During yogurt manufacture, the lactose fermentation and organic acid production can be used to monitor the fermentation process by starter cultures and probiotic bacteria. In the present work, a simple, sensitive and reproducible high-performance liquid chromatography with dual detectors, diode array detector and refractive index was validated by simultaneous analysis of carbohydrates and organic acids in goat milk yogurts. In addition, pH and bacterial analysis were performed. Separation of all the compounds was performed on an Aminex HPX-87H column (300×7.8 mm, 9 µm) utilizing a 3 mmol L(-1) sulfuric acid aqueous mobile phase under isocratic conditions. Lactose, glucose, galactose, citric, lactic and formic acids were used to evaluate the following performance parameters: selectivity, linearity, precision, limit of detection (LOD), limit of quantification (LOQ), decision limits (CCα), detection capabilities (CCβ), recovery and robustness. For the method application a six goat milk yogurts were elaborated: natural, probiotic, prebiotic, symbiotic, cupuassu fruit pulp, and probiotic with cupuassu fruit pulp. The validated method presented an excellent selectivity with no significant matrix effect, and a broad linear study range with coefficients of determination higher than 0.995. The relative standard deviation was lower than 10% under repeatability and within-laboratory reproducibility conditions for the studied analytes. The LOD of the method was defined from 0.001 to 0.003 µg g(-1), and the LOQ from 0.003 to 0.013 µg g(-1). The CCα was ranged from 0.032 to 0.943 µg g(-1), and the CCβ from 0.053 to 1.604 µg g(-1). The obtained recovery values were from 78% to 119%. In addition, the method exhibited an appropriate robustness for all parameter evaluated. Base in our data, it was concluded that the performance parameters demonstrated total method adequacy for the detection and quantification of carbohydrates and organic acids in goat milk yogurts. The application of the method was successfully applied to monitoring different goat milk yogurts during fermentation.

No abstract

The aim of this work was to evaluate the physicochemical, instrumental color and texture, and sensory qualities of restructured tilapia steaks elaborated with small sized (noncommercial) 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.

The aim of this study was evaluated the physical and chemical changes in five types of alternative poultry meat keep at refrigerated conditions (4±1°C) during 18 days. For this purpose, breast meat of conventional, organic and free-range chicken, duck and quail were purchase from markets of Niteroi city (Rio de Janeiro, Brazil). Levels of pH, thiobarbituric acid reactive substances (TBARS) and biogenic amines (cadaverine and putrescine) were determinate. Statistic evaluation was performed using analyze of variance and Tukey test. The results showed a gradual and proportional increment of pH values (between 5.5 and 6.5) in all poultry meats during the storage time; an increment of TBARS values in the first days of storage, remaining stables to the end of experiment. A significant increment of putrescine values was observed after the sixth day remaining stable in conventional chicken and quail until the end of experiment while significant reduction was observed in the rest of poultry meats. Finally, only conventional and organic chicken and quail showed a gradual increment during storage time. In conclusion, significant biochemical changes was observed during the storage time being that pH, cadaverine and putrescine values could be parameters using like deterioration indicators for these products.Keywords: biogenic amines, chicken, duck, pH, quail, quality, TBARS. ResumoO objetivo do presente estudo foi avaliar as mudanças físico-químicas de cinco tipos de carnes de aves alternativas mantidas em condições de refrigeração (4±1°C) durante 18 dias. Para essa finalidade utilizou-se carne de peito de frangos convencional, caipira e orgânico, pato e codorna adquiridos de supermercados na cidade de Niterói (Rio de Janeiro, Brasil) e determinaramse os níveis de pH, substâncias reativas ao ácido tiobarbitúrico (SRATB) e aminas biogênicas (cadaverina e putrescina). Os resultados indicaram um incremento gradativo e proporcional dos valores de pH (entre 5,5 e 6,5) nas carnes de aves durante o tempo de estocagem; um aumento dos valores de SRATB nos primeiros dias de estocagem, mantendo-se invariáveis até o final do experimento. Em todas as aves foi observado um incremento significativo dos valores de putrescina após o sexto dia, mantendo-se estáveis no frango convencional e a codorna até o final do experimento, enquanto o resto das carnes diminuiu significativamente. Finalmente, foi observado um incremento gradativo apenas na codorna e nos frangos convencional e orgânico. Conclui-se que houve mudanças bioquímicas significativas nas carnes avaliadas durante o tempo de estocagem, sendo que os valores de pH, cadaverina e putrescina seriam parâmetros que podem ser utilizados como indicadores de deterioração destes produtos.Palavras-chave: aminas biogênicas, codorna, frango, pato, pH, qualidade, TBARS.