Proficiency Testing and Determination of Standard Parameters in Wine

Transcription

1 2018, TextRoad Publication ISSN X Journal of Agriculture and Food Technology Proficiency Testing and Determination of Standard Parameters in Wine Švancarová Laštincová Jarmila *1, Pospíšilová Ľubica 2, Drápelová Ida 3 *1 Central Controlling and Testing Institute in Agriculture, Matuškova 21, Bratislava, Slovakia 2 Dept. of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of Agri Science, Mendel University in Brno, Zemědělská 1, Brno, Czech Republic 3 Dept. of Pedology and Geology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědělská 3, Brno, Czech Republic ABSTRACT Proficiency testing and quality of selected parameters were evaluated in wine samples reached by different analytical methods and laboratories. Uncertainty, experimental standard deviation and z-score were compared in wines from the protected designation of origin. For the wine analysis various techniques are usually applied, but results should be always reliable and accurate. Therefore one of the results is also the recommendation about accuracy and precision of selected analytical method. White wine as samples were used in this round in 2014 and 2015 measuring standard parameters in CCTIA laboratory and results compared are in very good agreement. KEYWORDS: proficiency testing; wine analysis, protected designation of origin INTRODUCTION Quality variety wines which are produced in specified regions of Slovakia are the closely watched category of wine in European Union. Therefore high quality control of certified wines with protected designation of origin (PDO) is needed. Determination of standard parameters in wines are recommended by the Organisation of Vine and Wine (OIV). International laboratory comparison of analytical results is very important to provide correct measurements in all accredited laboratories. For the quality control in wine sector in Slovakia it is inevitable, that a state institution has a management of quality control and all the measurements and chemical analysis are in accordance with the international standard ISO: 17025/2005. Central Controlling and Testing Institute in Agriculture (CCTIA) in Bratislava has an accredited laboratory for testing wine products before introducing them into the market. One of the evaluated criterion for the assessment of laboratory performance is the Proficiency Tests, which should be attend as frequently as it is possible. As quoted Knaggs (2011a, b) and Lippold (2014) the FAPAS tests or the LVU tests can give a good base to evaluate precision, accuracy and trueness of measurements in tested laboratories. All of these testing programs were launched after regulation for testing laboratories Proficiency Testing of laboratories From Codex Alimentarius and ISO were issued (De Biévre, 2005; Thompson, 2006; ILAC Guide G 13). Milde (2016), Laštincová et al. (2013) and Stullerová et al. (2012) confirmed that proficiency testing represent a useful tool for classification of efficiency and quality of measurements of any parameters in a wine or must. But there are also other requirements recommended by OIV such as validation, precision, accuracy, reliability and rapidity of determination, which are necessary for controlling of quality measurements. A buyer of wine product might require that the laboratory of a supplier provide evidence that its laboratory is tested by independent agency. If the laboratory gives evidence of producing accurate data analysis of materials it supplies, the buyer can minimize additional testing of goods. In conjunction with the standard deviation for proficiency z-score for each laboratory was calculated. Every selected parameter has been in wine successfully analysed only when the absolute value of this z-score was lower than 2. In the case when the absolute magnitude is between 2-3 so review of analytical method is needed. If the content is not in the area of limit or if quotient LabSt/ZielSt is smaller than 0.5 or over 2; the results requires the critical review. MATERIALS AND METHODS One of the key requirements in wine quality characterization is the determination of selected parameters given in Tab. 1. The test material for LVU Proficiency test Analytik von Wein 2014 was dispatched in May 2014 (Germany) and in June 2015 (United Kingdom). Every participant received a wine material to be analysed for standard parameters like actual and whole alcoholic strength, density, total acidity, volatile acids, fructose, glucose, dry extract, and CO 2 pressure. In the CCTIA laboratory standard analytical methods described in Compendium of International Methods of Wine and Must Analysis - OIV (2018) were used. Total and actual alcoholic strength was determined by volumetric method. Detailed description of measurement of the alcoholic strength of distillate with a pycnometer *Corresponding Author: Jarmila Švancarová Laštincová, Central Controlling and Testing Institute in Agriculture, Matuškova 21, Bratislava, Slovakia; jarmila.lastincova@uksup.sk 1

