Changes in the activity of flavanone 3ß-hydroxylase in blueberry fruit during storage in ozone-enriched atmosphere.

BACKGROUND: The present study aimed to determine whether the ozonation process affects the flavonoid biosynthesis in highbush blueberry (Vaccinum corymbosum L.) fruit. Flavanone 3ß-hydroxylase (F3H) was used as a marker of the flavonoid biosynthesis pathway. The activity of F3H, the expression of gene encoding F3H and the antioxidant status in blueberries treated with ozone at a concentration of 15 ppm for 30 min, every 12 h of storage, and maintained at 4 °C for 4 weeks were investigated. RESULTS: The results showed that ozonation process increases the expression of the F3H gene after 1 week of storage, which translates into a higher catalytic capacity of protein, as well as a higher content of flavonoids and total antioxidant potential of ozonated blueberries compared to non-ozonated fruits. CONCLUSION: The present study provides experimental evidence indicating that ozone treatment in proposed process conditions positively affects flavonoid metabolism in highbush blueberry fruit leading to the maintainance of the high quality of the fruit during storage. © 2021 Society of Chemical Industry.

Identities, concentrations, and sources of pesticide exposure in pollen collected by managed bees during blueberry pollination.

Bees are critical for crop pollination, but there is limited information on levels and sources of pesticide exposure in commercial agriculture. We collected pollen from foraging honey bees and bumble bees returning to colonies placed in blooming blueberry fields with different management approaches (conventional, organic, unmanaged) and located across different landscape settings to determine how these factors affect pesticide exposure. We also identified the pollen and analyzed whether pesticide exposure was correlated with corbicular load composition. Across 188 samples collected in 2 years, we detected 80 of the 259 pesticide active ingredients (AIs) screened for using a modified QuEChERS method. Detections included 28 fungicides, 26 insecticides, and 21 herbicides. All samples contained pesticides (mean = 22 AIs per pollen sample), with pollen collected from bees on conventional fields having significantly higher average concentrations (2019 mean = 882.0 ppb) than those on unmanaged fields (2019 mean = 279.6 ppb). Pollen collected by honey bees had more AIs than pollen collected by bumble bees (mean = 35 vs. 19 AIs detected at each farm, respectively), whereas samples from bumble bees had higher average concentrations, likely reflecting differences in foraging behavior. Blueberry pollen was more common in pollen samples collected by bumble bees (25.9% per sample) than honey bees (1.8%), though pesticide concentrations were only correlated with blueberry pollen for honey bees. Pollen collected at farms with more blueberry in the surrounding landscape had higher pesticide concentrations, mostly AIs applied for control of blueberry pathogens and pests during bloom. However, for honey bees, the majority of AIs detected at each farm are not registered for use on blueberry at any time (55.2% of AIs detected), including several highly toxic insecticides. These AIs therefore came from outside the fields and farms they are expected to pollinate. For bumble bees, the majority of AIs detected in their pollen are registered for use on blueberry during bloom (56.9% of AIs detected), though far fewer AIs were sprayed at the focal farm (16.7%). Our results highlight the need for integrated farm and landscape-scale stewardship of pesticides to reduce exposure to pollinators during crop pollination.

Budbreak patterns and phytohormone dynamics reveal different modes of action between hydrogen cyanamide- and defoliant-induced flower budbreak in blueberry under inadequate chilling conditions.

