AboutJ. 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.
Question Dear Peter,
When you use concentrate instead of 100% fresh juice, what nutrients do you lose?
I also have a question about preservatives. I notice that, for example, some grape juice, apple juice or cranberry juice that made out of concentrate have no preservatives ( just concentrate and water), others contain juice, water and preservatives.Why in one case the preservatives are not needed and in the other case the preservatices are there?
These days consumers all try to avoid the preservatives so I would think the manufacturers will try to do the same if they can.
Last, when you make carbonated juice out of concentrate, do you add water to the concentrate then add carbonation, or do you just add concentrate to carbonated water?
I truly appreciate your time input,
Lucy
Answer There is more loss of flavor than of nutrients in making juice concentrates. Concentration is usually done by evaporation, which involves heating under vacuum. This also helps preserve the juice, which is why reconstituted juice, made from concentrate and water, may not need preservatives. Fresh juice is subject to spoilage and is usually stored under refrigeration but can still spoil slowly, so has preservatives added, which are still there when mixed with water, sweetener and acid to make juice-based drinks. A good example is fresh apple cider, which even in a refrigerator will turn hard fairly quickly because it has live yeasts in it.
For carbonated beverages, carbon dioxide is usually added at filling, so one would normally reconstitute the juice then carbonate, but it might work the other way. The problem is carbon dioxide escapes quickly if not under pressure, so carbonated water would start to lose its fizz.
