Gamma processing of Arabic bread for immune system-compromised cancer patients

Arabic bread prepared from local Saudi flour contained a total of up to 10(4) organisms per g. Most of these were bacterial spores that survived the baking process (1.3 X 10(2) to 3.5 X 10(3] and a small number of yeasts and molds (10 to 40 cells per g). The organisms in Arabic bread appear to be harmless to healthy individuals. However, for immune system-compromised cancer patients and bone marrow transplant recipients, it is prudent to irradiate the bread to reduce microbial contamination. The decimal reduction doses (10% survival) for the most radiation-resistant organisms (spore formers) in bread were 0.11 to 0.15 Mrad. Accordingly, 0.6 Mrad was sufficient to reduce the number of spores in Arabic bread by a factor of 10,000, i.e., to less than 1/g. This treatment constitutes radiation pasteurization (radicidation), and to this extent, provides a margin of microbiological safety. Sensory evaluation by the nine-point hedonic scale showed no detectable loss of organoleptic quality of bread up to 0.6 Mrad, while irradiation to 2.5 Mrad induced unacceptable organoleptic changes.     

Effect of γ Irradiation on the Microflora of Freshwater Fish: III. Spoilage Patterns and Extension of Refrigerated Storage Life of Yellow Perch Fillets Irradiated to 0.1 and 0.2 Megarad1

Maximal shelf life was determined and microbial flora were compared for irradiated (0.1 and 0.2 Mrad) and nonirradiated yellow perch fillets stored at 1 C. Shelf life was estimated by organoleptic determinations. Microbiological studies included determination of the effects of irradiation on the total aerobic microbial population, lag phase, and rate of growth. Genera of organisms isolated from fillets through the course of microbial spoilage were identified, and the proteolytic activity of the organisms was determined. Plate counts for fish prior to irradiation showed the presence of approximately 10(6) organisms per g of sample. Irradiation to 0.1 and 0.2 Mrad produced 1.4 and 3 logarithm reductions of the initial count, respectively. Irradiation to 0.1 and 0.2 Mrad approximately doubled the product's shelf life. Organisms initially isolated from the nonirradiated fillets, in order of decreasing number, consisted of Flavobacterium, Micrococcus-Sarcina, Achromobacter-Alcaligenes-Mima, Pseudomonas, Microbacterium, Vibrio, Bacillus, Corynebacterium, Lactobacillus, Brevibacterium, and Aeromonas. By the 6th and 9th days of fillet storage, Pseudomonas and the Achromobacter group were the predominant organisms. All members of the genus Flavobacterium, but not all members of the genus Pseudomonas, were proteolytically active on raw fish juice-agar and skim milk-agar media. The Achromobacter group was found to be nonproteolytic on both media. Residual flora of fillets irradiated to 0.1 and 0.2 Mrad consisted of the Achromobacter group, Lactobacillus, Micrococcus-Sarcina, and Bacillus. Their sequence in predominance, however, varied with dose level. Not all proteolytic bacteria in the fillets were eliminated by 0.1 and 0.2 Mrad; proteolytic Micrococcus-Sarcina survived these treatments.     

Survival and growth of Bacillus cereus in bread

Bread doughs were artificially inoculated with spores of six Bacillus cereus strains at different inoculum levels and counts of survivors in bread determined during storage at 27.5 degrees C. No B. cereus were isolated from the centre crumb of 400 g loaves when the dough contained less than 10(4) spores/g whereas with 800 g loaves survival occurred with doughs containing 5.0 X 10(3) spores/g. With all strains there was a period of at least 24 h before multiplication took place in the bread. The inclusion in dough of 0.2% of calcium propionate, based on flour, effectively delayed germination and subsequent multiplication of B. cereus spores. It is concluded that the risk of food poisoning due to the presence of B. cereus in bread is minimal.     

