Estudo da desidrata??o de tomates em peda?os com pr?-tratamento osm?tico

• Main Author: Souza, Josilma Silva de
• Other Authors: CPF:07538596453
• Format: Others
• Language: Portuguese
• Published: Universidade Federal do Rio Grande do Norte 2014
• Subjects: Tomates; Conserva??o; Desidrata??o osm?tica; Secagem; Difus?o; Tomatoes; Conservation; Osmotic dehydration; Drying; Diffusion.; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA
• Online Access: http://repositorio.ufrn.br:8080/jspui/handle/123456789/15777

Made available in DSpace on 2014-12-17T15:01:20Z (GMT). No. of bitstreams: 1 JosilmaSS.pdf: 490115 bytes, checksum: b796ab795af867ca3ee2bfaee9a69f80 (MD5) 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