Marília Amorim Berbert de Molina

Desidratação por imersão-impregnação e secagem por convecção de goiaba

O objetivo deste trabalho foi avaliar as caracteristicas fisico-quimicas e sensoriais de goiabas in natura e submetidas a desidratacao por imersao-impregnacao e a secagem complementar por conveccao, alem de avaliar a estabilidade da cor das goiabas secadas apos 30, 60 e 90 dias de armazenamento sob refrigeracao. Amostras de goiaba foram imersas em solucoes de sacarose a 0,4 e 0,5 g mL-1, sacarose a 0,3 g mL-1 + sucralose a 0,2 g L-1, acucar invertido a 41% (p/p) e acucar invertido sem diluicao. Foram avaliados solidos soluveis totais, acidez titulavel, pH, cor, aroma, aparencia, sabor e textura. O teor de solidos soluveis totais das amostras aumentou linearmente em funcao do tempo de imersao, sem efeito significativo do tipo de acucar empregado no preparo da solucao. A preservacao do teor de acido citrico foi mais pronunciada em solucoes menos concentradas de sacarose. Amostras secadas nao submetidas a desidratacao osmotica exibiram maior alteracao de cor do que aquelas previamente desidratadas. Solucoes de sacarose sao mais eficazes na estabilidade da cor do que as de acucar invertido. As goiabas submetidas a desidratacao por imersao-impregnacao tiveram boa aceitacao sensorial, e aquelas secadas apenas por conveccao nao foram aceitas pelos provadores.

Secagem de fatias de abacaxi in natura e pré-desidratadas por imersão-impregnação: cinética e avaliação de modelos

The effect of glucose and invert sugar impregnation on the convective drying rate of pineapple and the suitability of nine mathematical models to describe the drying curves were investigated. Tests were conducted using fresh pineapple rings and samples which were pre-treated by osmotic dehydration in sucrose solutions (0.40, 0.44, and 0.47 g mL-1) and in invert sugar syrup. Osmotic pre-treatments were performed at 40 and 50 oC for 2 hours at 60 min-1. The convective drying was performed in a tray cabinet dryer using heated ambient air at 60 oC and 1.25 m.s-1. The adjustment levels of the models were based on the correlation coefficient, the root mean square error, mean absolute percentage error, and residual plot analysis. The highest rates of convective drying were obtained for the fresh samples. In the osmotically pre-treated fruits, with both temperatures, an increase in the solution concentration was followed by a decrease in the convective drying rate. The Wang and Singh model was considered the most adequate in describing the convective drying of pineapple rings.

Avaliação nutricional e sensorial de caqui cv Fuyu submetido à desidratação osmótica e secagem por convecção

A crescente preocupacao com a saude humana tem promovido o aumento da demanda pelo consumo de frutas, tanto in natura como processadas. Neste trabalho, foram realizadas as avaliacoes nutricional e sensorial de caqui Fuyu submetido a desidratacao osmotica e secagem por conveccao. Cilindros de caqui com diâmetro de 15 mm e altura de 40 mm foram imersos por 2 horas em solucao com concentracao de sacarose de 0,47 g.mL-1, a 40 oC, utilizando-se relacao fruta/xarope de 1:10 e grau de agitacao de 60 min-1. A reducao do teor de agua ate 17% b.u. foi realizada a 60 oC, empregando-se velocidade do ar de 1,25 m/s. Apos a secagem, foram realizadas as seguintes analises fisico-quimicas: acidez, pH, oBrix, carboidratos, proteinas, lipidios, vitamina C, cinzas, fibras insoluveis e analise sensorial. Os resultados mostraram incremento em todas as caracteristicas fisico-quimicas avaliadas para o caqui desidratado em comparacao ao caqui in natura. A analise sensorial evidenciou que o produto obteve elevado indice de aceitacao, correspondendo ao segundo e terceiro niveis da escala hedonica (gostei muito e gostei regularmente). A caracteristica que influenciou predominantemente a aceitacao do produto foi a textura (88%), seguida do sabor (84%). A aparencia foi o atributo que menos influenciou a aceitacao (80%).

