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1.
Mexican fermented maize dough, pozol, including traditional banana leaf-wrapped samples and material in plastic bags, was purchased. All samples were pH 4.7 to 5.7 approx. 12 h after preparation, pH declining to 3.6 to 3.9 after 6 to 9 days storage at ambient temperature. These latter samples had dry matter contents of 31% to 48% (w/w), 0.35% to 0.75% titratable acidity as lactic acid and lactic acid bacteria as predominant microbial flora at about 108 c.f.u./ml. The lactic acid bacteria included strains of Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus confusus, Lactococcus lactis and Lactococcus raffinolactis. Fungi were not found in the samples stored in plastic bags. The samples wrapped in banana leaf, however, developed a large surface mycoflora within 2 days. This included Geotrichum candidum, yeasts and moulds. The majority of the lactic acid bacteria and approx. 50% of yeasts hydrolysed starch to some extent. No Geotrichum isolate hydrolysed starch. Lactate was assimilated by all the Geotrichum isolates and by 17 of 39 yeast strains.  相似文献   

2.
Samples of camel's milk collected from different zones of Morocco were analysed to evaluate their microbiological quality and to identify predominating lactic acid bacteria (LAB). The following average colony-forming units (c.f.u.s) of aerobic total count, enterococci, faecal and total coliforms, LAB, yeasts,Staphylococcus aureus and spores of sulphite-reducing clostridia were recorded: 6.2 × 107, 2.9 × 104, 1.6 × 104, 7.0 × 106, 1.0 × 107, 3.8 × 104, 1.3 × 105 and 6.0 c.f.u./ml, respectively. The enumeration results were markedly variable and coliforms were not detected in 1 ml of some samples. Bacteriological identification revealed a definite dominance of enterococci with Enterococcus faecalis as the main representative species. Besides Enterococcus, other genera including Pediococcus (28.2%), Streptococcus (4%), Lactococcus (8%) and Leuconostoc(1%) were isolated on de Man, Rogosa and Sharp (MRS) agar.  相似文献   

3.
Silages are important feedstuffs. Homofermentative lactic acid bacterial inoculants are often used to control silage fermentation. However, some research pointed out those homofermentative lactic acid bacteria (LAB) impaired the aerobic stability of wheat, sorghum, and corn silages. Adding heterofermentative LAB can produce more acetic acid, thereby stabilizing silages during aerobic exposure. Alfalfa is difficult to ensile. The present work was to study the effects of L. buchneri (heterofermentative LAB), alone or in combination with L. plantarum (homofermentative LAB) on the fermentation, aerobic stability, bacteria diversity and ruminal degradability of alfalfa silage. After 90 days ensiling, the pH, NH3-N/TN, butyric acid content and molds counts of control were the highest. The inoculated silages had more lactic acid, acetic acid content and more lactic acid bacteria than the control. Inoculating LAB inhibited harmful microorganisms, such as Enterobacterium and Klebsiella pneumoniae. The L. buchneri L. plantarum-inoculated silage had more acetic acid and less yeasts than other three treatments (P < 0.05), and lower NH3-N/TN than control (< 0.05). The CO2 production of L. buchneri L. plantarum-inoculated silage was less than that of L. plantarum-inoculated silage (P < 0.05). Inoculating LAB in alfalfa silages can decrease pH, increase the production of lactic and acetic acids, reduce the number of yeasts and molds, and inhibit Enterobacterium and K. pneumoniae. Inoculating with L. buchneri or L. buchneri L. plantarum can improve aerobic stability of alfalfa silages. A combination of L. buchneri and L. plantarum is preferable because it enhanced alfalfa silage quality and aerobic stability.  相似文献   

