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Objective: This study aimed to investigate the varieties and contents of volatile components in fermented dough with flavor fermentation broth at different fermentation time. Methods: Headspace solid phase microextraction-gas chromatography (HS-SPME-GC-MS) was used to determine the volatile flavor substances in the dough of the flavor ferment at 12, 24, 36, 48 and 72 h. Also, sensory evaluation of the odor and determination of pH value, total acidity (TAA) and rheological properties of the dough were measured. Results: The strength of eight odors (frankincense, cheese, flower, fruit sweet, wine, malt, grass and sour) showed different performance, depending on the types and contents of the flavour substances produced during the different fermentation periods. The pH value of the dough gradually decreases with the time of fermentation, while TTA was the opposite. The tensile resistance, stretch ratio and tensile area of dough increased first but decreased with the extension of fermentation time, while the elongation of dough decreased first then increased. These results indicated that moderate fermentation (36 h) was beneficial to the formation and stability of the gluten network. A total of 92 volatile substances were detected in the dough with 5 fermentation times, including 22 alcohols, 27 esters, 12 aldehydes, 14 ketones, 10 alkanes, and 7 acids. A total of 27, 43, 38, 41 and 37 volatile flavor components were detected from the dough fermented for 12, 24, 36, 48 and 72 h, respectively. The contents of acids and esters increased first then decreased with the prolongation of fermentation time and reaching the highest at 48 h (47.31% and 20.96%, respectively). On the other hand, the contents of aldehydes, ketones and acids all gradually decreased. Conclusion: The volatile substances of different fermentation times were alcohols mainly, and the total flavor substances and the relative content of alcohols and esters reached the highest at 48 h, indicating that alcohols and esters might be the major contributors to the flavor of dough during fermentation.

Widespread autotoxicity is an important obstacle to natural regeneration of many plants. The rare relict plant Metasequoia glyptostroboides is a difficult to natural regeneration and is affected by litter allelopathy. However, little is known about the potential influence of autotoxic substances on different regeneration stages of M. glyptostroboides. We identified multiple chemical compounds of aqueous extracts from fresh (recently accumulated) and natural litter (mixture of litter different phases of decomposition), to evaluate the autotoxic effects of the four most important detected compounds applied individually on seed germination and seedling growth of M. glyptostroboides. Results found that the 28 chemical compounds were identified in the aqueous extracts of M. glyptostroboides litter. The Jaccard similarity coefficient of chemical compounds in aqueous extracts of fresh and natural litter of M. glyptostroboides reached 50%. The number of chemical compounds in fresh litter was 5.56% more than that in natural litter. Catechol, trifluoroacetamide, benzoic acid and D-(+)-arabitol significantly affected seed germination rate, seed germination index, vigor index, shoot length and main root length of M. glyptostroboides. Specifically, benzoic acid had the strongest inhibitory effect, followed by catechol, trifluoroacetamide and D-(+)-arabitol. The autotoxic effect was concentration dependent, low concentrations were positive and neutral, high and extremely high concentrations were negative for all the chemical compounds. Moreover, catechol, trifluoroacetamide, benzoic acid and D-(+)-arabitol were autotoxic substances affecting the natural regeneration of M. glyptostroboides, as well as strongly inhibited at the shoot growth stage. This study confirms that natural regeneration of M. glyptostroboides is restricted by a large amount of litter coverage under the forest, highlighting how the chemical compounds responsible for the autotoxic characteristics of M. glyptostroboides affect the different regeneration stages of M. glyptostroboides. [ABSTRACT FROM AUTHOR]