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MENDELNET 2016 ANALYSIS OF RED CURRANT (RIBES RUBRUM) AND RED GOOSEBERRY (RIBES UVA-CRISPA) VARIETIES BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROSCOPY VACLAV STURSA1, PAVEL DIVIS1,2, ZUZANA JURECKOVA1, ALES MATEJICEK3 1Department of Food Chemistry and Biotechnology 2Materials Research Centre Brno University of Technology Purkynova 118, 612 00 Brno CZECH REPUBLIC 3Research and Breeding Institute of Pomology Holovousy Ltd. Holovousy 129, 508 01 Horice CZECH REPUBLIC [email protected] Abstract: Berries are highly valued fruits containing many organic compounds with significant health benefits. This work is focused on determination of elemental composition of different red currant and gooseberry varieties, which is less known. An acid digestion method was used to decompose fruit samples and a method for determination of 9 nutritionaly important elements by inductively coupled plasma optical emission spectrometry was optimized. From the analysed varieties ´Jesan´ and ´Rubigo´red currants and ´Hinnonmaki Rot´ and ´Krasnoslawjanskij´red gooseberries were evaluated as the best for the use in food industry in terms of elemental composition. Key Words: currant, gooseberry, fruit, elemental composition INTRODUCTION Currants and gooseberries are known in Europe since the 14th century. They were consumed either fresh or as juices and jams, or as a fermented fruit beverages. Currant is a small shrub belonging to the family of Grossulariaceae, of the genus Ribes. The currant bush grows up to a height of 1–1.5 meters. Its leaves are yellowish-green in color and are arranged spirally on the stems in bunches of five. During each season, the shrub bears pendulous chain of small berries. The fruit has size of about 1 cm in diameter with a glossy skin and a persistent calyx at the apex, and containing 3–10 tiny seeds. Depending on the berries colour, red, white and black currants varieties can be distinguished (Strik 2003, Djordjevic et al. 2014). Gooseberries are deciduous shrubs, fast growing under optimum conditions to 1 m tall and 1.5 m wide. The leaves are alternate, single, deeply lobed, and glossy dark green. The fruit borne singly or in pairs at the axils, is a berry with many minute seeds at the center. A gooseberry may be green, white, yellow, or shades of red from pink to purple to almost black. Fruits of the European gooseberry may be very large but usually they are up to 3 cm long, less in width (Strik 2003). Growing of currants and gooseberries has been recently extensively on the decline mainly due to a massive expansion of Podosphaera mors-uvae fungus, the most important disease in gooseberry and currant. Within the modern trend of consuming foods with a high content of biologically active substances the cultivation of new varieties of currants and gooseberries resistant to pests and diseases becomes again very significant. In 2005 there were nearly 40 000 hectares of orchards growing gooseberry and 163 000 hectares growing currants worldwide. Berries are good source of many nutritionally significant compounds. Whereas the organic composition of the currant and gooseberry is subject of numerous publications (Benvenuti et al. 2004, Pantelidis et al. 2007, Da Silva Pinto et al. 2010, Vagiri et al. 2013) elemental composition of different currant and gooseberry varieties is less known. Elemental analysis of food matrices can be performed 669 | Page MENDELNET 2016 by various spectroscopic techniques. One of the often used techniques is atomic emission spectroscopy, mainly with inductively coupled plasma. The main analytical advantages of the ICP–OES over other spectroscopic techniques are the capability for efficient and reproducible vaporization, atomization and excitation of wide range of elements in various sample matrices, minimum spectral interferences and simultaneous determination of all metallic elements and some metalloids and non-metals (Ebdon et al. 1998). This work is focused on the elemental analysis of six different varieties of red currant and gooseberries. These varieties were grown at Research and Breeding Institute of Pomology Holovousy and they are resistant for most diseases typical for currants and gooseberries. As the elemental composition of fruit is one of the important nutrition parameter used in food industry, the results of this study may help to choose the best fruit cultivar in restored breeding programme of currant and gooseberry in the Czech Republic or in other countries. MATERIAL AND METHODS The ICP–OES instrument was calibrated by certified solutions of metals of interest (1 g/l, Astasol, Analytika, Czech Republic). For the decomposition of fruit samples nitric acid (Analpure, Analytika) was used. In all analyses only ultrapure water prepared by ELGA station (Veolia Watter systems Ltd., UK) was used. To verify the proper function of ICP–OES instrument the quality control material METRANAL no.3 containing different metals in strawberry leaves matrix (Analytika) was used. All of the analyses were performed on an ICP–OES (Ultima 2, Horiba