Gamma radiation effects on microbiological, physico-chemical and antioxidant properties of Tunisian millet (Pennisetum Glaucum L.R.Br.)

Maximizing the Nutritional Benefits and Prolonging the Shelf Life of Millets through Effective Processing Techniques: A Review

Maximizing the nutritional benefits and extending the shelf life of millets is essential due to their ancient significance, rich nutrient content, and potential health benefits, but challenges such as rapid rancidity in millet-based products underscore the need for effective processing techniques to enhance their preservation and global accessibility. In this comprehensive review, the impact of diverse processes and treatments such as mechanical processing, fermentation, germination, soaking, thermal treatments like microwave processing, infrared heating, radio frequency, nonthermal treatments like ultrasound processing, cold plasma, gamma irradiation, pulsed light processing, and high-pressure processing, on the nutritional value and the stability during storage of various millets has been examined. The review encompasses an exploration of their underlying principles, advantages, and disadvantages. The technologies highlighted in this review have demonstrated their effectiveness in maximizing and extending the shelf life of millet-based products. While traditional processes bring about alterations in nutritional and functional properties, prompting the search for alternatives, novel thermal and nonthermal techniques were identified for microbial decontamination and enzyme inactivation. Advancements in millet processing face challenges including nutrient loss, quality changes, resource intensiveness, consumer perception, environmental impact, standardization issues, regulatory compliance, and limited research on combined methods.

Aflatoxins in Cereals and Cereal-Based Products: Occurrence, Toxicity, Impact on Human Health, and Their Detoxification and Management Strategies

Cereals and cereal-based products are primary sources of nutrition across the world. However, contamination of these foods with aflatoxins (AFs), secondary metabolites produced by several fungal species, has raised serious concerns. AF generation in innate substrates is influenced by several parameters, including the substrate type, fungus species, moisture content, minerals, humidity, temperature, and physical injury to the kernels. Consumption of AF-contaminated cereals and cereal-based products can lead to both acute and chronic health issues related to physical and mental maturity, reproduction, and the nervous system. Therefore, the precise detection methods, detoxification, and management strategies of AFs in cereal and cereal-based products are crucial for food safety as well as consumer health. Hence, this review provides a brief overview of the occurrence, chemical characteristics, biosynthetic processes, health hazards, and detection techniques of AFs, along with a focus on detoxification and management strategies that could be implemented for food safety and security.

Effect of radiation processing on phenolic antioxidants in cereal and legume seeds: A review

Phenolic compounds in cereal and legume seeds show numerous benefits to human health mainly because of their good antioxidant capacity. However, long-term storage and some improper preservation may reduce their antioxidant potential. It is necessary to retain or modify the phenolic antioxidants with improved technology before consumption. Radiation processing is usually applied as a physical method to extend the shelf life and retain the quality of plant produce. However, the effect of radiation processing on phenolic antioxidants in cereal and legume seeds is still not well understood. This review summarizes recent research on the effect of radiation, including ionizing and nonionizing radiation on the content and profile of phenolic compounds, and antioxidant activities in cereal and legume seeds, the influencing factors and possible mechanisms are also discussed. The article will improve the understanding of radiation effect on phenolic antioxidants, and promote the radiation modification of natural phenolic compounds in cereal and legume seeds and other sources.

Aflatoxin reduction in nuts by roasting, irradiation and fumigation: a systematic review and meta-analysis

The present study aimed to investigate the reduction of aflatoxins as a potent hazard for human health in nuts during roasting, irradiation, and fumigation processes. A systematic search was performed in PubMed, Scopus, and ISI Web of Science on 6 April 2020 to find interventional studies assessing the effects of roasting, fumigation, and irradiation methods on total and individual aflatoxins concentration in nuts. Study-specific results were pooled by using a random-effects model. A total of 19 trials were included in the analyses. In most studies, the influence of method on aflatoxin reduction was assessed on peanuts. The results showed that the roasting method significantly reduced aflatoxin B1, B2, G1, and G2 concentrations by 46.91%, 30.66%, 40.88%, and 26.19%, respectively. Such results for the fumigation method were 20.88% and 22.56% for aflatoxin B1 and aflatoxin total, respectively. There was a 58.60% reduction in aflatoxin B1 and a 74.97% reduction in aflatoxin total concentrations in nuts following the irradiation method. The findings indicated that the evaluated processes could be influential for reducing aflatoxin levels in nuts.

