High-pressure-based hurdle strategy to extend the shelf-life of fresh chicken breast fillets

The combined effects of high hydrostatic pressure (HHP) and a commercial liquid antimicrobial edible coating consisting of lactic and acetic acid, sodium diacetate, pectin and water (“articoat-DLP”) followed by modified atmosphere packaging (MAP) on the shelf-life of chicken breast fillets were evaluated.All samples were held at 4 °C under MAP (30% CO₂/70% N₂) conditions and these were assigned to the following treatments: (i), control untreated fillets (C-MAP); (ii), fillets dipped in articoat-DLP (A-MAP); (iii) HHP (300 MPa) treated fillets followed by MAP (HP-MAP) and (iv) HHP (300 MPa) treated fillets after dipping in articoat-DLP (A-HP-MAP). During storage, packages were tested at intervals for CO₂ and O₂ concentrations, colour (CIE L* a* b*), pH, oxidative stability (TBARS), cooking loss, Warner-Bratzler shear force measurement and sensory analysis (colour, tenderness, juiciness, chicken aroma, oxidised flavour, off-flavours and overall acceptability). Total viable counts and numbers of Pseudomonas, lactic acid bacteria (LAB), Brochothrix thermosphacta, coliforms and Escherichia coli were also determined.The A-HP-MAP combination was the most efficient in extending the durability of chicken breast fillets, which maintained their sensory and microbiological quality for up to 28 days. At the time of rejection, total counts were 6.3 ± 0.7 log cfu/g, with LAB being dominant (100%). For A-MAP and HP-MAP fillets, the storage life was estimated to be two weeks while that of the untreated fillets (C-MAP) was estimated to be one week.Colour, tenderness and overall acceptability were the best maintained sensory attributes during storage for A-HP-MAP samples. The synergistic effect of this high-pressure-based hurdle strategy was higher than those previously reported when applying several combined hurdles to poultry meat.     

Sensory quality and food safety of boneless chicken breast portions thawed rapidly by submersion in hot water

Boneless chicken breast portions were thawed by submersion in hot water (60 °C) and compared to refrigerator thawing. Thawing in hot water was significantly quicker (2–8.5 min) than refrigerator thawing (10–15.5 h). Thawing time in hot water increased with an increase in meat thickness. Sensory panelists could not distinguish a difference between hot water versus refrigerator thawed and subsequently grilled chicken breast portions. A model for Salmonella growth predicts that thawing chicken breast at the slowest rate in this study (0.5 °C/min) would result in a lower increase in the Salmonella concentration than that expected for room temperature storage for 4 h.     

Effects of lactic acid and lauricidin on the survival of Listeria monocytogenes,Salmonella enteritidis and Escherichia coli O157:H7 in chicken breast stored at 4 °C

Lauricidin and lactic acid were evaluated for their effects on growth and survival of Listeria monocytogenes (L55), Salmonella enteritidis (S552) and Escherichia coli O157:H7 (E19) inoculated onto raw chicken breast. Fresh, raw chicken breasts were purchased immediately after slaughter and transported on ice to the laboratory within 20 min. Each chicken breast was decontaminated by briefly dipping in 70% ethanol and passed through a flame of a Bunsen burner and then allowed to cool. The decontaminated Chicken breast was dipped in TSB broth, at room temperature (25 °C) for 15 min, containing approximately log 9 CFU/ml of L. monocytogenes, S. enteritidis or E. coli O157:H7. Initial counts of L. monocytogenes, S. enteritidis or E. coli O157:H7 counts in chicken breast immediately after dipping in TSB broth were in the range of log 7–log 8 CFU/g. After inoculation, the chicken breasts were kept at room temperature for 20 min to allow attachment. Each inoculated chicken breast (25 °C) was dipped in 0 (control – sterile water), 0.5%, 1%, 1.5% or 2% of lauricidin (w/v) or lactic acid (v/v) for 10, 20 or 30 min and then individually placed in oxygen-permeable polyethylene bags. Breasts were subjected to microbiological analyses after treatment (day 0) and after storage for 2, 5, 7, 10 and 14 d at 4 °C. Initial counts of L. monocytogenes, S. enteritidis and E. coli O157:H7, in chicken breast treated with lauricidin decreased by 2.90, 1.31 and 2.27 log CFU/g, respectively. Lauricidin was more effective in reducing L. monocytogenes population than S. enteritidis and E. coli O157:H7 population. Dipping chicken breast in lauricidin for 30 min caused a significant reduction of L. monocytogenes, S. enteritidis and E. coli O157:H7 population compared to 10 and 20 min dipping. Initial L. monocytogenes, S. enteritidis and E. coli O157:H7 counts on chicken breast treated with lactic acid decreased by 1.97, 1.71 and 2.59 log CFU/g, respectively. Lactic acid caused a higher reduction in initial S. enteritidis and E. coli O157:H7 counts compared to lauricidin.     

