Low O2-induced changes in pH and energy charge in pear fruit tissue

Nanos, George D.; Kader, Adel A.

doi:10.1016/0925-5214(93)90063-9

Cited by 38 publications

(21 citation statements)

References 18 publications

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“…Also under these conditions, ethylene synthesizing enzymes get inactivated to prolong shelf life. On the other hand, very high CO 2 levels can introduce physiological stress in the fruit and result in unfavourable values of ATP/ADP ratios (Nanos and Kader 1993). These factors strongly point to the existence of an optimum level of CO 2 which, based on the present study, appears to be around 50%.…”

Section: Weight Losssupporting

confidence: 46%

Effects of modified atmosphere packaging on quality of ‘Alphonso’ Mangoes

Ramayya

Niranjan

Duncan³

2011

J Food Sci Technol

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Postharvest quality of Alphonso mangoes (Mangifera indica L) is vital to ensure proper ripening and good quality. 500 g mature green mangoes, were subjected to three pre-packaging hot water dips (20, 30 & 40°C) for 40 min, two packaging films (OPP unperforated and perforated), using three levels of gas concentrations of 25,50 and 75% v/v CO 2 treatments (balance N 2 ) and stored at 10°C for 21 days. During the storage period headspace gas composition, weight loss, ascorbic acid, pulp firmness, external fruit colour and overall quality score were measured to determine optimum storage conditions. The most effective postharvest condition was found to be dipping in water maintained at 40°C for 40 min, followed by packaging under 50% CO 2 in bags made of unperforated film when compared to mangoes packed under 25 and 75% CO 2 which showed deteriorated quality including spoilage and mould. Good keeping quality of at least 21 days was achieved under these conditions, which was much superior to the control samples that showed deterioration after 12 days of storage.

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Section: Weight Losssupporting

confidence: 46%

Effects of modified atmosphere packaging on quality of ‘Alphonso’ Mangoes

Ramayya

Niranjan

Duncan³

2011

J Food Sci Technol

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“…Cellular pH is very important in the regulation of metabolism. The cellular functions that take place in the cytosol are optimal at a pH near neutral (Nanos and Kader, 1993). Acidification of the cellular pH is potentially hazardous to cells.…”

Section: Resultsmentioning

confidence: 99%

“…Uncontrolled cytoplasmic acidification, caused by a failure to stop lactate production and eventually by proton leakage from the vacuole, is the cause of cell death (Menegus et al, 1989). To maintain the neutral pH of the cytoplasm, protons are transported across membranes or are consumed or produced by cellular metabolism (Nanos and Kader, 1993). There is a constant tendency for protons and undissociated acids to leak through the vacuolar membrane into the cytoplasm (Chervin et al, 1996).…”

Section: Resultsmentioning

confidence: 99%

Effects of Short-term Exposure to Low Oxygen Atmospheres on Phsyiological Responses of Sweetpotato Roots

Imahori¹,

Kishioka²,

Uemura³

et al. 2007

J. Japan. Soc. Hort. Sci.

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Sweetpotato roots were stored under a continuous flow of 0% or 1% O 2 (balance N 2 ) or air for 7 days at 20°C to study the effects of short-term exposure to low O 2 on their physiological responses and quality. During the course of the experiment, no visible signs of injury or decay were observed. However, low O 2 treatments increased the soluble solid content and weak off-odors were detected by olfactory evaluation in roots stored at 0% O 2 . The intensity of off-odors increased as the concentrations of acetaldehyde and ethanol increased in roots during storage. Ethanol concentrations were higher than those of acetaldehyde, which remained low during storage in 1% O 2 and air, but increased greatly in roots stored at 0% O 2 . Pyruvate decarboxylase (PDC) activities in roots exposed to 0% or 1% O 2 increased by 3.1-and 2-fold respectively over levels in roots stored in air by day 7. Alcohol dehydrogenase (ADH) activities in roots exposed to 0% or 1% O 2 increased by 1.6-and 1.7-fold respectively over levels in roots stored in air by day 7. ADH-specific activity was about 10-times that of PDC. The pH of root homogenate exposed to air remained constant, whereas the pH increased and decreased, respectively, in roots stored at 0% or 1% O 2 . PDC showed stability over the pH range 5.5-7.0, whereas ADH exhibited stability over the pH range 6.0-7.5. The Km of PDC in sweetpotato was 0.56 mM for pyruvate, whereas the Km of ADH was 0.19 mM for acetaldehyde. From these results, there may be some potential for the short-term exposure of sweetpotato roots to low O 2 in place of low temperature treatment to prolong shelf-life, although ethanol fermentation may be accelerated under low O 2 atmospheres.

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“…Carbon dioxide has the potential to change the pH of tissue and cell sap (Siriphanich and Kader, 1986). In normal air the cytoplasmic pH of Bartlett pears was estimated to be 7.4; however, when oxygen was reduced to 0.25 kPa this value decreased to approximately 7 (Nanos and Kader, 1993), and under elevated carbon dioxide the cytoplasmic pH dropped to 6.6. Non-latent pear tyrosinase is active at pH values ranging from 4 to 7 (Espín et al, 2000).…”

Section: Polyphenol Oxidase and Decompartmentationmentioning

confidence: 99%

“…On the basis of observations described by Veltman et al and Frenkel and Patterson (Frenkel and Patterson, 1973) it is hypothesised that brown core results from the decompartmentation of cellular compartments, caused by membrane disintegration (Figure 3). Decompartmentation is accompanied by a large decrease in cellular pH, since the vacuolar pH (the vacuole occupies a large part of the cell's volume) is low (3.8-4.4 (Nanos and Kader, 1993)). The average pH of the cell after decompartmentation was estimated to be about 5, which means an activation of non-latent tyrosinase of 80% (Espín, Veltman et al, 2000).…”

Section: Polyphenol Oxidase and Decompartmentationmentioning

confidence: 99%

A Proposed Mechanism Behind the Development of Internal Browning in Pears (Pyrus Communis Cv Conference)

Veltman¹,

Peppelenbos²

2003

Acta Hortic.

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Storage of pears under low oxygen levels (0.5-1.0 kPa) leads to decreased ascorbic acid and ATP levels, a lower ATP-production, and to internal browning, a storage disorder in pears. Addition of 5 kPa carbon dioxide to the storage atmosphere increased the severity of this disorder. Experiments showed that anoxia can result in off-flavours, but not in internal browning. Internal browning is caused by brown pigments (melanins), which are formed due to oxidation of vacuolar polyphenols under the influence of tyrosinase (EC 1.14.18.1). We hypothesise that internal browning is initiated by a combination of oxygen radical action and a lack of maintenance energy for, amongst others, the regeneration of antioxidants. The two factors together lead to decompartmentation, bringing tyrosinase from the plastids and substrates from the vacuole together.

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Low O2-induced changes in pH and energy charge in pear fruit tissue

Cited by 38 publications

References 18 publications

Effects of modified atmosphere packaging on quality of ‘Alphonso’ Mangoes

Effects of modified atmosphere packaging on quality of ‘Alphonso’ Mangoes

Effects of Short-term Exposure to Low Oxygen Atmospheres on Phsyiological Responses of Sweetpotato Roots

A Proposed Mechanism Behind the Development of Internal Browning in Pears (Pyrus Communis Cv Conference)

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