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PubMed1982

Effect of feeding a raw winged bean seeds on gastrointestinal functions in rats.

The primary cause of the adverse effects of feeding of raw winged bean seeds in rats was investigated. In experiment 1, rats were fed on either a raw winged bean diet or a steamed winged bean diet for 10 days. Body weight gain of rats fed on 30% raw winged bean diet was significantly lower than that of rats fed on 30% steamed winged bean diet. The adverse effect of the feeding of 30% raw winged bean diet on growth was accompanied by disorders of the gastrointestinal tract including a significant reduction in intestinal sucrase activity, not being improved with feeding of the diet supplemented with methionine. In experiment 2, rats fasted for 2 days were refed on a 10% casein diet, a 30% raw winged bean diet or a 30% steamed winged bean diet, in which most of the carbohydrate component was sucrose, for 4 days. Although body weight gain and food consumption in rats refed on these winged bean diets were lower than those in rats refed on 10% casein diet, the effects of feeding of the raw winged bean diet on body weight gain and food consumption were extremely deleterious as compared with those of feeding of the steamed winged bean diet. Significant reductions in hydrolase activities localized in the brush border membrane of the small intestine were found in rats refed on the raw winged bean diet prior to the occurrence of apparent disorders in the gastrointestinal tract. These findings suggest that the primary cause of the adverse effects of raw winged bean seed feeding the disorders in the small intestine caused by lectin or similar substances in raw winged bean seeds.

Alkaline Phosphatase↗

PubMed2000

Growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes in egg products held at different temperatures.

Growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes in steamed eggs and scrambled eggs held at different temperatures (5, 18, 22, 37, 55, and 60 degrees C) were investigated in the present study. Among the holding temperatures tested, both pathogens multiplied best at 37 degrees C followed by 22, 18, and 5 degrees C. In general, E. coli O157:H7 grew better in the egg products than L. monocytogenes did at all the storage temperatures tested except at 5 degrees C. E. coli O157:H7 did not grow in steamed eggs and scrambled eggs held at 5 degrees C. L. monocytogenes showed a slight population increase of approximately 0.6 to 0.9 log CFU/g in these egg products at the end of the 36-h storage period at 5 degrees C. The population of both pathogens detected in the egg products was affected by the initial population, holding temperature, and length of the holding period. It was also noted that L. monocytogenes was more susceptible than E. coli O157:H7 in steamed eggs held at 60 degrees C. After holding at 60 degrees C for 1 h, no detectable viable cells of L. monocytogenes with a population reduction of 5.4 log CFU/g was observed in steamed eggs, whereas a lower population reduction of only approximately 0.5 log CFU/ml was noted for E. coli O157:H7.

Animals↗

PubMed2002

Utilisation of energy from digester gas and sludge incineration at Hamburg's Köhlbrandhöft WWTP.

At Hamburg's Köhlbrandhöft WWTP the demand for external energy supply is minimised by state of the art sludge treatment. The sludge is subjected to thickening, anaerobic digestion, dewatering, drying and incineration. The digester gas is used in a combined gas and steam turbine process. The sludge incineration also produces steam, which is also used in the steam turbine that follows the gas turbine. The turbines produce electricity, partially expanded steam is used for the sludge drying process. Heat from the condensation of vapours from sludge drying is used to heat the anaerobic digesters. The overall process requires no external heat or fuel and produces 60% of the WWTP's electricity demand.

Bacteria, Anaerobic↗

PubMedDate not supplied

Physical properties of starch meals in vivo and in vitro and their influence on gastric emptying and oral glucose tolerance test.

In study A, consisting of four groups of six subjects each, we measured the differences in pH, viscosity, and osmolality of in vivo and in vitro samples of steamed rice, congee, and 16.6 and 5% glucose solutions in 300-ml volumes. The physical properties of starch meals in vivo are different from in vitro samples, which may account for discrepancies among previous studies of glucose tolerance and gastric emptying. In study B, test meals of 300 ml of steamed rice, congee, 16.6% glucose, 5% glucose or a combined congee-metoclopramide meal (in which 10 mg metoclopramide i.v. was given 15 min before the congee was eaten) were given to seven subjects. Blood samples were taken, and the serum glucose and insulin responses were determined. The meals were labeled with 99mTc pentetic acid microcapsules, and the gastric emptying rates were calculated. Metoclopramide increased the gastric emptying of congee to that approaching steamed rice. The incremental glucose response to steamed rice was greater than that to congee, but the incremental insulin response was greatest with congee plus metoclopramide. The physical form of the food influences the blood glucose and insulin response and the rate of gastric emptying. The gastric emptying rate may be the major mechanism for the increased insulin response.

