Ultralow Oxygen Treatment Research Articles

Ultra-Low Oxygen and Preconditioning Storage Regulate Ethylene Synthesis to Prevent Corky Disorders in 'Fuji' Apple.

Corky disorders in apples represent a significant problem for long-term storage where controlled atmosphere (CA) is mainly used. Ultra-low oxygen (ULO) is an alternative to CA, which consists of low partial pressure of O2 to maintain a low metabolism in the apple fruit, achieving an effective decrease in the ethylene production and physiological disorders. The aim of this research was to study the effectiveness of a short hypoxia period on the development of cork physiological disorders during the storage of apple. ‘Fuji’ apples were prestored under ULO (0.5 kPa O2) for two periods of time (15 and 30 days) and at two temperatures (0 or 5°C). Corky physiological disorders increased at 5°C prestorage temperature; however, ULO treatments for 15 or 30 days at 0 or 5°C achieved a significant reduction in corky disorders near to 1%, compared with control treatments. In addition, a considerable reduction in ethylene production for up to 30 days was observed in ULO-treated fruit at 0 and 5°C. ULO for 30 days at 0 and 5°C increased the internal production of ethanol and acetaldehyde, causing a lower sensory quality due to the presence of fermentative flavors in fruit stored at 5°C. ULO of 15 days of conditioning decreased the relative expression of ethylene biosynthesis genes MdACS1 and MdACO1, resulting in lower ethylene production.

Prestorage Temperature and Ultra-low Oxygen Treatments Affect Incidence of Physiological Disorders in Organic ‘Granny Smith’ Apples

The physiological disorders superficial scald, bitter pit, and lenticel blotch pit severely compromise the commercial value of ‘Granny Smith’ apples. A number of chemical treatments are available to alleviate these disorders but they are unacceptable in the expanding organic market. The objective of this research was to study the effectiveness of prestorage treatments—delayed cooling and elevated temperature under ultra-low oxygen (ULO) atmospheres—as organic-friendly strategies to control these disorders. ‘Granny Smith’ apples were exposed to four different treatments: 1) conditioning temperature treatments (CTemp): 10 days at 3 °C or 30 days at 3 °C or 10 days at 20 °C, in air; 2) the same conditioning temperature treatments combined with an ultra-low oxygen (ULO) conditioning treatment of 0.2–0.5 kPa O2 and <0.5 kPa CO2; 3) 1-methylcyclopropene (1-MCP) treatment as a commercial control; and 4) untreated control fruit. After the prestorage treatment, fruit were stored for 90 or 150 days at 0 °C, and then held poststorage for 8 days at 20 °C before quality analysis. A combination treatment of temperature conditioning and ULO for 30 days at 3 °C achieved the best control of superficial scald, bitter pit, and lenticel blotch pit. The use of ULO with CTemp for 10 days at 20 °C offered the same control but induced high concentrations of ethanol and acetaldehyde that affected the organoleptic acceptability of the fruit and reduced its commercial value. The use of 1-MCP offered 100% control of superficial scald but bitter pit and lenticel blotch pit disorder incidences were similar or higher than in the control fruit. All ULO conditioning treatments resulted in high ethanol and acetaldehyde concentrations during the first 90 days of storage, but fruit exposed to ULO conditioning treatment for 30 days at 3 °C showed similar organoleptic acceptability to control fruit after 150 days. Therefore, ULO conditioning is a potentially useful treatment for the organic apple industry.

Effects of Ultralow Oxygen and Vacuum Treatments on Bed Bug (Heteroptera: Cimicidae) Survival.

Control of bed bugs is problematic, balancing among efficacy, safety, and cost. In this study, ultralow oxygen (ULO) and vacuum treatments were tested on bed bugs to develop a safer, effective, and environmentally friendly solution to kill bed bugs on infested items. ULO treatments were established by flushing sealed enclosures with nitrogen. All life stages of bed bugs were found to be susceptible to ULO and vacuum treatments, and efficacy of the treatments increased with reduced oxygen levels, increased treatment time, and temperature. In the ULO treatments, 100% mortality of bed bug nymphs and adults and >98% mortality of bed bug eggs were achieved in the 8-h treatment under 0.1% O 2 atmosphere at 30°C. Different levels of vacuum that yielded different oxygen levels were tested on all life stages of bed bugs. The susceptibility of different stages to vacuum treatments increased from nymphs to adults to eggs. Complete control of all life stages was achieved in 12 h under -982 mbar (-29.0 inHg) vacuum at 30°C. This study demonstrated that bed bugs were very susceptible to low oxygen stresses and ULO and vacuum treatments have potential to be used as effective and safe treatments to decontaminate bed bug-infested removable objects.

