Effect of enzymatic hydrolyzed protein from pig bones on some biological and functional properties.

Pig bone residue is considered a potential source of hydrolysates from its protein with added value uses in the food industry. This work deals with the enzyme hydrolysis of pig bone protein. The conditions for extracting the protein hydrolysate were optimized and the equation obtained allowed samples with different degrees of hydrolysis (DH) to be extracted to study how the biological properties of in-vitro hydrolized protein affected digestibility, determination of the inhibitory activity of the angiotensin-converting enzyme and the antioxidant activity and its functional properties. It was found that the emulsifying capacity and emulsion stability increased at intermediate DH values, after which these properties decreased with the increase in DH. The in-vitro digestibility and angiotensin-converting enzyme (ACE) of the hydrolysates are also clearly affected by the DH. The amino acid composition of the hydrolized protein is also determined.

Optimization of extraction and deamidation of edible protein from evening primrose (Oenothera biennis L.) oil processing by-products and its effect on structural and techno-functional properties.

The optimization of ultrasound-assisted alkaline extraction and enzymatic deamidation by protein-glutaminase (PG) on evening primrose seed cake (EPSC) protein and its effect on structure (amino acid composition, secondary structure and electrophoresis pattern) and techno-functional properties (water-holding and oil-binding capacities, solubility, emulsifying and foaming properties) of EPSC protein were evaluated. The optimum conditions of the both processes were measured using response surface methodology (RSM). The maximum yield (26.4%) and protein content (86.1%) were reached at the optimized extraction conditions. Optimal conditions of PG deamidation based on reaching a high degree of deamidation (DD) with a simultaneously low degree of hydrolysis (DH). Under these conditions, DD and DH were 39.40 and 2.11%, respectively. Ultrasound-assisted alkaline extraction and enzymatic deamidation by PG have great potential to produce edible EPSC protein with modified techno-functional characteristics that can be used for several aims in the food and pharmaceutical applications.

Polysaccharides from pineapple core as a canning by-product: Extraction optimization, chemical structure, antioxidant and functional properties.

Ultrasonic-assisted extraction (UAE) technique has been investigated to extract polysaccharides from pineapple core as a by-product using response surface methodology. A Box-Behnken design was employed to optimize the conditions for the maximum extraction yield of polysaccharides. The results demonstrated that the optimum extraction conditions were as follows: water/solid material ratio of 29.5 mL/g, extraction temperature of 66.3 °C and extraction time of 46.7 min. Under these conditions, the extraction yield of pineapple core polysaccharides (PCPs) was 16.7%. The structure of PCPs was analyzed by Fourier transform-infrared spectroscopy (FT-IR) analysis, X-ray diffractometry (XRD), SEM (scanning electron microscope) and gas chromatography-mass spectrometry (GC-MS). The results of thermogravimetric analysis indicated that the PCPs had a good thermal stability at temperatures below 250 °C. The extracted polysaccharides had a porous structure with rough surface. The extracted polysaccharides had strong scavenging activities on DPPH and hydroxyl radicals. Furthermore, they demonstrated interesting water-holding and fat-binding capacities (3.11 and 4.25 g/g, respectively). The results revealed that polysaccharides displayed good emulsifying and foaming properties. Overall, the findings suggest that PCPs are a promising source of antioxidants and may have potential applications in functional food industries.

Application of Ultrasound-Ultrafiltration-Assisted alkaline isoelectric precipitation (UUAAIP) technique for producing alfalfa protein isolate for human consumption: Optimization, comparison, physicochemical, and functional properties.

A new Ultrasound-Ultrafiltration-Assisted Alkaline Isoelectric Precipitation (UUAAIP) technique was employed for producing alfalfa protein isolate from alfalfa leaves. A five-factor-three-level Box-Behnken Design (BBD) was used to optimize the UUAAIP process for maximizing both extraction yield and protein content simultaneously. The optimum conditions were as follows: solvent/solid material ratio of 43.3 mL/g, pH of 10.1, extraction temperature of 42.5 °C, extraction time of 102 min, and flow rate of 9.7 L/h. Under these conditions, the maximum predicted extraction yield and protein content were 14.5 g/100 g and 91.1 g/100 g, respectively. UUAAIP technique improved the average molecular weight and color of the isolate. Moreover, it was efficient in removing the saponins and phenolic compounds as anti-nutritional factors compared to heat-coagulation extraction (HCE) and alkaline isoelectric precipitation extraction (AIPE). The protein isolate extracted by UUAAIP had greater solubility, water-holding and oil-binding capacities but lower emulsifying and foaming properties than those extracted by HCE and AIPE.

