Julian Heyes - Academia.edu (original) (raw)

Papers by Julian Heyes

Annual Plant Reviews online

2019 IEEE International Instrumentation and Measurement Technology Conference (I2MTC)

This paper presents a novel technique to measure skin topography of kiwifruit. Fringe projection ... more This paper presents a novel technique to measure skin topography of kiwifruit. Fringe projection has been identified as a rapid, non-destructive way to extract topographical data from fruit skins. In this paper, a detailed methodology of using this technology is outlined. The captured raw data require the filtering process to separate the low frequency component from the high frequency component. A wide range of surface roughness parameters can be extracted from the accompanying proprietary software after filtering. 3D coordinates arranged as a rectangular matrix of height values can be extracted for further image analysis. An experiment on skin topography of kiwifruit has concluded that the technique is able to to quantify the skin difference from different growing environments.

NSNZ 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

New Zealand Journal of Crop and Horticultural Science, 2022

Scientia Horticulturae, 2022

New Zealand Journal of Crop and Horticultural Science, 2022

ABSTRACTTuber quality problems such as skin tears (skinning), rots, browning, shrivelling and wei... more ABSTRACTTuber quality problems such as skin tears (skinning), rots, browning, shrivelling and weight loss in New Zealand-grown export potatoes have caused significant postharvest losses and insurance quality claims from overseas distributors. These quality issues could be attributed to poor management of curing and subsequent storage conditions. This study investigated the effects of various curing and storage conditions (i.e. duration, temperature and relative humidity (RH)) on tuber quality of two potato cultivars, ‘Moonlight’ and ‘Nadine’, that are exported to Fiji. Results have shown that high curing RH (93\%) led to significantly lower skin browning, shrivelling and weight loss in both cultivars, and significantly lower tuber rot in ‘Nadine’ than low curing RH (62\%). Shorter curing duration (7 days) yielded significantly lower shrivelling in ‘Moonlight’, and significantly lower tuber rot in ‘Nadine’, than longer curing duration (14 days) or control (0 day). Percent weight loss was significantly lower in cured potatoes than in control for both cultivars. Curing temperatures (16 or 26°C) and storage RH (65 or 90\%) did not significantly affect the tuber qualities assessed. Therefore, 7 d curing at >90\% RH and at least 15°C is recommended for minimising quality problems occurring during transport of these potato cultivars to distant markets.

Nutrients, 2021

Cancer is one of the leading causes of death globally. Epidemiological studies have strongly link... more Cancer is one of the leading causes of death globally. Epidemiological studies have strongly linked a diet high in fruits to a lower incidence of cancer. Furthermore, extensive research shows that secondary plant metabolites known as phytochemicals, which are commonly found in fruits, have onco-preventive and chemo-protective effects. Apple is a commonly consumed fruit worldwide that is available all year round and is a rich source of phytochemicals. In this review, we summarize the association of apple consumption with cancer incidence based on findings from epidemiological and cohort studies. We further provide a comprehensive review of the main phytochemical patterns observed in apples and their bioavailability after consumption. Finally, we report on the latest findings from in vitro and in vivo studies highlighting some of the key molecular mechanisms targeted by apple phytochemicals in relation to inhibiting multiple ‘hallmarks of cancer’ that are important in the progression ...

Postharvest Physiological Disorders in Fruits and Vegetables, 2019

AIP Conference Proceedings, 2019

Fermentation and drying are two important postharvest processing stages for Theobroma cacao beans... more Fermentation and drying are two important postharvest processing stages for Theobroma cacao beans. In the Fiji Islands, tropical weather conditions favour fermentation but the high relative humidity impedes drying. Slow or intermittent drying leads to product loss from mould growth and spoilage, which is costly for the cocoa industry. Conversely, direct solar drying can lead to unacceptably high temperatures (over 60 °C) and quality loss. Relative humidity can be controlled by applying low cost desiccant technology such as silica gel to dehumidify process air. The effect of dehumidified air on drying fermented T. cacao beans was evaluated at different drying temperatures of 56 °C and 46 °C. A rapid drying rate was achieved for fermented T. cacao beans dried at 56 °C under 10% relative humidity. Drying was slower at 46 °C under 18% relative humidity. Cocoa beans equilibrated to a moisture content <7% in 12 h and 34 h drying time respectively. Quality analyses are now under way to establish which of these drying profiles is preferable as a target for desiccant-assisted indirect solar drying.

