The synergistic bactericidal effect of simultaneous 222 nm krypton-chlorine excilamp and 307 nm UVB light treatment on sliced cheese and its mechanisms.

In this study, we investigated the combined effect of 222 nm krypton-chlorine excilamp (EX) and 307 nm ultraviolet-B (UVB) light on the inactivation of Salmonella Typhimurium and Listeria monocytogenes on sliced cheese. The data confirmed that simultaneous exposure to EX and UVB irradiation for 80 s reduced S. Typhimurium and L. monocytogenes population by 3.50 and 3.20 log CFU/g, respectively, on sliced cheese. The synergistic cell count reductions in S. Typhimurium and L. monocytogenes in the combined treatment group were 0.88 and 0.59 log units, respectively. The inactivation mechanism underlying the EX and UVB combination treatment was evaluated using fluorescent staining. The combination of EX and UVB light induced the inactivation of reactive oxygen species (ROS) defense enzymes (superoxide dismutase) and synergistic ROS generation, resulting in synergistic lipid peroxidation and destruction of the cell membrane. There were no significant (P > 0.05) differences in the color, texture, or sensory attributes of sliced cheese between the combination treatment and control groups. These results demonstrate that combined treatment with EX and UVB light is a potential alternative strategy for inactivating foodborne pathogens in dairy products without affecting their quality.

Red cabbage extract immobilized in bacterial cellulose film as an eco-friendly sensor to monitor microbial contamination and gamma irradiation of stored cucumbers.

The aim of the present study is to develop a pH-sensing biopolymer film based on the immobilization of red cabbage extract (RCE) within bacterial cellulose (BC) to detect contamination and gamma radiation exposure in cucumbers. The results obtained show a sensitivity to pH changes for RCE in its aqueous form and that incorporated within BC films (RCE-BC), both showed color change correlated to bacterial growth (R2 = 0.91), this was supported with increase in pH values from 2 to 12 (R2 = 0.98). RCE and RCE-BC exposure to gamma radiation (0, 2.5, 5, 10, 15, 20, 25 kGy) resulted in gradual decrease in color that was more evident in RCE aqueous samples. To sense bacterial contamination of cucumbers, the total count was followed at 0, 5, 10 and 15 days in cold storage conditions and was found to reach 9.13 and 5.47 log cfu/mL for non-irradiated and 2 kGy irradiated samples, respectively. The main isolates detected throughout this storage period were identified as Pseudomonas fluorescens, Erwinia sp. Pantoea agglomerans using matrix assisted laser desorption ionization-time of flight-ms (MALDI-TOF-MS). Bacterial growth in stored irradiated cucumbers was detected by color change within 5 and 10 days of storage, after which there was no evident change. This is very useful since contamination within the early days of storage cannot be sensed with the naked eye. This study is the first to highlight utilizing RCE and RCE-BC as eco-friendly pH-sensing indicator films for intelligent food packaging to detect both food contamination and gamma preservation for refrigerator stored cucumbers.

Effect and Mechanism of Eliminating Staphylococcus aureus by Electron Beam Irradiation and Reducing the Toxicity of Its Metabolites.

The purpose of this study was to evaluate the mechanism of sterilization of Staphylococcus aureus by electron beam irradiation (0.5-, 1-, 2-, 4-, and 6-kGy treatments) and whether it reduces the toxicity of its fermentation supernatant. In this study, we investigated the mechanism of sterilization of S. aureus by electron beam irradiation using colony count, membrane potential, intracellular ATP, and UV absorbance measurements; we used hemolytic, cytotoxic, and suckling mouse wound models to verify that electron beam irradiation reduced the toxicity of the S. aureus fermentation supernatant. The results showed that 2 kGy of electron beam irradiation treatment completely inactivated S. aureus in suspension culture, and 4 kGy inactivated cells in S. aureus biofilms. This study suggests that the bactericidal effect of electron beam irradiation on S. aureus may be attributed to reversible damage to the cytoplasmic membrane, resulting in its leakage and the significant degradation of genomic DNA. The combined results of hemolytic, cytotoxic, and suckling mouse wound models demonstrated that the toxicity of S. aureus metabolites was significantly reduced when the electron beam irradiation dose was 4 kGy. In summary, electron beam irradiation has the potential to control S. aureus and reduce its toxic metabolites in food. IMPORTANCE Electron beam irradiation of >1 kGy damaged the cytoplasmic membrane, and reactive oxygen species (ROS) penetrated the cells. Electron beam irradiation of >4 kGy reduces the combined toxicity of virulent proteins produced by Staphylococcus aureus. Electron beam irradiation of >4 kGy can be used to inactivate Staphylococcus aureus and biofilms on milk.

