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.
Questions related to Food Microbiology
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!
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?
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??).
- 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).
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.
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
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?
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.
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 ?
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?
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.
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?
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!
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.
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.
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?
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.
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?
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
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?
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)
Thanks Dr Malcolm John Reeves for your answer. I will try to determine which species of mycoderma it is.
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!
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.
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!
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?
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.
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.
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?
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 ?
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?
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 ?
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.
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..
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?
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?
I want to study antimicrobial properties of nano emulsion prepared from a cationic emulsifier other than Lauric arginate (LAE) ,Does anyone have any suggestions?
There are two origins of phytase : microbial phytase EC 220.127.116.11 and plant phytase EC 18.104.22.168. I want to know if the microbial phytase from Aspergillus niger is GRAS ( Generally Recommended As Safe) or not. Thanks
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
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!
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?
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?
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
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
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.
Can the microbial quality of spices affect the rate, quantity, quality and the antimicrobial property of the essential oils extracted?
I would like to measure the particle size of pea globulins in a Malvern Mastersizer and the refractive index is requiered.
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 × 104 = log 5 × 105 = 5.70
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?
I'm highly interested in data on S. epidermidis cell number in ready to eat meat products. Can anybody provide me with that information?
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.
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?
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 !!
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
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.
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?
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.
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.
in my knowledge, filamentous fungi usually grow slower than yeast. Does anyone has the same opinion? Please include references.
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.
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.