| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系 === 89 === Abstract
The effect of manufacturing method on the textural properties of preserved tomato was investigated. Tomatoes were blanched, and boiled (B) or soaked (S) in the sucrose (S), maltose (M) or invert sugar (I) and then dried at 60℃ until Aw＝0.76 ±0.02.
Results showed that, significant TPA profile variation was observed among all the products. The tomatoes soaked in maltose (SM) took longer time for drying and possessed firmer texture as compared with others. Puls NMR analysis showed that lower mobility of free water in this sample. Which means that lower free water mobility might lead to slower water evaporation and longer drying time, The boiled sample took shorter time for drying may come from the destruction of middle lamella and the high porosity. Bound water showed lower mobility in maltose sugared samples (both boiled or soaked) and samples soaked in sucrose. However, samples boiled in sucrose or invert sugar showed a higher content for bound water. This might be explained by the increased water-soluble pectin that was degraded from protopectin and the increase of invert sugar which was degraded from sucrose during boiling. The relationships between texture and pectic substances have been characterized. In this research, samples with firmer texture possess higher HWP fractions content.
After storage for sixty days, results showed that in SM, BM and SS samples, sugar crystallized and their water content decrease or keep steady while their water activity increase significantly. Their firmness also increased significantly (more 0.5 ㎏). SM samples took the shortest time to mold. The time of molding was found to be correlated to quantity of free water. The changes of water content and water activity might come from crystallization of sugars. The increase of firmness might be related to crystallization of sugars in addition to amount of stronger associated pectins.
|
|---|
