method is a reliable and robust method that can be applied to estimate Kp in inhibition studies in pharmaceutical and biotechnological areas.

Promover calidad de la educación universitaria es fundamental para el desarrollo, sin embargo sostenerlo solo desde currículos tecnificados, es olvidar el valor que agrega lo emocional en la formación de personas con responsabilidad social.El presente artículo reflexiona cómo la incorporación de lo emocional como un eje curricular, favorece la efectividad y profundidad de los aprendizajes, aunque su manejo en el aula obligue a un cambio en la relación profesor-alumno.Una experiencia de aula, basado en lo propuesto por Krathwohl confirmó mejoras en la disposición al trabajo, conductas y resultados en los grupos. Esto, en concordancia con la literatura, corrobora que una educación que prioriza competencias genéricas, consigue mayor desarrollo y productividad, formando profesionales que contribuirán mejor al desarrollo económico de su comunidad.

Nanoparticles with antimicrobial properties are used in thousands of nano-enabled consumer products. Therefore, it is important to understand the response mechanisms of bacteria that are exposed to these nanoparticles at different conditions. Moreover, it is necessary to evaluate possible microbial adaptation mechanisms. In our study, Escherichia coli K-12 MG1655 (E. coli) were grown continuously in bioreactors at two specific growth rates (0.1 h−1 and 0.2 h−1) and then exposed to chronic concentrations of casein-coated silver nanoparticles (AgNPs) [1 mg L−1] for about 180 generations. After initiating the injection of AgNPs, the results showed a change in growth kinetic parameters between non-exposed and exposed systems. Maximum yield (Ymax) decreased by 33%, while the maintenance coefficient (ms) increased by 52%. This evidence was indicating the versatility of the culture to growth in the exposed conditions and even the ability to achieve a new stationary state. However, the adaptation was achieved at a metabolic cost. Comparing the concentration and composition of extra-cellular substances that were produced showed differences between the control and exposed conditions, and also between the exposed systems in the two growth conditions. In the AgNPs-exposed bioreactor (EB) growing at 0.1 h−1, AgNPs–ES complexes showed that the ratio of the area representing β-sheets to the area representing α-helix proteins was 2.4, which implies the formation of a protein corona, while at an exposed growth rate of 0.2 h−1 this ratio was

A convective drying process was optimized as strategy to produce dehydrated ingredients with high antioxidant capacity; using Hass avocado byproducts (peels and seeds). Studied processing variables were: temperature (45 °C–75 °C), air-flow (0.8 m/s to 1.8 m/s) and loading density (1 kg/m2 to 3 kg/m2). The response variables were Total Phenol Content (TPC) and Antioxidant Capacity (DPPH). Drying kinetic analysis revealed that seeds had higher water diffusivity than peels, but the latter showed shorter drying times. Multiple optimization routines allowed maximizing simultaneously DPPH and TPC. Thus, 62.82% and 54.81% of the initial TPC was retained in dehydrated peels and seeds, respectively. Sorption isotherms for both dehydrated byproducts showed that avocado seeds were more hygroscopic than peels, which was attributed to differences on their composition. This research has outlined a useful tool for the transformation of avocado wastes into storable commodities with high antioxidant properties which may have different food uses.

We provide initial rate data from enzymatic reaction experiments and tis processing to estimate the kinetic parameters from the substrate uncompetitive inhibition equation using the median method published by Eisenthal and Cornish-Bowden (Cornish-Bowden and Eisenthal, 1974; Eisenthal and Cornish-Bowden, 1974). The method was denominated the direct linear plot and consists in the calculation of the median from a dataset of kinetic parameters Vmax and Km from the Michaelis–Menten equation. In this opportunity we present the procedure to applicate the direct linear plot to the substrate uncompetitive inhibition equation; a three-parameter equation. The median method is characterized for its robustness and its insensibility to outlier. The calculations are presented in an Excel datasheet and a computational algorithm was developed in the free software Python. The kinetic parameters of the substrate uncompetitive inhibition equation Vmax, Km and Ks were calculated using three experimental points from the dataset formed by 13 experimental points. All the 286 combinations were calculated. The dataset of kinetic parameters resulting from this combinatorial was used to calculate the median which corresponds to the statistic estimator of the real kinetic parameters. A comparative statistical analyses between the median method and the least squares was published in Valencia et al. [3].

