Identification of Enterobacteriaceae from washed and unwashed commercial shell eggs

To evaluate the effect of processing on the safety and quality of retail shell eggs, a storage study was conducted with unwashed and commercially washed eggs. This work demonstrated that commercial processing decreased microbial contamination of eggshells. To know which species persisted during storage on washed or unwashed eggs, Enterobacteriaceae isolates were selected and identified biochemically. For each of three replications, shell eggs were purchased from a commercial processing plant, transported back to the laboratory, and stored at 4 degrees C. Once a week for 6 weeks, 12 eggs for each treatment (washed and unwashed control) were rinsed in sterile phosphate-buffered saline. A 1-ml aliquot of each sample was plated onto violet red bile glucose agar with overlay and incubated at 37 degrees C for 24 h. Following incubation, plates were observed for colonies characteristic of the family Enterobacteriaceae. A maximum of 10 isolates per positive sample were streaked for isolation before being identified to the genus or species level using commercially available biochemical strips. Although most of the isolates from the unwashed control eggs belonged to the genera Escherichia or Enterobacter, many other genera and species were identified. These included Citrobacter, Klebsiella, Kluyvera, Pantoea, Providencia, Rahnella, Salmonella, Serratia, and Yersinia. Non-Enterobacteriaceae also recovered from the unwashed egg samples included Xanthomonas and Flavimonas. Very few washed egg samples were contaminated with any of these bacteria. These data provide useful information on the effectiveness of processing in removing microorganisms from commercial shell eggs.     

Impact of commercial processing on the microbiology of shell eggs

Shell egg microbiology has been studied extensively, but little information is available on how modern U.S. processing conditions impact microbial populations. As regulations are being drafted for the industry, such information can be important for determining processing steps critical to product safety. Five different shell egg surface microbial populations (aerobic bacteria, yeasts and molds, Enterobacteriaceae, Escherichia coli, and Salmonella) were monitored at 12 points along the processing line (accumulator, prewash rinse, washer 1, washer 2, sanitizer, dryer, oiler, scales, two packer head lanes, rewash entrance, and rewash exit). Three commercial facilities were each visited three times, a total of 990 eggs were sampled, and 5,220 microbiological samples were subsequently analyzed. Although variations existed in concentrations of microorganisms recovered from each plant, the patterns of fluctuation for each population were similar at each plant. On average, aerobes, yeasts and molds, Enterobacteriaceae, and E. coli prevalence were reduced by 30, 20, 50, and 30%, respectively, by the end of processing. The microbial concentrations (log CFU per milliliter) in the egg rinse collected from packer head lanes were decreased by 3.3, 1.3, 1.3, and 0.5, respectively, when compared with those of rinses collected from eggs at the accumulator. Salmonella was recovered from 0 to 48% of pooled samples in the three repetitions. Higher concentrations of Salmonella were recovered from preprocessed than from in-process or ready-to-pack eggs. These data indicate that current commercial practices decrease microbial contamination of egg shell surfaces.     

Identification of yeasts isolated from commercial shell eggs stored at refrigerated temperatures

Yeasts and molds can grow on or in eggs, causing spoilage. Washed and unwashed eggs (treatments) were collected aseptically on three separate days (replications) from a commercial processing facility and stored for 10 weeks at 4 degrees C. Ten eggs from each treatment were sampled weekly (110 eggs per treatment per replication). Yeasts and molds were enumerated from external shell rinses by plating onto acidified potato dextrose agar. Yeast colonies were picked randomly and stored for subsequent identification by gas chromatographic analysis of fatty acid methyl esters using the MIDI Microbial Identification System. Of 688 isolates analyzed, 380 were identified to genus or species. Genera identified by this method included Candida, Cryptococcus, Hansenula, Hyphopichia, Metschnikowia, Rhodotorula, Sporobolomyces, and Torulaspora. Candida spp. accounted for 84.5% (321 of 380) of the isolate identifications. Candida famata was the most prevalent species (n = 120), followed by Candida lusitaniae (n = 38). A group of 20 isolates was subjected to molecular or biochemical analyses for comparison with the MIDI results. Biochemical tests were performed using automatic and mini systems. Results of biochemical tests and ribosomal DNA sequencing were in agreement for 11 of the isolates, but only 7 of the 20 MIDI-identified isolates were in agreement with the sequencing results. C. famata, an anamorph of Debaryomyces hansenii var. hansenii, was the most commonly identified isolate by all methods. These data indicate that there was limited correlation between results obtained with the MIDI system and the information obtained from molecular databases. However, both systems were able to correctly identify C. famata, the species most often isolated throughout egg storage.     

