SADD: STOCHASTIC ANALYSIS OF DESTRUCTIVELY MEASURED DATA - POSSIBILITIES TO INCLUDE BIOLOGICAL VARIATIONS IN STATISTICAL ANALYSIS

Three techniques are presented to include the structural variation always present in measured data in statistical analysis. The methods are investigated and compared using cross sectional data, generated based on an exponential model as if gathered by destructive measuring methods. All three methods are based on optimising objective functions based on the data and the biological shift model. These objective functions are calculated for each separate measuring point in time either according the specific density function belonging to the model applied, or after conversion into biological shift factors (also according to the model applied) according to a Gaussian distribution. The procedures used need to be improved, embedded in the existing statistical framework and all available statistical expertise and skills need to be combined into robust procedures capable of analysing everyday data

Quality modelling

For modelling product behaviour, with respect to quality for users and consumers, its essential to have at least a fundamental notion what quality really is, and which product properties determine the quality assigned by the consumer to a product. In other words: what is allowed and what is to be avoided when modelling product behaviour in terms of quality and acceptabilit

Modelling postharvest quality behaviour as affected by preharvest conditions

Some hundred years ago, wise men decided that preharvest research and applications had to be regarded separated from the postharvest handling and behaviour. Over the years, both areas developed completely separated. Control over both areas was obtained by different companies and advisory boards, with mostly not too good means of communication between them. This decision hampered seriously the consistent and integral development of knowledge on food production and usage. Bridging the gap between all the knowledge and expertise available in the preharvest area of growing food and the postharvest area of storing and processing food, has become and is still becoming more and more important over the last couple of years. In this paper, based on theoretical considerations, on plausible (but unproven) mechanisms and applying the fundamental rules of chemical kinetics, a pathway to deduce general and generic models is developed towards a possible approach to integrate all available knowledge. Still the validity of this approach is not proven. However, a number of examples from both the applied as well as the fundamental point of view are elaborated to indicate such an interaction exists, and to indicate how to tackle the modelling problem. The examples range from physiological disorders like core brown, internal brown, chilling injury and the biological age of individual tomatoes in truss tomatoes as related to the maturity at harves

The development of a model to describe the influence of temperature and relative humidity on respiration rate of prickly pear cactus stems in reduced O2 conditions

Respiration rate (RO2) of prickly pear cactus stems (Opuntia spp.) was measured as a function of 4 temperature (T) and 6 relative humidity (RH) combinations for O2 partial pressures between 15 and 0.8 kPa, which were considered to support aerobic respiration. The rate of respiration (RO2) was determined based on O2 depletion of the atmosphere in sealed containers containing 1 kg of stems. The O2 partial pressure declined linearly over time and the slopes of the fitted lines were used to calculate the rate of O2 uptake. The rate of O2 uptake increased with increasing temperature and decreased with increasing RH. The respiratory rate at 25°C was approximately 30 to 40 times higher than at 5°C. The respiratory rate at 65% RH was between 30 and 90% greater than at 90% RH, depending on the temperature. Data for ln(RO2) for each RH level were regressed against the inverse of the T (K-1) to determine Arrhenius constants and calculate the apparent Ea of respiration for the six RH conditions. The Ea was similar for each RH level, varying between a low of 113 to a high of 131 kJ•mol-1. An equation having an R2 of 0.95 was developed describing respiration as a function of RH and T (°C) using only four constant

Consumers and Food Choice: Quality, Nutrition and Genes

The quantity and quality of food needed for reproduction differs from nutritional needs for health and longevity. The choice of food type and amount is driven by our genetic need for growth and reproduction, not for long term health. So, fast digestible food, rich in energy is searched for. We humans share that drive with almost all animals. The energy carrying nutrients in processed food are more accessible than in the same unprocessed food. That leads to an ever increasing level of processing, and an ever decreasing consumption of raw fruits/vegetables and home cooked meals. In the past, with alternating conditions of food shortage and food abundance, overeating in times of prosperity was a reproductive advantage. However, high energy food becomes a severe nuisance in the age of permanent food abundance. Obesity and heart diseases spread through the developed world. That behaviour is rooted in our genetic instincts. Cultural based sensorial preferences, induced mostly in childhood by an epigenetic mechanism, present a variation around the instinctive rooted preferences. Food choice based on reflective decisions appears of minor importance. Nevertheless, all government campaigns against over-eating appeal to reason, not to instinct. We are faced with a permanent dichotomy between what is good for reproduction and what is good for health. This occurs not only in what and how we eat, but also in all neighbouring areas on the edges of food science, biology, social science, medicine and ethics

