|KOSKINIEMI, CRAIG - North Carolina State University|
|Truong, Van Den|
|MCFEETERS, ROGER - Retired ARS Employee|
|SIMUNOVIC, JOSIP - North Carolina State University|
Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2013
Publication Date: 11/1/2013
Citation: Koskiniemi, C.B., Truong, V., McFeeters, R.F., Simunovic, J. 2013. Quality evaluation of packaged acidified vegetables subjected to continuous microwave pasteurization. LWT - Food Science and Technology. 54:157-164.
Interpretive Summary: Microwave technology has the potential to process food products with good quality retention. This occurs because microwave energy provides rapid heating of both liquid and particulate phases based on dielectric properties, as opposed to conventional methods, which rely on heat transfer by convection and conduction. This research illustrates the application of continuous microwave processing technology to pasteurize acidified vegetable packs for shelf-stability. Pasteurization temperature of 75 ºC, the industrial standard for thermal processing of acidified vegetables, can be reliably achieved by rotating the packs by 180º in the microwave tunnel for increasing exposure of the cold spots in the packs to incident microwaves. The pasteurized product with good retention of color and firmness of acidified vegetable pieces were microbiologically stable under incubation at 30 ºC for at least 60 days. This study demonstrates a feasibility of using continuous microwave systems for pasteurizing packaged acidified vegetables.
Technical Abstract: The study evaluated the use of 915 MHz continuous microwave processing with a rotation apparatus for pasteurization of acidified vegetable packages. Broccoli florets, and 1.2 cm cubes of broccoli stems, red bell pepper, and sweetpotato were pre-equilibrated to 1 g/100 g NaCl and 0.38 g/100 mL citric acid, and separately placed in 110 mL cups with a 0.5 g/100 mL citric acid solution. Unsealed packages were placed on a conveyor belt and run through a 915 MHz microwave cavity operating at 3.5 kW (residence time = 4 min). After processing, cups were sealed with a lidding film, and held in insulating molds for 30 min. Infrared thermocouples, fiber optic temperature sensors, and infrared imaging were used to monitor product temperatures. Microbial stability and changes in color and instrumental textural properties were measured over a 60-day storage period at 30 °C. Good retention of color and texture of acidified vegetable pieces was observed after microwave pasteurization. Over storage, textural properties significantly degraded for all vegetables, but the brilliant color of red bell pepper and sweetpotato was relatively retained. Chemical indicators of microbial spoilage were not detected at the end of storage. This study demonstrates a successful continuous microwave pasteurization process for producing shelf-stable acidified vegetable packages.