4.
Controlled fermentation of maize was carried out using six strains of Lactobacillus fermentum and one strain of yeast, Saccharomyces cerevisiae, isolated from traditionally fermented maize dough as starter cultures for inoculum enrichement. The fermentations were monitored by pH, acidity, microbiological analysis and taste panel evaluation of two products, kenkey and koko, prepared from the fermented doughs. The strains of L. fermentum used as starter culture dominated the microflora during fermentation and in most inoculated doughs the required pH was attained by 24 h instead of 48 h of dough fermentation. Higher contents of lactic acid bacteria and yeasts were observed in inoculated doughs at the initial stages of fermentation but the spontaneously fermented doughs attained similar lactic acid bacteria and yeasts counts by 24 h of dough fermentation. The organoleptic quality of kenkey and koko prepared from doughs fermented with starter culture for 48 h was not significantly different from the traditional products. Kenkey prepared from doughs fermented for 24 h with starter culture were found to be unacceptable by the taste panel although similarly produced koko was acceptable.The authors are with the Food Research Institute, Council for Scientific and Industrial Research, P.O Box M 20. Accra, Ghana.  相似文献   

5.
Summary The industrial production of ethanol is affected mainly by contamination by lactic acid bacteria besides others factors that act synergistically like increased sulfite content, extremely low pH, high acidity, high alcoholic content, high temperature and osmotic pressure. In this research two strains of Saccharomyces cerevisiae PE-2 and M-26 were tested regarding the alcoholic fermentation potential in highly stressed conditions. These strains were subjected to values up to 200 mg NaHSO3 l−1, 6 g lactic acid l−1, 9.5% (w/v) ethanol and pH 3.6 during fermentative processes. The low pH (3.6) was the major stressing factor on yeasts during the fermentation. The M-26 strain produced higher acidity than the other, with higher production of succinic acid, an important inhibitor of lactic bacteria. Both strains of yeasts showed similar performance during the fermentation, with no significant difference in cell viability.  相似文献   

6.
Over a 3-week period, samples of fresh, chopped, pork meat were taken every morning and afternoon from 50 meat stalls. Microbiological examination revealed that the samples had (c.f.u./g): total microbes, 1×103 to 2.14×106; mean probable numbers of coliforms and Escherichia coli, 1.51×103 to 1.15×104; and yeasts and moulds, 0 to 1.28×104. Salmonella, found in 32 samples from 21 stalls, were serotyped as B (three samples), C1 (four) or E (25). No Campylobacter were found. Because microbial growth and/or contamination of the meat occurred during the day, samples taken in the afternoon had greater total counts (P<0.05) and contained detectable numbers of Salmonella more frequently (42% versus 22%) than those taken in the morning.The author is with the Department of Biology and Chemistry, City Polytechnic of Hong Kong, 83 Tat Chee Ave, Kowloon, Hong Kong  相似文献   

7.
The aerobic biodegradation of lindane (γ-hexachlorocyclohexane) by a consortium of acclimated bacteria from sediment at a polluted site on the Suquia River, Cordoba, Argentina, is reported. The bacteria were acclimated for 30 days under aerobic conditions, using a minimal culture medium containing lindane (0.034 mM) as sole carbon source. Growth of the bacterial consortium decreased at a lindane concentration of 1.03 mM and was totally inhibited at 2.41 mM. The consortium showed initial lindane degradation rates of 4.92×10−3, 11.0×10−3 and 34.8×10−3 mM h−1 when exposed to lindane concentrations of 0.069, 0.137 and 0.412 mM, respectively. Chloride concentration increased during aerobic biodegradation, indicating lindane mineralization. A metabolite identified as γ-2,3,4,5,6-pentachlorocyclohexene appeared during the first 24 h of biodegradation. Four different bacteria, identified as Sphingobacterium spiritivorum, Ochrobactrum anthropi, Bosea thiooxidans and Sphingomonas paucimobilis, were isolated. Pure strains of B. thiooxidans and S. paucimobilis degraded lindane after 3 days of aerobic incubation. This is the first report of lindane biodegradation by B. thiooxidans.  相似文献   