Optimisation and kinetic study of the ultrasonic-assisted extraction of total saponins from alfalfa (Medicago sativa) and its bioaccessibility using the response surface methodology.

The ultrasonic-assisted extraction of total saponins from alfalfa leaves was optimised by the simultaneous maximization of the yield and bioaccessibility as a factor with increasingly great relevance in the biological activity by Response Surface Methodology. The kinetics of total saponins and bioaccessibility were investigated for the optimum ultrasound-assisted method compared to conventional method by the pseudo-first order model. The optimum extraction conditions were of solvent/raw material ratio of 11.4 mL/g, extraction time of 2.84 h, extraction temperature of 76.8 °C, ultrasound power of 112.0 w and ethanol concentration of 78.2%. The yield of total saponins and bioaccessibility was 1.61 and 18.6%, respectively. The yield rate constant for the ultrasound extraction was almost two times more than that of the heat-reflux method. Ultrasonic-assisted extraction, comparing to conventional method, had greater efficiency for the extraction yield and bioaccessibility of total saponins.

Ascorbic acid degradation in aqueous solution during UV-Vis irradiation.

This work studied the effect of multi-wavelength UV processing on the ascorbic acid content of aqueous solutions, at different pH values (3, 4, and 5). The source of radiation was a mid-pressure mercury lamp (460 W), emitting between 250 and 740 nm. The samples were treated for 60 min, at 25 °C and 45 °C, with the lamp on and with the lamp off. A radiation balance was performed to estimate the total radiation power absorbed by the whole solution. Ascorbic acid content was reduced, either in irradiated or non-irradiated solutions, due to aerobic oxidation. But, in most cases, irradiation did not accelerate degradation. This can be explained by the fact that ascorbic acid barley absorbs ultraviolet in the interval of wavelengths emitted by the lamp (only 31% of the incident radiation P(0) could be absorbed by the solutions). Therefore, mid-pressure mercury lamps are helpful to avoid Vitamin C photo-degradation.

Optimisation of steam blanching on enzymatic activity, color and protein degradation of alfalfa (Medicago sativa) to improve some quality characteristics of its edible protein.

The use of alfalfa protein in human food is limited by its low quality. Response Surface Methodology was employed to optimise the combined effects of different steam blanching conditions on the enzymatic activity, browning and protein degrading which cause undesirable characteristics. The optimum conditions were: steaming time 4.36 min, particle size 23 mm, time from harvesting to steaming 2 h leading to a residual activity of polyphenol oxidase of 1.31% and a completely inactivation of peroxidase. The Browning Index value was 108.3 and the non-protein nitrogen 170.2 (g kg-1 TN). The browning and protein degradation rates of alfalfa treated under the optimum conditions were much lower than the control alfalfa after 60 days ensiling. This suggests that blanching of fresh whole alfalfa leaves under the optimum conditions was helpful for avoiding the appearance of the dark color and degradation of the extracted protein, improving its quality for human consumption.

Bleaching of sugar cane juice using a food-grade adsorber resin and explained by a kinetic model describing the variation in time of the content of adsorbate.

This work studies the adsorption of colored compounds in cane juice using a food-grade macroporous adsorber resin without functional groups. The adsorption equilibrium was studied through the adsorption isotherms at 30, 40, and 50 ℃. The absorbance at 420 nm was used to measure the concentration of colored compounds, which enables correlation of the residual concentration with the adsorbed concentration. Furthermore, the efficiency of the adsorption process was studied, from which it was observed that there was an improvement in efficiency with increasing resin content, while the increase in temperature was less important in the process. The kinetic study was performed using the Ibarz model and intraparticle diffusion model, which correctly account for the kinetics of the adsorption process. The adsorption kinetic constant was always greater than the desorption kinetic constant, indicating that the adsorption step predominates over the desorption step.

Kinetic and thermodynamic study of the photochemical degradation of patulin.

In a previous work, the UV photodegradation of patulin was concluded to follow a first-order kinetic and to be faster at acidic pH. In this case, the UV photodegradation of aqueous patulin solutions was studied at acidic pH values (3-6) similar to the values of apple juices where patulin has been found, obtaining that the first-order kinetic constant increased when the acidity of the reaction media was also increased (pH decreased). From the parameters obtained by fitting the experimental data to both the Arrhenius and Van't Hoff equations, the existence of kinetic and thermodynamic compensations was studied. Apparent kinetic and thermodynamic compensations were concluded, the isokinetic and isoequilibrium temperatures being -13.4 and -15.4°C, respectively. As the harmonic mean temperature was 34.3°C, applying the statistical criterion, it was concluded that both compensations were real, the reaction mechanism control changing from enthalpic for temperatures lower than the isokinetic-isoequilibrium temperatures (-13.4/-15.4°C) to entropic for higher temperatures. It could also be concluded that the reaction rate depends on the pH value for the acidic range studied.