Controlled atmosphere treatment for control of grape mealybug, Pseudococcus maritimus (Ehrhorn) (Hemiptera: Pseudococcidae), on harvested table grapes

Controlled atmosphere (CA) treatments with ultralow oxygen (ULO) alone and in combinations with 50% carbon dioxide were studied to control grape mealybug, Pseudococcus maritimus (Ehrhorn) on harvested table grapes. Two ultralow oxygen levels, 30 and <0.01μLL−1, were tested in both ULO and ULO+50% CO2 treatments. The ULO treatments with the lower oxygen level were more effective than the ULO treatments at the higher oxygen level. The ULO+50% CO2 treatments were more effective than the ULO treatments. Grape mealybug eggs were significantly more tolerant of ULO and ULO+CO2 treatments than nymphs and adults. A 14day ULO treatment with 30μLL−1 O2 at 2°C did not achieve 100% mortalities of any life stage. In the presence of 50% CO2, the 14d treatment achieved complete mortality of all life stages of the grape mealybug. A 3d ULO treatment with <0.01μLL−1 O2 at 2°C resulted in 93.3% mortality of nymphs and adults. The 3d ULO treatment in combination with 50% CO2 treatments, however, achieved complete control of grape mealybug nymphs and adults and caused 70.5% relative egg mortality. Complete egg mortality was achieved in a 10d ULO+50% CO2 treatment with <0.01μLL−1 O2 at 2°C. Both the 14d CA treatment with 30μLL−1 O2 and 50% CO2 and the 10d CA treatment with <0.01μLL−1 O2 and 50% CO2 were tested on table grapes and grape quality was evaluated after two weeks of post-treatment storage. The CA treatments did not have a significant negative impact on grape quality and were safe for table grapes. The study indicated that CA treatments have potential to be developed for postharvest control of grape mealybug on harvested table grapes.

Ultralow oxygen treatment for control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on harvested table grapes

Exported organic table grapes from the U.S. are currently fumigated with methyl bromide to control quarantined pests such as western flower thrips, Frankliniella occidentalis (Pergande). An alternative treatment which is compatible with organic products is needed. In this study, controlled atmosphere with ultralow oxygen (ULO) treatment was studied to control thrips on harvested table grapes. ULO treatments with <0.01ppm oxygen at 3.3°C for 1, 2, and 3days were tested for thrips control. The 3-day ULO treatment achieved complete control of thrips. The treatment was also applied to Thompson seedless and Flame seedless grape varieties and grape quality was evaluated two weeks after the treatment. The ULO treatment had no negative impact on the visual quality of grapes. There were no significant differences in overall grape quality or premium quality berries between the ULO treatment and the control. The results indicated that the ULO treatment was effective and safe to control western flower thrips on table grapes and had a potential for commercial use.

Influence of preharvest calcium applications, fruit injury, and storage atmospheres on postharvest brown rot of apple

