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

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

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

First attempts of linking modelling, Postharvest behaviour and Melon Genetics

The onset of climacteric is associated with the end of melon fruit shelf-life. The aim of this research was to develop practical and applicable models of fruit ripening changes (hardness, moisture loss) also able to discriminate between climacteric and non-climacteric behaviour. The decrease in firmness was measured non-destructively by flat-plate compression; moisture loss was measured by weight loss. A set of 13-15 near-isogenic lines (NILs) derived from the climacteric line SC3-5 was used to verify the relationship among the climacteric behaviour and ripening related changes (weight loss, softening and color) during two consecutive seasons. The biological variance models for moisture loss and firmness followed a simple exponential behaviour that explained more than 90% of the total variance. Results of the analyses using these models could not be linked to properties of near-isogenic lines like climacteric behaviour, ethylene production or skin thickness. The results suggest that the phenotype is more important than genotype, when considering mean values. These results seem to suggest that relations may exist between the different processes and properties of NILs on an individual basis, not on mean values

The Relationship of Malay Kampung Organization, Facility, and Activity with the Malaysian Homestay Program : Focusing on the Management of Sungai Sireh Homestay at Selangor

論文特集

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

Optical Absorption and Scattering Phenomena in 'Jubileum' Plums in Relation to Their Colour Properties

Absorption and scattering of laser light pulse passing through the fruit determine among others, the optical properties of the product. Efforts have been made in the recent past to utilize innovative techniques such as time-resolved reflectance spectroscopy (TRS) to study the quality aspects of different fruit such as nectarines. These optical properties have been well related to firmness, sugars, acids and other quality attributes. TRS measurements were performed on ‘Jubileum’ plums at two different wavelengths: 670 nm and 758 nm. The fruit were harvested in Norway and brought to Italy under protected conditions. After sorting the fruit by size, TRS measurements were made and the fruit were randomized for different examinations of quality aspects. It was observed that the absorption coefficient (µa) increased for both wavelengths as ripening progressed towards the melting stage of the fruit. The µa values at 670 nm were higher than those at 758 nm. The higher rate in the µa was distinguishable from the third day onwards as the fruit ripened. Similarly, it was interesting to note that the internal colour measured after destructing the fruit related well with the TRS absorption coefficient (µa), i.e., a decrease in the CIE L* (towards darker region) and b* (towards blue) value along with an increase in a* (towards red) from third day of storag

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

Ready to Eat Nectarines - Assuring Quality in the Chain

Time-resolved reflectance spectroscopy, coupled to the modelling of firmness decrease, was used to predict at harvest softening behaviour of nectarines. Selected fruit were used in an export trial from Italy to The Netherlands. Quality assessed after shelf life was in agreement with the predicted firmness for fruit of different stages of maturity, showing that it is possible to select fruit at harvest for different market destinations and prevent transportation of fruit unsuitable for consumption