Science topic

Food Microbiology - Science topic

The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept.
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Hello,
I am running a plant based yoghurt fermentation (10 - 50kg bucket/tank batch) but after 16h the pH drop is quite poor (stops at 5.4 - 5.8). The yoghurt base is UHT treated before and consists of pea & faba bean protein, oil, sucrose, dextrose and salt and the culture is S.thermophilus and L. delbrueckii. It works on a benchtop level (300g jars) and then pH drops to 4.4. What could be the reason for failed acidification in scale up? Could it be that the heat is not evenly distributed and the core does not get to the target temperature? Or perhaps the medium could be supplemented with some extra nutrients for ST and LB to enhance growth?
Thanks in advance for your help!
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I have analyzed PT a sample from an external PT provider, the matrix was skimmed milk powder (lyophilized), and the required tests were: aerobic plate count, Enterobacteriaceae count, Coliforms count, and E. coli count. the results that I got were questionable; the counts were much lower than the assigned values (lower by an order of magnitude). I tried to investigate the possible reasons for what happened; I check media preparation, incubators temperature, sterility checks of 3M Petrifilms and all were good. the problem that the number of CFUs capable of growing on plates was much lower than the real number so I suspect that the problem happened during the delivery of samples, although the sample was delivered with two other samples and their results were good. Anyone has been through this? Any other possible explanations?
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Hi there, to my opinion, although the result si "only" questionable ( as opposed to unsatisfactory), you should run a 5 M investigation, although you might ot get a definite root cause. Also was the expected value low? have you ever calculated you uncertainties of measurement? Once every thing on your side is OK, only then could you place the cause onto transportation and storage.
Best
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I have been using a nonfat dry milk solution (100 g/L) for Salmonella pre-enrichment on samples of cocoa products. This solution is recommend by ISO 6887-4, instead of Buffered Peptone Water, since cocoa has antimicrobial compounds, and milk casein can avoid this activity. The ISO standard recommends, but does not explain the preparation instructions:
- The sterilization procedure is the main issue because the 10% skim milk solution always caramelizes when trying to sterilizate it on autoclave (already tried: 121°C for 5 min; 115°C for 10 min; 110°C for 15 min). Considering that I only have this equipment for sterilization, how can I avoid the caramelization? Does the caramelization affects Salmonella growth??).
Notes:
- Also tried a sterilization cycle of 20 min at 106°C. These were the only conditions that do not caramelized the solution.
- I don't have 0.22 µm filters.
- I have tried many diferent autoclavation cycles based on this question: https://www.researchgate.net/post/How-can-I-sterilize-skim-milk-and-avoid-caramelization
- A 1% (w/v) Brilliant Green solution was prepared. Is it safe to aplly on the milk solution without inhibiting Salmonella growth? The reason that I have not been using Brilliant Green is because our cocoa samples don't usually have high bacterial counts (100-1000 x 10³ CFU/g).
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I want to do a fermentation test for my yeast. I want to know if i can do it using YPD broth supplemented with phenol red as pH indicator. If can, how much phenol red would it needed, and how to formulate the broth as a whole. It would be very helpful if you attach some literature. Thankyou.
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I want to do a fermentation test for my yeast to know if they can ferment glucose or not. After some study i found that phenol red broth might be the media for it. But the example that using that broth is commonly for bacteria. So i want to know whether it can be used for yeast and how to formulate one. It would be very helpful if you give the literature for the formula. Thankyou
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Dear
The composition of Phenol Red Carbohydrate Broth has been introduced in the following link:
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Dear All,
I have problems with spoilage caused most likely by lactic acid bacteria in vegan sliced sausage. The product was stored at ~7°C in vacuum packaging and after three weeks it got yellow spots. Due to literature research I am pretty sure that it is Leuconostoc gelidum that causes these yellow spots.
I also had problems some months ago with slime after some weeks of storage and I think this was also caused by lactic acid bacteria. The problem in this case (pilot plant) is the recontamination of the product by the slicing process which is done manually.
Do you have any suggestion, which preservative agent works best against lactic acid bacteria or Leuconostoc gelidum in particular?
thanks,
Wolfgang
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.... of most bacteria, including food pathogens, spoilage bacteria, and the lactic acid bacteria used in vegetable fermentations, are readily destroyed by heating to 160°F (71°C), especially when the pH is low. Acid and low pH are also toxic to most bacteria. https://www.ars.usda.gov/ARSUserFiles/60701000/FoodSafetyPublications/p328.pdf
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I'll be conducting my thesis in Japan soon and I want to know what is the best method to personally bring viable microorganisms (specifically Lactobacillus spp.) in-flight.
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I recommend
Girish Korekar
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best wishes
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Please let me know about how to analyse pollen in honey in a simple and specified manner
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This method is recommended by the International Commission for Bee Botany:
Ten grams of honey is dissolved in 20 ml of warm water (40 C).
The solution is centrifuged for 10 min at 2500 r/min, the supernatant solution is decanted, and the sediments are collected into a conical tube and treated with an acetolysis mixture (acetic anhydride : conc. sulphuric acid = 9:1 V/V) for approximately 30 min at room temperature.
After treatment with the acetolysis mixture, the sediments are rinsed with distilled water, centrifuge for 5 min at 2500 r/min, and preserve for study.
