Total Aerobic Viable Counts Research Articles

Nutritional, Physicochemical and Microbial Quality of Ultrasound-Treated Apple-Carrot Juice Blends

Three different apple-carrot juice blends (60:40, 75:25 and 90:10, v/v) were prepared and treated with ultrasound with comparison to the conventional thermal pasteurization. Total aerobic viable count (TAC) were significantly lower in juice blends with lower pH (apple-carrot ratio of 90:10, v/v) than the blends with higher pH after one month storage at 4?C. TAC were similar in ultrasound-treated and thermal pasteurized juice blends. Changes of turbidity of juice during storage followed the same pattern of TAC. Other juice quality parameters such as color, pH, titratable acid, total soluble solids, antioxidant capacity and beta-carotene did not change significantly during the storage period. The results suggest that ultrasound treatment has a potential to use as an alternative non-thermal technique for traditional thermal pasteurization process for maintaining the quality of beverages prepared from fruit and vegetable juices.

Development of Hazard Analysis Critical Control Points (HACCP) and Enhancement of Microbial Safety Quality during Production of Fermented Legume Based Condiments in Nigeria

Critical control points during production of iru and okpehe , two fermented condiments, were identified in four processors in Nigeria. Physical objects such as stone and metallic objects were mixed in with the seeds; contamination resulted from wet-dehulling by foot pressing and water used in washing. The pH variation during fermentation ranged from 6.9 – 8.5 for both unfermented cotyledon and fermented condiments. Total aerobic viable count (TAVC) ranged from 1.2 – 6.2 Log 10 CFU/g. Coliforms, enterococci, staphylococci and B. cereus were pathogens detected during processing and post-processing of condiments. This indicates that the processing of condiment using traditional method is subject to microbial contamination. Dry-dehulling, cooking under pressure and inoculation of starter cultures reduced contamination and enhanced safety quality. Training of processors about Hazard Analysis Critical Control Points (HACCP), processing, environmental sanitation and personal hygiene were suggested as strategies to improve the safety of these traditional fermented condiments.

Analysis of total aerobic viable counts in raw fish by high-throughput optical oxygen respirometry.

A simple, miniaturized, and automated screening assay for the determination of total aerobic viable counts in fish samples is presented here. Fish tissue homogenates were prepared in peptone buffered water medium, according to standard method, and aliquots were dispensed into wells of a 96-well plate with the phosphorescent, oxygen-sensing probe GreenLight. Sample wells were covered with mineral oil (barrier for ambient oxygen), and the plate was monitored on a standard fluorescent reader at 30°C. The samples produced characteristic profiles, with a sharp increase in fluorescence above the baseline level at a certain threshold time, which could be correlated with initial microbial load. Five different fish species were analyzed: salmon, cod, plaice, mackerel, and whiting. Using a conventional agar plating method, the relationship between the threshold time and total aerobic viable counts load (in CFU per gram) was established, calibration curve generated, and the test was validated with 169 unknown fish samples. It showed a dynamic range of 10(4) to 10(7) CFU/g, accuracy of ± 1 log(CFU/g), assay time of 2 to 12 h (depending on the level of contamination), ruggedness with respect to the key assay parameters, simplicity (three pipetting steps, no serial dilutions), real-time data output, high sample throughput, and automation. With this test, quality of fish samples, CFU-per-gram levels, and their respective time profiles were determined.

Bruising on ostrich carcasses and the implications on the microbiology and losses in utilizable meat when removing them post-evisceration or post-chilling

Bruising on ostrich carcasses reduces meat yield. These bruises are usually removed as part of the primary meat inspection, performed directly after evisceration. Three separate studies were conducted to determine the advantages and disadvantages of removing the bruises at primary meat inspection or after overnight cooling of the ostrich carcasses (0-4 degrees C). The bruised areas were also investigated to determine their frequency and distribution and to establish the most obvious causes and possible preventative measures. The neck bruises represented 52.58% of all bruises; the high side railings of the transport vehicles being the most probable cause. Large and multiple bruising were probably from the trampling of birds lying down. It was established that trimming bruises on warm carcasses caused higher total aerobic viable counts on the trimmed surfaces than cold trimming. Cold trimming together with better management of trimming practices also led to a decrease in meat yield losses.