Comparative Resistance of Strains of Clostridium botulinum to Gamma Rays

A total of 102 strains of Clostridium botulinum (56 strains of type A, 43 type B, and 3 nontoxigenic strains which could not be typed) was examined for resistance to gamma rays. When these organisms were suspended in neutral phosphate buffer in concentrations of 10⁴ spores per tube, the threshold sterilizing dose appeared to be 1.4 Mrad. Partial survival to 1.4 Mrad was shown by 10.7% of the type A strains, 18.6% of the type B strains, and one of three nontoxigenic strains. Over-all, type A strains indicated higher radioresistance than type B strains, although there was overlapping. Representatives of the most resistant strains had D values of 0.317 to 0.336 Mrad; the D values of an intermediate group were 0.224 to 0.253 Mrad, and the most sensitive strain studied, 51B, had a D value of 0.129 Mrad. The radioresistance of Putrefactive Anaerobe 3679, strain S-2, was comparable to the intermediate C. botulinum group (D = 0.209).     

Radiation Sterilization of Prototype Military Foods. III. Pork Loin

Ten lots of pork loin, packed in cans, were inoculated with approximately 10(6)Clostridium botulinum spores per can. Each lot was seeded with a different strain; five type A and five type B strains were used. The pack comprised 5,690 cans, including controls, and contained about 10(9) spores per dose. The cans were irradiated with Co(60) in the range of 0 to 5.0 Mrad (0.5 Mrad increments) at 5 to 25 C, incubated for 6 months at 30 C, and examined for swelling, toxicity, and recoverable C. botulinum. The minimal experimental sterilizing dose (ESD) based on nonswollen, nontoxic, but nonsterile end points was 2.5 < ESD 相似文献   

Radiation Sterilization of Bacon for Military Feeding

Sliced, cured bacon, packed in cans and seeded with 6 × 10⁵ spores per can of Clostridium botulinum strains 33A or 41B, or with 3 × 10⁶ spores per can of strains 36A, 12885A, 9B, or 53B, was irradiated to various dose levels with γ radiation. Evidence provided by swelling, toxicity, and recoverable C. botulinum with 2,200 inoculated, irradiated cans demonstrated that: (i) 4.5 Mrad were more than adequate as a sterilization dose; (ii) the experimental minimal sterilizing dose was 2.0 Mrad, and the theoretical 12-log reduction dose was 2.65 or 2.87 Mrad depending on the method of calculation; (iii) some spoilage occurred at dose levels below 2.0 Mrad; (iv) all visible spoilage of irradiated bacon was due to strains 33A and 12885A only, whose D values were, respectively, 0.141 and 0.177 Mrad based on spoilage data, and 0.221 and 0.188 Mrad, respectively, when based on recovery data; (v) toxic cans did not always result in swelling, nor did swollen cans always produce toxic spoilage; and (vi) viable C. botulinum can exist for at least 8 months in storage at 30 C without producing visible or toxic spoilage at doses below 2.0 Mrad.     

Radiation Injury of Clostridium botulinum Spores in Cured Meat

Cans of chopped ham, inoculated with spores of Clostridium botulinum strains 33A and 41B at levels of 2,500 and 250 per gram, were subjected to an enzyme-inactivating heat treatment and irradiation with 0.5, 1.5, 2.5, or 3.5 Mrad of Co(60). A portion of the pack was not irradiated, and received a commercial thermal process (F(0) = 0.2). Viable spores were enumerated after treatment and after 6 months of incubation at 30 to 37.7 C. Toxic spoilage occurred at 0 and 0.5, but not at 1.5, 2.5, or 3.5 Mrad. More spoilage and toxin formation occurred in the product irradiated at 0.5 Mrad than in identical product receiving no radiation treatment. Confirmed botulinal spores were isolated from all of the radiation variables of 2,500 per gram-inoculated product and from all but the 3.5 Mrad low-inoculum cans. However, neither growth nor toxin was observed in unspoiled product. The "injury" phenomenon previously described in thermally processed cured meats (survival of botulinal spores without capacity for multiplication or toxigenesis) apparently occurs also in irradiated cured meats.     