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I am doing my master's degree on food microbiology. I am trying to isolate Listeria bacteriophages from cattle feces and waste water. Even though I am successful at isolation step, i can not move forward. I am applying double plaque assay. I see clear zones on the agar. I pick a plaque and suspend it in 100 µL PBS (phosphate buffered saline) in order to make dilutions. I prepare dilutions up to 10-6 again by using PBS. However, i don't get any results. No clear zones appear after I apply double plaque assay with the dilutions. In short, I lose my bacteriophages. How can I overcome this problem ? Could you please help me ?
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Milk-loving people, let’s discuss this video! I'm for sustainable agriculture and I agree that Remilk is revolutionary but there were points in this video that got me thinking:
1. “Milk is not healthy” is a broad presumption. Sure, there have been researches that were for and against consuming milk. But I consider milk as a healthy food since it contains proper amounts of dietary fats, proteins, vitamins, and minerals needed by the body. It is a reason why dietary guidelines (such as issued by the United States Department of Agriculture) recommends consuming three daily servings of low-fat/non-fat milk, yogurt, or cheese.
2. Alright, milk may be bad for consumers who can’t tolerate lactose. But how about in fermented milk products? During fermentation, microorganisms utilize lactose and produce lactic acid. I can think a lot about how lactic acid production is important in fermented milk products.
3. Milk has cholesterol but a cup of whole milk only contains 0.01% of cholesterol. How much more in low-fat or non-fat milk? Also, milk consumption increases HDL (high-density lipoproteins) cholesterol which transports excess cholesterol from the bloodstream to the liver for bile production. Bile serves as an emulsifier in the digestion of dietary lipids.
4. Indeed, milk is predominantly comprised of saturated fats. However, these saturated fats can be converted to unsaturated fats by microorganisms (e.g. lactic acid bacteria) during fermentation.
5. I can agree that milk is not entirely sustainable in the sense that the dairy industry greatly contributes to greenhouse gas (GHG) emissions compared to other agricultural practices. But we can’t ignore that there has been a significant reduction in GHG emissions throughout the years primarily by changes in breeding, nutrition, and management practices.
6. I honestly don’t know what to feel about animal abuse in the dairy industry. Does continually breeding dairy animals and leaving them in a lifelong cycle of reproduction and lactation might be considered animal abuse? (In my mind, it's a sad yes.)
7. Let’s say that the microbes have the same machinery as the cow’s mammary epithelial cells in producing milk, is it certain that they will have the same physicochemical composition, property, and functionality?
8. What are the external nutrient sources of the microbes? Is it the same nutrients found in the cow’s blood?
9. It is contradicting that they want to produce milk from microbes with the same chemical composition as cow’s milk but with no lactose?
This video discussed valid points that can be considered problems in the dairy industry. As long as this microbially-produced milk does not sacrifice the wonders of milk; Remilk, why not?
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I agree with you why not.
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Hi
Recently I'm working on food microbiology. I need pdf copies of AOAC 2017.09 and AOAC 2017.10 methods for rapid identification of bacteria in feed/food samples by Bruker MBT.
Thanks.
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Does the winemaking industry currently use enzymes derived from genetically modified organisms?
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The progress of science in the field of oenological yeasts led to the use of GMOs in the field of viticulture being considered by the IOV (International Organization of Vine and Wine) in 2015. This revision was framed within the International Agreement of the Cartagena Protocol on Biodiversity Security. In this Agreement, three branches were defined where recombinant DNA technology could be applied:
1. Plants
2. Yeast
3. Obtaining enzymes from genetically modified organisms It is worth mentioning that in 2003, both Canada and the United States of America accepted the use of these microorganisms, qualified them within the GRAS (Generally Recognized as Safe) category and today they can be acquired commercially.
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It is requested to please suggest that i have a standard method that gives answer in MPN/g and the requirement is that the result of Food microbiology must be reported in CFU/g. Kindly mention any personal work or research.
thankyou
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@Dear Prof. Sami,
There is one correction* in the sense that I had posted my response earlier but not on this thread. But I distinctly remember a similar question came up for discussion on RG platform some time back.
Regards,
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I am conducting a meta-analysis and most of my studies report values for bacterial analysis in CFU. However, I have one study which reports its microbial values in MPN. What should I do?
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The simple answer is that they are equivalent- one MPN is equal to one CFU. Both units measure the estimated number of bacteria in a water sample. Both are recognized by a variety of scientific and regulatory bodies worldwide including the US Environmental Protection Agency (EPA) and the International Standardization Organization (ISO). The difference is in how the measurement is obtained. The use of either MPN or CFU is based on the method used for the detection of bacteria and both are valid measurements for bacteria limits.
For CFUs, bacteria grow on a solid medium, like agar.  Afterward, colonies of bacteria are counted.  For an MPN measurement, samples grown in a liquid medium, like multiple tube fermentation and Colilert.  Positive wells/tubes are then counted and an MPN conversion table is used to generate a numeric result.  
In short, laboratories and agencies worldwide use both MPN and CFU interchangeably. 
Both measurements are well-established means to estimate the number of bacteria in a sample, and both carry a 95% confidence interval.  
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I have GCMS results for kimchi at different days of fermentation and for raw materials used to prepare it (part of the data in the image attached). I would like to group the compounds based on their origin (plant, bacteria, mixed/reaction product). I would be very grateful for any help!
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Also, you can compare the performance of each biochemical compound related to any factor analyzed by DCA or NMDS using the mentioned software in comparison with that of outcome from control samples (plant cultured alone without bacteria).