In a three year study, the effect of preharvest calcium applications on postharvest losses of apple fruit (cultivar ‘Idared’) caused by Monilinia fructigena was evaluated in fruit under air storage, controlled atmosphere (CA), and ultra low oxygen (ULO) conditions. Injured and noninjured fruit were used and storage was at 1°C for all three storage conditions. In addition, temporal dynamics of postharvest brown rot development were assessed monthly over four months storage and the spread of brown rot infection amongst fruit was assessed at the final assessment date. For all years, disease development, final brown rot incidence and the area under curves of disease progress were lower amongst calcium-treated than in the nontreated controls (mean values of 3.6 and 11.1%, respectively). CA and ULO treatments reduced rot incidence (mean values of 12.4, 6.3, and 0.7%, for air, CA and ULO fruit respectively). In addition, with regard to injury–inoculation combinations, final brown rot incidence increased in the order noninjured–noninoculated, noninjured–inoculated, injured–noninoculated and injured–inoculated treatments (mean values of 3.6, 5.0, 7.3, and 11.4%, respectively). The number of infected fruit was generally higher in the first layer of neighbouring fruit in storage boxes than in the second one. Calcium treatment significantly reduced the number of infected fruit both in the first and second layers compared to the controls (mean values of 45.5 and 75, respectively). CA and ULO treatments also reduced the number of infected fruit both in the first and second layers of neighbouring fruit (mean values of 94, 69.5, and 10.5, for air, CA and ULO respectively). With regard to injury treatments, the number of infected fruit increased in both the first and second layers of neighbouring fruit in the order of noninjured–inoculated and injured–inoculated treatments (mean values of 51.5 and 75.5, respectively). This study suggests that integration of preharvest calcium applications and CA storage, along with minimization of fruit injury/infection, may reduce brown rot incidence during long term storage.

Semi-commercial ultralow oxygen treatment for control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on harvested iceberg lettuce

Pallet-scale ultralow oxygen (ULO) treatment was applied to iceberg lettuce after various lengths of postharvest storage to determine the effects of pre-treatment storage on lettuce tolerance to ULO treatment for control of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Lettuce from seven cultivars was vacuum cooled and stored at 2 °C after harvest for 0, 2, 3, and 5 d before being subjected to 2-d ULO treatment with 0.003% oxygen at 10 °C ambient temperature. Complete control of thrips was achieved in all three tests. Temperature of lettuce increased from about 5 °C at the start of ULO treatment to 9.6 °C at the end of the treatment. Fresh vacuum-cooled lettuce from three of seven cultivars sustained injury to heartleaves by the ULO treatment. Lettuce that had been stored at the low temperature for 2, 3, or 5 d before the ULO treatment tolerated the ULO treatment and there was no significant quality reduction compared with untreated controls. Heavier heads were significantly more susceptible to heartleaf injury than lighter heads. This study demonstrated that 2-d postharvest refrigerated storage followed by 2-d ULO treatment was effective in controlling western flower thrips with minimal adverse effects on lettuce quality. The ULO treatment protocols developed in this study also have potential to be scaled-up for commercial ULO treatment applications.

Recent advances in development of ultralow oxygen treatment for postharvest pest control on perishable commodities

Purpose of review: This review summarises and discusses recent research progress in controlled atmosphere (CA) treatment with ultralow oxygen (ULO) for postharvest pest control on perishable commodities. Findings: In the last 10 years few studies have been conducted on ULO treatment for postharvest pest control. However, significant progress has been made and several ULO treatments were developed for postharvest pest control on different types of perishable prod� ucts. Complete control of green peach aphid, sweetpotato whitefly, twopotted spider mite and western flower thrips was achieved with 18 h fumigation using >99% nitrogen without injury to begonia seedlings. Lettuce aphid, western flower thrips and black widow spi� ders were successfully controlled on head lettuce, broccoli and table grapes, respectively, without negative impact on product quality. Vine mealybug was successfully controlled without reducing the vitality of grape benchgrafts. The tolerance of lettuce to ULO treat� ment was increased through postharvest storage to improve the safety of ULO treatment. ULO treatment is promising for controlling selected pests on selected fresh commodities, especially on those that are evaluated for their vitality rather than appearance. Directions for future research: More research efforts should be directed towards identifying suitable pests and fresh commodities for ULO treatment. Emphasis should also be given to pest control on products such as rootstocks, bulbs and tubers, which are evaluated by vitality rather than appearance. Research should also be directed at enhancing the tolerance of commodities to CA treatment in order to make ULO and other CA treatments safer to product quality. Large scale studies and collaboration with industry are also vital for in� dustrial adaptation of ULO treatment.