Adult↗

PubMed1990

[Modified microdiffusion method for fluoride analysis of foodstuffs].

In fluoride analysis, there are two procedures for the determination of fluoride depending on nature of samples. One procedure directly can determine fluoride contents by fluoride ion electrode, dissociating fluoride from the sample with the acid (perchloric acid). The other procedure needs to separate fluoride from biological sample using steam-distillation or micro-diffusion method, and then the determination by means of fluoride ion electrode can be applied. In this study, we applied a modified microdiffusion method by Hinoide (1990) for its availability in different temperatures and reaction time, and then estimated to determine fluoride contents of Shrimp (Sakura-shrimp) as a biological sample by this method. It is also very important to determine fluoride contents of foodstuffs and biological samples with regard to bioavailability of fluoride in vivo. The results were as follows: 1. Using the modified microdiffusion method, the fluoride recovery rate attained more than 95% in the range of 0.1-10 micrograms fluoride from a standard solution under the experimental condition of 60 degrees C and 90 degrees C of reaction temperatures and 60, 90 and 120 minutes of reaction time. 2. For the sample of shrimp, fluoride contents analyzed by means of the modified micro-diffusion and steam-distillation methods showed almost similar values, although the fluoride contents by steam-distillation method revealed relatively lower value. The difference might be derived from a loss of fluoride in ashing the sample before applying the steam-distillation method. The modified microdiffusion method used in this experiment can be utilized routinely and precisely in fluoride analysis for small amounts of biological sample.

Animals↗

PubMed1987

Clinical studies with treated clotting factor concentrates.

We carried out safety studies in 45 previously untreated patients with congenital coagulatory defects, who needed to be treated with clotting factor concentrates. Non-A, non-B hepatitis developed in patients who received dry heated F VIII preparations with or without chloroform, but not in those who were infused with hot-steam treated F VIII or chromatography treated F IX. Hepatitis B developed in 3 unvaccinated patients who received the same lot of hot steam treated F VIII. None of the 45 patients we have investigated developed HTLV-III/LAV antibody. Thus, dry heating of concentrates does not prevent hepatitis transmission. Hot-steam and hydrophobic interaction chromatography seem to be more effective in preventing hepatitis transmission, but not completely safe. All the above procedures except hot steam seem to protect from hepatitis B. They all seem to prevent HTLV-III/LAV transmission.

Antibodies, Viral↗

PubMed1983

[Enterococci and coliforms in yellow sheep cheese].

The developmental dynamic of enterococci and coliforms was followed up in the entire technologic process and the storage of kashkaval (yellow cheese of ewe milk) under the conditions of modern industrial production. It was found that during the whole industrial cycle up to the steam cooking of curd the amount of enterococci grew and reached its peak value in the cheddarized cheese curd (2.4--30 million per gram), increasing from 10 to 34 times as against its level in the initial milk used. The coliform bacteria also rose in number, and their amount reached maximum values of 10 to 120 mill/g in the processed and dipped curd, after which a slowly advancing reduction set in. Species of the Enterobacter (55.1%), Escherichia (14.1%), Citrobacter (19.2%), and Klebsiella (11.5%) genera were isolated. The steam cooking of cheddarized curd produced an unfavourable effect on enterococci (pasteurization effect of up to 98.3 to 99.9%) and a lethal effect on the coliforms. Enterococci that resisted steaming multiplied in kashkaval and reached their highest level--960 000 up to 39 mill/g--between the 30th and the 60th day of production after which their numbers dropped. Their amount in the ripened product varied from 95000 to 17.8 mill/g, and on the 240th following production--from below 100 to 1.6 mill/g. Coliform bacteria were not found in 0.1 g of the product mass during ripening and storage of kashkaval. Out of the 196 strains that were differentiated as enterococci 30.7 per cent of the fecalis subgroup, and 69.3 per cent--of the Sp. faecium-durans subgroup. After steaming 92.3 per cent of the strains were of the Str. faecium and Str. durans species.

Animals↗

PubMed1976

[UHT--behandeling van melk (author's transl)].