Assessment of the microbiological conditions of red‐meat carcasses from bacterial counts recovered by sampling via excision or swabbing with cotton wool

SummarySamples from 240 carcasses were collected from four animal species (porcine, ovine, bovine and equine). Two samples were taken from each carcass, one using the excision method (EX) and the other the wet–dry swabbing method (SW). Eight areas from each carcass were sampled. Most of the samples obtained by SW revealed total aerobic viable counts (TVC) levels of between 3.1 and 4.0 log CFU cm−2, while most of the values corresponding to excision were located between 4.1 and 5.0 log CFU cm−2. Moreover, Enterobacteriaceae (EC) counts were only detected above 3.0 log CFU cm−2 in 0.85% of the carcasses when the samples were collected by swabbing, while the excision method revealed that 13.75% of the carcasses presented EC greater than 3.0 log CFU cm−2. TVC and EC by EX revealed statistically significant differences compared to SW, while no significant linear relationship was found between carcass surface bacterial counts obtained by SW and EX.

Purity control of some Chinese crude herbal drugs marketed in Italy

The widespread use of herbal drugs, among which those coming from eastern Countries, has created a more compelling need for quality, a pre-requisite that can influence safety. In the present study, 10 Chinese crude herbal drugs marketed in Italy (Radix Ginseng, Radix Astragali, Rhizoma Coptidis, Rhizoma Atractylodis Macrocephalae, Radix Bupleuri, Radix Rehmanniae, Radix Paeoniae Alba, Pericarpium Citri Reticulatae, Radix Polygalae, Radix Salviae Miltiorrhizae) were analysed by the following purity assays: foreign matter, total ash, microbial and heavy metal contamination. Each herbal drug was purchased in Italy from three different sources: two Chinese firms and one Chinese herbal shop. Except for the heavy metal content, the tests were performed according to the European Pharmacopoeia. The presence of parasites was shown in two samples; moreover, level of ash (in three samples), lead content (in one sample) and total viable aerobic count (in one sample), were higher than the limits set by the European or Italian Pharmacopoeias. Our results, even if obtained from a small number of herbal drugs, show some purity issues and underline the importance of the quality control, particularly for this kind of products whose therapeutic value is not always demonstrated.

Effects of high-pressure treatment on the microflora of oysters (Crassostrea gigas) during chilled storage

The microbiological quality of oysters high-pressure (HP)-treated in-shell at 260 MPa for 3 min, or 500 or 800 MPa for 5 min and then stored at 2 °C, were investigated. Microbial counts after HP treatment showed that the bacterial load was reduced after treatment at all pressures to levels below the detection limit. Randomly-selected isolates from the total aerobic viable counts of untreated and HP-treated oysters after 14 days of storage were identified by the API identification system. Bacteria isolated from oysters HP-treated at 260 MPa were Shewanella putrifaciens and Pseudomonas fluorescens. For oysters HP-treated at 500 or 800 MPa, the main bacteria isolated were Pseudomonas spp. Vibrio spp. comprised 44% of the microflora in untreated oysters after storage for 14 days at 2 °C, but no Vibrio were detected in HP-treated oysters. This study confirmed that HP processing can inactivate microorganisms and delay microbial growth in chilled stored oysters. High-pressure (HP) treatment is being increasingly employed for commercial processing of oysters but no studies of the microflora of HP-treated in-shell oysters have been reported. HP treatment significantly changed the microflora of oysters and apparently has good potential for inactivation of Vibrio spp as HP treatment, in combination with adequate chilled storage, can improve the microbiological shelf-life and safety of oysters.

Analysis of total aerobic viable counts in samples of raw meat using fluorescence-based probe and oxygen consumption assay

A simple test for determining total aerobic viable counts in raw meat is presented. Homogenates of meat samples are prepared in full PBW medium, dispensed in the wells of 96-well plate together with the oxygen-sensing probe, Redlight, covered with oil and monitored on a fluorescent reader at 30 °C. The probe produces characteristic sigmoidal profiles of fluorescence reflecting depletion of sample dissolved oxygen, with onset time indicating the initial microbial load. The test provides rapid and accurate results (1 and 12 h for contamination levels of 10 8 and 10 3 cfu/g, respectively) and correlates well with the ISO:4833:2003 method ( r = 0.86), which make it useful as alternative to conventional culture methods for the quick, high throughput determination of TVC (30 °C) in meat samples.