Efficiency of high pressure treatment on inactivation of pathogenic microorganisms and enzymes in apple,orange, apricot and sour cherry juices

The purpose of this study was to investigate the effect of high hydrostatic pressure with a mild heat treatment on Staphylococcus aureus 485, Escherichia coli O157:H7 933 and Salmonella Enteritidis FDA in apple, orange, apricot and sour cherry juices. The effectiveness of the treatment on polyphenol oxidase activity in apple juice and pectinesterase activity in orange juice were also determined. An inoculum of microorganisms was completely inactivated at 350 MPa and 40 °C in 5 min. The residual polyphenol oxidase activity in apple juice after treatment at 450 MPa and 50 °C for 60 min was obtained as 9 ± 2.2%. The residual pectinesterase activity in orange juice after treatment at 450 MPa and 50 °C for 30 min was determined as approximately 7 ± 1.6%. It compares with 12 ± 0.2% at a treatment of 40 °C and 450 MPa for 60 min. Pressure resistant isoenzymes were thought to be responsible for the final residual activity. The inactivation is irreversible and the enzyme is not reactivated upon storage. High pressure processing constitutes an effective technology to inactivate the enzymes in fruit juices. Pressures higher than 400 MPa can be combined with mild heat (<50 °C) to accelerate enzyme inactivation.     

High hydrostatic pressure treatment applied to model cheeses made from cow’s milk inoculated with Staphylococcus aureus

Pasteurized milk was inoculated with two strains of Staphylococcus aureus (CECT4013 or ATCC13565) and used to elaborate soft-curd cheeses with approximately 7.5-log CFU/g of S. aureus. Cheeses were submitted to 10 min high hydrostatic pressure (HHP) treatments of 300, 400 or 500 MPa at 5 °C or 20 °C. Staphylococcus enterotoxin (SE) was evaluated in cheeses containing ATCC13565. Counts of S. aureus were measured after HHP treatment (day 1) and after 2, 15 and 30 days ripening at 8 °C. Inactivation increased with pressure and storage time, but was similar for both treatment temperatures. Maximum S. aureus reductions were achieved after 30 days ripening for samples treated at 500 MPa and 5 °C: 6.0 ± 0.1 and 4.7 ± 0.5-log CFU/g for CECT4013 and ATCC13565, respectively. However, SE was detected in all cheese samples containing ATCC13565 before and after HHP and after 30 days ripening.     

