| Firstly, in order to determine the optimum accumulation technology of GABA in the fresh cabbages, the effects of cutting, low temperature stress and soaking on the changes of y-aminobutyric acid (GABA) content and other related indexes in outer and inner leaves of the fresh cabbages (B.oleracea var.capitata L.) were studied. Then based on this optimum condition, in order to obtain the adequate method of drying and to optimize its process parameters, the effects of hot-air drying, microwave drying and combined microwave-hot-air drying on the contents of water, GABA content, other components and the color of the dry cabbages were analyzed. Further, the effects of ultrafine grinding on the GABA content, particle size and sensory quality of dehydrated cabbage were investigated. Finally, the effects of packaging methods and storage temperature on cabbage powders’ quality were observed. The results were as follows:1. Effects of different stress treatments on GABA accumulation in cabbages were analyzed: The changes of y-aminobutyric acid (GABA) content and related indexes in outer and inner leaves of the fresh cabbages, cut into different sizes, stored at a low temperature of4℃and soaked into solution, were observed. The results showed that in both outer and inner leaves with the size of0.5cm×3cm, GABA content reached the maximum values of1.02mg·g-1and1.88mg·g-1, respectively, and the GABA content of inner leaves was significantly higher than that of outer leaves (P<0.05). Further, the outer and inner leaves with the size of0.5cm×3cm were stored at4℃for1.5h, GABA content in outer and inner leaves reached the maximum values of1.77mg·g-1and2.41mg·g-1, respectively, and the GABA content of the former was significantly lower than that of the latter (P<0.05). It was observed that after soaking for4h with the100μmol·L-1CaCl2solution, phosphate-citric acid buffer solution (pH=5.6) or10g·L-1sodium glutamate respectively, the GABA content in inner and outer leaves all reached the maximum. Meanwhile, the optimal accumulation condition was determined by orthogonal design analysis and the results showed that after soaking with100μmol·L-1CaCl2solution for2h, then10g·L-1sodium glutamate solution (pH=5.6) for4h, the GABA content was the best, increasing to2.48 mg/g.2. Based on the obtained optimum condition, changes of GABA and other components in cabbages dried by different drying methods were observed. The effects of hot-air drying, microwave drying and combined microwave-hot-air drying on the GABA content and other quality were compared. The results showed that with the increased drying temperature under the hot-air drying, GABA content first increased then decreased, L*value decreased, a*and b*value both increased, and the quality was better with the drying temperature of70℃. By the method of microwave drying, GABA content of the non-blanched cabbages was up to3.25mg/g when the microwave power increased to2.5W/g, but the color was poor. Combined the advantages of hot-air and microwave drying and determined by orthogonal design analysis and the regression equations, the optimal process parameters of combined microwave-hot-air drying were obtained:under the pre-microwave power of2.5W/g, the cabbage was dried to the moisture content of40%, then with the hot-air drying temperature of70℃, the quality of samples was the best.3. Based on two kinds of obtained optimum condition, the influence of ultrafine grinding on nutritional content of dried cabbage was investigated; samples were grounded under cryogenic conditions with ball mill for3,6,9and11h, respectively. The longer grinding time, the smaller particles size; with the prolonged grinding time, the angle of repose significantly increased, and GABA, glucosinolate, soluble protein, soluble sugar and water activity (aw) all increased, but values had no significant differences at their levels.4. In order to observe the storage stability of cabbage ultrafine powders, the effects of storage temperature, packaging mathods on GABA content and other quality of cabbage ultrafine powders were studied. The ultrafine powders (average size24.91μm) and the crude powders (average size233μm) were filled into the PE bag packaged with Nitrogen, vacuum and natural air, respectively,and stored at the temperatures of37℃and4℃, respectively. for2months. Results showed that the color (L*and a*values) and moisture content were significantly (P<0.05) affected by storage temperature, but insignificantly (P>0.05) affected by the packaging mathods To sum up, packed with PE and stored at4℃, cabbage ultrafine powders were better for retaining nutrient content, and ensuring the product quality. |
PDF Full Text Request