Pasteurisation of milk provides protection for the consumer against pathogens which may be present in the raw milk, and improves its keeping quality. Sterilisation provides indefinite keeping quality but has an undesirable effect on the flavour and nutritive value of the milk. Ultra high temperature (UHT) treatment produces a milk with prolonged shelf life at ambient temperatures yet has practically the same effect on colour, falvour and nutritive value as pasteurisation. UHT treatment of milk involves preheating to 80 degrees C and then quickly raising the temperature, either by indirect heating in a tubular heater or by direct steam injection, to 130 degrees-- to 150 degrees C at which temperature it is kept for 3 to 5 sec. Cooling follows immediately. Systems in operation in South Africa use steam injection for heating to sterilising temperatures. Evaporation cooling is obtained by subjecting milk to a partial vacuum. This removes any water added during heating by condensing steam and also removes steam-volatile off-flavours. UHT-treated milk is packed aseptically, usually into heat-sealed paperboard laminated cartons. Intact packages can be kept for up to three months. Absolute sterility cannot be obtained by UHT processing. The term "sterilising effect", introduced by Galesloot, means the log10 of the ratio of initial spore count to surviving spore count. A spoilage rate of not more than one litre package per 1000 is considered satisfactory. For laboratory control samples of the sterilized milk are incubated at temperatures favourable to germination of mesophilic and thermophilic spores respectively. After incubation the milk is examined for flavour and physical appearance, subjected to the standard plate count and tested for increase in acidity and decrease in stability towards the alcohol test. Milk for UHT treatment must possess protein stability in the alcohol test, be of good bacteriological quality, and a low spore count in particular.

Animals↗

PubMedDate not supplied

Effect of rendering procedures on the scrapie agent.

A pool of scrapie-infected sheep brains was used to spike mixtures of porcine bone and intestine. These were processed in pilot-scale facsimiles of 12 rendering procedures that were in use within the European Union in 1991, and three that were not. Meat and bone meal, and tallow, were produced from the rendered tissues. Suspensions of all the meat and bone meal samples, and two of the tallow samples were assayed in mice for scrapie infectivity. Neither of the tallow samples had any detectable infectivity but the meat and bone meal samples were positive, except for those produced by processes involving exposure to hyperbaric steam. In addition, greaves were produced from the scrapie-spiked raw materials by an atypical low-temperature process and subjected to solvent extraction with hot heptane. The treated greaves were then exposed to steam to drive off residual solvent. Although the starting titre of infectivity in these greaves was low, there appeared to be no reduction in infectivity as a result of the treatments with hot heptane and steam. However, there was no detectable infectivity in the meat and bone meal prepared from the greaves produced by the atypical low-temperature process after it had been exposed to hyperbaric steam.

Animals↗

PubMed1998

Use of hemicellulose hydrolysate for beta-glucosidase fermentation.

Hydrolysis of cellulose by Trichoderma cellulases often results in a mixture of glucose, cellobiose, and low-mol-wt cellodextrins. Cellobiose is nonfermentable for most yeasts, and therefore it has to be hydrolyzed to glucose by beta-glucosidase prior to ethanol fermentation. In the present study, the beta-glucosidase production of one Penicillium and three Aspergillus strains, which were previously selected out of 24 strains, was investigated on steam pretreated willow. Both steam-pretreated willow and hemicellulose hydrolysate, released during steam explosion of willow, were used as carbon sources. Reference cultivation runs were performed using prehydrolyzed Solka Floc and glucose. The four strains were compared with Trichoderma reesei regarding sugar consumption and beta-glucosidase production. Aspergillus niger and Aspergillus phoenicis proved to be the best enzyme producers on hemicellulose hydrolysate. The maximum beta-glucosidase activity, 4.60 IU/mL, was obtained when A. phoenicis was cultivated on the mixture of hemicellulose hydrolysate and steam-pretreated willow. The maximum yield of enzyme activity, 502 IU/g total carbohydrate, was obtained when Aspergillus foetidus was cultivated on the hemicellulose hydrolysate.

Aspergillus↗

PubMed1998

Lifting the fog in endoscopic surgery.

This article describes a problem encountered in addressing the phase out of CFCs, the subsequent reduction in the use of the low temperature sterilization modailities and the move towards greater utilization of steam sterilization. The ban of CFCs drastically changed the way reprocessing of sterile supplies and equipment is performed in Hospitals. In 1994 at St. Boniface General Hospital Operating Room in Winnipeg, Manitoba, preparations began to meet the challenge. One of the measures taken was to review purchases for new equipment and where ever possible, choose equipment that could be sterilized using steam as opposed to using Ethylene Oxide sterilization. Medical device companies responded to the CFC ban by modifying the manufacture of delicate equipment to withstand the high temperatures used in steam sterilization. Equipment such as rigid telescopes could be steam sterilized for the first time.