Effects of Gamma Irradiation on Ochratoxin A Stability and Cytotoxicity in Methanolic Solutions and Potential Application in Tunisian Millet Samples

Gamma irradiation is a useful technology for degrading mycotoxins. The purpose of this study was to investigate the effect of irradiation on ochratoxin A (OTA) stability under different conditions. OTA was irradiated in methanolic solution and on millet flour at doses of 2 and 4 kGy. Residual OTA concentrations and possible degradation products in irradiated samples were analyzed by high-performance liquid chromatography with fluorescence detection and liquid chromatography coupled to mass spectrometry. The extent of in vitro cytotoxicity of OTA to HepG2 cells, with and without irradiation treatment, was assessed with an MTT assay. OTA was more sensitive to gamma radiation on Tunisian millet flour than in methanolic solutions. After irradiation of naturally contaminated millet flour, the OTA concentration was significantly reduced by 48 and 62% at a dose of 2 and 4 kGy, respectively. However, in the methanolic solution, OTA at concentrations of 1 and 5 μg mL^-1 was relatively stable even at a dose of 4 kGy, with no degradation products detected in the chemical analysis. Analytical results were confirmed by cell culture assays. The remaining cytotoxicity (MTT assay) of OTA following irradiation was not significantly affected compared with the controls. These findings indicate that gamma irradiation could offer a solution for OTA decontamination in the postharvest processing chain of millet flour. However, the associated toxicological hazard of decontaminated food matrices needs more investigation.

Impact of γ-irradiation on physicochemical characteristics, lipoxygenase activity and antioxidant properties of finger millet

In the present study, the finger millet grains were subjected to γ-irradiation at four different dosage levels: 2, 5, 10, and 15 kGy. Effect of γ-irradiation on the proximate composition, pasting properties, lipoxygenase activity, and antioxidant properties of finger millet flour was evaluated. Moisture, protein, fat, ash, and carbohydrate content of native flour was 12.96, 6.85, 2.73, 1.57, and 73.69 g/100 g, respectively. According to the results of proximate analysis, γ-irradiation significantly (p < 0.05) reduced the moisture contents and increased protein contents; however, the fat content of the irradiated flour was equal to or lower than that of the native flour. Pasting properties of the finger millet flour was reduced with the γ-irradiation. Compared with the native flour, lipoxygenase activity and malondialdehyde content decreased and radical scavenging activity, catalase, and superoxide dismutase activities increased in the irradiated flour with increasing γ-irradiation doses. Finally, the present study suggested that the γ-irradiation process improved the antioxidant enzymes and physicochemical characteristics; which could be helpful in formulating tailored made food products.

Aflatoxin in foodstuffs: Occurrence and recent advances in decontamination

Aflatoxins are highly toxic compounds produced as secondary metabolites by some Aspergillus species, whose occurrence have been reported predominantly in several types of foods of low moisture content, while aflatoxin biotransformation products have been reported mainly in milk and milk products. This review deals with the occurrence of aflatoxins in some of the major food products in the last 5 years including regulatory aspects, and recent advances in detoxification strategies for contaminated foods. Aflatoxin contamination in cereals including corn and peanut is still a public health problem for some populations, especially in African countries. Despite that most of physical and chemical methods for aflatoxin detoxification may affect the nutritional properties of food, or are not safe for human consumption, gamma-radiation and ozone applications have demonstrated great potential for detoxification of aflatoxins in some food matrices. Biological methods based on removal or degradation of aflatoxins by bacterial and yeast have good perspectives, although further studies are needed to clarify the detoxification mechanisms by microorganisms and determine practical aspects of the use of these methods in food products, especially their potential effects on sensory characteristics of foods.

Profiling membrane glycerolipids during γ-ray-induced membrane injury

BACKGROUND

γ-rays are high-energy radiation that cause a range of random injuries to plant cells. Most studies on this issue have focused on γ-ray-induced nucleotide damage and the production of reactive oxygen species in cells, so little is known about the glycerolipid metabolism during γ-rays induced membrane injury. Using an ESI-MS/MS-based lipidomic method, we analysed the lipidome changes in wild-type and phospholipase D (PLD)δ- and α1-deficient Arabidopsis after γ-ray treatment. The aim of this study was to investigate the role of PLD-mediated glycerolipid metabolism in γ-ray-induced membrane injury.