Development of functional foods using psyllium husk and wheat bran fractions: Phytic acid contents

Wheat grain is a rich source of phosphorus which is present mostly as phytic acid and is distributed mainly in the bran and germ fractions. Phytic acid has now been recognized as an important phytochemical having antioxidant properties. This study deals with the determination of total as well as phytic phosphorus contents of psyllium (PS), course (CB) and fine wheat bran (FB) enriched pan bread and Arabic flat bread. The concentration of phytic acid in CB, FB, wheat germ, wholegrain wheat flour (WGF), white wheat flour (WWF), and psyllium were found to be 8.86 mg/g, 8.52 mg/g, 6.05 mg/g, 1.74 mg/g, 0.46 mg/g and 0.02 mg/g, respectively. Most of the phosphorus existed as phytic phosphorus (74.7–90.8%) in FB, CB, germ, and WGF as compared to only 42.6% in WWF. The level of phytic phosphorus in pan bread containing 10% CB, 20% FB (both containing with 5% PS) was found to be 0.63 mg/g and 1.53 mg/g respectively, as compared to only 0.34 mg/g in WWF pan bread, and 0.90 mg/g in WGF pan bread. The phytic phosphorus content in Arabic bread made with WGF and 3% psyllium was 1.32 mg/g as compared to only 0.48 mg/g in WWF Arabic flat bread. The results obtained indicate that the level of phytic phosphorus significantly increased in bread formulations containing CB, FB, and WGF, but no change with psyllium addition was observed. Adding these wheat mill fractions, and psyllium will enable bakeries not only to produce fiber-enriched pan bread and Arabic bread but would also benefit consumers to increase their dietary fiber intakes, and health-promoting phytochemicals coming from wheat bran and germ fractions.     

Radiation Sterilization of Prototype Military Foods: Low-Temperature Irradiation of Codfish Cake, Corned Beef, and Pork Sausage

"Screening" packs comprising 10 lots each of codfish cake, corned beef, and pork sausage, each lot containing about 10(6) spores of a different strain (five type A and five type B) of Clostridium botulinum per can, were irradiated at -30 +/- 10 C with a series of increasing doses (20 replicate cans/dose) of (60)Co gamma rays. The cans were incubated for 3 months at 30 C and examined for swelling, toxin, and recoverable botulinal cells. Based on the latter criterion of spoilage, median lethal dose (LD(50)) and D values were estimated for each strain in each food. The most resistant strain in codfish cake, corned beef, and pork sausage was, respectively, 53B, 77A, and 41B. There was no clear-cut trend in the comparative order of resistance between the two antigenic types among the three foods. LD(50) values gave essentially the same order of resistances as the D values and may be used interchangeably with the latter for the 10 test organisms. "Clearance" packs consisting of the most resistant strain (about 10(7) spores/can) with its respective food were irradiated with a variety of doses at -30 +/- 10 C, using 100 replicate cans/dose (about 10(9) spores/dose). These packs were incubated for 6 months at 30 C and assayed for the three types of spoilage. Based on recoverable cells, the experimental sterilizing doses (ESD) for codfish cake, corned beef, and pork sausage were 2.5< ESD 相似文献   

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum

An apparatus consisting of a Dewar flask and a relay system controlling the flow of liquid nitrogen permitted the irradiation of samples in tin cans or Pyrex tubes at temperatures ranging from 0 ± 1.5 C to -194 ± 2 C. An inoculated pack comprising 320 cans of ground beef containing 5 × 10⁴ spores of Clostridium botulinum 33A per can (10 cans per radiation dose) was irradiated with Co⁶⁰ at 0 and -196 C. Incubation was carried out at 30 C for 6 months. Approximately 0.9 Mrad more radiation was required to inactivate the spores at -196 C than at 0 C. Cans irradiated at -196 C showed partial spoilage at 3.6 Mrad and no spoilage at 3.9 Mrad; the corresponding spoilage-no spoilage doses at 0 C were 2.7 and 3.0, respectively. The majority of positive cans swelled in 2 to 14 days; occasional swelling occurred as late as 20 days. At progressively higher doses, swelling was delayed proportionally to the radiation dose received. The remaining nonswollen cans had no toxin after 6 months of storage, although occasional cans contained very low numbers of viable spores comprising on the average 0.1% of the original spore inoculum. The D₁₀ values in phosphate buffer were 0.290 Mrad for 0 C and 0.396 Mrad for -196 C; in ground beef, the corresponding D₁₀ values were 0.463 Mrad and 0.680 Mrad, respectively. These D₁₀ values indicate that the lethal effect of γ rays decreased at -196 C as compared with 0 C by 13.5% in phosphate buffer, and by 47% in ground beef.     

