Effect of fortification with CaCO3 nanoparticles obtained from eggshell on the physical and sensory characteristics of three food matrices.

Food fortification has attracted interest in recent years, due to the understanding that micronutrient deficiency is one of the causes of the global burden of disease, and that food fortification aims to prevent or correct a demonstrated deficiency of one or more nutrients in a specific population or population groups. Nutritional value is an important concern regarding fortification and new product development. However, people are not willing to sacrifice the organoleptic characteristics of food products. Therefore, the effect of CaCO3 nanoparticles (NPs-CaCO3) and commercial CaCO3 on the physical and sensory properties of three food matrices (cookies, fruit rolls and dairy desserts) was evaluated. A texture analysis was performed on cookies and fruit rolls; a viscosity analysis on dairy desserts; and a color analysis and sensory profile on the three matrices. The results showed that both types of calcium increase hardness in fortified biscuits and fruit rolls but, in the latter case, commercial calcium caused a higher increase in hardness (p < 0.05). Viscosity was higher in the desserts with NPs. Color presented significant changes in all the fortified matrices. These findings demonstrated that Ca-NPs are a good strategy for food fortification compared to commercial calcium carbonate, as fortification with high levels of calcium is a challenge for the food industry due to its effects on the product. The results showed that, in the matrices with commercial calcium, the changes were more evident, while the matrices fortified with Ca-NP have a better sensory response than commercial Ca, with a higher level of acceptance by the judges. Therefore Ca-NPs can be considered to be a good source of calcium for food product fortification that causes a slight effect on physical and sensory properties.

l-Threonine production from whey and fish hydrolysate by E. coli ATCC® 21277TM.

In this work production of l-threonine by Escherichia coli ATCC® 21277™ has been studied using a mixture of alternative low-cost substrates, which are recognized to be a major pollution problem. Whey was used as the primary carbon source, whereas Red Tilapia (Oreochromis sp.) viscera hydrolysates constituted the nitrogen source. A Box-Behnken Design was used for optimizing l-threonine and biomass production, using temperature and glucose, whey, and Red Tilapia (Oreochromis sp.) viscera hydrolysate contents as factors. Results indicate that biomass production is affected by the concentration of hydrolysate and temperature. On the other hand, l-threonine production is affected by concentration of whey, hydrolysate, and temperature. In this context, it was possible to maximize l-threonine production, but with a detriment on biomass production. The optimal conditions for biomass and l-threonine maximization (after 24 h) were identified and validated experimentally, resulting in biomass and l-threonine production of 0.767 g/L and 0.406 g/L, respectively. This work has shown the technical feasibility of using whey and Red Tilapia (Oreochromis sp.) viscera hydrolysates for the production of l-threonine by E. coli ATCC® 21277TM. Finally, the complications associated to the use of these low-cost complex substrates for the production of l-threonine by E. coli, suggest that more in detail studies (i.e. at the metabolic level) are required in order to propose strategies to increase the process productivity, before its scale up. This is a first step in our long-term goal of developing a production process for i) dealing with the pollution problems caused by those wastes, and ii) strengthen the milk and fish industries which are important poles of the Colombian economy.

System metabolic engineering of Escherichia coli W for the production of 2-ketoisovalerate using unconventional feedstock.

Replacing traditional substrates in industrial bioprocesses to advance the sustainable production of chemicals is an urgent need in the context of the circular economy. However, since the limited degradability of non-conventional carbon sources often returns lower yields, effective exploitation of such substrates requires a multi-layer optimization which includes not only the provision of a suitable feedstock but the use of highly robust and metabolically versatile microbial biocatalysts. We tackled this challenge by means of systems metabolic engineering and validated Escherichia coli W as a promising cell factory for the production of the key building block chemical 2-ketoisovalerate (2-KIV) using whey as carbon source, a widely available and low-cost agro-industrial waste. First, we assessed the growth performance of Escherichia coli W on mono and disaccharides and demonstrated that using whey as carbon source enhances it significantly. Second, we searched the available literature and used metabolic modeling approaches to scrutinize the metabolic space of E. coli and explore its potential for overproduction of 2-KIV identifying as basic strategies the block of pyruvate depletion and the modulation of NAD/NADP ratio. We then used our model predictions to construct a suitable microbial chassis capable of overproducing 2-KIV with minimal genetic perturbations, i.e., deleting the pyruvate dehydrogenase and malate dehydrogenase. Finally, we used modular cloning to construct a synthetic 2-KIV pathway that was not sensitive to negative feedback, which effectively resulted in a rerouting of pyruvate towards 2-KIV. The resulting strain shows titers of up to 3.22 ± 0.07 g/L of 2-KIV and 1.40 ± 0.04 g/L of L-valine in 24 h using whey in batch cultures. Additionally, we obtained yields of up to 0.81 g 2-KIV/g substrate. The optimal microbial chassis we present here has minimal genetic modifications and is free of nutritional autotrophies to deliver high 2-KIV production rates using whey as a non-conventional substrate.

