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Food enzymes as affected by high intensity pulsed electric fields |
G. V. BARBOSA-CÁNOVAS1, O. Martín2, and P. Elez-Martínez2. (1) Dept. of Biological Systems Engineering, Washington State Univ., 220 L.J. Smith Hall, PO Box 646120, Pullman, WA 99164-6120, (2) Dept. of Food Technology, Univ. of Lleida, UTPV-CeRTA, Av. Alcalde Rovira Roure, 191, Lleida, 25198, Spain A new food processing technology, high intensity pulsed electric fields (HIPEF), is currently being investigated due to its inactivation of undesirable microorganisms and enzymes with limited increase of food temperature. As a result, it is now possible to obtain more stable foods with fewer changes in composition, physicochemical properties, and sensory attributes. Several studies exist on the effects of HIPEF on enzymes suspended in aqueous solutions, and in real foods like fruit juices and milk, which are products of great importance to the food industry. The enzymes studied have been pectinmethylestearase, polyphenoloxidase, polygalacturonase, peroxidase, alkaline phosphatase, proteases, lipases, and others such as lipoxygenase, lactate dehydrogenase, a-amylase, glucose oxydase, lisozyme, pepsin, and papain. Depending on the particular enzyme, the media used for suspension, and the HIPEF treatment conditions, most enzymes are almost completely inactivated while others show resistance to HIPEF processing. Electric field intensity, treatment time, number of pulses, pulse width, pulse waveform, field polarity, frequency, and treatment temperature are HIPEF factors that can have significant effects on enzyme inactivation. The factors that influence enzyme inactivation the most are field strength and treatment time. Enzyme inactivation has been described as an exponential function of treatment time or field strength and also by means of empirical models such as Hülsheger’s and Fermi’s. The mechanism of enzyme inactivation by HIPEF is still unclear and HIPEF processing may affect the native structure of enzymes and therefore could promote changes in enzymatic activity. Further investigation on enzyme inactivation is required to 1) better control the critical points involved, 2) achieve higher levels of inactivation, 3) learn more about the mechanism of enzyme inactivation, and 4) enable the scale-up of the technology for the food industry.
Session 23, Pulsed electric fields: An update
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