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Estudo da desidrata??o osm?tica de fatias de chuchu (Sechium edule, Sw.) / Study of osmotic dehydration of chayoteFerreira, J?natas de Aguiar 30 August 2005 (has links)
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Previous issue date: 2005-08-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior-CAPES / In this research, the drying kinetics and equilibrium conditions during osmotic
dehydration of chayote (Sechium edule, Sw.) were studied using 20, 30 and 40 % (w/v)
sucrose solutions. A thermostatic bath was built to allow the experimental evaluation of
osmotic dehydration kinetics and equilibrium moisture content determination. The
experiments were carried out at three different temperatures (30 ?C, 40 ?C and 50 ?C) in
order to evaluate the influence of temperature and sucrose concentration. Chayote fruits
were washed and submerged in sodium hypochloride solution for ten minutes, for
sanitization. Afterwards, the fruits were dried and cut into slices of about 0.5 cm
thickness. Then, the slices were put into hypertonic sucrose solutions during preestablished
time intervals. After osmotic dehydration, the solution was discarded and
the slices were softly dried with absorbent paper to remove surface moisture. The
moisture content was determined gravimetrically. Long time experiments up to 96 h
were performed to provide information about the equilibrium moisture content. An
specific equilibrium isotherm was selected by statistical methods. The correlation that
better described equilibrium moisture content behavior was the Smith sorption isotherm,
adapted to osmotic environment. The Overhults model was used to describe osmotic
dehydration kinetics and estimate the drying constants k and n. Based on the results
obtained in this research, it could be demonstrated that the equilibrium moisture content
is strongly influenced by sucrose concentration and that k is a parameter dependent on
the temperature and sucrose concentration, whereas n may be considered constant for
the given experimental setup. / Neste trabalho foi feito um estudo da desidrata??o osm?tica de fatias de chuchu em um
sistema que possibilitou a determina??o da umidade de equil?brio e dos coeficientes do
modelo de Overhults para descrever a cin?tica de desidrata??o osm?tica das fatias. O
procedimento experimental consistiu em lavar e escovar os frutos, para a remo??o de
impurezas da casca, fatiar o chuchu, em fatias de 5 mm de espessura, num fatiador
dom?stico de alimentos, submeter o material ? desidrata??o osm?tica em solu??o
hipert?nica de sacarose a 20,30 e 40%, por at? 96 horas, tomando amostras em per?odos
determinados para levantar a curva de desidrata??o do material e tamb?m determinar a
umidade de equil?brio das fatias de chuchu como uma fun??o da concentra??o inicial da
solu??o hipert?nica e da temperatura. Com base nos resultados obtidos foi poss?vel
determinar os par?metros do modelo de Overhults para as fatias de chuchu, bem como a
uma correla??o para a umidade de equil?brio do material e constatar que h? forte
influ?ncia da temperatura e da concentra??o sobre a cin?tica de desidrata??o osm?tica
do chuchu, que cerca de 50 % da umidade das amostras ? removida nas primeiras duas
horas de imers?o, que a umidade de equil?brio ? atingida em cerca de 48 horas de
imers?o e que o modelo de Overhults descreve satisfatoriamente as curvas de
desidrata??o osm?tica.
