Pulsed electric field treatment applied to microbreweries for processing craft beer

热处理方法，如巴氏杀菌，主要用作灭活腐败微生物的手段。然而，热处理方法是高耗能的，并且对腌制食品的营养和感官质量产生不利影响。近年来，诸如脉冲电场(PEF)技术等非热过程已经被研究用于商业应用。PEF器件由一对导电的金属电极组成，它们之间的间隔为已知的间隙距离。高压脉冲施加到其中一个电极上，同时将另一个电极保持在地电位。由此产生的电场导致细胞膜的可逆破裂，因此微生物失活。加拿大的啤酒厂法规不要求精酿啤酒进行巴氏杀菌；因此，PEF工艺在酿造行业得到了潜在的应用。PEF处理是一种非加热处理，与传统的热巴氏杀菌相比，更好地保留了新鲜的口感和营养价值。然而，由于脉冲电场加工过程中的电流流动，金属离子从电极中释放出来。释放的金属量取决于产品的类型、电极的具体成分和使用的脉冲类型。这项拟议的研究通过一个旨在消除大多数金属离子释放的加压加工室来调查PEF工艺在精酿啤酒中的适用性。在滑铁卢大学和Innocente Brewing Company的大力合作下，我们有信心使用改进后的UW的PEF设施来展示精酿啤酒的PEF巴氏杀菌的有效性。正在考虑进行系统的测试，精确控制施加的脉冲、处理时间和其他参数，如介质温度和能量，以评估在PEF加工过程中释放的金属离子及其对口感和保质期的影响(如果有的话)。作为这项研究的结果，预期的知识和技术对微型啤酒厂推广其新的优质产品有直接好处。

Heat treatment methods such as thermal pasteurization are predominantly utilized as a means to inactivatespoilage microbes. However, heat treatment methods are energy intensive and adversely affect nutritional andorganoleptic quality of the preserved food. In the recent years non-thermal processes like pulsed electric field(PEF) technology has been investigated for commercial applications. PEF devices consist of a pair ofelectrically conductive metal electrodes, separated by a known gap distance. High voltage pulses are applied toone of the electrodes while keeping the other electrode at ground potential. The resulting electric field causesirreversible breakdown of cell membrane; hence microbial inactivation.Brewery regulations in Canada do not necessitate pasteurization of craft beer; hence, PEF processing finds apotential application in the brewing industry. PEF treatment being a non-thermal, the fresh like taste and thenutritional value are better retained than with conventional thermal pasteurization. However, due to the flow ofcurrent during the PEF processing, metal ions are released from the electrodes. The amount of metal releaseddepends on the type of product, the specific composition of electrodes and the type of pulses used. Thisproposed research investigates the applicability of the PEF processing to craft beer, through a pressurizedprocessing chamber that has been designed to eliminate release of most metal ions.With a strong cooperation between the University of Waterloo and Innocente Brewing Company, we areconfident in demonstrating the effectiveness of the PEF pasteurization for craft beer, using the modified UW'sPEF facility. Systematic tests with precise control of the applied pulse, treatment time, and other parameters,like medium temperature and energy are being considered to evaluate metal ions released during the PEFprocessing and their consequent effect, if any, on the taste and the shelf life. The knowledge and technologythat are expected as outcome of this research are of direct benefit for microbreweries in promoting their newpremium products.