Incidence of spore-forming bacteria in unsweetened evaporated milk brands in Nigeria

A total of forty-five samples of three most commonly consumed unsweetened evaporated milk brands purchased from retail outlets in South-western Nigeria were examined for occurrence of spore-forming bacteria. All the samples had high numbers of spore-forming bacteria of the genera Bacillus spp and Clostridium spp. with mean total aerobic viable counts of 2.15x105cfuml-1 for br and A, 0.95x105cfuml-1 for brand B and 0.69x105cfuml-1 for brand C. Total anaerobic plate counts ranged from 0.13x105 for brand C, to 0.54x105 for brand B and 1.67x105 for brand A. The organisms isolated from the three brands were identified as Bacillus cereus, Bacillus licheniformis, Bacillus coagulans, Bacillus stearothermophilus, Bacillus subtilis and Clostridium perfringens, with B. subtilis having the highest frequency of occurrence (93.33%). Samples were subjected to four different pasteurization treatments: 550C for 30 min, 800C for 15 min, 900C for 10 min and 1200C for 30 sec, to determine a more efficient process. No growth was observed on culture plates of samples pasteurized at 1200C for 30 sec, except on aerobic plates of brand A. However the milk samples treated under this regime curdled. Samples pasteurized at 800C for 15 min recorded the least counts next to samples treated at 1200C for 30 sec, without causing the samples to curdle. Keywords: Evaporated milk, pasteurization, sporeforming bacteria, viable counts. Nigerian Food Journal Vol. 25 (1) 2007: pp. 137-144

A Comparison of Wet-Dry Swabbing and Excision Sampling Methods for Microbiological Testing of Bovine, Porcine, and Ovine Carcasses at Red Meat Slaughterhouses

A comparison of wet-dry swabbing and surface tissue excision of carcasses by coring was undertaken. Samples from 1,352 bovine, 188 ovine, and 176 porcine carcasses were collected from 70 separate visits to commercial slaughterhouses operating under normal conditions. The mean total aerobic viable bacterial counts (TVCs) for all species sampled by excision was 5.36 log units, which was significantly greater than the 4.35 log units measured for swabbing. Poorly correlated linear relationships between swab- and excision-derived bacterial numbers from near-adjacent carcasses were observed for all three animal species. R2 values for least squares regressions for bovine, ovine, and porcine carcasses were 0.09, 0.27, and 0.21, respectively. The reasons why it was not possible to calculate a factor that allowed the interconversion of bacterial numbers between samples collected by each sampling method were investigated. Uncertainty associated with laboratory analyses was a contributing factor because the geometric relative standard deviations measured for TVCs were 0.174 and 0.414 for excision and swabbing, respectively. Uneven distribution of bacteria at identical sampling sites on near-adjacent carcasses on processing lines was also a contributory factor. The implications of these findings for process control verification were investigated by intensive sampling for 13 weeks in three commercial slaughterhouses. As many as 4 log units of difference in TVCs were observed in duplicate samples collected within a narrow timeframe from near-adjacent carcasses on the processing line. We conclude that it might not be appropriate to institute corrective actions in slaughterhouses on the basis of a single week's test results.

The growth of Listeria monocytogenes in cheese packed under a modified atmosphere.

The effect of modified atmosphere Packaging (MAP) on the growth of Listeria monocytogenes in mould ripened cheeses was studied at refrigeration temperatures (2-8.3 degrees C) over a storage period of 6 weeks. Control experiments in cling film with no atmospheric modification produced a lag time before growth of up to 1 week and rapid subsequent growth. MAP with a CO2 concentration of less than 20% allowed growth to occur but when O2 was incorporated; the lag time was reduced from 3 to 2 weeks and subsequent growth was also faster, producing an increase in cell numbers of 1.4 log cycles over the incubation period. N2-MAP in the absence of O2 increased the lag time to 3 weeks and slowed growth, while the inclusion of CO2 extended the lag to 3 weeks and slowed subsequent growth even more. In MAP with 80:10:10 (v/v/v) N2:CO2:O2, there was a lag period of 2-3 weeks before growth of L. monocytogenes occurred, while the total viable aerobic count (TVAC) decreased by 2-3 log cycles and the total Lactobacillus count showed little change. It was concluded that MAP was not suitable for preventing the growth of L. monocytogenes in such cheeses.

MICROBIOLOGICAL STATUS OF BEEF CARCASS MEAT IN INDONESIA

ABSTRACT The microbiological status of beef carcass meat was investigated at a traditional and a semi‐modern abattoir in Indonesia. Carcasses from the traditional abattoir were generally less contaminated than those from the semi‐modern abattoir. The average total aerobic viable bacterial count of carcasses produced at the traditional abattoir, (log10 3.62/cm2) was found to be significantly lower (p = 0.02) at the semi‐modern abattoir (log10 4.02/cm2). More than 70% of carcasses at both abattoirs were found to be positive for Escherichia coli (> 10 organisms/cm2), while Salmonellae were found on approximately 15% of carcasses at both locations.