Qualidade nutricional de goiabas submetidas aos processos de desidratação por imersão-impregnação e secagem complementar por convecção

During dewatering and impregnation soaking (DIS), transfer of water and of natural compounds from the product to the hypertonic solution occurs, however, few studies have been carried out to identify and quantify the losses of these compounds. Thus, this work reports on the losses of vitamin C and of the following minerals: Na, K, Ca, Mg, Zn and Mn, in red guavas submitted to the combined process of DIS (at 50 oC for 2 hours) and convective drying (at 60 oC and air velocity of 1.25 m/s, to a final moisture content of 20% w.b.). Studies were carried out employing two types of solutes: sucrose (in 0.4 and 0.5 g.mL-1 solutions) and liquid invert sugar (in a 41% w/w solution and as an undiluted syrup). Also, a test was performed using a solution comprised of 0.3 g.mL-1 sucrose and 0.2 g.L-1 sucralose. The control treatment consisted of drying guava solely in the convective drier. The effect of storage conditions on the stability of ascorbic acid was assessed after 60 days at 7 and 25 oC. Results indicated reductions in the range of 20 to 64% in the amounts of the minerals studied at the end of the DIS process, as compared to the amount found in fresh fruits, and negligible losses of vitamin C, except in the treatment with undiluted liquid invert sugar. Convective drying promoted losses of vitamin C in the range of 32 to 68%. The ranges of vitamin C loss in storage at 7 and 25 oC were 58 to 82% and 70 to 86%, respectively.

Desidratação por imersão-impregnação de abacaxi em soluções de sacarose e em xarope de açúcar invertido

This work consisted of evaluating the effect of the type of osmotic agent, degree of stirring, and temperature and concentration of the hypertonic solution on the kinetics of osmotic dehydration of sliced pineapple. The osmotic agents used here were sucrose in solutions with concentrations of 0.40, 0.44 and 0.47 g.mL-1, and undiluted inverted sugar syrup. Osmotic dehydration was carried out using a fruit to syrup weight ratio of 1:10, and employing two levels of temperature of the solutions, 40 and 50 °C, two shaking rates, 0 and 60 min-1, and a total immersion time of 2 hours. The results showed that immersion in undiluted inverted sugar caused a greater increase in the total soluble solids content in sliced fruit. The parameters characterizing the kinetics of osmotic dehydration showed higher values in the sliced fruit dehydrated in syrup at 40 to 50 °C under shaking.

Desidratação osmótica de frutos de duas cultivares de abacaxi em xarope de açúcar invertido

The objective of the present study was to investigate the kinetics of the osmotic dehydration of sliced pineapple of two cultivars, Perola and Smooth Cayenne, in undiluted inverted sugar syrup. Osmotic dehydration was carried out using a fruit to syrup weight ratio of 1:10, and employing two levels of temperature of the solutions (40 and 50 oC), two levels of agitation (zero and 60 min-1) for a total immersion time of 2 h. Results showed that the fruit to syrup ratio employed did not alter the total soluble solids content of the osmotic solution at the end of the dehydration process. A threefold increase in the total soluble solids content in pineapple slices was observed after dehydration, irrespective of cultivar and temperature of the solution. Highest values of mass reduction, water loss and solids gain were observed for fruit slices of cultivar Perola.

Mecanismos de transferência de massa na desidratação osmótica de goiaba em soluções de sacarose, sucralose e açúcar invertido

The present work aimed at investigating the effect of sucrose, sucralose and inverted sugar solutions on the kinetics of osmotic dehydration of guava pieces. The fruits were cut in twelfths and immersed in sucrose solutions at 0.5 and 0.4 g mL-1; of sucrose at 0.3 g mL-1 + sucralose at 0.2 g L-1 and in inverted sugar syrup for 2 h at 50 oC, under agitation of 60 min. The undiluted inverted sugar solution promoted the highest levels of water loss and weight reduction in osmo-dehydrated guava pieces. The best overall performance was achieved by immersing guava pieces in sucrose solutions at 0.4 g mL-1 which led to water loss and mass reduction of similar values attained with sucrose solutions at 0.5 g mL-1; whereas maintaining the same level of solids gain achieved with sucrose solutions at 0.3 g mL-1.