Effects of different levels of Lactobacillus casei and Houttuynia cordata Thunb. on chemical, physical and antioxidant properties of bio-fermented Houttuynia cordata juice

Abstract

This study aimed to investigate the effects of different levels of Lactobacillus casei (L. casei) and Houttuynia cordata powder (HCP) on the chemical, physical properties and antioxidant activity of bio-fermented juice. The experiment was arranged in a 4 × 3 factorial in a completely randomized design (CRD). Factor A consisted of four levels of L. casei at 0, 1, 10 and 20% (v/v), and Factor B comprised three levels of HCP at 10, 12.5 and 15% (w/v). The variables analyzed included total bacterial count, total phenolic content, total flavonoid content, quercitrin concentration, antioxidant activity (DPPH IC₅₀ and ABTS IC₅₀), moisture content, pH, total soluble solids, and total acidity. The results demonstrated that both the levels of L. casei and HCP significantly influenced the properties of bio-fermented Houttuynia cordata juice (p<0.05). Notably, the group supplemented with 1% L. casei and 15% HCP showed the highest total bacterial count at 8.667 × 10⁶ CFU/ml, along with a total phenolic content of 22.351 mg/g, total flavonoid content of 13.874 mg/g, and quercitrin content of 904.438 µg/L. In addition, this group exhibited favorable antioxidant activities, with DPPH IC₅₀ and ABTS IC₅₀ values of 398.297 µg/ml and 145.239 µg/ml, respectively. These findings indicate a well-balanced combination of microbial population, bioactive compounds, and antioxidant capacity, highlighting the potential of using 1% L. casei with 15% HCP as an optimal formulation for producing bio-fermented Houttuynia cordata juice with desirable chemical, physical, and biological properties suitable for application in the livestock industry.