8.
The aim of this work was to study the effects of applying a strain of Propionibacterium acidipropionici, with or without Lactobacillus plantarum, on the fermentation and aerobic stability characteristics of low dry matter (DM) corn (Zea mays L.) and sorghum (Sorghum bicolor L.) silages. Corn at the dent stage and sorghum at the flowering stage were harvested. Treatments comprised control (no additives), P. acidipropionici, L. plantarum and a combination of P. acidipropionici and L. plantarum. Fresh forages were sampled prior to ensiling. Bacterial inoculants were applied to the fresh forage at 1.0×106 colony-forming units per gram. After treatment, the chopped fresh materials were ensiled in 1.5-l anaerobic glass jars equipped with a lid that enabled gas release only. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, 60 days, the silages were subjected to an aerobic stability test. The L. plantarum inoculated silages had significantly higher levels of lactic acid than the controls, P. acidipropionici and combination of P. acidipropionici and L. plantarum inoculated silages (P<0.05). The P. acidipropionici did not increase propionic and acetic acid levels of the silages. After the aerobic exposure test, the L. plantarum and combination of P. acidipropionici and L. plantarum had produced more CO2 than the controls and the silages inoculated with P. acidipropionici (P<0.05). All silages had high levels of CO2 and high numbers of yeasts and molds in the experiment. Therefore, all silages were deteriorated under aerobic conditions. The P. acidipropionici and combination of P. acidipropionici and L. plantarum were not able to improve the aerobic stability of fast-fermenting silages, because they could not work well in this acidic environment. The results showed that P. acidipropionici and combination of P. acidipropionici and L. plantarum did not improve the aerobic stability of low DM corn and sorghum silages, which are prone to aerobic deterioration.  相似文献   

9.
A yogurt culture (Streptococcus thermophilus 15HA + Lactobacillus delbrueckii subsp. bulgaricus 2-11) was studied in conditions of aerobic batch fermentation (10–40% dissolved oxygen in milk). The growth and acidification of S. thermophilus 15HA were stimulated at 20% oxygen concentration and the lactic acid process in a mixed culture was shortened by 1 h (2.5 h for the aerobic culture and 3.5 h for the anaerobic mixed culture). Streptococcus thermophilus 15HA oxygen tolerance was significantly impaired at oxygen concentrations in the milk above 30%. Though S. thermophilus 15HA was able to overcome to some extent the impact of high oxygen concentration (40%), the lactic acid produced was insufficient to coagulate the milk casein (4.0 g lactic acid l−1 in the mixed culture and 3.8 g lactic acid l−1 in the pure culture). A dramatic decrease in the viable cell count of L. delbrueckii subsp. bulgaricus 2-11 in the pure and mixed cultures was recorded at 30% dissolved oxygen. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

10.
In 2003, 50 game carcasses (ungulates) originating from one Austrian hunting ground were subject to visual examination for (fecal) contamination of the body cavities and microbiological testing of the body cavities in order to assess variations in microbial surface contamination in the season June–August compared to October–December. No carcass tested positive for the bacterial pathogens Salmonella or Listeria. Bacterial surface counts in October–December (median values: total aerobic count: 4.12 log10 colony-forming-units (cfu)/cm2; Enterobacteriaceae: 2.48 log10 cfu/cm2) were significantly lower than those in June–August (median values: total aerobic count: 5.65 log10 cfu/cm2; Enterobacteriaceae: 3.45 log10 cfu/cm2). The cooling regime (0.4 °C, 62% relative humidity) allowed no microbial growth for 96 h but was associated with weight loss of the carcasses. All carcasses had undergone a precooling phase of 8–12 h, with temperatures of 17.8±1.2 °C in the season June–August and 9.8±1.2 °C in October–December. This temperature difference was identified as the most probable effector for the observed seasonal variation. The results demonstrate the need for a continuous cool chain after evisceration of game carcasses.  相似文献   