Under inadequate chilling conditions, hydrogen cyanamide (HC) is often used to promote budbreak and improve earliness of Southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrids). However, HC is strictly regulated or even banned in some countries because of its high hazardous properties. Development of safer and effective alternatives to HC is critical to sustainable subtropical blueberry production. In this study, we examined the efficacy of HC and defoliants as bud dormancy-breaking agents for 'Emerald' blueberry. First, we compared water control, 1.0% HC (9.35 L ha-1), and three defoliants [potassium thiosulfate (KTS), urea, and zinc sulfate (ZS)] applied at 6.0% (28 kg ha-1). Model fitting analysis revealed that only HC and ZS advanced both defoliation and budbreak compared with the water control. HC-induced budbreak showed an exponential plateau function with a rapid phase occurring from 0 to 22 days after treatment (DAT), whereas ZS-induced budbreak showed a sigmoidal function with a rapid phase occurring from 15 to 44 DAT. The final budbreak percentage was similar in all treatments (71.7%-83.7%). Compared with the water control, HC and ZS increased yield by up to 171% and 41%, respectively, but the yield increase was statistically significant only for HC. Phytohormone profiling was performed for water-, HC- and ZS-treated flower buds. Both chemicals did not increase gibberellin 4 and indole-3-acetic acid production, but they caused a steady increase in jasmonic acid (JA) during budbreak. Compared with ZS, HC increased JA production to a greater extent and was the only chemical that reduced abscisic acid (ABA) concentrations during budbreak. A follow-up experiment tested ZS at six different rates (0-187 kg ha-1) but detected no significant dose-response on budbreak. These results collectively suggest that defoliants are not effective alternatives to HC, and that HC and ZS have different modes of action in budbreak induction. The high efficacy of HC as a dormancy-breaking agent could be due to its ability to reduce ABA concentrations in buds. Our results also suggest that JA accumulation is involved in budbreak induction in blueberry.

Differential mechanisms between traditionally established and new highbush blueberry (Vaccinium corymbosum L.) cultivars reveal new insights into manganese toxicity resistance.

In acid soils, manganese (Mn) concentration increases, becoming toxic to plants. Mn toxicity differentially affects physiological processes in highbush blueberry (Vaccinium corymbosum L.) cultivars. However, the mechanisms involved in Mn toxicity of the new and traditionally established cultivars are unknown. To understand Mn toxicity mechanisms, four traditionally established (Legacy, Brigitta, Duke, and Star) cultivars and two recently introduced to Chile (Camellia and Cargo) were grown under hydroponic conditions subjected to control Mn (2 µM) and Mn toxicity (1000 µM). Physiological, biochemical, and molecular parameters were evaluated at 0, 7, 14, and 21 days. We found that the relative growth rate was reduced in almost all blueberry cultivars under Mn toxicity, except Camellia, with Star being the most affected. The photosynthetic parameters were reduced only in Star by Mn treatment. Leaf Mn concentrations increased in all cultivars, exhibiting the lowest levels in Camellia and Cargo. Brigitta and Duke exhibited higher ß-carotene levels, while Cargo exhibited a reduction under toxic Mn. In Legacy, lutein levels increased under Mn toxicity. Traditionally established cultivars exhibited higher antioxidant activity than the new cultivars under Mn toxicity. The Legacy and Duke cultivars increased VcMTP4 expression with Mn exposure time. A multivariate analysis separated Legacy and Duke from Camellia; Star and Cargo; and Brigitta. Our study demonstrated that Mn toxicity differentially affects physiological, biochemical, and molecular features in the new and traditionally established cultivars, with Legacy, Duke, Camellia, and Cargo as the Mn-resistant cultivars differing in their Mn-resistance mechanisms and Star as the Mn-sensitive cultivar.

Effect of atmospheric cold plasma treatment on antioxidant activities and reactive oxygen species production in postharvest blueberries during storage.

BACKGROUND: Blueberry is universally acknowledged as a kind of berry rich in antioxidants. Cold plasma, an emerging non-thermal treatment technology, has been proved to be able to maintain or improve the antioxidant level while inactivating the microorganisms on the surface of fruits and vegetables. Postharvest blueberries were treated with atmospheric cold plasma (ACP; 12 kV, 5 kHz) for 0 s (Control), 30 s (ACP-30), 60 s (ACP-60), and 90 s (ACP-90) in this study, and the effects of ACP on the antimicrobial properties, antioxidant activities, and reactive oxygen species (ROS) production were investigated during storage at 4 ± 1 °C for 40 days. RESULTS: Total aerobic bacteria and mold populations on ACP-treated blueberries decreased significantly in a time-dependent manner (P < 0.05), and decreased by 0.34-1.24 and 0.57-0.87 log10 CFU g-1 respectively on ACP-60-treated blueberries during storage. The decay rate of blueberries was decreased by 5.8-11.7% and the decrease of blueberry firmness was slowed down by ACP-60. But the total phenol, anthocyanin, and ascorbic acid contents increased, and superoxide dismutase, catalase, and peroxidase activities were enhanced in ACP-treated blueberries. The free radical scavenging activity and total antioxidant capacity (T-AOC) were enhanced. Hydrogen peroxide (H2 O2 ) and superoxide anion (O2 - ) production rates declined by 27.3% and 41.3% at day 40 of storage, respectively. CONCLUSION: It is suggested that ACP may be a promising non-thermal treatment technology for postharvest sterilization and preservation of blueberry under suitable conditions. © 2020 Society of Chemical Industry.

