Changes in growth and antioxidant status of alfalfa sprouts during sprouting as affected by gamma irradiation of seeds.

Viking 3000 alfalfa seeds irradiated with gamma rays to doses of 0, 1, 2, 3, or 4 kGy were sprouted and allowed to grow for up to 8 days at 23 degrees C. Germination, growth (yield and length), antioxidant capacity, and ascorbic acid (AA) were measured during sprouting. Results showed percent germination of the seeds and the rates of growth of the sprouts were inversely related to the radiation dose absorbed by the seeds. Both antioxidant capacity and AA content expressed on a fresh weight basis decreased during growth of the sprouts. Sprouts grown from irradiated seeds had greater antioxidant capacity and AA content on a fresh weight basis than those grown from nonirradiated seeds. However, when the nutritive values were expressed on a per gram of seed basis, irradiation had no effect on the nutritive values of sprouts.

Irradiation D-values for Escherichia coli O157:H7 and Salmonella sp. on inoculated broccoli seeds and effects of irradiation on broccoli sprout keeping quality and seed viability.

Like alfalfa sprouts, broccoli sprouts can be a vehicle for bacterial pathogens, which can cause illness when they are consumed. The gamma irradiation process was used to reduce numbers of bacterial pathogens on broccoli sprouts and seeds, and the effect of this process on the seeds was studied. The irradiation destruct values for Salmonella sp. and for strains of Escherichia coli O157:H7 inoculated on broccoli seeds were determined. Results obtained in this study indicate that a dose of 2 kGy reduced total background counts for broccoli sprouts from 10(6) to 10(7) CFU/g to 10(4) to 10(5) CFU/g and increased the shelf life of the sprouts by 10 days. Yield ratio (wt/wt), germination percentage, sprout length, and thickness were measured to determine the effects of various irradiation doses on the broccoli seeds. Results show a decreased germination percentage at a dose level of 4 kGy, whereas the yield ratio (wt/wt), sprout length, and thickness decreased at the 2-kGy dose level. The radiation doses required to inactivate Salmonella sp. and strains of E. coli O157:H7 were higher than previously reported values. D-values, dose required for a 1-log reduction, for the nonvegetable and vegetable Salmonella sp. isolates were 0.74 and 1.10 kGy, respectively. The values for the nonvegetable and vegetable isolated strains of Escherichia coli O157:H7 were 1.43 and 1.11 kGy, respectively. With the irradiation process, a dose of up to 2 kGy can extend the shelf life of broccoli sprouts. A dose of > 2 kGy would have an adverse effect on the broccoli seed and decrease the yield of broccoli sprouts.

Inactivation of Escherichia coli O157:H7 and Salmonella by gamma irradiation of alfalfa seed intended for production of food sprouts.

Inonizing irradiation was determined to be a suitable method for the inactivation of Salmonella and Escherichia coli O157:H7 on alfalfa seed to be used in the production of food sprouts. The radiation D (dose resulting in a 90% reduction of viable CFU) values for the inactivation of Salmonella and E. coli O157:H7 on alfalfa seeds were higher than the D-values for their inactivation on meat or poultry. The average D-value for the inactivation of Salmonella on alfalfa seeds was 0.97 +/- 0.03 kGy; the D-values for cocktails of meat isolates and for vegetable-associated isolates were not significantly different. The D-values for nonoutbreak and outbreak isolates of E. coli O157:H7 on alfalfa seeds were 0.55 +/- 0.01 and 0.60 +/- 0.01 kGy, respectively. It was determined that the relatively high D-values were not due to the low moisture content or the low water activity of the seed. The D-values for Salmonella on alfalfa seeds from two different sources did not differ significantly, even though there were significant differences in seed size and water activity. The increased moisture content of the seed after artificial inoculation did not significantly alter the D-value for the inactivation of Salmonella. The results of this study demonstrate that 3.3- and 2-log inactivations can be achieved with a 2-kGy dose of ionizing radiation, which will permit satisfactory commercial yields of sprouts from alfalfa seed contaminated with E. coli O157:H7 and Salmonella, respectively.

Changes in structure and color characteristics of irradiated chicken breasts as a function of dosage and storage time.

