Gaby Mergardt

Standardization of the Biocrystallization Method for Carrot Samples

ABSTRACT The growing organic market demands methods which can describe food quality within the organic system (authentication). Several studies indicate that methods, such as the biocrystallization method, are suitable for this question. More or less reproducible crystallization patterns emerge when an aqueous dihydrate cupric chloride solution with plant extract is crystallized on a glass dish. The emerging patterns are characteristic of sample material. To be applied in routine analysis for example for authentication of organic products, the biocrystallization method has to be standardized. After the laboratory process was documented and a computerized pattern evaluation tool was further developed and applied, the method was standardized for selected carrot samples, which is described here. For standardization, several factors of influence were tested and the reproducibility between three different laboratories in the EU was investigated. The method is able to differentiate patterns from samples from different farming treatments and processing steps as statistically significant. This represents a significant step forward beyond the state of the art.

Standardization and validation of the visual evaluation of biocrystallizations.

ABSTRACT The biocrystallization method has been used as a holistic method for evaluating food samples since the 1930s and has, as recent reviews have concluded, been successful in discriminating farming systems in several studies. However, it is noted that a standardization and validation for more objective means of evaluation of biocrystallization pictures and a clearly defined and communicable language, as well as possibilities for verification, are still lacking. During the years 2002–2006 a project for standardizing and validating the visual evaluation of these biocrystallizations took place, performed by a group consisting of three European research institutes. As no pre-set methodology nor norms for the visual evaluation existed, the choice was made to work according to existing norms on sensory analysis and to adapt these to the visual evaluation. The main norm, ISO-Norm 11035, for establishing sensory profiles was adapted towards these pictures. A panel was formed, mainly morphological descriptors were selected and defined, a scale with references was established, the panel trained and tested for pictures, produced on the basis of carrots of different qualities. Reliability and validity aspects of the panel, as well as the structure of the set of criteria were evaluated. According to standard rates for diverse statistical tests the panel has been validated for the evaluation of carrots with a defined set of descriptors. The set of descriptors contains sub-domains which can be used for further development of the evaluation method, towards a more integrated, holistic ‘Gestalt’-evaluation, and towards finally interpretation of these pictures. The followed process and results are unique in connection to this method.

Evaporation influences on the crystallization of an aqueous dihydrate cupric chloride solution with additives

The overall structure of the crystallization results of dihydrate cupric chloride with additives in a petri dish is affected by the duration between the beginning of the evaporation and the start of the crystallization. Experiments done with polyvinylpyrrolidone and freeze-dried carrot as additive are compared with those of the additive free case. The dependency of dewetting on the dihydrate cupric chloride amount is discussed in terms of depletion of the solution and the surface tension properties of the system. The possible influence of the depletion is depending on the moment the crystallization starts. This is defined by the size of the evaporated area on the dish.

Development and Performance of Crystallization with Additives Applied on Different Milk Samples

Crystallization with additives is developed on milk samples from different processing treatments. Performance tests are carried out based on structure analysis of the crystallization patterns. Crystallization with milk as additive is applied following changes in milk after different processing treatments. When an aqueous cupric chloride dihydrate solution crystallizes in the presence of milk as additive, specific patterns emerge, which can be evaluated by image analysis. Milk samples were heated and homogenized in a pilot plant and characterized by various parameters. Furthermore, milk samples from the market were tested. Patterns from milk after heat treatment and homogenization are significantly different from those derived from untreated milk. The experiments could be reproduced for other milk samples, on different days and in another laboratory.

Differentiation of organic and non-organic winter wheat cultivars from a controlled field trial by crystallization patterns

BACKGROUND There is a need for authentication tools in order to verify the existing certification system. Recently, markers for analytical authentication of organic products were evaluated. Herein, crystallization with additives was described as an interesting fingerprint approach which needs further evidence, based on a standardized method and well-documented sample origin. RESULTS The fingerprint of wheat cultivars from a controlled field trial is generated from structure analysis variables of crystal patterns. Method performance was tested on factors such as crystallization chamber, day of experiment and region of interest of the patterns. Two different organic treatments and two different treatments of the non-organic regime can be grouped together in each of three consecutive seasons. When the k-nearest-neighbor classification method was applied, approximately 84% of Runal samples and 95% of Titlis samples were classified correctly into organic and non-organic origin using cross-validation. CONCLUSION Crystallization with additive offers an interesting complementary fingerprint method for organic wheat samples. When the method is applied to winter wheat from the DOK trial, organic and non-organic treated samples can be differentiated significantly based on pattern recognition. Therefore crystallization with additives seems to be a promising tool in organic wheat authentication.

