Controlled Atmosphere Treatments Research Articles

Unique molecular mechanisms revealed for the effects of temperature, CA, ethylene exposure, and 1-MCP on postharvest senescence of broccoli

The management of postharvest broccoli (Brassica oleracea L. var. italica) exemplifies a crucial element in ensuring agricultural sustainability and food preservation. The main aim of our study was to investigate the physiological and molecular factors that influence the shelf life of broccoli by employing several technologies known to influence its deterioration, namely controlled atmosphere (CA), 1-methylcyclopropene (1-MCP), and ethylene interventions. Controlled atmosphere (CA) and 1-methylcyclopropene (1-MCP) delay the senescence process whereas ethylene promotes broccoli senescence. The study involved physiological assessments to investigate the broccoli senescence patterns as influenced by temperature, and the effects of CA, 1-MCP, and ethylene on the shelf life of broccoli. Concurrently, RNA sequencing and subsequent analysis improved our understanding of the intricate molecular mechanisms behind postharvest senescence. The application of 1-MCP and CA demonstrated significant delays in the senescence process, affirming their effectiveness in maintaining broccoli quality during postharvest storage. We found that the MAPK pathway during 1-MCP treatment was involved in stress and defense responses by expression of genes like WRKY33, WRKY29, EIN3, PYL4, Catalase 2-like (CAT2 like), and SRK2E. Furthermore, alterations in auxin-responsive genes like IAA, SAUR21, and SAUR36 highlight the differential modulation of ethylene and auxin signaling pathways. A subsequent experiment demonstrated that in postharvest broccoli, exogenous auxin promotes senescence and auxin inhibitors retard senescence. Downregulation of key enzymatic genes, including UTP-glucose-1-phosphate uridylyltransferases, during CA treatment points to inhibition of glycolysis, which might be one of the mechanisms to enhance the shelf life of harvested products and delay senescence. Senescence-associated gene expression patterns suggested stage-specific connections that need additional investigation. This study offers valuable insights into the field of postharvest management, providing practical knowledge by identifying target genes for enhancing broccoli storage life and mitigating food waste.

Low O2 and high CO2 atmospheres have no impact on efficacy of phytosanitary irradiation doses for Drosophila suzukii larvae

Use of irradiation as a phytosanitary treatment has been restricted in atmospheres with low O2 because extreme low O2 exposure can potentially induce radioprotective responses and enhance survival after irradiation. In addition to being low in O2, many controlled atmosphere treatments and modified atmosphere packaging materials maintain high CO2 levels along with low O2. Few studies have combinatorically tested the combined effects of high CO2 and low O2 on radiation sensitivity, and none have done so in a fully factorial design. Here we exposed larvae of the fly Drosophila suzukii to a range of concentrations of low O2 and high CO2 at a series of radiation doses up to 60 Gy. We found that low levels of O2 (≤ 5 kPa) induced a radioprotective response, with the radioprotective response greatest at the lowest O2 concentrations (2.5 & 0 kPa). Adding CO2 significantly decreased this protective response of low O2 on healthy adult emergence when O2 was 2.5 & 5 kPa, but this effect was only apparent at lower radiation doses, well below those used for phytosanitary treatments for this pest. Our study suggests that either controlled atmospheres or modified atmosphere packaging will not challenge the efficiency of phytosanitary irradiation for D. suzukii, and that high CO2 may act as an additional mitigation measure to disinfest insect pests from fresh commodities.

Tweedle gene family of Drosophila suzukii (Matsumura) larva enhances the basal tolerance to cold and hypoxia.

