Impacts of freeze–drying operation on the storage properties, commercial quality, and bioactive compounds of pickled cabbage
| Autor: | Chu-Mei Huang, 黃祝眉 |
|---|---|
| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 Chinese cabbage is rich in natural antioxidative phenolic compounds, which are contributed to the regulation of individual’s physiological functions. Pickled cabbage, a preservable fermentative product of Chinese cabbage, is yet easy to spoil and deteriorate by the contamination of microorganisms and the reaction of enzymes. The size and weight are the considerable factors for product transportation. Therefore, a suitable processing technology to prolong the time for storage, maintain the quality and antioxidant, and increase the convenience for transportation of pickled cabbage is an important topic for the food processing. Freeze-drying is a processing technology that less destroying the texture and structure of food to reduce the proliferation of microorganisms and retain more natural bioactives. The study was to investigate the impact of freeze-drying on the quality and antioxidative activity of pickled cabbage. The fresh cabbage was soaked in 4% saline and fermented in oven at 25 ° C for 21 days. Then, the fermented pickled cabbage was used to freeze-drying. The quality indexes (include hardness, pH, titratable acidity, and color) and antioxidative activity (include antioxidant activity, total polyphenols and total flavonoids content) of pickled cabbage were measured before and after freeze-drying. The results showed that the hardness of freeze-drying product after rehydration was decreased, but it can be improved by adding 0.5% CaCl2. The rehydration rate was 84.83% after freeze-drying product soaked for 120 min. There is no significant differences in pH (before: 3.10; after 3.32), titratable acidity (before: 0.78 %; after: 0.63 %) and color (both leaning yellow color) between before and after drying product. The TEAC antioxidant activity of product before and after drying was 239 and 217 mM TE, respectively; and the total flavonoids was 15 and 12 mg/ml and total polyphenols was 83 and 70 mg/ml. After 180 days of storage, the rehydration rate of freeze-drying product was 80.24% for 120 min soaking. The pH value, titratable acidity, color, TEAC value, total flavonoids, and total polyphenols of the 180-days stored freeze-dried product were 3.66, 0.53 %, yellowish, 202 mM TE, 13 mg/ml, and 61 mg/ml, respectively. These values showed insignificant differences with the product before freeze-drying. In conclusion, the addition of CaCl2 and freezing-drying should be effective methods to maintain quality and active ingredients of pickled cabbage after 180 days storage. Freeze-drying technology might be widely applied to the preservation of various pickled food. Because of the size and weight reductions, the freeze-dried products should be convenient for Transportation. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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