Drying kinetics and sensory characteristics of dehydrated pumpkin seeds (Cucurbita moschata) obtained by refractance window drying.

The current importance of pumpkin (Cucurbita moschata) in national food security has progressively encouraged research on this fruit. This is how pumpkin seeds constitute a potential raw material to obtain dehydrated products for direct consumption. In this research, we compared the drying kinetics, effective diffusivity (D ef ) and sensory perception in a non-trained panel of dehydrated pumpkin seeds through refractance window drying (RW) and convective air drying (CA). RW drying was carried out in a laboratory-scale hydro-dryer and CA drying was carried out in a dryer with hot air circulation; both at 80 ± 2 °C. Sensory acceptability (appearance, aroma, taste and texture) was evaluated by an affective test on a hedonic scale from 1 to 5 with 60 panelists. The drying curves (MR vs t) were fitted to four kinetic models: Newton, Logarithmic, Page and Midilli et al. D ef was determined by the second Fick's Law solution. The best model for RW drying was logarithmic, and D ef was 6.60 × 10-10 m2/s (R2 = 0.9927); while for CA, it was Midilli et al., with the D ef found through this method being 9.60 × 10-10 m2/s (R2 = 0.9928). Dry seeds by RW obtained a general acceptance of 3.82, compared to 3.63 by CA. Results allow us to conclude that among the drying methods evaluated, there is not statistically significant differences, in terms of dehydration characteristics and sensory acceptability, constituting RW drying as an alternative method for obtaining dehydrate pumpkins seeds for direct consumption.

Evaluation of the environmental impact of dry chemical silage obtained from the viscera of red tilapia (Oreochromis spp.) using ecological footprint methodology.

Fish production worldwide has increased over the years due to increased populations and interest from consumers. This has led to an increase in the waste produced by this industry, with viscera being particularly notable as one of the main sources of negative environmental impact. This study will determine the environmental impact created when obtaining dry chemical silage from the viscera of red tilapia (Oreochromis spp.), using ecological footprint methodology as an indicator of sustainability. This process allows approximately 30% of CO2 emissions to be mitigated compared to those generated when fresh viscera are dumped into shallow landfills, while implementing actions that improve the process such as biogas production from waste and solar drying of the final product can mitigate approximately 86% of its environmental impact, when compared to the disposal of fresh viscera. It was concluded that the production of dry chemical silage using alternative drying energy is environmentally sustainable.

Electrically Switchable Nanolever Technology for the Screening of Metal-Chelating Peptides in Hydrolysates.

Metal-chelating peptides (MCP) are considered as indirect antioxidants due to their capacity to inhibit radical chain reaction and oxidation. Here, we propose a new proof of concept for the screening of MCPs present in protein hydrolysates for valorizing their antioxidant properties by using the emerging time-resolved molecular dynamics technology, switchSENSE. This method unveils possible interactions between MCPs and immobilized nickel ions using fluorescence and electro-switchable DNA chips. The switchSENSE method was first set up on synthetic peptides known for their metal-chelating properties. Then, it was applied to soy and tilapia viscera protein hydrolysates. Their Cu2+-chelation capacity was, in addition, determined by UV-visible spectrophotometry as a reference method. The switchSENSE method has displayed a high sensitivity to evidence the presence of MCPs in both hydrolysates. Hence, we demonstrate for the first time that this newly introduced technology is a convenient methodology to screen protein hydrolysates in order to determine the presence of MCPs before launching time-consuming separations.

