Now showing 1 - 8 of 8
  • Publication
    Development of a bivariate mathematical model to characterize simultaneously the dose-time-responses of pro-oxidant agents
    (American Society of Agricultural and Biological Engineers (ASABE), 2013-07) ; ; ;
    The available data about the interference of oxidation compounds in the oxidation kinetics of process such as lipid oxidation chain reactions, the resistance of pharmaceutical drugs, the effects of free radical agents in cell tissue, the damage caused in DNA, etc, are examples of the many applications for in vivo and in vitro assays. However, often in these bio-assays, only semi-quantitative conclusions can be obtained, due to the use of quantification procedures disregarding kinetic considerations. A pseudo-mechanistic model is proposed which is based on the accumulative Weibull's function, and represents a formal transfer from the field of the dose-response relationships. It allows researchers to obtain the simultaneous solution of a series of oxidation activities as a function of concentration and time. It describes satisfactorily simulations in which reaction compounds interact through a second order kinetic scheme. Its application is simple: it provides parametric estimates, which characterize the oxidative process; facilitates rigorous comparisons between the effects of distinct compounds in different systems; reduces the sensitivity to the experimental error; and its mathematical form constitutes a useful orientation to prepare more economic and efficient trial designs. The model was assayed, firstly, using the kinetic simulation of the oxidative process, and finally, it was applied to a variety of experimental data from other authors in different systems and conditions, obtaining highly satisfactory results in all cases. In all experimental data tested, the calculated parameters were always statistically significant (Student’s t-test, α = 0.05), the equations were consistent (Fisher’s F-test) and the goodness of fit (adj R2, adjusted coefficient of multiple determination) were up to 0.98.
  • Publication
    Mathematical modelling of domestic water flow
    A model was developed to simulate water flow with reliable parameters allowing the analysis of water consumption in selected areas. The model was applied to investigate the daily water consumption by domestic users in County Sligo, Ireland. The water flow data was obtained in 15 minute intervals from bulk meters in selected areas. The water consumption data was averaged in different time interval formats and fitted to the model. In all cases, the parameters were consistent (α=0.05) and the correlation coefficients (r2) were high, thus demonstrating the reliability of this approach.
  • Publication
    Valorisation of tomato wastes for development of nutrient-rich antioxidant ingredients: A sustainable approach towards the needs of the today's society
    Nutrient-rich antioxidant ingredients were produced from tomato fruit wastes using a microwave-assisted extraction (MAE) process. Different conditions of extraction time (t), temperature (T), ethanol concentration (Et) and solid/liquid ratio (S/L) were combined in a circumscribed central composite design and optimized by response surface methodology. The model was statistically validated and used for prediction in the experimental range. Under the global optimal MAE conditions (t = 20 min, T = 180 °C, Et = 47.4% and S/L = 45 g/L), it was possible to obtain an extraction yield of 75.5% and ingredients with high levels of sugars, proteins, phenolics, and flavonoids, and interesting antioxidant properties measured via ABTS+ scavenging activity and oxidative haemolysis inhibition assay (OxHLIA). The antioxidant capacity of the extracts was lower compared to the one of commercial food additives. However, the sustainably developed ingredients may be used in the fortification and functionalisation of food, as well as for incorporation in feed products.Industrial relevanceThis study addresses current needs of the agri-food sector, namely the recycling of plant wastes and production of valuable extracts for the food/feed industry. A MAE process was developed and optimized to maximize the recovery of nutrients and antioxidants from tomato fruit wastes. The optimum processing conditions established in this study allowed a high extraction yield and reduced solvent consumption. MAE can be considered as a sustainable alternative to conventional extraction methods. These findings will contribute to promote a more sustainable bioeconomy in the agro-food sector.
      479Scopus© Citations 56
  • Publication
    A new microplate procedure for simultaneous assessment of lipophilic and hydrophilic antioxidants and pro-oxidants, using crocin and β-carotene bleaching methods in a single combined assay: Tea extracts as a case study
    β-Carotene and crocin bleaching reactions are the basis of two methods extensively used to quantify antioxidant and pro-oxidant activities. They are appropriate for lipophilic and hydrophilic matrices, respectively, and can provide useful complementary information in the study of complex natural extracts containing components with variable degrees of polarity. In this regard, a microplate procedure (Carotene Combined Bleaching) is proposed that enables the combination of both methods in a single, informative and less expensive method which is also faster to carry out. As an illustrative model, the method was applied to test a set of commercial lipophilic and hydrophilic antioxidants and some predictable pro-oxidant agents. Afterwards, as a food compound case study, the antioxidant activity of five types of tea extracts (Green, Blue, White, Black and Red) were characterized and their equivalent potential activity was calculated using commercial antioxidants on the basis of the new procedure developed in this research. The activity of the tea extracts decreased in the following order: (a) In a predominantly lipophilic environment: White > Black > Red > Blue > Green tea extracts; and (b) In a predominantly hydrophilic environment: Green > Red > White > Black > Blue tea extracts
      806Scopus© Citations 25
  • Publication
    Catechin-based extract optimization obtained from Arbutus unedo L. fruits using maceration/microwave/ultrasound extraction techniques
    This study compares three extraction techniques (maceration, microwave and ultrasound) for catechin recovery from Arbutus unedo fruit extracts. To obtain the conditions that maximize catechin extraction yield, a response surface methodology was applied using a 3-level full factorial Box-Behnken design in which the processing time (t), temperature (T), ultrasonic power (W) and ethanol percentage (Et%) were the relevant independent variables with the response (catechin content, mg/g dw) measured by HPLC-PDA. A fixed solid/solvent ratio of 50 g/L was used in all techniques. Maceration and microwave extractions were found to be the most effective methods, capable of yielding 1.38 ± 0.1 and 1.70 ± 0.3 mg/g dw of catechin, respectively at the optimal extraction conditions. The optimal conditions for maceration were 93.2 ± 3.7 min, 79.6 ± 5.2 °C and 23.1 ± 3.7% of ethanol, while for the microwave extraction were 42.2 ± 4.1 min, 137.1 ± 8.1 °C and 12.1 ± 1.1% of ethanol. Comparatively with maceration, the microwave system was a faster solution, conducting to slightly higher catechin yields, but using higher temperatures to reach similar values. The ultrasound method was the least effective solution, yielding 0.71 ± 0.1 mg/g dw of catechin at 42.4 ± 3.6 min, 314.9 ± 21.2 W and 40.3 ± 3.8% ethanol. The results highlight the potential of using A. unedo fruits bio-residues as a productive source of catechin.