[Detection of Gamma-Ray Irradiation History of Dried Plant-Based Foods via the Analysis of 5,6-Dihydrothymidine].

Irradiation is widely used worldwide to sterilize and kill insects in food, and prevent the germination of agricultural products. However, in Japan, food irradiation is prohibited except to prevent potato sprouting. Herein, 5,6-dihydrothymidine (DHdThd) residue-a damaged nucleoside generated from the thymidine (dThd) residue in DNA contained in food upon irradiation-was used as a detection indicator. Eight dried plant-based food samples were gamma ray-irradiated in the range from 3.2 to 8.3 kGy. Subsequently, DNA was extracted from the irradiated sample and digested into nucleosides by the three enzymes, and the test solution was analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Evidently, in all samples, the concentration ratio of DHdThd to dThd in the test solution (DHdThd/dThd) was dependent on the irradiation dose; moreover, during storage under frozen conditions for at least 890 d post-irradiation, this concentration ratio was equal to that immediately after irradiation. The irradiation histories of the eight types of dried plant-based food samples were correctly detected.

Application of an innovative water-assisted ultraviolet C light technology for the inactivation of microorganisms in tomato processing industries.

We aimed to study the efficacy of a water-assisted UVC light device (WUVC) as an innovative clean technology for the disinfection of fresh sound tomatoes and processing wash water and water turbidity was evaluated as a critical parameter. First, wash waters with different turbidities (from 0.4 to 828 NTU) were inoculated with Listeria innocua and treated in the WUVC device at different dosages. Secondly, fresh tomatoes, inoculated with L. innocua and non-inoculated ones, were treated using the WUVC device containing wash water of different turbidities for different times. The reduction of L. innocua populations on wash water and on the surface of tomato was influenced by turbidity; lower reduction values were observed at higher turbidities. Washing tomatoes with tap water with UVC lamps off (control treatment, TW) decreased L. innocua population on the surface of tomatoes but did not eliminate those bacteria that went into the water. Contrarily, when UVC lights were on, L. innocua population in wash water after treatment significantly decreased, those in clean water being the lowest populations. Reductions of native microbiota on the clean water treated with the highest UV-C radiation dose were lower than those obtained when tomatoes were artificially inoculated. We demonstrated that high reductions of L. innocua population on fresh tomatoes could be achieved using the WUVC system but some drawbacks related to the increase of turbidity should be solved for its implementation in real conditions.

Determination of pepper microbial contamination for low energy e-beam irradiation.

Electrons with energies of 300 keV or lower have the potential to decontaminate the surfaces of various types of food products with minimal loss of quality. The aim of the present work was to determine the thickness of the layer inhabited by microorganisms. The food samples tested were black and white pepper irradiated with 200 keV, 230 keV, 300 keV and 9 MeV beams of electron energy. To determine the depth from the surface which can be inhabited by microorganisms two approaches were tested. The methods used were based on the application of different microbiological recovery techniques and the microbial effectiveness of the irradiation process depending on the energy of the electron beam. It was observed that the layer which microorganisms may contaminate differed for the tested samples it was estimated as being below 100 µm thick for white pepper and about 200 µm for black pepper. The penetration ability was significant in experiments performed, and as a result the electron beam at the lowest levels tested (200 and 230 keV) was found to be insufficient to effectively decontaminate the black pepper samples. The beam of energy 300 keV was found to have a similar microbial inactivation effect as the high energy electron beam (9 MeV).

Microbial radiosensitization using combined treatments of essential oils and irradiation- part B: Comparison between gamma-ray and X-ray at different dose rates.