CHANGES IN THE MICROFLORA OF PACKAGED FRESH BROCCOLI

Changes in the microflora of fresh broccoli shrink-wrapped in film, sealed in gas-flushed film pouches, or stored on ice in cardboard crates and held at 1°C were analyzed. Growth trends for total aerobes, psychrotrophs, yeast/molds, members of Enterobacteriaceae, and lactic acid bacteria did not differ significantly between the packaging treatments (p ≤ 0.05). However, populations of total aerobes in unpackaged broccoli in its final week of storage (week 6) were significantly greater than that of packaged broccoli at week 6. Samples packaged in film remained higher in quality 2 to 3 weeks longer than control samples. Yellowing was the most obvious defect.     

Correlation of eggshell strength and Salmonella enteritidis contamination of commercial shell eggs

Shell quality has been identified as a heritable trait that can be manipulated by genetic selection. Previous research has concluded that many methods of determining shell quality produce variable results. With the development of newer, more precise measuring technologies, shell strength can now be assessed in a consistent, objective fashion. A research project was conducted to determine what role shell strength might play in affecting external Salmonella Enteritidis contamination of egg contents. Visibly clean eggs were collected from an in-line shell egg-processing facility at the accumulator. Eggs were inoculated by dipping in a concentrated suspension of nalidixic acid-resistant Salmonella Enteritidis. After storage, eggs were assessed for shell strength and both external and internal Salmonella Enteritidis contamination. In the first study, there was a significant difference (P < 0.05) in shell strength among the three replicates. No differences between treatments were found for shell strength or Salmonella Enteritidis contamination of contents. In the second study, there were no replicate differences for any of the monitored factors. When rinsate and content samples were enriched, 100% of the rinsates were positive for Salmonella Enteritidis. No content samples were shown to be contaminated with Salmonella Enteritidis during direct plating, but 3 to 5% of the samples from each replicate were positive after enrichment. Correlation analysis of the results from each study found only weak correlations between shell strength and Salmonella Enteritidis contamination on eggshell surface or contents. Within the range of shell strengths recorded in this study, the correlation analysis suggests that shell strength does not play a major role in Salmonella Enteritidis contamination. Further work with eggs that represent a greater range of shell strengths could provide a clearer indication of the interaction of shell strength and Salmonella Enteritidis contamination.     

Shell rinse and shell crush methods for the recovery of aerobic microorganisms and enterobacteriaceae from shell eggs

Recovery of bacteria from shell eggs is important for evaluating the efficacy of processing and the quality and safety of the final product. Shell rinse (SR) techniques are easy to perform and widely used. An alternative sampling method involves crushing and rubbing the shell (CR). To determine the most appropriate method for recovering microorganisms from shell eggs, 358 shell eggs were collected from a commercial egg processor and sampled by SR and CR techniques. Total aerobic mesophiles and Enterobacteriaceae were enumerated on plate count and violet red bile glucose agar plates, respectively. Unwashed, in process, and postprocess eggs were evaluated in the study. Aerobic microorganism prevalence for eggshells sampled was similar for both methods (approximately 100%), but the log CFU per milliliter values were higher in the SR than the CR samples (3.2 and 2.2, respectively). Average Enterobacteriaceae recovery was similar for both methods (45 versus 40% for the SR and CR methods, respectively) when all eggs were considered together. This population was detected more often by SR when unwashed eggs were sampled (90 versus 56% for the SR and CR methods, respectively), equally by SR and CR for in-process eggs (30 versus 29.3% for the SR and CR methods, respectively), but more often by CR for postprocess eggs (10 versus 36% for the SR and CR methods, respectively). The SR technique was easier to perform and recovered larger numbers of aerobic organisms, particularly for unwashed eggs. However, the CR technique was more efficient for recovery of Enterobacteriaceae from postprocess eggs. Stage of shell egg processing may be an important consideration when choosing egg sampling methods.     