Drosophila suzukii (Matsumura) is considered a quarantine pest in the A2 list because it causes serious infection and huge economic losses. Cold and controlled atmosphere treatments have been used to control immature stage pests in fresh fruits. Herein, the basal tolerance response of D. suzukii egg, larva and pupa to cold and hypoxia stress were studied, and underlying transcriptome mechanisms in the larva were pinpointed. The third instar was more tolerant than 12-h-old egg and 8-day-old pupa when treated at 3 °C + 1% O2 for 7 days, with 34.00% ± 5.22% larval survival. Hypoxia influenced the effect of cold treatment on D. suzukii. Larval survival decreased at 3 °C + 1% O2 , but increased at 0 °C + 1% O2 . Survival increased with temperature between 0 and 5 °C + 1% O2 , but decreased significantly at 25 °C + 1% O2 . RNA-sequencing results showed that the Tweedle (Twdl) family was upregulated and uniquely enriched in larvae treated at 3 °C + 1% O2 . In addition, RNA interference-mediated silencing of a key Twdl gene reduced the survival rate after cold and hypoxia treatment. Hypoxia was able to influence the effect of cold treatment on the survival of D. suzukii positively or negatively. Structural constituents of the chitin-based cuticle, in particular Twdl genes, body morphogenesis, and ATP synthesis-coupled proton transport were involved in the tolerance to cold and hypoxia. In future, the Twdl gene could be used as a nanocarrier delivering RNA pesticides to control D. suzukii in the field and so prevent its worldwide spread. © 2023 Society of Chemical Industry.

Survival of Plodia interpunctella (Hübner) larvae treated with 98% N2 and the life history of their next generation.

Understanding the development and reproduction of insects surviving controlled atmosphere treatment may help in developing sound pest management strategies. The developmental duration, survival percentage, and oviposition of Plodia interpunctella and its F1 generation were determined after the fifth instar larvae (the last-stage larvae) were exposed to 98% N2 for different exposure times. The survival percentage of the last-stage larvae treated with 98% N2 for 6, 4, 1.5, and 0 day was 70, 80, 91, and 100%, respectively when measured 24 h after treatment. The survival percentage of the last-stage larvae that developed to pupae was 37, 55, 73, and 96%, corresponding to the different exposure times. The developmental time needed to pass from pupa to adult emergence of specimens treated as the last-stage larvae were 8, 7, 6, and 6 days corresponding respectively to high N2 treatment after 6, 4, 1.5, and 0 day of exposure. The mean number of eggs laid by the subsequent females developed from the treated last-stage larvae was 35, 66, 81, and 123, respectively. The oviposition inhibition ratio of the F1 generation decreased by more than 33% compared with that of the parental generation. When the last-stage larvae were exposed to 98% N2 for longer than 4 days, the immature developmental time of surviving individuals in the F1 generation was delayed more than 6 days due to slower egg hatching and longer development of the first and second instar larvae stages. The population trend index of the F1 generation was lower when raised from the treated last-stage larvae than those from untreated controls.

Effects of Long-Term Low Oxygen Storage Treatment on Survival of Rice Weevil (Sitophilus oryzae) and Confused Flour Beetle (Tribolium confusum).

There is a need for alternative treatments for postharvest pests on stored products. In this study, 45-d long-term controlled atmosphere (CA) treatments with 3, 5, 6.5, and 8% O2 were studied to determine effects on survival and development of rice weevil (Sitophilus oryzae) and confused flour beetle (Tribolium confusum) eggs and susceptibility of different life stages to a 14-d 5% O2 treatment. Low oxygen treatments were effective against S. oryzae and T. confusum. The 45-d CA treatments with 6.5, 5, and 3% O2 resulted in 0.26, 0.004, and 0% survival rates from egg to adult respectively for S. oryzae and 6.51, 0.14, and 0% survival rates from egg to later stages respectively for T. confusum. For both species, eggs were more susceptible to low oxygen treatment than larvae or pupae. A 14-d CA treatment with 5% O2 resulted in 4.9 and 3.3% survival of eggs of S. oryzae and T. confusum, respectively, as compared with over 50% survival of larvae and pupae for both species. S. oryzae adults, however, were very susceptible to low oxygen treatment and 14-d exposure to 5% O2 atmosphere resulted in zero survival. In contrast, the 14-d exposure to 5% O2 atmosphere resulted in over 94% survival for T. confusum adults. This study suggested there were considerable differences between stored product insects in susceptibility to low oxygen treatment and that long-term CA storage treatments with a low oxygen level of ≤6.5 and ≤5% have potential in controlling S. oryzae and T. confusum, respectively.