Stored rice and rice products are prone to contamination by pathogenic fungi and bacteria such as Aspergillus niger, Bacillus cereus, and Paenibacillus amylolyticus. Treatment with antimicrobial essential oils (EOs) and irradiation are options to control spoilage organisms. Microbial samples with or without fumigation with an oregano/thyme EO mixture were irradiated at 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 kGy for calculation of a D10 value. The relative sensitivity was calculated as the ratio of D10 values for the irradiation plus oregano and thyme EO combination and irradiation alone treatments. In all cases, irradiation plus fumigation with the oregano and thyme EO mixture showed increased efficacy compared with irradiation alone. The relative sensitivity of γ-ray irradiation against A. niger was 1.22, 1.33, and 1.24 for radiation dose rates of 10.445, 4.558, and 0.085 kGy/h, respectively, however against B. cereus it was 1.28, 1.45, and 1.49, and against P. amylolyticus it was 1.35, 1.33, and 1.38, for respective γ-ray irradiation dose rates. The relative sensitivity of X-ray irradiation against A. niger, B. cereus, and P. amylolyticus was 1.63, 1.21, and 1.31, respectively, at the X-ray dose rate of 0.76 kGy/h. The results showed that the relative sensitivity of γ-ray irradiation was higher against the two bacteria than the fungus, whereas X-ray showed higher sensitivity against the fungus than the two bacteria. There was no consistent positive or negative relationship between dose rate and relative sensitivity. The results demonstrated the potential of an oregano and thyme EOs mixture as an antimicrobial agent and its efficacy to increase the radiosensitization of A. niger, B. cereus, and P. amylolyticus during γ-ray or X-ray irradiation treatments.

Inactivation of Escherichia coli, Salmonella enterica serovar Typhimurium, and Bacillus cereus in roasted grain powder by radio frequency heating.

AIMS: The objective of this study was to evaluate the antimicrobial effects of radio frequency (RF) heating and the combination treatment of RF heating with ultraviolet (UV) radiation against foodborne pathogens in roasted grain powder (RGP). METHODS AND RESULTS: Foodborne pathogens inoculated on RGP were subjected to RF heating or RF-UV combination treatments. After 120 s of RF heating, 4·68, 3·89 and 4·54 log reductions were observed for Escherichia coli, Salmonella Typhimurium and Bacillus cereus vegetative cells respectively. The combined RF-UV treatment showed synergistic effects of over 1 log unit compared to the sum of individual treatment for E. coli and S. Typhimurium, but not for B. cereus vegetative cells because of their high UV resistance. Germinated B. cereus cells were not significantly inactivated by RF heating (<1 log CFU per gram), and increased heat resistance compared to the vegetative cells was verified with mild heat treatment. The colour of RGP was not significantly affected by the RF or RF-UV treatments. CONCLUSIONS: Applying RF heating to grain-based food products has advantages for the inactivation of E. coli and S. Typhimurium in RGP. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of the present study could be used as a basis for determining the treatment conditions for inactivating E. coli and other foodborne pathogens such as S. Typhimurium and B. cereus in RGP.

Radiosensitivity increase in FCV-F9 virus using combined treatments with natural antimicrobials and γ-irradiation.

AIMS: The objective was to evaluate the possible synergistic effect of cranberry juice (CJ) and commercial citrus extract (BS) against FCV-F9 viral titre in vitro in combination with γ-irradiation and to determinate the D10 values and radiosensitivity increase. METHODS AND RESULTS: Virus samples were treated with a formulation containing a mixture of BS or CJ. Results showed a D10 of 0·05, 0·42% and 1·34 kGy for the virus treated with the BS, the CJ and the irradiation alone respectively. Concentrations needed to reduce 6 log TCID50  ml-1 of viral titre were BS-0·3%, CJ-2·52% and 8·04 kGy. Irradiation combined with BS-0·01% and CJ-0·1% against FCV-F9 virus showed D10 values of 0·74 and 0·72 kGy, respectively, resulting in a viral radiosensitization of 1·28 and 1·50 for respective treatments. CONCLUSION: The higher viral radiosensitization observed after combining γ-irradiation with BS-0·01% and CJ-0·1% indicates that CJ and BS could be used as antiviral agents alone or in combination with γ-irradiation to prevent NoV outbreaks. SIGNIFICANCE AND IMPACT OF THE STUDY: Cranberry juice and BS could be used in hurdle approaches in combined treatment with γ-irradiation to assure food safety without a detrimental effect on nutritional value and maintain low processing cost.

Decontamination of dried whole black peppercorns using ultraviolet-c irradiation.