Best,
Saeed
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What do you recommend cheaper culture media instead of MRS media for Lactobacillus bacteria ssp. plantarum?
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MRS medium is rich in minerals and growth factors and hence is used for such fastidious lactobacilli.However, it could be replaced successfuly by a media based on whey enriched with minerals in many studies,
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I'm doing a study by using honey as my main treatment substance. The problem with honey is, honey collected from different sources have different physicochemical characteristic and its ingredient is also different. Does each honey sources need to undergo separate toxicity test? Human have consume honey for thousand of years and we can relatively say it is safe especially after rigorous standard food post-harvesting processes. 
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I obtained useful information from your reply on this RG question,
Regards for all
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Hi. I am a TA for a food microbiology lab and am in the process of updating our lab manual for Spring 2021. The majority of students in the course are a microbiology/biology program; however, several are animal/food science majors (my background). The prerequisite for the course is a general microbiology lab. Effective education is very important to me, so I'd love to hear suggestions on cool lab experiments or techniques that you think would be important for students to know. An example of something I'd be looking for comes from a Twitter post I saw this weekend - the researcher engineered 10 various chromoprotein sequences into E. coli. They then combined the strains into one culture and had students streak them onto plates to see how good their isolation techniques were.
We do everything from aseptic technique and dilutions to specific labs on food pathogens like Salmonella and C. perfringens.
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Tumour micro environment demonstrates immunosuppressive status due to various soluble factors such as IL-10, TGF-β, vascular endothelial growth factor (VEGF) , prostaglandin E2 ( PGE2), HMGB1, indoleamine-2,3-dioxygenase (IDO), as well as soluble forms of phosphatidylserine, Fas receptors, and MHC class I-related chain.
Prevailing inflammatory status will facilitate the abundance of 'inflammophilic' periodonto pathogens in OSCC tumour micro environment. P. gingivalis and F. nucleatum are classical examples as such.
P. gingivalis
  1. Several virulence factors are involved in the direct activation of inflammation and cell proliferation mediated by P. gingivalis. Among them, nucleoside diphosphate kinase NDK), FimA, and the LPS of P. gingivalis participate in the first stages of carcinogenesis.
  2. While gingipains and GroEL are associated with later stages.
  3. NDK inhibits proapoptotic mechanisms in oral epithelial cells by inhibiting the ATP/P2X7 , suppression of proapoptotic BCL-2-associated death promoter and activate antiapoptotic pathways (such as the PI3K/Akt, JAK/STAT, and MAPK pathways),
  4. These anti -apoptic pathways facilitate the 3rd phase - escape of 'immuno editing' by increased expression of STAT-3 or anti-apoptotic molecule Bcl2.
  5. FimA attenuates the host p53-mediated tumor suppression and cell cycle progression.
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Something besides the boar spermatozoan test? Thank you!
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by PCR
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Specifically for Rapid EC, Rapid Salmonella, Columbia blood agar, MYP, TSA, and XLD. Can it still grow? If so, what color and zone of inhibition?
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Ok, let me try...
On Columbia blood agar (with defibrinated blood incorporated after sterilization of the base medium) Listeria monocytogenes will grow and will give also a clear β-haemolysis reaction.
On TSA growth of the bacterium is obvious, though not so abundant (i.e. small colourless colonies and slow growth on the agar plate). For this to occur, 0.6% yeast extract should be added, thus making TSAYE, which corresponds to the preffered general purpose medium for L. monocytogenes. In general, yeast extract seems to be an important ingredient in the media used for Lm, since its use is suggested also by ISO 11290 in blood agar.
On XLD Lm will not grow, I can tell you that. I came up with that mistake once...
For the other culture media you mention, I can't tell.
Regards!
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Can anyone help me to get this article.
Rose Bengal chloramphenicol (RBC) agar. International Journal of Food Microbiology; 1987; 5(3): 261-262
Available online 5 November 2002.
Thanks
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Dear Dr Manjur,
Your requests are already granted by the researchers above. We shall discuss and see more easy alternative ways.
Best regards.
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Dear researchers,
I am doing some experiments on poultry samples. I found difficulties to prepare my samples for artificial contamination in the lab. My purpose is to completely decontaminate the samples to avoid any synergies with the strains that I will be using meanwhile keeping the meat in the fresh state (no thermal treatment).
Do you have any publications or protocols that may help me with that?
Thank you.
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Thank you Antonio for your suggestion.
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Hi everyone, I need to storage Clostridium botulinum strains, and I would like to know if the better option for this is to use Tarozzi media, supplemented with starch. Do you have alternative culture media?
Thanks in advance
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following
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In the microwaves that are widely used in homes and restaurants:
Are the bacteria destroyed by the direct effect of these microwaves and bacterial cell damage or is that due to the heat generation?
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Heat is generated by moving the water molecules in the microwave. The water in the cell is likewise expressed. Since the water inside the bacterial cell will be heated, the bacteria will die with the effect of this heat.
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I am working on natural antimicrobial  food additives, and I want to examine the ability of chitosan as an antimicrobial agent
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Dear Taghreed Hafez,
You may be able to produce water soluble chitosan by yourself!
Vahid
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.