2 Laštincová et al., 2018 are given in OIV-MA-AS312-01A. CO 2 pressure was determined by the manometric method (OIV-MA-AS314-02). Determination of total acids was performed as follows: CO 2 was removed from the sample by vacuum and potentiometric titration was used in our laboratory (OIV-MA-AS ). The results for dry extract (= total dry matter) was done according to OIV-MA-AS2-03B. Glucose and fructose was analysed by enzymatic method according to OIV-MA-AS In 2014 the sample was a white semi-sparkling wine with added carbon dioxide and used wine was industrial product of grape variety Müller Thurgau from the specific growing area. It was therefore not adjusted analytical face points to certain target values, however in the preparation an addition of ascorbic acid was used. For this reason was in iodometric determination distillation with correction needed. Sample storage conditions: temperature 1 8 C, dark, storage 1day and time between opening bottle and analysis 1 day. The test material for the LGC Proficiency Test (UK) was dispatched in June D1-Italian white wine as sample was used in this round /14/ for measuring standard parameters. Testing of wine in CCTIA laboratory in Bratislava is performed by ISO/IEC: 17025:2005 and validated methods are used. This system is reliable and results are highly acceptable, precise and accurate and z-score lies not outside the range ± 2. RESULTS AND DISCUSSION Proficiency testing of sparkling wine was organized by LVU in 2014 and by LGC in As it is shown in Tab. 1 5 and Fig. 1 and 2 very good and comparable results were achieved. Comparison of results of CO2 pressure (Table 2. and Figure.1) between 26 laboratories gave a minimal difference values (measured 1.68 barr; maximum value was 2.9 barr; median was 2.57 barr). ZielSt. was 0.215; LabSt. was and quotient sl/sr was For actual and total alcoholic strength the results could be summarized as follows: for determination of whole alcohol content it was 33 laboratories chosen from 36 and average was determined 11.8 % vol. The maximum value was % vol.; minimum was % vol.; median was % vol.; deviation results between laboratories LabSt. was 0.139; experimental target standard deviation ZielSt. was For the actual alcohol 41 laboratories was taken and minimum was % vol.; LabSt. was 0.093; ZielSt. was and sh was 0.299; sl/sh was 0.31 and quotient sl/sr was In combination with the standard deviation for proficiency, z-score was calculated for each result of each parameter for our laboratory (BA-SLAV) and very good results were achieved (Tab. 1). Table 1: Average values of determined parameters and z-score comparison in semi-sparkling wine 2014 (where: BA-slav = laboratory of CCTIA Bratislava, SD = standard deviation, ZielSt. = experimental target standard deviation, Labst/Ziel = deviation results between laboratories) Parameter BA-slav Median SD ZielSt. z-score Labst/Ziel Total alc. (% vol.) Actual alc. (% vol.) Glu (g.l -1 ) Fru (g.l -1 ) Acidity (g.l -1 ) Extract (g.l -1 ) Volatile acids (g.l -1 ) Pressure CO2(barr) Figure 1. Comparison of CO 2 pressure determination between all laboratories in 2014 (where: green median from citation given by Lippold (2014) 2

3 Table 2: Average values of CO2 measurements, z-score and standard deviation (SD) between some laboratories in 2014 test Laboratory 1 2 CO2 /barr/ SD z-score Results of determination of total acids content from 39 laboratories showed very good results for 34 from them. Minimum value was 7.01 g.l-1; maximum value was 7.75 g.l-1; average was g.l-1; median was g.l- 1; deviation result between labs (sl) was 0.202; target standard deviation according to Horwitz (sh) was Experimental standard deviation (sr) was and quotient sl/sr was The results for total dry matter (OIV-MA-AS2-03B) were in good agreement for all 40 laboratories. Average was g. L-1 and our result was 41.2 g.l-1. Quotient sl/sr was Comparison between all laboratories and selected results of studied parameters are summarised in Table 3. Table 3: Different Methods used for determination of volatile acids in 2014 Methods Blanc Corrected Yield OIV modif. with SO2 corr. no numeration - OIV without SO2 corr. yes no - Gerhardt-etc yes no - OIV313-02m yes no 96 AVV without SO2 corr AVV with SO2 corr. yes enumeration 100 AVV without SO2 corr. no - 99 OIV without SO2 corr. no enumeration 98 Gerhardt-etc yes OIV modif., with SO2 corr. yes titrimetry 103 FTIR OIV with SO2 corr. yes enumeration 99.8 OIV with SO2 corr. no titrimetry - OIV without corr. yes no - OIV without corr. no - - OIV without corr. no no - OIV with SO2 corr. no titrimetry 98 OIV modif. with corr. yes titrimetry 91 Gerhardt-etc no titrimetry 99.5 IFU 5 yes titrimetry - 3