Structural change and color characteristics of chicken breasts as a function of irradiation dose and subsequent storage process were investigated by visible spectroscopy and HunterLab measurement. Ratios of R(1)=A(485 nm)/A(560 nm) and R(2)=A(635 nm)/A(560 nm,) which are related to absorbances of the visible bands at 485 nm (metmyoglobin), 560 nm (oxymyoglobin), and 635 nm (sulfmyoglobin), suggested that relative amount of oxymyoglobin either increases as a result of irradiation, or decreases with the storage process. The plot of R(1) and R(2) versus storage time showed that the increments of both R(1) and R(2) are dose-dependent and that the relative amount of oxymyoglobin species in irradiated meats begins to decompose 7-12 days later than raw meats. In addition, R(1) and R(2) values were correlated with color index E(∗) of chicken breasts.

Volatile sulfur compounds in irradiated precooked turkey breast analyzed with pulsed flame photometric detection.

Ionizing radiation is an effective processing technology for pathogen inactivation on various foods. However, the generation of off-odor is a concern for some irradiated meats. This study was conducted to investigate volatile sulfur compounds of precooked ready-to-eat turkey breast as functions of radiation dose and subsequent storage. Precooked turkey breast was exposed to 0, 1, 2, 3, 4, and 5 kGy of gamma radiation and stored for 14 days at 5 degrees C. Volatile sulfur compounds were extracted using solid phase microextraction (SPME), followed by gas chromatographic separation and pulsed flame photometric detection. Irradiation dramatically increased concentrations of hydrogen sulfide, sulfur dioxide, methanethiol, and dimethyl disulfide. The rate of increase was higher at low doses (0-2 kGy) than at higher doses of 3-5 kGy. Carbon disulfide was the only volatile sulfur compound that was reduced by irradiation. Concentrations of all volatile sulfur compounds decreased in both irradiated and nonirradiated samples stored at 5 degrees C.

gamma-Radiation influences browning, antioxidant activity, and malondialdehyde level of apple juice.

Apple juice was gamma-irradiated at 5 degrees C at doses ranging from 0 to 8.9 kGy and then stored at 5 degrees C for 15 days. Ionizing radiation reduced the browning of apple juice and increased antioxidant activity measured by the ferric-reducing antioxidant power (FRAP) assay. The magnitude of changes increased with radiation dose. The level of malondialdehyde (MDA) measured using the thiobarbituric acid reactive substrates assay increased at radiation doses above 2.67 kGy. The browning of irradiated juices increased during storage at 5 degrees C, but the irradiated juices were still lighter than controls at the end of storage. Differences in FRAP values disappeared during early periods of storage while higher MDA levels were observed in irradiated samples during most of the storage period. Elimination of suspended matter from apple juice did not alter irradiation-induced changes in browning, FRAP, or MDA formation. As compared to irradiation conducted at 5 and 20 degrees C, treatment at -15 degrees C was less effective in reducing browning and in increasing MDA formation but elevated FRAP values. The exclusion of oxygen from juices did not affect the reduction in browning due to irradiation but promoted the increase in FRAP values and decreased the irradiation-induced MDA formation.

Elimination by Gamma Irradiation of Salmonella spp. and Strains of Staphylococcus aureus Inoculated in Bison, Ostrich, Alligator, and Caiman Meat †.

There is an expanding industry for the marketing of high-value meats from animals other than the typical domesticated species, including, but not limited to, bison, ostrich, alligator, and caiman. In this study we compared the gamma radiation resistance of a mixture of salmonellae ( Salmonella dublin , S. enteritidis , S. newport , S. senftenberg , and S. typhimurium ) and a mixture of Staphylococcus aureus strains (ATCC 13565, ATCC 25923, and B124) when present on ground bison, ostrich, alligator, and caiman meats at 5°C. A minimum of five doses were used to establish the D values, and the studies were replicated three times. Because the type of meat did not significantly (P < 0.05) alter the radiation resistance of salmonellae and of S. aureus only slightly in the case of ostrich meat, all of the results for each organism were combined to obtain radiation D values of 0.53 ± 0.02 and 0.37 ± 0.01 kGy for Salmonella spp. and S. aureus , respectively. The authors conclude that both of these food-borne pathogens, if present, can be eliminated or greatly reduced in number, depending upon the level of contamination, from these meats by gamma radiation doses between 1.5 and 3.0 kGy at 5°C, the doses currently approved by the FDA and USDA for the irradiation of poultry. The authors also conclude that similar, if not identical, control of food-borne pathogens should be expected on edible meats in general, not just on those that are generically related.

Effects of NaCl, Sucrose, and Water Content on the Survival of Salmonella typhimurium on Irradiated Pork and Chicken.