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Estudo da desidrata??o de tomates em peda?os com pr?-tratamento osm?ticoSouza, Josilma Silva de 07 June 2002 (has links)
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Previous issue date: 2002-06-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Vegetables drying plays an important role in the field of food dehydration, being a very old practice that was originated from sun drying items of food in order to preserve them to be consumed during the periods of scarcity. One of these vegetables is the tomato, that was originally grown in South America. Tomatoes are easily perishable after being picked up from the tree and this makes the process of tomato dehydration a challenge due to the high amount of water (95%) contained in them. The present research work was mainly intended to develop alternative processes for tomato conservation, by drying slices of skinned and unskinned tomatoes in the in natura form or in the osmotically pre-dehydrated form. Firstly, the best conditions of the osmotic pre-dehydration process were defined including temperature, immersion time and concentration of the osmotic solution, based on the results of water loss, solids gain and weigh reduction of the pre-dehydration tomatoes at different processing conditions. The osmotic solution used was made up of NaCl (5 and 10%) and sucrose (25 and 35%) at different combinations. For a fixed conditions of osmotic pre-dehydration, the drying tests of the pre-processed and in natura tomatoes were carried out in a stove with air circulation and a convective dryer with trays, at two levels of temperature. The sensorial analysis of the osmotically pre-treated and unskinned dehydrated tomatoes was carried out as well as a study on the their shelf-live. The results obtained showed that the drying of the tomatoes took place as a result of the internal control of the water transport, and did not show a constant rate, while two distinct periods of the decreasing phase were observed. The osmotic pre treatment substancially reduced the initial amount of humidity in the tomatoes, thus reducing the necessary time for the product to attain levels of intermediate humidity. The impermeability of the tomato skin was identified as well as the unfavorable influence of the pre-treatment on the unskinned tomatoes, whose solid gain brought about a decrease in the water activity with subsequent reduction of the drying rate. Despite the various simplifications carried out during the development of this study, the proposed diffusive model adjusted to the experimental data satisfactorily, thus making it possible to determine the effective coefficients of diffusion, whose results were consistent and compatible with those found in the current literature. Concerning the higher rates of evaporation and the lowest processing time, the best results were obtained in the drying of the unskinned, in natura tomatoes and of the skinned, pre-dehydrated tomatoes, at 60?C, both processed in the convective drier. The results of the sensorial analysis of the unskinned and pre-treated product did not prove to be satisfactory. Regarding the shelf-live of the tomatoes, for a period of 45 days, no physicochemical or microbiological alteration of the product was noted / A secagem de hortali?as ocupa uma posi??o muito representativa na ?rea de desidrata??o de alimentos, processo esse que teve in?cio com a secagem ao sol, tem a finalidade de preservar os excedentes das colheitas para serem consumidos nos per?odos de escassez. Dentre estas hortali?as se encontra o tomate, originado da Am?rica, que ap?s a colheita apresenta-se um fruto bastante perec?vel fazendo com que a sua desidrata??o seja um desafio, devido ao seu alto teor de ?gua (95% b.u.). Esse trabalho teve como principal objetivo encontrar formas alternativas de conserva??o do tomate, atrav?s da secagem de peda?os com e sem pele, na forma in natura ou pr?-desidratados osmoticamente. Inicialmente, foram definidas as melhores condi??es da pr?-desidrata??o osm?tica (temperatura, tempo de imers?o, concentra??o da solu??o osm?tica) baseados nos resultados de perda de umidade, ganho de s?lidos e redu??o de peso, dos tomates pr?-desidratados em diferentes condi??es de processamento. A solu??o osm?tica utilizada foi composta de NaCl (5 e 10%) e sacarose (25 e 35%) em diversas combina??es. Para uma condi??o fixa de desidrata??o osm?tica, realizou-se os ensaios de secagem dos tomates pr?-processados e in natura em estufa com circula??o de ar e em secador convectivo de bandejas, em dois n?veis de temperatura. Foi realizada a an?lise sensorial e o estudo de prateleira dos tomates desidratados sem pele e pr?-tratados osmoticamente. Os resultados obtidos mostraram que a secagem dos tomates ocorre sob condi??o de controle interno do transporte de umidade, n?o apresentando per?odo de taxa constante, e verificando-se dois per?odos distintos da fase decrescente. O pr?-tratamento osm?tico reduziu substancialmente a umidade inicial dos tomates, reduzindo o tempo necess?rio para o produto atingir n?veis de umidade intermedi?rios. Foi identificado o car?ter impermeabilizante da pele do tomate, e a influ?ncia desfavor?vel do pr?-tratamento nos tomates sem pele, cujo ganho de s?lidos provocou a diminui??o da atividade de ?gua com conseq?ente redu??o das taxas de secagem. Apesar das in?meras simplifica??es, o modelo difusional proposto ajustou-se de forma satisfat?ria aos dados experimentais, possibilitando a determina??o de coeficientes de difus?o efetivos, cujos resultados mostraram-se consistentes e compat?veis com os encontrados na literatura. Com rela??o as maiores taxas de evapora??o e ao menor tempo de processamento, os melhores resultados foram obtidos na secagem ? 60?C de tomates in natura sem pele e os tomates com pele pr?-desidratados, ambos processados no secador convectivo. Os resultados da an?lise sensorial do produto pr?-tratado e sem pele, n?o foram satisfat?rios. Com rela??o a vida de prateleira, durante um per?odo de 45 dias de armazenamento, n?o se verificou qualquer altera??o f?sico-qu?mica ou microbiol?gica do produto
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Estudo da desidrata??o osm?tica da cenoura (Daucus carota) em fatiasAra?jo, Paulyanna Medeiros de 30 April 2010 (has links)
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Previous issue date: 2010-04-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In the area of food dehydration, drying of vegetables has a very representative
position, it has the objective to preserve the surplus of crops and began with sun drying.