Kinetic analysis and modeling of L-valine production in fermentation batch from E. coli using glucose, lactose and whey as carbon sources.

In this study the effect of the carbon source on L-valine production kinetics using genetically modified E. coli was researched. Glucose, lactose, Whey (W) and deproteinized whey (DW) were tested as carbon sources, keeping the carbon/nitrogen (C/N) ratio constant. Biomass generation and substrate consumption were modeled with Contois and Mass Conservation models, respectively, whereas Mass Conservation Balance and Luedeking-Piret models were used for product obtaining. Results showed that L-valine production is partially associated to growth, with values of 0.485 g L-valine/(g dry cell weight.h), and a product loss effect at a specific rate (ß) of 0.019 g L-valine/(g dry cell weight.h) with W. The yield of this product increased 36 % using W concerning glucose or lactose as carbon sources. On the other hand, Mass Balance and Luedeking-Piret models adjust properly to experimental data (R2 >0.90). In conclusion whey is a promising substrate for obtaining L-valine using genetically-modified E. coli.

Sorption isotherms and thermodynamic properties of the dry silage of red tilapia viscera (Oreochromis spp.) obtained in a direct solar dryer.

The sorption isotherms, thermodynamic properties and calculation for confirming the isokinetic theory of dry chemical silage of red tilapia viscera (Oreochromis spp.) obtained in a direct passive solar dryer were determined. Sorption isotherms were carried out at 15, 25, 35 and 45 °C using a static gravimetric method. The curves obtained were adjusted to eight equations. The isosteric heat of sorption (net and total) and the thermodynamic parameters were determined based on the Clausius-Clapeyron equation and the enthalpy-entropy compensation theory was applied to adsorption isotherms. The sorption isotherms obtained were of type III of Brunauer classification. The Peleg model best described the experimental data. In all cases, the isosteric heat decreased while the moisture content increased. The value of isokinetic temperature (TB) was found to be less than harmonic mean temperature (Thm), the sorption of water in dry chemical silage is therefore controlled by entropic mechanisms and proceeds spontaneously.

Optimization of enzymatic hydrolysis of red tilapia scales (Oreochromis sp.) to obtain bioactive peptides.

The objective of this study was to optimize the conditions of enzymatic hydrolysis (type of enzyme, pH, temperature (T), substrate (S) and enzyme concentration (E)) to increase content of soluble peptides (P), antioxidant activities and degree of hydrolysis DH (%), in hydrolysates. Also, the effect of scaling up from a 0.5 L to a 7.5 L reactor, was evaluated. Hydrolysis was carried out for 3 h in a 500 mL reactor, with Alcalase® 2.4 L and Flavourzyme® 500 L enzymes. A second experimental design was then developed with S and E as factors, where DH, P and antioxidant activity, were response variables. The Alcalase® 2.4 L was the most productive enzyme, with optimal S and E of 45 g/L and 4.4 g/L, respectively. Its hydrolysates showed antioxidant activities with IC50 of 0.76 g/L, 12 g/L and 8 g/L for ABTS, FRAP and ICA, respectively. The scale up didn't showed negative effect on the hydrolysis.

Bovine plasma hydrolysates' iron chelating capacity and its potentiating effect on ferritin synthesis in Caco-2 cells.

The low bioavailability of iron is one factor that contributes to its deficiency in the human diet. For this reason, it is necessary to find compounds that can form iron chelates so that these can be added to foods that contain iron to improve its bioavailability at the intracellular level. In this study, we assessed the relationship between bovine plasma hydrolysates' iron chelating ability and their degree of hydrolysis. The hydrolysate with the highest chelating capacity was fractionated and each fraction's chelating capacity was subsequently assessed. Each fraction's effect on ferritin synthesis in Caco-2 cells was also determined. The results showed that bovine plasma hydrolysates with a degree of hydrolysis of 19.1% have an iron chelating capacity of 38.5 ± 0.4% and increase the synthesis of ferritin in Caco-2 cells five-fold compared to the control. This may be due to the fact that these hydrolysates contain amino acids such as Leu, Lys, Glu, Ala, Asp, Val, Thr, Cys and Phe, which may be responsible for binding iron to the hydrolysate, increasing its solubility and the consequent uptake by Caco-2 cells.