We investigated the effects of water content, activity, sodium chloride (NaCl) and sucrose contents on the survival of Salmonella typhimurium ATCC 14028 in irradiated mechanically deboned chicken meat (MDCM) and ground pork loin. The effects of NaCl and sucrose concentration were investigated by adding various amounts to MDCM or ground pork loin, or by rehydrating freeze-dried ground pork loin with NaCl solutions with various degrees of saturation. The effects of water content were investigated by rehydrating freeze-dried ground pork loin with different quantities of water. Inoculated samples were irradiated at 5°C in vacuo to various doses up to 6.0 kGy. Highly significant effects (p < 0.01) of water content, water activity (aw) and NaCl content, but not of sucrose content, on the survival of S. typhimurium were identified. The failure of sucrose to provide the same protection for S. typhimurium in meat against radiation argues against reduced water activity being a primary mechanism of protection. The results indicate that the survival of foodborne pathogens on irradiated meats with reduced water content or increased NaCl levels may be greater than expected.

Effects of Ionizing Radiation and Anaerobic Refrigerated Storage on Indigenous Microflora, Salmonella , and Clostridium botulinum Types A and B in Vacuum-Canned, Mechanically Deboned Chicken Meat †.

Vacuum-canned, commercial, mechanically deboned chicken meat was challenged with either Clostridium botulinum spores (20 strains of types A and B, proteolytic; final spore concentration of ca. 400/g of meat) or Salmonella enteritidis (ca. 104 CFU/g of meat) followed by irradiation to 0, 1.5, and 3.0 kGy and storage at 5°C for 0, 2, and 4 weeks. None of the samples stored at 5°C developed botulinal toxin; however, when these samples were temperature abused at 28°C they became toxic within 18 h and had obvious signs of spoilage, i.e., swelling of the can and a putrid odor. During 4 weeks of refrigerated storage the log10 of the population of S. enteritidis in nonirradiated samples decreased from 3.86 to 2.58. S. enteritidis CFU were detectable in samples irradiated to 1.5 kGy at 0 weeks but not in samples irradiated to 3.0 kGy. Log levels of aerobic and facultative mesophiles increased during 4 weeks of refrigerated storage from 6.54 to 8.25, 4.03 to 8.14, and 2.84 to 5.23 in samples irradiated to 0, 1.5, and 3.0 kGy, respectively. Based on taxonomic analyses of 245 isolates, the bacterial populations depended upon radiation dose and storage time. The change was predominantly from gram-negative rods in nonirradiated samples to gram-positive streptococci in samples irradiated to 3.0 kGy and stored for 4 weeks. Spoilage organisms survived even the 3.0 kGy treatment.

Control of Enterotoxic Bacillus cereus on Poultry or Red Meats and in Beef Gravy by Gamma Irradiation.

The gamma-radiation resistance of five enterotoxic and one emetic isolate of Bacillus cereus vegetative cells and endospores was tested in mechanically deboned chicken meat (MDCM), ground turkey breast, ground beef round, ground pork loin and beef gravy. The D10 values for B. cereus ATCC 33018 were 0.184, 0.431 and 2.56 kGy for logarithmic-phase cells, stationary-phase cells, and endospores at 5°C on MDCM, respectively. Neither the presence nor absence of air during irradiation significantly affected radiation resistance of vegetative cells or endospores of B. cereus ATCC 33018 when present on MDCM. Irradiation temperature (-20 to +20°C) did affect the radiation resistance of stationary-phase vegetative cells and to a limited extent that of spores on MDCM. Impedance studies indicated that surviving vegetative cells were severely injured by radiation. A dose of 7.5 kGy at 5°C was required to eliminate a challenge of 4.6 × 103 B. cereus ATCC 33018 from temperature-abused MDCM (24 h at 30°C). The radiation resistance of a mixture of endospores of six strains to gamma radiation was 2.78 kGy in ground beef round, ground pork loin and beef gravy, but 1.91 kGy in turkey and MDCM. The results indicate that irradiation of meat or poultry can provide significant protection from vegetative cells but not from endospores of B. cereus .

Extending Shelf Life of Poultry and Red Meat by Irradiation Processing.

