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About 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.

You are here: Experts > Industry > Food Engineering > Food Engineering/Manufacturing > head space in pressurized home canned foods

Food Engineering/Manufacturing - head space in pressurized home canned foods

Expert: J. Peter Clark - 10/22/2009

Question
Hi. I use a pressure canner to process low acids foods. Recently I processed some pumkin. I mashed it up, as my trusty old Joy of Cooking told me to and processed it for 90 minutes at 12 pounds of pressure. Some of the cans spewed some of the contents out into the water. The seal on the cans is good and the food inside looks fine. Will this affect the shelf life of that food? Should I use it sooner or is it ok that the jars are only 2/3 of the way full instead of only having 1 inch headspace. Also I have found alot of conflicting opinions on wether to mash the pumpkin or just cube it. Which is better?

Answer
Sara,

My guess is that you overfilled the jars and had some entrained air. When they heated up, the contents expanded and blew out. Once the internal pressure was relieved, a vacuum was formed with what was left and the seal formed. The contents should be fine. In the future, with mashed pumpkin, you may need to stir carefully and cook to remove air. Cubes will hold less air. You need to leave some space at the top for expansion and maybe heat up more slowly. Follow canning directions carefully.

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