Laika Jessica, Sabatucci Annalaura, Sacchetti Giampiero, Di Michele Alessandro, Molina Hernandez Junior Bernardo, Ricci Antonella, Dalla Rosa Marco, Chaves Lopez Clemencia, Neri Lilia
Department of Bioscience and Technology for Agriculture, Food and Environment, University of Teramo, Teramo, Italy.
Department of Physics and Geology, University of Perugia, Perugia, Italy.
J Food Sci. 2024 Dec;89(12):9283-9298. doi: 10.1111/1750-3841.17599. Epub 2024 Dec 14.
Polyphenol oxidase (PPO) is among the most detrimental enzymes in processed plant foods, being responsible for enzymatic browning. To propose a "mild" alternative to traditional enzymatic inactivation methods, this study investigated the effect of cold atmospheric plasma (CAP) on PPO inactivation and highlighted the role of different sugars on both inactivation and structural modification of this enzyme. Different model systems were prepared in phosphate buffer using a purified PPO either alone or added with glucose, fructose, sucrose, and trehalose at different concentrations. CAP treatments (6 KV; 23 KHz; duty cycle 10%) were applied at times ranging from 5 to 30 min. Different spectroscopic analyses were conducted before and after treatments to evaluate the PPO activity and changes in tertiary and secondary structures. CAP induced a significant reduction (p < 0.05) in PPO activity across all systems, ranging from 70% to 94% after 30 min of treatment. Among sugars, fructose enhanced (p < 0.05) the PPO inactivation (+23% on average with respect to the phosphate buffer system), possibly by promoting the loss of secondary structures containing the copper-binding site of the catalytic pocket. The effect of other sugars on PPO inactivation was strictly dependent on their type and concentration; specifically, disaccharides at the highest concentrations and treatment times showed a protective effect on the structure and functionality of the protein. Thus, the results of this study highlight that sugars can modulate the effectiveness of CAP, offering promising perspectives for optimizing this food processing technology. PRACTICAL APPLICATION: Cold atmospheric plasma (CAP) is a promising nonthermal technology for food preservation. In particular, surface dielectric barrier discharge (SDBD) CAP could be applied as an alternative to chemical and thermal treatments to inactivate polyphenol oxidase (PPO), an enzyme responsible for browning reactions and quality loss in most processed fruit and vegetable products. However, as shown by this study, PPO inactivation induced by CAP is affected by sugars. Specifically, fructose can positively influence the inactivation of this enzyme. Therefore, CAP potentially could find main applications for the PPO stabilization of high fructose-content plants (e.g., pears, apples, bananas, grapes, peppers, and squashes).
多酚氧化酶（PPO）是加工植物性食品中最具危害性的酶之一，它会导致酶促褐变。为了提出一种比传统酶失活方法“温和”的替代方法，本研究调查了冷常压等离子体（CAP）对PPO失活的影响，并强调了不同糖类在该酶失活和结构修饰中的作用。在磷酸盐缓冲液中制备了不同的模型体系，使用纯化的PPO，单独使用或添加不同浓度的葡萄糖、果糖、蔗糖和海藻糖。CAP处理（6千伏；23千赫兹；占空比10%）的时间范围为5至30分钟。在处理前后进行了不同的光谱分析，以评估PPO活性以及三级和二级结构的变化。CAP使所有体系中的PPO活性显著降低（p<0.05），处理30分钟后降低幅度为70%至94%。在糖类中，果糖增强了（p<0.05）PPO的失活（相对于磷酸盐缓冲液体系平均提高23%），这可能是通过促进包含催化口袋中铜结合位点的二级结构的丧失来实现的。其他糖类对PPO失活的影响严格取决于它们的类型和浓度；具体而言，最高浓度和处理时间下的二糖对蛋白质的结构和功能具有保护作用。因此，本研究结果表明糖类可以调节CAP的有效性，为优化这种食品加工技术提供了有前景的思路。实际应用：冷常压等离子体（CAP）是一种很有前景的食品保鲜非热技术。特别是，表面介质阻挡放电（SDBD）CAP可以作为化学和热处理的替代方法，用于使多酚氧化酶（PPO）失活，PPO是大多数加工水果和蔬菜产品中导致褐变反应和质量损失的一种酶。然而，如本研究所示，CAP诱导的PPO失活受糖类影响。具体而言，果糖可以对该酶的失活产生积极影响。因此，CAP可能主要应用于高果糖含量植物（如梨、苹果、香蕉、葡萄、辣椒和南瓜）的PPO稳定化处理。
