Parameters of quality in courgettes

The interest of the alimentary industry for satisfying the demands of the consumer to healthy products, healthy and with high nutritional content, gives place to a continuous development of cultivated able to adapt to the different environingingmental conditions. Such is the case of the courgette (Cucurbita pepo spp. pepo), characterised for showing a big variability morfotípica and high contents in antioxidant compounds, between which include the phenolic compounds. In the actuality, are diverse the technicians that can be employed to quantify the content in total phenolic compounds (CFT) in vegetables, such as the Liquid Chromatography of High Resolution (HPLC) and the Spectrophotometry UV-VIS. However, they are scarce the works in which it has studied the potential of fast technicians and no contaminantes like the spectroscopy by reflectance in the infrared near (NIRS) for the quantification of these compounds in vegetables. Said technician characterises for being clean, not using reagents and save time of analysis. By these reasons, his application in the alimentary industry has increased in the last years.

The aim of this study is to determine the potential of the technology NIRS to predict the phenolic compounds totals of cultivated in courgette, as well as determine the mathematical treatments that better predictions realizar of these compounds. The study carried out on 65 samples of exocarpo, 120 samples of mesocarpo and 185 samples that formed the group of calibration of exocarpo + mesocarpo pertaining to 14 accessions and 17 commercial varieties of courgette, cultivated in the Centre Ifapa The Mojonera (Almería, Spain). The samples were frozen products and liofilizadas and later grinded. The spectrums Nirs were registered with a team NIRS (Foss NirSystems model 6500), in way of reflectance, registering the spectrums each 2 nm in the interval of 400-2.500 nm (visible and infrared region). The equations of calibration and the treatment quimiométrico of the data carried out by means of the employment of the application Winisi II (v. 1,50 Infrasoft International).

The coefficients of determination obtained in the validation (r²_cval) for the CFT were 0,75 (mesocarpo) and 0,66 (exocarpo+mesocarpo). These results put of self-evident that it is possible to use this analytical technician for the fast prediction of CFT in courgette in mesocarpo and mesocarpo+exocarpo with sufficient accuracy for purposes of screening, allowing of this form a reduction of the work of laboratory. However, it would be convenient to increase the population of samples so as to improve the rank of values of CFT in exocarpo, of this form would improve the low coefficient of determination of validation obtained for this fabric (0,14).

17 commercial varieties of courgette analysed during the study.

The nutritional characterisation of fruit and vegetables is an appearance of high importance so much in the alimentary industry as in programs of genetic improvement, where identify the existent variability is an aim prioritario. The courgette (Cucurbita pepo ssp. pepo) Is one of the main vegetables produced in Europe, especially in Almería, Spain, because of his healthy properties and organolépticas. The technicians carried out for the determination of total phenolic compounds (CFT) are technical analytical that require numerous stages during the extraction equipment equipment, which comport long. Incidentally, in the programs of genetic improvement of this vegetable does necessary the analysis of numerous fruit to characterise the profile of CFT existent. During decades, the spectroscopy in the infrared near (NIRS) has employed like fast technician and of low cost for the analysis of multiple components in organic matrices. However, they do not exist bibliographic references on this technician for the quantification of CFT in fruit of courgette, in spite of his importance in programs of genetic improvement and in the alimentary industry. In this work, studies the potential of this technician for the prediction of the CFT in fruit of courgette.

The fruit were cultivated under the usual practices of irrigation, control of plagues and illnesses.

A total of 185 samples of fruit of pertaining courgette to 14 accessions, and of 17 commercial varieties, were used in this study. These were cultivated during three consecutive campaigns (2009 to 2012).

Material vegetable

After being germinated, the plántulas of courgette were transplanted to sacks of perlita (Grodan BV, 6040KD Roermond, NL) situated in an invernadero (36º 46' N, 2º 48' Or). For the growth of these followed the local cultural practices referents to the irrigation, control of plagues and illnesses. Each variety was represented by at least 3 fruit. Roughly 100 g of sample of cool courgette was liofilizado (Telstar, Terrasa, Spain) until achieving constant weight. Finally, the samples were finamente grinded.