Jobin Yvon, France) equipped with Mainhard type nebuliser and cyclonic spray chamber. An analytical balance AND HA-202M (A&D Company, Japan) was used to weight samples. Samples were shaken on GFL 3006 shaker (Gesselschaft für Laboratortechnik GmbH, Germany) and heated on Gerhardt heating plate (Gerhardt Bonn, Germany). All of the currant and gooseberry varieties were grown in the Czech Republic at the Research and Breeding Institute of Pomology Holovousy Ltd. (50 22'29'' N, 15 34'38'' E, 321m alt.) in the experimental orchard. The soil type in the experimental orchard is heavy loamy clay soil with a minimum thickness of 60–80 cm. The bedrock consists of clay stone. Average annual temperature of the locality is 8.14 °C. Average annual rainfall is 655 mm and average rainfall during vegetation period is 379 mm. All plants were 3 years old and no pesticides were used during the cultivation. The samples came from the harvests in 2013 and 2014. All fruits were harvested at full maturity, stored under -18 °C prior analysis and analyzed as soon as possible. Analyzed red currant varieties were: ´Detvan´, ´Jesan´, Junnifer´, ´Losan´, ´Rovada´, ´Rubigo´ and analyzed gooseberry varieties were: ´Alan´, ´Hinnonmaki Rot´, ´Karát´, ´Karmen´, ´Krasnoslawjanskij´,´Remarka´. Approximately 10 grams of fruit was decomposed by 20 ml of concentrated nitric acid. After 24 h of nitric acid addition and continuous sample shaking the sample was heated for 60 min until the complete decomposition. After cooling down, the samples were transferred into the 100 ml volumetric flasks and filled up with water. Each of the fruit variety was decomposed and analysed three times. The quality control material samples were prepared by the same way as the fruit samples. All concentrations were expressed as the average. The standard deviation was less than 10 % for all analysed samples. The concentrations in mg/kg of fresh weight were calculated as cm = cs .V / m, where cm is the concentration of element of interest in mg/kg, cs is the concentration of element of the interest in the analysed solution (mg/l), V is the volume of analysed solution (l) and m is the weight of the sample used for the analysis (kg). Obtained data were further analyzed with the XLStat and Microsoft Excel software. Testing for significance of mean effects and interactions on all variables was calculated using ANOVA analysis of variance and Tukey´s test. Statistical significance was set at P = 0.05. RESULTS AND DISCUSSION Before the analysis ICP–OES operating conditions were optimized by analysis of a standard solution containing 10 mg/l of each element of the interest. The standard matrix was modified to be the same as in the analysed samples. The optimal wavelengths were chosen in order to achieve the sufficient sensitivity and the least interference and they are presented in Table 1. The optimal power to plasma was 1200 W and peristaltic pump rotation 20 rpm. The optimal nebuliser pressure was estimated by measuring the ratio of the intensities of the magnesium 280 and 285 nm spectral lines and by measuring 670 | Page MENDELNET 2016 the ratio of signal and background (SBR). The results are presented in Figure 1 and it can be seen that the optimal pressure was 0.29 MPa. The plasma gas flow was adjusted according to the manufacturer's recommendations to 13 l/min. The optimal flow of additional (auxiliary) gas was different for minor (0.2 l/min) and major elements (0.8 l/min) as it is illustrated in Figure 2. The alkali and alkaline-earth metals have low ionization energy and they emit radiation already in the initial radiation zone which is located under the edge of the ICP torch. Addition of auxiliary gas lifts the plasma above the injector tube and it allows better monitoring of the radiation emission. After the ICP–OES conditions have been optimized, the correct settings of the ICP–OES instrument were verified by analysis of quality control material. The recoveries ranged from 92 to 105% (Table 1) which is acceptable. Results from the elemental analysis of red currant cultivars are summarized in Table 2. Large differences were observed in metal contents in currant. While zinc, copper and manganese were present in quantities less than 1 mg/kg, sodium, iron and magnesium up to 50 mg/kg and calcium with phosphorous up to 700 mg/kg. All currants were an excellent source of potassium (up to 1800 mg/kg). The difference between mineral content of different currant varieties was statistically significant (p < 0.05) which can be related to different pomological characteristic of analysed cultivars. From the nutritional point of view the ´Jesan´ and ´Rubigo´ varieties were evaluated as the best as they contained significantly higher concentrations of all major elements. In an average it can be concluded that consumption of 100 g of red currants examinated in this study cover about 1–5% of the recommended dietary allowance of potassium, calcium, phosphorous, sodium, iron, manganese, magnesium, copper and zinc for woman and men (Driskell 2009).

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