Analysis of Main Nutrients and Heavy Metal in Five Konjac

The contents of glucomannan, protein, fat, crude fiber and heavy metal was determined and analyzed by detection techniques of spectrophotometry, automatic Kjeldahl method, Soxhlet extraction and inductively coupled plasma mass spectrometry (ICP-MS) in the Amorphophallus albus, Amorphophallus nigrum, Amorphophallus yunnanensis Engl, Amorphophallus bulbifer and Tingsheng 1.The results showed that the glucomannan content in konjac was the most abundant, reaching about 60% of dry weight, the fat content was at least 0.06%~0.54%, the protein content was 4.16%~7.86%, and the crude fiber content was 3.10%~4.70%, the content of manganese (Mn) in heavy metal was 8.170~53.290 mg/kg, it was the highest up to 53.290 mg/kg in A.nigrum and the content of glucomannan, fat, protein, crude fiber and trace elements in different varieties of konjac was significantly different. On the whole, Amorphophallus albus had the highest nutritional value. This research can provide data support for the current development of under-forest specialty industries, the selection of konjac planting varieties, konjac market value positioning and intensive processing industries.