Ultralow Oxygen Treatment for Control of Latrodectus hesperus (Araneae: Theridiidae) on Harvested Table Grapes

The spider Latrodectus hesperus Chamberlin & Ivie (Araneae: Theridiidae) was subjected to low and ultralow oxygen (ULO) treatments at different temperatures. Complete control of the spiders was achieved in 24-h ULO treatments with 0.5% O2 or lower at 1°C and in a 24-h low oxygen (2%) treatment at 15°C. Oxygen level and temperature greatly affected spider mortality. At 1°C, as oxygen level was decreased from 2 to 0.5%, spider mortality increased from 0 to 100%. At 2% O2, as temperature was increased from 1 to 15°C, spider mortality increased from 0 to 100%. Grape clusters from two table grape (Vitis spp.) cultivars, ‘Thompson Seedless’ and ‘Flame Seedless’, were subjected to the 24-h ULO treatment with 0.5% O2 at 1°C. The ULO treatment had no negative effects on grape quality. Because of the relatively short treatment time, effectiveness at low storage temperature and the easily attained oxygen level, we conclude that the ULO treatment have good potential to be implemented commercially for control of black widow spiders on harvested table grapes.

Ultralow Oxygen Treatment for Control of &lt;I&gt;Latrodectus hesperus&lt;/I&gt; (Araneae: Theridiidae) on Harvested Table Grapes

The spider Latrodectus hesperus Chamberlin & Ivie (Araneae: Theridiidae) was subjected to low and ultralow oxygen (ULO) treatments at different temperatures. Complete control of the spiders was achieved in 24-h ULO treatments with 0.5% O2 or lower at 1 degrees C and in a 24-h low oxygen (2%) treatment at 15 degrees C. Oxygen level and temperature greatly affected spider mortality. At 1 degrees C, as oxygen level was decreased from 2 to 0.5%, spider mortality increased from 0 to 100%. At 2% O2, as temperature was increased from 1 to 15 degrees C, spider mortality increased from 0 to 100%. Grape clusters from two table grape (Vitis spp.) cultivars, 'Thompson Seedless' and 'Flame Seedless', were subjected to the 24-h ULO treatment with 0.5% O2 at 1 degrees C. The ULO treatment had no negative effects on grape quality. Because of the relatively short treatment time, effectiveness at low storage temperature and the easily attained oxygen level, we conclude that the ULO treatment have good potential to be implemented commercially for control of black widow spiders on harvested table grapes.

Ultralow oxygen treatment for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on iceberg lettuce : I. Effects of temperature, time, and oxygen level on insect mortality and lettuce quality

Ultralow oxygen (ULO) treatments with different oxygen levels, treatment times, and temperatures were studied to determine effects on western flower thrips mortality and postharvest quality of iceberg lettuce. Thrips mortality increased with reduced oxygen level and increased treatment time and temperature. At 0.003% oxygen, over 99.6% mortality rates of thrips were achieved in three ULO treatments of 2, 3, and 4 d at 10, 5, and 1 °C, respectively. No treatments caused injury to lettuce surface leaves and there was no reduction in visual quality for treated lettuce. However, about 9–33% of lettuce heads sustained injury to heartleaves. The 2 d ULO treatment with 0.003% oxygen had the lowest injury rate to heartleaves and the injury increased with increased treatment duration. The amount of injured leaves was small (<2 g per head). There were also some variations among the lettuce cultivars in susceptibility to heartleaf injury by ULO treatments. Four out of eight cultivars tested tolerated the 2 d ULO treatment at 10 °C without any injury. Therefore, ULO treatment has potential to be developed as an alternative postharvest treatment for western flower thrips on iceberg lettuce.

Ultralow oxygen treatment for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on iceberg lettuce : II. Effects of pre-treatment storage on lettuce quality

Iceberg lettuce stored under normal atmosphere and controlled atmosphere (CA) with about 3% oxygen at low temperature for 1 week was compared with fresh lettuce for their response to 2 d ultralow oxygen (ULO) treatment with 0.003% oxygen at 10 °C for control of western flower thrips. Lettuce which had been stored for 1 week under normal or CA tolerated ULO treatment while over 30% of fresh lettuce sustained minor injury to heartleaves. Therefore, pre-treatment storage at low temperature enhanced tolerance of lettuce to the subsequent insecticidal ULO treatment. A sequential combination of CA storage and ULO treatment was demonstrated to be effective against western flower thrips and lettuce aphid and safe to all seven lettuce cultivars tested. The study indicated that ULO treatment can be made safer to lettuce through pre-treatment storage to increase lettuce tolerance.