Among the vegetable is the carrot, which had its origin in Southeast Asia and in Brazil
is a vegetable cultivated enough. The principal objective of this works is to find
alternative ways for the conservation of carrot slices by osmotic dehydration with
additional drying in heart. Were initially defined the best conditions of pre-osmotic
dehydration (temperature, immersion time, type of osmotic solution) based on the
results of humidity loss, solid gain, weight reduction and efficiency ratio of predehydrated
carrots slices. The osmotic solutions used were composed by NaCl (10%)
and sucrose (50 ? Brix) named DO1 and sucrose (50 ? Brix) called DO2. Was made
experiment of pre-osmotic dehydration of carrot slices in two temperature levels, with
complementary drying in heart with air circulation at 70 ? C. Sensory analysis was
performed and the study of slices dehydration osmotically and the slices without
osmotic treatment. The best results were obtained with the solution DO1 60?C with
immersion time of 60 min. The drying of carrot slices presented period of constant rate
and decreasing rate. The osmotic pre-treatment reduced the initial humidity of carrot
slices, reducing the time to the product to reach the same humidity content. Fick's
model, considering the shrinkage, and the Page s model, adapt satisfactorily to
experimental datas, allowing the determination of effective diffusion coefficients,
consistent with the references. The results of sensory analysis of dry product, showed
greater acceptance of sliced carrots with osmotic treatment / Na ?rea de desidrata??o de alimentos, a secagem de hortali?as ocupa uma
posi??o muito representativa, tem a finalidade de preservar os excedentes das colheitas
e teve in?cio com a secagem ao sol. Dentre as hortali?as encontra-se a cenoura, que teve
sua origem no Sudoeste Asi?tico e no Brasil ? uma hortali?a bastante cultivada. Esse
trabalho teve como objetivo principal encontrar formas alternativas de conserva??o para
fatias de cenoura, atrav?s da desidrata??o osm?tica com secagem complementar em
estufa. Inicialmente foram definidas as melhores condi??es da pr?-desidrata??o
osm?tica (temperatura, tempo de imers?o, tipo de solu??o osm?tica) baseadas nos
resultados de perda de umidade, ganho de s?lidos, redu??o de peso e ?ndice de
efici?ncia das fatias de cenoura pr?-desidratadas. As solu??es osm?ticas utilizadas
foram compostas de NaCl (10%) e sacarose (50? Brix) denominada DO1, e sacarose
(50? Brix) denominada DO2. Realizaram-se os ensaios de pr?-desidrata??o osm?tica das
fatias de cenouras em dois n?veis de temperatura, com secagem complementar em estufa
com circula??o de ar a 70?C. Foi realizada an?lise sensorial e o estudo da reidrata??o
das fatias desidratadas osmoticamente e das fatias sem tratamento osm?tico. Os
melhores resultados foram obtidas com as cenouras desidratadas com a solu??o DO1 a
60?C com tempo de imers?o de 60 min. A secagem das fatias de cenoura apresentou
per?odo de taxa constante e de taxa decrescente. O pr?-tratamento osm?tico reduziu a
umidade inicial das fatias de cenoura, reduzindo o tempo para o produto atingir o
mesmo teor de umidade. O modelo de Fick, considerando o encolhimento, e o modelo
de Page, se ajustaram de forma satisfat?ria aos dados experimentais, possibilitando a
determina??o de coeficientes de difus?o efetivos, consistentes com a literatura. Os
resultados de an?lise sensorial do produto seco indicaram maior aceita??o das fatias de
cenouras com tratamento osm?tico
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Desidrata??o osm?tica de banana utilizando solu??es de fruto-oligossacar?deos e xarope de milho em diferentes temperaturas / Study banana osmotic dehydration using solutions containing fructo-oligosaccharides and corn syrup at different temperaturesLANDIM, Ana Paula Miguel 02 June 2016 (has links)
