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• Reliable Power – steady temperatures are needed for proper roasting/cooking
• High Electricity Costs – Nearly a quarter of the country’s nut processing plants are in California , where energy costs continue to rise
• High thermal loads
Reciprocating engines, with a power size range of 30kW–8MW, generate engine jacket heat from 180-200°F, and exhaust heat at around 1200 °F. Industrial turbines, with a power range from 1-20+ MW, generates heat from 900-1100°F. This heat can be recovered and used to heat or cool products in a variety of food processing steps such as:
• Ovens can reach temperatures up to 800 degrees F (EPA)
• Hot water and steam are sometimes used for blanching
• In some processes, nuts must be dried with warm air to achieve the appropriate moisture content
• Nuts must be cooled immediately after roasting with cooled air to prevent over-cooking
When harvested peanuts arrive at the processing plant, the nuts are separated from plant material, such as stems and leaves, and soil. If the nuts are to be roasted in-shell, they are washed in wet, coarse sand to remove dirt and discoloration, and then are dried in by powdering them with talc or kaolin. Otherwise, the shells are removed, and the nuts are roasted and blanched. In dry-roasting, the nuts are roasted at 800 degrees F for 40-60 minutes using either a gas-fired rotating oven, or a conveyor belt with countercurrent hot air. In oil-roasting, nuts are cooked in a tank of oil heated to around 300 degrees F for 3-10 minutes. Nuts are cooled immediately after roasting with cool air to prevent overcooking.
The nuts are cleaned (skin, dust, etc. removed) in a process called blanching. Blanching may take place using one of four techniques. Dry blanching involves heating the nuts to just below 300 degrees F to loosen the skin, and then passing the nuts through coarse brushes or ribbed rubber to remove the skin. In water blanching, the skins are first slit, and then removed using hot water sprayers. The nuts must be dried back to their original moisture content. Nuts may be steam blanched by exposing the nuts to steam, and then placing them on revolving spindles that move down a grooved corridor and unwrap the peanut skin. Finally, nuts may be air blanched by placing the nuts on a revolving, abrasive surface and exposing them to a countercurrent of air. (EPA)
After nuts are roasted, they may be further processed into peanut butter. Peanuts must first be ground alone, and then ground with salts, sweeteners, and a stabilizer to prevent separation of the oily phase. (Peanut Butter Lovers)
Peanut & Treenut Processors Association
American Peanut Council
American Peanut Council Fall Conference - September 13-14, 2004
American Peanut Council Winter Conference - December 8-10, 2004
PTNPA Annual Conference & Trade Show - January 22-25, 2005
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