New Zealand Journal of Crop and Horticultural Science, 1992

Softening during fruit ripening may be initiated by an increase in proton pumping across the plas... more Softening during fruit ripening may be initiated by an increase in proton pumping across the plasma membrane. This would lower the cell wall pH and loosen acid-labile bonds, as well as displacing Ca 2 + from load-bearing bonds. The enzyme responsible for proton pumping is the plasma membrane H+-ATPase. The activity of this enzyme in nectarine (Prunus persica (L.) Batsch var. nectarina (Ait.) Maxim., cv. Redgold) mesocarp was studied during 4 days of ripening at 20°C after harvest at commercial maturity. Fruit began to produce significant amounts of ethylene (> 1 ~tre/kg per h) from the second day. Flesh fmnness began to decline from the third day, but background skin colour did not change until the fourth day. Plasma membranes were extracted from the fruit by phase partitioning. Initial characterisation of the H+-ATPase activity showed that it was Mg2+-dependent, K+-stimulated, and vol-sensitive. The KID for MgA TP was 0.19 ± 0.02 mM. The Kj value for Ca 2 + was estimated at 100 JlM free Ca 2 +. The in vitro specific activity of the A1Pase did not alter significantly during a 4-day period after commercial harvest. There was a slight decline in ATPase activity with increasing ethylene evolution (R2 = 0.25, P < 0.05) but no significant correlation between ATPase activity and fmnness or skin colour.

Acta Horticulturae, 2016

The aim of this study was to investigate the effect of different doses of UV-C light as a posthar... more The aim of this study was to investigate the effect of different doses of UV-C light as a postharvest treatment to control the attachment and subsequent growth of Listeria monocytogenes on fresh-cut broccoli. Growth of the bacteria was studied under in vitro and in vivo conditions. UV-C treated (0, 2.6 and 5.2 kJ m-2) broccoli branchlets were inoculated with L. monocytogenes at various times (0, 6, and 24 h) after treatment and tested for bacterial growth up to 8 days. Broccoli extracts obtained through fractionation and partitioning between different solvents (nhexane, 10% methanol, n-butanol, and aqueous) were tested in vitro against the growth of L monocytogenes. Broccoli extracts from all doses of UV-C irradiation significantly reduced the growth of L. monocytogenes when inoculated 24 h post treatment while only the extract from higher UV-C dose was effective in reducing growth in samples inoculated 6 h after the treatment. The most potent extracts were aqueous and butanol which restricted the growth of L. monocytogenes in samples treated with 5.2 kJ m-2 and extracted 24 h after the treatment. Phytochemical analysis of the same samples using LC-MS confirmed that UV-C treatment induced particular chemical compounds that may restrain microbial growth. These findings confirm that UV-C treatment is effective in stimulating the synthesis of phytochemical compounds that may inhibit the growth of L. monocytogenes in fresh-cut broccoli. Therefore, this treatment could be used as a hurdle technology to reduce the risk of post-harvest contamination and to ensure microbial safety of fresh produce.

Scientia Horticulturae, 2016

The application rate, length and timing of any physical treatment influence its effectiveness. In... more The application rate, length and timing of any physical treatment influence its effectiveness. In developing a treatment for commercial application, delays prior to, and caused by the physical treatment may play an important role to find product outcomes. Previously, hypobaric treatment has been identified as a potential decay reduction treatment. The aims of this study were to investigate the impact of application speed, length and delay prior to and caused by hypobaric treatment on the subsequent efficacy to reduce decay development in strawberry. Hypobaric treatment for 6 h and repeated application of 50 kPa mitigated effectiveness. Delaying application by 8 h continued to result in reducing strawberry decay without affecting weight loss and firmness in subsequent storage. However, hypobaric treated (50 kPa for 4 h at 20 • C) strawberries were no different from non-treated fruit shifted directly to 5 • C, suggesting that application at 20 • C is inappropriate. Alternatively, hypobaric treatment (50 kPa, 4 h) at 5 • C reduced fungal decay in comparison to control fruit transferred directly to 5 • C, indicating that hypobaric treatment after cooling may be the best approach to minimize decay development. Results of this work demonstrate the potential to combine hypobaric treatment with cold storage to extend storage life of strawberries. However, for more effective application, perhaps hypobaric treatment should be tested as a hurdle technology to be used in conjunction with other physical treatments (UV-C, heat and ultrasound) and/or volatile chemical treatments.

