title: Impact of the O2 concentrations on bacterial communities and quality of modified atmosphere packaged Pacific white shrimp (Litopenaeus vannamei).
abstract: The importance of spoilage-related bacteria in fresh Pacific white shrimp (Litopenaeus vannamei) under different modified atmospheres (MAs) at 4 °C and the effect of O2 were demonstrated in the current study. The changes of bacterial communities in MA-packed shrimp during cold storage were studied by a combined method of plate counts with isolation and identification. Three gas mixtures were applied: 80% CO2 /5% O2 /15% N2, 80% CO2 /10% O2 /10% N2 and 80% CO2 /20% O2, and unsealed packages of shrimp were used as the control. In addition, the TVB-N, pH, whiteness index, and sensory scores were also determined to evaluate the quality changes of shrimp. MA packaging effectively inhibited the increase of total psychrotrophic bacteria counts and H2 S-producing bacteria counts by about 1.7 and 2.1 log cycles, respectively. The growth of Gram-negative spoilage bacteria in shrimp, including Shewanella spp., Aeromonas spp., and Pseudomonas spp., was inhibited by MA packaging, but the growth rate of Gram-positive bacteria such as lactic acid bacteria (LAB) and Brochothrix spp. were less affected by MA as effectively as Gram-negative bacteria. In comparison with the MA-packaged samples, the counts of H2 S producers in shrimp under a CO2 -enriched atmosphere with 20% O2 were slightly lower than the count in samples under an atmosphere with 5% O2 . However, MA with 20% O2 led to higher concentrations of TVB-N, and lower whiteness values and sensory scores. The shelf life of shrimp under 80% CO2 /10% O2 /10% N2 has been prolonged by > 6 d in comparison with the control according to the sensory scores.
authors: Shanghai Engineering Research Center of Aquatic Product Processing & Preservation College of Food Science & Technology, Shanghai Ocean Univ., Shanghai, 201306, P. R. China.
authors: Yun-Fang
authors: YF
authors: Qian
authors: Sheng-Ping
authors: SP
authors: Yang
authors: Jing
authors: J
authors: Xie
authors: Qing
authors: Q
authors: Xiong
authors: Zhi-Li
authors: ZL
authors: Gao
mesh_terms: D000333:Aeromonas / Q000302:isolation & purification; D000818:Animals; D002245:Carbon Dioxide / Q000032:analysis; D015169:Colony Count, Microbial; D005506:Food Contamination / Q000517:prevention & control; D005516:Food Microbiology; D018857:Food Packaging / Q000379:methods*; D063427:Food Quality; D006094:Gram-Positive Bacteria / Q000302:isolation & purification; D009584:Nitrogen / Q000032:analysis; D009812:Odorants / Q000032:analysis; D010100:Oxygen / Q000032:analysis*; D033561:Penaeidae / Q000382:microbiology*; D011549:Pseudomonas / Q000302:isolation & purification; D012034:Refrigeration; D012758:Shellfish / Q000382:microbiology*; D020592:Shewanella / Q000302:isolation & purification
chemical_list: D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen
keywords: Litopenaeus vannamei; microbial ecosystem; modified atmosphere packaging; phenotypic identification; quality