Inactivation by ozone of Listeria innocua on salmon-trout during cold-smoke processing

This study was conducted to evaluate the efficacy of gaseous ozone exposure on Listeria innocua 2030c growth during cold-smoke processing of Oncorhynchus mykiss (salmon-trout). Three sets of experiments were performed: inoculation with L. innocua 2030c followed by a 20 min ozone exposure were applied to (a) fresh salmon-trout after filleting, (b) to fresh whole fish, and (c) to fresh whole fish after removal of the fish slime. In sets (a) and (b) fillets were subsequently cold-smoked but not in set (c). The ozone concentration inside the exposure chamber after 20 min reached 0.1 × 10⁻³ g/l.Counts of L. innocua 2030c were performed after treatment for sets (a), (b) and (c), after smoking and weekly during 21 days in vacuum packs at 5 °C, for sets (a) and (b). Sampling for total Aerobic Plate Counts (APC) of non-inoculated samples was also performed in set (a). The percentage of salt in the water phase, peroxide values and the effect of treatment on sensory properties of cold-smoked salmon-trout fillets were also determined in the first and second set. In the first set, a decrease of less than 1 log₁₀ in L. innocua numbers occurred on ozone treated samples in all sampling occasions. APC was slightly lower on fresh fillets after treatment and on smoked fillets at 3 weeks of storage at 5 °C (less than 1 log₁₀ CFU/g). In the second set, a reduction greater than 1 log₁₀ L. innocua/g occurred on smoked fillets at the end of the storage period. In the third set, the slime removal resulted in a 1 log₁₀ L. innocua/g reduction on fresh treated samples.Ozone treatment had no significant (p > 0.05) effect on L. innocua counts on samples compared to those on untreated fish. In both sets, no significant differences among ozone treated/untreated samples were noticeable by sensory evaluation (p > 0.05).     

Biogenic amines content,histamine-forming bacteria and adulteration of bonito in tuna candy products

Thirty-four tuna candy products sold in retail markets and supermarkets in Taiwan were purchased and tested to determine the biogenic amine, histamine-forming bacteria, and adulteration of bonito meat. The levels of pH value, water activity (Aw), water content, total volatile basic nitrogen (TVBN), aerobic plate count (APC) and total coliform (TC) in all samples ranged from 5.3 to 6.1, 0.47 to 0.65, 7.37% to 17.32%, 12.1 to 54.6 mg/100 g, <1 to 6.2 log CFU/g and <3 to 1700 MPN/g, respectively. None of these sample contained Escherichia coli. The average content of various biogenic amines in all tested samples was less than 1.0 mg/100 g. Four histamine-producing bacterial strains isolated from tested samples produced 1.02–1.74 ppm of histamine in trypticase soy broth supplemented with 1.0% l-histidine (TSBH) after incubation at 35 °C for 24 h. Assay of multiplex polymerase chain reaction (PCR) revealed that adulteration rate of bonito meat was 26.5% (9/34) in tuna candy samples. Tuna species in tuna candy samples was identified as Thunnus albacares for 29 samples (85.3%), Thunnus alalunga for four samples (11.8%) and Thunnus obesus for one sample (2.9%) by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP).     

A comparison of microbial contamination on sheep/goat carcasses in a modern Indian abattoir and traditional meat shops

The microbial load on sheep/goat carcasses was investigated in Deonar abattoir and traditional meat shops in Mumbai. A total of 96 swab samples from carcass sites were collected and analysed from the abattoir, while 144 swab samples from carcass sites were analysed from three meat shops. These samples were processed for total viable count (TVC) and differential counts. The average TVC after flaying, evisceration and washing in the abattoir was 5.51 ± 0.36, 6.06 ± 0.53 and 5.13 ± 0.58 CFU/cm², respectively. Pooled average TVC in the shops after flaying, evisceration and washing was 5.83 ± 0.42, 6.48 ± 0.27 and 6.17 ± 0.41 log CFU/cm², respectively. Statistical analysis revealed a highly significant difference (P < 0.01) among TVC counts after washing between abattoir and the shops. The highest prevalence of Micrococcus spp. and S. epidermidis was noticed during various operations in both the abattoir and the shops. Although Salmonella spp. could not be isolated from any of the carcass sites in the abattoir, in the shops it showed 16.4% prevalence at all the sites irrespective of operations. Overall study revealed that level of contamination in the traditional meat shops was significantly higher compared to the abattoir. However, the microbial contamination in the abattoir is also high if we compare these results to the reports from developed countries and do not conform to EU specifications. The findings of this study reflect the hygiene status of meat production in the developing world.     