Postharvest Biology and Technology, 2015

Acta Horticulturae, 2010

The effects of controlled atmosphere (CA) on fruit quality of a commercially important cultivar o... more The effects of controlled atmosphere (CA) on fruit quality of a commercially important cultivar of feijoa fruit, 'Unique', were studied during storage in five atmospheres containing: 0 kPa CO 2 , 2 kPa O 2 ; 3 kPa CO 2 , 2 kPa O 2 ; 0 kPa CO 2 , 5 kPa O 2 ; 3 kPa CO 2 , 5 kPa O 2 ; and air at 4°C. Fruit were transferred to 20°C after storage for 4, 6, 8 and 10 weeks for a shelf life period of 7 days. For the entire period of storage fruit weight loss was approximately 1.6% of the initial weight. When fruit were transferred to 20°C, rate of weight loss rapidly increased. From week 6 onwards fruit previously stored in CA lost less weight during shelf life than fruit stored in air. There was a decline in firmness in all fruit over the storage and shelf life period. Fruit stored in air softened faster (from about 14 N at week 4 to about 7 N at week 10) than in CA (16 N to 12 N). Fruit from all treatments developed an external skin discolouration after 6 weeks at 4°C. There was no significant difference in skin colour between CA and air stored fruit. 'Unique' fruit stored in CA ripened more slowly than fruit in air. Despite these beneficial effects of CA, CA storage treatments used here did not appear to offer a significant benefit for 'Unique' in terms of the final outturn quality. All fruit were rated as over ripe after 6 weeks of storage regardless of treatment.

Acta Horticulturae, 2013

Postharvest fungal rot contributes significantly to fresh produce losses. Conventionally, fungici... more Postharvest fungal rot contributes significantly to fresh produce losses. Conventionally, fungicides have been used to minimise fruit decay. However, increased concerns over the negative effects of fungicide application motivated a search for alternative options to extend storage life of fresh produce. While temperature control reduces the chance of fungal rot, a physical treatment at a time soon after harvest may further increase storage life. Previous studies have suggested that a postharvest hypobaric treatment is a potential non-chemical method for the control of fungal rots in some fresh produce. In this study the effect of hypobaric treatment (50 kPa.a, 4 h) on the subsequent rot development and quality of blueberries held at 20 and 0°C was assessed. The results obtained show that prestorage low pressure treatment of blueberries slightly reduced postharvest rot incidence arising from natural infections at 20°C. In addition, firmness and respiration rate of the fruit were not affected by low pressure treatment. The small reduction in rot incidence in hypobaric treated fruit has been ascribed to either direct effect of low oxygen; indirect activation of induced resistance; or removal of free water from the surface of the produce. Should hypobaric treatments be found to be effectual they could eventually facilitate the development of a new cost-effective method of physical treatment to reduce postharvest fungal decay.

Introduced to New Zealand in 1993, ulluco (Ullucus tuberosus) is still a minor crop despite the a... more Introduced to New Zealand in 1993, ulluco (Ullucus tuberosus) is still a minor crop despite the attractive colour and shape of tubers, mainly because of late tuberisation and an earthy taste due to the presence of geosmin. SPME-GC/MS analysis revealed a high degree of variability within ulluco cultivars for geosmin levels. Progeny analysis revealed that the character is heritable, allowing selection for low-geosmin. Detection of geosmin in microtubers produced under aseptic conditions confirmed the presence of a biochemical pathway for geosmin in ulluco, justifying this breeding strategy. Ulluco does not produce seeds under New Zealand conditions and has a very limited genetic base. Therefore, we developed an in vitro-based method for rapid selection of solid mutants. Axillary buds were induced to produce callus that was treated with ethylmethane sulfonate (1 and 2%) or gamma rays (10, 20, 30 and 40 Gy) or both, and plantlets were regenerated. They were subcultured several times wit...

Towards a gourmet ulluco: Biochemistry and mutagenesis Pathirana, Ranjith (1) Sansom, Catherine (... more Towards a gourmet ulluco: Biochemistry and mutagenesis Pathirana, Ranjith (1) Sansom, Catherine (2) Smallfield, Bruce (3) Perry, Nigel (4) Heyes, Julian (5) (1,5)Plant & Food Research, Private Bag 11 600, Palmerston North 4442 (2,4)Plant & Food Research, Plant Extracts Research Unit, 4th Floor, Science II Building, Cnr Castle & Union,Dunedin 9016 (3)Plant & Food Research, Canterbury Agriculture & Science Centre, Gerald St, Lincoln 7608 Attractive colour and shape of tubers make ulluco (Ullucus tuberosus) a potentially valuable gourmet vegetable. Late tuberisation and the presence of geosmin giving an earthy taste are two major problems. We have optimised SPME-GC/MS to evaluate geosmin levels in tubers allowing progeny testing of analysed tubers. Within cultivar variation was found to be high and progeny analysis revealed that the character is heritable allowing selection for low-geosmin levels. Detection of geosmin in microtubers produced under aseptic conditions confirmed the prese...