Kinetic and thermodynamic compensation. A current and practical review for foods.

Kinetic and thermodynamic compensations have been reported in many chemical, physical, biological and food processes. Kinetic compensation can be found for any process and when it takes place, it gives information about the reaction mechanism and whether the reaction is controlled by enthalpy or entropy. It consists of the linear relationship between the logarithm of the frequency factor (lnk0) and the activation energy (Ea), both previously obtained from the Arrhenius equation for different values of an environmental variable (e.g. pH, concentration of any substance not involved in the process, pressure, water activity, etc.). A mathematical consequence of kinetic compensation is the isokinetic temperature, this being the temperature at which the kinetic constant should be the same regardless of the environmental variable. Thermodynamic compensation can be found for any process involving an equilibrium and consists of the linear relationship between the variation of enthalpy and entropy, both previously obtained from the Van't Hoff equation for different values of an environmental variable. A mathematical consequence of thermodynamic compensation is the isoequilibrium temperature, this being the temperature at which the equilibrium constant should be the same regardless of the environmental variable. According to the transition state theory, some kinetic constants can be related to the equilibrium constant of the initial equilibrium stage between the reagents and the transition state. For these cases, it can be concluded that both compensations are related mathematically and therefore not only does the existence of one kind of compensation imply the existence of the other, but the isokinetic and isoequilibrium temperatures should both be the same, or at least very close to each other. However, there is no reason that forces the linearities that cause either kind of compensation. So, some processes have shown these linear relationships while others have not. Moreover, some authors have reported that, due to the fact that the estimates of the parameters for the couples lnk0-Ea and ΔH≠-ΔS≠ being correlated with each other, there is a statistic compensation that consists of the propagation of experimental errors, and this effect has to be considered before concluding kinetic and/or thermodynamic compensations. This work reviews how to deal with kinetic and thermodynamic compensations physically, mathematically and statistically, prior to a second part that reviews the food processes for which one or both of these compensations have been studied.

Ascorbic acid stability in fruit juices during thermosonication.

Thermosonication is an emerging technology useful for inactivating microorganisms and enzymes in fruit juices. However, the effect of the ultrasound processing on the ascorbic acid content is not clear and the results reported in the literature are contradictory. In this work, the impact of sonication and thermosonication on the ascorbic acid content was first evaluated in model systems. Degassed model solutions at four different pH values (3-6) were processed with or without sonication for 60min at two different conditions of temperature (25 and 55°C). In all cases, the ascorbic acid was stable under the treatment. After that, two commercial deaerated fruit juices were processed with and without US at 55°C. The ascorbic acid was also retained in these juices after the ultrasound processing under the most severe conditions studied. In conclusion, previous degassing/deaerating of fruit juices is recommended to prevent ascorbic acid degradation when thermosonication is applied.

Mechanisms for improving mass transfer in food with ultrasound technology: Describing the phenomena in two model cases.

The aim of this work was to demonstrate how ultrasound mechanisms (direct and indirect effects) improve the mass transfer phenomena in food processing, and which part of the process they are more effective in. Two model cases were evaluated: the hydration of sorghum grain (with two water activities) and the influx of a pigment into melon cylinders. Different treatments enabled us to evaluate and discriminate both direct (inertial flow and "sponge effect") and indirect effects (micro channel formation), alternating pre-treatments and treatments using an ultrasonic bath (20 kHz of frequency and 28 W/L of volumetric power) and a traditional water-bath. It was demonstrated that both the effects of ultrasound technology are more effective in food with higher water activity, the micro channels only forming in moist food. Moreover, micro channel formation could also be observed using agar gel cylinders, verifying the random formation of these due to cavitation. The direct effects were shown to be important in mass transfer enhancement not only in moist food, but also in dry food, this being improved by the micro channels formed and the porosity of the food. In conclusion, the improvement in mass transfer due to direct and indirect effects was firstly discriminated and described. It was proven that both phenomena are important for mass transfer in moist foods, while only the direct effects are important for dry foods. Based on these results, better processing using ultrasound technology can be obtained.

Peroxidase (POD) and polyphenol oxidase (PPO) photo-inactivation in a coconut water model solution using ultraviolet (UV).

