Action of plasma-activated lactic acid on the inactivation of inoculated Salmonella Enteritidis and quality of beef

This study aimed to investigate the effects of plasma-activated lactic acid (PALA) on Salmonella Enteritidis and beef quality. To improve the antibacterial efficiency of plasma-activated water (PAW), plasma-activated lactic acid (PALA) was prepared by treating lactic acid (0.05-0.20%) with a plasma jet for 40 to 100 s with subsequent application to the surfaces of beef slices (50 x 50 mm, approximately 10 g). Slices were analyzed for changes in surface color, pH, lipid oxidation and odor. In addition, secondary structure (beta-sheet and random coil) of the beef protein was determined using Fourier transform infrared spectrometer. We showed that the antibacterial activity of PALA was closely related to the reaction of NO2- with H2O2 as well as the decomposition of NO2- under acidic conditions. UV-treated fresh beef slices were spot-inoculated with Salmonella Enteritidis (5.67 log CFU/g) and then immersed in PALA solutions for 20 s; leading to a reduction ranging from 1.24 to 3.52 log CFU/g. Data indicated that there was no negative effect of PALA on beef quality parameters. This study not only provided a theoretical basis for developing a novel decontaminant but also enabled PALA to find a way for practical application. Industrial relevance: In China, a high concentration of lactic acid (2.0-2.5%) is a widely used bactericidal agent in the beef industry. However, it has a negative effect on the odor and protein of the product. The meat industry faces challenges in achieving the balance between the antimicrobial effect on meat and the quality of the product. Based on this, plasma-activated water (PAW) is a hopeful alternative decontaminant for microbial inhibition on meat, made by treating water with non-thermal plasma, containing reactive species, ions and charged particles, which is safe and environmentally friendly. This study demonstrated that plasma-activated lactic acid (PALA) was more effective and stable than PAW. The PALA treatment of beef slices not only led to the reduction of Salmonella Enteritidis but maintained beef quality. PALA appears a promising decontaminant for the meat industry.