國產甘藷之花青素組成及抗解澱粉製備之研究

Abstract

本研究分為三部分，第一部分針對兩種國產紫色甘藷(台農73號和芋心甘藷)，進行藷皮及藷肉花青素含量與DPPH自由基清除能力測定，並以HPLC/MS-MS進行花青素結構鑑定。第二部分以四種國產甘藷(台農31、66、73號及芋心甘藷)藷肉凍乾粉末為原料，將10%懸浮液先於40℃/5 min使內生性酵素(alpha及beta-amylase)對澱粉粒進行修飾，再以1、2或3次溫度循環(4℃/22h-30℃/2h)處理，使澱粉顆粒進行韌化作用，以提高甘藷粉之機能性。第三部分以國產甘藷澱粉為原料，先將澱粉糊化並以pullulanase去支鏈而得去支鏈澱粉(debranched starch, DS)，再對17% 去支鏈澱粉懸浮液進行韌化處理(121℃/15m-60℃/8h、121℃/15m-60℃/8h-4℃/16h-60℃/8h)，及80% 去支鏈澱粉懸浮液進行熱濕處理(121℃/2h)，以提高其抗解澱粉(resistant starch, RS)含量。第二及第三部分樣品，以體外消化試驗評估其消化情形及抗解澱粉含量，並進行澱粉膨潤力試驗及廣角度X-光繞射(X-ray diffraction, XRD)分析，以了解其內部結構之變化。 芋心甘藷之藷皮與藷肉花青素含量皆高於台農73號，前者分別為93.0及514.5 mg/100 g (db)，後者則分別為46.3及121.2 mg/100 g (db)。甘藷中花青素含量與其DPPH自由基呈正相關性(R2=0.9971)。HPLC/MS-MS分析得到15種花青素結構，其配醣體皆為cyanidin或peonidin，再分別接上不同醣基所構成。經過多次溫度循環，澱粉結構趨於緊密、整齊，致使水分不易滲入，膨潤力下降，導致消化酵素較不易進入澱粉粒中進行水解，因此，雖然快速可獲得之葡萄糖量(rapid available glucose, RAG)不變，緩慢可獲得之葡萄糖量(slowly available glucose, SAG )下降，但相對之抗解醣量增加，而達到提高甘藷粉機能性之目的。但是經過濕熱處理之紫色甘藷凍乾粉末之花青素含量皆顯著降低。選用台農66號天然甘藷澱粉製備抗解澱粉，其天然澱粉及其去支鏈澱粉分別含有76及72%之抗解澱粉(resistant starch, RS)，再經韌化或熱濕處理後，其RS為59-82%。經韌化處理後之去支鏈澱粉由天然甘藷澱粉之C-type轉變成B-type，而濕熱處理者則為C-type。

There are three parts in this thesis. First, the anthocyanin content and DPPH radical scavenging of two Taiwanese purple sweet potatoes (TN73 and Taro-sp) were determined, as well as the anthocyanins’ structures of flesh and skin were identified by using the HPLC/MS-MS. Second, the four Taiwanese freeze-dried sweet potato flesh flour were prepared to be 10% suspension and treated at 40℃/5 min for the modification with endogenous enzymes (alpha and beta-amylase), followed by the additional treatment with 1, 2 and 3 temperature cycles (4℃/22h-30℃/2h). The annealed starch and flour will improve the functionality of sweet potato flour. Third, the sweet potato starch isolated from Taiwanese sweet potatos were be gelatinized and debranched with pullulanase to obtain the debranched starch (DS). The 17% DS suspension was then annealed either at 121℃/15 m-60℃/8h or at 121℃/15 m-60℃/8h-4℃/16h-60℃/8h, and 80% DS suspension was heat-moist treated at 121℃/2h to increase its resistant starch (RS) content. The in vitro digestibility was performed to evaluate the slowly available glucose (SAG) and the RS in hydrothermal treated sweet potato flour and starch, respectively. In addition, the swelling power and wide angle X-ray diffraction (XRD) analysis were carried out to study the changes of flour and starch structures. The anthocyanins content in skin and flesh of Taro-sp (93.0 and 514.5 mg/100 g (db)) were higher than TN73 (46.3 and 121.2 mg/100 g (db)). The DPPH radical scavenging capacity was well correlated to the anthocyanins content (R2=0.9971). There are 15 anthocyanins’ structures well identified, the aglycon of the anthocyanins was cyanidin or peonidin. After the temperature cycles treatment, the starch structure is getting to compact and order, resulting in the slow diffusion rate of water which restricts the amylase acting on the starch molecules. Although the amount of rapidly available glucose (RAG) did not change and SAG did decrease, as a result, the resistant carbohydrates were relatively increased. Through these processes, the functionality of sweet potato flour was improved. However, the anthocyanins were not stable during these processes. The RS% of TN66 native sweet potato starch, DS, and hydrothermal treated DS were 76, 72 and 59-82%, respectively. The annealed sweet potato starch had B-type crystal structure, while the native and heat-moist treated starch had C-type crystal structure.