Changes during ensilage in fermentation products, tea catechins, antioxidative activity and in vitro gas production of green tea waste stored with or without dried beet pulp

Wet green tea waste (GTW) was ensiled in laboratory silos with or without dried beet pulp at a ratio of 2:1 on a fresh weight basis. The silos were opened at 15, 30 and 60 days after anaerobic storage; fermentation products, tea catechins, antioxidative activity and in vitro gas production were determined. Acetic acid prevailed over the fermentation and the pH declined to below 4.2 when wet GTW was ensiled alone. Addition of dried beet pulp greatly enhanced lactic acid production and the pH further decreased to below 3.8 with no butyric acid being detected. Approximately 90% and 80% of (-)-epicatechin gallate and (-)-epigallocatechin gallate, respectively, were degraded in silage prepared from wet GTW alone, while the degradation was ameliorated in mixed silage to about 55% and 70%, respectively. Antioxidative activity was not markedly altered by ensiling and 70-80% of the initial activity was detected after 60 days. Changes were small in (-)-epigallocatechin, caffeine and total phenols with or without mixing with dried beet pulp. In vitro gas production was similar between materials and their silages, indicating that reduction of tea catechins would not elicit an improvement in digestibility. It is concluded that wet GTW can be ensiled successfully without bacterial inoculants when mixed with other materials containing certain sugars. Ensiling may degrade part of the components of tea catechins, while not affecting total phenols, antioxidative activity and digestibility of wet GTW.