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Design and development of a pilot-scale pulsed electric field processing system for microorganism inactivation in orange juice

บทคัดย่อ

In the beverage processing industry worldwide, orange juice is the most widely manufactured juice. Conventional preservation methods such as thermal pasteurization ensure safety and extend the shelf life of orange juice. However, they often lead to detrimental changes in the sensory qualities of the food product. High-quality and nutritious foods, with fresh flavor, texture, and color, having minimal or no chemical preservatives, and above all safe for consumption, are required by consumers Chan et al (1997); Michelle et al (2004); Cortes  et al (2008). Therefore, newly developed food technologies usually focus on preservation while maintaining food quality attributes. Non-thermal pasteurization by pulsed electric field (PEF) processing has already been introduced. It can alternatively be applied to deliver safe and shelf-stable products such as juices, milk, yogurt, soups, and liquid eggs with fresh-like character, high nutritional value, and minimal or no chemical preservatives Sale et al (1968); Hulsheger et al (1981); Fleischman (2014); Jeyamkondan et al (1999). The PEF pasteurization process utilizes micro-second (µs) high-voltage pulses, producing high electric field strength (> 20 kV/cm) between the two electrodes. These electric pulses are applied to food products, at temperatures below thermal pasteurization, efficiently inactivating contaminating microorganisms without significantly affecting the quality of the food product by a phenomenon known as the electroporation phenomenon Sale et al (1968); Hulsheger et al (1981); Fleischman (2014); Jeyamkondan et al (1999). Generally, a PEF processing system consists of a high-voltage power source, an energy storage capacitor bank, a charging resistor, a discharge switch, a pulse controller, and a treatment chamber. Electrical energy from the power supply was stored in the capacitor and was then discharged through the treatment chamber to generate electric field strengths in the food product. The survival rate of the number of microorganisms in food products treated by PEF processing depends on process parameters, including electric field strength, total treatment time, pulse width, pulse waveform, and food conductivity Fleischman (2014). In the past several decades, there have been numerous research studies and developments on the PEF processing system for microorganism inactivation of food juice products Sale et al (1968); Hulsheger et al (1981); Fleischman (2014); Jeyamkondan et al (1999). (Ohshima et al, 1997, 2007); Sen-in et al (2012); Panyamuangjai

et al (2012); Intra et al 2015; Mcdonald et al (2000); Gupta et al (2003);

Qin et al 1998. Available commercial-scale PEF processing has been designed to inactivate microorganisms in tomato-orange juices Min et al (2003); Linton et al (2003). However, these commercial-scale PEF systems tend to be relatively large units, which are quite expensive with typical starting prices greater than ten thousand U.S. dollars. In Thailand, commercial-scale PEF processing systems are not available for the micro, small, and medium-sized enterprises in the food and drink industries because of their high cost and enormous size. Therefore, a PEF processing system for micro, small, and medium-sized enterprises in the food and drink industries must have a low cost, a small and simple system, easy to use and clean, and its maintenance must be possible by low-skilled laborers.

This study aimed to develop and investigate a low-cost, simple PEF processing system for the inactivation of microorganisms in orange juice. In this paper, A detailed description of the pulsed electric field system design is also presented. The MATLAB/Simulink was used to simulate the 3-phase pulse high-voltage source circuit. The inactivation of endogenous microorganisms (E - coli) in orange juice and the quality of orange juice were experimentally investigated, and the quality of pulsed electric field processed orange juice was compared with that of thermally processed orange juice.