Chlorofluorocarbons↗

PubMed2004

Heated, humidified air for the common cold.

BACKGROUND: Heated, humidified air is used by common cold sufferers since the invention of the steam kettle. There is scientific literature available investigating this mode of therapy using a rhinotherm. The present reviews addresses to the use of hot, humid air in common cold. OBJECTIVES: To assess the effects of inhaling heated water vapour with the help of a rhinotherm (an equipment designed to deliver heated water vapour to a person's nasal cavity), in the treatment of the common cold by comparing: a. symptoms b. viral shedding c. nasal resistance after a natural or experimentally induced common cold. SEARCH STRATEGY: In the initial review published in issue 3, 1999 of The Cochrane Library, we searched MEDLINE with MeSH headings: common cold, rhinopharyngitis, inhalation, steam, heated vapour, rhinothermy (January 1966 to July 1999). EMBASE, Current Contents, review articles, cross references were also searched. Attempts were also made to contact the manufacturers for any unpublished data. In this updated review, we have searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2003), MEDLINE (January 1966 to November Week 2, 2003), EMBASE (January 1990 to November 2003), and Current Contents (current five years). SELECTION CRITERIA: Randomized trials using heated water vapour in a standardized way in patients with the common cold or volunteers with experimental induction of rhinovirus infection were included in the review. DATA COLLECTION AND ANALYSIS: All the articles retrieved were initially subjected to a review for inclusion / exclusion criteria. Review articles, editorials, abstracts with inadequate outcome description were excluded. Studies selected for inclusion were subjected to a methodological assessment. MAIN RESULTS: The results of a systematic review of six trials with 319 participants, support the use of warm vapour inhalations in the common cold in terms of relief of symptoms (Odds Ratio with 95 % CI 0.31, 0.16-0.60, Relative risk 0.56, 0.4-0.79). Results on symptom score indices were equivocal. None of the studies demonstrated a worsening of clinical symptom scores. One study demonstrated increased nasal resistance one week after steam inhalation in contrast to an earlier study which showed improvement in the nasal resistance. There was no evidence of decreased viral shedding measured by virus isolation in the nasal secretions (Tyrrell 1989a) or measurement of viral titres in nasal washings among treatment group. The rhinovirus titres in the nasal washings from the treatment group were the same as those of the placebo group on day one prior to the treatment and on all four days after the treatment. The area under curve (Hendley 1994) was also similar in the placebo and treatment groups for titres of virus in the nasal washings as were the average viral titres across five days of follow up, the maximum values after treatment, and viral shedding velocity i.e. amount of virus shed per day (Hendley 1994). Minor side effects due to thermal stress were reported in all the studies. REVIEWERS' CONCLUSIONS: Three trials demonstrated beneficial effects on the symptoms of the common cold. One study from Israel showed a decrease in nasal resistance measured by peak nasal expiratory and inspiratory flow rate. Studies done in North America failed to show any objective improvement in outcome measures with the study intervention. A multi-centre double blind randomised controlled trial testing this therapy with uniform outcome measures is recommended.

Air↗

PubMed1999

An easy and safe method to store and disinfect explanted skull bone.

In our department extensive decompression craniectomies became the treatment of choice for patients with massive cerebral oedema following either trauma or acute cerebral infarction. The remarkable survival rates of this neurosurgical technique created the problem of adequate vault defect reconstruction. To evaluate the biological safety of using stored autologous skull flaps for this purpose, we compared three different disinfection methods. Skull bone fragments stored at -21 degrees C for different periods of time were artificially contaminated with clinically relevant strains of Serratia marcescens, Enterococcus faecium and Staphylococcus aureus. As potential methods for disinfection we tested immersion in 3% H2O2, boiling in normal saline for 15 and 30 minutes and a special process of steam disinfection at a temperature of 75 degrees C for 20 minutes. We were able to demonstrate that only steam disinfection completely eliminated the bacterial strains tested. Refrigeration plus steam disinfection of autologous skull bone prior to re-implantation seems to offer reliable safety for its use for defect closure. It is available at reasonable cost in many hospitals and does not require a bone bank.

Bone Transplantation↗

PubMed2003

Effect of laboratory procedures and thermocycling on the shear bond strength of resin-metal bonding systems.