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Previous issue date: 2016-06-02 / CAPES / Banana is a perishable fruit, as it ripens fast and cannot be adequately preserved by the cold, resulting in large post-harvest losses. The application of preservation techniques, such as osmotic dehydration, reduces losses of the commodity in post-harvest stage, extend its shelf-life, while not severely affecting its nutritional values, and functional and sensorial properties, which makes it at processing alternative for the fruit. The aim of this study is to evaluate the kinetics of osmotic dehydration, as well as the quality of the osmotically dehydrated samples in terms of color, texture, and antioxidant capacity, using fructo-oligosaccharide, corn syrup and the mixture of both, under different temperatures. To determine the kinetics, the fruit, cut in cubes, was dehydrated in different solutions, under temperatures of 40, 50 and 60 ? C. The kinetics of water loss (WL) and solid gain (SG) were evalueted at 30, 60, 90, 120, 180, 240, 360, 720 to 1440 minutes. The analysis of variance was used to verify the effect of each solution and temperature on kinetics. The kinetic parameters were modeled based on the equations of Peleg, Page modified and Barbosa Junior et al. using non-linear regression. The time to reduce the dehydration rate or penetration to one third of its initial values (t(1/3)) and the process average time (t(average)) were obtained on the Barbosa Junior et al. model The quality of the samples was accessed at these two times, in different solutions under different temperatures. For such, the variation of the instrumental parameters of color, antioxidant capacity (FRAP, DPPH and total phenolic content), and texture (axial compression tests) of samples, in nature as well as processed, were verified. The WL was not affected significantly by the type of solute used, however, the temperature presented significant influence over these parameters (p < 0.05). The experimental data for the WL was adequately adjusted to the Peleg and Page modified models with coefficients of determination (R?) superior than 0.98, mean relative error (E) inferior than 6.5% in all treatments. The water loss content values varied from 15.75 to 28.79% at time t(1/3), while for the time t(averege) 15.75 to 30.27% between treatments. The process of osmotic dehydration had affect on the quality of the final product, showing significant differences between the fruits in natura and processed state, in terms of color, antioxidant capacity and texture of the samples. / A banana ? um fruto perec?vel, pois sofre r?pido amadurecimento, n?o pode ser devidamente conservado pelo frio, sendo acometido por grandes perdas p?s-colheita. A utiliza??o de t?cnicas de conserva??o, como a desidrata??o osm?tica, reduz as perdas p?s-colheita, estende a validade comercial, n?o acarreta em severas altera??es nas caracter?sticas nutricionais, funcionais e sensoriais e mostra-se como uma alternativa de processamento para este fruto. O objetivo desde trabalho foi avaliar a cin?tica da desidrata??o osm?tica, bem como, a qualidade das amostras desidratadas osmoticamente em termos de cor, textura e capacidade antioxidante, utilizando fruto-oligossacar?deo, xarope de milho e a mistura de ambos, em diferentes temperaturas. Para determina??o da cin?tica, a banana, cortada em cubos foi desidratada nas diferentes solu??es, sob as temperaturas de 40, 50 e 60 ?C. As Cin?ticas de Perda de ?gua (PA) e ganho de s?lidos (GS) foram avaliadas nos tempos 30, 60, 90, 120, 180, 240, 360, 720 e 1440 minutos. A an?lise de vari?ncia foi usada, a fim de verificar o efeito do tipo de soluto e da temperatura na cin?tica. Os par?metros cin?ticos foram modelados de acordo com a equa??o Peleg, Page modificado e Barbosa J?nior et al. utilizando regress?o n?o-linear. A partir do modelo de Barbosa J?nior et al., obteve-se o tempo para reduzir a taxa de desidrata??o ou impregan??o a um ter?o de seus valores iniciais (t(1/3)) e o tempo m?dio de processo (t(m?dio)). A qualidade das amostras foi avaliada nestes dois tempos, nos diferentes solutos e temperaturas. Para tal, foram verificadas a varia??o dos par?metros instrumentais de cor, a capacidade antioxidante (FRAP, DPPH e teor de fen?licos totais) e a textura (ensaios de compress?o axial) das amostras in natura e processadas. A PA n?o foi afetada significamente pelo tipo de soluto empregado, no entanto, a temperatura apresentou influ?ncia significativa neste par?metro (p < 0,05). Os dados experimentais para a PA se ajustaram adequadamente ao modelo de Peleg