Molecular Microbiology Research, 2025, Vol.15, No.2, 45-58 http://microbescipublisher.com/index.php/mmr 52 some links and overall process inheritance. For example, the iron-enhancing soy sauce developed by Yuyue is to add an appropriate amount of lactoferrin and soluble iron salt before packaging based on traditional brewing to enhance nutritional function while ensuring that the original soy aroma is not destroyed. This product innovation expands the functional attributes of traditional soy sauce. Industrial upgrading is also reflected in model innovation, such as Yuyue building the soy sauce brewing industrial park into a platform integrating production, popular science and tourism. Through modern display technology, consumers can intuitively understand the mysteries of soy sauce microbial fermentation and the value of traditional craftsmanship. This experience economy and cultural communication have enhanced the brand influence and brought new benefits to the company. 6 Construction and Standardization of Quality Evaluation System 6.1 Traditional evaluation and modern analysis The quality of soy sauce is traditionally mainly based on experienced brewing masters to identify sensory features from the aspects of color, fragrance, taste, etc. Wine reviewers usually judge the quality of soy sauce by observing its translucent color, smelling its rich and pure aroma, and savoring its freshness and mellowness. However, this sensory evaluation is subjective and is not easy to quantify and standardize. To this end, modern quality evaluation has introduced a method that combines instrument analysis with sensory science. On the one hand, the objective physical and chemical indicators of soy sauce are determined through chemical analysis: such as amino acid nitrogen, total nitrogen, salt, total acid, color, sugar, etc. High-quality soy sauce usually has an amino acid nitrogen content of more than 1.0 g/100mL and a balanced proportion, with moderate total acid and reddish-brown color. The analysis of the aroma and taste of soy sauce is increasingly relying on instruments and means. For example, gas chromatography-mass spectrometry (GC-MS) combined with odor olfactory resolution (GC-O) was used to analyze volatile aroma components; free amino acids and nucleotide composition were determined by high performance liquid chromatography (HPLC); and the umami, salty and bitterness intensity of the sample were objectively evaluated using an electronic tongue sensor (Feng et al., 2013). Through these analyses, a "chemical fingerprint" of a soy sauce sample can be obtained. Texture analysis, viscosity measurement, etc. are also used to evaluate the taste characteristics of soy sauce (such as consistency). However, the chemical analysis data is not a simple linear relationship with human sensory feelings. To this end, it is necessary to introduce a sensory evaluation team to conduct systematic evaluation and analyze the sensory results with physical and chemical indicators. Liu et al. (2023) conducted a sensory and physical and chemical analysis of aged soy sauce in different years, and found that as the maturity year increases, the total solids, amino acid nitrogen, and color of the soy sauce all increase (Liu et al., 2023), showing higher viscosity and darker color, and obtain higher thick, fresh sweet and mellow scores on the sensory. They also pointed out that consumers prefer soy sauces with dark colors, high viscosity and outstanding sweet and umami flavor. 6.2 Quality standardization and grade classification In order to unify the quality measurement standards in the industry, various countries have formulated quality standards for soy sauce. China's current soy sauce standard (GB/T 18186) divides soy sauce into special grade, first grade, second grade, etc. according to indicators such as amino acid nitrogen content. Extra-grade soy sauce requires amino acid nitrogen ≥0.8 g/100mL, and sensoryly requires coordinated color, aroma and odor without odor (Wang et al., 2018). This standard prompts brewing companies to strictly control processes in production to ensure that the products meet the landmark indicators. At the same time, more detailed grading is often established within the enterprise, and Yuyue will make internal grade adjustments to different batches of soy sauces to ensure the consistent flavor of the final product. In the process of quality standardization, process control standards are also indispensable. The company will formulate quality control points and parameter ranges for the entire process from raw material acceptance to fermentation, sterilization, and packaging. The application of laboratory rapid
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