Methyl jasmonate induces the resistance of postharvest blueberry to gray mold caused by Botrytis cinerea.

BACKGROUND: The effects of postharvest methyl jasmonate (MeJA) treatment (50 µmol L-1 ) on the control of gray mold caused by Botrytis cinerea in blueberry fruit were evaluated by analyzing (i) the levels of disease resistance signals; (ii) the activity of enzymes involved in antioxidant system, disease resistance and phenylpropanoid pathway, and (iii) the secondary metabolite content. RESULTS: The results indicated that MeJA treatment significantly restrained the development of gray mold decay in blueberries. The treatment induced a nitric oxide (NO) burst and increased the endogenous hydrogen peroxide (H2 O2 ) content in the earlier period of storage. The enhanced NO and H2 O2 generation by MeJA treatment might serve as a signal to induce resistance against B. cinerea infection. Furthermore, in inoculated fruit, MeJA treatment significantly promoted antioxidant enzymes and defense-related enzyme activity, which included superoxide dismutase, catalase, ascorbate peroxidase, chitinase, and ß-1,3-glucanase, and the degree of membrane lipid peroxidation was reduced. The MeJA treatment enhanced the phenylpropanoid pathway by provoking phenylalanine ammonialyase, cinnamate 4-hydroxylase, and 4-coumarate CoA ligase activity, which was accompanied by elevated levels of phenolics and flavonoids in blueberry fruit. CONCLUSION: These results suggested that MeJA could induce the disease resistance of blueberries against B. cinerea by regulating the antioxidant enzymes, defense-related enzymes, and the phenylpropanoid pathway through the activation of signaling molecules.

Inactivation of foodborne pathogens based on synergistic effects of ultrasound and natural compounds during fresh produce washing.

Ultrasound has potential to be used for disinfection, and its antimicrobial effectiveness can be enhanced in presence of natural compounds. In this study, we compared the antimicrobial effects of ultrasound at 20 kHz (US 20 kHz) or 1 MHz (US 1 MHz) in combination with carvacrol, citral, cinnamic acid, geraniol, gallic acid, lactic acid, or limonene against E. coli K12 and Listeria innocua at a constant power density in water. Compared to the cumulative effect of the individual treatments, the combined treatment of US 1 MHz and 10 mM citral generated >1.5 log CFU/mL additional inactivation of E. coli K12. Similarly, combined treatments of US 1 MHz and 2 mM carvacrol (30 min), US 20 kHz and 2 mM carvacrol, 10 mM citral, or 5 mM geraniol (15 min) generated >0.5-2.0 log CFU/mL additional inactivation in L. innocua. The synergistic effect of citral, as a presentative compound, and US 20 kHz treatment was determined to be a result of enhanced dispersion of insoluble citral droplets in combination with physical impact on bacterial membrane structures, whereas the inactivation by US 1 MHz was likely due to generation of oxidative stress within the bacteria. Combined ultrasound and citral treatments improved the bacterial inactivation in simulated wash water in presence of organic matter or during washing of inoculated blueberries but only additive antimicrobial effects were observed. Findings in this study will be useful to enhance fresh produce safety and shelf-life and design other alternative ultrasound based sanitation processes.

Ethylene plays an important role in the softening and sucrose metabolism of blueberries postharvest.