Analysis of the content in phenolic totals

Analysis Nirs

After the lyophilisation, the fruit of courgette were finamente grinded. The register of spectrums NIR carried out with a spectrophotometer NIR (NIRSystems model 6500, Foss NIR Systems, Inc, Silver Spring, MD, USES) in way of reflectance, realizar a scanning from the 400 to 2.500 nm (visible and infrared regions near), The values of absorbance (log 1/R, where R is the reflectance) were registered in intervals of 2 nm. The equations of calibration for the CFT, so much in leather as in pulp, as well as the treatment quimiométrico of the data carried out by means of the Global computer application v, 1,50 (Winisi II, Infrasoft International, LLC, Port Matilda, PA, USES). The equations of calibration obtained using the data of absorbance (log 1/R), or derived of second order of the data log 1/R, by means of different combinations referents to size of the segment of derivación and softened. Wavelengths from the 400 to 2.500 nm each 8 nm were employed for the development of the equations of calibration. It used the algorithm of partial square minima modified (MPLS) for correlacionar the spectral data with the information of CFT of the samples.

Roughly 100g of sample of cool courgette was liofilizado until achieving a constant weight.

The validation crossed was used to determine the optimum number of terms to use in the equation (Shenk and Westerhaus, 1991), and determine the error of the prediction (SECV) showed by the different equations developed.

The method of validation crossed was also employed to identify those samples 'outliers' by means of the chemical value (t) or spectral (H). The samples ‘t outliers' are samples that have a relation between his value of reference and the spectral value that differ of the value of other samples of the population (values of t > 2,5). A value identified like H outlier means that a sample is espectralmente different to the rest of the samples of the population.

The Table 1 sample the composition in CFT of the samples employed for the study. So much the average like the standard deviation (OF) for the CFT was similar in both fabrics. The rank in the content of CFT was similar in exocarpo and mesocarpo, showing values from 2,76 to 5,07 mg/g ps and of 1,72 to 4,37 mg/g ps, respectively.

Table 1: descriptive Statistics for the contended in phenolic compounds in the samples of courgette studied in this work mg/g ps.

These results were analogous to the obtained previously in pumpkin by other authors (Oloyede et al., 2012). However, different investigations have found values in CFT slightly greater in other pertaining fruit to the family Cucurbitaceae (Mongkolsilp et al., 2004).

To determine the predictive capacity of the equations considered that that possessed the greater coefficient of determination in the validation crossed (r²_cval) and the elder ratio between the one of and SECV, defined like RPD (Williams, 1987). The Table 2 sample the predictive capacity of the equations developed for CFT for exocarpo, mesocarpo and exocarpo+mesocarpo in fruit of courgette. Having in consideration these statisticians, the prediction of CFT was upper with the second spectral derivative (2,10,5,1), for the case of mesocarpo and, exocarpo + mesocarpo; whereas for the population of exocarpo was the first derivative (1,4,4,1) with which obtained better results. On the other hand, in the table 2 shows like the predictive capacity of the equation for the prediction of CFT in mesocarpo presented better results (r²_cval =0,75) that when calibrating the fabric formed by the exocarpo of the fruit (r²_cval =0,14), or when they considered simultaneously both populations in the calibration, exocarpo+mesocarpo (r²_cval =0,59).

According to the values of RPD obtained for the different fabrics of courgette in study, the equations obtained could be useful for purposes of sampling, following the recommendations proposed by Williams and Sobering (1996), that established different groups in function of the value of the ratio: values of RPD lower to 1,5 are considered as no useful, values comprised between 1,5-2,0 can be employed for approximate predictions, those between 2,0-2,5 allow to develop quantitative predictions, whereas greater values of 3,0 can be considered to do good and excellent predictive models. In base to these considerations, could affirm that the models based in the spectroscopy Vis/ Nirs obtained are valid to develop able quantitative equations to predict approximate values of CFT in mesocarpo (RPD = 1,82) and exocarpo+mesocarpo (RPD = 1,46). However, the best results for the case of exocarpo (RPD = 0,81) (whose population was composed by 65 samples) indicate that it would owe to increase the population of samples so as to enter variability in the CFT of this fabric.

The technology Nirs is a highly employed technician for the determination of parameters of quality in vegetal products. In this work has put of self-evident the potential of the technology Nirs for the fast prediction of the content in phenolic totals in fruit of courgette, as well as the determination of the mathematical models that better results offer in the calibration of these compounds. The equations obtained for the prediction of the CFT in the mesocarpo of the courgette showed a good precision. By this reason, the technology Nirs can be employed in programs of genetic improvement and in routine control of the alimentary industry with the purpose to reduce the work of laboratory for the quantification of CFT. Once they are selected the samples whose content in CFT find in the rank of interest, would proceed to analyse the same by means of the technicians of conventional laboratory.

Gratitudes

This work has been funded by the Project RTA2009-00036-00-00 (Inia) and Bottoms Feder. M.T. White-Díaz appreciates the financials by the Ministry of Economy and Competitiveness through the Program of Learning of Personal Researcher, Fpi-Inia.

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