Development and application of molecular markers for poultry meat identification in food chain

Every year, large quantities of poultry and game meat are consumed. Thus, efficient techniques to identify the meat species origin are required which interest traders, consumers and organizations. In this study, two mitochondrial DNA (mtDNA) genes, Cytochrome b (Cyt b) and 12S ribosomal RNA (12S rRNA) were tested as putative discrimination markers in samples of raw and processed poultry meat (chicken, turkey, duck, goose, pheasant, partridge, woodcock, ostrich, quail and song thrush), applying the PCR–RFLP technique with universal primers and ten different restriction enzymes. Digestion of 12S rRNA by AciI successfully distinguished all avian species, producing species-specific patterns. We conclude that the 12S rRNA gene is more informative than Cyt b gene for avian species identification purposes. Moderate process treatment did not prevent the species identification, presenting similar patterns with the raw meat. Finally, this method was considered sufficient to detect mixtures of meat, making it a valuable tool for checking possible adulterations.     

Effects of gamma irradiation and frozen storage on microbial,chemical and sensory quality of chicken meat in Iran

Irradiation is considered one of the most efficient technological processes for the reduction of microorganisms in food. It can be used to improve the safety of food products, and to extend their shelf lives. The aim of this study was to evaluate the effects of gamma irradiation and frozen storage as a combination process for improvement of chicken meat shelf life. Broiler chicken were treated with 0 (non irradiated), 0.75, 3.0, and 5.0 kGy of gamma irradiation and held frozen for 9 months. The control and irradiated samples were stored at −18 °C and underwent microbial analysis, chemical characteristics and sensory evaluation at 3 months intervals. Microbial analysis indicated that irradiation and freezing storage had a significant effect (P < 0.05) on the reduction of microbial loads. There was no significant difference in sensory quality and chemical characteristics during freezing storage in chicken meat. The combination of frozen storage plus irradiation resulted in greater overall reductions on microbial loads, extending shelf-life of chicken meat for commercial application and critical condition.     

Inhibition of Staphylococcus aureus on beef by nisin-containing modified alginate films and beads

Nisin, a bacteriocin, was immobilized into palmitoylated alginate-based films or in activated alginate beads. Sterile beef muscle slices or ground beef were inoculated with Staphylococcus aureus at a level of 10⁴ CFU/g. Sliced beef was then coated with palmitoylated alginate-based films containing 0, 500 or 1000 IU/mL of nisin. Also, ground beef was mixed with 0, 500 or 1000 IU/mL of nisin covalently linked to activated alginate beads in order to evaluate the effect of nisin concentration on S. aureus level. The content of S. aureus in beef was determined during storage at 4 °C. Results demonstrated that after 7 days of storage, a reduction of 0.91 and 1.86 log CFU/cm² was observed on sliced beef covered with film containing 500 or 1000 IU/mL of nisin, respectively. After 14 days of storage, when nisin solution (500 or 1000 IU/g) was mixed with ground beef, 2.2 and 2.81 log CFU/g reductions of S. aureus counts were respectively observed. However, when nisin (500 or 1000 IU/g) was linked into activated alginate beads, 1.77 and 1.93 log CFU/g reductions of S. aureus counts were respectively observed (P ⩽ 0.05). These results suggest that sterile, hydrophobic and biodegradable films or beads incorporating various amounts of nisin could be used efficiently to control the growth of pathogens or microorganisms responsible of spoilage at the surface of round beef or other meat products.     