We studied the effects of ethylene on softening and sucrose metabolism in postharvest blueberry fruit by examining the responses of fruit firmness, cell wall polysaccharides, cell wall enzymes, four key genes of cell wall degradation and metabolism, enzyme activities, and five key genes of sucrose metabolism to exogenous ethylene treatments. Ethylene was found to accelerate blueberry softening, as it promoted the degradation of pectin and expression of pectinesterase (PE) and polygalacturonase (PG). Sucrose catabolism was accelerated with fruit softening, while sucrose content, sucrose phosphate synthase (SPS) activity were positively correlated with the loss of fruit firmness. Exogenous ethylene treatments promoted sucrose metabolism by inhibiting the expression of VcSPS1 and VcNIN2 and stimulating the expression of VcSS1 and VcCWINV1. These results indicate that ethylene plays an important role in fruit softening and sucrose metabolism of blueberry at 20 °C, and there may be a link between sucrose metabolism and fruit softening.

Effect of ethanol treatment on the quality and volatiles production of blueberries after harvest.

BACKGROUND: Blueberries are appreciated by consumers for their rich natural antioxidants and their good nutritional and health functions. However, blueberries are very perishable due to microbial infection and metabolic aging after harvest. Ethanol has been shown to have the effect of controlling postharvest microorganisms and improving storage quality of fruits and vegetables. This study aimed to clarify the effects of ethanol on the appearance quality and flavor attributes of postharvest blueberries. Blueberries were treated with ethanol (250, 500, and 1000 µL L-1 ) and stored at 0 ± 0.5 °C, 90% relative humidity (RH), for 40 days. RESULTS: The results indicated that ethanol treatment could slow the decline of blueberry firmness and reduce the decay rate significantly in a dose-dependent manner. The soluble solids content (SSC) and titratable acidity (TA) of ethanol-treated blueberries increased significantly (P < 0.05), improving the taste of the blueberries. The activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) were stimulated with the accumulation of ethanol in blueberries, which catalyzed the conversion of ethanol, acetaldehyde, and pyruvate, increasing their levels in blueberries. More volatiles, especially esters, were detected in ethanol-treated blueberries, e.g. methyl acetate, ethyl acetate, ethyl propanoate, ethyl isobutyrate, ethyl 2-methylbutanoate, ethyl isovalerate, ethyl 3-methyl-2-butenoate, diethyl sebacate, and isopropyl myristate. CONCLUSION: The preservative effect of ethanol on blueberry was significantly affected by ethanol concentration. In this study, the effect of 500 µL L-1 ethanol fumigation on blueberry was the best in terms of appearance quality (firmness and decay rate) and flavor attributes (SSC, TA, and volatiles). © 2019 Society of Chemical Industry.

Protective effects of bovine serum albumin on blueberry anthocyanins under illumination conditions and their mechanism analysis.

This study investigates the effects of bovine serum albumin (BSA) on blueberry anthocyanins and their interaction. Findings showed that BSA could protect blueberry anthocyanins against degradation and retain their antioxidant activity at an ideal concentration of 0.15 mg/mL under three deteriorating treatments: illumination, vitamin C + illumination, and sucrose + illumination. The fluorescence and UV absorption spectra showed that malvidin-3-o-galactoside (M3G), the major monomer in blueberry anthocyanins, led to a static quenching of BSA and the binding site of M3G to BSA was approximately one. Further, the interaction was a spontaneous process with electrostatic interactions being the main force. CD spectra and synchronous fluorescence spectra presented alterations in the secondary structure and microenvironment of Trp and Tyr residues of BSA, respectively, upon interaction with M3G. Finally, molecular docking analysis showed that M3G mainly bound the II and III domains of BSA by hydrogen bonds and electrostatic interaction. In conclusion, our study highlights the protective effects of BSA on the stability and anti-oxidant activity of blueberry anthocyanins and their interaction analysis.

Effect of sodium nitroprusside on antioxidative enzymes and the phenylpropanoid pathway in blueberry fruit.