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Based on the OIE-Listed Crustacean diseases 2017 report
Only two bacterial diseases
1. Necrotizing Hepatopancreatitis (NHP) caused by NHP bacterium (NHPB)
2. ACUTE HEPATOPANCREATIC NECROSIS DISEASE (AHPND) caused by Vibrio parahaemolyticus
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Hi Martin;
Nice to connect each other. I'm glad that you are doing awesome jobs in food microbiology. If you can came to Chicago (October 1-4) at 18th Food Summit conference (http://food.global-summit.com/america/) for your speech, I will be very happy to see you. Byong (byong.lee@mail.mcgill.ca)
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I wish you good presentation
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I want to produce Food grade Starter Powder from L Plantarum culture. So I have to separate microbial cells.
Must be low cost; Without centrifugal process; For mass volume (not industrial scale but for about 3 L)
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The traditional way would be centrifugation. Other methods would be for filter membranes but would require specific equipment. Sedimentation does not always occur, it depends on the strain. Evaporation and drying may be an option but temperature control is required.
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I want to isolate Salmonella from meat, which enrichment media could be used selenite or tetrathionate broth?
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The recovery of salmonellae from egg products was studied, by use of three different enrichment procedures: (i) selenite broth, (ii) selenite broth containing 10% sterile feces, and (iii) the lactose pre-enrichment procedure. Brilliant Green Agar was used throughout as the recovery medium. Although the lactose pre-enrichment methodology promoted Salmonella recovery from samples containing small numbers of dormant organisms, the efficiency of this enrichment method is adversely affected by unfavorable coliform-Salmonella ratios. Under such conditions, early subculture of lactose broth into selenite broth is indicated. Selenite broth containing 10% sterile feces was more efficient than the lactose pre-enrichment methodology in promoting the growth of “dormant” salmonellae. Albumen adversely affected recovery of salmonellae from selenite broth, whereas whole egg and egg yolk enhanced Salmonella recovery from this medium. The selenite-feces medium presents a solution to the major problems encountered in the detection of salmonellae in egg products and offers an approach to a single medium in which food-borne salmonellae will manifest themselves with a minimum of laboratory manipulation.
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I would like to harvest Photobacterium and Morganella via centrifuge. Which rpm and time is better to avoid damage cells?
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Hi:
In order to pellet cells, people usually use around 5000 g (centrifugal acceleration 5000 times the gravity on earth) for 10 minutes.
Regards
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Thanks Dr Malcolm John Reeves for your answer. I will try to determine which species of mycoderma it is.
-----updates-----
Thank you for your answer, Dr Paulo Cameira dos Santos. I had not paid much attention to the fermentation volume yet, and only thought that if the final inoculation density was fixed, the dominant microorganism would have been starter culture, regardless of the volume. Further, if possible, I will investigate the volume's effect on the contamination of a MLF.
Thank you for your time and sharing again!
-----updates-----
Thank you for your time, Paulo Cameira dos Santos, Sunita Singh and Bachtarzi Nadia. There were some supplemented information for this question.
What was the volume of the experiment, and the aproximate size of the container of the wine?
The volume of model wine was 100 mL, and there was no CO2 replenished on the headspace of the PET bottle. The film emerged after 3~4 days of innoculated malolactic fermentation.
Did you observed the film by the optical microscope? It was cocci or bacillus?
I had observed the film via a optical microscope (second picture through 1000x oil lens). The size of observed microorganism was much better than bacteria. The shape was close to cocci.
-----updates-----
The film was gram stained, and it looked different from bacteria. A smell of ester mixed with vinegar was detected when I opened the cap. What it was? Will that be a kind of yeast? Thank you!
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there must be mixed culture microbes . isolate and allow for some time succession may take place for you to know if its fungi or bacteria or algae or possibly protein micelles
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preservation of meat from germs
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Please have a look at these PDF attachments.
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Someone has information on fermentation with abnormal development of volatile acids in the rehydration of stockfish?
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Nice
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I will inoculate the P.Phosphoreum to fish. I could not decide on the stock culture media and method for determination. Can anyone help me please?
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by LAMP vageli.
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I'm looking for a procedure that is easy to observe the germination and establishment of the germ tubes of mold spores. If anyone has any info, please inform me.
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Thank you for your help. This article really helped me.
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For next semester (Semptember 2017) I'm looking for a master student who would like to study on seafood processing and seafood quality and/or meat processing and meat quality (chemical, sensorial and microbiological quality). In addition, our faculty give schoolarship for all students. If there is someone who is interested in this, please contact with me.
Bests,
ilknur
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yes on two conditions that i will be allowed to start PhD in the same field at same place. find attached my cv
 Regards
ogori A.F
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Hello Everyone, during the completion of the research about edible coated strawberry.I should check microbial plate count using PDA and PCA. However the result of CFU for both coated and uncoated strawberry showed that PDA had higher CFU compare to PCA. Can anyone give the possible explanation for my results?
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Dear Meilina,
PCA and PDA are used to make two different counts. You use PDA to detect yeast and mould and you use PCA to detect bacteria in general. As pH of both medium are different they tend to show different counts even if they come from the same sample.
One possible explanation is that all yeasts that could not grow at the "high" pH (around 7) of PCA are able to grow only on PDA (pH 3.5). Which would be very likely as fresh fruit tend to have a high count of yeasts and strawberries have a low pH.
It should be easy to verify this just by taking a look of at the microscope of some of your colonies just to make sure you have two different populations on each medium.
Good luck! 