Annals of Botany, 2000

Several processes contribute to the rapid opening of Asiatic lily¯owers. Opening occurs after the... more Several processes contribute to the rapid opening of Asiatic lily¯owers. Opening occurs after the tepals stop increasing in length, and have reached maximum thickness. Up to day À0. 5 (where day 0 is time that¯owers are halfopen), the sepals entirely encase the petals, and their edges are tightly clasped in deep grooves beside the petal midribs. At day À0. 5 to À0. 3, the petal midrib reduces in width, opening the groove and allowing the tepals to pull apart (bud`cracking'). Unlocking is not complete until about day À0. 15: it is not the key event directing opening, but helps to sharpen its onset. The midribs control subsequent opening, pulling the laminae behind them. In the ®rst 3±4 h of opening (`dark phase'), the main process is an increase in the angles the midribs make where they join the pedicels. During this time, the petals and sepals are only slightly curved. Subsequently through to day 0. 5 (the`light phase'), an increasingly marked curvature of the midribs pulls the tepals further apart and causes them to progressively re¯ex. By day 1 the¯owers are mature and the laminae are no longer being pulled by the midribs. In studies of isolated tissue segments, we found that in the later stages of opening there is greater cell expansion in the epidermis of the inner surfaces, contributing to the recurving. Petal expansion is accompanied by cell separation and osmotic changes, and inhibitors of starch hydrolysis inhibit expansion of petal segments. Of the various processes operating during lily opening, we believe that the most in¯uential is the change in angle between midribs and pedicel, suggesting a pulvinus-like mechanism.

Annals of Botany, 2000

In commerce, Asiatic lilies are picked in bud, each stem holding several buds. We found¯ower open... more In commerce, Asiatic lilies are picked in bud, each stem holding several buds. We found¯ower opening was rapid, taking less than 4 h both on the stem and for excised buds. Opening was also strongly synchronous. For a 12 h daynight cycle, opening began late in the dark period, reaching a mid-point after 11 h of darkness. This was equally true of buds that were excised when nearly ready to open, and those with 3±4 d of development to complete. Reversing day and night reversed the time of opening, and red light was as eective as white light in providing`day' conditions. A 15 min light break during the night did not aect the opening. Lengthening the night (8, 12, 16 h) and shortening the day delayed opening from 9, to 11, to 13 h after the start of darkness, respectively. In continuous light and continuous dark, synchronicity was lost. If opening¯owers were held in extended darkness, two phases of opening could be discriminated. In a`dark phase', petals opened to approx. 408, and anthers remained intact. When such¯owers were returned to light, there was a`light phase', where petals opened further, became more pigmented and began to recurve, and the anthers dehisced, these events taking only 2±3 h. The net result was that¯owers became fully open and anthers dehisced approx. 2 h after dawn, regardless of daylength.

Postharvest Biology and Technology, 2006

The effects of 1-methylcyclopropene (1-MCP), an ethylene inhibitor, on endogenous ethylene produc... more The effects of 1-methylcyclopropene (1-MCP), an ethylene inhibitor, on endogenous ethylene production and chlorophyll degradation in the West Indian lime (Citrus aurantifolia, Swingle cv. 'Paan') were examined under ambient conditions (24-31 • C and 73-81% RH). Fruit treated with 250 or 500 nl l −1 1-MCP effectively retarded yellowing for 21 days at ambient storage. Application of 1000 nl l −1 1-MCP accelerated yellowing within 9 days, while 750 nl l −1 1-MCP treated fruit completely turned yellow at 15 days. Chlorophyllase and chlorophyll degrading peroxidase activities in flavedo tissue of lime peel were delayed in 1-MCP treated fruit at concentrations of 250 and 500 nl l −1. Ethylene production rate of 1000 nl l −1 1-MCP treated fruit was 1.6 times higher than that of untreated fruit. Nevertheless, 1-MCP at low concentrations (250 or 500 nl l −1) effectively suppressed endogenous ethylene production. Ascorbic acid content was reduced in fruit treated with 1000 nl l −1 1-MCP but not in fruit treated with 250, 500 or 750 nl l −1. Before commercial treatment of limes with 1-MCP becomes possible, the appropriate concentration and treatment temperature, fruit maturity stage and storage temperature must be determined.