This study determined the efficacy of UV-C as a decontamination process against some foodborne bacteria in dried whole black peppercorns. Artificially-inoculated Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus were subjected to UV-C with a surface irradiance of 0.43 mW/cm2 and were all found to exhibit a biphasic inactivation pattern with fast log-linear inactivation followed by a tail. Total log reductions (TLR) ranged from 1.92 (S. aureus) to 3.60 log CFU/g (E. coli O157:H7). Increasing the lamp number from 1 to 5 also linearly (R2 = 0.98) increased the surface irradiance from 0.43 to 1.70 and the TLR of the most resistant S. aureus from 1.92 to 2.62 log CFU/g. Quality evaluation showed very small, variable changes in color coordinates, which were not detected by a same/different test involving a 50-member sensory evaluation panel. Mercury deposition was not detected after a maximum exposure time of 90 min to 0.43 and 1.70 mW/cm2. Finally small, non-significant changes in the innate bacterial microflora of the black peppercorns were determined after 90 min-treatment using 1 lamp and 5 lamps, emphasizing the limitation of utility of UV-C as additional decontamination process for post-process-introduced microorganisms. Good Manufacturing Practices throughout the dried black peppercorn manufacturing process were recommended.

Microwave pasteurization of apple juice: Modeling the inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium at 80-90 °C.

Although due to their acidity some fruit juices are considered safe, several outbreaks have been reported. For processing fruit juices, microwave heating offers advantages such as shorter come-up time, faster and uniform heating, and energy efficiency. Thus, it could be a beneficial alternative to conventional pasteurization. The objective of this study was to study the inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium under microwave pasteurization at temperatures between 80 and 90 °C, i.e., at conditions that are employed in conventional pasteurization. Inoculated juices were treated at different power levels (600 W, 720 W) and treatment times (5s, 10s, 15s, 20s, 25s). Time-temperature profiles were obtained by fiber-optic sensors in contact with the samples allowing continuous data collection. The log-logistic and Arrhenius equations were used to account for the influence of the temperature history; thus, resulting in two different modeling approaches that were compared in terms of their prediction abilities. Survival kinetics including non-isothermal conditions were described by a non-linear ordinary differential equation that was numerically solved by the Runge-Kutta method (ode45 in MATLAB ®). The lsqcurvefit function (MATLAB®) was employed to estimate the corresponding survival parameters, which were obtained from freshly made apple juice, whereas the prediction ability of these parameters was evaluated on commercial apple juices. Results indicated that inactivation increased with power level, temperature, and treatment time reaching a microbial reduction up to 7 Log10 cycles. The study is relevant to the food industry because it provides a quantitative tool to predict survival characteristics of pathogens at other non-isothermal processing conditions.

Synergistic bactericidal effect and mechanism of X-ray irradiation and citric acid combination against food-borne pathogens on spinach leaves.

In this study, we investigated the antimicrobial activity of the X-ray irradiation and citric acid (CA) combination against Escherichia coli O157:H7 and Listeria monocytogenes on the surface of spinach leaves and elucidated the mechanisms underlying their synergistic interaction. Upon treatment with 0.3 kGy X-ray irradiation and 1% CA combination, the cell counts of E. coli O157:H7 and L. monocytogenes reduced by 4.23 and 3.69 log CFU/mL on spinach leaves, respectively. The synergistic reduction in the cell counts of E. coli O157:H7 and L. monocytogenes by the combination treatment was 0.95 and 1.14 log units, respectively. The X-ray and CA combination exerts its antimicrobial effect by damaging the bacterial cell membrane and enhancing the generation of intracellular reactive oxygen species in the pathogens. The enhanced bactericidal effect of the combination treatment may not be due to the loss of intracellular enzyme activity. We also evaluated the effect of the combination treatment on the quality attributes of spinach leaves. The combination treatment did not result in adverse changes in color and texture of spinach leaves. These results demonstrate the potential of citric acid and X-ray irradiation combination for decontaminating foodborne pathogens on fresh produce.

Bactericidal and synergistic effects of X-ray irradiation and gallic acid against foodborne pathogens on lettuce.