Controlled atmosphere storage alleviates internal browning in flat peach fruit by regulating energy and sugar metabolisms

Flat peach fruit are cold-sensitive and vulnerable to chilling injury (CI), particularly internal browning (IB) during cold storage, which limits the consumer acceptance and market value of the fruit. Controlled atmosphere (CA) has been used to alleviate IB in fruit. However, the mechanisms of CA on IB in peach remains unknown. This study investigated the effects of CA (3–3.5% Oxygen, 3–3.5% Carbon dioxide, and 93–94% nitrogen) treatment on IB development, sugar metabolism, and energy metabolism in cold-stored (1 ± 0.5 °C) peach. The CA treatment effectively inhibited the development of IB and markedly inhibited the reduction of sugar contents and energy charge. The protein expression of the V-type proton ATPase subunit was significantly inhibited by the CA treatment, accompanied by higher adenosine triphosphate (ATP) content, and energy charge than the control fruit. Notably, the expressions of the pyruvate kinase family of proteins, pyruvate decarboxylases, and sucrose synthase were induced by CA treatment that had complex protein interactions with the ATPase and the energy metabolism pathway. These results indicated that CA treatment enhanced the chilling tolerance attributed to maintaining higher levels of energy status and sugar contents by regulating the expression of key proteins involved in energy metabolism during cold storage and shelf life. Taken together, our study can provide theoretical support for the research and development of fresh-keeping and cold-chain logistics technology.

Changes of Sensory Quality, Flavor-Related Metabolites and Gene Expression in Peach Fruit Treated by Controlled Atmosphere (CA) under Cold Storage.

Controlled atmosphere (CA) has been used to alleviate chilling injury (CI) of horticultural crops caused by cold storage. However, the effects of CA treatment on peach fruit sensory quality and flavor-related chemicals suffering from CI remain largely unknown. Here, we stored peach fruit under CA with 5% O2 and 10% CO2 at 0 °C up to 28 d followed by a subsequent 3 d shelf-life at 20 °C (28S3). CA significantly reduced flesh browning and improved sensory quality at 28S3. Though total volatiles declined during extended cold storage, CA accumulated higher content of volatile esters and lactones than control at 28S3. A total of 14 volatiles were positively correlated with consumer acceptability, mainly including three C6 compounds, three esters and four lactones derived from the fatty acid lipoxygenase (LOX) pathway. Correspondingly, the expression levels of genes including PpLOX1, hyperoxide lyase PpHPL1 and alcohol acyltransferase PpAAT1 were positively correlated with the change of esters and lactones. CA elevated the sucrose content and the degree of fatty acids unsaturation under cold storage, which gave us clues to clarify the mechanism of resistance to cold stress. The results suggested that CA treatment improved sensory quality by alleviating CI of peach fruits under cold storage.

Effects of controlled atmosphere and storage temperature on the quality of shelled ‘Barton’ pecan nuts during long-term storage

This study aimed to evaluate the effects of controlled atmosphere (CA) storage at a low oxygen partial pressure (pO2; 2 kPa of O2) and low pO2 associated with high pCO2 (2 kPa O2 + 15 kPa CO2) in relation to ambient atmospheric conditions (control), at different temperatures, on shelled ‘Barton’ pecan nuts quality after storage. Color, respiration rates, moisture content (MC), and oxidation markers, such as peroxide value (PV), acidity value (AV), and volatile compounds (VC), were evaluated. During six months of storage, the MC decreased in all CA treatments, and treatments at 10 °C had the lowest AVs and PVs. However, the treatment with high pCO2 levels also guaranteed lower AVs at 20 °C. The color parameter b* (yellow), which is related to the golden appearance of pecans and is a highly desirable visual attribute in the commercialization of nuts, was maintained high in treatments at 10 °C with CA treatments until six months of storage. The VCs, characteristic of lipid oxidation (aldehydes, acids, alcohols, and ketones), increase in all treatments with prolonging storage. When pCO2 was associated to 10 °C at six month of storage, it showed a larger area in the acids and unsaturated aldehyde classes, while it was relevant for alcohols, lactones, and esters at 20 °C, with sweet characteristics, including ethyl ethanoate, ethyl hexanoate, and butyrolactone. Thus, this study shows another advance in the storage techniques of shelled pecans, pointing to alternatives for reducing energy costs in the cooling chain.