Kinetic modeling of the alkaline deproteinization of Nile-tilapia skin for the production of collagen.

A new phenomenological model, based on a second order dissolution kinetics, was developed for the alkaline removal of non-collagenous protein (NCP) from the skin of Nile tilapia (SNT). This model allows estimating the liquid concentration of NCP in terms of temperature, skin size, NaOH concentration and time. This model was fitted with 135 experiments averaging a R2 of 0.99. The root-mean-square deviation and the mean-absolute-percentage error of the model were 0.0041 and 3.15%, respectively. The Arrhenius-activation energy was 15-122 kJ mol-1. Multi-objective optimization led to the highest NCP extraction (NCPE) of 24.3% and to the lowest loss of collagen (LC) of 1.3%, with R2 coefficients of 0.98 and 0.92, respectively. Ultimately, SNT deproteinized under optimal conditions was subjected to acid extraction and purification. FTIR and SEM analyses indicated that the product was a Type I collagen that could be used in the pharmaceutical industry.

Byproducts of aquaculture processes: development and prospective uses. Review / Subproductos de los procesos de acuicultura: desarrollo y usos prospectivos. Revisión

Background: Growing aquaculture production around the world generates an important environmental impact because of its waste volume, which reaches nearly 60%. These byproducts have important levels of protein and lipids that can be revaluated to obtain products that are of interest to the pharmaceutical and food industries such as bioactive peptides and functional properties. Recently, technologies have been applied to the isolation and purification of bioactive peptides according to their molecular weight, such as membrane separation techniques and chromatography. Currently, there are commercial products from fish protein hydrolysates that can be used in nutritional and pharmaceutical applications as a source of amino acids with different physiological functions. Objective: Give information on aquaculture byproducts, hydrolysis methods, methods of purification, bioactive peptides and functional properties and nutritional supplements. Methods: Science Direct, Springer Link, Wiley Online Library, and Scopus were reviewed using the keywords aquaculture products, protein hydrolysis, bioactive peptides, functional properties. For the selection of the articles, the year of publication, the language, the methodology used and the trajectory of the authors were taken into account. Conclusions: This review is a brief description of the use of aquaculture byproducts using different types of hydrolysis process and their multiple applications on several industries.

Antecedentes: El crecimiento de la producción acuícola en el mundo genera un importante impacto ambiental debido a su volumen de residuos, que alcanza casi el 60%. Estos subproductos tienen niveles importantes de proteínas y lípidos que pueden revaluarse para obtener productos que son de interés para las industrias farmacéutica y alimentaria, como péptidos bioactivos y propiedades funcionales. Recientemente, se han aplicado tecnologías para el aislamiento y la purificación de péptidos bioactivos de acuerdo con su peso molecular, así como técnicas de separación de membrana y cromatografía. Actualmente, hay productos comerciales de hidrolizados de proteína de pescado que pueden usarse en aplicaciones nutricionales y farmacéuticas como fuente de aminoácidos con diferentes funciones fisiológicas. Objetivo: Proporcionar información sobre subproductos de la acuicultura, métodos de hidrólisis, métodos de purificación, péptidos bioactivos, propiedades funcionales y suplementos nutricionales. Métodos: Se revisaron bases de datos como Science Direct, Springer Link, Wiley Online Library y Scopus usando palabras clave como productos de acuicultura, hidrólisis de proteínas, péptidos bioactivos, propiedades funcionales. Para la selección de los artículos se tuvo en cuenta el año de publicación, el idioma, la metodología empleada y la trayectoria de sus autores. Conclusiones: Esta revisión es una breve descripción del uso de subproductos acuícolas usando diferentes tipos de procesos de hidrólisis y sus múltiples aplicaciones en varias industrias.