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To increase the sensitivity for PCR methods of detection of microbial foodborne pathogens, the bacterial numbers are normally enriched from 5 hours to overnight. Is it possible to reduce this enrichment time by concentrating the cells in a sample using latex beads? I understand there is a method using antibodies bound to the beads but I would like to avoid this if possible. If anyone has any references or experience with this can they help ?
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Hi Karen:
That is a big issue. I think that the beads are not universal for all microbial cells and would only work specifically for some targets such as Salmonella,etc. I am afraid that you would have to consider classical methods such as filtration and centrifugation. I am enclosing a couple of references as starting point.
Best regards
Jorge
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While extracting protease from the B. subtilis containing media, what is the best way to remove protease for Food applications? While adding ammonium sulphate precipitation, the result will be suitable for applications  in food or not? Any methods to carry our protease assay?
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you can used preciptation with amonium sulphate or with aceton and centrifuge then check assay of enzyme after dialysis (just when used NH4SO4)
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for fermentation of yogurt culture  inside an incubator it needs constant temperature condition for some period of time eg 37 degrees for 4 hours without changing.Hence how can i maintain constant temperature for a period of time inside the incubator ?
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I think you mean uniform temperature inside an incubator. Well, we all know that air is a bad conductor of heat and therefore, to get even distribution of heating or cooling in any closed chamber, you must have a blower (may be for an incubator it may be a gentle blower type as compared to an oven). To keep the temperature constant your thermostat should be of a good quality.
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Mostly the incubation time of bacteria is 48 hours. But, if i want to know the dry mass of the bacteria. So, how long i should incubated it? is it 24 hours, 48 hours, or in the mid log phase? because i use minimal medium for my bacteria.
Thankyou
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You most welcome
Houda
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Hello! I am working on a rapid method of rough estimation of bacteria in milk, like an ATP test. Can someone suggest some other methods besides ATP test?
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Thank you! But if I want rough estimation of bacteria, ATP test is suitable?
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I am working on cold active lipases and having trouble in purifying the enzyme due to very high degree of aggregation. I have tried breaking the aggregates using several detergents such as CHAPS, Tweens, Triton X100, NP40, Brij-35, SDS, etc but no success till now. The high molecular weight aggregates are not able to move in to PAGE and remain stuck at the interface of stacking and resolving gel. Find the attached images of SDS and native PAGE showing protein bands at the top of gel. Any suggestions please..
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What, precisely, is your aim? Do you just want to see the protein in the gel (e.g., for quantification), or do you want to purify the active enzyme (e.g., for kinetic measurements or industrial use)?
In the former case, I'd start with 7 M urea, 2 M thiourea, 10 mM DTT and 1%SDS. 
In the latter case detergents with fat-like structure (lyso-lipids, fatty acids, FOS-choline, LysoFos, neopentenyl glycols) may be able to to solubilise functional protein. In any case, I'd start with a careful literature search. A day in the library can save you months in the lab!
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I'm going to transform Salmonella with linear DNA for lambda-red recombination. I've been doing chemical transformation by heat shock at 42C with plasmids, which has been successful. However, I haven't tried this method for linear DNA yet. Has anyone tried this before? How about the transformation efficiency?
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If you are trying to knock-out bacterial genes using lambda-red system, I suggest you use electroporation rather than heat shock for linear DNA. Because electroporation gives higher transformation efficiency and you need a lot of linear DNA going into bacteria to have a chance for DNA recombination! 
I could suggest you have a look on this paper for detail
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I am conducting a viability assay and have had some trouble deciphering what strain is the standard to test against. From what I can tell people uses so many different strains. I am testing Listeria, Salmonella, and Staph.
I have the Listeria ATCC number from a colleague at my university. Any help?
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When it comes to viability studies, it is common to use a cocktail of different strains, so that the study is more robust. Ideally, you could select strains that are usually found in the food you are testing (preferably those which are more difficult to kill) or even strains involved in previous food poisoning outbreaks. But if you're dealing with a project in its early stage, you can also use an ATCC strain, just to conduct the preliminary tests. Good luck!!
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What is the appropriate concentration of Gum Arabic to be inoculated in to yogurt
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Dear sir
The Arabic gum will affect on the physicochemical, sensory and flow behavior characteristics of yoghurt and the recommended rat of addition from 0.2 and not more that 0.5% according to the total solid contents of yoghurt milk
shenana
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I want to study antimicrobial properties of nano emulsion prepared from a cationic emulsifier other than Lauric arginate (LAE) ,Does anyone have any suggestions?
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Thanks so much.
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There are two origins of phytase : microbial phytase EC 3.1.3.8 and plant phytase EC 3.1.3.26. I want to know if the microbial phytase from Aspergillus niger is GRAS ( Generally Recommended As Safe) or not. Thanks
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phytase It is an enzyme and passes several steps of purification ..Definitely  Aspergillus niger is GRAS 
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I've found it when evaluating the efficiency of cabbage disinfection.
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Hello dear Claudia Gentil!
Most probably it is a Helminth eggs.
Please try to write the name of this worm and you will find a lot of info in the internet.
I also have attached a document related with the microbial risks associated with cabbage.
Hope that this info will be helpful.
Have a nice day and successful research.
Sincerely,
Vitalijs
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in my recent work I need to sterilize a chicken drumsticks samples to inoculate them later with specific E coli strain then treat them with chemicals and recover them after treatment, and the later step I will study the effect of my treatments to the strain I used. the tricky part is how can I be sure that I'm recovering the same isolate if the samples were not sterile 100% ?.
