New tecnologies and pre-treatments: vacumm packed dried tomato. / Novas tecnologias e pre-tratamentos : tomate seco embalado a vacuo.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Osmotic concentration and other pre-treatments aim to improve product quality and optimise the drying process. Amongst these treatments one can mention the use of antioxidants to avoid excessive browning and maintain the nutritional characteristics. The incorporation of tomato concentrate at 18 to 36°Brix is not a method currently used in the manufacture of dried tomatoes, but could be a suitable method for quality improvement as well as increasing the yield on drying, considering that it would add up to six times the amount of soluble solids naturally present in the tomato. And the use of weak acids in the solutions used for osmotic drying or concentration represents a mild processing alternative, resulting in a product with appropriate sensory characteristics for immediate consumption. The use of a combination of additives together with various types of sugar (sucrose, fructose and glucose), especially acidifiers, in addition to their antioxidant action, help to increase the rate of osmosis. The general objectives of this research were: to evaluate and select new technology and pre-treatments aiming at improving final product quality and process yield and efficiency in the drying of tomato, and also to define and characterise the shelf life of the selected product. This research defined procedures, which allowed for an increase in efficiency and quality of a new product: vacuum-packed dried tomato with intermediate moisture content, safe for consumption. The use of invert sugar was shown to increase the efficiency of the osmotic dehydration of tomatoes, and temperatures above 45°C failed to provide the desired quality. Ascorbic acid showed losses during the first 30 minutes of pre-treatment, and the lycopene showed an increase in availability during the first 10 minutes, followed by a gradual decrease. The consumers determined that flavour was the most important factor for product approval and disapproved the application of triple concentrated tomato paste. The application of antioxidant (sodium metabisulphite and isoascorbic acid) allowed for greater retention of the lycopene and ascorbic acid. The consumers preferred products with the ?soluble solids/total acidity ratio? between 23.8 and 26.65. The salt concentration in the mixed syrup of sucrose and invert sugar was shown to be more efficient in the osmotic dehydration process between the values of 5.05 and 7.45%, with a citric acid concentration between 6.62 and 7.25%. The consumers chosen (sensory analysis) products obtained from pre-treatment: osmotic dehydration in 65°Brix syrups with the addition of 5.85% NaCl and 6.00% citric acid. The microbiological quality of the product, vacuum-packed dried tomato, was maintained during the periods evaluated of 180 days under refrigeration and 90 days at room temperature. The consumers considered values for the color parameter "L" above 38.37 as unacceptable, indicating this value as an instrumental colour limit (luminosity). The dried tomato adsorbed water in Relative Humidity to up 50%. The dried tomatoes osmotically dehydrated with invert sugar, salt and citric acid, provided values for water activity the 0.76 to 0.86. The syrup could be reused efficiently.

ASSUNTO(S)

drying shelf-life quality tomate vida de prateleira tomatoes qualidade secagem

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