Engenharia De Alimentos

Tomato polygalacturonase (PG) was extracted from ripe tomatoes and purified by cation exchange and gel filtration chromatography. Cation exchange chromatography yielded two peaks with PG activity: the first peak was identified as PG2 (the heat labile form) and the second one as PG1 (the heat stable form). Both PG2 and PG1 presented a molar mass of 42 kDa when analyzed by SDS-PAGE and an isoelectric point >9.3. Thermal inactivation of purified tomato PG2, at pH 4.4, in the temperature range from 53 to 63°C, followed first-order kinetics. Combined pressure-temperature inactivation of tomato PG2 was studied at 5-55°C/100-600MPa. Under all pressure-temperature conditions, PG2 inactivation followed first-order kinetics. Purified tomato PG1, although more thermostable than PG2, showed a pressure stability very similar to that of PG2. These results indicate that high-pressure processing is an efficient alternative to inactivate tomato PG without the need for applying high temperatures.

Originalmente brasileiro, o requeijão cremoso é um queijo fundido que apresenta elevado teor de gordura e, como produto embalado, deve apresentar informação nutricional a fim de promover a comunicação, ao consumidor, sobre o valor energético e os componentes que constituem o produto. Este trabalho objetivou avaliar as informações nutricionais apresentadas nos rótulos de marcas comerciais de requeijão cremoso e a confiabilidade das informações. Foram determinados o valor energético, carboidratos, proteínas, gorduras totais, gorduras saturadas, gorduras trans e extrato seco total, de sete marcas comerciais de requeijão cremoso. Calculou-se a variação dos resultados obtidos com as quantidades apresentadas nos rótulos dos produtos e comparou-se com o limite permitido no Padrão de Identidade e Qualidade (PIQ) do produto. No estudo, foram obtidas 49 respostas que resultaram das comparações entre os resultados obtidos por métodos analíticos e as informações dos rótulos ou limites permitidos por legislação. Desse total, dez respostas apresentaram variação fora dos 20% tolerados pela RDC 360/2003, podendo-se concluir que 20,4% das informações nutricionais dos rótulos das sete marcas comerciais de requeijão cremoso analisadas não estavam adequadas à legislação vigente. A partir das análises realizadas nas sete marcas comerciais de requeijão cremoso, pode-se definir que a composição da porção de 30 g do produto variou entre 68,5

Pectin methylesterase (PME) was extracted from bananas (cv Cavendish) and puri®ed by af®nity chromatography on a CNBr±Sepharose±PME inhibitor (PMEI) column. A single protein and PME activity peak was obtained. For banana PME, a biochemical characterization in terms of molar mass (MM), pI, and kinetic parameters was performed. In a second step, the thermal and high-pressure stability of the enzyme was studied. Isothermal inactivation of puri®ed banana PME could be described by a ®rst-order kinetic model in a temperature range of 65°to 72.5°C, whereas its isobaric± isothermal inactivation followed a fractional-conversion model. Banana PME was found to be more thermally stable compared with PMEs extracted from orange, tomato, and apple.

Pectinmethylesterase (PME) extracted from tomato fruit was purified by affinity chromatography. A single peak of PME activity was observed, presenting a molar mass of 33.6 kDa, an isoelectric point higher than 9.3, and an optimal temperature and pH for activity of 55°C and 8.0, respectively. The processing stability of purified tomato PME in buffer solution was compared to PME stability in tomato juice. In both media, thermal inactivation of PME presented first-order inactivation kinetics, PME in tomato juice being more heat-labile than purified PME. Regarding high-pressure treatment, tomato PME showed to be very pressure-resistant, revealing an outspoken antagonistic effect of temperature and pressure. To avoid cloud loss in tomato juice, a timetemperature treatment of 1 min at 76.5°C was calculated in order to have a residual PME activity of 1 × 10-4 U/mL.

Pectin methylesterase (PME) was extracted from strawberries (Fragaria ananassa, cv Elsanta) and purified by affinity chromatography on a CNBr-Sepharose 4B-PMEinhibitor column. A single protein and PME activity peak was obtained. A biochemical characterization in terms of molecular mass, pI, and kinetic parameters of strawberry PME was performed. In a second step, the thermal and high-pressure stability of the enzyme was studied. Isothermal and combined isothermal-isobaric inactivation of purified strawberry PME could be described by a fractional-conversion model. Purified strawberry PME is much more stable toward high-pressure treatments in comparison to those from oranges and bananas.

Pectin methylesterase (PME) from carrots (Daucus carrota L.) was extracted and purified by affinity chromatography on a CNBr-Sepharose 4B-PME inhibitor column. A single protein and PME activity peak was obtained. A biochemical characterization in terms of molar mass (MM), isoelectric points (pI), and kinetic parameters of carrot PME was performed. In a second step, the thermal and highpressure stability of the enzyme was studied. Isothermal and combined isothermal-isobaric inactivation of purified carrot PME could be described by a fractional-conversion model.

Tomato polygalacturonase (PG) was extracted from ripe tomatoes and purified by cation exchange and gel filtration chromatography. Cation exchange chromatography yielded two peaks with PG activity: the first peak was identified as PG2 (the heat labile form) and the second one as PG1 (the heat stable form). Both PG2 and PG1 presented a molar mass of 42 kDa when analyzed by SDS-PAGE and an isoelectric point >9.3. Thermal inactivation of purified tomato PG2, at pH 4.4, in the temperature range from 53 to 63°C, followed first-order kinetics. Combined pressure-temperature inactivation of tomato PG2 was studied at 5-55°C/100-600MPa. Under all pressure-temperature conditions, PG2 inactivation followed first-order kinetics. Purified tomato PG1, although more thermostable than PG2, showed a pressure stability very similar to that of PG2. These results indicate that high-pressure processing is an efficient alternative to inactivate tomato PG without the need for applying high temperatures.

Visa a elaboração de pós para bebida a partir de milho pipoca, observando-se aspectos de preparo da rnatéria ­prima e condições operacionais de processamento. Con­clui que as bebidas servidas com açúcar e leite obtive­ram melhor aceitação na análise sensorial.

No presente trabalho estudou-se a degradação da cor e do ácido ascórbico em kiwis processados por desidratação osmótica. Os frutos, submetidos a três pré-tratamentos químicos (cloreto de cálcio, ácido cítrico e ácido ascórbico) foram desidratados em solução de sacarose a 50°Brix por 150 minutos em banho termostático a 40°C sob agitação a 70 rpm. As reações de degradação dos parâmetros a* e da variação total de cor (ΔE*) foram melhor ajustadas ao modelo cinético de primeira ordem. O pré-tratamento com cloreto de cálcio ocasionou melhor manutenção da cor verde das fatias durante o processo. Os teores de vitamina C apresentaram redução média de 40% até o final da desidratação. Os tratamentos com ácido cítrico e ácido ascórbico proporcionaram a manutenção de níveis mais elevados de vitamina C nas fatias de kiwi.