16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/12172 Authenticity tests of organic products (Golden Delicious and Elstar) applying sensory analysis Ploeger, Angelika11, Röger, Monika1 , Weibel, Franco2 Key words: sensory evaluation, quantitative descriptive analysis, apple quality Abstract In the governmental funded project BÖL-02OE170/F, apple samples from different farming systems (organic and conventional) were differentiated and classified by sensory evaluation. Samples from farm pairs derived from geographical neighbouring locations. Each farm pair consisted of one farm producing apples according to organic land use system and one producing conventionally. Factors of influence as growing conditions, climate, soil and harvest time were comparable within each pair. For sensory evaluation, a descriptive analysis panel was trained according ISOstandards of descriptive analysis. The quantitative descriptive analysis method (QDA) enables to show a complete product profile with all sensory characteristics of a product as well as their intensity. Over 2 crop periods (2004/2005), 18 apple samples (9 pairs) were evaluated by QDA method; 5 samples pairs of the variety “Golden Delicious” and 4 sample pairs of the variety “Elstar”, each with 3 replicates and 6 apples per replicate. In the first crop year, descriptive analysis was done to develop product profiles of all samples. Based on these data, a classification model was developed to classify sensory characteristics of organic vs. conventional apple cultivation. According to this model, from 9 defined trial sample pairs, 8 sample pairs could be classified according to the farming system in the second year. Introduction Beside safety, freshness, general health benefits as well as nutritional value, one reason for consumers demanding organic foods is a tastier product (Bourn, D., Prescott, J., 2002). The results of the questionnaire conducted by Casutt and Guggenbuehl (2006) show that apples are consumed regularly (48% eat more than four apples a week) because consumers like them as a snack between meals and because they are refreshing. A number of studies comparing organic and conventional food have included sensory tests indicating that organic and conventional fruits and vegetables differ on a variety of sensory characteristics, but the findings are inconsistent (Bourn, D., Prescott J., 2002 ; Roth et al, 2005, Homutova, I., Blazek, J., 2006, Theuer, R, 2006). This is due to different sensory methods applied. The quantitative descriptive analysis method (QDA) is one of the most sophisticated tools in sensory science and allows - in opposition to preference or acceptance tests objective descriptions of products in terms of the perceived sensory attributes. Depending on the specific technique used, the description shows a complete product profile with all sensory characteristics and their intensity in appearance, aroma, texture, mouthfeel and flavour attributes. Because without a classification model describing a quality profile with consistent product characteristics of organic versus 1 : University of Kassel, Dep. Organic Food Quality and Food Culture, Nordbahnhofstr. 1a, D37213 Witzenhausen, Germany 2 Forschungsinstitut für biologischen Landbau (FIBL), Ackerstrasse, CH-5070 Frick 16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/12172 conventional products, preference/ acceptability measures that reflect relative degrees of liking are difficult to interpret. Therefore the aim of the study is to develop a classification model for two different varieties of apples (Golden Delicious and Elstar) of different farming systems. The research project was funded by the German Government (Ministry of Food, Farming and Consumer protection BÖL-02OE170/F). Materials and Methods Under the guidance of a panel leader, a panel group (10 – 12 persons) develops a scorecard with a list of attributes fully describing the product and developing definition for each attribute. At the same time a ranking of attributes of the product (apples) is done. At least the panellists learn to practice scoring along the intensity scale (0 to 9 resp. weak to strong). The panellists were trained to be able to communicate precisely without subjective descriptions and to work consistent and reproducible (Stone, Sidel 1993). Sensory evaluation was carried out during two consecutive years (from harvest 2004 and 2005). Two varieties of apple samples were tested, 5 sample pairs of variety “Golden Delicious” from defined field trial (FIBL Switzerland, F. Weibel) and 4 sample pairs of the variety “Elstar” (neighbouring farms, FAL Trenthorst). Each sample pair consisted of one sample derived from an organic producing system (according to Council Regulation [EEC] No. 834/2007 of the European Union) and one from a conventional farm. Harvest and climatic conditions were comparable. Training and evaluation were carried out according QDA-standards of Stone & Sidel (Stone,Sidel 1993). The panellists were calibrated directly on the test samples. During data collection, panellists got at maximum of 6 product samples per session in a randomized design order (according to sensory evaluation software FIZZ, Biosystemes, France). The samples were served in booths, monadically (each panellists got the samples in different order). All data were quantified by ratings of perceived intensities, using an unstructured line scale with end-anchors and offset goal posts (e. g. from weak to strong). Experimental design was as follows: 1. Factorial: each level of a factor is matched with each level of others, 2. Replicated: samples were evaluated 3 times, 3. Repeated measures: each panellist tasted each sample. The experimental design yields a four-dimensional data matrix: panelist x attributes x samples x replicates. The data were analysed by “FIZZ” sensory software. Descriptive statistical measures were first calculated for all attributes using scores from panellists. Analysis of variance was performed on each attribute using a randomized block design for balanced data, with panellists as repeated measures. Where F-test indicated a significant difference between test treatments, differences was defined as P < 0,05. In addition, data of the quantitative descriptive analysis were also differentiated by classification and regression tree system (CART-system, Breimann et al 1984), which classified the sample pairs by statistic evaluation. This so called tree system shows the relationship between one or more variables of influence (x variables) on a dependent variable (response variable =Y).The result of this statistical procedure is visualized as a tree (leafs are separated variables, branches are steps of differentiation. This tree can be used as a decision tree to look for key attributes or key parameters influencing the product quality. 