Characterization of aromas of instant oolong tea and its counterparts treated with two crude enzymes from Aspergillus niger

Abstract

Sensory evaluation, GC–MS and omission test were used to characterize aromas of noninstant Oolong tea (NIOT), original instant Oolong tea (OIOT) and its counterparts treated by two enzyme extracts from Aspergillus niger. The results showed that OIOT had stronger sweet, fruity, and roasted notes, but weaker grass and floral notes than NIOT. After treated by the crude enzymes extracted from the fermented broth from tea waste (TW) medium, the treated‐OIOT had an improved aroma similar to that of NIOT, due to the increases of 2‐pentyl‐furan and 3‐cis‐hexen‐1‐ol. In comparison, after the treatment of crude enzymes from wheat bran and orange peel (WBOP) medium, the treated‐OIOT showed significantly aroma difference from NIOT and OIOT, which was attributed to the increases of 3‐cis‐hexen‐1‐ol, γ‐terpinene, and β‐trans‐farnesene. These results revealed that the original aroma of OIOT could be effectively modified and improved by the enzyme extracts, particularly by that from the TW medium. Practical applications Tea is one of the most popular beverages all over the world. Instant tea is an important tea product that is processed from teas by extraction, concentration and drying. Instant tea is more convenient than teas for industrially producing tea foods such as tea beverage, tea break, and tea ice cream. However, the aroma profile of instant tea is always inferior to those of the original unprocessed noninstant teas, because the characteristic aroma of the original unprocessed tea could undergo significant changes during the preparation of instant tea. The present manuscript shows two enzyme extracts from Aspergillus niger could improve the aroma of instant Oolong tea, providing interesting information to promote the aroma of instant tea via enzymatic treatments, which may help to develop effective approaches to enhancing the quality of instant teas.

Characterization of the Aroma of an Instant White Tea Dried by Freeze Drying

“…The present SDE extract and IWT had the characteristic aroma different from those of fresh, slightly brewed whites, but the dominating sweet note seemed similar to that of the aged white tea as reported in previous literatures [9,24]. Although few literatures currently report the effects of instant tea preparation on the aroma of IWT, it has been shown that some factors such as heating and oxidation during instant tea processing could affect the sweet, green and floral odors of tea products [4,25]. For instance, when Pu-erh tea was processed into instant Pu-erh tea, the sweet attribute significantly increased [4].…”

“…For instance, when Pu-erh tea was processed into instant Pu-erh tea, the sweet attribute significantly increased [4]. In addition, when oolong tea was processed into instant oolong tea, the intensities of sweet, fruity and roasted notes increased significantly, but the intensities of floral and grass notes decreased significantly [25]. Therefore, the IWT and SDE extract had a dominated sweet note, which might be attributed to the heating and oxidation process during instant tea preparation.…”

“…Before the quantitative descriptive analysis, panelists had discussed aroma compositions of samples through three preliminary sessions (each spent 3 h) until all of them agreed to the attributes, according to the statements from ISO 8589 and previous researches [25,39] with slight modifications. The green, floral, sweet, woody, roasted and fruity notes were selected as indicators for sensory evaluation.…”

“…All the panelists were trained to distinguish the aroma characteristics and intensities using a series of standards solutions. In detail, standard solutions of hexanal (green) [25], linalool (floral) [25], benzeneacetaldehyde (sweet) [32], trans-β-Ionone (woody) [11], 2,5-dimethylpyrazine (roasted) [30] and 1-octanol (fruity) [11] were used to train panelists to get familiar with the aroma characteristic and intensity.…”

Fermentation by Multiple Bacterial Strains Improves the Production of Bioactive Compounds and Antioxidant Activity of Goji Juice

“…The concentration of 2-pentyl-furan, a fatty acid oxidation product [26], increased by 8.72, 6.44, and 11.63 times after being fermented with SLV, SZP, and SZVP, respectively. Zhang et al [27] found that the enzymes produced by Aspergillus in fermentation of tea increased the content of 2-pentyl-furan, thereby enhancing the floral and grassy odors to improve the sensory quality. Therefore, it is proposed that the metabolites produced by the fermentation strains may increase the 2-pentyl-furan content, where the metabolites generated by B. velezensis may be important.…”