RESULTS

The ion leakage of Arabidopsis leaves after 2885-Gy γ-ray treatment was less than 10%. High does γ-ray treatment could induce the accumulation of intracellular reactive oxygen species (ROS). Inhibition of PLDα1 caused severe lipid degradation under γ-ray treatment. γ-ray-induced glycerolipid degradation mostly happened in chloroplastidic lipids, rather than extraplastidic ones. The levels of lysophosphatidylcholine (lysoPC) and lysophosphatidylethanolamine (lysoPE) were maintained in the WS ecotypes during γ-ray treatments, while increased significantly in the Col ecotype treated with 1100 Gy. After 210- and 1100-Gy γ-ray treatments, the level of lysophosphatidylglycerol (lysoPG) decreased significantly in the four genotypes of Arabidopsis.

CONCLUSIONS

γ-ray-induced membrane injury may occur via an indirect mechanism. The degradation of distinct lipids is not synchronous, and that interconversions among lipids can occur. During γ-ray-induced membrane injury, the degradation of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) may be mediated by PLDζ1 or phospholipase A1. The degradation of phosphatidylglycerol was not mediated by PLA, PLDδ or PLDα1, but by phospholipase C or other PLDs. γ-rays can decrease the double-bond index and increase the acyl chain length in membrane lipids, which may make membranes more rigid and further cause injury in membranes.

Gamma irradiation effects on ochratoxin A: Degradation, cytotoxicity and application in food

Ochratoxin A (OTA) is one of the main mycotoxins that can be found in food. The use of gamma radiation is a technique for preserving food that may exert some effects on mycotoxins. OTA was irradiated in its dry form, in aqueous and in methanolic solutions, and in wheat flour, grape juice and wine. Additionally, the toxicity of OTA irradiated in water was tested. In aqueous solutions, more than 90% of the OTA was degraded by γ-radiation doses ≥2.5kGy, and a 2-fold reduction in OTA cytotoxicity was observed. In food matrices, the elimination of OTA by γ-radiation was found more difficult, as radiation doses of 30kGy eliminate at most 24% of the OTA. Higher moisture content of food matrices did not substantially increase OTA elimination. It is concluded that OTA is very sensitive to irradiation in water solutions but resistant in its dry form and in food matrices.

Constitutive hyperactivity of histone deacetylases enhances radioresistance in Lepidopteran Sf9 insect cells

BACKGROUND

Lepidopteran insect cells withstand multifold higher radiation doses and suffer far less DNA damage despite carrying numerous structural/functional homologies with mammalian cells. Since DNA-histone interactions significantly influence radiation-induced DNA damage, we investigated the role of histones in insect cell radioresistance.

METHODS

Modified comet assay was used to assess the γ-radiation-induced DNA damage following serial histone depletion by varied salt concentrations. Acid-Urea-Triton (AUT) gel analysis combined with in silico predictions was used to compare mammalian and insect histones and acetylation status while HDAC activity was assessed/modified for studying the latter's role in radioresistance. Cell death was measured by morphological analysis and flow cytometry.

RESULTS

High-salt extraction pattern from Sf9 nuclei suggested stronger DNA-histone affinity as the two core histones H2A/H2B could be extracted at much higher (2M) concentration as compared to 1.2M NaCl in mammalian (AA8) cells. Electrophoretic mobility of unirradiated Sf9 cells remained unaltered at all salt concentrations (0.14M-2M NaCl), and radiation-induced DNA damage increased only by 2M-NaCl pre-treatment. In silico analysis confirmed excellent conservation of Lepidopteran H2A/H2B sequence with human histones including comparable N-terminal lysine residues, yet these had ~60% lower acetylation. Importantly, insect cells showed ~70% higher histone deacetylase activity whose inhibition by Trichostatin-A reversed hypo-acetylation state and caused significant radiosensitization, thereby confirming the protective contribution of reduced acetylation.

CONCLUSION

Our study reveals that the hypo-acetylated state of well-conserved core histones, maintained by considerable HDAC activity, contributes significantly in Lepidopteran radioresistance.

GENERAL SIGNIFICANCE

This investigation shows constitutively high activity of HDACs as a potential radioprotective mechanism existing in insect cells.

Combined effects of gamma-irradiation and preparation method on antioxidant activity and phenolic composition of Tuberaria lignosa

The preparation method had a higher influence on bioactive properties than the processing treatment, with decoctions being preferable over infusions, as indicated by the higher antioxidant activity and levels of phenolic compounds.