The objectives of this study were to evaluate the bactericidal effects of X-ray irradiation and gallic acid (GA) against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on lettuce leaves and in phosphate-buffered saline (PBS). Inoculated PBS and lettuce were exposed to X-rays (0.05, 0.1, and 0.15; 0.1, 0.2, and 0.3 kGy, respectively), and GA was applied to lettuce leaves as a solution and in PBS at concentrations of 0.5% (w/v). Combined treatment with 0.3 kGy and 0.5% GA reduced E. coli O157:H7, S. Typhimurium, and L. monocytogenes cell counts 5.41, 2.57, and 1.36 log CFU/cm2 on lettuce, respectively. Combined treatment with 0.15 kGy X-ray and 0.5% GA reduced counts for the same species by 6.54, 4.24, and 1.51 log CFU/mL in PBS. The combined treatments exerted a synergistic antibacterial effect against E. coli O157:H7 on lettuce, but not against S. Typhimurium or L. monocytogenes. In PBS, the synergistic effect was confirmed in both E. coli O157:H7 and S. Typhimurium cells. Mechanistic investigations indicated that the synergistic antibacterial effect was associated with intracellular reactive oxygen species (ROS) generation and bacterial cell membrane damage. Additionally, the X-ray and GA combination treatment did not adversely affect the color, total phenol content, and texture of lettuce. These findings demonstrate that treatment with X-ray radiation and GA can enhance the microbiological safety of fresh produce.

Storage characteristics of infrared radiation stabilized rice bran and its shelf-life evaluation by prediction modeling.

BACKGROUND: Rice bran is a nutrient-dense and resource-rich byproduct produced from the rice milling. The limitation of rice bran utilization is mainly caused by oxidative deterioration. Improvement of stability to prolong rice bran shelf-life has thus become an urgent requirement. RESULTS: The present study aimed to determine the characteristics of infrared radiation heat treatment of rice bran (IRRB) and raw rice bran stored under different temperatures. The effects of heating and storage time on physicochemical, microbial, storage stability and structural properties were investigated. Additionally, the prediction model for the shelf-life of rice bran was established based on free fatty acids and the peroxide value by fitting the curve of bran lipid oxidation. The results obtained demonstrated that infrared radiation heating at 300 °C for 210 s resulted in decreased lipase activity and peroxidase activity of 73.05% and 81.50%, respectively. The free fatty acids and peroxide value of IRRB stored at 4 and 25 °C for 8 weeks were only reached at 2.35% and 3.17% and 2.53 and 3.64 meq kg-1 , respectively. The shelf-life prediction model showed the the shelf-life of infrared radiation-treated samples increased to 71.6 and 25.8 weeks under storage at 4 and 25 °C, respectively. CONCLUSION: The stabilizing process could effectively suppress microbial growth and had no prominent effect on the physicochemical and microstructure properties of rice bran and, simultaneously, storage life was greatly extended. © 2020 Society of Chemical Industry.

Cobalt-60 and electron beam irradiation-induced lipid oxidation in largemouth bass (Micropterus salmoides).

BACKGROUND: Irradiation can cause lipid oxidation of fish. This study aimed to examine the effect of radiation (method, dose and dose rate) on the acid value (AV), peroxide value (PV), thiobarbituric acid reactive substances (TBARS) content and fatty acid profile of fresh and freeze-dried largemouth bass flesh. RESULTS: AV, PV and TBARS presented a dose-dependent increase in fish meat for both cobalt-60 (60 Co) and electron beam (EB) irradiation. With a 6 kGy dose of radiation, all measured indices in the 60 Co group were significantly higher than those in the EB group (P < 0.05 or P < 0.01). With a 3 kGy dose of radiation, AV, PV and TBARS in the 200 Gy min-1 dose rate group were significantly lower than those in the 2 and 80 Gy min-1 groups (P < 0.05). After 60 Co irradiation, AV, PV and TBARS in most fresh samples were significantly higher than those in freeze-dried samples (P < 0.01). And 60 Co irradiation decreased the unsaturated fatty acid (UFA) content in fresh samples and increased the UFA content in freeze-dried samples. Our study indicated that 60 Co irradiation, particularly at a low dose rate, accelerated lipid oxidation in fish meat. A large amount of muscle moisture enhances the amount of UFA loss in fish meat during 60 Co irradiation. CONCLUSIONS: A low dose (3 kGy) of EB irradiation, a high dose rate (200 Gy min-1 ) of 60 Co irradiation or freeze-drying treatment can alleviate the lipid oxidation of largemouth bass meat. © 2020 Society of Chemical Industry.

Increased Resistance of Salmonella enterica Serovar Typhimurium and Escherichia coli O157:H7 to 222-Nanometer Krypton-Chlorine Excilamp Treatment by Acid Adaptation.