Effects of electron-beam irradiation on the shelf life, microbial populations and sensory characteristics of summer truffles (Tuber aestivum) packaged under modified atmospheres

The effects of two doses of electron-beam irradiation (1.5 kGy and 2.5 kGy) on the microbial populations (total mesophilic aerobes, Pseudomonas genus, Enterobacteriaceae family, molds and yeasts) and sensory characteristics of Tuber aestivum packaged under modified atmospheres were monitored immediately after treatment, and weekly during 42 days of storage at 4 °C. Treatment with 1.5 and 2.5 kGy reduced the pseudomonads populations by 4.3 and 5.5 logs, respectively. Enterobacteriaceae counts decreased by 5.4 logs with the 1.5 kGy dose and counts below the detection limit (<1.0 log cfu/g) were obtained with the 2.5 kGy dose. Lactic acid bacteria and yeasts were less affected by the ionizing radiation treatments and they became the dominant microbial populations throughout storage with microbial counts up to 7.1 log cfu/g. The carbon dioxide levels inside the packages containing irradiated truffles were lower than those of the non-irradiated ones, suggesting a decrease in the respiration rate of the treated ascocarps. The treatments with 1.5 and 2.5 kGy e-beam did not negatively affect the sensory characteristics of truffles, but a visible superficial yeast growth was detected in truffles irradiated with 1.5 kGy at the end of their shelf life (day 28). Treatment with 2.5 kGy e-beam has prolonged the shelf life to 42 days, compared with 21 days for the untreated samples.     

CHANGES IN THE MICROFLORA OF PACKAGED FRESH TOMATOES

Fresh tomatoes were shrink-wrapped in film, sealed in gas-flushed film pouches, or stored in cardboard packing crates. All samples were stored at 13°C, and changes in populations of total aerobes, psychrotrophs, yeasts and molds, members of Enterobacteriaceae, and lactic acid bacteria followed. Shrink-wrapping and gas-packaging increased aerobic counts over no packaging, and selected for yeasts and molds. Shrink-wrapping additionally selected for lactic acid bacteria. The greatest number of psychrotrophs but the least number of yeasts and molds developed in unpackaged tomatoes. Shrink-wrapped and gas-packaged tomatoes remained unspoiled at least 6 weeks whereas controls spoiled in 4 weeks.     

An assessment of the microbiological risks involved with egg washing under commercial conditions

The potential benefits of washing eggs is offset by a historical perception in the European Union that wetted eggs are prone to spoilage and water loss. This study describes the effects of spray jet washing under various processing conditions to shell surface counts of Salmonella and the presence of bacteria in egg contents. Experiments used eggs that were contaminated with Salmonella Enteritidis PT4 or Salmonella Typhimurium DT104 before cuticle hardening. Washing of contaminated eggs under optimum conditions resulted in a more than 5-log reduction of Salmonella counts from the shell surface. Salmonella was not isolated from the yolk or albumen of any egg washed by the optimal protocol, suggesting that when properly controlled, egg washing did not cause Salmonella to enter the contents. However, contamination did arise if strict control was not maintained over the wash and rinse water temperatures. Both Salmonella Enteritidis and Salmonella Typhimurium were shown to enter the egg contents when water temperatures were lowered, indicating that strict temperature control must be maintained in order to prevent the ingress of Salmonella into egg contents. Other washing machine parameters that were investigated did not significantly affect Salmonella entry into the egg contents but influenced shell surface kill levels to varying degrees.     

Pathogen prevalence and microbial levels associated with restricted shell eggs

Restricted shell eggs that do not meet quality standards for retail but maintain acceptable quality for inclusion in further processed eggs are often diverted to further processing. A study was conducted to characterize the microbiological populations present on and in these eggs. On a single day, restricted eggs were collected from three shell egg processing plants a total of three times (replicates). Six shells or egg contents were combined to create a pool. Ten pools of shells and contents were formed for each plant per replicate. Shells and membranes were macerated in 60 ml of diluent. Contents were stomacher blended to form a homogeneous mixture. Total aerobic microorganisms and Enterobacteriaceae were enumerated. The prevalence of Salmonella, Campylobacter, and Listeria was determined by cultural methods. Average aerobic counts were 4.3 log CFU/ml for the shells and 2.0 log CFU/ml for the contents. There were plant x replicate differences for both (P < 0.05 and P < 0.01, respectively). The average Enterobacteriaceae level associated with the shell was 2.4 log CFU/ml and less than 0.1 log CFU/ml for the egg contents, with 36.7% of the samples being positive. One shell sample (0.5% of total samples) was Campylobacter positive. Two shell samples (1.1% of total samples) were Salmonella positive. Twenty-one percent of samples were positive for Listeria (33 shells and 5 contents). Although current pasteurization guidelines are based on Salmonella lethality, the results of this study reiterate the need to revisit the guidelines to determine the effectiveness for other pathogenic species.     

