| 報告時間：2025-6-20 |
| 報告地點：Room 407 |
| 指導老師：Yu-Tse Liu, Ph.D. |
| 學生：Xin-Yi Wu |
| 摘要 |
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Shio Koji, a common fermented seasoning in Japan, is produced by fermenting rice koji, salt, and water. The rice koji mold (Aspergillus oryzae) hydrolyzes the substrate, imparting a rich flavor and diverse components. With rising health awareness, natural antioxidants have gained attention. Moreover, since 2020, the World Health Organization has established global sodium content standards for different food categories, advocating sodium reduction to lower the risk of hypertension and cardiovascular diseases. Therefore, this study aimed to investigate the physicochemical properties and antioxidant capacity of Shio Koji fermented with different salt concentrations and to evaluate its application in Chinese sausages as a partial replacement for salt and sodium erythorbate, assessing the effects on sausage quality during refrigerated storage. The study had two parts. In Experiment 1, dried rice koji was mixed with water at a 3:4 ratio, and salt was added at concentrations of 0% (S0), 5% (S5), 10% (S10), and 15% (S15). The mixtures were fermented at 30°C for 8 days. Samples were extracted on days 0, 2, 4, 6, and 8 to measure physicochemical properties and antioxidant capacity. Results showed that the pH value of S0 gradually increased during fermentation, whereas salted groups exhibited a decreasing trend. Regarding color value, L* values decreased over fermentation time, with higher salt concentrations causing more pronounced decreases. The a* value of S0 shifted from slightly green to slightly red, while other groups showed minimal changes due to salt's inhibitory effects. All groups exhibited yellowish b* values. Antioxidant assays demonstrated that all groups had optimal DPPH-scavenging effects, ferrous ion chelating activity, and reducing power assay results on day 6. Notably, S5, S10, and S15 exhibited DPPH-scavenging effects comparable to BHT and ferrous ion chelating activity like EDTA. Although S0 had the highest total phenolic content, its antioxidant capacity was inferior to salted groups, indicating that total phenols were not the main contributors to antioxidant activity. Considering antioxidant capacity, cost, and food safety risks, Shio Koji fermented with 15% salt for 6 days was selected for experiment 2. In experiment 2, pork hind leg meat and fat were used to prepare Chinese sausages with Shio Koji fermented for 6 days at 15% salt. Four formulations were prepared by adjusting salt and sodium erythorbate levels: Control (C), Low shio koji plus sodium erythorbate (LSKE), Low shio koji (LSK), and High shio koji (HSK). Samples were vacuum-packed in ziplock bags and refrigerated at 4°C for 4 weeks, with measurements taken at weeks 0, 1, 2, 3, and 4. Samples for sensory evaluation and texture profile analysis were vacuum-sealed and stored at -20°C, then cooked before testing. Results revealed that after 4 weeks, LSK and HSK groups showed minimal changes in pH value and b* values, while L* values increased. Total plate count and volatile basic nitrogen (VBN) values in these groups were lower than those in the control and LSKE groups, indicating some antimicrobial effects. However, without sodium erythorbate, the a* values in LSK and HSK declined significantly, residual nitrite content fluctuated, and Thiobarbituric acid reactive substances (TBARS) levels were elevated, reflecting poorer antioxidant stability. Sensory evaluation indicated that the HSK group had the lowest overall preference due to excessive salt reduction negatively impacting flavor and texture. Texture profile analysis showed that hardness, chewiness, and cohesiveness decreased in LSK and HSK compared to the control, with chewiness and cohesiveness being the lowest among all groups. In contrast, although the LSKE group exhibited a declining pH value and increasing total plate count and VBN values in later storage stages, the combined addition of Shio Koji and sodium erythorbate stabilized the color value and promoted a reduction in residual nitrite content. TBARS levels in LSKE were lower than those in LSK and HSK. Sensory evaluation scores for LSKE were highest in color, aroma, saltiness, umami, sweetness, juiciness, chewiness, and overall acceptability, even surpassing the control. Texture profile analysis showed no significant difference in springiness compared to other groups; however, hardness, chewiness, and cohesiveness decreased relative to the control but remained higher than other reduced-salt groups. In summary, the LSKE group demonstrated superior performance in residual nitrite content management, color stability, and sensory evaluation. It is recommended to add alcohol during Shio Koji preparation to enhance antimicrobial effects and reduce contamination risks before further application in meat products. Future studies should evaluate the feasibility of the commercial application of Shio Koji in Chinese sausages to achieve salt reduction, flavor enhancement, and quality stability. |
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