Size development of tomatoes growing in trusses: linking time of fruit set to diameter.

BACKGROUND: Size of fruit is an important issue in determining yield at harvest. Even under controlled conditions, variation between fruit and trusses can be considerable. As an easy to measure indication of size, the diameter of tomatoes growing in trusses was assessed in three experiments with different number of tomatoes per truss, as well as cultivars, and also by varying the level of ions in the recirculated drain water. RESULTS: By applying the von Bertalanffy growth model, more than 99% of the variation present could be explained by the time of fruit set for all tomatoes growing anywhere in the trusses. A linear relationship between time of fruit set and the biological shift factor, an indication of developmental age, was observed. Integrating this linear relationship in the analysis of the diameter data removed one stochastic variable (biological shift factor), effectively halving the number of parameters to be estimated. CONCLUSION: The results of the present study indicate that the major part of the variation present in the diameter of tomatoes growing in trusses is the result of variation in the time of fruit set of individual fruits. The position within the greenhouse (i.e. local differences in assimilates supply) exerted only a minor effect on diameter development. Accordingly, the time of fruit set largely determines fruit size. Likely, growing conditions before fruit set are crucial for final fruit size. The time of fruit set of each tomato in the truss and the local growing conditions within the greenhouse that affect assimilate supply need to be assessed accurately for a reliable size prediction.

Effect of location in the canopy on the colour development of three apple cultivars during growth.

BACKGROUND: Homogeneity in appearance is one of the quality aspects asked for in the supply chain. Decreasing the biological variation in batches of harvested apples (cultivars Braeburn, Fuji and Gala) becomes increasingly important. Skin colour is one of the aspects that determine both optimal harvest and stage of development. Skin colour is affected by location in the canopy. The rules of development of biological variation are now established and will be used on skin colour data. RESULTS: The Minolta colour aspects a*, b* and L* measured before commercial harvest change in a sigmoidal fashion and can be analysed including the biological variation, with a logistic model in indexed nonlinear regression, obtaining explained parts of above 90%. The mechanism of colour change is not affected by state of development or location in the canopy. The location in the canopy affects the intensity of both red and green colouring compounds. The variation in colouration is not affected by the location in the canopy. CONCLUSION: The red-coloured apple cultivar (Gala) depends more on the location in the canopy than the less-coloured cultivars (Fuji and Braeburn). The colour development in Fuji apples is considerably slower, with a much larger variation in stage of development. The location in the canopy affects all aspects of biological variation (biological shift factor and asymptotic starting level of colouration) for all three colour aspects L*, a* and b*, but only the mean value, not the standard deviation. The biological shift factors per colour aspects are linearly related. Once induced, variation remains constant during development.

Appetite for the selfish gene.

In developed countries, where the majority of the population has enough income to afford healthy diets, a large number of the inhabitants nevertheless choose unhealthy nutrition. WHO and FAO strategies to overcome this problem are mostly based on educational means. Implicitly, this approach is based on the presumption that the main causes of the problem are ignorance and culturally acquired bad habits. It has already been shown that wild animals, evidently acting solely on instinct without cultural effects, display tendencies that may damage their longevity: they tend to avoid healthy types of caloric restriction, prefer processed to raw food, and have an excessive intake of food stimulants and proteins when available (Ostan et al., 2009). This paper presents evidence for such nutritional patterns in humans as well and broadens the discourse to include proteins and fats and describes some human biological traits that present important differences between humans and other primates; among them are the human tendency for overeating and the inadequacy of a totally raw diet for human consumption (despite having some advantages for the human immune system). From an evolutionary perspective these strategies offer a biological advantage by enhancing the reproductive capability of the organisms, according to Dawkins' theory of the Selfish Gene. Genomic-based pleasure of such nutrition seems to be the main cause of instinctive nutritional drives. Further research on the process of food acceptance is needed to determine the role and importance of genomic-based pleasure compared to epigenetic or culture-based pleasure. Both, however, seem to be important and very stable factors in human nutritional choice and seem to prevail over conscious factors in food acceptance.

Modelling the biological variance of the yellow aspect of Granny Smith apple colour.

BACKGROUND: The yellow aspect of colour is usually not considered for produce with a green-to-red or a green-to-yellow transition upon ripening. The magnitude of change is simply too small and, additionally, masked by a large variation. The colour of 'Granny Smith' apples, harvested from three orchards at two stages of maturity, was measured individually using the CIE L*a*b* system during storage in a regular atmosphere at three temperatures: 1, 4 and 10 degrees C. A model was developed based on a simplified mechanism, consisting of two consecutive reactions, to describe the development of the apple colour expressed as b* and L* values during storage. RESULTS: Monitoring individual apples made it possible to include and describe the biological variance of colour in batches of apples and to extract information on chilling injury, as a process active at 1 degrees C. All variations could be attributed to a single source related to the amount of yellowing compounds at the moment of harvest, indicating differences in state of maturity between individual apples. The obtained explained part (R(2) (adj)), using nonlinear mixed effects regression analysis was well over 90% for all data combined over more than 3000 observations. CONCLUSION: Orchard location had a slight effect on the mean initial colour value, indicating differences in development stage, most probably due to differences in assessing the harvest date. The magnitude of the variation in these colour values was, however, the same for all three orchards. The behaviour of the green colour aspect (a* value) has been reported separately, as this represents the major change in perceived colour. The changes in b* and L* values are rather small, while the biological variation between the individual fruit is at least of the same magnitude. The model presented here is, as far as known, the first model on b* and L* values for green-coloured products. Analysing b* and L* data using this model provides additional information with respect to the stage of maturity at harvest in a batch or for an orchard of Granny Smith apples. All the variation in the yellow colour aspects could be attributed exclusively to the initial level of yellow compounds.

Mango Firmness Modeling as Affected by Transport and Ethylene Treatments.

More and more, tropical fruit are subjected to accelerated ripening at receiving markets until "ready to eat." We propose a kinetic model that incorporates the effects of temperature and ethylene on the firmness behavior of "Keitt" and "Kent" mangoes. Stiffness of individual mangoes, as measured by the acoustic firmness tester, was measured repeatedly over time. The firmness model assumes fixed levels of ethylene, established after the climacteric peak, that steadily induces production of softening enzymes that subsequently denaturalize. The initial level of these enzymes is assumed to be zero due to either the tree factor for freshly harvested mangoes, or due to chilling injury for reefer transported mangoes. The kinetic parameter set for "Keitt" mangoes was estimated based on a Spanish batch, freshly harvested and ripened under dynamic temperature scenarios, combined with a reefer transported Brazilian batch stored at four constant temperatures. Firmness data from reefer transported batches, from Brazil, Ivory Coast and Mali, stored at four constant temperatures were used to estimate a set of kinetic parameters for the "Kent" mangoes. Only a partial set of "Kent" kinetic parameters could be established due to the often already advanced stage of softening at the time of arrival. The effect of ethylene was investigated by applying external ethylene levels, varying from 0 to 100 µL L-1. The effect of external application of ethylene was modeled by estimating EF, the ethylene factor, being a reflection of the internal ethylene level and ethylene sensitivity. The effect of ethylene application on softening was sometimes huge. For an Israeli "Keitt" batch a fifty times higher EF was found when the firmness behavior of low- (without ethylene application) and high temperature (with ethylene application) stored sub-batches were compared. However, this effect was sometimes also small, especially for reefer transported mangoes. For commercial application, a reliable prediction of the time until "ready to eat" is not possible because of the current inability to assess EF. Nevertheless, the proposed model described mango softening accurately, irrespective of the sourcing area and includes the effects of storage temperature and ethylene application.