Evaluation of the Functional Properties and Granulization of Micronized Roselle Tea Residual Powder

Abstract

洛神葵呈鮮艷紅色，富含豐富營養成份、良好香氣及酸味，深受廣大消費者喜歡，常供飲料(品)、果醬、果凍及蜜餞製作。近年洛神葵機能成分—花青素及多酚化合物十分受到重視，成為保健、營養熱門之研究主題及素材，洛神葵茶製備萃取後之花萼渣，除供蜜餞製作外，使用及經濟效益有待提昇，如何多元化利用其天然膳食纖維及機能成分、特性成為重要及待深入研究之主題及技術。 本研究以乾燥洛神葵經水萃取後所剩餘之花萼渣，經熱風乾燥(hot dry；HD；55℃, 8hr)及冷凍乾燥(frezze dry；FD)處理，研磨微化後篩分為五種片段，取最小片段再經行星式球磨儀微化處理，觀察經不同微化處理洛神葵茶渣粉末之外觀結構並評估理化特性及機能性成分，取最適片段經不同時間浮動床造粒(fluid bed granulation)以提高產品應用性，並進行造粒效果評估。 實驗結果如下：乾燥洛神葵茶渣微化粉末含有豐富膳食纖維(約72.06-74.32 %)，可為一良好的膳食纖維來源；外觀觀察部分，經微化處理後最小片段有最強的結晶構造，色澤分析中L*值隨粒徑大小降低有逐漸上升趨勢，又以FD較HD為高，a*值則有相反之趨勢；不同大小片段之微化粉末其部分理化特性、體外機能性、總多酚及總花青素含量皆較未經分離組高，體積密度則較低，其中經HD處理陽離子交換力隨粒徑大小降低有顯著上升之情形，且與糖醛酸含量間具有相關性，而α-amylase活性抑制比及水溶性果膠質(water soluble pectin；WSP)皆與粒徑大小呈中度線性相關 (R2>0.7)，花青素組成經HPLC分析主要為delphinidin，cyanidin含量次之。經球磨微化處理之洛神葵茶渣微化粉末於球磨8小時出現聚集情形，粒徑大小有先上升後下降之現象；隨球磨時間增加，結晶構造有受到降解之現象，Chroma值則逐漸降低，球磨處理後葡萄糖結合力有明顯降低之情形，WSP含量隨研磨時間增加皆有逐漸上升之情形(R2>0.85)，總花青素含量經球磨後隨球磨時間增加則逐漸降低。經浮動床造粒後其粒徑大小明顯增加，膨潤力、還原力、類黃酮、總多酚及總花青素含量亦有上升之現象。

Roselle is bright red in color and contains abundant nutrients, excellent aroma and sourness and is widely preferred by consumers. It is often used in the manufacturing of drinks (products), jams, jellies and preserves. In recent years, much importance is given to the functional compounds—anthocyanin and polyphenol compounds—of Roselle and it has become a popular research topic and material for health and nutrition. Besides being used for making preserves, the economic efficiency of the calyx extracted from the Roselle tea still needs to be improved. Further studies are still needed for the important research and technology of using the natural dietary fiber and functional compositions and characteristics of Roselle in multiple ways.

This study uses the calyx residual of dry Roselle extracted by water. After hot air drying (HD, 55℃, 8 hr) and freeze drying (FD), micronized grinding was carried out and five fractions of the Roselle powder were sieved. The smallest fraction was selected and treated by planetary ball-mill micronization. The outer appearance and structures of different micronized Roselle residue were observed and the physicochemical properties and functional compositions were also estimated. Fluid bed granulation was carried out on the most appropriate fraction at different time periods, so as to enhance product usability as well as carry out the effective estimation of granulation.

The research results showed that dry Roselle tea residual powder contains abundant dietary fiber (72.06-74.32%), and can be used as an excellent source of dietary fiber. After micronization, the outer appearance of the smallest fraction showed the strongest crystalline structures. In the color analysis, there was a gradual increasing trend in the L* value along with a decrease in the particle size. There was a decreasing trend in the a* value when FD was higher than HD. Some of the physicochemical properties, external functions, total polyphenol and total anthocyanins of the micronized powder was higher than those in the non-separated group. However, the bulk density was lower. There was an apparent increase in the cation exchange capacity of the powder treated by HD along with a decrease in the particle size and was related to the uronic acid content. There was also a middle linear correlation between the inhibitory activity toward α-amylase and water soluble pectin (WSP) and particle size (R2>0.7). After HPLC analysis, the anthocyanin content mainly contained delphinidin, followed by cyanidin. Aggregation occurred after the micronized Roselle tea residual powder was treated by ball-mill micronization for 8 hours. There was first an increase followed by a decrease in the particle size. Degradation occurred in the crystalline structures when the ball-mill time was increased. There was a gradual decrease in the Chroma value. There was also an apparent decrease in the glucose binding ability after ball-mill treatment. A gradual increase in the WSP content occurred when the ball-mill time increased (R2>0.85). However, there was a gradual decrease in the total anthocyanin content along with an increase in the ball-mill time. The particle size apparently increased after fluid bed granulation. There was an increase in the swelling power, reducing power, flavonoids, total polyphenol and total anthocyanin contents after granulation.