- 學位論文
自然與微生物發酵木薯(Manihot esculenta, Crantz) 粉的理化性質
Physicochemical Properties of Fours of Natural and Microbial Fermented Cassava (Manihot esculenta, Crantz)
摘要
木薯 (Manihot esculenta Crantz) 是生長在非洲熱帶地區，最重要的糧食作物之一。它在努力減輕非洲糧食危機，發揮了重要作用。主要是因為其具高效生產之食物能量、可整年供應、在極端壓力條件下的耐受性及適合在目前非洲的農業和食品系統。因此，本研究的目的是調查自然和微生物發酵技術生產營養強化修飾麵粉，與修飾麵粉的理化性質比較。麵粉比較其組成份、熱與物化性質。組成份揭露出在不同處理之麵粉之間的所有參數，在α=0.05時無顯著差異。然而，總酸度與pH值可觀察到顯著的差異在兩種處理方式，微生物發酵木薯粉（MFC）組具有較高總酸度與較低pH值，這是顯示在麵粉樣品中包含更多的酸之指標。兩個麵粉的總水分含量範圍在10~20%之內，可被建議用於商業麵粉與澱粉。有高水分含量的為自然發酵木薯粉的最初（24小時）與最終（72小時）處理組，但低於微生物處理之麵粉的第二個處理組（48小時）。整體水分含量普遍偏低，這是一個穩定的保存期限之指標，如果適當的包裝和儲存。低水分是必要的，在麵粉中保持良好的品質量與較長的保存期限。兩組麵粉的蛋白質含量，在處理24、48及72小時後，分別為1.20、1.07、 1.30 與 1.24、1.23、1.17。兩組麵粉之間差異無顯著性，然而，在處理72小時後兩組麵粉之數值顯示稍高。自然發酵木薯粉（0.25％）與微生物發酵麵粉（0.25％）的灰分含量低於建議為A級工業麵粉與澱粉之0.5％限制範圍內。然而自然與微生物發酵木薯麵粉之灰分含量沒有顯著的差異，雖然兩組麵粉在最後處理（72小時）被紀錄有稍高的灰分含量。微生物發酵木薯粉在處理72小時後的纖維含量低（1.45），但在24，48和72小時的所有其他處理組，可觀察出沒有顯著性差異。自然發酵木薯（NFC） 與微生物發酵木薯麵粉之澱粉含量，分別在72小時（98.6％）和24小時（98.4）較高，與分別在24小時（84.15％）和72小時（85.1）較低。在NFC組麵粉糊化發生在較低的溫度範圍（62.03-71.75℃）相較MFC組麵粉（61.98-71.55℃），其吸熱糊化焓在MFC組麵粉較高於NFC組麵粉，雖然觀察到的差異性極小。溶脹和溶解度模式表明鬆弛溫度較低，與較高的溶脹和溶解率在MFC組麵粉，相較於NFC組麵粉。然而，溶解度沒有顯著差異被觀察，兩種處理組在溫度為60，70和80℃，雖然顯著差異在90℃時被觀察出，在所有的處理組織中，微生物發酵的麵粉比那些自然發酵的麵粉都具有較高的值。9％（乾量基準）自然發酵木薯麵粉漿的糊化特性表明較高之最終粘度、消減值及最低黏度，但較低的崩解值，相較於微生物發酵的麵粉。這表明，自然發酵木薯糊之麵粉承受加工條件可能會更好，會呈現出略優之增稠特性於微生物發酵木薯糊之麵粉。具差異性之粘彈性性質與物理功能特性之自然與微生物發酵木薯粉能被使用於選擇特定之食品與工業加工之應用。
並列摘要
Cassava (Manihot esculenta Crantz) is one of the most important staple food crops grown in tropical Africa. It plays a major role in efforts to alleviate the African food crisis because of its efficient production of food energy, year-round availability, tolerance to extreme stress conditions, and suitability to present farming and food systems in Africa. Thus, the objectives of this study were to investigate natural and microbial fermentation techniques to produce and to compare the physiochemical properties nutritionally-enhanced modified flour. The flours were compared in terms of their proximate composition, thermal and physicochemical properties. Proximate composition revealed that there were no significant differences for all parameters between both flours for different treatments at α=0.05; however, significant difference was observed for total acid and pH between treatments, with values of the microbial fermented cassava flour (MFC) higher for the total acid and lower for the pH, which is an indication that more acid is contained in the flour sample. The total moisture contents of both flours are within the 10-20% moisture level recommended for commercial flours. There was high moisture content for the first (24 hours) and final (72 hours) treatments of the natural fermented cassava flour, but lower than the microbial flour for the second (48 hours) treatments. The moisture content overall is generally low and this is an indication of stable shelf life if properly packaged and stored. Low moisture is necessary in flour for good keeping quality and longer shelf life. The protein contents for both flours were 1.20, 1.07, 1.30 and 1.24, 1.23, 1.17 for the treatments 24, 48, and 72 hours, respectively. There was no significant difference between both flours; however, slightly higher values are observed at the 72 hour treatment for both flours. The ash contents of natural fermented cassava flour (0.25%) and microbial fermented flour (0.25%) were low, and within the limit, 0.5%, recommended for grade A industrial flour and starches. Nevertheless, there was no significant difference for ash between the flour of natural and microbial fermented cassava, although slightly higher ash content for the last treatments (72 hours) of both flours were recorded. The fibre content was low for the microbial fermented cassava flour (1.45) at treatment 72 hours, but no significant difference were observed at 24, 48, and 72 hours for all other treatments. Starch content was higher in natural fermented cassava (NFC) and microbial fermented cassava flours at 72 hours (98.6%) and at 24 hours (98.4) and lowest at 24 hour (84.15%), and 72 hours (85.1), respectively. Gelatinization in NFC flour occurred at a lower temperature range (62.03-71.75 oC) compared with MFC flour (61.98-71.55 oC) with the endothermic gelatinization enthalpy having slightly higher values in flour of microbial than NFC flour, although minimal differences were observed. Swelling and solubility patterns indicated lower relaxation temperature and higher swelling and solubilization rates in MFC flour compared with NFC flour. However, no significant differences were observed for solubility for both treatments at temperatures 60, 70, and 80 oC, respectively; although significant differences were observed at 90 oC, with values of microbial fermented flour having higher values than those of the natural fermented flour at both treatments. The pasting characteristics of 9% (db, dry basis) flour slurry of natural fermented cassava showed higher final viscosity, trough, and setback but lower breakdown ratios compared with flour of microbial fermented. This indicates that flour of natural fermented cassava paste might be better in withstanding processing conditions and would present a slightly superior thickening characteristic than flour of microbial fermented cassava paste. The differences in the viscoelastic properties and physico-functional characteristics of the natural and microbial fermented cassava flour could be used in their selection for specific food and industrial processing applications.