Sensory, microbiological and chemical changes in hoki stored in ice

SummarySensory, physical, microbiological and chemical analysis were carried out on whole hoki during 21 days of storage in ice. Sensory results show that cooked hoki developed unpleasant odours and flavours after 11 days. Texture changes in cooked fish were minimal. Assessment of the raw fish provided a useful means of predicting quality of cooked fish. the total viable aerobic count on the fish surface first exceeded ICMSF standards after fish had been stored for 11 days in ice. Hypoxanthine and K value were good objective indicators of the freshness of hoki, while measurement of trimethylamine provided a means to monitor the onset of spoilage.

Bacteriological safety of cook-chill food at the Royal Free Hospital, with particular reference to Listeria

Cook-chill food prepared by the Catering Department of the Royal Free Hospital was examined over an 8-month period commencing October 1989. Total aerobic viable counts (TAVCs) were performed on 200 food specimens which were also examined for Listeria using selective enrichment culture. Ten of 200 food samples tested had TAVCs > 10 5 colony forming units (cfu) g −1, and nine of these were from non-vegetarian (meat) dishes. Although most of the food prepared by cook-chill had microbial loads within the limits recommended by current Department of Health guidelines (i.e. <10 5 cfu g −1), our findings for the non-vegetarian dishes suggest that extra caution is required when preparing such food. Listeria were not isolated from any food sample. In a survey of listeria faecal carriage, Listeria monocytogenes was isolated from only two of 100 faeces specimens obtained from patients.

The effect of selective decontamination of the digestive tract with the addition of systemic cefotaxime on the aerobic faecal flora of mice.

The administration per-orally to mice of the non-absorbable antibiotics polymyxin E, tobramycin and amphotericin B resulted in the elimination of detectable aerobic gram-negative rods from the faecal flora without affecting the total viable aerobic count. The addition of parental cefotaxime to the regime caused a fall in the number of aerobic lactobacilli and an increase in the number of enterococci. The rise was associated with the translocation of viable enterococci to the mesenteric lymph nodes and the spleen. The changes induced by cefotaxime were reversed when the antibiotic was withdrawn. Following withdrawal of all antibiotics the total aerobic faecal flora increased to above normal levels, but there was no associated diarrhoea. Attempts to implant exogenous enterobacteria into the digestive tract resulted in only low level colonization both in treated mice and in control mice. These results may have implications for the use of this antibiotic regime for selective decontamination of the digestive tract in humans, particularly those who are immunocompromised.

The relationship of bacterial numbers and types to diamine concentration in fresh and aerobically stored beef, pork and lamb

SummaryBacterial numbers and putrescine and cadaverine concentrations were measured in intact beef, pork and lamb and minced beef at retail and during aerobic chill storage at 5°C. Putrescine concentrations increased consistently with ‘total’ aerobic viable count (TAVC) but cadaverine concentrations increased only when high numbers of presumptive Enterobacteriaceae were present. Significant changes in diamine concentration did not occur until the TAVC exceeded 4.2 × 107/cm2 or g when the meat was clearly spoiled. Changes prior to the onset of spoilage were not sufficient for their use as a predictive indicator of the acceptability of the meat.

Bacterial Counts of Commercial Fish Diets

Two diets formulated and offered for commercial fish production were examined to determine their microbial burden. The total count of aerobic bacteria ranged from 103 to 107 bacteria per gram of diet. The diets contained psychrophilic and thermophilic species and up to 104 aerobic and anaerobic spore-forming bacteria per gram. Enterococci and members of the Enterobacteriaceae, including species of Salmonella, were also present. Fluorescent pseudomonads were detected in 18 of the 47 samples tested, Proteolytic, amylolytic, lipolytic, and haemolytic organisms were shown to be present in measurable numbers. The total viable aerobic count did not change markedly on storage of representative samples at 4, 20, or 30 C.

Storage life of vacuum-packed iced trout. II. Influence of radiation pasteurisation.

AbstractIrradiation of vacuum‐packed gutted trout to doses of 200, 100 and 50 krads at 0° produced no immediate effect upon the flavour of trout after cooking. The eating quality decreased steadily independent of dose in subsequent ice storage. The irradiated fish were still edible after 4 weeks' storage but their quality as a first class food was retained for about 3 weeks only. At the 200‐krad dose a total viable aerobic count of 1 million per g was not reached within 4 weeks. At doses of 100 and 50 krads this count was reached after 26 and 23 days, respectively. Non‐irradiated fish which spoiled in the third week of storage reached a count of 1 million per g after 15 days.