Susceptibility of dry-cured tuna to oxidation and biogenic amines generation related to microbial status and salting/curing technology

The present study evaluated the effect of salting/curing methods and raw tuna flesh microbial status on the lipid oxidation and the incidence of biogenic amines in “muxama”, a dry tuna product. After drying (T0), salted/cured and uncured “muxamas” processed in the air presented malondialdehyde (MDA) levels lower than those under vacuum (P < 0.05) with differences amounting to 53.18% and 50.84%, respectively. Regardless the salting method, MDA content tended to increase with storage, with lipid oxidation progressing faster in uncured samples. The microbial status of fresh muscles kept almost unchanged or slightly decreased after salting under vacuum, with Enterobacteriaceae counts falling below 10 cfu/g. T0 cured “muxamas” differed in the microbial status, with the initial total counts at 30 °C (1.6x104 cfu/g) remaining almost unchanged (4.9x104 cfu/g) or increasing from 5.9x103 cfu/g to 1.6x107 cfu/g, reflecting distinct microbial survival among the flora under the present NaCl and Aw conditions. Histamine in fresh tuna muscle varied between 4.19 and 2305 mg/kg (dry matter) without detectable spoilage signs between samples. After processing and storage, BA profiles also changed, expressing distinct microbiota evolutions, with histamine content keeping below legislated values or increasing from 26.39 mg/kg up to 208.21 mg/kg (T0), 1179.20 mg/kg (T1) and 1107.35 mg/kg (T3). Muxama is susceptible to lipid oxidation and BAs formation.