Effect of Nitrogen on Stored-Product Insect Control at Industrial Scale

In this study, we evaluated the insecticidal effect of nitrogen against Sitophilus granarius (L.), Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Prostephanus truncatus (Horn), Tribolium confusum Jacquelin du Val, and Oryzaephilus surinamensis (L.). Four trials were conducted in chambers containing flour in bags or sacks with >99% nitrogen level. Adults of all the above species, as well as immature life stages (eggs, larvae, and pupae) of T. confusum were used in the trials. Our results showed that nitrogen caused high mortality for all species and life stages tested. Some survival was recorded for R. dominica and T. confusum pupae. Low progeny production was recorded for S. granarius, S. oryzae, and R. dominica. In conclusion, our trials indicated that a high nitrogen environment can provide satisfactory control of various primary and secondary stored-product insect species.

Olive Oil Produced from Olives Stored under CO2 Atmosphere: Volatile and Physicochemical Characterization

In this study, an alternative debittering technique for olives, invented and patented by Prof. Vassilis Dourtoglou, was employed. Olive fruits (Olea europaea cv. Megaritiki) were stored under CO₂ atmosphere immediately after harvest for a period of 15 days. After the treatment, a sensory evaluation between the olives stored under CO₂ and those stored under regular atmospheric conditions (control) was performed. Additionally, the CO₂-treated olives were used for the cold press of olive oil production. The volatile profile of the olive oil produced was analyzed using headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to mass spectrometry (GC-MS). A total of thirty different volatile compounds were detected. The volatile characteristics of olive oil are attributed, among others, to aldehydes, alcohols, esters, hydrocarbons, alkanes, and terpenes. The volatile compounds' analysis showed many differences between the two treatments. In order to compare the volatile profile, commercial olive oil was also used (produced from olives from the same olive grove with a conventional process in an industrial olive mill). The antioxidant activity, the content of bioactive compounds (polyphenols, α-tocopherol, carotenoids, and chlorophylls), and the fatty acids' profile were also determined. The results showed that the oil produced from CO₂-treated olives contains different volatile components, which bestow a unique flavor and aroma to the oil. Moreover, this oil was found comparable to extra virgin olive oil, according to its physicochemical characteristics. Finally, the enhanced content in antioxidant compounds (i.e., polyphenols) not only rendered the oil more stable against oxidation but also better for human health. The overall quality of the olive oil was enhanced and, as such, this procedure holds great promise for future developments.

Utilizing low oxygen to mitigate resistance of stored product insects to phosphine

BACKGROUND

Data are provided on the utilization of modified atmospheres, at a commercial scale, against stored product insect populations that are resistant to phosphine. The method is evaluated on different populations of two major stored-product beetle species, Rhyzopertha dominica and Oryzaephilus surinamensis. The trials were carried out in commercial facilities, in which nitrogen was introduced through an embedded nitrogen generator. Each chamber contained three or four pallets of either currants or herbs. A computational model was developed to evaluate the nitrogen concentration.

RESULTS

In most trials, 100% mortality was recorded for both beetle species and all populations, regardless of the temperature and exposure intervals tested. Control progeny production ranged between 20 and 45 adults per vial for R. dominica, and 29 and 27 adults per vial for O. surinamensis. Simulation results reveal that nitrogen can easily penetrate the currants, and its concentration is uniform (differences are below 1.5%) across the pallet. Additionally, the simulation model revealed that lower temperatures do not have an impact on the nitrogen concentration profiles.

CONCLUSIONS

The modified atmosphere applications evaluated here were proved to be effective for all populations, regardless of the level of resistance to phosphine, and any survival could be attributed to the short exposure intervals. Modified atmosphere applications can be effective at a considerably short exposure interval, even at 2.5 days, which is an incontestable advantage for the use of this method against insects, at exposures comparable with those of commercial fumigations. © 2022 Society of Chemical Industry.

Low-oxygen hormetic conditioning improves field performance of sterile insects by inducing beneficial plasticity

As part of sterile insect technique (SIT) programs, irradiation can effectively induce sterility in insects by damaging germline genomic DNA. However, irradiation also induces other off-target side effects that reduce the quality and performance of sterilized males, including the formation of damaging free radicals that can reduce sterile male performance. Thus, treatments that reduce off-target effects of irradiation on male performance while maintaining sterility can improve the feasibility and economy of SIT programs. We previously found that inducing a form of rapid, beneficial plasticity with a 1-hr anoxic-conditioning period (physiological conditioning hormesis) prior to and during irradiation improves male field performance in the laboratory while maintaining sterility in males of the cactus moth, Cactoblastis cactorum. Here, we extend this work by testing the extent to which this beneficial plasticity may improve male field performance and longevity in the field. Based on capture rates after a series of mark release-recapture experiments, we found that anoxia-conditioned irradiated moths were active in the field longer than their irradiated counterparts. In addition, anoxia-conditioned moths were captured in traps that were farther away from the release site than unconditioned moths, suggesting greater dispersal. These data confirmed that beneficial plasticity induced by anoxia hormesis prior to irradiation led to lower postirradiation damage and increased flight performance and recapture duration under field conditions. We recommend greater consideration of beneficial plasticity responses in biological control programs and specifically the implementation of anoxia-conditioning treatments applied prior to irradiation in area-wide integrated pest management programs that use SIT.

