Preparation of Water Soluble Powder of Propolis and the Quality Changes of its Bread during Storage

Propolis 수용성분말 제조 및 이를 첨가한 빵의 저장 중 품질변화

The properties of water soluble powder of propolis(WSP), made with different levels(0, 20, 40, 60, 80%) of ethanol extract of propolis(EEP) and hydrocolloid were investigated, along with the quality changes of its bread after 7 days' of storage at $30^{\circ}C$ The yield of WSP containing 40% EEP treated at $160^{\circ}C$ was the highest at 59.3% and the brown color of all the powders tended to be darkened with increasing EEP content. The turbidity of WSP treated at higher temperature was decreased in its aqueous solution (10%, w/w), and this was considered to be due to the presence of minute nonsoluble particles. Antioxidative activities determined by DPPH(1,1-diphenyl-2-picrylhydrazyl) were the lowest in WSP treated at $140^{\circ}C$, while those of the WSP samples prepared at 160 and $180^{\circ}C$ were as high as that of WSP containing more than 40% EEP, regardless of EEP concentration. The propolis breads with added WSP made at $160^{\circ}C$ were selected as the most desirable powder for subsequent study. Bread with WSP40 was the heaviest while the volume loss of WSP80 was the greast after baking. The moisture contents of the propolis bread were drastically decreased until 3 days' of storage, but it was thought that WSP might be ineffective for the prevention of moisture loss. The pH of breads without EEP was decreased after 3 days' of storage, while that of the WSP breads remained almost unchanged until 5 days' of storage. Total bacterial counts also exhibited decay levels during the storage. In conclusion, water soluble powder of propolis is useful as a natural antioxidative and antibacterial material in various types of food.