Kinetic modeling of the enzymatic hydrolysis of proteins of visceras from red tilapia (Oreochromis sp): effect if substrate and enzyme concentration / Modelado de la cinética de la hidrolisis enzimática de proteínas de vísceras de tilapia roja (Oreochromis sp): efecto de la concentración de enzima y de sustrato

Background: the growth of world aquaculture has generated important environmental impacts as discard residues that are important sources of protein, which has been used to manufacture low-value products, such as animal food, fish flour and fertilizers. Objectives: to evaluate the effect of enzyme and substrate concentration on the degree of hydrolysis (DH) of proteins in the red tilapia (Oreochromis sp.) viscera (RTV). Methods: the commercial alcalase 2.4 L enzyme was used at different concentrations to hydrolyse the proteins in RTV at 53.5°C and a pH of 9.5 in a 1 L magnetically stirred, jacketed, glass batch reactor connected to an automatic titrator. Each experiment was conducted over 6 h in which every consumed volume of base was recorded every 5 min to determine the corresponding DH at each point. Results: the results indicated that increasing the enzyme concentration produced an increase in the DH and in the reaction rate, while increasing the substrate concentration produced a decrease in both parameters. For this reason, a mathematical model was adjusted for the inhibition of substrate from the exponential kinetic equation d(DH)/dt = a* EXP[-b* (DH)] to explain the behavior of the DH as a function of substrate concentration in this hydrolytic process. The parameters a and b were estimated from a nonlinear regression. Based on these results, the reaction constants were determined as Ks = 456.75 g L-1, K2 = 1.2191 min-1, Kd = 0.2224 min-1, KM = 1.8963 and K3 = 0.1173 L g-1 min-1, which allowed the generation of a good correlation between the predicted and experimental values at the different evaluated operating conditions. This correlation was supported by a low average relative error (ARE) of 3.26%. Conclusion: under evaluated experimental conditions, the kinetics of the hydrolysis reaction followed a substrate inhibition mechanism without product inhibition, which was adjusted through a typical exponential Equation that involves two parameters (a and b) associated with the kinetic constants (Ks, K2, and Kd).

Antecedentes: el crecimiento de la acuicultura en el mundo ha provocado importantes impactos ambientales como el descarte de residuos que son importantes fuentes de proteína, los cuales han sido usados para manufacturar productos de bajo valor tales como: alimento para animales, harina de pescado y fertilizantes. Objetivo: evaluar el efecto de la concentración de enzima y de sustrato sobre el grado de hidrolisis (GH) de las proteínas presentes en las vísceras de tilapia roja (Oreochromis sp.) (VTR). Métodos: se empleó la enzima commercial alcalasa 2.4 L a diferentes concentraciones para hidrolizar las proteínas presentes en la VTR a 53°C y a un pH de 9.5 en un reactor de vidrio de 1 L con chaqueta, magnéticamente agitado y conectado a un titulador automático. Cada experimento se llevó cabo por 6 h registrando cada 5 min el volumen de base cosumido para determinar el grado de hidrolisis correspondiente a cada punto. Resultados: los resultados indicaron que un incremento en la concentración de enzima producía un incremento en el GH y en la velocidad de reacción, mientras que un aumento en la concentración de sustrato provocaba una disminución en ambos parámetros. Por esta razón, se ajustó un modelo matemático para la inhibición de sustrato a partir de la ecuación de cinética exponencial d(GH)/dt = a*EXP[-b*(GH)] para explicar el comportamiento del GH como una función de la concentración de sustrato en este proceso hidrolítico. Los parámetros a y b fueron evaluados mediante una regresión no lineal. Con base en estos resultados, las constantes de reacción fueron determinadas como Ks = 456.75 g L-1, K2 = 1.2191 min-1, Kd = 0.2224 min-1, KM = 1.8963 and K3 = 0.1173 L g-1 min-1, los cuales permitieron obtener una buena correlación entre los valores experimentales y los predichos a las diferentes condiciones de operación. Esta correlación fue soportada por un bajo error medio relativo del 3.26%. Conclusión: bajo las condiciones experimentales evaluadas, la cinética de la reacción de hidrólisis siguió un mecanismo de inhibición por sustrato sin inhibición por producto, el cual fue ajustado mediante una ecuación típica exponencial que involucra dos parámetros (a and b) asociados a las constantes cinéticas Ks, K2, and Kd.