Aroma of mature-green and tree-ripe mangoes after refrigerated air or controlled atmosphere storage

ABSTRACT: Mango flavor is dependent on cultivar characteristics and postharvest handling procedures. Mangoes harvested with the ripening metabolism initiated develop better flavor than mangoes harvested at the mature-green stage. Different cultivars were harvested at both ripeness stages and evaluated to determine the effect of fruit ripeness, storage temperature and atmosphere on the volatiles present in aroma profiles. Mangoes of the cultivars Haden, Keitt and Tommy Atkins at distinct ripeness stages were stored in controlled atmospheres (CA) with 2, 5 or 21 kPa O2 plus 0, 10 or 25 kPa CO2 at 5, 8, 12 or 15 °C. Terpene concentrations of mangoes stored in air were higher than the concentrations in mangoes stored in CA. The sesquiterpene α-copaene did not present recognizable peaks in almost all elusion sequences. The same result was observed with the monoterpene β-pinene in cv. Haden and cv. Keitt mangoes while in ‘Tommy Atkins’ fruit β-pinene concentrations were below 1.06 µL.L-1. Ethanol and acetaldehyde concentrations were significantly higher in mangoes from 2 kPa O2 storage than those from air storage or the other CA treatments. Terpene synthesis in air or CA storage in all cultivars varied significantly, preventing generalizations as to what storage conditions favor or limit aroma components elution.

Effects of 1-methylcyclopene and controlled-atmosphere treatment on the quality and antioxidant capacity of blueberries during storage

Abstract The effects of 1-methylcyclopropene (1-MCP) treatment and controlled-atmosphere (CA) storage and their combination on quality and antioxidant capacity of postharvest blueberries were evaluated here. To investigate the most appropriate approach for maintaining fruit quality, blueberries were subjected to four different treatments, a control (CK), 1-MCP, 3% O2 + 10% CO2 (CA), and 1-MCP combined with 3% O2+10% CO2 (1-MCP + CA), then stored for 80 days at 0 °C. It was found that the applications of 1-MCP, CA and 1-MCP + CA were effective at delaying the increase in weight loss and inhibiting the decrease in firmness, total soluble solids (TSS) contents and titratable acidity (TA) contents. In addition, 1-MCP, CA and 1-MCP + CA treatment could significantly suppress MDA accumulation and relative electrolytic leakage promotion. Moreover, the production of reactive oxygen species (ROS), such as O2- and H2O2, was reduced by all the treatment, which was associated with increased activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Taken together, our findings indicate 1-MCP, CA and 1-MCP + CA have potential applications in maintaining the quality and improving the antioxidant capacity of harvested blueberries, and 1-MCP + CA is the most effective treatment.

Studies on the application of bio-carbon dioxide as controlled atmosphere on pest management in wheat grain storage

The study evaluated the viability of purified waste gas called bio-CO2 (CO2 ≥ 98%, CH4 ≤ 2.0%, v/v), which is a byproduct from a compressed biogas (CBG) plant, as a new source of CO2 for control atmosphere for wheat grain storage. The findings were compared with the use of pure CO2 on mortality of Rhyzopertha dominica adults, seed germination, and nutritional quality of wheat grain for two and six months storage periods. Fifteen tapered plastic bottles of 1 L storage volume were taken for grain storage. Insect mortality of 100% was found in 1, 3, and 5 days using bio-CO2 and 4, 6, and 8 days with pure CO2 at 80, 60, and 40% concentration, respectively. In control grain infested with R. dominica, the adult insect triplicated in six weeks, 3.9 times in two months, and 10.4 times in 6 months storage. There were no significant differences (p > 0.05) observed in seed weight stored for two and six months under the bio-CO2 fumigation. Whereas, seed weight loss of about 5.03 ± 0.8% in control without infestation and 17.25 ± 1.2% in grain infested with R. dominica were reported over two months storage. Similarly, no weight loss during controlled atmosphere treatment, 12.66 ± 0.34% in control, and 27.42 ± 0.96% with R. dominica were found for six months storage period. The seed germination was significantly affected at 80% CO2 using both the controlled atmosphere for grain stored for six months. The major nutrient contents remained non-significant (p > 0.05) under both the fumigants. Whereas, carbohydrate content was significantly reduced (p < 0.05), and protein content was increased in control without infestation and grain infested with R. dominica.

Multimycotoxin Determination in Grains: A Comprehensive Study on Method Validation and Assessment of Effectiveness of Controlled Atmosphere Storage in Preventing Mycotoxin Contamination.