Ultralow Oxygen Treatment for Postharvest Control of Western Flower Thrips on Broccoli

Laboratory studies were conducted to develop ultralow oxygen (ULO) treatment for controlling western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), on broccoli at a low temperature of 1°C. Complete control was achieved in 5 d at 0.003% oxygen. Oxygen level affected efficacy of ULO treatment. At a higher oxygen level of 0.03%, 6-d treatment killed ≈85% of thrips, and 10-d treatment killed all thrips. The 5-d ULO treatment with 0.003% oxygen was successfully tested on iced commercial broccoli of several cultivars without any noticeable negative effects on shelf-life and postharvest quality. The ULO treatment provided a safe and effective alternative to methyl bromide fumigation for postharvest control of western flower thrips on exported broccoli for industrial development.

Ultralow Oxygen Treatment for Postharvest Control of Western Flower Thrips on Broccoli

Laboratory studies were conducted to develop ultralow oxygen (ULO) treatment for controlling western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), on broccoli at a low temperature of 1 degree C. Complete control was achieved in 5 d at 0.003% oxygen. Oxygen level affected efficacy of ULO treatment. At a higher oxygen level of 0.03%, 6-d treatment killed -85% of thrips, and 10-d treatment killed all thrips. The 5-d ULO treatment with 0.003% oxygen was successfully tested on iced commercial broccoli of several cultivars without any noticeable negative effects on shelf-life and postharvest quality. The ULO treatment provided a safe and effective alternative to methyl bromide fumigation for postharvest control of western flower thrips on exported broccoli for industrial development.

Ultralow oxygen treatment for postharvest control of Nasonovia ribisnigri (Homoptera: Aphididae) on iceberg lettuce.

The aphid Nasonovia ribisnigri (Mosley) is a common pest of lettuce in the United States. It hinders export of U.S. lettuce to the overseas market such as Japan where it is a quarantined pest. Ultralow oxygen treatments were studied for control of the insect on iceberg lettuce. Small-scale ultralow oxygen treatments in plastic jars were conducted at 1, 5, and 10 degrees C for different durations to determine effective treatment against nymphs and alates of N. ribisnigri. At oxygen levels of 0.015-0.025%, N. ribisnigri can be controlled in 3 d at 1 degrees C, 2 d at 5 degrees C, and 1 d at 10 degrees C. Large-scale ultralow oxygen treatments were conducted in bulk container treatment chambers with commercial iceberg lettuce heads for 2 d at 6 degrees C with oxygen levels of 0.015 and 0.025% and for 3 d at 3 degrees C with oxygen level of 0.015%. All treatments achieved complete control of N. ribisnigri. No negative impact on lettuce quality was detected after 2 wk of posttreatment storage. Therefore, the selected treatments have potential to be commercially developed for postharvest control of N. ribisnigri on iceberg lettuce.

Ultralow Oxygen Treatment for Postharvest Control of Nasonovia ribisnigri (Homoptera: Aphididae) on Iceberg Lettuce

The aphid Nasonovia ribisnigri (Mosley) is a common pest of lettuce in the United States. It hinders export of U.S. lettuce to the overseas market such as Japan where it is a quarantined pest. Ultralow oxygen treatments were studied for control of the insect on iceberg lettuce. Small-scale ultralow oxygen treatments in plastic jars were conducted at 1, 5, and 10°C for different durations to determine effective treatment against nymphs and alates of N. ribisnigri. At oxygen levels of 0.015–0.025%, N. ribisnigri can be controlled in 3 d at 1°C, 2 d at 5°C, and 1 d at 10°C. Large-scale ultralow oxygen treatments were conducted in bulk container treatment chambers with commercial iceberg lettuce heads for 2 d at 6°C with oxygen levels of 0.015 and 0.025% and for 3 d at 3°C with oxygen level of 0.015%. All treatments achieved complete control of N. ribisnigri. No negative impact on lettuce quality was detected after 2 wk of posttreatment storage. Therefore, the selected treatments have potential to be commercially developed for postharvest control of N. ribisnigri on iceberg lettuce.

