Study On The Key Production Technology Of Purple Sweet Potato Granules

Purple sweet potato as a new endemic species of sweet potato, is an unusual sweet potato with consumption, medicinal and health effects in human body, it contains not only the nutritional contents of the regular sweet potato, but also numerous anthocyanins. In recent years, Purple sweet potato, because of its special quality, is popular in domestic and foreign markets, and its developmental prospects are very bright.The purple sweet potato granules are processed by purple sweet potato, all its components in fresh sweet potatoes have a few loss during the processing, and after rehydration, it has the same color, taste and flavor as the fresh ones. As an excellent food raw materials or additives, it can be used in numbers of food areas. Not only can it satisfy the people's needs on green, organic, nutrition, and health food, it also provides a new direction for the deep processing of purple sweet potato and purple sweet potato granules.This paper investigated the optimum conditions of preparing purple sweet potato granules by three different processing methods, and analyzed the differences between the quality of purple sweet potato granules which are prepared by such three different processing. What's more, it also discusses the application and impact of purple sweet potato granules in bread and steamed bread. This study includes the following components:1. The optimum conditions of preparing purple sweet potato granules by hot air processing: considering the purple sweet potato chips'crushing force during cooking, the purple sweet potato granules'iodine blue value, L* and a* for color as indexes, we investigated the effects of factors, including cooking time, calcium concentration, emulsifier level and drying temperature, on purple sweet potato granules'quality, the optimum processing of preparing purple sweet potato granules by hot air processing was obtained as follows: Cutting the washed tuber(southern purple sweet potato 008) into thin slices of 10 - 15mm, 12 minutes of cooing time, adding 50μg/mg calcium concentration (as the potato tuber's mass ratio) and 0.4% emulsifier (as the potato tuber's mass percentage), then extruding into uniform mashed potatoes, air dried at 55℃temperature, until the materials'moisture content is between 6% to 9%, taking it out and crushing, and through the 80 mesh sieve, thus the prepared purple potato granules have the minimum iodine blue value and the optimum color.2. The optimum conditions of preparing purple sweet potato granules by microwave processing: considering the composite score of the purple sweet potato granules'iodine blue value, L* and a* as the indexes, we investigated the effects of microwave's dry power on purple sweet potato granules'quality, the optimum processing of preparing purple sweet potato granules by microwave processing was obtained as follows: Cutting the washed tuber (southern purple sweet potato 008) into thin slices about 10 to 15mm, with 12 minutes cooking time, adding 0.4% emulsifier, then extruding into uniform mashed potatoes, microwave dried at 700 watt, until the materials'moisture content is between 6% to 9%, moving it out and crushing, and through the 80 mesh sieve, thus the prepared purple potato granules have the minimum iodine blue value and the optimum color.3. The optimum conditions of preparing purple sweet potato granules by freeze processing: considering the composite score of the purple sweet potato granules'iodine blue value, L* and a* for the indexes, the optimum processing of preparing purple sweet potato granules by freeze processing was obtained as follows: Cutting the washed tuber (southern purple sweet potato 008) into thin slices about 10 to 15mm, with 12 minutes cooking time, adding 0.4% emulsifier, then extruding into uniform mashed potatoes, freeze dried it until the materials'moisture content is between 6% to 9%, taking it out and crushing, and through the 80 mesh sieve, thus the prepared purple potato granules have the minimum iodine blue value and the optimum color.4. Comparing the quality of the purple sweet potato granules which are prepared by three different processing: measuring the purple sweet potato granules'indexes, such as moisture, yield, iodine blue value, color value, viscosity, absorbent and its freeze-thaw and so on, to analyze the quality of the purple sweet potato granules prepared following the above processing. The results showed that the granules treated by freeze processing have the best quality, then is the hot air processing, and the microwave processing makes the granules the poorest quality among the three different processing.5. The impact of the purple sweet potato granules'adding on the bread and steamed bread's quality: considering the texture properties such as hardness, gumminess, chewiness, springiness, cohesiveness and resilience, and the color value as the indexes, to analyze the impact of the bread and steamed bread's quality made by the purple sweet potato granules'added. The result is, while adding 4% purple sweet potato granules, the bread has the best quality and size, color and texture date; the steamed bread, made with 6% purple sweet potato granules, has the largest size, refreshing and non-stick teeth, a good recovery, contains the purple sweet potato's special color and fragrance, and the wheat's aroma, what's more, it has a better color and texture data.