Extracción de compuestos fenólicos y actividad antioxidante de hojas de Bixa orellana L. (achiote) / Extraction of phenolic compounds and antioxidant activity from leaves of Bixa orellana L. (achiote)

Introducción: Bixa orellana L. también conocida como achiote, es una planta con un rico depósito de compuestos bioactivos, tales como, saponinas, alcaloides y flavonoides, a los cuales se les atribuyen propiedades fisiológicas entre las que se encuentran: actividad antimicrobiana, antiinflamatoria, antialérgica, antiviral, anticancerígena, antioxidante, entre otras. Objetivos: evaluar el efecto del tiempo de extracción y la relación solvente/ sobre el contenido de fenoles totales, así como el efecto del contenido de sólidos y el pH de la solución, sobre la actividad antioxidante del extracto de hojas de B. orellana. Métodos: el contenido total de fenoles fue evaluado por el método de Folin-Ciocalteu. La actividad antioxidante se determinó por los métodos espectrofotométricos de reacción con el radical 2,2´-azino-bis (3-etilbenzotiazolin-6- ácido sulfónico) y la medida de la capacidad reductora sobre el Fe+3, los resultados se expresaron como micromoles de equivalentes Trolox por gramo de extracto (µmol ET.g-1). Resultados: las condiciones del proceso que más favorecen la extracción de compuestos fenólicos desde las hojas de Bixa orellana L. son: tiempo de extracción de 60 h y relación solvente/ hojas (v/p) de 4/1. El contenido máximo de fenoles totales fue de 144,77 ± 9,66 mgAT.g-1, que al someterlo a una solución de pH de 8 y 11,7 °Brix, presenta una actividad antioxidante de 4406,83 ± 43,30 µmol ET.g-1 por el método de reacción con el radical 2,2´-azino-bis (3-etilbenzotiazolin-6- ácido sulfónico) y 4547,22 ± 53,19 µmolET.g-1 por el método de medida de la capacidad reductora sobre el Fe+3. Conclusiones: se demostró que la cantidad de fenoles totales extraídos de hojas de B. orellana dependen de la relación solvente/material vegetal y del tiempo de extracción; asimismo, se encontró que el pH tiene efecto sobre la actividad antioxidante determinada por la reacción con el radical 2,2´-azino-bis (3-etilbenzotiazolin-6- ácido sulfónico) y la medida de la capacidad reductora sobre el Fe+3(AU)

Introduction: Bixa orellana L. also known as annatto, is a plant with a high content of bioactive compounds, such as saponins, alkaloids and flavonoids that have physiological properties as antimicrobial, anti-inflammatory, anti-allergenic, antiviral, anticarcinogenic and antioxidant properties, among others. Objectives: To evaluate the effect of extraction time and the solvent/ leaf ratio over the total phenolic content and the effect of solids and pH of the solution on the antioxidant activity in extracts from Bixa orellana leaves. Methods : The ethanol extract of leaves of Bixa orellana was obtained by percolation and filtering. Total phenol content was evaluated by the Folin-Ciocalteu. The antioxidant activity was determined by spectrophotometric methods as reaction with 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) and ferric reducing antioxidant power, the results were expressed as micromoles of Trolox equivalents per gram of extract (µmolTE.g -1). Results: Process conditions that improve the extraction of phenolic compounds from Bixa. orellana extract are: extraction time of 60 h and solvent/ leaves ratio (v/w) of 4/1. The maximum total phenol content was 144.77 ± 9.66mgAT.g-1, which when subject to a solution of pH 8 and 11.7 °Brix, has an antioxidant activity of 4406.83 ± 43.30 µmolTE.g-1 by the 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) reaction and 4547.22 ± 53.19 µmolET.g-1 by ferric reducing antioxidant power. Conclusion: It showed that the amount of TF extracted from leaves of Bixa orellana depend on the solvent/ leaves ratio and the extraction time. In addition, it found that the pH has an effect on the antioxidant activity determined by the methods 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) reaction and ferric reducing antioxidant power(AU)