Effects of ca treatments and temperature on broccoli colour development

Broccoli combines high contents of vitamins, fibres and glucosinolates with a low calorie count and is sometimes referred to as the ‘crown jewel of nutrition’. Colour is one of the most important quality attributes of broccoli, and yellowing due to senescence of broccoli florets is the main external quality problem in the broccoli supply chain. Controlled Atmosphere (CA) is a very effective method to maintain broccoli quality but the effects of CA on colour retention have not been studied extensively. The aim of this paper is to characterise the colour behaviour (measured by RGB colour image analysis) of broccoli as affected by CA and temperature. Data on colour behaviour and gas exchange were gathered for broccoli heads that were stored in containers at three temperatures and subjected to four levels of O2 and three levels of CO2. Gas conditions and temperature have a clear effect on the colour change of broccoli especially at low O2 in combination with high CO2. An integrated colour model is proposed that combines a colour model with a standard gas exchange model. The colour model is based on three differential equations describing the formation of (blue/green) chlorophyllide from the colourless precursor, the bidirectional conversion of chlorophyllide into (blue/green) chlorophyll, and the decay of chlorophyllide. During the first step of building the integrated model, gas exchange data were analysed simultaneously using multi response regression analysis. No fermentation was encountered for this batch of broccoli. During the second step it was found that only one of the reactions of the colour model, the decay of chlorophyllide, is affected by the gas conditions. In the final step, a multi-response approach was applied where gas exchange parameters were estimated using the gas exchange model, the colour parameters were estimated using the colour model with both models linked via the reaction rate constant affected by the gas conditions. Such a calibrated, integrated, model could be used as a tool for predicting colour change in the postharvest chain

Benefits of fundamental modelling : the case of physiological disorders

A model was developed assuming that the occurrence and the development of physiological disorders are effects of a balance between processes of disorder formation and scavenging of initiating compounds. Based on this (simplified) mechanism and applying the fundamental rules of chemical kinetics, the differential equations can be derived. The observed effects depend on initial levels of some nutrients (N), free radicals (Ra) and scavenging activity (SS). All three types of compounds do depend on the growing conditions prior to harvest, and hence on season, weather and climate. Postharvest development of disorders (PD) depends also on conditions during storage, e.g. temperature and CO2 level. Thus their influence was incorporated into a model based on fundamental knowledge in that sphere. The benefit of the developed model is that it allows simulating very different ranges in type of development of disorder. From very fast and reaching high level of occurrence, very fast but stabilised at low level of occurrence, to slow but reaching high level of occurrence, and slow and stabilised at low level of occurrence. And of course simulating of cases where the disorder occurrence is not observed at all. The model was checked against measured data on pears, indicating that the approach seems to be realistic and powerful enough to pursue. Existing data are however gathered in a manner not suitable for this approach. Therefore further studies on dynamics of physiological disorders require improvement of experimental methods

pH in Action

Based on fundamental chemical relations, well-established in chemical engineering and chemical technology over almost a century, the effects of pH in food and agricultural products will be deduced for different situations and processes. Based on simple equilibria and dissociation of water, salts, acids and bases, and considering the reaction of hydrogen ions in these food-related systems, simple and reliable formulations are developed capable of describing surprisingly well the discoloration of blanched vegetables and the activity of enzymes in different buffered and unbuffered systems. The line of reasoning is generic and can be applied repeatedly to different problems, situations and processes

Biological Variance in Agricultural Products. Theoretical Considerations

The food that we eat is uniform neither in shape or appearance nor in internal composition or content. Since technology became increasingly important, the presence of biological variance in our food became more and more of a nuisance. Techniques and procedures (statistical, technical) were developed. The most widely used are sorting or grading on large-scale operations. Statistical rules were developed on the sampling size to obtain a reliable mean value. Experimental design strategies were developed for efficient research. All the techniques used are rather empirical and only loosely connected to the theoretical and fundamental knowledge we do have. An effort is made to approach biological variance from a new perspective. The nature of biological variance is traced back to its origin in the processes of production and conversion, primarily driven by the "random" differences in climate and soil. By modelling the dynamics on the level of the individual units that constitutes a batch, rather then modelling the mean value for the batch itself, more fundamental models can be developed. These more fundamental models are generic in nature and describe changes in product properties for all kinds of circumstances like growing area, seasonal effects, harvest maturity and storage temperature