Two simple and low-cost QuEChERS approaches were optimized and validated for multimycotoxin determination in grains by UPLC-MS/MS and applied to assess effectiveness of controlled atmosphere (CA) storage in preventing mycotoxin contamination. Common bean, soybean, and maize samples were stored for 6 months. CA treatments were conducted varying O2 and CO2 partial pressures, temperatures, and moisture contents of the chambers. In the validation study for common bean and maize, 8 out of 11 mycotoxins were successfully validated. For soybean, 10 out of 11 mycotoxins were validated. Aflatoxin B1 was detected in all commodities. Statistical tests suggest that storage temperature played a key role in aflatoxin B1 concentrations in common bean and soybean, but had no influence on maize. Maize was also positive for fumonisins B1 and B2. Differences in fumonisin concentrations were not significant among different treatments. Concentrations of aflatoxin B1 in some samples exceeded legislation's maximum levels. Thus, some of the CA treatments applied were effective in preventing mycotoxin contamination in common bean and soybean but were not effective for maize.

Effects of controlled atmosphere on browning, redox metabolism and kernel quality of fresh in-hull walnut (Juglans regia L.)

The green hull of fresh walnuts (Juglans regia L.) is highly susceptible to browning and accompanied with deterioration of the walnut quality, and the currently available preservation technologies still do not meet the market threshold supply of fresh walnut. This study investigated the effect of controlled atmosphere (CA) storage alone and combination with 1-Methylcyclopropene (1-MCP) on hull browning and kernel quality of fresh in-hull walnut. Fresh in-hull walnuts were treated with air (Control), CA (5% O2, 7.5% CO2), 1-MCP (0.5 μL L−1) + CA and stored at 0 ± 0.5 °C for 100 d. Browning incidence, hull redox metabolism, kernel color and walnut oil quality were analyzed. The results showed that CA promoted the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), maintained total phenol (TP), γ-aminobutyric acid (GABA), ascorbic acid (ASA), and glutathione (GSH) contents, inhibited ethylene production, reduced reactive oxygen species (ROS) accumulation, and delayed the hull browning. Besides, CA attained the highest kernel quality through inhibited the decrease of kernel color value and moisture content, and reduced acid value (AV) and peroxide value (POV) of walnut oil. While 1-MCP + CA treatment increased the activities of antioxidant enzymes, the combination weakened the other positive effects of CA. However, hull browning and kernel deterioration in 1-MCP + CA were less than that observed in air control. Overall, CA was an effective method for the preservation of fresh in-hull walnut at 0 ± 0.5 °C.

Physiological responses and quality attributes of muscadine grape (Vitis rotundifolia Michx) to CO2-enriched atmosphere storage

Abstract Muscadine grape (Vitis rotundifolia Michx) is a non-climacteric fruit that rapidly loses quality during storage. This study aimed to assess the effect of controlled atmosphere (CA) on quality parameters and muscadine grapes decay. Berries of two muscadine grape cultivars, Triumph, and Supreme, were stored at 4 °C with 95 % relative humidity in either regular air (AIR), regular CA (RCA) (6 % O2 + 10 % CO2), or CA with extreme CO2 level (ECA; 4 % O2 + 30 % CO2) for up to 42 d. Treated berries with either RCA or ECA provided better control of weight loss. Both CA treatments reduced decay incidence, but there was no decay in ECA berries after 42 d for both cultivars and no evidence of CO2 injury. The results showed that berry softening was significantly delayed by RCA and ECA, which had a lower ethylene production rate than berries exposed to AIR. Application of RCA and ECA also retained greater total antioxidant activity, total phenolic compounds, and firmness compared to AIR. These results demonstrate that maintaining CA conditions postharvest leads to improved preservation of compositional quality and delayed softening and decay of harvested muscadine grapes compared with AIR storage.