Comparative Resistance of Nonsporogenic Bacteria to Low-Temperature Gamma Irradiation

A total of 36 microorganisms, comprising 19 species of 11 genera, were screened for radiation resistance with (60)Co gamma rays at a radiation temperatore of -80 +/- 2 C in phosphate buffer (pH 7.0) under vacuum. Micrococcus radiodurans was the most resistant organism. An initial population of 2.8 x 10(5) cells per dose of this species survived 2.4 but not 2.7 Mrad. Of the remaining 18 species with initial populations of about 10(6) cells per dose, Streptococcus faecium survived 0.9 to 1.5 Mrad, depending on the strain tested. S. faecalis QM survived 0.9 but not 1.2 Mrad. S. faecalis 1539 and Alcaligenes faecallis survived 0.6 but not 0.9 Mrad. Three species of Salmonella, one strain each of Escherichia coli, Streptococcus lactis, and Aerobacter aerogenes survived 0.3 but not 0.6 Mrad. The remaining 22 bacteria did not survive 0.3 Mrad, the lowest dose tested. Detailed survival curve determinations for four strains of S. faecium, the most resistant of the test bacteria of public health significance, indicated the following order of resistance at -80 C: alpha21 > theta12 = F(6) > FEC. Each strain produced two exponential survival curves with different slopes, the breaks occurring at 0.3 to 0.5 Mrad. The D values (doses which reduce the microbial population by 90%) of the more resistant cell fractions were two- to three-fold higher than the more sensitive cell fraction. The resistance of strain alpha21 was determined at different radiation temperature (+5, -30, -80, -140, -196 C). The D value-radiation temperature relationship followed a quadratic equation. Computations of E(a) and Q(10) values (activation energy and temperature coefficient, respectively) showed a very small thermodynamic effect on radiation death. An Arrhenius evaluation of the temperature effect on cell kill indicated that there was no simple physicochemical mechanism which might explain the change in D value as a function of temperature.     

Radiation Sterilization of Prototype Military Foods: II. Cured Ham

Ten lots of diced cured ham, packed in cans, were inoculated with approximately 10(6)Clostridium botulinum spores per can. Each lot was seeded with a different strain (five type A and five type B strains). All cans were irradiated to various dose levels with Co(60). Evidence provided by swelling, toxicity, and recoverable C. botulinum with 6,350 cans demonstrated that: (i) 4.5 Mrad was more than adequate as a sterilization dose; (ii) the minimal experimental sterilizing dose (ESD) based on nonswollen nontoxic endpoints was 2.0 < ESD 相似文献   

Low-Temperature Irradiation of Beef and Methods for Evaluation of a Radappertization Process