11.
Lactic acid bacteria increased from 3.2 × 106 and 1.6 × 107 c.f.u./g (wet wt) to 2 × 109 and 1.6 × 109 c.f.u./g after 12 to 24 h of fermentation of home-produced mawè (a dough produced from dehulled maize) and commercial mawè, respectively. In commercial mawè, the yeast count increased from 1.3 × 105 to 2.5 × 107 c.f.u./g after 48 h of fermentation before decreasing, whereas in the home-produced mawè it increased from 2.5 × 104 to 3.2 × 107 c.f.u./g after 72 h of fermentation; the dominant yeasts were mainly Candida krusei, although C. kefyr, C. glabrata and Saccharomyces cerevisiae were also present. Enterobacteriaceae counts increased slightly during the initial stage ofthe fermentation, but decreased below the detection level after 24 to 48 h. Enterobacter cloacae was mostly found in commercial mawè and Escherichia coli mostly in homeproduced mawè.D.J. Hounhouigan and C.M. Nago are with the Université Nationale du Bénin, Faculté des Sciences Agronomiques, Département de Nutrition et de Sciences Alimentaires, BP 526, Cotonou, Benin; M.J.R. Nout and F.M. Rombouts are with the Agricultural University, Department of Food Science, Bomenweg 2, 6703 HD Wageningen, The Netherlands. J.H. Houben is with Utrecht University, Department of the Science of Foods of Animal Origin, Yalelaan 2, 3508 TD Utrecht, The Netherlands.  相似文献   

12.
Initial survey of four packinghouses indicated that bacterial and fungal populations on the surface of cantaloupes were significantly reduced by sanitizing procedures particularly on faecal coliforms. In this study, several combinations of disinfectants were tested in an attempt to obtain a more effective antimicrobial activity on aerobic bacteria, fungi and total coliforms. The efficacy of aqueous chlorine (200 mg l–1) and lactic acid (1.5%) on inactivation of inoculated Escherichia coli O157:H7 on cantaloupe surfaces was investigated using different temperatures (25 and 35 °C) and immersion times (1 and 10 min). Maximal log reductions were achieved with both sanitizing agents when the initial bacterial population of E. coli was 7.42 log c.f.u. cm–2. A highly significant 7.2 log reduction (P < 0.01) was obtained with a solution of lactic acid with and without Tergitol (0.3%) surfactant when cantaloupes were immersed for 10 min regardless of the temperature of the solution. Although the sanitizers caused substantial mortality, some bacterial cells remained attached at relatively low numbers on the fruit surface. The development of sanitizers more efficacious than chlorine for total elimination of this pathogen from the surface of cantaloupes is needed.  相似文献   

13.
Biofilm formation in an ice cream plant   总被引:1,自引:0,他引:1  
The sites of biofilm formation in an ice cream plant were investigated by sampling both the production line and the environment. Experiments were carried out twice within a 20-day period. First, stainless steel coupons were fixed to surfaces adjacent to food contact surfaces, the floor drains and the doormat. They were taken for the analysis of biofilm at three different production stages. Then, biofilm forming bacteria were␣enumerated and also presence of Listeria monocytogenes was monitored. Biofilm forming isolates were selected on the basis of colony morphology and Gram’s reaction; Gram negative cocci and rod, Gram positive cocci and spore forming isolates were identified. Most of the biofilm formations were seen on the conveyor belt of a packaging machine 8 h after the beginning of the production, 6.5 × 103 cfu cm−2. Most of the Gram negative bacteria identified belong to Enterobacteriaceae family such as Proteus, Enterobacter, Citrobacter, Shigella, Escherichia, Edwardsiella. The other Gram negative microflora included Aeromonas, Plesiomonas, Moraxella, Pseudomonas or Alcaligenes spp. were also isolated. Gram positive microflora of the ice cream plant included Staphyloccus, Bacillus, Listeria and lactic acid bacteria such as Streptococcus, Leuconostoc or Pediococcus spp. The results from this study highlighted the problems of spread of pathogens like Listeria and Shigella and spoilage bacteria. In the development of cleaning and disinfection procedures in ice cream plants, an awareness of these biofilm-forming bacteria is essential for the ice cream plants.  相似文献   