e Page modificado e obtiveram-se coeficientes de determina??o (R?) maiores do que 0,98, desvio relativos m?dios (E) inferiores a 6,5% em todos os tratamentos. O modelo do tempo de n-redu??o da taxa de desidrata??o se mostrou uma boa alternativa na defini??o do tempo de processamento das amostras submetidas ? desidrata??o osm?tica. Os valores de perda de ?gua variaram de 15,70 a 28,79% no tempo t(1/3), enquanto que para o tempo de t(m?dio) de 15,75 a 30,27% entre os tratamentos. O processo de desidrata??o osm?tica influenciou na qualidade final dos produtos, apresentando diferen?as significativas entre a fruta in natura e a processada para varia??o dos par?metros de cor, a capacidade antioxidante e a textura das amostras in natura e processadas.
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Estudo da reidrata??o do feij?o verde (Vigna unguiculata L. Walp) desidratado por micro-ondas com e sem pr?-tratamento osm?ticoQueiroga, Priscila Vanini Dantas de Medeiros 19 March 2012 (has links)
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Previous issue date: 2012-03-19 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The green bean has organoleptic and nutritional characteristics that make it an important food
source in tropical regions such as the Northeast of Brazil. It is a cheap source of protein and
important for nutrition of rural population contributing significantly in subsistence farming of
the families from Brazil s northeast. It is consumed in entire region and together with the dry
meat and other products composes the menu of typical restaurants, being characterized as an
important product for economy of Northeast. The green bean is consumed freshly harvested and
has short cycle, being characterized as a very perishable food, which hampers your market. The
drying method is an alternative to increase the lifetime and provide a reduction volume of this
product making easier your transportation and storage. However is necessary to search ways of
drying which keep the product quality not only from the nutritional standpoint but also
organoleptic. Some characteristics may change with the drying process such as the coloring, the
rehydration capacity and the grains cooking time. The decrease of drying time or of exposure of
the grains to high temperature minimizes the effects related with the product quality loss.
Among the techniques used to reduce the drying time and improve some characteristics of the
product, stands out the osmotic dehydration, widely used in combined processes such as the
pretreatment in drying food. Currently the use of the microwaves has been considered an
alternative for drying food. The microwave energy generates heat inside of materials processed
and the heating is practically instantaneous, resulting in shorter processing times and product
quality higher to that obtained by conventional methods. Considering the importance of the
green beans for the Northeast region, the wastefulness of production due to seasonality of the
crop and your high perishability, the proposal of this thesis is the study of drying grain by
microwaves with and without osmotic pretreatment, focusing on the search of conditions of
processes which favor the rehydration of the product preserving your organoleptic
characteristics. Based on the analysis of the results of osmotic dehydration and dielectric
properties was defined the operating condition to be used in pretreatment of the green bean, with
osmotic concentration in saline solution containing 12,5% of sodium chloride, at 40?C for 20
minutes. The drying of green bean by microwave was performed with and without osmotic
pretreatment on the optimized condition. The osmotic predehydration favored the additional
drying, reducing the process time. The rehydration of dehydrated green bean with and without
osmotic pretreatment was accomplished in different temperature conditions and immersion time
according to a factorial design 22, with 3 repetitions at the central point. According to results the
better condition was obtained with the osmotically pretreated bean and rehydrated at a
temperature of 60?C for 90 minutes. Sensory analysis was performed comparing the sample of