Annual Plant Reviews online

2019 IEEE International Instrumentation and Measurement Technology Conference (I2MTC)

This paper presents a novel technique to measure skin topography of kiwifruit. Fringe projection ... more This paper presents a novel technique to measure skin topography of kiwifruit. Fringe projection has been identified as a rapid, non-destructive way to extract topographical data from fruit skins. In this paper, a detailed methodology of using this technology is outlined. The captured raw data require the filtering process to separate the low frequency component from the high frequency component. A wide range of surface roughness parameters can be extracted from the accompanying proprietary software after filtering. 3D coordinates arranged as a rectangular matrix of height values can be extracted for further image analysis. An experiment on skin topography of kiwifruit has concluded that the technique is able to to quantify the skin difference from different growing environments.

NSNZ 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

New Zealand Journal of Crop and Horticultural Science, 2022

Scientia Horticulturae, 2022

New Zealand Journal of Crop and Horticultural Science, 2022

ABSTRACTTuber quality problems such as skin tears (skinning), rots, browning, shrivelling and wei... more ABSTRACTTuber quality problems such as skin tears (skinning), rots, browning, shrivelling and weight loss in New Zealand-grown export potatoes have caused significant postharvest losses and insurance quality claims from overseas distributors. These quality issues could be attributed to poor management of curing and subsequent storage conditions. This study investigated the effects of various curing and storage conditions (i.e. duration, temperature and relative humidity (RH)) on tuber quality of two potato cultivars, ‘Moonlight’ and ‘Nadine’, that are exported to Fiji. Results have shown that high curing RH (93\%) led to significantly lower skin browning, shrivelling and weight loss in both cultivars, and significantly lower tuber rot in ‘Nadine’ than low curing RH (62\%). Shorter curing duration (7 days) yielded significantly lower shrivelling in ‘Moonlight’, and significantly lower tuber rot in ‘Nadine’, than longer curing duration (14 days) or control (0 day). Percent weight loss was significantly lower in cured potatoes than in control for both cultivars. Curing temperatures (16 or 26°C) and storage RH (65 or 90\%) did not significantly affect the tuber qualities assessed. Therefore, 7 d curing at &gt;90\% RH and at least 15°C is recommended for minimising quality problems occurring during transport of these potato cultivars to distant markets.

Nutrients, 2021

Cancer is one of the leading causes of death globally. Epidemiological studies have strongly link... more Cancer is one of the leading causes of death globally. Epidemiological studies have strongly linked a diet high in fruits to a lower incidence of cancer. Furthermore, extensive research shows that secondary plant metabolites known as phytochemicals, which are commonly found in fruits, have onco-preventive and chemo-protective effects. Apple is a commonly consumed fruit worldwide that is available all year round and is a rich source of phytochemicals. In this review, we summarize the association of apple consumption with cancer incidence based on findings from epidemiological and cohort studies. We further provide a comprehensive review of the main phytochemical patterns observed in apples and their bioavailability after consumption. Finally, we report on the latest findings from in vitro and in vivo studies highlighting some of the key molecular mechanisms targeted by apple phytochemicals in relation to inhibiting multiple ‘hallmarks of cancer’ that are important in the progression ...

Postharvest Physiological Disorders in Fruits and Vegetables, 2019

AIP Conference Proceedings, 2019

Fermentation and drying are two important postharvest processing stages for Theobroma cacao beans... more Fermentation and drying are two important postharvest processing stages for Theobroma cacao beans. In the Fiji Islands, tropical weather conditions favour fermentation but the high relative humidity impedes drying. Slow or intermittent drying leads to product loss from mould growth and spoilage, which is costly for the cocoa industry. Conversely, direct solar drying can lead to unacceptably high temperatures (over 60 °C) and quality loss. Relative humidity can be controlled by applying low cost desiccant technology such as silica gel to dehumidify process air. The effect of dehumidified air on drying fermented T. cacao beans was evaluated at different drying temperatures of 56 °C and 46 °C. A rapid drying rate was achieved for fermented T. cacao beans dried at 56 °C under 10% relative humidity. Drying was slower at 46 °C under 18% relative humidity. Cocoa beans equilibrated to a moisture content <7% in 12 h and 34 h drying time respectively. Quality analyses are now under way to establish which of these drying profiles is preferable as a target for desiccant-assisted indirect solar drying.