Stress Response of Vibrio parahaemolyticus and Listeria monocytogenes Biofilms to Different Modified Atmospheres

The sessile biofilms of Vibrio parahaemolyticus and Listeria monocytogenes have increasingly become a critical threat in seafood safety. This study aimed to evaluate the effects of modified atmospheres on the formation ability of V. parahaemolyticus and L. monocytogenes biofilms. The stress responses of bacterial biofilm formation to modified atmospheres including anaerobiosis (20% carbon dioxide, 80% nitrogen), micro-aerobiosis (20% oxygen, 80% nitrogen), and aerobiosis (60% oxygen, 40% nitrogen) were illuminated by determining the live cells, chemical composition analysis, textural parameter changes, expression of regulatory genes, etc. Results showed that the biofilm formation ability of V. parahaemolyticus was efficiently decreased, supported by the fact that the modified atmospheres significantly reduced the key chemical composition [extracellular DNA (eDNA) and extracellular proteins] of the extracellular polymeric substance (EPS) and negatively altered the textural parameters (biovolume, thickness, and bio-roughness) of biofilms during the physiological conversion from anaerobiosis to aerobiosis, while the modified atmosphere treatment increased the key chemical composition of EPS and the textural parameters of L. monocytogenes biofilms from anaerobiosis to aerobiosis. Meanwhile, the expression of biofilm formation genes (luxS, aphA, mshA, oxyR, and opaR), EPS production genes (cpsA, cpsC, and cpsR), and virulence genes (vopS, vopD1, vcrD1, vopP2β, and vcrD2β) of V. parahaemolyticus was downregulated. For the L. monocytogenes cells, the expression of biofilm formation genes (flgA, flgU, and degU), EPS production genes (Imo2554, Imo2504, inlA, rmlB), and virulence genes (vopS, vopD1, vcrD1, vopP2β, and vcrD2β) was upregulated during the physiological conversion. All these results indicated that the modified atmospheres possessed significantly different regulation on the biofilm formation of Gram-negative V. parahaemolyticus and Gram-positive L. monocytogenes, which will provide a novel insight to unlock the efficient control of Gram-negative and Gram-positive bacteria in modified-atmosphere packaged food.

Primary Metabolism in Fresh Fruits During Storage

The extension of commercial life and the reduction of postharvest losses of perishable fruits is mainly based on storage at low temperatures alone or in combination with modified atmospheres (MAs) and controlled atmospheres (CAs), directed primarily at reducing their overall metabolism thus delaying ripening and senescence. Fruits react to postharvest conditions with desirable changes if appropriate protocols are applied, but otherwise can develop negative and unacceptable traits due to the onset of physiological disorders. Extended cold storage periods and/or inappropriate temperatures can result in development of chilling injuries (CIs). The etiology, incidence, and severity of such symptoms vary even within cultivars of the same species, indicating the genotype significance. Carbohydrates and amino acids have protective/regulating roles in CI development. MA/CA storage protocols involve storage under hypoxic conditions and high carbon dioxide concentrations that can maximize quality over extended storage periods but are also affected by the cultivar, exposure time, and storage temperatures. Pyruvate metabolism is highly reactive to changes in oxygen concentration and is greatly affected by the shift from aerobic to anaerobic metabolism. Ethylene-induced changes in fruits can also have deleterious effects under cold storage and MA/CA conditions, affecting susceptibility to chilling and carbon dioxide injuries. The availability of the inhibitor of ethylene perception 1-methylcyclopropene (1-MCP) has not only resulted in development of a new technology but has also been used to increase understanding of the role of ethylene in ripening of both non-climacteric and climacteric fruits. Temperature, MA/CA, and 1-MCP alter fruit physiology and biochemistry, resulting in compositional changes in carbon- and nitrogen-related metabolisms and compounds. Successful application of these storage technologies to fruits must consider their effects on the metabolism of carbohydrates, organic acids, amino acids and lipids.

