Food Engineering/Manufacturing/vacuum sealing


QUESTION: I have a product that contains ascorbic acid and is a high sugar content with a Ph of below 0.85 and a water activity of below 4.5, could you tell me if it is necessary for me to vacuum seal this product?


I think you mean that pH is below 4.5 and water activity is below 0.85. If so, the product should be shelf stable. Vacuum sealing is common to reduce exposure to oxygen, which can cause spoilage, but does not impact human health. Hot filled products create a vacuum as they cool, which is used to help seal the closure. With high sugar content, ascorbic acid, and the other properties, it sounds like a jam or preserve. It is common to hot fill such products to reduce yeasts and molds, which might cause spoilage, but are not health threats.

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

QUESTION: Mr. Clark,

Thank you so much for your helpful response.  I would like to ask you a few more things.  Our product is not a jelly or jam.  We are wanting to package this product in a PET plastic bottle.  We currently heat the product to 175 degrees, fill at 150 degrees, but when turning over vacuum sealing distorts the container.  We would prefer to cool our product to 125 degrees and not vacuum seal.  However, we do not know the issues with mold or yeast growth if we package this way.  What information could you give us that would help us decide whether to vacuum seal or not.

Happy New Year, Gwen

You do not need to hot fill/vacuum seal because the combination of low water activity and low pH makes the product safe. By heating to 175 F, you kill any pathogens or spoilage microbes that might be there. The only risk is contamination from the bottles and caps, but nothing harmful should grow. I'd suggest at least blowing out any dust from the bottles with clean air. You can do accelerated shelf life testing after filling at 125 F to see if and when spoilage occurs. Holding at 145 F means one day is equivalent to 16 days at 72 F, so you will quickly learn if there is a risk. You could also consider approved chemical preservatives such as potassium sorbate or sodium benzoate.  

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J. Peter Clark


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


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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