The isolated or combined effects of dynamic controlled atmosphere (DCA) and 1-MCP on the chemical composition of cuticular wax and metabolism of ‘Maxi Gala’ apples after long-term storage

Apples have a continuous hydrophobic layer that covers the surface of the fruit, which is called the cuticle. The effects of 1-methylcyclopropene (1-MCP) on the cuticular wax layer of apples were reported after cold storage, although the interaction between 1-MCP and dynamic controlled atmosphere (DCA) is not yet known. Therefore, this study aimed to analyze the effects of 1-MCP on the wax composition and metabolism of ‘Maxi Gala’ apples after storage in a controlled atmosphere (CA) and dynamic controlled atmosphere based on chlorophyll fluorescence (DCA-CF) and respiratory quotient (DCA-RQ; RQ = 1.3 and 1.5). The 1-MCP treatment effectively decreased ethylene production for CA and DCA-CF treatments, while in DCA-RQ treatments produced no effect. The average extracted cuticular wax content of ‘Maxi Gala’ apples was 16.65 g m−2 and no differences in storage conditions or 1-MCP application were observed. Alkanes, alcohols, fatty acids, aldehydes, and terpenoids were identified in the chemical composition of the cuticular waxes, being alkanes and fatty acids the predominant ones. Moreover, 1-MCP decreased fatty acid and 10-nonacosanol concentrations in the fruit. Fruit with the 1-MCP application and stored in DCA had lower α-farnesene concentrations. The wax compositions of the DCA-stored apples with and without 1-MCP were similar. However, 1-MCP treatment resulted in a greater mass loss in fruit stored in DCA.

Microbiological and Physiological Attributes of Fresh-Cut Cucumbers in Controlled Atmosphere Storage

Fresh-cut cucumbers are popular worldwide, but they are prone to spoilage due to tissue damage caused by processing. The effects of controlled atmosphere storage (CAS) at 3% O2 and 7% CO2 or 8% O2 and 2% CO2 on microorganisms and the quality of fresh-cut cucumbers (Cucumis sativus L. cv. Chinese Long) at 4°C and 90% relative humidity were investigated in this study. The results showed that compared with the control group, both controlled atmosphere treatments maintained chlorophyll concentration, appearance, and color of fresh-cut cucumbers effectively; inhibited respiration rate and polyphenoloxidase (PPO) and peroxidase (POD) activity; delayed the decrease in firmness and the increase in relative electrolyte leakage; and inhibited the growth of microorganisms on cucumbers during storage. On day 10, the chlorophyll concentration and firmness of cucumbers stored at 3% O2 and 7% CO2 was 1.15 and 1.04 times that of cucumbers stored at 8% O2 and 2% CO2, respectively. Respiration rate, relative electrolyte leakage, polyphenoloxidase activity, peroxidase activity, and levels of total bacteria, coliforms, and Pseudomonas spp. at 3% O2 and 7% CO2 were 19.79, 6.01, 5.45, 88.50, 18.07, 16.14, and 19.76% lower than at 8% O2 and 2% CO2, respectively. In conclusion, storage at 3% O2 and 7% CO2 was effective in inhibiting microorganisms and maintaining the quality of stored fresh-cut cucumbers.

Graduated Controlled Atmosphere: A Novel Approach to Increase "Duke" Blueberry Storage Life.

Blueberries (Vaccinium corymbosum L.) are highly valued for their health-promoting potential, yet they are extremely perishable. Controlled atmosphere (CA) strategies reduce blueberry respiratory metabolism, slowing down senescence. However, the sudden change of atmosphere could elicit a physical abiotic stress in the fruit, negatively affecting quality. We propose an innovative approach based on controlled graduation to slowly reach optimum gas storage conditions as an alternative to standard CA. For two consecutive seasons, “Duke” blueberries were subjected to four different storage conditions: control (air); standard CA (sudden exposure to 5 kPa O2 and 10 kPa CO2 across the experiment); GCA3 and GCA7 (gradually reaching 5 kPa O2 and 10 kPa CO2 in 3 and 7 days, respectively). Fruit were stored for 28 days at 0 ± 0.5°C. Real-time respirometry provided an in-depth insight to the respiratory response of blueberries to their gas environment. Blueberries subjected to the graduated application of CA (GCA) treatments had a lower steady-state respiration rate compared to control and standard CA fruit. This indicated a reduction in metabolic activity that positively impacted quality and storage life extension. For example, GCA3 and GCA7 blueberries had a 25% longer storage life when compared to control, based on reduced decay incidence. In addition, GCA fruit were 27% firmer than control and CA fruit after 28 days of cold storage. GCA3 had a positive effect on maintaining individual sugars concentrations throughout the experiment, and both GCA treatments maintained ascorbic acid content close to initial values compared to a decrease of 44% in the control fruit at the end of the experiment. This work provides a paradigm shift in how CA could be applied and a better understanding of blueberry physiology and postharvest behavior.

