Location: Healthy Processed Foods Research
Project Number: 2030-41000-063-08-T
Project Type: Trust
Start Date: Apr 1, 2010
End Date: Jun 30, 2014
The development of non-chemical peeling technology has recently been identified as a top priority at the Energy Efficiency Roadmap Meeting for the California Food Processing and Beverage Industry. Typically, 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. However, steam peeling produces undesirable products with deteriorated peeling appearance, high loss in firmness and lowered yields than conventional lye peeling. Some studies regarding the application of IR radiation heating for peeling of potatoes have been reported in literature. Since IR heating does not need a heating medium, such as water, the process can be named as “IR dry-peeling”. To address the critical challenge of developing a water and energy efficient peeling method to be used as an alternative of current lye peeling and steam peeling for the tomato industry, we conducted tests of various peeling methods with the support of the California League of Food Processors (CLFP) since 2008. We discovered that using infrared (IR) heating for peeling tomatoes has 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. Therefore, we are proposing this research in order to design and construct a complete prototype continuous IR dry-peeling system for tomatoes that consists of tomato feeding, IR heating, vacuum chamber, pre-skin remover, and peel eliminator sections, and to test the efficacy of the new IR dry-peeling system by evaluating the effect of various processing parameters (IR intensity, heating time, emitter configuration) on the peeling performance and product quality of tomatoes using popular processing tomatoes varieties and finally to provide vital information for industrialization and commercialization of the new peeling technology and work with tomatoes processors, equipment manufacturers, utility companies, and the CLFP to transfer the new peeling technology into commercialization.
Popular processing tomatoes (Lycopersicon esculentum) cultivars like what we have used in our previous study will be used for the tests to optimize the processing parameters and perfect the peeling performance of the system and the quality of the peeled product (peeling throughput, peeling loss, peelability, color and texture of the peeled tomatoes). The first step of this project is to build the IR dry-peeling system for tomatoes. The system will consist of the feeding section, IR heating section, vacuum section, preskin remover section, peel eliminator section, and product inspection ramp. The mode of operation of the system is as follows: The cleaned tomato gets into the feeding line with controlled locations from a hopper. The feeding line transfers the tomato into the IR heating section, which consists of two assembled sets of tubular electric IR heaters and an automatically controlled conveyance system passing through the heating section. The IR heated tomatoes are released into vacuum chamber to induce the skin cracking, and then the tomatoes go through the pre-skin remover and a peel eliminator consisting of opposing (rotating) rollers. The opposing rotating rollers are responsible for the final phase of peel elimination. The final product is conveyed onto the peeled product inspection ramp for collection. The feeding section will have feeding lines designed to achieve specific orientation of the tomatoes as they enters the conveyor at the IR heating section. Tomato will be fed between sets of parallel emitters. The IR heating section (1m high x 0.5m wide) will have tubular electric IR emitters with corresponding reflectors assembled in parallel. The arrangement will facilitate double sided heating and is expected to achieve minimum heating time. The exposure time of tomatoes to IR heat will be regulated by the feeding and conveyor speed which will be automatically controlled. To eliminate shading (tomatoes contacting each other) during conveyance, vertical and lateral displacements are incorporated in conveyor design to allow flexible and multiple tomato vertical and lateral displacements. Peeling loss will be expressed as percentage calculated based on the difference in tomato weights before and after peeling. The color of peeled tomato will be measured and expressed in L*a*b color space. The firmness of the tomato will be measured using fruit texture analyzer. The optimal throughput and design guidelines for large scale IR peeling system will be established. The energy consumption of the system will be evaluated and compared with current processing methods. All results will be analyzed for statistical significance. Progress reports and a comprehensive final report will be developed to document the advantages and characteristics of the IR dry-peeling technology and system.