Stored Wheat Grains Research Articles

Identification and control of toxin-producing fungus in wheat grain stores using environment friendly factors

Background: The problem of mycotoxins in wheat crops can lead to health issues for humans and animals. It is very important to find safe and efficient methods to prevent the growth of toxin-producing fungi or reduce and remove them from food to prevent their risks to humans, animals, and agricultural crops. The paper focuses on finding environmentally friendly materials to protect wheat grains from toxin-secreting fungi, particularly Aspergillus niger, reducing the production of aflatoxin B1.Methods: Eight fungal genera were isolated from wheat grain samples, and the most frequent fungus was A. niger. Plant extracts were used to reduce the growth of A. niger, and the culture media was used to test the ability of A. niger fungus isolates to produce aflatoxin toxins. The media was also used to sow wheat grains for the purpose of isolating the fungi associated with them, growing the fungi, and purifying it. The culture media was poured into sterile petri dishes with a diameter of 9 cm, with three replicates for each concentration, and the comparison treatment in which an untreated food media was used. Results: The paper found that A. niger was the frequent fungus among the isolated fungal genera in wheat grain samples. The plant extracts, particularly citrullus extract, showed a clear effect in inhibiting the growth of A. niger and reduced the AFB1 toxin that it produces. The paper recommends continuous examination of stored wheat grains to determine the amount of fungal contamination and to ensure good storage conditions before receiving the grains in grain stores.Conclusion: The paper aimed to detect fungi associated with local and imported wheat grains stored in the stores of Al-Muthanna Governorate and the possibility of reducing them by using some plant extracts. Keywords: Citrullus; Phylex; Aspergillus niger; AFB1

Impact of UV-C irradiation on pests and fungi in stored wheat

The application of UVC radiation in stored wheat grains in Brazil is still very recent and the study of the parameters of this technology in stored products becomes important for the advancement in the scientific as well as technological areas. This is mainly due to the fact that it is a cheap technology that does not leave residues, and can be used to replace chemical pesticides. Thus, the objective of the present work is to evaluate the effect of UV-C radiation on the control of insect pests and fungi in wheat grains. For this purpose, wheat grains containing 20 adult insects of Sitophilus sp were irradiated with UVC light for 15 and 30 minutes at intervals of 15 days for 120 days of storage. At the end of the period, live and dead insects, mass loss and total fungal count were evaluated. Based on the analyses carried out, the use of UV-C Light has been reaffirmed as an effective microbiological control method. On the other hand, the study of its use as a method of biological control, under the conditions of the experiment in which the plant material used were wheat grains with moisture content below 10%, is not feasible since the exposure of wheat grains infested with Sitophilus sp. During the 15 and 30 minute periods, every 15 days there was no statistical difference when compared to the control group.

Potential fungicidal and antiaflatoxigenic effects of cinnamon essential oils on Aspergillus flavus inhabiting the stored wheat grains

Wheat is one of the essential crops for the human and animal nutrition, however, contamination with aflatoxigenic fungi, due to the improper storage conditions and high humidity, was the main global threats. So, preventing the growth of aflatoxigenic fungi in stored wheat grains, by using different essential oils was the main objective of this work. Aspergillus flavus EFBL-MU12 PP087400, EFBL-MU23 PP087401 and EFBL-MU36 PP087403 isolates were the most potent aflatoxins producers inhabiting wheat grains. The effect of storage conditions of wheat grains “humidity, temperature, incubation period, and pH” on growth of A. flavus, was assessed by the response surface methodology using Plackett-Burman design and FCCD. The highest yield of aflatoxins EFBL-MU12 B1 and B2 by A. flavus grown on wheat grains were 145.3 and 7.6 μg/kg, respectively, at incubation temperature 35°C, 16% moisture contents, initial pH 5.0, and incubated for 14 days. The tested oils had a powerful antifungal activity for the growth and aflatoxins production by A. flavus in a concentration-dependent manner. Among these oils, cinnamon oil had the highest fungicidal activity for A. flavus at 0.125%, with about 85-90 % reduction to the aflatoxins B1 and B2, conidial pigmentation and chitin contents on wheat grains. From the SEM analysis, cinnamon oils had the most deleterious effect on A. flavus with morphological aberrations to the conidial heads, vegetative mycelia, alteration in conidiophores identity, hyphae shrank, and winding. To emphasize the effect of the essential oils on the aflatoxins producing potency of A. flavus, the molecular expression of the aflatoxins biosynthetic genes was estimated by RT-qPCR. The molecular expression of nor-1, afLR, pKsA and afLJ genes was suppressed by 94-96%, due to cinnamon oil at 0.062% compared to the control. Conclusively, from the results, cinnamon oils followed by the peppermint oils displayed the most fungicidal activity for the growth and aflatoxins production by A. flavus grown on wheat grains.