Survival of Listeria monocytogenes,and enterotoxin-producing Staphylococcus aureus and Staphylococcus pasteuri,during two types of biltong-manufacturing processes

Biltong is a ready-to-eat (RTE) meat product, produced from raw muscle meat by marination, curing and drying. The aim of this study was to determine the survival of three representative bacterial pathogens, (Listeria monocytogenes, Staphylococcus aureus and Staphylococcus pasteuri) throughout the manufacturing process of biltong. Beef portions were surface inoculated with selected isolates and prepared using either a traditional, home-style or modern, manufacturing method prior to drying at 25 °C for 96 h. These two methods differed in their marination process. Samples were taken every 12 h and bacteria enumerated by plate counts. Biltong produced using the modern method was associated with lower counts compared to product produced using the traditional technique. Less than 1 Log CFU/g L. monocytogenes cells were detected in final product and cell counts decreased rapidly throughout both processes. By contrast, 2–4 Log CFU/g cells of Staphylococcus strains survived in the final product. The latter finding may hold future foodborne illness implications, as these strains of Staphylococcus were enterotoxin-producers.     

Effect of high pressure homogenization applied individually or in combination with other mild physical or chemical stresses on Bacillus cereus and Bacillus subtilis spore viability

High pressure homogenization (HPH) has been proposed as an effective alternative to high hydrostatic pressure in the continuous sanitization of fluid food systems. In this study, we evaluated the influence of HPH treatment, applied individually (one, two or three cycles) or in combination with other mild physical or chemical stresses (mild heat treatment H₂O₂ and low pH), on the capability of Bacillus cereus and Bacillus subtilis spore, suspended in sterilized double distilled water, to form colonies. Although plate count only slightly decreased in all the strains when one cycle of HPH at 150 MPa was applied alone, the spores released significant levels of dipicolinic acid (up to 28%) that could indicate a possible disruption of spore layers. Three consecutive cycles of HPH determined high reduction of colony count (about 5 log CFU/ml) and high DPA release (52%). Among the stress conditions applied, it was observed that only the thermal shock after one HPH cycle reduced the colony count of 2.3 log CFU/ml and induced a DPA release up to 57%.These results suggested HPH as a novel application for B. cereus and B. subtilis control in fluid foods.     

Inactivation of Salmonella spp. in ground chicken using high pressure processing

High Pressure Processing (HPP) is a safe and effective process for improving the microbial safety and shelf-life of foods. Salmonella is a common contaminant in poultry meat and is frequently responsible for foodborne illness associated with contaminated poultry meat. In this study the inactivation of a five-isolate cocktail of Salmonella spp. in ground chicken (95% lean) using HPP at refrigeration temperature (4–6 °C) was studied. More than 5-log CFU/g inactivation was achieved at 450 MPa for10 min. In contrast, HPP treatment at 250 MPa or 350 MPa (single-cycle, 15 min) inactivated 0.5 log or 1.7 log CFU/g, respectively. The multiple-cycle HPP mode at 250 or 350 MPa (3-cycle with 5 min/cycle) showed higher cell reduction at 1.3 or 3.3 log CFU/g, respectively. HPP at 550 MPa for 10 min may reduce the cell counts, initially at 8.5 log CFU/g, to below the detection limit (1.0 log CFU/g) in current study. The images (electron microscopy) of the HPP shocked cells were examined for structural damage, which demonstrated that Salmonella cells may still look intact (with damages on rough/irregular surface at 450 MPa stress) under Scanning Electron Microscopy (SEM), but have significant damage internally (voids and uneven mass distribution patterns) under Transmission Electron Microscopy (TEM).     

Application of an optimized 18-h method involving one step culturing and single primer-based PCR assay for detection of Salmonella spp. in foods

