Ru Yue-Rong, Wang Zhen-Xing, Li Ya-Jing, Kan Huan, Kong Kin-Weng, Zhang Xue-Chun
Key Laboratory for Forest Resources Conservation and Utilization in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming, China.
College of Life Sciences, Southwest Forestry University, Kunming, China.
J Food Biochem. 2022 Apr;46(4):e13887. doi: 10.1111/jfbc.13887. Epub 2021 Aug 2.
In this study, the walnut flowers were fermented using five different probiotics, including two Lactobacillus plantarum, one Lactobacillus bulgaricus, one Lactobacillus casei, and one Lactobacillus rhamnosus. The chemical compositions, antioxidant capacities, and α-glucosidase inhibitory abilities of walnut flowers during fermentation processes were evaluated. The results showed that all the active compounds and bioactivities of the walnut flowers were significantly decreased after 7 days of fermentation, whereas a short-term fermentation (1-3 days) enhanced their bioactivities. Compared to the unfermented sample, L. plantarum (ATCC 8014) and L. rhamnosus (ATCC 53013) increased the ABTS (1.22 and 1.30 times higher) and DPPH radical scavenging activities (up to 1.23 and 1.04 times), respectively. L. plantarum (SWFU D16), L. plantarum (ATCC 8014), and L. rhamnosus (ATCC 53013) improved the ferric reducing antioxidant power which was 110.98%, 133.16%, and 104.76% of the unfermented sample. All five probiotics promoted the α-glucosidase inhibitory ability of walnut flowers (maximum 2.18-fold increase). Three phenolic acids and five flavonoids in the fermentation broth were identified by HPLC, where catechin, epicatechin, and catechin gallate were the dominant components. HPLC results demonstrated that these compounds were degraded and transformed in varying degrees under the effects of probiotics. Taken together, a short-term probiotic fermentation could change the active compounds of the walnut flowers and improve their bioactivities. L. plantarum (ATCC 8014) and L. rhamnosus (ATCC 334) are suggested as suitable strains in producing the fermented walnut flowers. The research findings could further support the development and utilization of walnut flowers as a fermented functional food. PRACTICAL APPLICATIONS: Walnut flowers have been used as fermented food in southwestern China, but their active components and functional activities during fermentation processes are still unclear. This study found that different probiotic fermentation exerted a strong and varied influence on the chemical composition and biological activities of the walnut flowers. A short-term fermentation has significantly improved their antioxidant capacities and α-glucosidase inhibitory abilities, whereas the longer period of fermentation, caused a significant loss of both their active compounds and bioactivities. These findings are useful as a reference for the manufacturers of fermented walnut flowers in selecting suitable strains and fermentation time for their products.
在本研究中，使用五种不同的益生菌对核桃花进行发酵，其中包括两株植物乳杆菌、一株保加利亚乳杆菌、一株干酪乳杆菌和一株鼠李糖乳杆菌。对发酵过程中核桃花的化学成分、抗氧化能力和α-葡萄糖苷酶抑制能力进行了评估。结果表明，发酵7天后，核桃花的所有活性成分和生物活性均显著降低，而短期发酵（1-3天）则增强了它们的生物活性。与未发酵样品相比，植物乳杆菌（ATCC 8014）和鼠李糖乳杆菌（ATCC 53013）分别提高了ABTS（分别高出1.22倍和1.30倍）和DPPH自由基清除活性（分别高达1.23倍和1.04倍）。植物乳杆菌（SWFU D16）、植物乳杆菌（ATCC 8014）和鼠李糖乳杆菌（ATCC 53013）提高了铁还原抗氧化能力，分别为未发酵样品的110.98%、133.16%和104.76%。所有五种益生菌均促进了核桃花的α-葡萄糖苷酶抑制能力（最大增加2.18倍）。通过高效液相色谱法（HPLC）鉴定了发酵液中的三种酚酸和五种黄酮类化合物，其中儿茶素、表儿茶素和儿茶素没食子酸酯是主要成分。HPLC结果表明，这些化合物在益生菌的作用下发生了不同程度的降解和转化。综上所述，短期益生菌发酵可以改变核桃花的活性成分并提高其生物活性。建议将植物乳杆菌（ATCC 8014）和鼠李糖乳杆菌（ATCC 334）作为生产发酵核桃花的合适菌株。研究结果可为核桃花作为发酵功能性食品的开发利用提供进一步支持。实际应用：核桃花在中国西南部已被用作发酵食品，但其在发酵过程中的活性成分和功能活性仍不清楚。本研究发现，不同的益生菌发酵对核桃花的化学成分和生物活性产生了强烈且多样的影响。短期发酵显著提高了它们的抗氧化能力和α-葡萄糖苷酶抑制能力，而较长时间的发酵则导致其活性成分和生物活性均显著丧失。这些发现可为发酵核桃花制造商在为其产品选择合适的菌株和发酵时间时提供参考。
