Original article Microbiological, physical and chemical characteristics of freshwater prawns (Macrobrachium rosenbergii) in modified-atmosphere packaging Julia S. Simoes, 1 * Eliane T. M arsico, 1 C esar A. L azaro, 1,2 Micheli da S. Ferreira, 1 Robson M. Franco, 1 Ana Paula A. A. S. Pereira 1 & Carlos A. Conte-Junior 1 1 Department of Food Technology, Veterinary School, Federal Fluminense University, Niteroi, Brazil 2 Facultad de Medicina Veterinaria, Universidad Nacional Mayor de San Marcos. Lima, Per u (Received 4 April 2014; Accepted in revised form 21 July 2014) Summary This study evaluated the influence of packaging atmosphere (air versus 50% N 2 /50% CO 2 ) on microbio- logical (mesophiles, psychrotrophs), physical (gas measurement) and chemical (pH, total volatile basic nitrogen [TVB-N], NH 3 ,H 2 S and biogenic amines) parameters in freshwater prawns during storage at 0 Æ 1 °C for 240 h. To select the most appropriate packaging, 21 batches of each treatment were analy- sed. Both the packaging permeability and the combination of gases affected the shelf life, but the modi- fied-atmosphere packaging (MAP) was more efficient than air packaging, increasing the shelf life by 40 h. The parameters of pH and TVB-N showed no statistical difference between the two atmosphere condi- tions all along the storage period. The biogenic amine agmatine showed potential for use as a quality indicator due to the increased concentration during storage. In further studies, this amine can be applied as an indicator for public health issue. Keywords Biogenic amines, food quality, Macrobrachium rosenbergii, modified-atmosphere packaging, shelf life. Introduction Farming of freshwater prawns has increased over the years and is still the main production method for these crustaceans (New et al., 2012). Although widely mar- keted, prawns are highly perishable because of their high content of low-molecular-weight metabolites, such as free amino acids and nucleotides, resulting from hepatopancreas autolysis (Gokoglu & Yerlikaya, 2008; Nirmal & Benjakul, 2009). Because of the lack of established quality parameters for freshwater prawns, some researchers have used the same parameters as for marine shrimp. Non-nitrogenated substances and free amino acids are suitable substrates for the develop- ment of microorganisms, which can form volatile metabolites including ammonia, organic acids, hypo- xanthine, acetate and volatile compounds of sulphur, resulting in off-flavours, and also nonvolatile com- pounds such as biogenic amines (Gram & Dalgaard, 2002; Silva et al., 2011; Monteiro et al., 2012; Carnei- ro et al., 2013a,b; Santos et al., 2013). In stored products, biogenic amines (BA) are gener- ated by the action of spoilage-bacteria decarboxylases (Ten Brink et al., 1990; L azaro et al., 2013; Matejkov a et al., 2013). Determination of the BA content in food is important because of the potential toxicity and sig- nificance for human health (Rodriguez et al., 2014). Some researchers have examined the possibility of using these compounds as food-quality markers in nonfermented foods such as meat and fish during stor- age (Zhao et al., 2007; Fadhlaoui-Zid et al., 2012; Rodrigues et al., 2013). Modified-atmosphere packaging (MAP) has the potential to control chemical, enzymatic and microbio- logical reactions, minimising the major sources of the degradation that occurs during the storage period (Church & Parsons, 1995; Sivertsvik et al., 2002). An appropriate combination of the gases O 2 ,N 2 and CO 2 in the package can inhibit spoilage microorganisms that grow under aerobic conditions, thus maintaining the sensory quality of the food matrix (Monteiro et al., 2013). The presence of oxygen in the package reduces the amount of exudates from fish during storage (Davis, 1995). This is important because drip loss could favour the growth of spoilage bacteria. Although some researchers have evaluated different fish-packaging materials (Pacquit et al., 2007; Monteiro et al., 2013), *Correspondent: E-mail: julia_simoes@hotmail.com International Journal of Food Science and Technology 2015, 50, 128–135 doi:10.1111/ijfs.12644 © 2014 Institute of Food Science and Technology 128