An inoculated, irradiated beef pack (1,240 cans) study was conducted for the determination of microbiological safety for unrestricted human consumption. Each can contained a mixture of 10⁶ spores of each of 10 strains of Clostridium botulinum (5 type A and 5 type B), or a total of 10⁷ spores/can. The cans were irradiated to various doses (100 cans/dose) with ⁶⁰Co gamma rays at -30 ± 10 C, incubated at 30 ± 2 C for 6 months, and examined for swelling, toxicity, and recoverable botulinal cells. The minimal experimental sterilizing dose based on nonswollen, nontoxic sterile cans was 2.2 < experimental sterilizing dose ≤ 2.6 Mrad. Using recoverable cells as the most stringent criterion of spoilage, and assuming the conventional simple exponential (without an initial shoulder) rate of spore kill, the “12D” dose was 3.7 Mrad when estimated on the basis of a mixture of 10 strains totaling 10⁷ spores/can, and 4.3 Mrad if it is assumed that each can of beef contained 10⁶ spores of a single most resistant strain and all of these spores were of identical resistances. However, an analysis of the data by extreme value statistics indicated with 90% confidence that the spore death rate was not a simple exponential but might be a shifted exponential (with an initial shoulder), Weibull, lognormal, or normal, with a “12D” equivalent of about 3.0 Mrad regardless of the initial spore density per can. There was an apparent antagonism between the irradiated type A and B strains in the cans. Some of the cans contained type B toxin but did not include type B viable cells. Other cans had a mixture of type A and B toxins, but a large number of these cans did not yield recoverable type B cells. However, type A viable cells could always be demonstrated in those cans containing type A toxin.     

Comparison of Media for the Enumeration of Clostridium perfringens

For the enumeration of viable vegetative cells and spores of Clostridium perfringens, noncommercial (laboratory prepared) sulfite-polymyxin-sulfadiazine (SPS) agar, tryptone-sulfite-neomycin (TSN) agar, and Shahidi-Ferguson-perfringens (SFP) agar were statistically compared to SPS agar without antibiotics. The selectivities of these four media were also evaluated on the basis of their ability to inhibit the growth of pure cultures of a variety of other organisms. The average recovery of vegetative cells of 10 strains of C. perfringens with SFP agar was not significantly higher than with SPS agar with 10(4) organisms per g, but with 10(6) organisms per g it yielded significantly higher recoveries than SPS agar. TSN agar yielded significantly lower recoveries at both inoculum levels. SFP agar gave significantly higher recoveries of spores than SPS and TSN agars. Average plate counts of spores in SFP agar were 75% as high as in SPS agar without antibiotics, but only 45% of the spores grew in SPS agar and 25% in TSN agar. TSN agar was the most selective of the three media, but the selectivity of SPS agar approached that of TSN agar under the test conditions. SFP agar, which was the least selective of the media, allowed growth to some extent of nearly all of the facultative anaerobes tested.     

Survival and growth of Bacillus cereus in bread

Bread doughs were artificially inoculated with spores of six Bacillus cereus strains at different inoculum levels and counts of survivors in bread determined during storage at 27·5°C. No B. cereus were isolated from the centre crumb of 400 g loaves when the dough contained less than 10⁴ spores/g whereas with 800 g loaves survival occurred with doughs containing 5·0 times 10³ spores/g. With all strains there was a period of at least 24 h before multiplication took place in the bread. The inclusion in dough of 0·2% of calcium propionate, based on flour, effectively delayed germination and subsequent multiplication of B. cereus spores. It is concluded that the risk of food poisoning due to the presence of B. cereus in bread is minimal.     

Survival of Clostridium botulinum Spores

Radiation survival curves of spores of Clostridium botulinum strain 33A exhibited an exponential reduction which accounted for most of the population, followed by a “tail” comprising a very small residual number [7 to 0.7 spore(s) per ml] which resisted death in the range between 3.0 and 9.0 Mrad dose levels. The “tail” was not caused by protective spore substances released into the suspensions during irradiation, by the presence of accumulated radiation “inactivated” spores, or by heat shock of pre-irradiated spores. The theoretical number of spore targets which must be inactivated by irradiation was estimated both by a graphical and by a computation method to be about 80, and the D value was calculated to be 0.295 and 0.396 Mrad, respectively, in buffer and in pork pea broth.     

