The process of mechanized production of dried konjac: fresh konjac bulbs → dig out the main buds → clean and peel → slice (slices, strips) → color protection → drying → inspection → packaging → finished product.
The following points should be noted in production:
(1) Remove the bud nests
At present, this process has not been mechanized and needs to be dug out manually. If the skin and buds of the bud nest are not dug cleanly, the fine powder will have black spots.
(2) Cleaning and peeling
If there is sediment and other debris on the surface of the bulb, it should be cleaned. The surface of konjac is periderm, which does not contain glucomannan and should be removed. The traditional method is to use manual scraping and manual cleaning, which is inefficient and labor-intensive. Nowadays, mechanized cleaning and peeling are adopted, which has high production efficiency. However, due to the unplanned shape of fresh taro bulbs, the protruding parts are often over-peeled and the recessed parts are not peeled enough. In addition, the water rinsing time is long during the rolling process. Part of the glucomannan dissolves, and the loss during cleaning and peeling is sometimes as high as 15% or more. Therefore, a suitable machine model should be selected, reasonable mechanical working parameters should be determined, or mechanical cleaning should be combined with manual cleaning to reduce losses and improve the quality of cleaning and peeling.
(3) Slices (or strips)
After cleaning and peeling, fresh taro should be cut into uniformly sized slices or strips in time for drying. One specification is cut into 2.5 cm wide and 3 to 4 mm thick strips, and the other specification is cut into 5 to 10 mm thick slices.
(4) Color protection
Corms can easily change color after peeling and slicing, so color protection should be carried out immediately after slicing. The color protection of konjac is mainly carried out by high-temperature passivation enzyme and fumigated sulfur dioxide. When fumigating sulfur dioxide, pay attention to the control of the amount. It is better to use the least sulfur dioxide to achieve color protection.
(5) Drying
At present, mesh bag type, vibrating fluidized bed or vibrating fluidized bed combined with mesh bag type are the main drying methods, and high-temperature fumigation is used in the drying process. There are two stages: sulfur fixation and low temperature drying. Generally, the hot air temperature in the high-temperature section is 110~130℃, the temperature in the low-temperature section is 50~70℃, and the mesh bag outlet material temperature is 40~50℃. The general trend of temperature is from high to low, and sulfur fumigation has also been changed from full-process sulfur fumigation in the past to staged sulfur fumigation in the early stage. The drying process mainly requires comprehensive coordination between boiler workers, technicians and production teams to obtain high-quality dried konjac that is white in color and dry in texture.
(6) Quality inspection
The moisture content of taro chips can be measured after weighing, crushing and drying. It can also be judged based on experience. Generally, a weight or hammer is used. Smash it, if it is crushed, it will be dry, otherwise it will have high moisture content. The sample comparison method can also be used to compare with samples with known accurate moisture content. The color can be judged by the senses, and graded based on the burnt and black heart rate of the dried taro slices and the degree of cleanliness. In actual production, inspectors mainly use moisture content and special grade product rate as the main basis for grading.
(7) Packaging
In order to prevent moisture and contamination, the dried taro chips that have been inspected should generally be packed in moisture-proof packaging. In actual production, most manufacturers process the raw materials into konjac powder as soon as possible to facilitate moisture-proof packaging.