Effects of high voltage atmospheric cold plasma treatment on microbial diversity of tilapia (Oreochromis mossambicus) fillets treated during refrigeration.

Fresh tilapia fillets are susceptible to perish due to the microbial contamination during storage. High voltage atmospheric cold plasma (HVACP), a non-thermal technology, can effectively inactivate various microorganism. The aim of this study was to identify the microorganism amount and diversity changes of fresh tilapia fillets during refrigerator storage after HVACP treatment. Samples were treated at 70 kV for 1, 3 and 5 min by dielectric discharge barrier (DBD) cold plasma then stored at 4 °C. During the storage, amounts of Total viable bacteria (TVB), Psychrophilic bacteria, Pseudomonas spp., Lactic acid bacteria, Enterobacteriaceae, H2S-producing bacteria were measured, and microbial diversity of samples was analyzed. Long treatment time showed a great reduction effect on amounts of all bacteria. When tilapia fillets were treated at 70 kV for 5 min and stored for 12 d, amounts of TVB, Pseudomonas spp. and Enterobacteriaceae were 7.15, 6.99 and 4.23 log CFU/g, respectively, which were significantly lower (P < 0.05) than those in control group. High-throughput sequencing results showed that microbial diversity of tilapia fillets treated by HVACP was fluctuated as storage time extend, microbial species richness was decreased during first two days, and increased to the peak till 9 d, then decreased again. The dominant bacteria in fresh samples were Acinetobacter, Macrococcus, Pseudomonas, and Lactococcus. The abundance of both Acinetobacter and Macrococcus were decreased gradually during storage, while the abundance of Lactococcus was increased at first 3 d then decreased. After 12 d of storage, the dominant bacteria were transformed into Pseudomonas, Arthrobacter, and Kurthia.

Improved gel functionality of myofibrillar proteins incorporation with sugarcane dietary fiber.

The effects of sugarcane dietary fiber (SDF) on the gelation properties of porcine myofibrillar proteins (MP) were studied to understand its mechanism of action in improving gel functionality. Rheological tests on all composite gels (MP with SDF) showed the visco-elastic nature of MP, but the G' significantly increased with contents of SDF and with particle size (P<0.05). However, the δ exhibited the opposite effect. Light microscopy suggested that SDF affected moisture distribution in the gel by drawing water from MP and homogenously embedded in gelation. It is proposed that during the heating the more concentrated MP promoted the unfolding of MP chains and facilitated the formation of ß-sheet instead of α-helices, leading to a compact and homogenous three-dimensioned network. These results indicated that the SDF changed the water distribution and resulted in the enhanced gelation which reacted to firmly bind SDF and form a synergistic interaction system.