4 Laštincová et al., 2018 Figure 2. Comparison of volatile acids determination between all laboratories in 2014 (Where: green = median; blue = distil. with SO 2 corr.; red = distil without SO 2 corr.; from citation Lippold (2014) Table 4: Comparison of all measured parameters between all laboratories in 2014 Parameter No of lab Average [sl*] [sr*] [sh*] sl/sh* sl/sr* Actual alc.% Total alc.% Glu gl Fru gl Acidity gl Extract gl **Volatile acid corr Volatile acid g.l CO2 gl Pressure barr *deviation result between labs (sl); target standard deviation according to Horwitz (sh); Experimental standard deviation (sr); quotient sl/sr **measured with correction As it can be seen in Tab. 3 and Fig. 2 that results for volatile acids were different because of using different analytical methods and not using correction. Detailed explanation of analytical method usually applied for vine analysis is given in Lippold (2014). It is clear that chosen method (e.g. OIV method with sorbic acid correction; or with SO2 correction; or method without SO2 correction; FTIR spectroscopy and Gerhardt etc.) directly influence accuracy of determination. It should be also stressed that if no correction was added results don t fit well (Tab. 3). On the other hand the results of 18 laboratories with SO2 correction (OIV-MA-AS313-02) fit very well (Table 4). Results of the determination of fructose were very precise. There were only 2 laboratories outside the limit. Our value was 13.5g L-1 and median was 13.0 g.l-1. The quotient sl/sr was For glucose 37 labs were in good agreement. Median was 7.39 g.l-1 and quotient sl/sr was 1.16 (OIV-MA-AS311-02). In 2015 LGC (UK) organized testing of Italian white wine for many laboratories. The summary of all the results and the performance assessments for our laboratory is given in Tab. 5. Table 5: Results of CCTIA laboratory Bratislava, in white Italian wine 2015 Parameter BA-slav Median SD ZielSt. z- score Methods Volatile acid Total acidy (g.l -1 ) Actual alc. (% vol.) Distill. Glu (g.l -1 ) Enzym Fru (g.l -1 ) Total SO2 (mg/l) Enzym 4

5 Further details of LVU Test are in LVU, Herbolzheim or in LGC DAPS-Alcoholic drinks PT Scheme ( For measurements experimental target standard deviation Zielstandard (sr) was calculated, which is stricter than the value sh according to Horwitz, therefore in the future will be used more frequently. In normal circumstances, about 95% of z-score will lie in the range If z-score is 3 is expected as a rarity and very strongly indicated that a result is not fit and requires investigation. CONCLUSION It is obvious that the choice and performance of analytical methods used for wine quality characterization is crucial to reach precise, accurate and reliable results of analysis. Proficiency testing aims to provide an independent assessment of the competence of participating laboratories. Together with the use of validated methods, proficiency testing is an essential element of laboratory quality assurance. Acknowledgements The study was supported by the project Earth QK of the Ministry of Agriculture of the Czech Republic. REFERENCES INTERNATIONAL ORGANISATION OF VINE AND WINE, Compendium of International Methods of Wine and Must Analysis - OIV KNAGGS, M. 2011a. FAPAS Wine Report Proficiency Test Analysis of wine. Crown Copyright, England, pp KNAGGS, M. 2011b. Labor Vergleichs Untersuchung Analytik von Wein Standardparameter, Herbolzheim, Germany. LIPPOLD, Ute und Ralf Labor Vergleichs Untersuchung Analytik von Wein Standard parameter, Herbolzheim, Germany, 2014, page (www. LVUs.de). THOMPSON, M., ELLISON, S.L.R., WOOD, R The International Harmonised Protocol for the Proficiency Testing of Analytical Chemistry Laboratories. Pure Appl. Chem., 78 (1): ILAC-Guide G13:08/2007. Guidelines for the Requirements for the Competence of Providers of Proficiency Testing Schemes.- DE BIÈVRE, P., DYBKAER, R., FAJGELJ, A. AND HIBBERT, D Metrological traceability of measurement results in chemistry. Pure Appl. Chem., 83 (10): /on line 15 June 2011/ MILDE, D Kvalimetrie 21. In: Analytical standards and equipment. Referenční materiály a mezilab. porovnávaní zkoušek VI, Valtice, 2theta, Český Tešín. ISBN LAŠTINCOVÁ, J., POSPÍŠILOVÁ, Ľ. and BEINROHR, E Proficiency testing in analysis of wine products. Journal of Chemistry and Chem. Engineering, 7 (8): STULLEROVÁ, L., KOVÁROVÁ, O Skúšky spôsobilosti ako účinný nástroj zabezpečenia kvality výsledkov skúšok. Chem. Listy, vol. 106: THOMPSON, M Recent trends in the interlaboratory precision at ppb and sub ppb concentrations in relations to fitness for purpose criteria in proficiency testing. Analyst, vol. 125: DE BIÉVRE, P Traceability in chemical measurements. Eds. Prof. Dr. Günzler H., Springer Berlin Heidelberg New York. ISBN LGC DAPS-Alcoholic Drinks PT Scheme, DP0210-UKSUP individual Report, Issue No1, 05 June 2015, Lancashire, UK. 5