Knowledge - Inside Search - Google

Introducing the Knowledge Graph

http://www.google.com/insidesearch/features/search/knowledge.html

Food Safety Project, Iowa State University Extension

http://www.extension.iastate.edu/foodsafety/Lesson/contact.html

: : 美國肉類出口協會 : : 美國牛肉熟成之介紹

http://www.usmef.org.tw/trade/sell_data/s_product08.asp


Sent from my iPad

More questions

1. Are Acetobacter species & Saccharomyces cerevisiae salt-tolrant and can grow

on food at 7% salt w/v??

Both of these two are not known to be salt-tolerant.

2. Are both Acetobacter species & Saccharomyces cerevisiae mesophiles so they

cannot grow in food at 15 or 5 degree Celcius??

Acetobacter usually cannot grow below 15C.

Saccharomyces cerevisiae may be able to grow below 15C but 5C would be too low for much growth.

-----Original Message-----
From: wwwwwwwwwwwwwwwwwwwwww
Sent: Tuesday, May 08, 2012 3:53 PM
To: Prof. HS Kwan (School of Life Sciences)
Subject: RE: Questions on FNSC4180 Food Microbiology

Dear Prof. Kwan,

Oh, I see. Then, I am sorry that I would like to ask more questions...

1. Are Acetobacter species & Saccharomyces cerevisiae salt-tolrant and can grow

on food at 7% salt w/v??

2. Are both Acetobacter species & Saccharomyces cerevisiae mesophiles so they

cannot grow in food at 15 or 5 degree Celcius??

Question on calculation of number of D values

You asked the wrong question: the target of your problem is not to calculate D-value but the number of D's necessary to reach the acceptable cell density.  So the initial cell density is important.

From 1000 units to 0.001 units requires 6D.

Best,

HS Kwan

From: jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj
Sent: Tuesday, May 08, 2012 1:13 PM
To: Prof. HS Kwan (School of Life Sciences)
Subject: Questions about final exam

Dear professor Kwan,

Good afternoon, today someone ask me how to calculate the D-value from the cell density, and I found that my friend's and my method is a little bit difference.

In determining D-value, if the initial cell density of that target microorganism (#) is 1000 unit, and the acceptable cell density of # is 0.001 unit, what should be the D-value calculated? 

My method is like that:D x log (1000/0.001) = 6D

My friend's method: D x log [1/(0.001)] = 3D

I found that the main problem is that do the initial cell density needed to be involved into the calculation ? 

--

More questions

You do not need a Google Blog account to read the blog. Answers to your questions:

1. Is Pseudomonas species salt-tolerant and can stand food w/ 7% salt w/v?

A:Many Pseudomonas spp are salt-tolrant and can grow on food at 7% salt w/v.

2. What is the pH range for Pseudomonas species to grow? Can it grow in food w/

pH 5.2?

A: Pseudomonas spp are highly diversified in many properties. They are not acid tolerant and likes to grow around neutral pH. They probably cannot grow in food at pH5.2.

3. As Listeria monocytogenes grows at pH>5.5,then it must be impossible to grow

in food w/ pH 4.8??

A: pH limits are influenced by many factors including the type of acids in the food. Where did you get the limit of pH>5.5? Your statement does not indicate that pH5.5 is the limit. Some reports showed that L.m. can grow at pH as low as 4.25.

4. Is Escherichia coli 0157 H7 salt-tolerant and can stand food w/ 7% salt w/v?

A: O157:H7 is not salt-tolerant. It would grow very poorly in food at 7% salt w/v. Some reports showed that it cannot grow at all at salt content above 8.4%.

5. What is the pH range for Saccharomyces cerevisiae to grow?

A: Saccharomyces cerevisiaw grows around neutral and slightly acidic pH. It is not usually characterized by their pH range. It is a fungus and can tolerate strong acids better than weak organic acids.

-----Original Message-----
From: wwwwwwwwwwwwwwwwwwww
Sent: Monday, May 07, 2012 12:27 AM
To: b097709@mailserv.cuhk.edu.hk
Subject: Questions on FNSC4180 Food Microbiology

Dear Prof. Kwan,

  I would like to ask you some questions on the course via e-mail as I don't

have a google blog account.Thank you very much!!!

1. Is Pseudomonas species salt-tolerant and can stand food w/ 7% salt w/v?

2. What is the pH range for Pseudomonas species to grow? Can it grow in food w/

pH 5.2?

3. As Listeria monocytogenes grows at pH>5.5,then it must be impossible to grow

in food w/ pH 4.8??

4. Is Escherichia coli 0157 H7 salt-tolerant and can stand food w/ 7% salt w/v?

5. What is the pH range for Saccharomyces cerevisiae to grow?

Question from students again

I do not have the time to go back to that question. Your answer appeared to be correct. When you can provide specific and precise results, give these results. That is, give the answer of 10^-9995/ml.

Best,

HS Kwan

-----Original Message-----
From:dddddddddddddddddddddddddddd
Sent: Sunday, May 06, 2012 11:59 PM
To: hoishankwan@cuhk.edu.hk
Subject: Questions regarding FNSC 4180 exam

Dear Professor Kwan,

I would like to clarify my understanding in D values.  From the pastpaper

2007-2008 question 6d, I got the following answers

New D value for each bacteria at 120C

Spoilage bac.: 0.0025min

Bacterial spores: 0.25min

Fungal spores: 0.05min

Therefore, the cell densities would be

Spoilage bac.: decrease from 10^5 to 10^-9995/ml

Bacterial spores: decrease from 10^4 to 10^-96/ml

Fungal spores: decrease from 10 to 10^-49/ml

Are my answers correct? From your blog, I do realize sterilization greater than

12D is possible.  However, when it comes to the cell density, eg 10^-9995/ml,

shall I write  10^-9995/ml or simply 0? 

Clean animals result in fewer E. coli

http://www.sciencedaily.com/releases/2012/05/120504110031.htm#.T6W0LH5IML0.gmail

Memorization question from student

You should at least know the values of the major groups, such as yeast, bacteria, etc.

Best,

HS Kwan

From: wwwwwwwwwwwwww
Sent: Saturday, May 05, 2012 5:15 PM
To: hoishankwan@cuhk.edu.hk
Subject: Question about exam

Dear Prof. Kwan, 

I would like to ask whether we need to memorize the water activity of specific microbe or food.