New Zealand Journal of Crop and Horticultural Science, 1992

Softening during fruit ripening may be initiated by an increase in proton pumping across the plas... more Softening during fruit ripening may be initiated by an increase in proton pumping across the plasma membrane. This would lower the cell wall pH and loosen acid-labile bonds, as well as displacing Ca 2 + from load-bearing bonds. The enzyme responsible for proton pumping is the plasma membrane H+-ATPase. The activity of this enzyme in nectarine (Prunus persica (L.) Batsch var. nectarina (Ait.) Maxim., cv. Redgold) mesocarp was studied during 4 days of ripening at 20°C after harvest at commercial maturity. Fruit began to produce significant amounts of ethylene (> 1 ~tre/kg per h) from the second day. Flesh fmnness began to decline from the third day, but background skin colour did not change until the fourth day. Plasma membranes were extracted from the fruit by phase partitioning. Initial characterisation of the H+-ATPase activity showed that it was Mg2+-dependent, K+-stimulated, and vol-sensitive. The KID for MgA TP was 0.19 ± 0.02 mM. The Kj value for Ca 2 + was estimated at 100 JlM free Ca 2 +. The in vitro specific activity of the A1Pase did not alter significantly during a 4-day period after commercial harvest. There was a slight decline in ATPase activity with increasing ethylene evolution (R2 = 0.25, P < 0.05) but no significant correlation between ATPase activity and fmnness or skin colour.

Acta Horticulturae, 2016

The aim of this study was to investigate the effect of different doses of UV-C light as a posthar... more The aim of this study was to investigate the effect of different doses of UV-C light as a postharvest treatment to control the attachment and subsequent growth of Listeria monocytogenes on fresh-cut broccoli. Growth of the bacteria was studied under in vitro and in vivo conditions. UV-C treated (0, 2.6 and 5.2 kJ m-2) broccoli branchlets were inoculated with L. monocytogenes at various times (0, 6, and 24 h) after treatment and tested for bacterial growth up to 8 days. Broccoli extracts obtained through fractionation and partitioning between different solvents (nhexane, 10% methanol, n-butanol, and aqueous) were tested in vitro against the growth of L monocytogenes. Broccoli extracts from all doses of UV-C irradiation significantly reduced the growth of L. monocytogenes when inoculated 24 h post treatment while only the extract from higher UV-C dose was effective in reducing growth in samples inoculated 6 h after the treatment. The most potent extracts were aqueous and butanol which restricted the growth of L. monocytogenes in samples treated with 5.2 kJ m-2 and extracted 24 h after the treatment. Phytochemical analysis of the same samples using LC-MS confirmed that UV-C treatment induced particular chemical compounds that may restrain microbial growth. These findings confirm that UV-C treatment is effective in stimulating the synthesis of phytochemical compounds that may inhibit the growth of L. monocytogenes in fresh-cut broccoli. Therefore, this treatment could be used as a hurdle technology to reduce the risk of post-harvest contamination and to ensure microbial safety of fresh produce.

Scientia Horticulturae, 2016

The application rate, length and timing of any physical treatment influence its effectiveness. In... more The application rate, length and timing of any physical treatment influence its effectiveness. In developing a treatment for commercial application, delays prior to, and caused by the physical treatment may play an important role to find product outcomes. Previously, hypobaric treatment has been identified as a potential decay reduction treatment. The aims of this study were to investigate the impact of application speed, length and delay prior to and caused by hypobaric treatment on the subsequent efficacy to reduce decay development in strawberry. Hypobaric treatment for 6 h and repeated application of 50 kPa mitigated effectiveness. Delaying application by 8 h continued to result in reducing strawberry decay without affecting weight loss and firmness in subsequent storage. However, hypobaric treated (50 kPa for 4 h at 20 • C) strawberries were no different from non-treated fruit shifted directly to 5 • C, suggesting that application at 20 • C is inappropriate. Alternatively, hypobaric treatment (50 kPa, 4 h) at 5 • C reduced fungal decay in comparison to control fruit transferred directly to 5 • C, indicating that hypobaric treatment after cooling may be the best approach to minimize decay development. Results of this work demonstrate the potential to combine hypobaric treatment with cold storage to extend storage life of strawberries. However, for more effective application, perhaps hypobaric treatment should be tested as a hurdle technology to be used in conjunction with other physical treatments (UV-C, heat and ultrasound) and/or volatile chemical treatments.