The purpose of this study is to investigate the effects of sodium nitroprusside (SNP) treatment after harvest on the activity of antioxidative enzymes and the phenylpropanoid pathway of blueberries. Blueberry fruits were dipped in 1.0 mmol/L SNP solution for 10 min and stored at 4 °C. Fruits treated with distilled water were used as the control. The results indicated that SNP significantly inhibited the increase of weight loss and enhanced the ascorbic acid content of blueberry fruit. Moreover, SNP increased the activity of phenylalanine ammonia-lyase, 4-coumarate-CoA ligase, polyphenol oxidase, superoxide dismutase, glutathione reductase, ascorbate peroxidase, peroxidase, and hydrogen peroxide in blueberry fruit. The accumulation of lignin and anthocyanin in the fruit was also stimulated by the SNP treatment. These results demonstrate that SNP treatment could maintain the antioxidant ability of blueberries by regulating the phenylpropanoid pathway and antioxidant enzymes.

Effect of postharvest application of ethylene on the profile of phenolic acids and anthocyanins in three blueberry cultivars (Vaccinium corymbosum).

BACKGROUND: The blueberry is a fruit that has been studied extensively for its health benefits, mainly due to its high antioxidant activity. There is a strong correlation between antioxidant activity and total anthocyanin and phenolic compound content. Postharvest treatment using ethylene may be a factor affecting the anthocyanin content. The objective of this work was to analyze postharvest treatment using ethylene on the anthocyanin profile during the storage of blueberries and phytochemical composition of 'Bluecrop', 'Goldtraube,' and 'Ozarkblue.' Fruits were harvested at commercial maturity; the treatment was carried out with 1000 µL L-1 of ethylene for 24 h followed by storage at 4 °C under normal atmosphere for 56 days. RESULTS: One day after treatment with ethylene, this increased the proportion of seven (more than 45%) and four (more than 65%) of the nine anthocyanins identified in the Bluecrop and Goldtraube cultivars respectively, and decreased five of the seven anthocyanins identified in 'Ozarkblue'. For 'Bluecrop,' however, this increase reduced until the end of storage but in 'Goldtraube' seven anthocyanins had increased. CONCLUSION: The effect of ethylene on anthocyanin composition of blueberries appeared to depend on the cultivar. 'Bluecrop' and 'Goldtraube' responded positively with an increase in total anthocyanins. © 2018 Society of Chemical Industry.

Effects of chitosan based coatings enriched with procyanidin by-product on quality of fresh blueberries during storage.

The aim of this work was to evaluate the efficacy of an innovative edible coating, based on chitosan from mushrooms enriched with procyanidins extracted from grape seeds, on fresh blueberry quality maintenance, (weight loss, pH, dry matter, colour, firmness and antioxidant activity) and microbial growth, during 14 days of storage at 4 °C. For weight loss, pH and dry matter no relevant differences were detected among the control and the differently coated samples at each considered storage time. Chitosan and chitosan + procyanidins coatings promoted a slight decrease of luminosity and an increase of blue hue colour of blueberry samples during the whole storage period. The use of coating promoted an increase in the antiradical activity that was the highest in blueberries coated with chitosan + procyanidins. Microbiological analysis results indicated that the chitosan-based coated samples had a significantly higher yeast and mould growth inhibition compared to the uncoated sample.

Interactive effects of aluminum and cadmium on phenolic compounds, antioxidant enzyme activity and oxidative stress in blueberry (Vaccinium corymbosum L.) plantlets cultivated in vitro.

To evaluate the potential role of phenolic compounds in Al and Cd stress tolerance mechanisms, Vaccinium corymbosum cv. Legacy plantlets were exposed to different metal concentrations. The present study used an in vitro plant model to test the effects of the following treatments: 100µM Al; 100µMAl + 50µMCd; and 100µMAl + 100µMCd during periods of 7, 14, 21 and 30 days. The oxidative damage was determined by the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2). The antioxidant activity values were determined using 1,1-diphenyl-2-picrylhydrazine (DPPH) and the ferric reducing antioxidant power test (FRAP). Additionally, the phenolic compound concentrations were determined using HPLC-DAD. The exposure to Al and Cd increased the MDA and H2O2 contents differentially, while the antioxidant capacity values showed differences between DPPH and FRAP with the largest changes in FRAP relative to Cd. SOD had the highest activity in the first 7 days, leading to a significant increase in phenolic compounds observed after 14 days, and chlorogenic acid was the major compound identified. Our results revealed that phenolic compounds seem to play an important role in the response to ROS. Therefore, the mechanisms of tolerance to Al and Cd in V. corymbosum will be determined by the type of metal and time of exposure.