The interest in coconut water as a beverage is increasing due, not only to its sensory properties, but also to its nutritional characteristics. Even so, several challenges limit its processing, the inactivation of the polyphenol oxidase (PPO) and peroxidase (POD) enzymes being the most important. Although the inactivation of these enzymes has been extensively studied in coconut water, both by conventional and emerging technologies, the technologies evaluated so far are either not effective in the inactivation of these enzymes and/or result in undesirable changes. This work evaluated the photo-inactivation of POD and PPO in a coconut water model solution using ultraviolet radiation (UV). Both enzymes showed continuous inactivation behaviour in relation to the processing time, this being described by a two-portion inactivation kinetics. A possible mechanism for the observed photo-inactivation was proposed, involving steps of molecular unfolding and aggregation. The POD activity after 15min of processing was ~5% of its original value, and reduced to ~1% after 30min of UV processing. After 15min of processing, PPO activity was ~8% of its original value, falling to ~2% after 30min of UV processing. The results obtained highlight the potential use of the ultraviolet radiation to inactivate both enzymes in coconut water.

An autocatalytic kinetic model for describing microbial growth during fermentation.

The mathematical modelling of the behaviour of microbial growth is widely desired in order to control, predict and design food and bioproduct processing, stability and safety. This work develops and proposes a new semi-empirical mathematical model, based on an autocatalytic kinetic, to describe the microbial growth through its biomass concentration. The proposed model was successfully validated using 15 microbial growth patterns, covering the three most important types of microorganisms in food and biotechnological processing (bacteria, yeasts and moulds). Its main advantages and limitations are discussed, as well as the interpretation of its parameters. It is shown that the new model can be used to describe the behaviour of microbial growth.

Chemical guide parameters for Spanish lemon (Citrus limon (L.) Burm.) juices.

To contribute for setting reference guideline for commercial juice extracted from the Spanish lemon varieties, chemical composition of 92 direct and 92 reconstituted samples were investigated. In direct lemon juice, titratable acidity was 52.4 g/L, being the citric acid the main component. Glucose, fructose and sucrose concentrations were 7.9, 7.3 and 4.5 g/L, respectively. Predominant mineral was potassium (1264.2mg/L), followed by phosphorous (306 mg/L), calcium (112 mg/L) and magnesium (92.6 mg/L). Hesperidin ranged from 257 to 484.8 mg/L, while water soluble pectins varied between 164.8 and 550 mg/L. Similar values were obtained in reconstituted lemon juice. There are different parameters that did not reach or exceeded the limits proposed by the European Association of the Industry of Juices and Nectars. These levels should be taken into account to modify the present reference guideline and that Spanish lemon juices are not discarded for to have lower or bigger values.

Albedo hydrolysis modelling and digestion with reused effluents in the enzymatic peeling process of grapefruits.

BACKGROUND: Until now, the optimisation of enzymatic peeling of grapefruit in the reactor has been obtained as the result of the semi-qualitative effects of enzyme activity. This work is an attempt to obtain quantified data. The reuse of enzymes to reduce costs in this process is unprecedented in the literature and is the aim of the present work. RESULTS: The optimal conditions determined for the maximum albedo degradation were a temperature of 40.6 °C and a time of 13.1 min in an enzymatic concentration of 0.067 mL enzymatic preparation per gram of peel in each litre of citrate buffer solution. The decrease in relative enzymatic activities in reused effluents was determined, as was the increase in activity when the enzymes were purified. These increases were 15.5% for polygalacturonase and 15.4% for cellulase activity. CONCLUSION: Optimal temperature, time and the ratio between peel mass and the enzymatic preparation volume were the best conditions for obtaining good peeling efficiency. The effluents from the enzymatic peeling process of the grapefruit still contain appreciable enzymatic activity after the digestion process. Thus, reusing these effluents while maintaining peeling efficacy and a subsequent recovery of the active enzymes by ultra-filtration of the effluents is the way to improve the efficiency of the process.

Modelamiento de la cinética de reacciones del pardeamiento no enzimático y el comportamiento reológico, en el proceso térmico de jugos y pulpas de fruta / Modeling the kinetics nonenzymatic browning reactions and rheological behavior in the termal process of fruit juices and pulps

En la manufactura de jugos y pulpas de fruta, tiene singular importancia referirse al pardeamiento no enzimático y al comportamiento reológico. El pardeamiento no enzimático es un fenómeno de oscurecimiento de naturaleza exclusivamente química (Braverman, 1980), se caracteriza por la presencia de polímeros pardos llamadas melanoidinas, generadas por las reacciones de Maillard o condensación de la melanoidina, la caramelización y el deterioro del ácido ascórbico; mientras que el comportamiento reólogo es la definición de la proporción de deformación del material al ser expuestas a esfuerzos de corte (σ) ocasionados por un reómetro (Muller, 1978; Ibarz, 2005). Los estudios de modelamiento de la formación de color y la definición de comportamiento reológico, considerados en la presente revisión, orientan a la conclusión de la existencia de una cinética de cero y primer orden respectivamente, siendo los factores que más influyen sobre las reacciones principalmente de Maillard; temperatura, presencia de aminoácidos, la actividad de agua y el pH, mientras que el comportamiento reológico se ve afectado por la temperatura, concentración de sólidos y el tamaño de las partículas que conforman la suspensión en el caso específico de las pulpas.

