利用常壓低溫電漿處理縮短發芽梗糙米煮飯時間及提高γ-氨基丁酸(GABA)含量

Abstract

發芽糙米，為僅除去稻米外殼的糙米在適當水分及溫度下培養，吸水澎潤 後，開始活化進行各種發芽所需之代謝作用，至胚芽突出而成。發芽糙米相較於 精白米有更高營養價值。但由於糙米質地堅硬，口感較差，且烹飪後外觀暗淡， 因此不如精白米受消費者歡迎。發芽糙米質地明顯較軟，且風味因風味分子在發 芽過程中分解釋放而增強，此外，其 γ-氨基丁酸 (gamma-aminobutyric acid, GABA) 及肌醇等生物活性成分含量亦增加。發芽糙米中 GABA 含量高於精白米 10 倍之多。GABA 是一種非蛋白氨基酸，在動物體內扮演一主要抑制性神經傳導 物質。有許多研究指出它具有一系列促進健康益處功能，如抗糖尿病和降血壓作 用、抑鬱和減少焦慮、抑制癌細胞增殖、改善大鼠記憶和學習能力等。電漿為物 質第四態，是對物質施加高溫或加速電子、離子等能量，產生大量如分子、原 子、電子、正負離子、受激態物質、自由基、UV 光等物質，在食品工業上主要 使用於改變受處理食物的表面性質及滅除表面微生物等。在本研究中，使用常壓 非熱式電漿 (atmospheric non-thermal plasma, ANP) 以較低的電漿能量 (7 W、8 W、14 W、15 W) 處理糙米，探討其是否可迅速磨損種子表面，進而促使提高糙 米吸水率、發芽率，同時是否有更軟化發芽糙米中的質地和增加 GABA 含量的結 果。在 14 W 及 15 W 處理下，24 小時的糙米發芽率皆達 95 %以上，較控制組的 89 %高，減少糙米發芽時間。此外，糙米經過 15 W 電漿處理後，吸水率在 48 小 時達到 39 %，較控制組 35 %高。在 SEM 的觀察下，也發現經電漿處理的糙米， 表面都有凹凸的現象。GABA 含量也在電漿 8W 處理緊接著培養 24 小時發芽後， 發現顯著高於控制組(22.64 mg / 100 g，33.87 mg / 100 g)。而在烹煮時間上 14 W 及 15 W 處理下，從控制組的 34 分 05 秒降顯著下降為 33 分 12 秒，及 32 分 11 秒。

Compare to milled rice, brown rice with only the outer hull removed has higher nutritional value. Through further germination, the germinated brown rice (GBR) its nutritive value and texture could be enhanced. During germination, the texture of brown rice softened, more flavor developed, and the content of bioactive component including gamma-aminobutyric acid (GABA), oryzanol, and free polyphenolics significantly increased. That is, germination greatly benefits the promotion of brown rice since it not only modified its unappealing hard texture but also making it a potent functional food. GABA, a non-proteinogenic amino acid with numerous reported health benefits research showed that it has a series of functions, such as anti-diabetic and hypotensive effects, depression and anxiety reduction, inhibit cancer cell proliferation, and improve memory and learning abilities in rats. In GBR, the contents of GABA is many times more than that in the brown rice implying its responsiveness to the stress caused by the early stage of growth. Atmospheric non-thermal plasma (ANP) contains a large amount of reactive species that could rapidly abrade the seed surface, enhance moisture absorption and, hence, promote higher germination rate. In this work, innovative uses and processing parameters of ANP as the convenient means to simultaneous soften the texture and increase GABA content in GBR. Brown rice was treated by ANP for 2 minutes at the power of different group as (a) 20k Hz/6.5k V- 7 Watt (b) 20k Hz/7k V- 8 Watt (c) 24k Hz/5.5k V-14 Watt (d) 24k Hz/6k V-15 Watt. The optimum condition for the preparation of GBR was determined based on the resulting GABA content and cooked texture. According to the result, The concentration of GABA peaked at 7 Watt treatment with 48 hours soaked, and was 1.6 times higher than the untreated group. Furthermore, the cooked texture of GBR after treated by plasma was softer in relatively shorter cooking time. In sum, ANP was successfully established as a novel application to rapidly modify the germination rate, bioactive content, and texture of brown rice. In future, this technology could be applied to many other crops with similar property.