Autor(es):
Guiné, Raquel 
; Barroca, Maria João
Data: 2010
Identificador Persistente: http://hdl.handle.net/10400.19/1276
Origem: Repositório Científico do Instituto Politécnico de Viseu
Assunto(s): Texture; pumpkin; Pepper
Descrição
Pumpkin and bell pepper are very popular in Portuguese cuisine; however, their processed form is scarce in the market. Therefore, the drying, which is one of the oldest methods for preservation of foods, may represent a possible method to commercialize these vegetables. The most popular drying process uses convection though hot air, but the high temperatures can change the composition and nutritional value as well as the organoleptic quality of the products. Despite the high costs and time consuming of freeze drying, this process generates minor changes in colour, flavor, texture, and chemical composition [1]. Apart from the perceived primary characteristics, texture and flavor play also an important role on the acceptability of foods by the consumers. Hence, it is crucial to determine and control the texture of the processed foods.
The present work aims to study the effect of freeze-drying and air drying at different temperatures on the texture of pumpkin and green pepper. The texture attributes (hardness, adhesiveness, springiness, cohesiveness, and chewiness) were estimated after measurements made with a texturometer. Measurements to the fresh green pepper were done on both sides of the pepper tissue, that is from the skin (external) and the flesh (internal) sides. Rupture of the skin from the flesh side required a lower force (10.9 N) when compared with the same action from the skin side (13.8 N).
The fresh pumpkin was peeled and texture profile analysis was carried out on cylindrical samples removed at 1, 3 and 4 cm of the skin and on axial and radial directions. At each distance of the skin the results show small differences between both directions. The medium values of hardness for fresh pumpkin were 12.4, 20.0 and 32.6 at 4, 3 and 1 cm of the skin, respectively.
Generally, the air convection of green pepper at 30 ºC and 70 ºC has a small effect on cohesiveness and springiness but their effect was very pronnonced on hardness (Figure 1). This parameter can be related to the force performed by mastication that takes part during eating. A similar effect was observed in the chewiness. The firmess (hardness) of the green pepper was also very sensitive to freeze drying.
As for the pumpkin, both drying processes – convective and freeze drying – have substantialy influenced its firmeness.