Application of Two Ocimum Species Powders in the Control of Red Flour Beetles, Tribolium castaneum Herbst (Coleoptera: Tenebronidae), during Wheat Grain Storage

Pest insects on stored goods are a problem everywhere in the world because they lower grain yields and quality. This has the impact of creating a significant danger to global food security, which could negatively affect people's well-being. In the human endeavor to lessen the threat caused by these insects, the use of synthetic chemical insecticides has unfavorable effects. Recently, there has been advancement in the use of botanicals and agricultural wastes in the control of these pests. This research investigated the effects of Ocimum gratissimum (African basil) and O. basilicum (common basil) powders against Tribolium castaneum infesting wheat grains in storage. Powders were tested singly and mixed at doses of 0.2, 0.4, 0.6, 0.8 and 1.0 g per 20 g of wheat grains. The following parameters were determined: adult mortality, adult emergence rates, seed damage %, weight loss %, and beetle perforation index. The data showed that two Ocimum powders were efficacious and their effectiveness increased with increasing the dosage and also the exposure time. The population of adult T. castaneum on treated wheat grains was significantly (p < 0.05) decreased by the two tested Ocimum species powders. After 24 hours of treatment, 1.0 g of O. basilicum powder caused 50% mortality of adult T. castaneum. However, the combination of O. gratissimum and O. basilicum powders caused 40% of beetles' mortality. On the other hand, O. gratissimum powder was the least toxic on adult T. castaneum with 30% only mortality. The lethal doses of both tested powders and their combination required to cause 50% mortality of the T. castaneum population after the first day of exposure were 1.09, 1.44, and 1.45 g, respectively. While, the lethal dose required to cause 90% mortality (LD90) was 4.24, 8.44, and 5.38 g after the first day post exposure. This study demonstrated the toxicity of O. gratissimum and O. basilicum powders on the survival of T. castaneum on wheat grains. The least deadly dose was recorded on O. gratissimum. Therefore, it is recommended that poor resource farmers and food vendors use Ocimum powder as a biocontrol to manage the red-rust flour beetle in stored wheat grains.

Insecticidal activity of crude olive pomace oils from Kabylia (Algeria) against the infestation of Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) in stored wheat grains

The insecticidal effect of four crude olive pomace oils extracted from pomace collected from four localities of Kabylia, refined olive pomace oil and extra virgin olive oil were assessed under laboratory conditions for the control of adults of Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrychidae)) and Sitophilus oryzae (Linnaeus, 1763) (Coleoptera: Curculionidae). The doses used ranged from 0.1 to 0.4 ml/25 g of durum and soft wheat seeds. In addition, the quality indices and the fatty acid composition of these oils were evaluated. The results show that the legal quality indices were well within the legal limits for crude olive-pomace oil (COP), refined pomace oil (ROP) and extra-virgin olive oil (EVO) categories. The effectiveness of these vegetable oils is highly dependent on the insect species, the dose rate, the exposure time and the type of oil tested The main fatty acids from all samples tested, were oleic (61.89–79.25%), palmitic (8.34–15.71%) and linoleic (8.17–16.52%) acids. For both species and substrates tested, mortality is dose and time of exposure dependent. The highest dose (0.4 ml/25 g) causes ≥ 63.75% mortality, after 24 h of exposure. Comparison of LD50 (ml/25 g) indicates that olive oil was generally more toxic than crude and refined pomace oils, for both insects and substrates, values varies from 0.005 to 0.189. The most sensitive insect was S. oryzae for most vegetable oils tested. Likewise, oils significantly reduced the F1 offspring of both insects and seed weight losses. No progeny were observed in the two pests at the highest dose, and therefore no weight loss was recorded. The results also revealed that the six oils affect the germination capacity of durum and soft wheat seeds when the dosage is increased. The results collected remain encouraging for the recommendation of natural substances as part of integrated pest management programmes against insect pests of stored grains.

