Atmospheric cold plasma-induced secondary structure modifications of shrimp allergen arginine kinase

Arginine kinase (AK) is a critical shrimp allergen with considerable health risk for sensitized individuals. Despite the growing recognition of food allergies as a public health concern, understanding the effects of emerging processing technologies on shrimp allergens has become an important research topic. This study assessed the effects of pin-to-plate dielectric barrier discharge atmospheric cold plasma on the secondary structure of AK purified from whiteleg shrimp (Litopenaeus vannamei). Plasma was applied either directly to purified AK solutions or to shrimp muscle before protein purification. All samples and untreated controls were subjected to Fourier-transform infrared spectroscopy (FTIR) for secondary structure analysis. The Amide I region spectra revealed measurable alterations, including a 3-7% reduction in α-helix, a 7-19% increase in β-sheet, and decreases of 1-4% and 3-8% in β-turn and random coil, respectively. Longer plasma exposure time (10 vs. 5 min) resulted in a greater magnitude of these changes. Also, directed exposure of purified protein induced more significant changes than plasma pretreatment of the shrimp muscle. Findings demonstrate plasma capability in non-thermal modification of the secondary structure of shrimp AK and establish a foundation for future studies on how structural changes affect allergen stability and immunological reactivity.