Bioscience Methods 2025, Vol.16, No.3, 154-161 http://bioscipublisher.com/index.php/bm 155 2 Introduction to Raw Materials in Vinegar Production 2.1 Nutritional and active substances of native citrus components Native citrus fruits and their related fruits are rich in essential nutrients and active ingredients such as vitamins, organic acids, phenolic substances and natural sugars. These substances not only endow vinegar with nutritional value, but also enhance its functional properties and health potential. Taking studies such as apple kiwi vinegar and ginseng vinegar as examples, it has been confirmed that the generation of vitamins, phenolic substances and special aromatic substances during the fermentation process of raw materials can not only enhance the flavor layers, but also generate health benefits (Wen et al., 2012). Fermentation promotes the transformation of these active substances, significantly increasing the content of phenolic acids and aromatic compounds. Whether it is grain vinegar or fruit vinegar, phenolic components are the core functional substances in acetic acid fermentation, and their formation is jointly regulated by the characteristics of raw materials and the activity of microorganisms. These phenolic substances, in synergy with amino acids, organic acids and other components, jointly constitute the material basis of the antioxidant and health-promoting properties of vinegar. 2.2 The enhancing effect of ecological planting on the quality of raw materials Cultivating raw materials such as citrus fruits through ecological planting methods helps maintain the integrity and content of nutrients, which is crucial for the production of high-quality vinegar. Raw materials that grow naturally with little processing can not only avoid pollution, but also retain healthy active substances to the greatest extent, and further enhance their functions during the fermentation process (Román-Camacho et al., 2022). Ecological cultivation also provides a stable and rich microbial community for the fermentation system, which plays a key role in the stable formation of flavor substances and functional components. Studies have shown that natural raw materials can regulate the protein expression and metabolic patterns of acetic acid bacteria, thereby optimizing the transformation of nutrients and the synthesis of beneficial compounds (Gu, 2011). 2.3 Raw material characteristics and value of Yuyue orange vinegar The advantage of Yuyue orange vinegar lies in its use of carefully selected citrus fruits as raw materials, effectively utilizing the natural nutrients and aroma components within the fruits. The multi-stage sorting process is adopted to ensure the flavor characteristics of the product and promote the accumulation of more active components such as phenolic substances and organic acids during the fermentation stage (Liu et al., 2024) The use of local citrus raw materials grown ecologically not only endows the product with significant health advantages but also forms market competitiveness. The synergy between the natural characteristics of raw materials and traditional craftsmanship enables the product to have both excellent sensory quality and functional value, which is significantly different from vinegar made from conventional raw materials (Liu et al., 2011). 3 Analysis of Vinegar Brewing Process (Yuyue Brand Orange Vinegar as an Example) 3.1 Core processes of traditional craftsmanship The traditional vinegar-making process shapes the flavor and functional characteristics of the product through four key stages. First, the starch saccharification stage is carried out. Enzymatic hydrolysis converts starch into fermentable sugars. Then it enters the alcoholic fermentation stage, where yeast metabolizes sugar into ethanol. Then, acetic acid is generated through the ethanol oxidation reaction led by acetic acid bacteria, forming the basic sour taste. The final aging stage promotes the maturation of flavor substances and the accumulation of active components. This technological system has been fully verified in traditional products such as Zhenjiang fragrant vinegar (Zhang et al., 2013; Gong et al., 2021). The dynamic evolution of physicochemical indicators and metabolites was presented at each stage. In the early stage of fermentation, the content of reducing sugar drops rapidly, while the acidity and the concentration of
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