Research has demonstrated that ionizing radiation can inactivate parasites, eliminate or greatly reduce the populations of microbial pathogens, and extend the shelf life while preserving the desired nutritional and sensory properties of refrigerated poultry and red meats. Foodborne pathogens can be greatly reduced in population and sometimes completely eliminated from foods by low doses of ionizing radiation. The shelf life of poultry, pork, and beef can be significantly extended by treatment with ionizing radiation. Combination treatments with vacuum packaging or modified atmosphere packaging and ionizing radiation have produced better than predicted results. Additional research is needed on the combined processes.

Toxicology Studies of Irradiation-Sterilized Chicken.

Results of nutritional, genetic, and toxicological studies of shelf-stable chicken sterilized by ionizing radiaiton are presented. No evidence of genetic toxicity or teratogenic effects in mice, hamsters, rats, and rabbits was observed. There was an unexplained reduction in the hatchability of eggs of Drosophila melanogaster reared on gamma-irradiated meat. No treatment-related abnormalities or changes were observed in dogs, rats, or mice during multigeneration studies. These nutritional, genetic, and toxicological studies did not provide definitive evidence of toxicological effects in mammals due to ingestion of chicken meat sterilized by ionizing radiation.

Determination of Irradiation D-Values for Aeromonas hydrophila.

This study examined the radiation resistance of Aeromonas hydrophila , a psychrotrophic pathogen of emerging importance. Five strains of Aeromonas hydrophila (three clinical and two food isolates) were irradiated in a Cesium-137 source at doses up to 150 Krads. The bacterium was irradiated in growth broth, phosphate buffer, ground bluefish or ground beef. Surviving bacteria were counted on nutrient agar or starch ampicillin agar. Radiation resistance was expressed as D-values (dose in Krads to yield a 10-fold decrease in viable number) and ranged from 14 to 22 Krads at 2 ± 1°C for most variables studied. Decreasing the temperature during irradiation increased the radiation resistance (raised the D-values). The results of this study indicate that a pasteurizing dose of ionizing radiation of 150 Krads is sufficient to kill the levels of Aeromonas hydrophila found in retail fresh foods.

Foodborne Viruses: Their Importance and Need for Research 1.

All viruses known to be normally transmissible through foods and of concern to human health emanate from the human intestine. The outbreaks of hepatitis A and recently of gastroenteritis attributed to Norwalk-like viruses most likely developed from feces-contaminated fingers of infected food handlers or water polluted with feces. With few exceptions no recorded outbreak has depended on the ability of virus to withstand even limited heating in food. New and better methods of detection are needed for hepatitis A and Norwalk viruses in foods. It has been well documented that international trade in food products of animal origin can result in the introduction of animal disease into areas in which the disease does not exist. This fact has given rise to programs of research and development for industrially applicable technology to rid animal products from the agents of animal diseases. The survival of viruses inclusive of etiological agents of foot-and-mouth disease, African swine fever, swine vesicular disease and hog cholera virus is reviewed in this paper and new research approaches are suggested. The general need for additional research of foodborne viruses is discussed.

Plant Trials of Bacon Made with Lactic Acid Bacteria, Sucrose and Lowered Sodium Nitrite.

Bacon prepared with 40 and 80 mg/kg (ppm) sodium nitrite, 0.7% sucrose and a culture of Pediococcus acidilactici (Wisconsin Process), and control bacon prepared with 120 ppm sodium nitrite and no added sucrose or bacterial culture were produced at three commercial bacon production plants. Sodium chloride, phosphate and sodium ascorbate (or sodium erythorbate) levels, as well as other processing conditions such as pumping rate, smokehouse temperature and time, forming and slicing conditions, were those normally used by each plant. Randomly selected samples of each lot were used for a challenge experiment with Clostridium botulinum (types A and B), with ca. 1,000 heat-shocked spores/g of bacon inoculated on each slice, vacuum packaged and incubated at 27°C. Samples were taken periodically up to 56 d of incubation and examined for the presence of botulinal toxin. The challenge experiment revealed that test bacon was substantially greater in antibotulinal properties than the control bacon. Residual nitrite levels of test bacon were lower than those of the control bacon, as were nitrosamines formed upon frying. Average N-nitrospyrrolidine level was 8.6 µg/kg (ppb) in the control, <2.7 ppb in the 80-ppm nitrite product, and <1.6 ppb in the 40-ppm nitrite product. This study indicates that bacon commercially prepared by the Wisconsin Process with 40 or 80 ppm sodium nitrite has a lesser risk of nitrosamine and botulinal toxin formation than bacon prepared with 120 ppm sodium nitrite and no added sucrose and lactic acid bacteria.