Evaluation of Some Grain Protectants and Ozone Gas against Sitophilus Granarius L. In Stored Wheat Grain

Evaluation of Some Grain Protectants and Ozone Gas against Sitophilus Granarius L. In Stored Wheat Grain

EVALUATION OF DIFFERENT STRAINS OF ENTMOPATHOGENIC FUNGI AS POTENTIAL AGENTS FOR THE MANAGEMENT OF TRIBOLIUM CASTANEUM

The global economic significance of wheat (Triticum aestivum) is undeniable, as it serves as a primary food source for 40% of the human population. T. castaneum, a notable economic pest, particularly impacts stored wheat grains and flour. In the pursuit of sustainable pest control, entomopathogenic fungi (EPF) have emerged as advanced microorganisms, providing viable alternatives to harmful synthetic chemical insecticides. This study employed four fungal strains—Beauveria bassiana, Isaria cateniannulata, Trichoderma harzianum, and Metarhizium attenuatum—against mixed adult populations of T. castaneum under controlled laboratory conditions. Different concentrations (1×10², 1×10⁴, 1×10⁶, 1×10⁸, 1×10¹⁰ cfu/ml) for each fungus were employed, and mortality data, LC50, and LT50 were recorded at post-exposure intervals of 4, 6, 8, and 10 days. The application method involved using the fungus through a filter paper dip, and red flour beetle adults were introduced to wheat grains. The highest mortality, observed at the concentration of 1×10¹⁰ cfu/ml, was 80% for both M. attenuatum and B. bassiana. Conversely, the lowest mortality, recorded at the concentration of 1×10² cfu/ml, was 64% for I. cateniannulata, while T. harzianum demonstrated 70% mortality at 1×10¹⁰ cfu/ml. The utilization of entomopathogenic fungi for insect control represents an emerging strategy. B. bassiana and M. attenuatum emerge as promising alternatives for managing T. castaneum in stored grains.

Experimental investigation on storage of food grains using cow dung-based desiccant as preservative

ABSTRACT Food grains, produced abundantly during the harvest season, face the challenge of maintaining their quality for extended periods. While immediate consumption is an option, long-term storage offers distinct advantages by ensuring a continuous food supply beyond the harvest season. Proper storage is a critical post-harvest factor that contributes to various benefits, including economic growth and food security. In this context, this paper presents an experimental study focused on the development and evaluation of a hybrid cow dung-based desiccant (HCDD) as a potential preservative for food grains. The study thoroughly examines the impact of this innovative desiccant, HCDD, on the quality of stored rice and wheat grains. Initially, the lipid content of rice grains in C3 and C4 drums was recorded at 1.97%. However, after 8.5 months of storage, a significant decline in quality was observed in C3, where the lipid content decreased to 1.78%. In contrast, C4 maintained a stable lipid content at 1.89%. Similarly, the initial free fatty acid content in rice grains in both C3 and C4 drums was 1.78%, but after 8.5 months, C3 experienced a significant increase to 7.48%, indicating substantial deterioration. Conversely, C4 exhibited a more modest increase, reaching 4.29% over the same period. Regarding wheat quality, the initial gluten content in C1 and C2 drums was 28.12%. After 5.5 months of storage, C1 exhibited a considerable decline, with gluten content decreasing to 17.62%. In contrast, C2, utilizing HCDD, displayed a milder decrease, reaching 19.1% after 13 months. Furthermore, the initial acid value in C1 and C2 drums for wheat grains was 10.2 mg KOH/g fat. After 5.5 months, C1 experienced a substantial increase in the acid value, rising to 26.8 mg KOH/g fat, indicating grain deterioration. Conversely, C2, benefiting from HCDD, exhibited a less pronounced increase, with an acid value of 15.4 mg KOH/g fat after 13 months. This study meticulously monitored the quality of stored grains by measuring crucial parameters such as lipid content, free fatty acids in rice, gluten, and acid values in wheat. The consistent findings revealed that grains stored with HCDD exhibited superior preservation qualities. They retained lower levels of moisture and experienced significantly slower deterioration rates compared to those stored without HCDD. This not only enhances the shelf life of grains but also ensures their nutritional and qualitative integrity.

Interactions among the composition changes in fungal communities and the main mycotoxins in simulated stored wheat grains.

