Optimized processing and formulation for retaining the sensory and nutritional quality of mustard leaf tea

Abstract

The potential of mustard (Brassica juncea) leaves as a raw material for herbal tea remains unexplored. This study aimed to evaluate the suitability of mustard leaves for tea production and optimize processing and formulation. Four mustard varieties were evaluated using traditional green tea processing techniques, demonstrating that purple-leaf mustard is an excellent raw material for herbal tea, both in terms of sensory properties and bioactive compounds. Next, eight processing methods for purple-leaf mustard were employed. The mustard leaf tea, processed using a combination of steaming fixation, rolling, and vacuum freeze-drying technology, demonstrated effective preservation of health-promoting compounds while maintaining a desirable flavor profile. Blending mustard leaf tea with Maofeng green tea or Tieguanyin oolong tea further enhanced its aroma and taste. This study developed a novel herbal tea using purple-leaf mustard and provides a reference for producing high-quality herbal teas with a unique flavor profile and health-promoting compounds.

Keywords: Blended tea; Brassica juncea; Health-promoting compounds; Herbal tea; Processing technology; Sensory evaluation.

Fig. 1

The sensory evaluation and nutrient compounds of the mustard leaf teas produced by four leaf mustard varieties. (A) Appearance of fresh leaf, dried tea and tea infusion of four varieties of leaf mustard; (B) Sensory evaluation of mustard teas produced by four varieties of leaf mustard; (C)-(J) The content of total anthocyanin (C), total chlorophyll (D), total glucosinolate (E), soluble sugar (F), ascorbic acid (G), total phenolics (H), and the level of FRAP (I) and ABTS⁺ in the four dried mustard tea. Different letters above the bars indicate significant differences (P < 0.05), the same as below. Differences were evaluated using the Least Significant Difference (LSD) test.

Fig. 2

The manufacturing processes and sensory evaluation for purple mustard leaf tea. (A) Outlines of manufacturing processes for eight types of mustard leaf tea; (B) The sensory evaluation of mustard leaf tea produced by different manufacturing processes. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Anthocyanins, Chlorophyll and Carotenoids contents of mustard leaf tea processed by different methods. (A) Cya-3-sin-5-mal; (B) Cya-3-caf-5-mal; (C) Cya-3-fer-5-glu; (D) Cya-3-p-cou-sin-5-mal; (E) Cya-3-p-cou-fer-5-mal; (F) Total anthocyanins; (G) Chlorophyll a; (H) Chlorophyll b; (I) Total chlorophyll; (J) Lutein; (K) Neoxanthin; (L) β-carotene; (M) Violaxanthin; (N) Total carotenoids. Each data point represents the mean ± SD of triple biological replicates.

Fig. 4

GSL and their breakdown products contents of mustard leaf tea processed by different methods. (A) sinigrin; (B) gluconapin; (C) 4-methoxyglucobrassicin; (D) glucobrassicin; (E) 4-hydroxy glucobrassicin; (F) neoglucobrassicin; (G) total aliphatic glucosinolate; (H) total indolic glucosinolate; (I) total glucosinolate; (J) SIN-ITC; (K) SIN-CN; (L) SIN-EPN; (M) GNA-ITC; (N) GNA-CN; (O) GNA-EPN; (P) Total ITC; (Q) Total CN; (R) Total EPN; (S) Total GBP.

Fig. 5

Soluble sugar (A-D), free amino acid (E), ascorbic acid (F), total phenolics (G) content and antioxidant capacity levels (H—I) of mustard leaf tea processed by different methods.

Fig. 6

Time-related trajectory analysis of mustard leaf tea processed by different methods.

Fig. 7

The purple mustard leaf tea blended with fourteen traditional Chinese teas. (A) The appearance of fourteen traditional Chinese teas and the tea infusion of the fourteen traditional Chinese teas brewed after being blended with mustard leaf tea in a 1:1; (B) The sensory evaluation of the mustard leaf teas blended with fourteen traditional Chinese teas. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 8

The model illustrating the manufacturing process of purple mustard leaf tea and the blended teas produced by mustard leaf tea mixed with Tieguanyin oolong tea or Maofeng green tea. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)