A polymerase chain reaction (PCR) using 20-mer oligonucleotide single primer (named primer 3) randomly designed on the basis of Salmonella Typhimurium gatD gene encoding galactitol-1-phosphate dehydrogenase could produce the specific DNA product of approximate 770-bp in all 38 Salmonella strains used. No 770-bp DNA band was amplified from any DNA samples of 20 non-Salmonella bacteria. The DNA band was detected by 1% agarose gel electrophoresis and ethidium bromide staining. The sensitivity of the RAPD–PCR assay for detection of pure genomic DNA from S. Typhimurium ATCC 13311 and Salmonella Enteritidis DMST 15676 was as few as 0.01 ng. When simple boiling in TE buffer for 5 min was used for extraction both Salmonella spp. DNA, the detection limits were at least 230 and 320 cells, respectively. By using the RAPD–PCR assay following at least 14 h pre-enrichment in nutrient broth (NB), as few as 1 CFU of S. Typhimurium ATCC 13311 or S. Enteritidis DMST 15676 per 25 g of autoclaved chicken meat was detected. When the optimized 18-h method involving pre-enrichment in NB and DNA extraction by boiling protocol followed by RAPD–PCR using primer 3 was evaluated in comparison with the conventional method on 195 possibly naturally-contaminated food samples, 36 samples were found positive by both methods. In addition, the results of the developed RAPD–PCR-based assay proved to be identical to those by the conventional method. The optimized 18-h method was simple, rapid and sensitive, achieved the same detection limit as the conventional method and produced a zero level of false-negative results.     

Aqueous extracts of Hibiscus sabdariffa calyces as an antimicrobial rinse on hot dogs against Listeria monocytogenes and methicillin-resistant Staphylococcus aureus

Contamination of ready-to-eat meat products by foodborne pathogens is a major concern in the food industry. Novel methods to control foodborne pathogens are made necessary by continuing outbreaks as well as the development of antibiotic-resistant pathogens. Hibiscus sabdariffa extracts could be useful as a natural source of antimicrobial rinse on ready-to-eat products to control pathogens. In this study, lyophilized Hibiscus flower extracts were examined for their antimicrobial activity as a rinse on all-beef hot dogs against Listeria monocytogenes and methicillin-resistant Staphylococcus aureus (MRSA). Beef hot dogs were dip inoculated in overnight cultures of 1:1 mixtures of L. monocytogenes strains Scott A and 101 or MRSA strains ATCC 33591 and ATCC 33593 and were placed at 4 °C overnight to allow for bacterial attachment. Hot dogs were rinsed with extracts (120, 240 mg/mL) or water (control) for 5, 15, 30, or 60 min and then plated immediately (0 h; no storage) or stored at 4 °C overnight and plated at 24 h. Serial dilutions were plated in duplicate on both TSA and selection media, Modified Oxford (Listeria) or Baird Parker (MRSA), and the entire experiment was replicated 3 times. Higher extract concentrations, longer rinse times, and longer storage times were the most effective at inhibiting and/or killing L. monocytogenes and MRSA on hot dogs. L. monocytogenes was reduced to ca. 1.5 log CFU/g while MRSA was reduced to undetectable levels following rinsing of hot dogs with extracts at 240 mg/mL for 60 min and stored for 24 h. Both L. monocytogenes and MRSA were reduced ca. 2 log CFU/g following rinsing of hot dogs with extracts at 120 mg/mL for 60 min and stored for 24 h. This research demonstrates the effectiveness of Hibiscus extracts against L. monocytogenes and MRSA as an antimicrobial rinse on ready-to-eat meat products.     

Inactivation of Staphylococcus spp. strains in whole milk and orange juice using ultra high pressure homogenisation at inlet temperatures of 6 and 20 °C

The objective of this work was to evaluate the inactivation induced by ultra high pressure homogenisation (UHPH) of Staphylococcus aureus ATCC 13565 and Staphylococcus carnosus CECT 4491 inoculated into milk and orange juice considering the effect of inlet temperature of the sample (6 and 20 °C) on the lethality values and on the production of sublethal injuries. Samples of UHT whole milk and UHT orange juice were inoculated at a concentration of approximately 7.0 log (CFU/ml) and pressurized with a dual valve UHPH machine at 300 MPa at the primary homogenising valve and at 30 MPa on the secondary valve. Viable and injured bacterial counts were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4 °C for milk, and after 3, 6, 9, 12, and 15 days of storage at 4 °C for orange juice. The inlet temperature, the food matrix and the kind of strain influenced significantly (P < 0.05) the lethality level, which was higher for S. aureus in whole milk at an inlet temperature of 20 °C. No sublethal injuries were detected after treatments. The change over time of viable counts for both strains showed a very strong decreasing tendency during the storage at 4 °C for orange juice, while the strain S. carnosus showed a low decreasing tendency and greater resistance when inoculated in milk and pressurized at 6 °C.     