Abscisic acid stimulates anthocyanin accumulation in 'Jersey' highbush blueberry fruits during ripening.

Non-climacteric blueberry (Vaccinium spp.) fruits accumulate high levels of anthocyanins during ripening, which are a good source of dietary antioxidants. This study examined the effects of exogenous abscisic acid (ABA) application on fruit characteristics and anthocyanin accumulation in a northern highbush blueberry (V. corymbosum 'Jersey') during development. Fruits on shrubs were treated with 1gL-1 ABA before the initiation of fruit colouration. Application of ABA temporarily increased the level of ABA in the fruits during development. Exogenous ABA had no obvious effect on fruit growth, but stimulated fruit colouration by accelerating the accumulation of individual anthocyanins, mainly malvidin, delphinidin and petunidin glycosides. This is the first report to show that ABA promotes the accumulation of anthocyanins in blueberry fruits. However, exogenous ABA also promoted fruit softening, which is undesirable during harvest and shelf life.

Influence of electro-activated solutions of weak organic acid salts on microbial quality and overall appearance of blueberries during storage.

The aim of this work was to study the potential of diluted electro-activated solutions of weak organic acid salts (potassium acetate, potassium citrate and calcium lactate) to extend the shelf life of blueberries during post-harvest storage. The sanitizing capacity of these solutions was studied against pathogenic bacteria Listeria monocytogenes and E. coli O157:H7 as well as phytopathogenic fungi A. alternata, F. oxysporum and B. cinerea. The results showed that a 5-min treatment of inoculated blueberries with electro-activated solutions resulted in a 4 log CFU/g reduction in Listeria monocytogenes for all solutions. For E. coli O157:H7, the electro-activated potassium acetate and potassium citrate solutions achieved a decrease of 3.5 log CFU/g after 5 min of berry washing. The most important fungus reduction was found when blueberries were washed with an electro-activated solution of potassium acetate and a NaOCl solution. After 5 min of blueberry washing with an electro-activated potassium acetate solution, a very high reduction effect was observed for A. alternata, F. oxysporum and B. cinerea, which showed survival levels of only 2.2 ± 0.16, 0.34 ± 0.15 and 0.21 ± 0.16 log CFU/g, respectively. Regarding the effect of the washing on the organoleptic quality of blueberries, the obtained results showed no negative effect on the product color or textural profile. Finally, this work suggests that washing with electro-activated solutions of weak organic acid salts can be used to enhance the shelf-life of blueberries during post-harvest storage.

Effect of cadmium on phenolic compounds, antioxidant enzyme activity and oxidative stress in blueberry (Vaccinium corymbosum L.) plantlets grown in vitro.

Cadmium (Cd(2+)) can affect plant growth due to its mobility and toxicity. We evaluated the effects of Cd(2+) on the production of phenolic compounds and antioxidant response of Vaccinium corymbosum L. Plantlets were exposed to Cd(2+) at 50 and 100µM for 7, 14 and 21 days. Accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and the antioxidant enzyme SOD was determined. The profile of phenolic compounds was evaluated using LC-MS. The antioxidant activity was measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the ferric reducing antioxidant power test (FRAP). Cd(2+) increased the content of MDA, with the highest increase at 14 days. The presence of Cd(2+) resulted in changes in phenolic compounds. The main phenolic compound found in blueberry plantlets was chlorogenic acid, whose abundance increased with the addition of Cd(2+) to the medium. The changes in the composition of phenolic compounds showed a positive correlation with the antioxidant activity measured using FRAP. Our results suggest that blueberry plantlets produced phenolic compounds with reducing capacity as a selective mechanism triggered by the highest activity of Cd(2+).