Standardization and Performance Test of Crystallization with Additives Applied to Wheat Samples

Crystallization with additives is developed and standardized on wheat samples from different origins and varieties. When an aqueous cupric chloride dihydrate solution crystallizes in the presence of wheat flour as additive, specific patterns emerge which can be evaluated by image analysis. Performance tests are evaluated by structure analysis of the resulting crystallization patterns. Different factors of influence were tested, from which milling of the kernels in the sample preparation and the mixing ratio of cupric chloride and additive on the plate and the evaporation and crystallization were identified as the most crucial ones which have to be standardized. Comparisons between different laboratories indicate that the method can be used in another laboratory, but chamber conditions have to be documented and controlled.

Standardization and performance of a visual Gestalt evaluation of biocrystallization patterns reflecting ripening and decomposition processes in food samples

The biocrystallization method is based on the phenomenon that additive-specific, dendritic crystallization patterns emerge when an aqueous dihydrate cupric chloride solution with additives is crystallized on a glass plate. The patterns reflect physiological processes like ripening and decomposition and are applied in differentiating food samples according to feeding regime, production system and degree of processing. The method has been used for decades in organic food quality assessment from an ontological holistic stance. The patterns are evaluated visually and by means of computerized image analysis. The present study describes the development of the visual evaluation from a morphological description of structural features towards the perception of a Gestalt, a salient, coherent ‘meaningful-whole’, which complies more closely with the pattern formation principle of the method. The methodology was standardized according to ISO-Norms 11035 and 8587 for sensory analysis of food products, adapted for use in the visual evaluation of biocrystallization patterns. Two Gestalts, ‘Ripening’ and ‘Decomposition’, reflected in biocrystallization patterns from diverse agricultural products were characterized, trained on and examined. Based on the statistical evaluation, it is concluded that the panel has become reliable and appropriate for ranking biocrystallization patterns according to the intensity of the two Gestalts. The developed level of Gestalt evaluation of biocrystallization patterns provides a basis towards qualitative interpretative judgements on the food quality of a product relating to quality concepts based on plant physiological processes.

A novel approach for differentiation of milk fractions and polyvinylpyrrolidone with different molecular weight by patterns derived from cupric chloride crystallization with additives

Crystallization with additives is based on self-organization, dendritic crystal growth and subsequent pattern formation. The principle is used as an indicator, differentiating food samples according their treatments and origin. The present study focuses on methodological investigations by taking different milk fractions as well as a single polymer as examples. Both kinds of samples alter the patterns derived from cupric chloride crystallization. The changes can be evaluated by image analysis, when a structure related algorithm is applied. The crystallization with additives seems to be an innovative approach following modifications in various sample types. Potential fields of application may be authentication of samples, following processing treatments as well as other modifications in the sample structure during production.

Advanced panel training on visual Gestalt evaluation of biocrystallization images: ranking wheat samples from different extract decomposition stages and different production systems

ABSTRACT Biocrystallization images are formed in reaction with foods; in the course of the evaporation of the water from food extracts in presence of copper chloride, crystalline structures are formed. The structures are known to reflect food quality, such as degree of decomposition. Individual expert evaluators have suggested that crystallization images of samples from organic production contain fewer signs of decomposition and that this feature can distinguish organic foods from their conventional counterparts. To further assess the scientific merits of this methodology, a panel of nine evaluators was trained in the visual assessment of biocrystallization images and asked to rank the visual Gestalt decomposition level of encoded images of wheat extracts from i) the same production system at five different decomposition stages and ii) organic production systems vs. conventional production systems aged for the same amount of time. The panel was trained by supervised classification on the basis of defined criteria and intra- and inter-personal variation was assessed. Statistical evaluation showed that the panel was highly reliable, and that the method was appropriate for ranking biocrystallization images of five different decomposition levels. Furthermore, images of samples from organic or conventional production systems could be distinguished with high agreement according to their Gestalt decomposition level with fewer signs of decomposition in the images of organic samples. The rank order between the organic systems vs. the conventional systems was significant.

Application of Crystallization with Additives to Cloudy and Clear Apple Juice

The present study describes the effects of applying the new method crystallization with additives on cloudy and clear apple juice samples in two independent laboratories. The method has been successfully applied to grain and milk samples before. The samples presented here are characterized by means of standard analysis of apple juices and a metabolomic approach (DART-MS). The most evident difference between the two juices is the pectin concentration. Different amounts of sample and cupric chloride change the resulting patterns. The frequency of branching is clearly different between the patterns of the two samples. Based on structure analysis of the patterns, the two apple juice samples can be differentiated. The region of interest (ROI) has a stronger impact on the structure variables for cloudy than for clear apple juice. There is a significant difference between the treatments performed by both laboratories, independent of chamber and day and taking the different repetitions into account. The method principle is based on self-organization processes and not on single compound detection. Therefore, the results from crystallization with additives may complement the other measurement data for a wide range of different foods.