In fact I already tested some methods for sterilization I used dipping in alcohol up to 3 minutes and still have some E Coli appear in the plates, then I sent some chicken drumsticks for Gamma radiation. the issue with the radiation is I still have a high microorganisms populations around log 5-6 growing in TSA media at 30 C for 72 hours. but in the other hand there is no E coli can be detected in VRBA-MUG media at 37 C for 24 hours.
the question is should I be satisfied with the fact that Radiation possibly eliminate all the E coli background in the samples ? or the presence of other microorganisms which they can be mold yeast and other Enterobacteriaceae in TSA is problematic ?. people here think this load will affect the attachment of the E coli strain I want to use.
is radiation suppose to eradicate all microorganisms because in my reading I find it doesn't in fact it eliminate bacteria while spore forming and mold reduced only and there is temperature , time and dose factors can interfere with the results. also the radiation dose I used was 10 kGy for 17 hours which is higher than what really recommended and found in references.
Finally , is it really possible to sterilize chicken samples for experimental purpose? and if it is possible is there any better method rather that radiation?
Thanks in advance 
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You can cook the meat so that all the bacteria are dead and ensure its sterile. Then go for doping with your Ecoli and use chemicals as you suggest as preservative.
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i use low molecular weight to check antifungal activity 
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Dear Maliha,
Low molecular weight chitosan is very potent anti-fungal substance. The following references will help you to know the details:
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I would like to find studies of the possibility of growth and reproduction in low pH conditions of some Сlostridia and Bacillus strains, capable of causing disease, food poisoning or allergies. Thanks in advance for any information!
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Hi Hoshi, thank you! The second article is close to what I'm looking for
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I would like to analyze a fermented food product (microbiological and physicochemical analysis), I wonder how I will transport it, at room temperature or in a cooler?
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Yes..you will need to sample aseptically (in sterile containers) and transport your samples in an iced cooler box and analyze within at least 24 hours. the faster you do the analysis the better the results and the more they will be truly representative of the original sample.
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Hello everyone
I am looking for a factor that could efficiently kill V. parahaemolyticus without completely dissolving the cell membrane. The ideal treatment should kill Vibrio by making large holes in the cell membrane, without dissolving it. Does anyone have any idea?  
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Electroporation
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When I detect spores, are there any specific tests? Will the presence of spores in a food product show colonies in TPC? If yes how to differentiate the two
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When you perform the total plate count you will be able to observe the growth of fungus as well as bacteria.
Once there is growth on the plate you can perform different staining techniques and after microscopic examination you can perform confirmatory spore staining 
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I was growing Lactobacillus spp. from different yogurts using MRS agar to determine cfu/mL in different products. I also did Gram-staining and catalase test to confirm microorganisms grown are most likely Lactobacillus spp. Most of them looked like typical Lactobacillus but from one yogurt I managed to isolate some weird looking Gram+ organism. What can it be? Pictures are attached to this question.
According to manufacturer (written on the packaging), this yogurt contains: Lactobacillus acidophilus LA-5, Bifidobacterium BB-12.
Thank you in advance
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You can go for 16s RNA gene sequencing or perform API test to determine the species of bacteria based on the biochemical reactions.
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For enrichment of Campylobacter i need Lysed horse blood, anyone know from where I can order horse blood, oxoid and other foreign companies take 4 weeks, I need it urgently.
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Go to a local veterinarian or vet school and ask for a sample.  Most are happy to collaborate.  You may need an IACUC protocol though.
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Dear collegues, how can I estimates copy number variation across different S. cerevisiae strain geneome sequences with "in silico" approach?
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One of the easiest approach is Ginkgo (http://qb.cshl.edu/ginkgo) . It was published for low coverage / single cell data. Check it out if you like.
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Hurdles in food microbiology
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Excellent answers all round. And in addition, we may consider hurdles those forms of Unit Operations with a focus on preservation, i.e. shelf-life and food safety promotion. From food technology, we see the order of unit operations adopted for any food production processes, depends on a range of factors - but mainly the type of product desired. So, I agree with Jagan above, the combination of hurdles adopted will depend on the food product. Another interesting concept is to consider parallel versus sequential/ consecutive hurdles. Examples of parallel hurdles? Storing acidified food @ low temperature produces parallel hurdles of low pH and low temperature. Products with modified atmosphere packaging are frequently stored at low temperature.
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 I use MPN method for enumeration of E.coli in food contact surfaces and now I want to convert MPN to cfu.
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The MPN values you found you just multiply by are you collect material
If the area is 2 cm2, You just multiply by 2
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Can the microbial quality of spices affect the rate, quantity, quality and the antimicrobial property of the essential oils extracted?
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chances are based on what microbe it is and how its pathogenesis takes place with respect to the host. most microbes do hold a symbiotic relationship with its host plant.
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I would like to measure the particle size of pea globulins in a Malvern Mastersizer and the refractive index is requiered.
Thank you!
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You won't get such direct reports. You must first do the basic characterisations like MW etcAnd then from any data bases for proteins you may get some data.