Ethylene biosynthesis and ripening behaviour of ‘Hayward’ kiwifruit subjected to some controlled atmospheres

The effects of storage in air (AS), controlled atmosphere (CA) or ultra low oxygen (ULO) on ethylene biosynthesis and ripening of ‘Hayward’ kiwifruit during storage at 0 °C and post-storage at 20 °C, were investigated. Fruit were stored for 60, 120 and 180 days at 0 °C in AS, CA (2%O 2 +5%CO 2 ) and ULO (0.7%O 2 +0.7%CO 2 and 1%O 2 +1%CO 2 ). Freshly harvested fruit and fruit removed from storage were treated with 130 μl/l propylene or propylene-free air for 9 days at 20 °C. Fruit treated with propylene at 20 °C at harvest produced ethylene with a lag period of 3 days, had concomitant 1-aminocyclopropane-1-carboxylic acid (ACC) production, 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) activities, and were ripe after 3–5 days while fruit not treated with propylene were not able to produce ethylene and ripen during the 9 days experiment. AS fruit softened faster during the first 60 days of storage. This effect was reduced in CA and ULO treatments. The soluble solids content (SSC) increased markedly during the first 60 days of storage and remained almost constant thereafter in all treatments. After 9 days shelf life, only AS and CA stored fruit were ripe. Fruit from ULO storage required propylene treatment to ripen fully. When kiwifruit were placed at 20 °C, after 60, 120 or 180 days storage at 0 °C, there was an induction of ethylene production with no lag period in fruit from AS or CA, with or without propylene. There was some ACC content and ACC synthase activity after 60 days storage for all treatments, while ACC oxidase activity increased only upon rewarming of the fruit in AS or CA. Kiwifruit removed from ULO-storage showed drastically reduced capacity to produce ethylene mainly due to low ACC oxidase activity rather than reduced ACC production or ACC synthase activity. Respiration increased upon rewarming of the fruit in all treatments. With storage time, there was a decrease in the capacity of the warmed fruit to produce ethylene and CO 2 as well as in the activities of ACC synthase and ACC oxidase, mostly after 60 days storage.

Efecto del almacenamiento en atmósferas bajas en oxígeno sobre la calidad e incidencia de escaldado superficial en manzanas Topred / Effect of low-oxygen atmospheres on quality and superficial scald of Topred apples

In a 2-year study, Topred (TR) apples harvested from the area of Lleida (NE Spain) were treated with 3 rates (0, 1000 and 2000 ppm) of diphenylamine (DPA) and held in 3 different experimental storage conditions: standard controlled atmosphere (CA) with 3% O2 and 3% CO2; low oxygen (LO) atmosphere with 2% O2 and 2% CO2; ultra-low oxygen (ULO) atmosphere with 1% O2 and 1% CO2. All samples were maintained at 1 °C and 93-94% relative humidity. The incidence of super ficial scald and quality parameters were assessed in February, April and June, after storage plus 1 and 7 days at 20 °C, in samples from each treatment (anti-scald rate and storage atmosphere). Storage in ULO was effective in extending the storage life of the fruit. Firmness retention was better in these fruits than in fruits held in CA and LO storage; generally, after a 7-day post-storage holding period at 20 °C, the differences were maintained. The soluble solids content and titratable acidity were similar for all treatments. These changes were similar for the 2 years studied. Over one season (1993-94) the ULO atmosphere provided the best control of superficial scald in TR apples, although a low concentration of anti-scald was necessary in some cases. During the 7-day post-storage holding period the fruit of all treatments showed an increased incidence of scald, but fruit from the ULO treatment could be considered acceptable for market distribution. Susceptibility of fruit to scald exhib ited seasonal variation; in the 1994-95 season, DPA treatment was necessary to control scald in ULO apples. No appreciable increase in low O2 injury was found in this cultivar held in 1 or 2% O2.