Studies On The Technoglogy Of Curing White Radish And The Relationship Between Yellowing And Brittleness

Pickled radish is popular among consumers with its unique flavor and taste, brittleness as an important indicator of pickled radish directly impact the commodity and palatability of products. It had been a key problem during the radish pickling production that the brittleness would decrease while the color was yellowing.In this study, selecting white radish as experimental materials, the mechanism and changing law of the radish brittleness and yellowing during the curing process were studied; the brittleness and yellowing and sensory evaluation of white radish effected by curing condition were analysed; at last, the mechanism and changing law of the radish brittleness and yellowing effected by the low-temperature blanching and adding Ca2+ concentration on the pickled radish were studied. The main results are as follows:1.The brittleness of the sweet variety decreased more rapidly than spicy flavor variety in the curing, the yellowing was also more sciously; the crispness and the degree of yellowing was significantly difference between after-sun pickled radish and the fresh pickled radish; The varieties of spicy flavor that is more easily yellowing, and the brittleness decreased more rapidly in the after-sun curing than the fresh.2. The correlation was analyzed between the color, brittleness and water content cellulose content, pectin content, water soluble pectin, pectinase and celluase activities in the spicy flavor variety during after-sun curing process. The results showed that the brittleness of pickled radish had significant positive correlation with pectin content, cellulose content and pectinase activity (r=0.779,0.678 and 0.717, respectively), and had not significant correlation with water content, water-soluble pectin content and cellulase activity, the factor of pickled radish on the brittleness follow the order:pectin content> pectinase> cellulose content >water-soluble pectin>cellulose> water content. The brittleness of pickled radish had positive correlation with color,but the correlation was not significant.3. During the curing process of fresh radish, the cell wall appeared wavy bending, cell space expanded, the vacuole size was smaller and the color of cell cellulose stain gradually faded, the crispness of pickled radish decreased. During the curing process of after-sun radish, the cell wall is not only irregular folds, also the cell structural damaged, the brittleness of pickled radish decreased more quickly.The shape of cell wall,cellulose content, volume of vacuole and the space of cells are closely related with the brittleness of pickled radish.4. Different conditions in the curing process were used to study the yellowing condition and the changes of brittleness. The results showed that the degree of water lossing, salinity and the temperature of preserved environment all effected on the brittleness and the speed of yellowing. Meanwhile,pectin methylesterse and the content of CaCl2 solution have comparatively great influence on brittleness, but not found the effects on the yellowing speed. when the curing condition was drying radish to 40% of fresh weight, salinity 5%, adding 0.20% CaCl2 solution and 0.8mL/100 mL H2O pectinesterase, normal temperature (18℃), the brittleness can better maintained and the yellowing speed was inhibited to some extent.5. Low-temperature blanching coucld improve the activity of pectin methylesterase activity, promote the formation of pectin into pectin acid and calcium ion binding fast, increase the content of of pectin calcium, thereby increasing the brittleness of radish. Inhibition of low-temperature blanching also played a role in the yellowing process of salted radish. The results of orthogonal experiment shows that, the optimum conditions of low-temperature blanching were:add 0.2% CaCl2 solution to the blanching liquid, at the temperature of 55℃for 20min before curing, then can be well maintained its quality.