Resistance of Clostridium perfringens Type A Spores to γ-Radiation

The radiation resistance of the spores of a classical strain and of an atypical, heat-resistant strain of Clostridium perfringens was determined. Spores were produced in Ellner's and in a Trypticase broth medium. Approximately 10⁶ viable spores per milliliter were suspended in 0.06 m phosphate buffer and irradiated with γ rays from cobalt-60; the survivors were counted in Tryptone-yeast extract-agar by the Prickett-tube technique. Radiation D values for spores of the atypical strain in phosphate buffer and in cooked-meat broth were 0.23 and 0.30 Mrad, respectively, and the D value of the classical strain was 0.25 Mrad in phosphate buffer. Spores of the classical and atypical strains of C. perfringens type A are characterized by differences in heat resistance; yet, all strains tested demonstrated similar radiation resistance. Also, the spores were more resistant to ionizing radiation in cooked-meat broth than in phosphate buffer.     

Chemical Sensitization of Clostridium botulinum Spores to Radiation in Meat

Beef ground round inoculated with 1,000,000 spores of Clostridium botulinum 33-A per gram and containing various additives was exposed to gamma radiation. Spores were inactivated in samples (irradiated at 2.0, 2.5, and 3.0 Mrad) which contained sodium nitrate (1,000 ppm) plus sodium chloride (2.5%). Similar results were obtained when sodium nitrite (200 ppm) was substituted for sodium nitrate, except that there was evidence of spore survival in 1 of 120 cans irradiated at 2.0 Mrad. Spore destruction was based upon the absence of spores and mouse-lethal toxin in meat subcultures made from cans incubated at 35 C for 120 days. Spores were not destroyed when exposed to 2.5 or 3.0 Mrad in the absence of sodium nitrate, sodium nitrite, or sodium chloride. Furthermore, the use of these chemicals individually, together with radiation, was ineffective. The additives alone in the absence of radiation also did not cause spore destruction. Radiation levels of 2.0, 2.5, and 3.0 Mrad, when used with sodium chloride at 1.5 or 2.0% and sodium nitrate at 500 ppm or sodium nitrite at 100 ppm, were ineffective.     

Change in Microflora of Sewage Sludge by Gamma-ray Irradiation

Total bacteria of activated dewatered sludge cake of Takasaki city which amounted to 2 × 10⁹ per gram diminished rapidly with the radiation dose, but slowly after 0.5 Mrad, and 10³ per gram survived even after 10 Mrad irradiation. However, coliforms which amounted to 8 × 10⁷ per gram were inactivated below 0.5 Mrad irradiation. The predominant bacteria in non-irradiated sludge were Pseudomonas cepacia and it mainly survived up to 2 Mrad, but Bacillus were predominant at 0.5 to 0.7 Mrad irradiation. The main residual flora from 2 to 5 Mrad was composed of Pseudomonas soranacearum, P. cepacia and P. delafieldii, and the main residual flora in more than 5 Mrad irradiated sludge was P. flava . These typical strains of Pseudomonas in phosphate buffer were radiation sensitive, and their D₁₀ values were from 0.005 to 0.021 Mrad under aerobic irradiation conditions.     

A novel milky disease organism from Australian scarabaeids: Field occurrence,isolation, and infectivity

A novel milky disease organism has been found causing disease in Aphodius tasmaniae and other scarabaeid larvae in the field in Australia. The sporangium is exceptionally long, measuring 10.5 × 1.5 μm, with a small central spore, measuring 1.0 × 0.6 μm. The vegetative cell is about half the size of the sporangium. The disease was easily transmitted by injection of spores into the hemocoel, with typically milky symptoms developing in 2–4 weeks. Spores will form in vivo at temperatures down to 12°C. For A. tasmaniae third-instar larvae, the ID₅₀ by injection was 3 × 10² spores/larva, yet no infection resulted when larvae were reared in peat containing up to 10⁸ spores/g, i.e., the disease was not successfully transmitted per os. All 10 species of scarabaeids tested were susceptible to the disease when spores were injected; however, all attempts to infect larvae per os were unsuccessful. In vitro culture was also unsuccessful.