EFFECT OF RAPID COOLING ON THE GROWTH AND PENETRATION OF SALMONELLA ENTERITIDIS INTO EGG CONTENTS

Shell eggs were inoculated internally with approximately 10 cells of Salmonella enterica serovar enteritidis (S. enteritidis) and subjected to three different cooling treatments. Eggs were cooled from an initial temperature of 27C to approximately 7.2C. After cooling, eggs were stored at approximately 7.2C for 36 days, or stored at 5.7–9.5C for 30 days plus 6 days at 37C to simulate temperature abuse. Rapid cooling and subsequent storage of eggs at approximately 7.2C inhibited the growth of S. enteritidis in eggs. Slow cooling, and/or temperature abuse promoted growth of S. enteritidis in eggs. The penetration study indicated that rapid cooling and subsequent storage at 7.2C for 30 days did not affect the penetration of S. enteritidis into egg contents. The S. enteritidis isolated from the eggshell with shell membranes was significantly higher (P < 0.05) than from the internal egg contents, indicating that most of the S. enteritidis cells were trapped within the shell pores and/or shell membranes.     

EGG QUALITY AS AFFECTED BY STORAGE AND HANDLING METHODS

The quality and shelf-life of fresh eggs were studied under simulated climatic conditions as found in Kuwait. Three groups of eggs (unwashed, washed, and washed and oil treated) were used. The treated eggs were stored at 5°, 25°, 37° and 42°C. Internal and external quality and sensory evaluation of the eggs stored up to 75 days were determined. The quality of the unwashed and washed eggs stored at 37°C and 42°C deteriorated rapidly while the wash and oil treatment extended shelf-life but decreased in quality to C over a period of time. The percent weight loss in the oil treated eggs at all temperatures was about 0.6% while the washed and unwashed lost more depending upon the temperature and storage time. All parameters studied for interior quality showed that oil treated eggs were significantly better than untreated eggs even at 42°C. Sensory evaluation on boiled eggs indicated that changes in flavor and overall quality for untreated eggs stored at high temperatures were obvious while little change in texture was observed. It was concluded that under Kuwaiti conditions eggs should be oil treated directly after collection and stored at or below 25°C so that the quality and shelf-life can be extended significantly.     

Comparison of the microflora on organically and conventionally grown spring mix from a California processor

Considerable speculation has occurred concerning the potential for higher numbers of foodborne pathogens on organically grown produce compared with produce not grown organically. The microflora composition of spring mix or mesclun, a mixture of multiple salad ingredients, grown either by organic or conventional means was determined. Unwashed or washed spring mix was obtained from a commercial California fresh-cut produce processor who does not use manure in their cultivation practices. Fifty-four samples of each type of product were supplied over a 4-month period. Analysis included enumeration of total mesophiles, psychrotrophs, coliforms, generic Escherichia coli, lactic acid bacteria, yeasts, and molds. In addition, spring mix was analyzed for the presence of Salmonella and Listeria monocytogenes. The mean populations of mesophilic and psychrotrophic bacteria, yeasts, molds, lactic acid bacteria, and coliforms on conventionally grown spring mix were not statistically different (P > 0.05) from respective mean populations on organically grown spring mix. The mean population of each microbial group was significantly higher on unwashed spring mix compared with the washed product. Of the 14 samples found to contain E. coli, eight were from nonwashed conventional spring mix, one was from washed conventional spring mix, and four were from nonwashed organic spring mix. Salmonella and L. monocytogenes were not detected in any of the samples analyzed.     

Factors affecting the occurrence of Bacillus cereus in liquid whole egg

Bacillus cereus was isolated from various sites at an egg laying station, from raw and pasteurized liquid whole egg and from bakery and retail products made with liquid whole egg. Melange and melange buckets (both washed and unwashed) had particularly frequent contamination, as did samples from the raw mix and holding tanks. After pasteurization, B. cereus was isolated less readily, suggesting that most of the initial contamination was in the form of vegetative cells. Spores produced by the isolates on laboratory media resisted heating at 80°C for 60 min and treatment with disinfectants. The results indicate that more rigorous exclusion of badly cracked and contaminated eggs, coupled with reduction in the use of melange and increased cleaning and disinfection, particularly at the egg laying station, would reduce the levels of B. cereus in the pasteurized liquid whole egg.     