There are significant food safety risks associated with wheat spoilage due to fungal growth and mycotoxin contamination. Nevertheless, a few studies have examined how stored wheat grain microbial communities and mycotoxins vary in different storage conditions. In this study, changes in deoxynivalenol (DON) and deoxynivalenol-3-glucoside (D3G) content were measured with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and an amplicon sequence analysis of fungi was performed on stored wheat grains from different storage conditions using high-throughput sequencing. The detailed interactions among the composition changes in the fungal community and the DON content of simulated stored wheat grains were also analyzed. Alternaria, Fusarium, Mrakia, and Aspergillus were the core fungal taxa, and the fungal communities of samples stored under different conditions were observed to be different. Aspergillus relative abundances increased, whereas Fusarium decreased. This led to an increase in the content of DON. The content of DON increased about 67% with 12% moisture and at 25 °C after 2 months of storage, which was influenced by the stress response of Fusarium. Correlations in fungal and mycotoxins changes were observed. There may be potential value in these findings for developing control strategies to prevent mildew infestations and mycotoxins contamination during grain storage. In storage, the more the fungal community composition and the relative abundance of Fusarium change, the more mycotoxins will be produced. We should therefore reduce competition between fungal communities through pre-storage treatment and through measures during storage. © 2023 Society of Chemical Industry.

Testing the Efficiency of Silver Nanoparticles Manufactured Locally by the Alga Spirogyra in Inhibiting the Fungus Aspergillus flavus and Reduction of Aflatoxin B1

This experiment was conducted in the mycotoxins lab at the College of Agricultural Engineering Sciences-University of Baghdad with the aim of evaluating the effectiveness of bio- and locally manufactured silver nanoparticles by the alga Spirogyra locally and biologically manufactured silver nanoparticles in inhibiting the fungus Aspergillus flavus and reduction of aflatoxin B1. The results showed the alga Spirogyra highly efficient in the biologically manufactured silver nanoparticles and the size of the synthesized nanoparticles was 8.504 nm when examined by atomic force microscope AFM, which showed a high efficiency in inhibiting the isolate of the fungus Aspergillus flavus at concentrations 1.5, 2 and 3, and the percentage of inhibition was 86.7%, 97.64, 100%, respectively, It also indicated a high efficiency in preventing the fungus from producing aflatoxin B1 on the stored wheat grains. The concentrations of toxins in stored wheat samples were 6.25 ppb, 4.11 ppb and 0.0ppb for concentrations 1.5, 2, and 3 compared with the control treatment in which the concentration of aflatoxin B1 was 88.4ppb, as the percentage of reduction was 92.92%, 95.35% and 100, respectively. The results of biologically manufactured silver nanoparticles also showed an efficiency in reducing aflatoxin B1 from stored wheat grains. The concentration (3) was superior in reducing aflatoxin B1 to 2ppb compared to concentrations of (1.5 and 2), in which the toxin concentration reached 10.25 ppb and 7.15 ppb, respectively, with a reduction percentage of 88.4%, 91.91% and 97.73%.

Monitoring of intergranular variables for predicting technical breakage of wheat grains stored in vertical silos

The increase in the silos temperature and intergranular relative humidity can alter the equilibrium moisture content of the grains mass causing losses. Thus, the objective was to evaluate the temporal monitoring of temperature, relative humidity, and intergranular carbon dioxide for the prediction of dry matter loss in wheat grains stored in vertical silos, using a mathematical model and machine learning algorithms. Under these conditions, wheat grains had a slight increase in metabolic activity, causing a dry matter loss of 0.035–0.041%. The intergranular temperature, relative humidity, and carbon dioxide results were similar to the measurements on the surface of the grain mass. It was concluded that the monitoring of temperature, relative humidity, and the concentration of carbon dioxide in the intergranular air indirectly and early determined the changes in the quality of wheat grains during storage. Although the metabolic activity of wheat grains was low, as the lots remained in hygroscopic equilibrium with moisture contents close to 12% (w.b.), the temporal detection characterized the loss of dry matter and the reduction of grain weight stored. Finally, the Artificial Neural Networks and Multiple Linear Regression model satisfactorily predicted the dry matter loss of stored wheat grain mass.

ASSESSMENT OF QUANTITATIVE LOSSES IN DIFFERENT WHEAT VARIETIES DUE TO RICE WEEVIL (SITOPHILUS ORYZAE L.)