Postharvest Biology and Technology, 2015

Acta Horticulturae, 2010

The effects of controlled atmosphere (CA) on fruit quality of a commercially important cultivar o... more The effects of controlled atmosphere (CA) on fruit quality of a commercially important cultivar of feijoa fruit, 'Unique', were studied during storage in five atmospheres containing: 0 kPa CO 2 , 2 kPa O 2 ; 3 kPa CO 2 , 2 kPa O 2 ; 0 kPa CO 2 , 5 kPa O 2 ; 3 kPa CO 2 , 5 kPa O 2 ; and air at 4°C. Fruit were transferred to 20°C after storage for 4, 6, 8 and 10 weeks for a shelf life period of 7 days. For the entire period of storage fruit weight loss was approximately 1.6% of the initial weight. When fruit were transferred to 20°C, rate of weight loss rapidly increased. From week 6 onwards fruit previously stored in CA lost less weight during shelf life than fruit stored in air. There was a decline in firmness in all fruit over the storage and shelf life period. Fruit stored in air softened faster (from about 14 N at week 4 to about 7 N at week 10) than in CA (16 N to 12 N). Fruit from all treatments developed an external skin discolouration after 6 weeks at 4°C. There was no significant difference in skin colour between CA and air stored fruit. 'Unique' fruit stored in CA ripened more slowly than fruit in air. Despite these beneficial effects of CA, CA storage treatments used here did not appear to offer a significant benefit for 'Unique' in terms of the final outturn quality. All fruit were rated as over ripe after 6 weeks of storage regardless of treatment.

Acta Horticulturae, 2013

Postharvest fungal rot contributes significantly to fresh produce losses. Conventionally, fungici... more Postharvest fungal rot contributes significantly to fresh produce losses. Conventionally, fungicides have been used to minimise fruit decay. However, increased concerns over the negative effects of fungicide application motivated a search for alternative options to extend storage life of fresh produce. While temperature control reduces the chance of fungal rot, a physical treatment at a time soon after harvest may further increase storage life. Previous studies have suggested that a postharvest hypobaric treatment is a potential non-chemical method for the control of fungal rots in some fresh produce. In this study the effect of hypobaric treatment (50 kPa.a, 4 h) on the subsequent rot development and quality of blueberries held at 20 and 0°C was assessed. The results obtained show that prestorage low pressure treatment of blueberries slightly reduced postharvest rot incidence arising from natural infections at 20°C. In addition, firmness and respiration rate of the fruit were not affected by low pressure treatment. The small reduction in rot incidence in hypobaric treated fruit has been ascribed to either direct effect of low oxygen; indirect activation of induced resistance; or removal of free water from the surface of the produce. Should hypobaric treatments be found to be effectual they could eventually facilitate the development of a new cost-effective method of physical treatment to reduce postharvest fungal decay.

Introduced to New Zealand in 1993, ulluco (Ullucus tuberosus) is still a minor crop despite the a... more Introduced to New Zealand in 1993, ulluco (Ullucus tuberosus) is still a minor crop despite the attractive colour and shape of tubers, mainly because of late tuberisation and an earthy taste due to the presence of geosmin. SPME-GC/MS analysis revealed a high degree of variability within ulluco cultivars for geosmin levels. Progeny analysis revealed that the character is heritable, allowing selection for low-geosmin. Detection of geosmin in microtubers produced under aseptic conditions confirmed the presence of a biochemical pathway for geosmin in ulluco, justifying this breeding strategy. Ulluco does not produce seeds under New Zealand conditions and has a very limited genetic base. Therefore, we developed an in vitro-based method for rapid selection of solid mutants. Axillary buds were induced to produce callus that was treated with ethylmethane sulfonate (1 and 2%) or gamma rays (10, 20, 30 and 40 Gy) or both, and plantlets were regenerated. They were subcultured several times wit...

Towards a gourmet ulluco: Biochemistry and mutagenesis Pathirana, Ranjith (1) Sansom, Catherine (... more Towards a gourmet ulluco: Biochemistry and mutagenesis Pathirana, Ranjith (1) Sansom, Catherine (2) Smallfield, Bruce (3) Perry, Nigel (4) Heyes, Julian (5) (1,5)Plant & Food Research, Private Bag 11 600, Palmerston North 4442 (2,4)Plant & Food Research, Plant Extracts Research Unit, 4th Floor, Science II Building, Cnr Castle & Union,Dunedin 9016 (3)Plant & Food Research, Canterbury Agriculture & Science Centre, Gerald St, Lincoln 7608 Attractive colour and shape of tubers make ulluco (Ullucus tuberosus) a potentially valuable gourmet vegetable. Late tuberisation and the presence of geosmin giving an earthy taste are two major problems. We have optimised SPME-GC/MS to evaluate geosmin levels in tubers allowing progeny testing of analysed tubers. Within cultivar variation was found to be high and progeny analysis revealed that the character is heritable allowing selection for low-geosmin levels. Detection of geosmin in microtubers produced under aseptic conditions confirmed the prese...