Eggshell factors influencing eggshell penetration and whole egg contamination by different bacteria, including Salmonella enteritidis

Trans-shell infection routes and whole egg contamination of 7 selected bacterial strains; Staphylococcus warneri, Acinetobacter baumannii, Alcaligenes sp., Serratia marcescens, Carnobacterium sp., Pseudomonas sp. and Salmonella enteritidis, recovered from egg contents, were studied. The first objective was to correlate bacterial eggshell penetration with various eggshell characteristics and bacterial strains. An agar approach was used to assess the eggshell penetration. The second objective was to assess the contamination of whole eggs with the bacterial strains; whole intact eggs were used in this case. The intact shells of agar-filled and whole eggs were inoculated with 10(3) -10(4) cfu of the selected strains. During 3 weeks storage at 20 degrees C and 60% relative humidity, the bacterial eggshell penetration was regularly monitored. The whole egg contamination was only analyzed after 3 weeks. The eggshell characteristics such as area eggshell, shell thickness and number of pores did not influence the bacterial eggshell penetration. For each individual bacterial strain the mean cuticle deposition was lower for penetrated compared to non-penetrated eggshells. For the individual strain Carnobacterium sp. and for the global results of all strains this difference was statistical significantly. The whole egg contamination was not influenced by neither the area of the eggshell nor the porosity of the eggshell. The results of the agar approach indicate that the Gram-negative, motile and non-clustering bacteria penetrated the eggshell most frequently; Pseudomonas sp. (60%) and Alcaligenes sp. (58%) were primary invaders followed by S. enteritidis (43%). All selected strains were able to penetrate; penetration was observed most frequently after ca. 4-5 days. Particularly S. enteritidis was a primary invader of whole eggs: the membranes and/or the content of 32% of the whole eggs was contaminated. The remaining bacterial eggshell contamination with the selected strain was determined after 3 weeks storage. Penetrated eggshells and contaminated whole eggs showed a significantly higher bacterial contamination on the eggshell compared to non-penetrated eggshells and non-contaminated whole eggs respectively (global results of all strains). The influence of hen age on bacterial eggshell penetration and egg content contamination was not significant. While the agar approach is suitable to study the influence of the eggshell characteristics on the bacterial eggshell penetration, the intact egg approach gives an estimation of the penetration of the shell followed by the probability of survival and migration in whole eggs.     

Assessment of the microbiological conditions of tails, tongues, and head meats at two beef-packing plants.

Newly skinned tails of beef carcasses at two packing plants were similarly contaminated with total aerobes and with coliforms that were largely Escherichia coli at log mean numbers about 3.5/cm2 and 4.5/100 cm2, respectively. The log mean numbers of aerobes and coliforms on the skinned tails after washing at plant A were, respectively, 1 and 2 log units less than the numbers on the newly skinned tails. At plant B, the log mean numbers of aerobes on skinned and on washed tails were similar while the log mean numbers of E. coli on washed tails were only about 1 log unit less than the numbers on skinned tails. Cooling of tails on racks in a chiller at plant B reduced the log mean numbers of E. coli by about 1 log unit but did not reduce the numbers of total aerobes. Tongues in the heads of carcasses at both plants were similarly contaminated with total aerobes and with coliforms that were largely E. coli at log mean numbers of about 4.5/cm2 and 4.5/100 cm2, respectively. The log mean numbers of aerobes on and the log total number of E. coli recovered from washed tongues were, respectively, about 2 and 4 log units less than for unwashed tongues at plant A and about 1 and 3 log units less than for unwashed tongues at plant B. The log mean numbers of aerobes and E. coli on washed cheeks and lips were both about 2 log units less than the numbers on unwashed tongues at both plants. With appropriate collection and washing procedures, the microbiological conditions of beef tails, tongues, and head meats can apparently be comparable to those of primal cuts and manufacturing beef at the times that the products are packed.     