the green bean in natura and rehydrated in optimized conditions, with and without osmotic
pretreatment. All samples showed a good acceptance rate regarding the analyzed attributes
(appearance, texture, color, odor and taste), with all values above 70%. Is possible conclude that
the drying of green bean by microwave with osmotic pretreatment is feasible both in respect to
technical aspects and rehydration rates and sensory quality of the product / O feij?o verde apresenta caracter?sticas organol?pticas e nutricionais que fazem dele uma
importante fonte aliment?cia em regi?es de clima tropical como o Nordeste do Brasil. ? uma fonte de
prote?na barata e importante para a nutri??o da popula??o rural contribuindo significativamente na
agricultura de subsist?ncia das fam?lias nordestinas. ? consumido em toda a regi?o e comp?e junto
com a carne de sol e outros produtos o card?pio dos restaurantes t?picos, caracterizando-se assim como
um produto importante para a economia da Nordeste. O feij?o verde ? consumido rec?m-colhido e
apresenta ciclo curto, sendo caracterizado como um alimento de alta perecibilidade, o que dificulta a
sua comercializa??o. A secagem desse produto se caracteriza como uma alternativa para o aumento da
vida ?til deste alimento, al?m de proporcionar uma redu??o de volume facilitando seu manuseio no
transporte e armazenagem. Todavia necess?rio se faz buscar formas de secagem que preservem a
qualidade do produto n?o s? sobre o ponto de vista nutricional como organol?ptico. Dentre as
caracter?sticas que se alteram com o processo de secagem, destacam-se a colora??o, a capacidade de
reidrata??o e o tempo de cozimento dos gr?os. A diminui??o do tempo de secagem, ou de exposi??o
dos gr?os a elevadas temperaturas minimizam os efeitos relacionados com a perda de qualidade do
produto. .Dentre as t?cnicas empregadas para minimizar o tempo de secagem e melhorar algumas
caracter?sticas do produto, destaca-se a desidrata??o osm?tica, muito utilizada em processos
combinados como pr?-tratamento na secagem dos alimentos. Atualmente a utiliza??o do micro-ondas
tem sido apontada como uma alternativa para a secagem de alimentos. A energia de micro-ondas gera
calor no interior dos materiais processados e o aquecimento ? praticamente instant?neo, o que resulta
em tempos de processamento mais curtos e qualidade do produto superior ? obtida pelos m?todos
convencionais. Considerando a import?ncia do feij?o verde para a regi?o Nordeste, o desperd?cio da
produ??o devido a sazonalidade da safra e sua alta perecibilidade, foi proposto nesta tese o estudo da
secagem dos gr?os em micro-ondas com e sem pr?-tratamento osm?tico, tendo como foco principal a
busca das condi??es de processo que favore?am a reidrata??o do produto, com preserva??o de suas
caracter?sticas organol?pticas. A partir da an?lise dos resultados da desidrata??o osm?tica e
propriedades diel?tricas foi definida a condi??o operacional a ser utilizada no pr?-tratamento do feij?o
verde, com concentra??o osm?tica em solu??o salina contendo 12,5% de cloreto de s?dio, a 400C por
20 minutos. A secagem do feij?o verde por micro-ondas foi realizada sem e com pr?-tratamento
osm?tico na condi??o otimizada. A pr?-desidrata??o osm?tica favoreceu a secagem complementar,
reduzindo o tempo de processo. A reidrata??o do feij?o verde desidratado com e sem pr?-tratamento
osm?tico foi realizada em diferentes condi??es de temperatura e tempo de imers?o de acordo com um
planejamento fatorial 22, com 3 repeti??es no ponto central . De acordo com os resultados a melhor
condi??o, foi obtida com o feij?o pr?-tratado osmoticamente e reidratado a uma temperatura de 600C
por 90 minutos. Realizou-se a an?lise sensorial comparando-se as amostra de feij?o verde in natura e
reidratado nas condi??es otimizadas, com e sem pr?-tratamento osm?tico. Todas as amostras
apresentaram um bom ?ndice de aceita??o referente aos atributos analisados (apar?ncia, textura, cor,
odor e sabor), estando todos os valores acima de 70%. Conclui-se que a secagem do feij?o verde por
micro-ondas com pr?-tratamento osm?tico ? vi?vel, tanto em rela??o aos aspectos t?cnicos como aos
?ndices de reidrata??o e a qualidade sensorial do produto
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