A rapidly rising population and a shift in food preferences away from traditional cereals and towards wheat and wheat products are driving up wheat consumption. Storage pests, particularly Sitophilus oryzae, is one of the important insect pest, damages stored wheat grains, degrading the quality and quantity of the commodities by diminishing nutrition content and rendering them unfit for human use. To overcome such problems a study was undertaken to assess the quantitative losses caused by rice weevil in different wheat varieties during different storage periods so that to choose most resistant variety. This study was undertaken during 2018-2019 under laboratory conditions, different wheat varieties viz, VL 907, RSP 561, WH 1080, HD 3086, WH1105 were assessed for quantitative losses caused by rice weevil Sitophilus oryzae. The assessed parameters were adult emergence, per cent seed damage, per cent weight loss and per cent avoidable losses. Our investigation revealed that among the wheat varieties WH 1080 was found least susceptible with minimum number of progeny emergence (21.9), least seed damage (5.77%) and weight loss (1.50%) up to six months of storage period while as RSP 561 was highly susceptible with maximum number of progeny emergence (94.6), highest seed damage (69.3 %) and weight loss (23.6 %).

Influence of ozone treatment on wheat (Triticumaestivum) germination during bulk storage

The currentexperiment was conductedto understandgaseous ozone exposure time and cycle effect on wheat seed germination during storage. The bulk storage of wheat grain hasa major issue of insects and pests which is controlled by gaseous ozone treatment in closed storage system. Ozone is the acceptable and economically viable technique for treating grains during storage for its residue-free and environment-friendly nature. In this research article, the ozone gas treatment givento the wheat grain during bulk storage and evaluated its influence on seed germination.A pilot-scale ozone disinfestation system for wheat grains was developed. The two-factorial experimental design on the influence of the parameters of the technological process of ozone treatment on the germination qualities of wheat seeds was carried out. Wheat grains were treated by gaseous ozone with various time durations (0 min, 30 min, 60 min, 90 min and 120 min) and at various frequency cycles (7 days, 14 days, 21 days). The experiment has recorded observation on the effect of ozone treatment time and the ozone frequency cycle on the germination percentage of wheat grain.The data demonstrated that ozone used in bulk storage enhances seed germination percentage. On the other hand, excess ozone can also cause some negative effects on germination. This study provided new insights into how stored wheat grain responds to ozone treatment and highlighted the impact of treatment time durations and frequency cycle for seed germination.

Efficacy of the Plant Extracts as Grain Protectants against Rice Weevil Sitophilus oryzae on Stored Wheat Grains

The present investigation were conducted at department of Entomology SHUATS, Prayagraj during 2021-2022 using completely randomized design with three replications and treatments neem leaf powder, turmeric rhizome powder, clove powder, pepper powder, mustard oil, soybean oil and groundnut oil. Among the selected oils and botanicals treated to wheat grains, mustard oil and soybean oil were found to be highly effective in increasing adult mortality (100 %) and reducing the per cent weight loss (0.00%) in stored wheat grains. Turmeric rhizome powder was found to be least effective among all the treatments. The maximum germination percentage, vigour index 1 and vigour index 2 was observed in grains treated with mustard oil (90%, 2250.00, 123.00) respectively on wheat grains. Turmeric rhizome powder was found to be least effective among all the treatments.

Nano-formulation of Pelargonium graveolens Essential Oil: Physicochemical Characterization and its Bioactivity Against Rice Weevil Sitophilus Oryzae on Stored Wheat Grain

Nano-formulation of Pelargonium graveolens Essential Oil: Physicochemical Characterization and its Bioactivity Against Rice Weevil Sitophilus Oryzae on Stored Wheat Grain

Detection of Aspergillus flavus in Wheat Grains Using Anti-mannoprotein (MP1) and Spore Protein Polyclonal Antibodies

Cell wall mannoprotein (MP1) gene of an aflatoxigenic strain of Aspergillus flavus, isolated from stored wheat grains, was cloned and sequenced. MP1 protein was expressed in E. coli in soluble form and purified. Polyclonal antibodies were raised against recombinant MP1 protein and inactivated spores of this fungus in rabbit and purified by ammonium sulphate precipitation, Protein A sepharose and antigen affinity chromatography. The minimum concentration of purified mycelial or spore proteins that could be detected by ELISA was determined as 100ng using 2µg of these antibodies. The anti-MP1 antibody was found more sensitive than anti-spore protein antibody. Western blot and immunofluorescence analysis showed reactivity of these antibodies to various proteins (30 to 200kDa) distributed throughout the surface of mycelia and spore of A. flavus. Cross-reactivity of these antibodies was detected with fungi belonging to different Aspergillus, Rhizopus and Alternaria species out of fourteen different fungal species tested. In fungal contaminated wheat grains, these antibodies could detect presence of as low as 1µg mycelia or 103 spores per gram of wheat grains using ELISA. The results suggest that the developed antibodies could be successfully applied for the detection of predominant fungal infestation in stored wheat grains.