Effect of Lemongrass Essential Oil Vapors on Microbial Dynamics and Listeria monocytogenes Survival on Rocket and Melon Stored under Different Packaging Conditions and Temperatures

The aim of the present study was to examine the effect of lemongrass essential oil vapors on the dynamics of surface microbiota and L. monocytogenes growth on rocket and melon under different packaging conditions and storage temperature. For that purpose, rocket and melon were placed on Expanded Polystyrene (EPS) trays, sprayed with L. monocytogenes to a population of 4.5–5.0 log CFU·g⁻¹, packaged using microperforated Oriented Polypropylene (OPP) film in either air or Microperforated Active Modified Atmosphere (MAMA) (initial atmosphere 5% O₂, 10% CO₂) including a Whatman paper containing the essential oil, without contact with the product, and stored at 0, 5, 10, and 15 °C. Application of lemongrass exhibited a bactericidal effect on enterococci and a fungistatic effect on yeast-mould populations but only during air storage of rocket. The former took place at all temperatures and the latter only at 10 and 15 °C. No effect on shelf life of both products was recorded. However, an important effect on the sensorial properties was observed; during the first 4–5 days of storage both products were organoleptically unacceptable. Regarding MAMA packaging, it affected only Pseudomonas spp. population resulting in a reduction of 1–2 log CFU·g⁻¹ in both products.

Effect of Carbon Dioxide on the Growth of Pseudomonas fluorescens and Listeria monocytogenes in Aerobic Atmospheres

The effects of atmospheres containing 20% O₂ and 0 to 80% CO₂ or 30% CO₂ and 0 to 40% O₂ (balance N₂) on the growth rate and lag phase of Listeria monocytogenes and Pseudomonas fluorescens in buffered nutrient broth at 7.5°C were investigated. Increasing CO₂ concentration lengthened the lag phase and decreased the growth rate of both organisms. CO₂ levels above 20% significantly reduced the growth rate of P. fluorescens and CO₂ levels of 80% significantly reduced the growth rate of L. monocytogenes . Linear and multiple regression analyses were used to describe L. monocytogenes and P. fluorescens growth curves. The R² values of all regression analyses were greater than 93%. The regression equations indicate that CO₂ inhibits the growth of both P. fluorescens and L. monocytogenes even in the presence of 20% O₂, However, the effect of CO₂ on P.fluorescens is greater than on L. monocytogenes .

Shelf Life and Toxin Development by Clostridium botulinum during Storage of Modified-Atmosphere- Packaged Fresh Aquacultured Salmon Fillets

Shelf life (onset of sensory spoilage) and the potential for toxin production by Clostridium botulinum type E in retail-type packages of fresh aquacultured salmon fillets packaged in high-barrier film bags under selected atmospheres (100% air, a modified atmosphere containing 75% CO₂:25% N₂, and vacuum) and stored under refrigeration (4°C) and temperature-abuse conditions (8 and 16°C) were investigated. Chemical spoilage indicators (trimethylamine and surface pH) and microbial populations were compared with sensory spoilage characteristics. Storage temperature influenced the time to onset of both sensory spoilage and toxin development in salmon fillets packaged in all atmospheres. The shelf life of fillets packaged in all atmospheres decreased with increase of storage temperature from 4 to 16°C. Trimethylamine content associated with the onset of spoilage for 100% air-packaged fillets increased as storage temperature increased. However, for modified-atmosphere-packaged fillets, the trimethylamine content associated with the onset of spoilage increased as storage temperature decreased from 8 to 4°C. Surface pH was not a good spoilage indicator for modified-atmosphere-packaged fillets. Toxin development preceded sensory spoilage at 16°C storage for fillets packaged in modified atmospheres. Toxin development coincided with sensory spoilage or was slightly delayed for the fillets packaged in all the atmospheres at 8°C storage. At 4°C none of the fillets packaged in either of the atmospheres developed toxin, even 20 days after spoilage as determined by sensory characteristics.

Survival of Campylobacter jejuni Inoculated in Fresh and Frozen Beef Hamburgers stored under Various Temperatures and Atmospheres

The viability of Campylobacter jejuni strains FRI-CF 401S and FRI-CF 25 inoculated in fresh and frozen beef hamburgers was investigated. Hamburgers were stored in the following conditions: 100% air at 4°C for 15 days, 100% CO₂, and 100% N₂ atmospheres at 4°C for 60 days and -18°C for 90 days. The data showed that 100% air was the most toxic atmosphere to C. jejuni strains. The C. jejuni populations decreased significantly faster (P ≤ 0.05) in the inoculated hamburgers in modified atmospheres than in those at -18°C. Fresh or frozen beef hamburgers contaminated by C. jejuni could always be a principal source of human campylobacteriosis.