Ultrafiltration is a technique used for the separation and recovery of proteins according to their molecular weight. The efficiency of the process can be controlled by control of the operational parameters, which can affect the structure and functionality of proteins in the final product. The aim of this study was to evaluate how the ultrafiltration process using ceramic membranes affects the physicochemical and conformational characteristics of quinoa protein fractions at two pHs above the isoelectric point of quinoa protein extracts. The results showed differences in permeate flux, reaching a volume concentration factor of three at 600 min at pH 7.0 and 300 min at pH 9.5. Thus, pH was a very important factor to control flux and membrane fouling. Higher protein concentration in the concentrate were detected at pH 9.5 (10.4 ± 0.2 mg/mL), whereas at pH 7.0, only 7.7 ± 0.1 mg/mL of recovered protein was obtained. In addition, differences in quinoa zeta potential and amino acid composition were found for the two pHs. The ultrafiltration process considerably affected the spatial configuration of the protein at pH 7.0, with a structured α-helix for the concentrate. The concentrates showed lower denaturation enthalpy values than the initial and permeate fractions at both pHs, indicating greater structural modification as result of ultrafiltration. In conclusion, pH is a critical variable affecting the physicochemical and conformational characteristics of ultrafiltrated quinoa proteins. It is important to evaluate the impact of the changes from ultrafiltration on functional properties for the development of novel food ingredients.

Power ultrasound (US) transmits substantial amounts of small mechanical movements serving for particle detaching in membrane filtrations. This topic has been reviewed in recent years mainly focused on the mechanisms by which the flux is improved under specific processing conditions. US also been shown to improve food quality by changing physical properties and modifying the activity of enzymes and microorganisms. Surprisingly, limited information exists regarding on how the application of US results in terms of process and quality during membrane filtration of complex matrices such as liquid foods. This review highlights the recent advances in the use of US in membrane filtration processes focused in the manufacturing of foodstuffs and food ingredients, and perspectives of novel hybrid membrane-US systems that may be quite interesting for this field. The application of US in food membrane processing increases the flux, but the lack of standardization regarding to experimental conditions, make suitable comparisons impossible. In this sense, careful attention must be paid regarding to the ultrasonic intensity (UI), the membrane configuration and type of transducers and volume of the treated solution. Dairy products are the most studied application of US membrane food processing, but research has been mainly focused on flux enhancement; hitherto there have been no reports of how operational variables in these processes affect critical aspects such as quality and food safety. Also, studies performed at industrial scale and economical assessments are still missing. Application of US combined with membrane operations such as reverse osmosis (RO), forward osmosis (FO) and enzyme membrane bioreactors (EMBR) may result interesting for the production of value-added foods. In the perspective of the authors, the stagnation of the development of acoustic filtration systems in food is due more to a prejudice on this subject, rather than actual impedance due to the lack of technological development of transducers. This later has shown important advances in the last years making them suitable for tailor made applications, thus opening several research opportunities to the food engineering not yet explored.

During microfiltration, limiting (JL) and critical flux (JC) are essential. Using these concepts, the operational zones, have been established for flux (J) versus transmembrane pressure (ΔPT). However, the resistance model cannot be used for an accurate description of these operational zones. The aim of this work was to evaluate the application of an equation for process parameters’ determination during skim milk microfiltration. The exponential model, J = JL(1 – exp(−ΔPT/(ΔPT)C), allowed a direct determination of JL and the critical ΔPT ((ΔPT)C) and allowed the calculation of JC and the limiting ΔPT ((ΔPT)L). The effect of temperature, concentration factor, and cross-flow velocity over JL and (ΔPT)C were evaluated. For JL and (ΔPT)C, a good fitting was obtained (Radj2 = 98.12%; Radj2 = 97.83%, respectively). These results allow to predict the limiting and critical points for given values of the concentration factor, cross-flow velocity and temperature. Moreover, determination of the operational zones cou...

