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Food Engineering/Manufacturing/Garlic in Salad Dressing- Shelf Stability

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QUESTION: Hi Peter,

I came across an answer you provided to a similar question that I have but would appreciate further information.  (http://en.allexperts.com/q/Food-Engineering-Manufacturing-2446/Caesar-Dressing.h)

I too would like to bottle my homemade Caesar Dressing which contains Oil/Vinegar/Fresh Garlic/anchovy paste/spices and would appreciate further clarification on how I can guarantee that my recipe will not cause botulism as I anticipate selling it retail.  

I visited the ONLY co-packer where I live and was not comfortable with his answer to my questions...he recommended adding xanthum gum without even checking my recipe and said it would be stable.  Needless to say he was on the news a few months later because he was shut down by the health dept.

I would like to bottle it myself at a commercial kitchen and just need to know if it is safe...how do I go about this?  I can't seem to find a straight answer.  Is the safety of the dressing based on ph levels?  Will the vinegar in the dressing prevent botulism?

Thank you in advance for your help.

- Dana

ANSWER: The safety of foods in general is dependent upon pH, among other factors. Clostridium botulinum does not produce toxin below pH 4.6 The garlic is high pH, but is usually a small component. As I said previously, it might be a good idea to blanch the garlic or to use dried garlic, but if the pH of the complete product is low enough, it will be safe. The suggestion to use xanthan gum was meant to help suspend particles, and because many commercial dressings have it. You may not need it, if you are willing to advise users to shake well. The anchovy paste probably is preserved by salt. Depending on your specific formula, FDA may consider your product to be an acidified food, whose preservation process must be filed with FDA by a recognized process authority. This only applies if you intend to sell in interstate commerce. Because oil is a low acid food, adding vinegar makes the mixture an acidified food, in the eyes of FDA.

---------- FOLLOW-UP ----------

QUESTION: Thank you so much for the answer.  My next step is to prepare a batch and test the pH myself before sending off for lab testing.  I just wanted to be sure I wasn't going to send something that would be rejected by the lab and that I'd have to pay for re-testing.  Are you able to recommend any specific lab for shelf-life testing/nutritional analysis?  

Also, what determines whether a dressing needs to be refrigerated at all times or if it can stay at room temperature?  I anticipate bottling myself initially and storing the finished product will be difficult if I need it to be refrigerated.

Thank you,

Dana

Answer
If a food has a pH above 4.6, water activity above 0.85, does not contain approved chemical preservatives, and has not been heated sufficiently to kill C. bot spores, then it must be refrigerated. Any of the opposite conditions makes a food shelf-stable. That is: pH below 4.6, water activity below 0.85, approved chemical preservatives, or sufficient heating. (C. bot spores are killed by heating for 2.54 minutes at 250 F.) Initially shelf-stable products are often stored refrigerated after opening because they become vulnerable to contamination in use.

There are many labs that can do shelf-life and nutritional testing. A good one is Silliker. My friend, Pam Coleman, is VP (email pam.coleman@silliker.com). A faulty product would not be rejected by a lab, but you would learn it was faulty and need to reformulate.  

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J. Peter Clark

Expertise

How various processed foods are made; ways to improve manufacturing; how to make a new food product.

Experience

Employment history: Research Engineer, U.S.Agricultural Research Service, Associate Professor Chemical Engineering, Virginia Tech, Director of Research, Continental Baking Company, President, Epstein Process Engineering, Inc., Vice Presdent Technology, Fluor Daniel, Inc., Consultant to the Process Industries

Organizations: American Institute of Chemical Engineers (Fellow) Institute of Food Technologists, American Association of Cereal Chemists, American Association of Candy Technologists, American Society of Agricultural Engineers,

Publications: Several Encyclopedias (Kirk and Othmer, Chemical Technology; Food Science, Food Technology and Nutrition; Wiley Encyclopedia of Food Science and Technology; Encyclopedia of Life Support Systems); five books, two book chapters; numerous journals.

Education: BSChE Notre Dame PhD University of California, Berkeley

Awards: AIChE Food, Pharmaceutical and Bioengineering Division Award 1998

Clients: Major food processing and pharamaceutical companies.

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