STATEMENT OF PROBLEM: During fabrication or repair of removable partial dentures, resin-to-metal or resin-to-denture tooth bonds may be stressed by laboratory procedures. PURPOSE: The purpose of this in vitro study was to evaluate the effect of steam cleaning, boiling, ultrasonic cleaning (laboratory procedures), and thermocycling on shear bond strength of resin bonds to metal and denture teeth. MATERIAL AND METHODS: Resin-metal bonding systems and their specific veneer resins (Rocatec, Sinfony; Rocatec, Visio-Gem, HLC-BOND, Zeta LC and Ducera experimental veneer resin) were tested on a Co-Cr alloy (Wirobond C). The veneer resins were bonded to resin denture teeth. The experimental groups (n=7) were subjected to the following conditions: 24-hour storage of the specimens in air (group I, control group), storage in air and treated with simulated laboratory procedures (2 minutes steam cleaning, 15 minutes ultrasonic cleaning at room temperature, 1 hour boiling in water, group II), storage in air with thermocycling (5000 cycles, 5 degrees to 55 degrees C, group III), storage in air with laboratory procedures followed by thermocycling (group IV), and storage in air with thermocycling followed by laboratory procedures (group V). Shear strength tests (MPa) were performed with a universal testing machine until fracture. After shear bond testing, the failure mode of the resin-metal and resin-denture tooth bonds was assessed. Statistical analysis of the results was carried out with one-way analysis of variance and Bonferroni-Dunn's multiple comparisons post hoc analysis for test groups (alpha=0.05). RESULTS: Except for Ducera/denture tooth specimens (groups III to V: 8.7 +/- 3.4-9.1 +/- 1.7; 10.8 +/- 1.9 MPa control group), the Wirobond C and denture tooth specimens (groups III, IV and V: 1.4 +/- 0.9-11.9 +/- 2.3 MPa), showed significantly lower shear bond strengths than the corresponding control groups (7.5 +/- 2.9-21.0 +/- 3.4 MPa, P<.05). The shear bond strengths of group II of Sinfony/Wirobond C (11.6 +/- 3.3 MPa, P<.0001), Visio-Gem/Wirobond C (7.4 +/- 1.9 MPa, P<0.0001), Ducera/Wirobond C (11.8 +/- 2.9 MPa, P<.0001) and of Zeta/denture tooth (3.9 +/- 1.6 MPa, P=.0005) were significantly decreased by steam, boiling, and ultrasonic procedures compared with the corresponding control groups (21.0 +/- 3.4 MPa; 14.7 +/- 4.0 MPa; 19.1 +/- 2.3 MPa; 7.5 +/- 2.9 MPa, respectively). No significant differences were noted among groups III, IV, and V. Co-Cr specimens subjected to the Rocatec system and bonded with Sinfony and HLC BOND/Zeta specimens showed cohesive failure. Adhesive failure was observed for the experimental veneer resin on the Co-Cr specimens and for all veneer resins on the denture teeth. CONCLUSION: Simulation of laboratory procedures and thermocycling caused a significant drop in shear bond strength of metal-resin and denture tooth-resin bonds for most of the tested veneer resins. Thermocycling before shear testing had the same effect on veneer resin bond strength as the simulated laboratory procedures.

Acrylic Resins↗

PubMed2001

The regeneration of field-spent granular-activated carbons.

The thermal regeneration of field-spent granular-activated carbons (GAC) is being increasingly adopted as a cost-effective alternative to disposal. The success of this practice requires the adjustment of process conditions to maximise the recovery of the original carbon characteristics while minimising carbon loss. This paper describes an investigation into the regeneration of several field-spent GAC representative of those typically generated by the drinking water treatment industry. The carbons were initially investigated for their ash contents and inorganic compositions in order to determine the accumulation of metallic species that affect the regeneration process. Regeneration was conducted in steam at 800 degrees C over reaction times between 0 and 60 min in order to achieve different degrees of carbon gasification. Weight losses were determined for each condition and the resulting carbons characterised for their apparent density, porosity, surface area and aqueous adsorption characteristics. Results showed that spent carbons recovered most of their adsorption characteristics when heated to 800 degrees C under inert conditions. Steam gasification in the range of 5-10 wt% burn-off had some positive effects on the characteristics of the spent carbons which were in most cases counteracted by a reduction in the carbon yield. Steam gasification in excess of 15 wt% burn-off caused a rapid increase in the carbon mesoporosity but a significant deterioration in the carbon microporosity, BET surface area and adsorption capacity for organic species of small molecular size.

