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Examines small decreases in SBPase cause a linear decline in the apparent RuBP regeneration rate, but do not affect Rubisco Carboxylation capacity. Decrease in the steady-state in vivo maximum regeneration rate of RuBp; Cytochrome b/f complex as a limiting step in whole chain electron transport; Assumptions based on analysis of plants with antinase.

• Slower TCA cycle, upregulated glycolysis and lactic fermentation in severe hypoxia. • Possible uncoupling of alanine from hypoxic adaptation responses in pear fruit. • High succinate level and label near anoxia hinted GABA shunt use or split TCA cycle. • Stalled glycolysis, upregulated TCA cycle and reverse fermentation under reaeration. • Hindered recovery to initial status post reaeration showed confounded time effect. Storage of pears in low oxygen conditions after harvest and before commercialization induces several responses in their metabolism initiating survival, maintenance and low energy expenditure mechanisms. In the present study a metabolomics approach was used in combination with a 13C feeding experiment to elucidate those metabolic responses in pear fruit under a stepwise induced hypoxic profile by monitoring changes in TCA, fermentation, GABA shunt associated metabolites and amino acids. A reoxygenation treatment was added at the end of the experiment to study the post hypoxic recovery mechanisms after prolonged hypoxia. Propagation of label through metabolic pathways was monitored by GC–MS analysis. Results showed successful utilization of 13C pyruvate from pear tissue under normoxia accompanied by fractional enrichment in organic acids, pyruvate and TCA cycle derived amino acids. Initiation of hypoxia at 5 kPa O 2 resulted in drop of fractional enrichment in malate, fumarate, citrate, valine, glutamate and alanine but not in α-ketoglutarate and succinate. Further induction of severe hypoxia (0.5 kPa O 2) resulted in a decrease of the TCA cycle activity, initiation of fermentation and primary evidence of an upregulated alanine-α-ketoglutarate shunt, a trend that continued until the 0.2 kPa O 2 incubation. Sucrose and fructose decreased below 0.5 kPa O 2 with a sharp increase of phosphorylated sugars that dropped by the end of the treatment. Reoxygenation caused upregulation of the TCA cycle but not glycolysis, reversed fermentation activity and a drop in concentration of all amino acids. Results were in line with common responses of plants under hypoxia and post anoxia recovery mechanisms and suggest that different mechanisms are implemented between normoxia and reoxygenation after prolonged hypoxia. [ABSTRACT FROM AUTHOR]

A method was developed to correct real-time measurements of the respiratory quotient (RQ) of pome fruit for gas leakage of a cool room. The method is based on a general leakage model that was simplified by performing sensitivity analysis of the contribution of the pressure driven and concentration driven gas transport terms. The analysis showed that pressure driven leakage was dominant over diffusive leakage. The methodology was validated successfully using an empty storage container at 0.4 kPa O 2 and 1.3 kPa CO 2. A sensitivity analysis using virtual storage experiments showed that the error of the RQ estimates with leak correction was 0%, while without leak correction they increased to above 700%. Finally, the validated model was successfully implemented in an automated RQ-DCA control system using ‘Braeburn’ apple fruit ( Malus × domestica ‘Braeburn’ 2 x ). RQ estimates without leakage correction were heavily biased when leakage of atmospheric air into the storage container occurred and would lead to erroneous control of the storage atmosphere composition. With the developed leakage correction, RQ measurements were found to be accurate during decreasing as well as increasing atmospheric air pressure. [ABSTRACT FROM AUTHOR]

A novel type of dynamic controlled atmosphere storage (RQ-DCA) was developed to control O 2 and CO 2 partial pressures in storage containers for apple fruit automatically, based on measurements of the stored fruit respiratory quotient (RQ). ‘Granny Smith’ apples were stored under RQ-DCA and the effect on fruit quality immediately after storage as well as during subsequent shelf life was investigated and compared to the effect of regular CA and regular CA storage with 1-MCP (SmartFresh SM ) treatment. The RQ-DCA system managed to control O 2 and CO 2 partial pressures in the storage container in an autonomous way. During RQ-DCA storage, the RQ breakpoint was found to vary between 0.25 kPa and 0.4 kPa O 2 . However, difficulties to obtain a reliable RQ measurement were observed at very low oxygen levels due to reduced fruit respiration and when the pressure of the storage container increases due to increased atmosphere pressure due to leakiness of the storage container. Superficial scald was found to be controlled almost completely during storage with RQ-DCA and the effect remained visible during up to 14 days of shelf life. Magness-Taylor firmness and skin color (hue angle) were found to be significantly higher after RQ-DCA storage compared to conventional CA storage and were comparable to these of fruit stored with regular CA after 1-MCP treatment up to 7 days of shelf life at 18 °C. In-fruit ethanol concentrations were found to be very low (<0.028 g L −1 ), indicating the RQ-DCA system managed to store the fruit close to the anaerobic compensation point but the fruit metabolism did not shift from aerobic respiration to fermentation. [ABSTRACT FROM AUTHOR]