In this study, we examined the change in resistance of Salmonella enterica serovar Typhimurium and Escherichia coli O157:H7 to 222-nm krypton-chlorine (KrCl) excilamp treatment as influenced by acid adaptation and identified a mechanism of resistance change. In addition, we measured changes in apple juice quality indicators, such as color, total phenols, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, during treatment. Non-acid-adapted and acid-adapted pathogens were induced by growing the cells in tryptic soy broth without dextrose (TSB w/o D) at pH 7.3 and in TSB w/o D at pH 5.0 (adjusted with HCl), respectively. For the KrCl excilamp treatment, acid-adapted pathogens exhibited significantly (P < 0.05) higher D5d values, which indicate dosages required to achieve a 5-log reduction, than those for non-acid-adapted pathogens in both commercially clarified apple juice and phosphate-buffered saline (PBS), and the pathogens in the juice showed significantly (P < 0.05) higher D5d values than those for pathogens in PBS because of the UV-absorbing characteristics of apple juice. Through mechanism identification, it was found that the generation of lipid peroxidation in the cell membrane, inducing cell membrane destruction, was significantly (P < 0.05) lower in acid-adapted cells than in non-acid-adapted cells for the same amount of reactive oxygen species (ROS) generated at the same dose because the ratio of unsaturated to saturated fatty acids (USFA/SFA) in the cell membrane was significantly (P < 0.05) decreased as a result of acid adaptation. Treated apple juice showed no significant (P > 0.05) difference in quality indicators compared to those of untreated controls during treatment at 1,773 mJ/cm2IMPORTANCE There is a need for novel, mercury-free UV lamp technology to replace germicidal lamps containing harmful mercury, which are routinely utilized for UV pasteurization of apple juice. In addition, consideration of the changes in response to antimicrobial treatments that may occur when pathogens are adapted to the acid in an apple juice matrix is critical to the practical application of this technology. Based on this, an investigation using 222-nm KrCl excilamp technology, an attractive alternative to mercury lamps, was conducted. Our study demonstrated increased resistance to 222-nm KrCl excilamp treatment as pathogens adapted to acids, and this was due to changes in reactivity to ROS with changes in the fatty acid composition of the cell membrane. Despite increased resistance, the 222-nm KrCl excilamp achieved pathogen reductions of 5 log or more at laboratory scale without affecting apple juice quality. These results provide valuable baseline data for application of 222-nm KrCl excilamps in the apple juice industry.

Effect of radio-frequency heating on microbial load, flavor, color, and texture profiles of Cordyceps militaris.

BACKGROUND: Cordyceps militaris is a medicine and food dual-purpose mushroom extensively cultivated and consumed in East and Southeast Asia for centuries. However, it has an extremely short shelf life of 3-4 days at room temperature. C. militaris was pasteurized for 10, 20, and 30 min by radio-frequency (RF) at an electrode gap of 20 mm. The effect of RF heating on the microbial load, color, texture, and flavor attributes of C. militaris was evaluated and compared with those sterilized by conventional high-pressure steam. RESULTS: RF heating contributed to good heating uniformity, uniform temperature distribution, and significant decrease in total microbial load. C. militaris heated by RF exhibited unnoticeable total color difference compared with unpasteurized ones, while those sterilized by high-pressure steam presented undesired and unacceptable browning. Insignificant differences in hardness and chewiness were observed after RF heating. Improvements in mushroom-like flavor occurred after 10 and 20 min of RF heating. CONCLUSION: This study suggests that RF heating for pasteurization of edible mushrooms has promising prospects. Evaluation of RF heating on the taste and nutritional characteristics of edible mushrooms is needed in future work. © 2018 Society of Chemical Industry.

Gamma irradiation of clove: level of trapped radicals and effects on bioactive composition.