14.
Two separate 4 (bacterial concentrations)×6 (yeast concentrations) full factorial experiments were conducted in an attempt to identify a novel approach to minimize the effects caused by bacterial contamination during industrial production of ethanol from corn. Lactobacillus plantarum and Lactobacillus paracasei, commonly occurring bacterial contaminants in ethanol plants, were used in separate fermentation experiments conducted in duplicate using an industrial strain of Saccharomyces cerevisiae, Allyeast Superstart. Bacterial concentrations were 0, 1×106, 1×107 and 1×108 cells/ml mash. Yeast concentrations were 0, 1×106, 1×107, 2×107, 3×107, and 4×107 cells/ml mash. An increased yeast inoculation rate of 3×107 cells/ml resulted in a greater than 80% decrease (P<0.001) and a greater than 55% decrease (P<0.001) in lactic acid production by L. plantarum and L. paracasei, respectively, when mash was infected with 1×108 lactobacilli/ml. No differences (P>0.25) were observed in the final ethanol concentration produced by yeast at any of the inoculation rates studied, in the absence of lactobacilli. However, when the mash was infected with 1×107 or 1×108 lactobacilli/ml, a reduction of 0.7–0.9% v/v (P<0.005) and a reduction of 0.4–0.6% v/v (P<0.005) in the final ethanol produced was observed in mashes inoculated with 1×106 and 1×107 yeast cells/ml, respectively. At higher yeast inoculation rates of 3×107 or 4×107 cells/ml, no differences (P>0.35) were observed in the final ethanol produced even when the mash was infected with 1×108 lactobacilli/ml. The increase in ethanol corresponded to the reduction in lactic acid production by lactobacilli. This suggests that using an inoculation rate of 3×107 yeast cells/ml reduces the growth and metabolism of contaminating lactic bacteria significantly, which results in reduced lactic acid production and a concomitant increase in ethanol production by yeast.  相似文献   

15.
Kluyveromyces marxianus NRRL Y-1196 produced the highest inulinase activity (38 U/mg protein) of six yeasts examined after 24 h growth in sauerkraut brine in shaking flasks at 30°C with 0.3% inulin as an enzyme inducer. The enzyme was recovered by acetone fractionation, with a yield of 81%. It had maximum activity at pH 4.4 and 55°C with K m values for inulin and sucrose of 3.92 mm and 11.9 mm, respectively. The yeast raised the pH from 3.4 to above 7.0, using all the lactic acid in the brine. Growth of K. marxianus in sauerkraut brine with a small amount of inulin may usefully decrease the BOD and concomitantly produce inulinase.The authors are with the Department of Food Science and Technology, Cornell University, Geneva, New York 14456, USA  相似文献   

16.
The coffee fermentation microflora were rich and mainly constituted of aerobic Gram-negative bacilli, with Erwinia and Klebsiella genuses at the highest frequencies. The best population increase was observed with lactic acid bacteria and yeasts, whereas those microorganisms that counted on a pectin medium remained constant during the fermentation step. Qualitatively, lactic acid bacteria belonged mainly to Leuconostoc mesenteroides species but the others microflora were relatively heterogeneous. The microorganisms isolated on pectin medium were Enterobacteriaceae, identified as Erwinia herbicola and Klebsiella pneumoniae, not reported as strong pectolytic strains. Throughout coffee fermentation, 60% of the simple sugars were degraded by the total microflora and not specifically by pectolytic microorganisms. Received: 21 August 2000 / Accepted: 25 September 2000  相似文献   