Eco-Friendly Tools for Early Detection of Insects in The Stored Wheat Grains Under Egyptian Conditions

Eco-Friendly Tools for Early Detection of Insects in The Stored Wheat Grains Under Egyptian Conditions

POST HARVEST TREATMENT OF PEST AFFECTING WHEAT GRAIN USING SOME SPICES (Pipernigrum, Zingiber Officinale AND Ellectaria cardamom).

The study was conducted in the Laboratory of Plant Science and Biotechnology Department, Federal University of Lafia, Nasarawa State to investigate the insecticidal potency of three spices powder namely black pepper (Piper nigrum L.), ginger (Zingiber officinale L.), and true green (Ellectaria cardamom L.), against wheat weevil (Tribolium castaneum) on stored wheat grain. Spices powder was added separately to 20g of wheat grain in plastic containers at four dosages 0.15, 0.27, 0.37, and 0.5% (w/w) while control had no spices powder. Twenty insect pests (Tribolium castaneum) were introduced into each container. Mortality counted in each treatment was recorded after 7, 14, 21, 28 and 35 days. All treatments were replicated three times. Variations were significantly observed in the overall effect of different plant powders on the mortality of weevils extracted from wheat kernel. Weevils treated with Piper nigrum powder exhibited the highest mean mortality (16.37), followed by Ellectaria cardamom (16.05) and lastly Zingiber officinale (13.82). from the result obtained, it is evident that the spice powders possessed insecticidal properties which if fully extracted could be used in post harvest treatment of wheat grain on storage

Analysis of Stored Wheat Grain-Associated Microbiota Reveals Biocontrol Activity among Microorganisms against Mycotoxigenic Fungi.

Wheat grains are colonized by complex microbial communities that have the potential to affect seed quality and susceptibility to disease. Some of the beneficial microbes in these communities have been shown to protect plants against pathogens through antagonism. We evaluated the role of the microbiome in seed health: in particular, against mycotoxin-producing fungi. Amplicon sequencing was used to characterize the seed microbiome and determine if epiphytes and endophytes differ in their fungal and bacterial diversity and community composition. We then isolated culturable fungal and bacterial species and evaluated their antagonistic activity against mycotoxigenic fungi. The most prevalent taxa were found to be shared between the epiphytic and endophytic microbiota of stored wheat seeds. Among the isolated bacteria, Bacillus strains exhibited strong antagonistic properties against fungal pathogens with noteworthy fungal load reduction in wheat grain samples of up to a 3.59 log10 CFU/g compared to untreated controls. We also found that a strain of the yeast, Rhodotorula glutinis, isolated from wheat grains, degrades and/or metabolizes aflatoxin B1, one of the most dangerous mycotoxins that negatively affects physiological processes in animals and humans. The mycotoxin level in grain samples was significantly reduced up to 65% in the presence of the yeast strain, compared to the untreated control. Our study demonstrates that stored wheat grains are a rich source of bacterial and yeast antagonists with strong inhibitory and biodegradation potential against mycotoxigenic fungi and the mycotoxins they produce, respectively. Utilization of these antagonistic microorganisms may help reduce fungal and mycotoxin contamination, and potentially replace traditionally used synthetic chemicals.

A new green insecticide for stored wheat grains: Efficiency against Rhyzopertha dominica and risk assessment

This work evidenced the insecticidal activity of encapsulated Mentha spicata essential oil (EO) against Rhyzopertha dominica in presence of stored wheat grain and evaluated the residual EO amount in wheat grains after treatment. EO distribution in the different fractions recovered after grain milling was also determined. The mortality rate against R. dominica reached more than 90% and was dependent on the amount of EO released from the encapsulation matrix. The quantification of the two major compounds of EO, (R)-limonene and (R)-carvone, showed that wheat grains contained different amount depending on the storage conditions. When wheat grains were stored in open jars, the EO residual amount in grains was especially low (1.98 mg/kg) compared to amount in closed jar (51.6 mg/kg). The flour resulting from milling contained lower amount of EO compounds in comparison with the bran fractions. The contact of wheat grains with EO clearly modified the native aromatic profile of the wheat flour as the most represented compounds were those belonging to the EO. In the native flour, ten volatile compounds, mainly alcohols and aldehydes due to oxidation of lipids were identified, which represented only 14% of the aromatic profile when the wheat grains were treated by EO. However, when the storage condition of grains mimics the silos conditions, the level of (R)-carvone, the major component of spearmint EO is found around 3 mg/kg of flour which was far below its currently use in bakery products.