In the manufacture of fruit juices and pulps, is of paramount importance to refer to non-enzymatic browning and rheological behavior. The non-enzymatic browning is a phenomenon of darkening of a purely chemical (Braverman, 1980), is characterized by the presence of brown polymers called melanoidins, generated by the Maillard reaction or condensation of melanoidins, the caramelization and degradation of acid ascorbic, while the rheological behavior is define as the proportion deformation of the material when exposed to shear stress (σ) caused by a rheometer (Muller, 1978; Ibarz, 2005). Modeling studies of colour formation and definition of rheological behavior, considered in this review, aimed at the conclusion of the existence of a zero kinetic and first order respectively, and the most influential factors with the reactions are mainly Maillard, temperature, amino acids presence, water activity and pH, while the rheological behavior is affected by temperature, solid concentration and particles size that make up the suspension in the specific case of the pulps.

Toxic effect of melanoidins from glucose-asparagine on trypsin activity.

In this work the effect of the presence of the melanoidins from glucose-asparagine on the enzymatic activity of trypsin is studied. It was observed that an excess of N alpha-benzoyl-L-arginine ethyl ester (BAEE) has an inhibiting effect on this enzyme activity. The maximum reaction rate was obtained for a 0.06 mN substrate concentration. It is also observed that the presence of melanoidin inhibits the enzymatic activity of trypsin. This inhibition can be described as a linear mixed type where the inhibition constant alpha K(i) of the substrate-inhibitor complex is higher than the inhibition constant K(i) of the complex enzyme-inhibitor with a alpha value of 1.88.

[Effect of high hydrostatic pressure on water imbibition, cooking times and microstructure of Phaseolus vulgaris]. / Efecto de la alta presión hidrostática (APH) en la imbibición de agua, tiempos de cocción y microestructura del Phaseolus vulgaris.

The effect of high hydrostatic pressure (HHP) on water imbibition, cooking times, and microstructure of cotyledons and seed coats of black beans was evaluated. High pressure treatments at 275, 410, 550 or 690 MPa and 25 degrees C for 5 min increased the rate of water imbibition of black beans. The saturation degree of HHP treated black beans was reached 50% faster than the saturation degree of untreated black beans. High hydrostatic pressure treatments reduced the cooking times (CT) of unsoaked black beans by 25% to 39%, similar to black beans soaked for 3 h. The microstructure of HHP treated beans exhibited protein aggregation in cell protoplasm and swelling of cell walls and starch granules. Seed coats of HHP treated black beans were less smooth than seed coats of untreated black beans. The swelling of palisade, hourglass, and parenchyma cells was also observed in HHP treated black beans such as soaked beans. High hydrostatic treatment is an alternative for reducing the preparation long times of Phaseolus vulgaris.

Efecto de la alta presión hidrostática (APH) en la imbibición de agua, tiempos de cocción y microestructura del Phaseolus vulgaris / Effect of high hydrostatic pressure on water imbibition, cooking times and microstructure of Phaseolus vulgaris

The effect of high hydrostatic pressure (HHP) on water imbibition, cooking times, and microstructure of cotyledons and seed coats of black beans was evaluated. High pressure treatments at 275, 410, 550 or 690 MPa and 25 degrees C for 5 min increased the rate of water imbibition of black beans. The saturation degree of HHP treated black beans was reached 50 faster than the saturation degree of untreated black beans. High hydrostatic pressure treatments reduced the cooking times (CT) of unsoaked black beans by 25 to 39, similar to black beans soaked for 3 h. The microstructure of HHP treated beans exhibited protein aggregation in cell protoplasm and swelling of cell walls and starch granules. Seed coats of HHP treated black beans were less smooth than seed coats of untreated black beans. The swelling of palisade, hourglass, and parenchyma cells was also observed in HHP treated black beans such as soaked beans. High hydrostatic treatment is an alternative for reducing the preparation long times of Phaseolus vulgaris.