Adsorption↗

PubMed1998

Nonacid meat decontamination technologies: model studies and commercial applications.

Increased consumer awareness and concern about microbial foodborne diseases has resulted in intensified efforts to reduce contamination of raw meat, as evidenced by new meat and poultry inspection regulations being implemented in the United States. In addition to requiring operation of meat and poultry slaughtering and processing plants under the principles of the hazard analysis critical control point (HACCP) system, the new regulations have established microbiological testing criteria for Escherichia coli and Salmonella, as a means of evaluating plant performance. These developments have renewed and intensified interest in the development and commercial application of meat and poultry decontamination procedures. Technologies developed and evaluated for decontamination include live animal cleaning/washing, chemical dehairing, carcass knife-trimming to remove physical contaminants, steam/hot water-vacuuming for spot-cleaning/decontamination of carcasses, spray washing/rinsing of carcasses with water of low or high pressures and temperatures or chemical solutions, and exposure of carcass sides to pressurized steam. Under appropriate conditions, the technologies applied to carcasses may reduce mean microbiological counts by approximately one-three log colony forming units (cfu)/cm2, and some of them have been approved and are employed in commercial applications (i.e., steam-vacuuming; carcass spray-washing with water, chlorine, organic acid or trisodium phosphate solutions; hot water deluging/spraying/rinsing, and pressurized steam). The contribution of these decontamination technologies to the enhancement of food safety will be determined over the long term, as surveillance data on microbial foodborne illness are collected. This review examines carcass decontamination technologies, other than organic acids, with emphasis placed on recent advances and commercial applications.

Animals↗

PubMed1985

Biological sterilization monitors: a four-year in-use evaluation of two systems.

Biological monitors (BI) are considered to be the best monitor of the sterilization process yet false positives may result in recalls and quality assurance difficulties. To assess the frequency, type and reasons for questionable results, we undertook a 4-year in-use study of two commonly used BI types--spore strips (Spordi) and a self-contained crushable ampule (Attest)--for both steam and ethylene oxide (EO). After laboratory verification of time/kill ratios for a portion of each involved lot, 2 BI of each type were placed in test pack within a randomly selected load run at standard time and temperature. All resulting positive BI were subcultured. Steam cycle positives were uncommon (32/1,1710 positive Spordi, 1.9%; 20/1,710 positive Attest, 1.2%) and could be related to chamber temperature or steam quality. All of the 4 BI per load were positive in only three loads; physical monitors indicated gross malfunction. Five positive Spordi were due to either contaminants or a malfunctioning incubator. EO-related positives were more common (53/1,109 positive Spordi, 4.8%; 25/1,109 positive Attest, 2.3%). One-half of the Spordi tests became positive after 48 hours of incubation. Organisms other than B. subtilis were recovered from 49.1% of the positive tests (26/53). The Attest was remarkable for its lack of contamination; 1/25 was positive for Pseudomonas stutzeri only. More positives were observed during the winter months when relative humidity was below 20%. This finding was more commonly observed with the EO Attest. In summary, we found no significant difference in the performance of either BI.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacillus subtilis↗

PubMed2001

Influence of processing stages on antimutagenic and antioxidant potentials of rooibos tea.

The antimutagenic and antioxidant potentials of rooibos (Aspalathus linearis) tea samples, collected from each of its major processing stages, were evaluated according to the Salmonella typhimurium mutagenicity test and the hydrogen donating ability and superoxide anion radical scavenging assays, respectively. Ten random samples were collected before and after fermentation, as well as after sun-drying, sieving, and steam pasteurization. Results indicated that the fermented tea had a significantly (P < 0.05) lower antimutagenic and antioxidant potential than the unfermented tea. Of the different processing stages, the most significant reduction in the antimutagenic and antioxidant property of the tea was found during the "fermentation" step. Sun-drying, sieving, and steam pasteurization also reduced the antimutagenic potential of the tea, although not to the same extent as the first processing step. The hydrogen donating ability was significantly increased after steam pasteurization in comparison to those of fermented and sun-dried tea. Pasteurization did not affect superoxide anion radical scavenging in comparison to fermented tea. Differences seem to exist in the antimutagenicity and antioxidant potencies of the tea sampled at the various stages during processing. A possible role of tea polyphenols in the antimutagenic and antioxdant activities of the tea is suggested as processing caused a significant reduction in the total polyphenolic content.

2-Acetylaminofluorene↗