Introduction

The sharp increase of vineyards under organic and biodynamic management as well as the consumption of these wines show the interest of winegrowers and consumers for environmentally friendly viticulture. In response to this trend a longterm randomized field trial was established in Geisenheim, Germany, to compare and evaluate the different wine production methods: integrated, organic and biodynamic management. The three management systems were evaluated according to their impact on soil quality, product quality and wine quality. But also the impact on the physiology of the plants, pests and diseases was examined. Image forming methods such as biocrystallisation, capillary dynamolysis and circular chromatography were applied to assess the management systems and quality characteristics of the product. As these image forming methods are especially used in biodynamics the importance of not only outer product quality but also the inner characteristics of a product such as ripeness and freshness are important.

The biocrystallisation method proved to be a valuable instrument to determine the management system from a certain grape juice. It is the most advanced and scientifically proven image forming method and based on the following phenomenon: Specific crystallisation patterns are formed on a round glass plate when a copper chloride solution is mixed with an organic additive, e.g. the different grape juices. The juice affects the patterns of crystallisation. During that process needle bundles are formed which show the inner quality and form of the product, e.g. aging of juices. As a result not only the inner quality of the product can be analyzed but also the cultivation method can be determined.

Biodynamics and quality

The biodynamic cultivation system has proven to increase the natural resistance of grapes in climatic difficult years as well as the microbiotic activity in vinification.

Maintaining the internal form and internal characteristics are important quality aspects. Biodynamic production contributes positively to minimize storage loss of food products which is important for marketing and sales.

In contrast, chemical analysis of different grape juice from different management systems could distinguish between organic or conventional production. However, the process of biocrystallisation is able to determine and show quality characteristics such as freshness or the ripeness status of grape juice from different management systems and is therefore important in analyzing quality characteristics of food products.

Material and Methods

The vineyard field trial was established in Geisenheim, Germany and was managed under three different management systems: Good agricultural practices (integrated), organic and biodynamic. After harvest, juice samples were collected from each management system and analyzed with the three image forming method biocrystallisation, capillary dynamolysis and circular chromatography. The concentration of the juice samples mixed with an analysis substance such as copper chloride or silver nitrate varied as well as aging patterns of the samples. Day 1 was considered as fresh followed by day 2 and days 5 which was considered as „aged“. After analysis with the three image forming methods the pictures were analyzed visually first by the researchers followed by the evaluation by a selected and trained panel.

Results

The three image forming methods show different results. The capillary dynamolysis showed no visual effect between the three management systems. It could be observed that samples from biodynamic and organic management showed fewer signs of aging and clearer forms when biocrystallisation was applied.  The needle bundles show the different aging status of the juices. Fine and regularly or clear needle bundles show the young age of the juice whereas coarse and chaotic needle bundles show clear signs of aging and less quality. The biodynamic management can be distinguished by its fine needle bundles on the picture whereas coarse and chaotic arrangement of needles can be observed in the integrated management system picture. The organic management system can be found within these two groups. It can be concluded that the juices of the integrated method show clearer and faster signs of aging.

A panel of 8 people evaluated the biocrystallisation pictures and highlighted the fact that aging of the juice samples can be very well determined from the pictures.

The method of circular chromatography could clearly show the management system under which the grapes were produced whereas the biocrystallisation could show more quality oriented effects. Therefore, it can be determined that the slower aging signs of juice is a sign of quality.

Conclusions

The study proved that the image forming methods show a clear hierarchy of form strength and juice aging. The biodynamic management system has the strongest form expression and least aging signs followed by the organic and the integrated management system. The assumption is supported that different management systems influence plant physiology and the final quality characteristics of the product.

Further research needs to be conducted to evaluate the quality characteristics with image forming methods after vinification of the grape juice as well as linking the obtained results to chemical analysis.

Note

The process of circular chromatography or the chroma test is one of the image forming methods. On a round chromatography paper a circle of 4 cm is impregnated with a silver-nitrate solution. After a drying time of some hours the organic additive ascents and after the impact of diffuse room light the pictures are formed. As such the distinction of quality of different products can be determined.

Cappilary dynamolysis

In this image forming method in a glas cylinder a chromatography filter paper is placed on which different solutions with water (e.g. 50% grape juice and 50% water) are left to run through the filter. After a drying period a silver nitrate solution or gold chloride solution is applied and runs through the paper as well until it has reached or passed the former product. Finally, the chromatogram is left to dry under light after which different color and patterns develop which can be used to evaluate the quality of different food products from different production systems.

Link to the study: https://oeno-one.eu/article/view/2548#

Athmann M., Bornhütter R., Fritz J., Geier U., Kauer R., Meissner G., Schulz H. (2020). Quality Assessment of Grape Juice from Integrated, Organic and Biodynamic Viticulture Using Image Forming Methods. Oeno One, volume 54, issue 2.