16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/12172 Results Results of the descriptive quantitative analysis show a complete product profile of the evaluated apples (see figure 1 as an example). For multivariate variance analysis, the unstructured line scale is transferred into scores from 0 (no perceived intensity) to 9 (highest perceived intensity). The intensities given are results of all panellists and repetitions. By evaluating differences in the characteristic intensities, for classification into organic vs conventional samples, analogue differences in characteristic intensities were defined. Due to the comparison of both crop years for the variety Golden Delicious (from field trials in Switzerland), results show analogue characteristics of sweet and sour flavour in tendency, in year 2004 for 3 out of 5 sample pairs, in 2005 for 4 out of 5 sample pairs the organic sample was more sweet, the conventional had a more sour flavour. In crop year 2005 the conventional samples had a significantly higher intensity in firmness and juiciness of the pulp, which is seen only in tendency in crop year 2004. Most important for classification was the apple skin, which showed significant more firmness and thickness at all 5 organic samples in year 2005 and of 4 out of 5 samples in year 2004 (for Golden Delicious). . skin colour (*) skin off-Flavour 9 pulp colour (*) skin bitter Aroma overall 8 skin firm (*) off-aroma skin off-Aroma Afterfeeling acerb 7 6 Aroma sweet Aroma fruity 5 Afterfeeling astringent Aftertaste sour 4 3 Aroma must Aroma pear 2 Aftertaste sweet 1 Aroma banana 0 off-Aftertaste Aroma green Aftertaste overall Mouthfeel acerb Mouthfeel tingly Mouthfeel astringent Texture mealy Texture chewable (*) Texture juicyfirm (*) Texture Flavour overall Flavour sweet Flavour sour (*) Flavour pear Flavour banana Flavour must Flavour citrus (*) off-flavour G1(organic) G2 (conv.) Figure 1: Product profile of one sample pair (coded as organic/conventional), variety “Golden Delicious” (as an example) Also for the variety “Elstar” significant differences were found in firmness and thickness of the apple skin, the skin of the organic samples were more firm and thick in comparison of the conventional ones. The skin of the organic samples was also more bitter in flavour. In other characteristics, no significant classification could be perceived, in tendency a higher intensity of firmness of the pulp in organic samples could be shown (see table 1). Results of classifying the sample pairs by CARTSystems confirm the differences of characteristics. Sample pairs could be separate clearly within the juice rate and firmness of apple skin. 16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 Archived at http://orgprints.org/12172 Tab. 1: Pulp and skin parameters of organic and conventional Elstar (2004, 2005) Year 2004 2005 Samples conv. organic F-value signif. conv. organic F-value sign. Pulp colour 6,81 5,03 57,35 <0,0001 5,19 5,69 3,68 0,3841 Skin firmness 2,19 5,17 160,65 <0,0001 3,57 4,95 28,57 0,0081 Skin thickness 2,71 4,53 59,3 <0,0001 3 4,03 15,79 0,0365 Skin bitter 3,65 4,36 8,95 0,1665 3,67 4,81 19,6 0,0442 Results show that apple samples of organic vs. conventional farming systems and different varieties can be classified by quantitative descriptive analysis. The variety in this study was Macintosh. Our results show that a significantly higher firmness of the skin for organic samples can be observed in this controlled study for other varieties (Golden Delicious and Elstar), too. Beside that, the pulp of organic apples of both varieties was firmer compared to those of conventional ones. Homotuva and Blazek (2006) state, that direct physical measurements and panellists´ evaluation regarding the skin thickness show the same results. The bitterness of the skin, as observed in this investigation can be related to the higher amount of phenolic substances (Weibel et al, 1999). Furthermore, results of the CART-system support the differentiation between apples from organic and conventional farming systems. Measurements of human senses are able to evaluate precisely and reproducible results. Acknowledgements The authors thank Dr. Nicolas Busscher (University of Kassel) and Statcom for providing the CART system as well as Prof. Dr. G. Rahmann (FAL-OEL) for coding and distributing the apple samples and the Ministry (BMELV) for financial support of the work (BÖL-02OE170/F). References Bourn, D., Prescott, J. (2002): A Comparison of the Nutritional Value, Sensory Qualities, and Food Savety of Organically and Conventionally Produced Foods. Food Science and Nutrition, 42(1):1-34. Breimann, L. J., Freidmann, H. , Olshen, R. A. , Stone C. J.(1984): Classification and Regression Trees. Wadsworth International Group, Belmont, California Casutt, M.M., Guggenbuehl,B., Kellerhals, M. (2006): Consumer reaction on new disease resistant apple cultivars. Monica Maria Casutt and Barbara Guggenbuehl, HSW-University of Applied Sciences Wädenswil, Switzerland b.guggenbühl@hswzfh.ch Homutova, I., Blazek, J. (2006): Differences in fruit skin thickness between selected apple (Malus domestica Borkh.) cultivars assessed by histological and sensory methods. Hort. Sci. (Prague) 33(3):108 – 113 Roth,E., Berna, A.Z., Beullens, K., Franck, C., Lammertyn, J., Schenk, A., Nivola,B (2005): A Comparative Study of Quality Attributes of Integrated and Organically Produced Apple Fruit. Frutic 05, September 12-16, Montpellier, France Stone, H.L., Sidel, J.L. (1993): Sensory Evaluation Practices, 2nd ed. Academic, San Diego. Theuer, R. (2006): Do organic fruits and vegetables taste better than conventional fruits and vegetables?. State of Science Review. The Organic Center, GB Weibel,F.P., Bickel, R., Leuthold, S., Alföldi, T., Niggli, U. (1999): Are organically grown apples tastier and healthier? A comparative field study using conventional and alternative methods to measure fruit quality. Proceedings of the 12th International IFOAM Scientific Conference, IFOAM, 147 -153.