Annals of Botany, 2000

Several processes contribute to the rapid opening of Asiatic lily¯owers. Opening occurs after the... more Several processes contribute to the rapid opening of Asiatic lily¯owers. Opening occurs after the tepals stop increasing in length, and have reached maximum thickness. Up to day À0. 5 (where day 0 is time that¯owers are halfopen), the sepals entirely encase the petals, and their edges are tightly clasped in deep grooves beside the petal midribs. At day À0. 5 to À0. 3, the petal midrib reduces in width, opening the groove and allowing the tepals to pull apart (bud`cracking'). Unlocking is not complete until about day À0. 15: it is not the key event directing opening, but helps to sharpen its onset. The midribs control subsequent opening, pulling the laminae behind them. In the ®rst 3±4 h of opening (`dark phase'), the main process is an increase in the angles the midribs make where they join the pedicels. During this time, the petals and sepals are only slightly curved. Subsequently through to day 0. 5 (the`light phase'), an increasingly marked curvature of the midribs pulls the tepals further apart and causes them to progressively re¯ex. By day 1 the¯owers are mature and the laminae are no longer being pulled by the midribs. In studies of isolated tissue segments, we found that in the later stages of opening there is greater cell expansion in the epidermis of the inner surfaces, contributing to the recurving. Petal expansion is accompanied by cell separation and osmotic changes, and inhibitors of starch hydrolysis inhibit expansion of petal segments. Of the various processes operating during lily opening, we believe that the most in¯uential is the change in angle between midribs and pedicel, suggesting a pulvinus-like mechanism.

Annals of Botany, 2000

In commerce, Asiatic lilies are picked in bud, each stem holding several buds. We found¯ower open... more In commerce, Asiatic lilies are picked in bud, each stem holding several buds. We found¯ower opening was rapid, taking less than 4 h both on the stem and for excised buds. Opening was also strongly synchronous. For a 12 h daynight cycle, opening began late in the dark period, reaching a mid-point after 11 h of darkness. This was equally true of buds that were excised when nearly ready to open, and those with 3±4 d of development to complete. Reversing day and night reversed the time of opening, and red light was as eective as white light in providing`day' conditions. A 15 min light break during the night did not aect the opening. Lengthening the night (8, 12, 16 h) and shortening the day delayed opening from 9, to 11, to 13 h after the start of darkness, respectively. In continuous light and continuous dark, synchronicity was lost. If opening¯owers were held in extended darkness, two phases of opening could be discriminated. In a`dark phase', petals opened to approx. 408, and anthers remained intact. When such¯owers were returned to light, there was a`light phase', where petals opened further, became more pigmented and began to recurve, and the anthers dehisced, these events taking only 2±3 h. The net result was that¯owers became fully open and anthers dehisced approx. 2 h after dawn, regardless of daylength.

Postharvest Biology and Technology, 2006

The effects of 1-methylcyclopropene (1-MCP), an ethylene inhibitor, on endogenous ethylene produc... more The effects of 1-methylcyclopropene (1-MCP), an ethylene inhibitor, on endogenous ethylene production and chlorophyll degradation in the West Indian lime (Citrus aurantifolia, Swingle cv. 'Paan') were examined under ambient conditions (24-31 • C and 73-81% RH). Fruit treated with 250 or 500 nl l −1 1-MCP effectively retarded yellowing for 21 days at ambient storage. Application of 1000 nl l −1 1-MCP accelerated yellowing within 9 days, while 750 nl l −1 1-MCP treated fruit completely turned yellow at 15 days. Chlorophyllase and chlorophyll degrading peroxidase activities in flavedo tissue of lime peel were delayed in 1-MCP treated fruit at concentrations of 250 and 500 nl l −1. Ethylene production rate of 1000 nl l −1 1-MCP treated fruit was 1.6 times higher than that of untreated fruit. Nevertheless, 1-MCP at low concentrations (250 or 500 nl l −1) effectively suppressed endogenous ethylene production. Ascorbic acid content was reduced in fruit treated with 1000 nl l −1 1-MCP but not in fruit treated with 250, 500 or 750 nl l −1. Before commercial treatment of limes with 1-MCP becomes possible, the appropriate concentration and treatment temperature, fruit maturity stage and storage temperature must be determined.