BACKGROUND: Food irradiation is a widely used technique for improving the safety and shelf life of foods, including most spices. However, growing concerns by consumers about this technique require further investigation on the effects of radiation, both on the safety of the food and on its organoleptic properties. In this work, cloves of diverse origins were submitted to different irradiation doses in a 60 Co source. The presence of trapped radicals and their time-dependent decay after irradiation were assessed by electron spin resonance (ESR) spectroscopy. The volatile bioactive composition and the clove oil were evaluated before and after irradiation by gas chromatography time-of-flight mass spectrometry. RESULTS: Results show an increase of the amount of volatiles collected after irradiation, especially of caryophyllene oxide and acetic acid, although these are still minor constituents. No new compound was detected after irradiation. Radicals decay fast, and 60 days after irradiation they were undetectable by ESR. CONCLUSION: Gamma irradiation showed to be a clean technique for clove decontamination, since no significant change in the aroma or oil compositions was found, and low levels of trapped paramagnetic species, after the initial decay period, were detected upon irradiation. Furthermore, irradiation doses higher than those legally allowed are equally safe. © 2018 Society of Chemical Industry.

Lipid oxidation stability of ultra-high-temperature short-time sterilization sporoderm-broken pine pollen (UHT-PP) and 60 Co-irradiation sterilization sporoderm-broken pine pollen (60 Co-PP).

BACKGROUND: Pine pollen, a kind of Chinese traditional medicine, is rich in unsaturated fatty acids. During its processing, it is often needed to break the sporoderm in order to increase the availability of some ingredients, which can cause lipid oxidation and the development of rancidity during storage. RESULTS: The primal peroxide value (PV) of ultra-high-temperature short-time sterilization sporoderm-broken pine pollen (UHT-PP) was much higher (over 15 times) than raw pine pollen (R-PP) and 60 Co-irradiation sterilization sporoderm-broken pine pollen (60 Co-PP). The PV of UHT-PP first increased and then decreased shortly after; however, PV of R-PP and 60 Co-PP remained almost unchanged during storage. The volatiles associated with rancidity in UHT-PP were found to be significantly higher than 60 Co-PP, especially hexanal (nearly 30 times) and hexanoic acid (about 2 times), and a multi-organoleptic sensor analyzer (electronic nose system) was able to differentiate these three kinds of samples when the output was subjected to discriminant function analysis. During storage (30 days), hexanal first increased and then decreased (at about 5 days), and hexanoic acid continuously increased for UHT-PP; however, no significant change was noted for R-PP or 60 Co-PP. UHT-PP has a greater surface area than 60 Co-PP, although same sporoderm-broken processes were applied. Antioxidants (flavone, carotenoid and tocopherols, sterol compounds) in 60 Co-PP were significantly (P ≤ 0.05, by Duncan's multiple range test) higher than that in UHT-PP, although not significantly different for total phenolics. CONCLUSIONS: Rancidity occurs more readily in UHT-PP than in R-PP and 60 Co-PP during storage, probably because significant lipid oxidation and antioxidant degradation occurred during the UHT sterilization sporoderm-broken processing of pine pollen. © 2018 Society of Chemical Industry.

Storage stability of soluble pigments, chlorophylls, and carotenoids in electron-beam-irradiated edible lavers (Porphyra umbilicalis) with impact on microbial safety and sensory characteristics.

BACKGROUND: In this study, we investigated whether electron beam (e-beam) irradiation can inactivate microbial populations, including aerobic bacteria plate count, fungi, and coliforms, in two types of lavers (dried and roasted). The impact of e-beam doses of 4 and 7 kGy on microbial populations, color values, total soluble pigments, chlorophylls, and carotenoid content immediately and after storage at 4, 15, 25, and 35 °C for 4, 8, and 12 weeks was also evaluated. RESULTS: The initial microbial load of approximately 106 and 105 CFU g-1 in both dried and roasted lavers was reduced to 104 and 101 CFU g-1 , respectively, after irradiation at 7 kGy. No further proliferation was observed in irradiated dried lavers during 4 weeks of storage at 4 and 15 °C. When stored at low temperature, the shelf-life was extended for up to 12 weeks in 7 kGy irradiated dried and roasted lavers. High amounts of soluble pigments and carotenoids were observed during storage in the 7 kGy irradiated dried laver samples at the end of 12 weeks irrespective of temperature. Although the chlorophyll content decreased under the storage conditions, it was comparatively stable in the 7 kGy-irradiated dried laver. Maximum degradation of color was observed in laver samples subjected to the roasting process. CONCLUSION: Overall, this study indicated that e-beam irradiation of laver at 7 kGy maintains microbial safety as well as quality attributes during storage for up to 12 weeks. Further, dried laver had more essential compounds than roasted laver. © 2019 Society of Chemical Industry.