RESUMO
The aim of this research was to determine the physicochemical properties, microbial counts and aflatoxin M1 (AFM1) levels of thermoultrasonicated, pasteurized and untreated milk (control) at days 1, 7 and 14 of storage. Thermoultrasound treatment was performed at a rate of 20â¯kHz for 10 or 15â¯min and 95% amplitude on homogenized and non-homogenized milk samples. Results showed that most physicochemical parameters were within the Mexican norms established for milk. Ultrasound treatment for 15â¯min reduced solids precipitation (pâ¯<â¯0.05) in unhomogenized milk during storage as compared to the pasteurized milk. All samples complied with aerobic mesophilic counts limits set by the Mexican norm except the control and the homogenized milk sample which was thermoultrasonicated for 10â¯min. Enterobacteriaceae counts of pasteurized and 15â¯min-thermoultrasound homogenized milks complied with the norm. The lowest levels of AFM1 were found in the 10â¯min-thermoultrasound unhomogenized milk (0.15⯱â¯0.05â¯pgâ¯AFMâ 1E/mL) one day after storage. Thermoultrasound did not affect the color of samples but homogenized milk treated for 10â¯min exhibited less total color difference. A high phenolic content was found in thermoultrasound and pasteurized milks on day 1. Thermoultrasound could be an alternative to milk pasteurization that preserves the physicochemical and microbiological quality of milk while reducing AFM1 levels.
Assuntos
Aflatoxina M1/análise , Enterobacteriaceae/isolamento & purificação , Microbiologia de Alimentos , Armazenamento de Alimentos , Leite/química , Leite/microbiologia , Pasteurização/métodos , Sonicação/métodos , Animais , Antioxidantes/farmacologia , Bovinos , Contagem de Colônia Microbiana , Cor , Sequestradores de Radicais Livres/farmacologia , México , Fenóis/análiseRESUMO
The purpose of this research was to optimize the thermoultrasound conditions for blackberry juice using the response surface methodology and considering juice quality parameters and antioxidant capacity. With the exception of microbial growth, the response variables showed high correlation coefficients with the mathematical model (R2adj>0.91). Thermoultrasound treatment inactivated all the evaluated microorganisms, and at the optimum conditions (50±1°C at 17±1min) it increased enzyme inactivation and antioxidant activity in comparison to pasteurized juice. The results demonstrated that thermoultrasound can be an alternative to pasteurization for the production of safe and high-quality juices with the added value of higher concentration of bioactive compounds and antioxidant capacity.
Assuntos
Antioxidantes/química , Sucos de Frutas e Vegetais , Rubus/química , Rubus/enzimologia , Ondas Ultrassônicas , Antocianinas/análise , Ácido Ascórbico/análise , Hidrolases de Éster Carboxílico/metabolismo , Catecol Oxidase/metabolismo , Ativação Enzimática , Sucos de Frutas e Vegetais/microbiologia , Concentração de Íons de Hidrogênio , Viabilidade Microbiana , Fenóis/análise , Rubus/microbiologia , Solubilidade , TemperaturaRESUMO
Blackberry (Rubus fruticosus spp.) fruit has high antioxidant activity due to its significant content of anthocyanins and antioxidant compounds. Among emerging technologies for food preservation, thermoultrasound is a technique that reduces microbial loads and releases compounds with antioxidant properties. The objective of this study was to determine the antioxidant content and fatty acid profile of blackberry juice subjected to thermoultrasound treatment in comparison to pasteurized juice. Blackberry juice and n-hexane extracts from a control (untreated juice), pasteurized, and thermoultrasonicated samples were evaluated for antioxidant activity, fatty acid profile, and antioxidant content. The juice treated with thermoultrasound exhibited significantly (p < 0.05) higher levels of total phenols (1011 mg GAE/L), anthocyanins (118 mg Cy-3-GlE/L); antioxidant activity by ABTS (44 mg VCEAC/L) and DPPH (2665 µmol TE/L) in comparison to the control and pasteurized samples. Oil extract from thermoultrasound juice also had the highest antioxidant activity (177.5 mg VCEAC/L and 1802.6 µmol TE/L). The fatty acid profile of the n-hexane extracts showed the presence of myristic, linolenic, stearic, oleic, and linoleic acids and was not affected by the treatments except for stearic acid, whose amount was particularly higher in the control. Our results demonstrated that thermoultrasound can be an alternative technology to pasteurization that maintains and releases antioxidant compounds and preserves the fatty acids of fruit juice.
Assuntos
Antioxidantes/química , Ácidos Graxos/análise , Sucos de Frutas e Vegetais/análise , Frutas/química , Pasteurização , Rubus/química , Ondas Ultrassônicas , Antocianinas/química , Antioxidantes/análise , Extratos Vegetais/químicaRESUMO
The objective of this study was to evaluate changes in color, betalain content, browning index, viscosity, physical stability, microbiological growth, antioxidant content and antioxidant activity of purple cactus pear juice during storage after thermoultrasonication at 80% amplitude level for 15 and 25 min in comparison with pasteurized juice. Thermoultrasound treatment for 25 min increased color stability and viscosity compared to treatment for 15 min (6.83 and 6.72 MPa, respectively), but this last parameter was significantly lower (p<0.05) compared to the control and pasteurized juices (22.47 and 26.32 MPa, respectively). Experimental treatment reduced significantly (p<0.05) sediment solids in juices. Total plate counts decreased from the first day of storage exhibiting values of 1.38 and 1.43 logCFU/mL, for 15 and 25 min treatment, respectively. Compared to the control, both treatments reduced enterobacteria counts (1.54 logCFU/mL), and compared to pasteurized juice decreased pectinmethylesterase activity (3.76 and 3.82 UPE/mL), maintained high values of ascorbic acid (252.05 and 257.18 mg AA/L) and antioxidant activity (by ABTS: 124.8 and 115.6 mg VCEAC/100 mL; and DPPH: 3114.2 and 2757.1 µmol TE/L). During storage thermoultrasonicated juices had a minimum increase in pectinmethylesterase activity (from day 14), and exhibited similar total plate counts to pasteurized juice. An increase of phenolic content was observed after 14 days of storage, particularly for treatment at 80%, 25 min, and an increase in antioxidant activity (ABTS, DPPH) by the end of storage.