Effects of hydrolysis and digestion in vitro on the activity of bovine plasma hydrolysates as inhibitors of the angiotensin I converting enzyme

The angiotensin I-converting enzyme (ACE) inhibiting activity of bovine plasma hydrolyzates obtained by Alcalase 2.4 L at different degrees of hydrolysis (DH) was evaluated. For the evaluation of ACE inhibition (ACEI), Hippuryl-His-Leu was used as substrate and the amount of hippuric acid liberated by non-inhibiting ACE was determined by spectrophotometry at 228 nm. The results showed that the enzymatic hydrolysis increased the ACEI activity as compared with the un-hydrolyzed plasma. The highest activity was onbtained with a DH of 6.7%. The peptide fractions with the maximum activity were isolated using ultrafiltration membranes, ion exchange chromatography and high performance liquid chromatography on reverse phase (RP-HPLC). The fraction with highest ACEI activity, showed an IC50 of 0.18 mg/mL and contained peptides with sequences AGATGVTISGAG, YSRRHPEYAVS, Q(K)AW and L(l)I(I)VR, which were determined by MALDI-TOF-TOF. It was also found that after submitting such fraction to digestive conditions in vitro, the ACEI activity remained constant.

Acción de un campo magnético sobre un cultivo aireado de Saccharomyces cerevisiae / Efect of magnetic field on an aereated saccharomyces cerevisiae culture

El crecimiento de la levadura Saccharomyces cerevisiae en melaza (miel virgen de caña) fue evaluado en presencia de un campo magnético (CM) variable de alta frecuencia y extremadamente baja intensidad. Se compararon los resultados obtenidos en cultivos creciendo bajo la acción del CM y en condiciones ambientales normales (controles). Se hicieron ensayos en fermentadores de 400ml, a 25°C. El flujo de aire utilizado en cada fermentador fue de aproximadamente 1vvm. El CM, con frecuencia de 100kHz y densidad de campo de 250mG fue aplicado por 200s. Los resultados mostraron que el CM puede estimular el crecimiento del cultivo bajo condiciones de aireación y sin ellas, mostrando un límite para el efecto de estimulación, por encima del cual se puede presentar un efecto inhibitorio sobre el crecimiento del cultivo. Bajo ciertas condiciones, el cultivo presenta una especie de adaptación al efecto del CM y la levadura puede superar la inhibición provocada por éste. Se observó que los CM afectan el consumo de sustrato por parte del cultivo, mostrando que bajo ciertas condiciones los microorganismos tratados pueden tener mejor aprovechamiento del sustrato. La aireación del cultivo puede interactuar con el efecto de los CM sobre su crecimiento y consumo de sustrato. Al aplicar una dosis de tratamiento magnético al cultivo de levadura, se encontró que a las 25h el cultivo con tratamiento presentaba un crecimiento 14,4 por ciento mayor que el cultivo control. Al mismo tiempo el consumo de sustrato por parte del cultivo tratado era menor que el del control

Efectos de la concentración de solutos y la relación jarabe/fruta sobre la cinética de deshidratación osmótica de papaya en láminas / Effects of solute concentration and syrup/frut relation of the kinetics of osmotic dehydration of papaya slices

El objetivo del trabajo fue optimizar la relación jarabe/fruta y la concentración de una mezcla de sacarosa y cloruro de calcio (CaCl2) para la deshidratación osmótica de láminas de papaya hawaiana (Carica papaya), tratanto de maximizar la perdida de peso (por ciento PP), la pérdida de humedad (por ciento PH) y la disminución en la actividad acuosa (por ciento PAw). Se utilizó un diseño estadístico de superficies de respuesta para determinar los niveles óptimos de sacarosa, CaCl2 y relación fruta/jarabe. Los resultados mostraron que se puede maximizar los tres parámetros si se utiliza un jarabe con una concentración de sacarosa de 57 por ciento, CaCl2 de 0,55g/100ml y una relación jarabe/fruta de 5. Los valores máximos obtenidos fueron PP de 48,29 por ciento; PH de 48,2 por ciento y PAw de 6,6 por ciento