Fifty Ohm radio frequency heating treatment under controlled atmosphere for inactivating Escherichia coli ATCC 25922 inoculated on almond kernels

The purpose of the study was to validate effects of radio frequency (RF) heating under controlled atmosphere (CA) on thermal inactivation of E. coli ATCC 25922 in almond kernels. A 2.4 kW, 27.12 MHz, 50 Ω RF heating system was used to treat 1.5 kg size almond kernel samples with the adjusted moisture content of 8.0% wet basis under regular atmosphere (RA, 21% O2, 79% N2) and CA (2% O2, 20% CO2, 78% N2) conditions. The power level of 900 W under an electrode gap of 11.5 cm was used at the ramping stage for quick heating, and a maximum temperature difference of 3 °C in the inoculation area was achieved by continuing the RF heating at reduced power level during the 40 min holding stage. A 4-log reduction time under CA treatment was achieved with 21 ± 1 min holding at 75 ± 3 °C, reducing treatment time by 38% as compared with RA environment. The various quality attributes of treated samples remained within acceptable range based on nut industry standards. The RF heating under CA conditions may hold potential as an effective treatment method to control E. coli ATCC 25922 in raw almond kernels and be possibly extended for pasteurization applications.

Chlorine dioxide and sodium diacetate treatments in controlled atmospheres retard mold incidence and maintain quality of fresh walnuts during cold storage

Fresh walnuts deteriorate and develop mold rapidly during cold storage. The effects of chlorine dioxide (ClO2) and sodium diacetate (SDA) in controlled atmosphere (CA) storage on deterioration of fresh walnuts have been investigated. 'Xifu No.1′ fresh walnuts were treated with air (Control), air +200 mg kg−1 sodium diacetate (SDA), air +50 mg L−1 chlorine dioxide (ClO2), 2 % O2 + 25 % CO2 (CA), CA + SDA and CA + ClO2 and then stored at 0 ± 1 °C for 135 d. Mold incidence, nutrient quality, oil quality and physiological indices of the walnuts were analyzed. The results showed that CA, CA + SDA, CA + ClO2 treatments delayed the development of mold, increased POD activity while decreasing PPO activity, and maintained quality of fresh walnuts in comparison to air treatments. CA + SDA and CA + ClO2 maintained higher melatonin content and lower peroxide and carbonyl values of fresh walnuts than CA treatment alone, but no difference in mold incidence were detected between CA and CA + SDA treatments. Overall, CA + ClO2 was the optimal treatment and kept quality of fresh walnuts for 135d at 0 ± 1 °C, with the lowest mold incidence (5 %), the highest firmness and contents of fat and melatonin, as well as the maximum POD activity.

The Increase of Bioactive Ingredients by Solid State Fermentation of Inonotus obliquus with Spent Substrate

In Taiwan, an estimated 200 thousand tons of spent mushroom substrates were produced annually for growing mushrooms. With the aim of identifying the best production conditions of the fruiting body with the spent substrates. The objective of this study was to determine the feasibility of production of Inonotus obliquus by solid state fermentation (SSF), using spent mushroom substrate with controlled atmosphere and adding corn and rice grain and birch and mulberry powder. The results of this study revealed two major trends. First, the SSF process in a controlled atmosphere with corn grain and mulberry powder added can substantially increase the bioactive ingredient content of the fruiting body even with spent substrate. Second, the contents of heavy metals were plunged to average 6.4% than the ones of fresh sawdust substrate after two round of fermentation with I. obliquus. Overall, the best results were achieved when spent substrate with corn grain and 10% mulberry powder, and the process was carried out in a controlled atmosphere, with the betulinic acid content, polysaccharide content, and DPPH radical scavenging potential being 1.03 mg/g, 29.3 mg/g, and 94.3%, respectively. These findings demonstrated the bioactive ingredient content of the fruiting body obtained via SSF with spent substrate and controlled atmosphere treatment can be increased. This innovation ventilation fermentation model with spent substrate was more economic by conservation of the usage of timber. The dramatically decreased trends of heavy metal of substrates and fruit bodies was lead to safety of ingestion of mushrooms. The innovation ventilation fermentation model with spent substrate of Inonotus obliquus