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I have taken 10 g of sample + 90 ml of sterile saline water and then it is serially diluted to 10-4. From that, 0.1 ml sample is taken in agar plate following spread plate technique and it is incubated at 37 °C for 48 hr. I have counted the number of colonies and found around 50(say). The formula is calculated as log (cfu/g) :
     Number of colony/dilution × volume of sample taken × 1/weight of sample
Since 0.1 ml = 1/10ml
  Number of colony/10-4 × 1/10 × 1/weight of sample
Since 10-4 = 1/104
 = 50 × 104 × 10/10 = 50 × 10= log 5 × 105 = 5.70
Or,      
Number of colony × 1/dilution × volume of sample taken 
Since 0.1 ml = 1/10 ml
Number of colony/10-4 × 1/10  
Since 10-4 = 1/104
 = 50 × 104 × 10 = 50 × 104 × 10 = log 5 × 106= 6.70
Which one I have to follow?
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Hi Jag pal,
You have taken 100 ul (0.1ml) sample from your stock which you prepared by suspending 10g in 90 ml water. You have got 50 CFU/100ul  which is equivalent to 500CFU/ml. I am not using any dilution factor here as you have not diluted your sample. Now you can convert your 500 CFU/ml to grams :
As you know your 90 ml water is in 10 grams
hence 1ml will be in 10/90 = 0.111g
hence your
500CFU/ml = 500 CFU/0.111g  = 4545.45 CFUs/g
Hope it helps
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What is the stability of Moxalactam sodium salt in PBS and water at 4, 8 and -20 °C. Can anyone help please?
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Thank you Rafik Karaman. 
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Hi,
I'm highly interested in data on S. epidermidis cell number in ready to eat meat products. Can anybody provide me with that information?
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Hi 
Please can look in attach file 
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Food samples are preserved for microbiological analysis by operators for public health to understand an outbreak. There should be a standard operating procedure around this process of collecting, preserving, and maintaining the library for public health inspection, audits for system verification, and finally removal in the event of an outbreak.
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You should look up standard analysis  documents/ standard such as British Pharmacopoeia    https://www.pharmacopoeia.com/  , some older version is downloadable  
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Toona sinensis has a strong odor, which is an important food quality. However, no related researches can be found to explain the nature of this odor. Sulfur compounds may be the most important chemicals which lead to the characteristic aroma. I want to know how to identify that compounds. Can you help me?
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I'm not sure what's your point. You may want to look into different flavour extraction methods. Doing the study of volatile aromatic compounds would be interesting in this case. You have to be very careful in selecting different extraction methods like SPME, Purge and Trap, SDE. It is always better to combine different extraction methods to find the best result. I would suggest you to use two dimentional GC, in coupling with TOF (GC × GC/TOF-MS). This is very sensitive and recently used technique. 
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i just know that Kefir grains are a combination of lactic acid bacteria and Several varieties of probiotic bacteria and yeasts in a matrix, so i wondered if i can create the kefir gains from milk or have them spontaneously in milk ?? if you have any information or propotiosion !!
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 Kefir grain contains mixture of different LAB and yeast species. It is not impossible bu so difficult. I agre with Prof.Dr. Bozanic. You can create kefir culture.
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Cordyceps Militaris was inoculated on the rice liquid culture medium. The pH value of liquid medium first increased and then decreased. I want to know the reason for the change of pH value. Why the pH change? Waiting for your answer. Thanks!
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The decrease in pH may be due to production of organic acids. I just think the increase in pH observed after the decrease may be due to some of these acids (eg lactic acid) are metabolized (act as substrate) to support microbial growth. Because this reduces the concentration of the acid hence an increase in pH. To  ascertain this you need to measure titratable acidity (TA) too and see how that changes along the course of microbial growth.
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For my research work I need two types of Lactobacillus along with the normal one. 
Type one - Lactobacillus sp that grows at pH 6-7, But do not grow at pH 3-4. 
Type two- Lactobacillus sp that grows at higher temperature (60 oC) but growth rate is very slow at 37 oC.
Can anyone please suggest me any source for this
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Dear Diptiman Choudhury basend on my knowledge about gut colonization by Lactobacillus I think that the result of your research could be reached:
1 - using (or isolating) a Lactobacillus strain endowed with high adhesion properties to human gut ;
2 - growing it under condition promoting adhesion
3 - carrying out in vitro experiment to verify if it can adhere after different killing treatment (please note that many molecules involved in adhesion are sensitive to physico-chemical treatments)
4 - verify in in vivo experiments (eg. mouse) the best result from step 3 so, in addition, to understand how long it can colonise (or persist in) the gut
The immunostimolation by dead lactobacillus cells should have been already published (sorry I do not remember the paper!) so you can take advantages from that results.
However, in order to reach you goal I have some problem to understand your previous questions.
Wishing you successfull experiments
Best regards
FBaruzzi
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After production of bacteria bacillus amyloliquefaciens i have found it to be more light and can easily be a run off and majority may go to a waste. I could like to know if their is a way i can formulate it and still maintain its viability and stability so as it can be a bit sticky or thicker to the areas of application. help please in its formulation.
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Dear Geoffrey Onserio Nyamagwa, First of all you have to optimize the growth of Bacillus amyloliquefaciens. For this you have to take Nutrient broth and from many literatures it is found that the pH is 7.0 and temp. is 30-40 degree celcius for Bacillus amyloliquefaciens. What ever it may be strains varies therefore you have to optimize the growth by changing pH and temp. and use shaker incubator of above 150 rpm. Hope it will help You. All The Best.
