Evaluation of microbial toxins, trace elements and sensory properties of a high‐theabrownins instant Pu‐erh tea produced using Aspergillus tubingensis via submerged fermentation

Abstract

Theabrownins (TB) are polymeric phenolic compounds associated with the multiple bioactivities of Pu‐erh tea, a post‐fermented Chinese dark tea. High‐TB instant Pu‐erh tea was produced via a novel submerged fermentation (SF) using Aspergillus tubingensis and compared with samples produced commercially via the conventional solid‐state fermentation (SSF). Viable microorganisms and microbial toxins, especially aflatoxins B₁, G₁, B₂, G₂, cyclopiazonic acid, fumonisins B₁, B₂, B₃ and ochratoxin A, were below the detection limit in all samples. Fewer microbial metabolites were found in SF instant tea compared with the SSF teas. Based on an adult consuming 1\xa0g of instant Pu‐erh tea daily, the dietary intake of investigated elements was below the safe limits recommended by various authorities. Tasters viewed the instant tea infusions as very mild, smooth, mellow and full. This suggested that submerged fermentation using A.\xa0tubingensis offers a speedy and safe alternative to commercial production of instant Pu‐erh tea.