      590Scopus© Citations 81
  • Publication
    An efficient methodology for quantification of synergy and antagonism in single electron transfer antioxidant assays
    The development of new antioxidant compounds for incorporation in foods is a rapidly growing research area. The resulting interactions between complex antioxidant mixtures are a key issue; however, research in this area is still in its infancy. Experimental antioxidant models based on conventional dose¿responses, that can predict joint effects of chemical mixtures, are urgently needed. This paper illustrates a methodological procedure for single electron transfer (SET) antioxidant assays to determine the synergistic and antagonistic effects of combining binary mixtures of antioxidants. Despite the abundance of theories and procedures to describe the synergistic/antagonistic effects in SET assays, they appear to be inadequate. Some features hindering advances in this field include the lack of: (1) experimental design, as a result of the extended use of unambiguous and simplistic procedures to quantify the effects of joint responses, based on single-dose values; (2) detailed mathematical hypotheses to quantify dose¿response values, which in addition causes the associated difficulties for assessing the statistical consistence of the results; and (3) functional approaches that consider the possibility of interactive effects. This paper proposes solutions for each of these limitations. Established ideas from existing fields are used to replace the current simplistic procedures, in order to quantify the effects of joint responses. One of the common hypothesis (known as concentration addition) for describing the combined effects is established for SET assays. A dose dependent mathematical model representative of this hypothesis, based on probability functions with meaningful parameters, is applied. The interactive effects between antioxidants are introduced into the model with simple auxiliary functions that describe the variations induced by each antioxidant in the parameters that define the effects of the other. Finally, a comprehensive index to summarize the complex parametric responses in one single value is proposed. Although the approach was experimentally demonstrated just in two classical SET assays (DPPH and ABTS), the results could be directly expanded in future to other types of classical SET assays. The methodology proposed is more complex than some relatively common approaches; nevertheless we believe that it is free of the controversial aspects listed above. Statistically consistent responses of null, synergy and antagonism effects were found when characterizing the interactions between several pairs of individual and complex mixtures of chemical antioxidant agents.
      619Scopus© Citations 46
  • Publication
    Analytical criteria to quantify and compare the antioxidant and pro-oxidant capacity in competition assays: The bell protection function
    The development of a convenient mathematical application for testing the antioxidant and pro-oxidant potential of standard and novel therapeutic agents is essential for the research community and food industry in order to perform more precise evaluations of products and processes. In this work, a simple non-linear dose–time tool to test the effectiveness of compounds for competitive assays is presented. The model helps to describe accurately the antioxidant and pro-oxidant response as a function of time and dose by two criteria values and allows one to perform easily comparisons of both capacities from different compounds. The quantification procedure developed was applied to two well known in vitro competition assays, the β-carotene and crocin bleaching asymptotic reactions. The dose–time dependency of the response of commercial antioxidants and some expected pro-oxidant compounds was evaluated in this study and the results showed low experimental error. In addition, as an illustrative example of the capabilities of the criteria proposed, the quantification of the combined effect of an antioxidant and a pro-oxidant was analyzed. Afterwards, the model was verified for other relevant competitive methods, using available experimental data from the bibliography. Its application is simple, it provides parametric estimates which characterize the response, and it facilitates rigorous comparisons among the effects of different compounds and experimental approaches. In all experimental data tested, the calculated parameters were always statistically significant (Student's t-test, α = 0.05), the equations were consistent (Fisher's F-test) and the goodness of fit coefficient of determination was higher than 0.98.
      270Scopus© Citations 1
  • Publication
    Mathematical model as a standard procedure to analyze small and large water distribution networks
    Currently, more research to implement and monitor cleaner production practices for distribution and sustainable management of natural and alternative water sources to comply with the demands of the different users while preserving water levels are needed. In this paper, a periodic hourly-based model with meaningful parameters has been developed to analyze and forecast water demand as a function of time, thus enabling a better understanding of the consumption pattern and the condition of the pipe network. The model was tested by investigating the daily water consumption from selected categories of users which were isolated from different distribution networks in Sligo, Ireland. The flow data used was obtained in 15-min intervals and averaged in different time periods for analysis. In all cases, the model fittings obtained were highly consistent and all the parameters showed satisfactory confidence intervals (α = 0.05), thus demonstrating the reliability of this approach. The model provides a quick analysis revealing the regularities of water demand that could benefit water utility managers and researchers: to obtain optimal regulation and pumping schemes; for planning and design purposes; to control unexpected scenarios that can take place during the distribution of water; the performance of water distribution systems; and to locate possible network failures. In addition, the model parameters can be used as standard criteria for water utilities to compare precisely the water demand between different areas, identify complex trends and analyze the pipe network for managing, auditing and monitoring purposes.
      256Scopus© Citations 6