Effects of marinating on the formation of polycyclic aromatic hydrocarbons (benzo[a]pyrene,benzo[b]fluoranthene and fluoranthene) in grilled beef meat

The study was conducted to investigate the effect of marinating on the generation of polycyclic aromatic hydrocarbons (benzo[a]pyrene, benzo[b]fluoranthene and fluoranthene) in grilled beef meat. Seven marinade treatments containing 1) basic marinade, which include sugar, water, onion, turmeric, lemon grass, salt, garlic, coriander and cinnamon, 2) basic–oil, 3) Commercial marinade. 4) basic–oil–lemon juice, 5) basic–lemon juice, 6) basic–oil–tamarind and 7) commercial–tamarind at four time intervals (0, 4, 8 and 12 h) were applied on meat samples before charcoal grilling. Tandem solid-phase extraction (SPE) was used to clean up the samples. A high performance liquid chromatography (HPLC) with fluorescence detector was used for PAHs analysis. The study showed significant (p < 0.05) reduction (70%) of PAH in beef samples treated with the acidic marinade (containing 1.2% lemon juice). The basic–lemon > basic > basic–oil–lemon > basic–oil was the best order of marinade treatment. The duration of marinating was not a significant (p > 0.05) factor in PAH reduction.     

Control of Fusarium moulds and fumonisin B1 in seeds by gamma-irradiation

The distribution of naturally occurring Fusarium moulds producing fumonisin B₁ in seeds was determined. Fusarium infection of seed samples ranged from 10% to 60%, Fusarium moniliforme was the predominant species. Fusarium counts in wheat seeds were 8.1 × 10⁴ CFU/g, 6.3 × 10⁶ CFU/g in maize and 4.8 × 10³ CFU/g in barley. Wheat, maize and barley seeds naturally contaminated with varying levels of fumonisin B₁ 1.4–5.8, 8.0–13.8 and 0.1–0.5 μg/g, respectively. F. moniliforme and Fusarium proliferatum were major Fusarium contaminants producing fumonisin B₁. The effect of gamma irradiation on Fusarium moulds and levels of fumonisin B₁ was also determined. The viable counts of Fusarium in seeds decreased by increasing the radiation dose levels and the growth of Fusarium spp. was inhibited at 4.0 kGy for barley and 6.0 kGy for wheat and maize. Application of radiation dose at 5 kGy inactivated fumonisin B₁ by 96.6%, 87.1% and 100% for wheat, maize and barley, respectively, and a dose of 7 kGy was sufficient for complete destruction of fumonisin B₁ in wheat and maize.     

Use of gamma irradiation for inactivation of pathogens inoculated into Kimbab,steamed rice rolled by dried laver

The effect of gamma irradiation for inactivating the pathogens inoculated into the ready-to-eat Kimbab, steamed rice rolled by dried laver, was investigated. The pathogens used were Salmonella Typhimurium, Escherichia coli, Staphylococcus aureus and Listeria ivanovii which are important for public health. The growth of four test organisms inoculated (about 10⁶–10⁷ CFU/g) into the Kimbab were sustained by an irradiation treatment during 24 h of storage regardless of the temperature at 10, 20 and 30 °C. Four pathogen inoculated into Kimbab decreased 2–3 log CFU/g by 1 kGy treatment and was not detected after 3 kGy. The D₁₀ value of pathogens inoculated into the Kimbab were 0.31–0.44 kGy among the four organisms. This study indicated that a low dose irradiation can maintain microbial safety for ready-to-eat Kimbab, steamed rice rolled by dried laver.