Volatile compounds associated with Psychrobacter spp. and Pseudoalteromonas spp., the dominant microbiota of brown shrimp (Crangon crangon) during aerobic storage

Abstract

The spoilage potential of several Psychrobacter and Pseudoalteromonas species (Psychrobacter cibarius, Psychrobacter maritimus, Pseudoalteromonas elyakovii, Pseudoalteromonas paragorgicola and Pseudoalteromonas nigrifaciens) was determined and quantified based on the presence of volatile organic compounds (VOCs). Psychrobacter and Pseudoalteromonas species dominate the microbiota of cooked brown shrimp (Crangon crangon). Additionally, API ZYM analyses determined the species' enzymatic capacity to contribute to spoilage by degrading lipids, amino acids and proteins. The bacterial species used in this study were isolated from cooked brown shrimp during storage under different storage and processing conditions and were selected for analysis of their spoilage potential based on their difference in the (GTG)₅-rep profile, 16S rRNA and gyrB sequences and API ZYM profile. The isolates were inoculated as pure cultures on heat-sterilised shrimp. The inoculated samples were stored at 4 °C and the production of VOCs by the pure strains on the shrimp matrix was identified via gas chromatography coupled to mass spectrometry (GC-MS). VOC production was quantified daily by selected ion flow tube mass spectrometry (SIFT-MS) until the bacterial count exceeded 10⁸-10⁹ cfu/g. The sensory profile of Psychrobacter species revealed very low spoilage potential as measured by the production of VOCs, but these species may nevertheless contribute to spoilage. Based on the API ZYM results, Pseudoalteromonas as well as Psychrobacter species might enhance spoilage by breaking down lipids and hydrolysing amino acids and proteins. Pseudoalteromonas species, especially Psa. elyakovii and Psa. nigrifaciens, have a high spoilage potential and might be responsible for the off-odours produced during spoilage of brown shrimp. These isolates produced significant amounts of volatile compounds such as sulphides, acetone, ammonia, and ethanol, which are all involved in seafood spoilage.

Keywords: Brown shrimp (Crangon crangon); Pseudoalteromonas; Psychrobacter; Spoilage; Volatile organic compounds.