Salmonella serovars isolated from table eggs: An overview

Salmonellosis can be acquired through consumption of infected raw or undercooked eggs. The European Commission has set criteria to control Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) infections in laying flocks, to reduce the risk of contaminated eggs entering the food chain. SE is considered the serovar mostly implicated in Salmonella egg related food poisoning, for its peculiar ability to contaminate the egg contents through vertical transmission. Other Salmonella serovars (SO) and ST generally contaminate eggs externally, and are found in the egg contents following penetration through the eggshell. A review of the information available on egg contamination by SE, ST and SO is presented, followed by a collation of the surveys investigating table egg contamination at retail. Where available, information on the serovars identified in these surveys and Salmonella contamination of the egg (shell, contents or both) is detailed. SE appears to play a major role in egg contamination. Isolation of ST from eggs is not frequent, and appears to be mostly on the eggshells. In the majority of the studies, more samples were positive for SO than for ST. In some studies, one individual serovar exceeded ST. The data presented in this article shows how ST is not often isolated from table eggs and that contamination of table eggs with SE and SO is more frequent.     

Microbiological quality of retail poultry carcasses in Spain.

A total of 40 eviscerated and refrigerated chicken carcasses were collected from five retail outlets (three supermarkets and two poulterers' shops) in León (Spain). The level of microorganisms on chicken carcasses was assessed using the excised breast-skin technique. Mean counts (log10 CFU/g) of psychrotrophs, pseudomonads, fluorescent pseudomonads, enterococci, Micrococcaceae, Staphylococcus aureus, and yeasts and molds were 4.84, 4.11, 3.32, 2.72, 3.80, 3.67, and 2.99, respectively. A significant correlation coefficient was found between pseudomonads and fluorescent pseudomonad counts (r = 0.827; P < 0.001) and between Micrococcaceae and S. aureus counts (r = 0.915; P < 0.001). Levels of psychrotrophs, pseudomonads, fluorescent pseudomonads, and yeasts and molds were significantly (P < 0.05) higher in supermarkets than in poulterers' shops, possibly due to the longer period of time the carcasses spent in the supermarkets (between 1 and 2 days, as opposed to only 4 to 16 h in the case of poulterers' shops). Carcasses from poulterers' shops showed higher (P < 0.05) counts of enterococci. Micrococcaceae, and S. aureus, which suggests higher storage temperatures in these outlets. Only S. aureus counts (especially those from poulterers' shops) exceeded the established values in the microbiological criteria for poultry meat consulted.     

COMPARISON OF A PEROXIDASE-CATALYZED SANITIZER WITH OTHER EGG SANITIZERS USING A LABORATORY-SCALE SPRAYER

Microbial and foodborne pathogen contamination of eggs continues to represent an important public health concern. The goal of this study was to compare the efficacy of spraying shell eggs with PCC (peroxidase-catalyzed compound, Enzodine ^TM, Symbollon Corporation, Sudbury, MA) with that of other sanitizers in the reduction of surface microbial contamination using a laboratory-scale sprayer apparatus. Treatments were distilled-deionized water, PCC, chlorine (200 ppm), and quaternary ammonium (QA). Each egg was sprayed with 150 mL of the treatment over a 1 min period while being rotated at approximately 150 revolutions per min. Enumeration of aerobic plate populations indicated that all treatments (distilled-deionized water, chlorine, PCC, and QA) significantly reduced the viable aerobic bacterial populations and Salmonella typhimurium when compared to the nonsprayed dry egg control. Spraying eggs with PCC resulted in a 6 logarithmic reduction in viable S. typhimurium populations on egg shell surfaces. Unlike results found with aerobic bacterial populations, PCC was not as effective in reducing levels of S. typhimurium to the extent of the chlorine and QA treatments (greater than 6 logarithmic reduction) but greater than 3 logarithmic reduction was observed with PCC as compared to distilled-deionized water. This study suggests that PCC may be a viable alternative to chlorine and QA in the reduction of bacterial populations on shell egg surfaces and can be applied as a spray on egg shell surfaces.     

GROWTH OF FUNGAL CONTAMINATION IN FERMENTED MILK CONTAINING BIFIDOBACTERIA AND Lactobacillus addophttus

The isolation, enumeration and identification of yeasts and molds were carried out in fifty samples of commercial fermented milk containing bifidobacteria and Lactobacillus acidophilus. The determinations were made at 2, 10, 17, 24, 28, 31, 36, 42, 51 and 84 days of refrigerated storage (7C). Fungal contamination was observed in 94% of the samples. The presence of yeasts was verified in all cases whilst the appearance of filamentous molds was occasional. In all the cases where fungal contamination was established, there was a steady presence of Candida krusei, which proved to be the only yeast identified. The filamentous molds detected were identified as Geotrichum candidum. The level of contamination by yeasts underwent a clear progression during the whole storage period and this evolution was related to the acidity level. The contamination is attributable to hygiene deficiencies during packaging.