Tuesday, February 20, 2018

Electric IR Heating To Peel Tomatoes: A Water Saving, Cost-effective, and Eco-friendlier Alternative

infrared heating for peeling tomatoes
For almost a decade now the development of non-chemical peeling technology has recently been identified as a top priority at the for the California Food Processing and Beverage Industry.

Lye peeling is the most industrially used method for processing tomatoes in the U.S. However, due to the pressure of cost and environmental regulations, some tomato processors were forced to use steam peeling to reduce chemical contamination of water. Unfortunately, steam peeling produces undesirable products with deteriorated peeling appearance, high loss in firmness and lowered yields.

Existing studies about the success of IR radiation heating for peeling of potatoes prompted interest in using the same technology for tomatoes. Initiatives for pilot plants and testing began.

A pilot-scale infrared tomato dry-peeling system was designed, built, and tested. It consisted of a section for feeding of the tomatoes, the infrared heating section, a peel eliminator, and the discharge section.

The IR heating unit is equipped a number of IR emitters and an automatically controlled variable speed conveyor system.  Surface temperature of tomatoes was measured immediately after IR heating using non-contact IR thermometers that gathered three different measurements on each tomato. The controlled temperatures were in the range of 103 deg. C to 110 deg. C. In this range, a yield of 70%- 85% fully peeled tomatoes could be obtained for all tomatoes sizes, depending on variety and maturity stage.

Since IR heating does not use water as a heating medium, the process can be referred to as “IR dry-peeling”. Early results showed infrared (IR) heating for peeling tomatoes as having "remarkable and promising" potential for commercialization by the food industry.

Because no water and salt are used in the new peeling process, IR dry-peeling could be the solution for long-term water supply and salinity problems caused by lye peeling. IR dry-peeling also reduced the tomato peeling loss significantly and resulted in similar or better firmness of the product with similar heating time compared to hot lye peeling. The reduced peeling loss and high product quality mean that more valuable and premium products can be produced. Because no salt is used in the peeling, the skins do not contain added salt and can be easily utilized as value-added food products.

Major Advantages to Infrared Dry Peeling:
  • The average percentage of fully peeled tomatoes obtained from the IR peeling system was much higher than that from steam peeling. 
  • The IR peeled tomatoes had a much better texture than the steam peeled ones.
  • A commercial infrared peeling system is predicted to save about 22 percent and 28 percent of the energy when compared to energy used by steam and lye peelings.
  • No water and chemicals are required for the infrared peeling system so there will be no need to treat any wastewater after the peeling process.