Combined effect of high hydrostatic pressure and ultraviolet radiation on quality parameters of refrigerated vacuum-packed tilapia (Oreochromis niloticus) fillets.

This study investigated the effects of high hydrostatic pressure (HHP) and ultraviolet radiation (UV-C), individually and combined, on the physical, chemical and bacterial parameters of Nile tilapia (Oreochromis niloticus) fillets stored at 4 °C for 14 days. Tilapia fillets were divided into four groups: control (untreated samples), UV-C, HHP, and UV-C combined with HHP (UV-C+HHP); UV-C was applied at dose of 0.103 ± 0.002 J/cm2, and HHP at a pressure of 220 MPa for 10 min at 25 °C. All samples were analyzed for total aerobic mesophilic count (TAMC), total aerobic psychrotrophic count (TAPC), Enterobacteriaceae count, pH, lipid oxidation, total volatile basic nitrogen (TVB-N), ammonia (NH3), and biogenic amines. Although UV-C accelerated (P ≤ 0.05) the formation of cadaverine, both UV-C and HHP, alone or together, retarded bacterial growth and delayed the increase (P ≤ 0.05) in pH, TVB-N, NH3 and biogenic amines during refrigerated storage, extending the shelf life of refrigerated tilapia fillets at least 2.5 times considering the TAMC counts. Lipid oxidation was unaffected (P > 0.05) by UV-C radiation, and decreased (P ≤ 0.05) by HHP and UV-C+HHP. HHP alone or combined with UV-C showed higher potential benefits for tilapia fillets preservation considering the positive influence on cadaverine levels and lipid oxidation.

Evaluation of Biogenic Amines Levels, and Biochemical and Microbiological Characterization of Italian-type Salami Sold in Rio de Janeiro, Brazil.

The objective of the present study was to evaluate the levels of biogenic amines (cadaverine, putrescine, tyramine, histamine, spermidine and spermine) by high performance liquid chromatography (HPLC) and the physicochemical (moisture, lipids, proteins, pH, water activity and fixed mineral residue) and microbiological (lactic acid bacteria and aerobic heterotrophic mesophilic bacteria count) characteristics of six Italian-type salami brands sold in the city of Niteroi (Rio de Janeiro, Brazil). The salami showed lactic acid bacteria count from 5.7 to 8.6 CFU•mL-1, and heterotrophic mesophilic bacteria count from 5.8 to 8.7 CFU•mL-1. Three brands showed moisture contents above 35% and one brand had protein content below 25%. The mean values obtained for the amines were: 197.43, 143.29, 73.02, 4.52, 90.66 and 36.17 mg•kg-1 for tyramine, putrescine, cadaverine, spermidine, histamine, and spermine respectively. Two brands presented histamine contents above the legal limit established in 100 mg•kg-1. We concluded that the evaluated salami presented a wide variation in the count of the bacterial groups with a predominance of lactic acid bacteria. The moisture contents indicate insufficient drying before commercialization and protein content had values below the minimum limit determined by the Brazilian legislation. Finally, the levels of biogenic amines found could cause adverse reactions in susceptible consumers, depending of the amount and frequency of intake of these products.

Effect of transglutaminase on quality characteristics of a value-added product tilapia wastes.

The aim of this work was to evaluate the physico-chemical, instrumental color and texture, and sensory qualities of restructured tilapia steaks elaborated with small sized (non-commercial) tilapia fillets and different levels of microbial transglutaminase (MTG). Four concentrations of MTG were used: CON (0 % MTG), T1 (0.1 % MTG), T2 (0.5 % MTG), and T3 (0.8 % MTG). In addition, bacterial content and pH shifts were also evaluated during 90 days of frozen storage. The different levels of MTG did not affect (P > 0.05) either the proximate composition of the restructured tilapia steaks or the bacterial growth during the frozen storage. MTG improved (P < 0.05) cooking yield and instrumental hardness and chewiness as well as sensory (salty taste, succulence and tenderness) attributes; strongly contributing to greater overall acceptance. Therefore, restructured tilapia steaks manufactured with MTG are potentially valued-added products with good consumer acceptance and better purchase-intention than steaks formulated with 0 % MTG.

Determinação de aminas biogênicas em diferentes tipos de queijos por cromatografia líquida de alta eficiência / Determination of biogenic amines in different types of cheese by high-performance liquid chromatography

As aminas biogênicas (cadaverina, espermidina, histamina, putrescina e tiramina) foram determinadas e quantificadas em quatro diferentes tipos de queijos utilizando-se a técnica de cromatografia líquida de alta eficiência (CLAE). Para realizar o estudo, foram adquiridas 10 amostras de cada tipo de queijo – gouda, minas frescal, mozarela e prato – no mercado varejista do Rio de Janeiro. As 40 amostras passaram pelas etapas de extração e derivatização das aminas biogênicas, as quais foram detectadas e quantificadas por CLAE-UV. Para avaliar as diferenças entre os queijos, foram aplicados a análise de variância A nova e o teste de Tukey. Dentre os queijos estudados, o minas frescal apresentou os mais baixos teores de aminas biogênicas (24,26 mg.kg-1), e os teores mais elevados (489,15 mg.kg-1) foram detectados no gouda. Das aminas biogênicas analisadas, a tiramina foi a que demonstrou concentrações mais elevadas (623,60mg.kg-1), e a espermidina, as menores concentrações (0,80 mg.kg-1). Considerando-se os quatro tipos de queijos estudados, o gouda parece ser o que requer maiores cuidados com relação ao monitoramento da presença de aminas biogênicas. A metodologia mostrou-se eficaz para efetuar a detecção e a quantificação das aminas biogênicas nos queijos estudados.