Avaliação de parametros do processo de extrusão e do teor de farelo de trigo adicionado em caracteristicas de "snacks" expandidos de milho. / Evaluation of extrusion process parameters and of wheat bran content added on features of corn expanded snacks.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Expanded extruded snacks present great acceptance, especially among children and adolescents. Therefore, the development of fiber enriched snacks represents a mean for the introduction of dietary fiber into the diet. The ingestion of fibers has functional benefits; the reduction of the risk of several diseases, highlighting: colon cancer, diabetes and cardiovascular diseases, is attributed to them. In this study, corn flour and wheat bran were used as ingredients to produce extrudates. Corn was chosen because it is used in a great variety of products found in the Brazilian market; moreover it has a significant amount of starch (between 65 and 70%). Wheat bran was chosen because it is found in several products containing fiber in the market, emphasizing breads; and contains significant amounts of dietary fiber (above 45%). The experimental design used was based on the Response Surface Methodology (RSM) and the experiments were carried out according to a 23 complete factorial design with 17 trials, being 3 of them referent to the central point. The independent variables were: raw material moisture content, temperature in the 3rd zone of the extruder and quantity of wheat bran in the formulation. Coded values (-a = -1.682; -1; 0; +1; +a = 1.682) presented the following real values for the 3 independent variables: moisture (16.3%; 19%; 23%; 27%; 29.7%), temperature (104.8ºC; 115ºC; 130ºC; 145ºC; 155.2ºC) and wheat bran (0.0%; 5.0%; 12.3%; 19.6%; 24.6%). The following dependent variables (responses) were considered: expansion index (EI), water absorption index (WAI), water solubility index (WSI), hardness (instrumental) and color (L* - luminosity). Snacks were also evaluated with respect to their internal structure, using Scanning Electronic Microscopy (SEM). Besides this, after determining the optimal fiber enriched product, snacks without and with wheat bran were compared in terms of their technological (physical and functional) and sensory properties. Values found for the EI showed that an increase in the wheat bran content, temperature and moisture resulted in a reduction of the EI. The highest values for the WAI were obtained for the lowest percentages of wheat bran and highest values of moisture. Extrusion temperature had almost no influence on this variable. The WSI increased due to the increase of the temperature and of the percentage of wheat bran; and due to the decrease of moisture. In relation to hardness, the less hard extrudates were resultant of the lowest values of moisture, and of the highest values of temperature and highest contents of wheat bran. The lightest (highest values of L*) snacks were obtained at the highest processing temperatures and with the highest values of moisture. Intermediate values of wheat bran produced snacks with the lowest L* values. Analyses using SEM showed that high moisture contents provided snacks with a dense structure and poor cell formation; high temperatures contributed to the weakening of the structures of the extrudates; and high wheat bran contents lead to the formation of a great number of incomplete cells with thin walls, that resulted in a fragile structure. Comparing snacks without and with wheat bran (control and optimum, respectively), produced under the same conditions of moisture and temperature, it was verified that the snacks did not differ significantly with respect to WAI, WSI and L* value, whereas with respect to the EI and hardness, they differed. In the sensory analysis, the attributes evaluated in an acceptance test were color, appearance, texture, taste and global acceptance. Snacks differed only in the acceptance of color and appearance. With respect to purchase intention, the control was best accepted. Although the snack without wheat bran have presented higher acceptation by the consumers, the snack with wheat bran shows a great potential of consumption, specially being a functional product, representing an alternative to increase the ingestion of dietary fiber. The snack considered as optimum in this study has a higher percentage of wheat bran (8.7% wet basis) than that required by the Brazilian legislation (6.0 % wet basis) to permit the use of a "high fiber content" claim.

ASSUNTO(S)

farelo de trigo snacks functional properties mthodology extrusão superficie de resposta - metodologia wheat bran propriedades funcionais extrusion snacks response surface

ACESSO AO ARTIGO

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