Characterization of the Sensory Properties and Quality Components of Huangjin Green Tea Based on Molecular Sensory-Omics

Characterization of key aroma in Huangjincha black tea processed from four different cultivars

Huangjincha (HJC) is a cultivar rich in amino acids making it ideal for producing high-quality black tea. In this study, the aroma composition of HJC black tea from four different cultivars (HJC1, HJC2, HJC18, and HJC168) was analyzed by aroma sensory evaluation combined with volatile compound analysis. Among 271 identified volatiles, with 39 compounds as key odorants contributing to the diverse aromas of HJC black teas. The OAV and GC-O results indicated that geraniol and benzeneacetaldehyde (HJC1), 3-methylbutanal and 1-penten-3-ol (HJC2), (E, E)-2,4-hexadienal and damascenone (HJC18), as well as methyl salicylate and citral (HJC168) were the most significant aroma compounds. Furthermore, PLS analysis revealed four odorants contributed to floral characteristic, three were related to fruity attribute, four were associated with green attribute, three were connected to fresh attribute, three were linked to nutty profile, and three were tied to the sweet profile.

Evaluation of key taste components in Huangjin green tea based on electronic tongue technology

A random forest algorithm combined with correlation analysis, was employed to identify key taste compounds in Huangjin green tea by using an electronic tongue. A total of 45 commercial Huangjin green teas were analysed for their amino acids, catechins, gallic acid, and caffeine using an amino acid analyser and HPLC. In this study, taste compounds of 30 were quantified, and 16 of these compounds exhibited taste activity values greater than 1 in the tea samples, including 6 amino acids, 8 catechins, as well as gallic acid and caffeine. Among these compounds, 5 compounds showed relatively high importance and strong correlations (P < 0.05) with the response of electronic tongue; specific for theanine, glutamic acid, lysine, gallocatechin, and catechin. A taste reconstruction experiment further confirmed that these 5 compounds significantly contributed to the overall taste profile, particularly enhancing the umami flavour.

Progress of research on aroma absorption mechanism and aroma fixation pathway of jasmine green tea

This overview summarizes the latest research progress on the aroma absorption mechanism and aroma fixation pathway of jasmine green tea, and discusses in depth the aroma absorption mechanism of green tea, the aroma release mechanism of jasmine flowers, as well as the absorption and fixation mechanism of the aroma components of jasmine green tea in the process of scenting, to provide a theoretical basis for the improvement of the quality of jasmine green tea and the innovation of processing technology. It was found that the aroma absorption mechanism of jasmine green tea is mainly associated with both physical and chemical adsorption, aroma release in jasmine involves the phenylpropanoid/benzoin biosynthetic pathway, β-glycosidase enzymes interpreting putative glycosidic groups, and heat shock proteins (HSPs) as molecular chaperones to prevent stress damage in postharvest flowers due to high temperatures and to promote the release of aroma components, and so forth. The preparation of aroma-protein nano-complexes, heat stress microcapsules, and the spraying of polymeric substances - β-cyclodextrin are three examples of aroma-fixing pathways. This overview also summarizes the problems and future development trends of the current research and proposes the method of loading benzyl acetate, the main aroma component of jasmine, through konjac glucomannan (KGM)-based gel to solve the problem of volatile aroma and difficult-to-fix aroma, which provides a reference for the sustainable development of the jasmine green tea industry. © 2024 Society of Chemical Industry.

Z, Cai X, Zhao X, Jiang Y, Miao B. Quality Assessment of Loquat under Different Preservation Methods Based on Physicochemical Indicators, GC–MS and Intelligent Senses

To explore the effects of different preservation methods on the quality of loquat after fresh-keeping treatment, various preservation techniques were employed. These included natural preservation (NP), vacuum freezing preservation (VFP), vacuum at room temperature preservation (VP) and freezing preservation (FP). The quality assessment involved analyzing the effects of these preservation methods using physicochemical indexes, a colorimeter, an electronic nose (E-nose), an electronic tongue (E-tongue) and gas chromatography–mass spectrometry (GC–MS). The results showed minor differences in loquat quality under different preservation methods, with sensory scores ranging from 55 to 78 and ΔE values ranging from 11.92 to 18.59. Significant variations were observed in moisture content (ranging from 53.20 g/100 g to 87.20 g/100 g), calorie content (ranging from 42.55 Kcal/100 g to 87.30 Kcal/100 g), adhesion (ranging from 0.92 to 1.84 mJ) and hardness (ranging from 2.97 to 4.19 N) (p < 0.05). Additionally, the free amino acid content varied from 22.47 mg/g to 65.42 mg/g. GC–MS analysis identified a total of 47 volatile flavor substances in varieties of loquats, including 13 aldehydes, 9 esters, 6 ketones, 2 acids, 3 alcohols, 2 phenols, 3 pyrazines, 1 furan and 8 other substances. The relative content of aldehydes was significantly higher than that of other chemicals. The VFP and FP samples exhibited higher aldehyde content compared to the NP and VP samples. Moreover, Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) revealed 18 marked compounds that could differentiate between 5 loquat species. Analysis using E-nose and E-tongue indicated significant changes in the olfactory and gustatory senses of loquats following preservation. The VFP samples demonstrated the most effective preservation of loquat quality with minimal impact. This study provides some theoretical guidance for the home preservation of loquats.