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Advisor(s)
Abstract(s)
A extrusão é uma etapa de processamento de matéria-prima sólida que junta num único equipamento, denominado extrusora, várias operações unitárias e modificações físico-químicas. Ensaiou-se a produção de produtos extrudidos a partir de castanha de menor valor comercial numa extrusora de parafuso simples, fazendo variar parâmetros como a velocidade do parafuso. Avaliaram-se comparativamente as características dos produtos obtidos nas diversas combinações das farinhas de milho e de castanha, nas múltiplas condições ensaiadas, através das modificações funcionais, por microscopia ótica e pelo comportamento amilográfico, e das alterações a nível molecular, por cromatografia de filtração sobre gel. Foi também determinado o respetivo perfil instrumental de textura, assim como foi realizada uma avaliação sensorial dos produtos obtidos. Os resultados mostraram que o entumescimento dos grânulos de amido, a relação amilose/amilopectina, a massa molecular da amilopectina e o teor em lípidos da castanha são muito superiores às do milho, justificando as diferenças encontradas nas respectivas curvas de consistência e as alterações sofridas na extrusão. Os produtos com maior aceitabilidade foram os processados com baixos teores de humidade e temperaturas de extrusão intermédias.
The goal of this work was to study the technological possibilities of production of extrudates based on chestnut flour. An experimental plan of the extrusion process was drawn, considering three factors (X1, X2 and X3), with five levels for each factor (0; 1; 1,68179; -1,68179) and six replicates for the center point (0). In a single-screw extruder, were varied parameters such as the proportion of raw materials, corn (M) and chestnut flours (C) - 80M: 20C; 64M: 36C; 40M: 60C; 16M: 84C; 0M: 100C; the moisture content (%) of the blends to be processed - 12, 14, 16, 18 and 20; and the processing temperature (° C) - 150, 164, 185, 205 and 220. The characteristics of the extruded products obtained in the various combinations of maize and chestnut flour in the multiple conditions tested were evaluated by means of the functional modifications of starches, namely by the amilographic behaviour, and by instrumental evaluation of the texture, through parameters such as expansion rate, rupture force and rupture energy. On the basis of these results, a new plan was established, which basically differed from the first one by the substitution of variable X3 (% of nut incorporation) by screw speed (rpm) - 120, 155, 170, 185 and 220 - keeping the composition (100% chestnut) fixed. Chestnut flour has a relatively low gelatinization temperature (59 °C), and high consistency in its pastes. Its starch - which constitutes about 49% on a dry basis - has been found to have an amylose / amylopectin ratio of 0,75, which is higher than that of most cereals, such as maize tested (about 0,32). The major changes occurred in raw materials with low moisture content and processed with high extrusion temperatures. The amylographic behaviour of the various blends and the texture characteristics of the extruded products showed that chestnut flour has potential to be used as an ingredient in the formulation of foods by extrusion-cooking.
The goal of this work was to study the technological possibilities of production of extrudates based on chestnut flour. An experimental plan of the extrusion process was drawn, considering three factors (X1, X2 and X3), with five levels for each factor (0; 1; 1,68179; -1,68179) and six replicates for the center point (0). In a single-screw extruder, were varied parameters such as the proportion of raw materials, corn (M) and chestnut flours (C) - 80M: 20C; 64M: 36C; 40M: 60C; 16M: 84C; 0M: 100C; the moisture content (%) of the blends to be processed - 12, 14, 16, 18 and 20; and the processing temperature (° C) - 150, 164, 185, 205 and 220. The characteristics of the extruded products obtained in the various combinations of maize and chestnut flour in the multiple conditions tested were evaluated by means of the functional modifications of starches, namely by the amilographic behaviour, and by instrumental evaluation of the texture, through parameters such as expansion rate, rupture force and rupture energy. On the basis of these results, a new plan was established, which basically differed from the first one by the substitution of variable X3 (% of nut incorporation) by screw speed (rpm) - 120, 155, 170, 185 and 220 - keeping the composition (100% chestnut) fixed. Chestnut flour has a relatively low gelatinization temperature (59 °C), and high consistency in its pastes. Its starch - which constitutes about 49% on a dry basis - has been found to have an amylose / amylopectin ratio of 0,75, which is higher than that of most cereals, such as maize tested (about 0,32). The major changes occurred in raw materials with low moisture content and processed with high extrusion temperatures. The amylographic behaviour of the various blends and the texture characteristics of the extruded products showed that chestnut flour has potential to be used as an ingredient in the formulation of foods by extrusion-cooking.
Description
Keywords
Extrusão Castanha Amido Farinhas
Citation
Choupina, Altino; Lopes-da-Silva, M.F.; Santos, Luís Beirão-da-Costa, Luísa (2017). Valorização de produtos na produção de extrudidos. In Barbosa, José Carlos (Ed.) IX Congresso Ibérico de Agroengenharia: livro de resumos = IX Congreso Ibérico de Agroingeniería: libro de resúmenes. Bragança: Instituto Politécnico. ISBN 978-972-745-229-3
Publisher
Instituto Politécnico de Bragança