Effect of phytosanitary irradiation and methyl bromide fumigation on the physical, sensory, and microbiological quality of blueberries and sweet cherries.

BACKGROUND: The objective of this study was to determine whether irradiation could serve as a suitable phytosanitary treatment alternative to methyl bromide (MB) fumigation for blueberries and sweet cherry and also to determine the effect of phytosanitary irradiation treatment on survival of Salmonella spp. and Listeria monocytogenes on these fruit. 'Bluecrop' blueberries (Vaccinium corymbosum) and 'Sweetheart' cherries (Prunus avium) were irradiated at 0.4 kGy or fumigated with methyl bromide and evaluated for quality attributes during storage. RESULTS: Irradiation caused an immediate decrease in firmness of both fruit without further significant change during storage. Fumigated fruit, in contrast, softened by 11-14% during storage. Irradiation did not adversely affect blueberry and cherry shelf-life. MB fumigation did not impact blueberry and cherry quality attributes initially; however, fumigated fruit exhibited greater damage and mold growth than the control and irradiated samples during storage. Irradiation at 400 Gy resulted in a ∼1 log CFU g(-1) reduction in Salmonella spp. and Listeria monocytogenes counts, indicating that this treatment cannot significantly enhance safety. CONCLUSION: This study indicates that irradiation at a target dose of 0.4 kGy for phytosanitary treatment does not negatively impact blueberry and cherry quality and can serve as an alternative to methyl bromide fumigation. © 2016 Society of Chemical Industry.

Atmospheric cold plasma inactivation of aerobic microorganisms on blueberries and effects on quality attributes.

Cold plasma (CP) is a novel nonthermal technology, potentially useful in food processing settings. Berries were treated with atmospheric CP for 0, 15, 30, 45, 60, 90, or 120 s at a working distance of 7.5 cm with a mixture of 4 cubic feet/minute (cfm) of CP jet and 7 cfm of ambient air. Blueberries were sampled for total aerobic plate count (APC) and yeast/molds immediately after treatment and at 1, 2, and 7 days. Blueberries were also analyzed for compression firmness, surface color, and total anthocyanins immediately after each treatment. All treatments with CP significantly (P < 0.05) reduced APC after exposure, with reductions ranging from 0.8 to 1.6 log CFU/g and 1.5 to 2.0 log CFU/g compared to the control after 1 and 7 days, respectively. Treatments longer than 60s resulted in significant reductions in firmness, although it was demonstrated that collisions between the berries and the container contributed significantly to softening. A significant reduction in anthocyanins was observed after 90 s. The surface color measurements were significantly impacted after 120 s for the L* and a* values and 45 s for the b* values. CP can inactivate microorganisms on blueberries and could be optimized to improve the safety and quality of produce.

Methyl jasmonate affects phenolic metabolism and gene expression in blueberry (Vaccinium corymbosum).

Blueberry (Vaccinium corymbosum) is a fruit very much appreciated by consumers for its antioxidant potential and health-promoting traits. Its beneficial potential properties are mainly due to a high content of anthocyanins and their amount can change after elicitation with methyl jasmonate. The aim of this work is to evaluate the changes in expression of several genes, accumulation of phenolic compounds and alterations in antioxidant potential in two different blueberry cultivars ('Duke' and 'Blueray') in response to methyl jasmonate (0.1 mM). Results showed that 9 h after treatment, the expression of phenylalanine ammonium lyase, chalcone synthase and anthocyanidin synthase genes was stimulated more in the 'Blueray' variety. Among the phenols measured an increase was recorded also for epicatechin and anthocyanin concentrations. 'Duke' is a richer sourche of anthocyanins compared to 'Blueray', treatment with methyl jasmonate promoted in 'Blueray' an increase in pigments as well as in the antioxidant potential, especially in fully ripe berries, but treated 'Duke' berries had greater levels, which were not induced by methyl jasmonate treatment. In conclusion, methyl jasmonate was, in some cases, an effective elicitor of phenolic metabolism and gene expression in blueberry, though with different intensity between cultivars.