-AKM
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I am working with probiotic bacteria and their application in foods. The topic of my research is the use of microencapsulation strategy for the improvement of probiotic viability. Now I am interested in investigating probiotic ability to survive in food in presence of additives (e.g. flavourings, sweeteners, aroma compounds and so on). Have you ever tested some additives?
Thank you.
Greetings, Annachiara
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Hello
You can add some additives  for food , It is prebiotis 
exp. 1-add Arabic gum in ice cream  is increase the probiotic bacteria and I now work on add Arabic gum in yogurt .
2-Fermented onion is increase the probiotic , onion is prebiotic  
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Samples are from a food manufacturing environment (sponge samples).
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vickie - e-mail me.. The question is how you know it's a false positive in the Bax; could be a false negative in the "standard method" too. 
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I am growing G. xylinum, in coconut water (4% sugar  and 0.1% protein ) in glass bottle, with lid 100ml. After 24h I observe some white deposit on the bottom of the bottle but the colour of the coconut water is transparent with no increase in opacity.
As I am not seeing Nata type consistency after 6 days. What is the best possible way to harvest deposits settling on the bottom (cellulose). I came across some papers suggesting washing with 2% NaOH while others washing with acetic acid and so on.
I thought I could receive some useful insights.
I would love to get some idea from people who have worked with glucose, fructose, lactose and sucrose. How does the addition effect production and does different carbon source alter the cellulose crystallinity.
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You need some more N source for good bacterial growth.  Peptone or yeast extract would be good or if you want to keep it defined, ammonium chloride or nitrate.  You do need to be sure there is enough oxygen for growth. 
Cellulose won't be affected by acid.  You can collect the pellet and wash with HCl.  if you want to wash with base you need to add sodium borohydride to protect the cellulose from the base.  Base will likely alter the crystalline structure.
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I tested viability of L. plaatarum NCIMB 8826 at simulated gastric fluids. My SGF was prepared by using 2 g NaCl, 3 g of Pepsin and 7 mL of conc, HCl. Distilled water was then added to get 1 L. After that pH was adjusted to 2 by 1 M NaOH. SGF was sterilized by a syringe filter (0.2 um). One mL of culture was added into SGF and incubate for 2 h.
After incubation, I did dilution in saline solutions and used pour plate method.
I and my labmate repeated in couple times. The cell counts were higher that 6 log CUF/mL. The results reported by other papers showed that the cells could not survive after 2 h at pH 2. 
Can anyone suggest what happen with my result or what I did wrong?   
Thank you in advance. 
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Please, make sure the inoculation size  of bacteria and isolation  source must be from  Human sources 
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.
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Yes the serotype of C. muytjensii strain 51329 is Cmuy O:2.  See
Jarvis, K.G., Yan, Q.Q., Grim, C.J., Power, K.A., Franco, A.A., Hu, L., Gopinath, G., Sathyamoorthy, V., Kotewicz, M.L., Kothary, M.H., Lee, C., Sadowski, J., Fanning,S., Tall, B.D., 2013. Identification and characterization of five new molecular serogroups of Cronobacter spp. Foodborne Path.Dis. 10, 343-352.
 
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i'll then have to carry out a controlled fermentation in the lab
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Dear Bridget,
This might help you a little.
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Hello, 
in my knowledge, filamentous fungi usually grow slower than yeast. Does anyone has the same opinion? Please include references.
Thank you
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Excellent Stephane, Thank you so much. you have answered my question perfectly. 
For your information, I am developing a specific method for marine yeast isolation that is why there are yeast and mold together.
The number of yeast cells and mold is not known to me but both in the seawater sample.
I used the YPD broth as enrich media as  explained before for 2 days then used the culture to inoculate a fresh media for 2 days then inoculate a fresh media for another 2 days 
but now I am writing a research article with full details on the isolation method, characterization  and identification of marine yeast. 
so many thinks a gain and if you have supporting reference for what you explained will be very much appreciated 
Abdelrahman
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Summary
Tofu industry in Indonesia which has been dominated by local’s small entrepreneur, and very identical with the use of formalin (formaldehyde), a dangerous substance for food additive. Since 1940s, the dependency is severe due to the drastic gap of productivity between the usage and no usage of formalin, since there has been no food additive alternative for the case of increasing the yield and shelf life of tofu.
Tofu producers are now enjoying a new hope from the emergence of newly develop natural preservative: a lactic acid bacteria culture that is able to give the equal yield and shelf life compared to formalin. However, there has been no regulation for such product in Indonesia, thus the application of the product will bring numerous problems to the producers because the “formalin mafia”s are around and will likely use the regulation gap to dispute and extort the producers.
A team of food scientists (including my self and Prof. Winarno) and an elder from a tofu producer community himself have been striving to register the new preservative to the appropriate regulation, whether it is already exist or needs to be made as new. The team itself has no interest regarding the product, but only in the purpose of putting an end to the use of formalin in Indonesia. Several laboratory tests have been conducted with the following results:
1. Contains active Lactobacillus spp cultures
2. Inhibits the growth of tofu-deteriorating/rotting microbes (directly retrieved from the tofu)
3. Has the pH of 4
4. Contains only 0.39% of lactic acid
thus brings assumptions of bacteriocin and organic acid (gives low pH) as the cause of its preservative activity.
Bottomline
Regardless the confidentiality and research limitations, We wonder anyone has any reference(s) for regulation, analysis methods, or anything that might be useful to the issue.
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