Objective  Effect of drying technology on the nutritional quality of Tremella fuciformis Berk was studied.

  Method  The national standards on the nutritional quality of edible fungi, such as contents of total sugar, reducing sugar, protein, and amino acids, were the indices used to evaluate 4 drying technologies in producing the dehydrated product. The FAO/WHO indexing system was applied to gage the protein nutrition. Dehydration of T. fuciformis employed either spent culture substrate for fuel in a factory oven (M1), spent culture substrate and wood chips for fuel in a factory oven (M2), spent culture substrate for fuel in a workshop oven (M3), or an industrial electric oven (M4).

  Results  Water-soaking of the fungi prior to dehydration showed no significant effect on the contents of protein, sugar, amino acids, and sulfur dioxide in the dried product (P＞0.05). However, the various drying methods resulted in quality differentiations among them. The contents of total sugar and reducing sugar in the dried T. fuciformis prepared under M2 and M3 were significantly higher than those under M4 (P＜0.05). The amino acid contents of the products made by different technologies did not differ significantly (P＞0.05). The nutritional grading based on amino acids ranked the dried mushrooms from those made by M1 at a score of 80.52, to M4 of 79.55, M3 of 79.15, and M2 of 77.80. All dried fungi products had a well-balance nutritional composition with lysine being the top restricted amino acid.

  Conclusion  The total sugar and amino acids in the dehydrated T. fuciformis were not affected by the pre-soaking but significantly by the drying process. Either drying by using spent culture substrate and wood chips for fuel in a factory oven (M2) or by using spent culture substrate for fuel in a workshop oven (M3) retained the nutrients more effectively than other methods. Incidentally, there was no sulfur dioxide residue detected in the dried T. fuciformis produced by the process currently practiced by the industry.