Experiments revealed the fouling nature evolutions along different electrodialysis (ED) trials, and how it disappears when current pulsation acts repetitively on the interfaces of ion-exchange membranes (IEMs). Fouling was totally controlled on the diluate side of cation-exchange membrane (CEM) by the repetitive pulsation frequency of the higher on-duty ratios applied. They created steady water splitting proton-barriers that neutralized OH(-) leakage through the membrane, decreasing the interfacial pH, and fouling of the concentrate side. The anion-exchange membrane (AEM) on the diluate side was similarly protected, but it was fouled once water splitting OH(-) generation became either intense enough or excessively weak. Interestingly, amorphous magnesium hydroxide (AMH) stemmed on the CEM-diluate side from brucite under intense water splitting OH(-) generation, and/or strong OH(-) leakage electromigration through the membrane. Water dissociation and overlimiting current regimes triggered drastic water molecule removal from crystal lattices through an accelerated cascade water splitting reaction. Also, amorphous calcium carbonate (ACC) appeared on CEM under intense water splitting reaction, and disappeared once intense OH(-) leakage was allowed by the water splitting proton-barrier dissipation. Our findings have implications for membrane fouling control, as well as for the understanding of the growth behavior of CaCO3 and Mg(OH)2 species on electromembrane interfaces.

In 1974, Eisenthal and Cornish-Bowden published the direct linear plot method, which used the median to estimate the Vmax and Km from a set of initial rates as a function of substrate concentrations. The robustness of this non-parametric method was clearly demonstrated by comparing it with the least-squares method. The authors commented that the method cannot readily be generalized to equations of more than two parameters. Unfortunately, this comment has been misread by other authors. Comments such as "this method cannot be extended directly to equations with more than two parameters" were found in some publications. In addition, recently, the most drastic comment was published: "this method cannot be applied for the analysis of substrate inhibition." Given all of these presumptions, we have been motivated to publish a demonstration of the contrary: the median method can be applied to more than two-parameter equations, using as an example, the substrate uncompetitive inhibition equation. A computer algorithm was written to evaluate the effect of simulated experimental error of the initial rates on the estimation of Vmax, Km and KS. The error was assigned to different points of the experimental design. Four different KS/Km ratios were analyzed with the values 10, 100, 1000 and 10,000. The results indicated that the least-squares method was slightly better than the median method in terms of accuracy and variance. However, the presence of outliers affected the estimation of kinetic constants using the least-squares method more severely than the median method. The estimation of KS using the median method to estimate 1/KS was much better than the direct estimation of KS, causing a negative effect of non-linearity of KS in the kinetic equation. Considering that the median method is free from the assumptions of the least-squares method and the arbitrary assumptions implicit in the linearization methods to estimate the kinetic constants Vmax, Km and KS from the substrate uncompetitive inhibition equation, the median method is highly superior to all published methods, including the non-linear regression by least squares. We concluded that the median method can be applied to the substrate uncompetitive inhibition equation and other equations with more than two parameters. In addition, as we can project, the median method is the most reliable and robust method for the estimation of kinetic parameters from enzyme kinetic models.

Statistical tools were used to analyze membrane fouling occurring during ultrafiltration (UF) of clarified grape juice. Experimental flux data were correlated to dead-end and crossflow filtration models. The UF experiments were performed at 30 and 40 °C for an 8-kDa multitubular ceramic membrane and also at 30 °C for a 1-kDa membrane to determine the effect of pore size. ANOVA was used for the statistical analysis of fluxes. The modified Kolmorov-Smirnov and the Shapiro-Wilk tests were used to evaluate the normality of the residuals obtained from each model, thus allowing validation or rejection of initial adjustments given by a simple R-square statistical test. Using the standard error of the estimate and the mean absolute error it was possible to identify the best model for each case. Differences in the permeate flux and fouling mechanisms between both temperatures and pore size were discussed.