Oranges and lemons can be affected by the physiological disorders granulation and endoxerosis respectively, decreasing their commercial value. X-ray radiographs provide images of the internal structure of citrus on which the disorders can be discerned. An image processing algorithm is proposed to detect these disorders on X-ray projection images and classify samples as being affected or not. The method automatically segments healthy and affected tissue, calculates a set of image features and uses these to classify the images using a naïve Bayes or kNN classifier. The developed method avoids the need for labour-intensive destructive sampling and allows for non-destructive inspection of all fruits while preventing losses due to destructive sampling. The proposed algorithm classifies 95.7% of oranges and 93.6% of lemons correctly. The classification method is fast, robust to noise and can be applied to any existing inline X-ray radiograph equipment. [ABSTRACT FROM AUTHOR]

The choice of harvest time and low oxygen storage conditions are crucial parameters in the commercialization of 'Conference' pear and the prevention of market losses. To elucidate the effect of harvesting time and hypoxia on the metabolic adaptational responses in pear fruit, a 13C-feeding experiment was performed. Pear tissue disks obtained from fruit harvested at optimum harvest time, or 1 week earlier or later (commercial, early, and late maturity stages, respectively) were exposed for 24 h to 21 kPa O 2 followed by 24 h incubation at 0.2 kPa O 2 at a constant temperature of 18 °C in a liquid medium containing [U13C] sodium pyruvate. Results showed high fractional enrichment of organic acids, succinate, α-ketoglutarate and lactate, and amino acids, glutamate, and alanine, during hypoxia for all harvesting times suggesting a downregulated TCA cycle stopping at succinate, as suggested by its accumulation, and a possible upregulation of the γ-aminobutyric acid (GABA) shunt. Increased concentration of alanine under hypoxia only in late pears was connected to increased endogenous levels of ethanol and acetaldehyde prior the experiment and lower lactate enrichment. Concentration and fractional enrichment of the optimum harvest time under 0.2 kPa O 2 were compared to previously published data from a similar experimental setup where a 4-day gradually declining hypoxic prolife from 21 kPa to 0.2 kPa was implemented. Results showed similar enrichment for all TCA cycle organic acids. Faster label propagation of lactate in the pre-treated tissue suggested faster adaptational mechanisms and an already initiated hypoxic response while higher concentration and enrichment of alanine in the non-acclimated fruit could be evidence of a tissue specific alanine response to sudden oxygen shortage or aneffect of the age of the acclimated sample. • Sucrose and sorbitol increased, organic & amino acids remained stable over harvests. • Signs of on-tree fermentation; 1-MCP potentially inhibiting ethanolic fermentation. • Glycolysis is upregulated under hypoxia and non-circular TCA cycle downregulated. • Label in succinate, α-ketoglutarate but not citrate shows hypoxic GABA shunt action. • Unaltered hypoxic metabolism post acclimation; alanine plays role in abrupt changes. [ABSTRACT FROM AUTHOR]

Abstract: Strawberry breeding programs for strawberry (Fragaria × ananassa Duch.) focus on developing cultivars with enhanced flavor and improved levels of health-related compounds. To assist this trend, a number of techniques were integrated into a single instrumental platform for high-throughput quality analysis of new strawberry cultivars. This platform was used to monitor the intrinsic properties of strawberries during ripening and to identify differences in sensory quality among nine strawberry cultivars. Through multivariate statistical analysis, 1-penten-3-ol was identified as a marker for unripe strawberries, whereas esters as methyl butanoate, pentyl acetate and methyl hexanoate distinguish ripe strawberries. Furthermore, ripe strawberries were characterized by higher sugar levels and decreased acidity and firmness. Additionally, the high-throughput platform could successfully discriminate between the different tested cultivars. [Copyright &y& Elsevier]

Abstract: A model to describe the loss of firmness in apples stored under different temperatures and controlled atmosphere (CA) conditions was developed. Pectin degradation, the synthesis of pectin degrading enzymes and ethylene production were considered to be the main reactions involved. Appropriate kinetic equations for these reactions were proposed. To estimate the parameters of the model, firmness and ethylene emission data were collected from ‘Braeburn’ apples harvested at three different stages of maturity and stored at 1°C under different CA conditions followed by shelf life. The model could explain up to 83.64% of the total variance of the measured data. [Copyright &y& Elsevier]

Abstract: Tomato is an important crop in terms of its economic and nutritional value. Tomato fruit quality is a function of metabolite content, which is prone to physiological changes related to fruit development and ripening. The aim of this work was to use a metabolomic approach to characterize compositional changes (sugars, acids and amino acids) of tomato during preharvest fruit development, ripening, and postharvest shelf-life. Gas chromatography–mass spectrometry was used to identify both polar and volatile metabolites that were involved in fruit development and ripening. Characteristic metabolites for the various fruit developmental stages were identified. Mannose, citramalic, gluconic and keto-l-gulonic acids were shown to be strongly correlated to final postharvest stages. During on-vine ripening, an increase was observed for the major hexoses, glucose and fructose, cell wall components such as galacturonic acid, and for amino acids such as aspartic, glutamic acid and methionine. Major changes were also observed at the level of the TCA cycle, showing a decrease in malic and fumaric acids, and accumulation of citric acid. [Copyright &y& Elsevier]