17.
Idli is a traditional cereal/legume-based naturally fermented steamed product with a soft and spongy texture which is highly popular and widely consumed as a snack food item in India. The predominant fermentation microflora comprises lactic acid bacteria and yeasts and causes an improvement in the nutritional, textural and flavour characteristics of the final product. The flavour profile of idli batter prepared with initial levels of 2 × 104 c.f.u. g−1 of Candida versatilis CFR 505 and 2 × 101 c.f.u. g−1 of Pediococcus pentosaceus CFR 2123 in 500 g idli batter, packed in polyester polylaminate pouches and stored at 30 ± 2 °C was periodically analysed by GC-MS. The desirable flavour compounds such as ketones, diols and acids were found to be present upto 8 days of storage, whereas undesirable flavours like sulphurous and oxazolidone compounds, ethanone and thiazole appeared in the batter subsequent to 6 days of storage. The sensory attributes of idlis (final product) prepared from the stored batter related well to the determined flavour profile. The present study appeared to indicate that the flavour profile of traditional fermented foods can be a reliable qualitative and quantitative parameter for objective assessment. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
We isolated aerobic and anaerobic facultative bacteria inhabiting the crop of adult Dusky-billed Parrotlets (Forpus modestus). We looked for bacteria capable of hydrolyzing starch, the most abundant polysaccharide in seeds. We compared our results with bacteria isolated from the crop of three species of doves with granivorous–frugivorous diet and three carnivore birds. Forpus modestus has 107–108 of colony formation units (CFU); these values were higher by one to three orders of magnitude compared with those observed in the other species studied. Bacillus pumilus, one of the most abundant bacteria isolated in F. modestus (6.03 × 106 CFU), was capable of hydrolyzing starch. We found higher diversity and abundance of bacteria in granivorous than in carnivorous birds or birds without a developed crop. Additionally, we found yeasts in the three species of doves. These findings suggest microbial activity in the crop, although its importance in food digestion needs to be determined.  相似文献   

19.
We investigated the intestinal microflora of coastal fish including Takifugu niphobles using both culture techniques and library cloning. As a result, the numbers of bacteria appeared on agar media were 1.0 × 104 to 1.4 × 109 CFU/g (colony forming units/gram), whereas those of total bacteria stained with 4′,6-diamidino-2-phenylindole were 4.7 × 1010 to 1.9 × 1011 cells/gram, irrespective of different fish species. In addition, the culture technique showed that the intestinal microflora in all specimens was mainly composed of the genus Vibrio. In contrast, the direct count method showed that spirochaetes with length of 2.5-4.5 μm were present in the intestinal contents of T. niphobles at high densities, whereas such bacteria could not be detected in those of other fish species. Library cloning yielded the sequences of 16S rRNA genes that were divided into seven taxonomic categories of bacteria including Actinobacteria, Bacilli, Clostridia, Gammaproteobacteria, Mollicutes, Spirochaetes and an unclassified bacterial group. These results demonstrate that the molecular diversity of the intestinal bacteria in T. niphobles based on the clone library method reflects the direct observation by fluorescence microscopy to some extent.  相似文献   

20.
Ngari, hentak and tungtap are traditional fermented fish products of North-East India. Eighteen samples of ngari, hentak and tungtap were collected and were analysed for microbial load. Lactic acid bacteria, endospore-forming rods, yeasts and aerobic mesophilic counts ranged from 4.0 to 7.2, 3.3–4.6, <1–3.5 and 4.3–7.3 log c.f.u./g, respectively. Lactic acid bacteria were identified as Lactococcus lactis subsp. cremoris, Lactococcus plantarum, Enterococcus faecium, Lactobacillus fructosus, Lactobacillus amylophilus, Lactobacillus coryniformis subsp. torquens and Lactobacillus plantarum. Endospore-forming rods were identified as Bacillus subtilis and Bacillus pumilus, aerobic coccal strains were identified as Micrococcus. Yeasts were identified as species of Candida and Saccharomycopsis. Pathogenic contaminants were detected in all samples, however, none of the sample contained more than 102 c.f.u./g of Bacillus cereus, 103 c.f.u./g of Staphylococcus aureus and enterobacteriaceae population, respectively. Enzymatic and antimicrobial activities of the isolates were tested. None of the strains produced biogenic amines in the method applied. Most strains of LAB had a high degree of hydrophobicity, indicating their ‘probiotic’ characters. This study has demonstrated the microbial diversity within the species of lactic acid bacteria, Bacillus and yeasts. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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