由新鮮龍眼榨汁製造濃縮龍眼汁 和龍眼粉之研究

Making of longan juice concentrate and browned powder from fresh longan puree

陳韋廷(Wei-Ting chen)

指導教授 ： 吳瑞碧

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02465

摘要

龍眼為本省夏季盛產的水果之一，其產期短、保鮮困難、不耐久藏與長期運輸，造成較大的產銷問題，因此本研究期以新製程及技術研發新型態龍眼加工製品，以提高其經濟效益並解決農民的問題。
本實驗分成兩部分，第一部分以龍眼為原料製成龍眼濃縮汁，在烘焙期間進行物化性質分析，並以固相微萃取法 (SPME) 分析烘焙期間龍眼果漿的揮發性成分變化。第二部份以噴霧乾燥之加工方式將烘焙龍眼果漿製成龍眼乾粉末，並探討其最適操作條件。
結果顯示，將新鮮龍眼去殼、打漿，以85℃熱風循環烘箱乾燥10小時，得水分約40%的烘焙龍眼果漿，再將其裝瓶密封繼續以85℃反應9小時，可製成香氣濃郁的龍眼濃縮汁。在揮發性成分分析方面，以PDMS/DVB 纖維在60℃下吸附龍眼果漿揮發性成分40分鐘，可以有效吸附果漿香氣化合物，經由GC/MS之分析得知，龍眼濃縮汁的主要香氣成分為trans-caryophyllene、trans-β-ocimene和α-gurjunene，其主要香氣成分與市售龍眼乾類似。將烘焙龍眼果漿與麥芽糊精混合均質，預熱至60℃後，以熱風溫度150℃進行噴霧乾燥試驗，並以二因子三階層之反應曲面法探討最適操作條件，經嗜好性品評和粉末產率評估，所得之龍眼乾粉末最適操作條件為:進料固形物22∼26%、麥芽糊精添加量58∼62%，此產品水分含量為3.65%、水活性0.22、假密度0.55 (g/ml)、色澤分析為L 值75.56、a 值1.6、b 值14.27。

關鍵字

龍眼果漿 ； 揮發性化合物 ； 固相微萃取 ； 噴霧乾燥 ； 反應曲面法

並列摘要

Longan is one of the most abundant summer fruits in Taiwan. It’s harvest period is short, thus cause problems in marketing. It is a good idea to increase the economic value of longan by developing new products.
The experiments can be divided into two parts. In the first part, the baked longan concentrate would be made from longan puree. The changes in quality and composition in baking would be analyzed. Volatile flavor compounds in the baked concentrate would be monitored using Solid-Phase Microextraction (SPME) and GC/MS. In the second part, the browned longan powder would be obtained by the spray draying of baked longan concentrate. The optimum conditions would be investigated.
Fresh longan fruit was shelled and blended to obtain the puree. The puree was dried in a hot air-recirculating oven at 85oC for 10 hr to obtain the baked longan concentrate at 40% moisture content. The concentrate was sealed in a bottle, heated in an oven at 85oC for 9 hr to develop the distinctive dried longan flavor. In the analysis of volatile compounds from the baked longan concentrate, PDMS/DVB fiber absorption was found to be suitable under the operating conditions of 60℃ for 40 minutes. The GC/MS results indicated that the main volatile compounds were trans-caryophyllene, trans-β-ocimene and α-gurjunene.
The baked longan concentrate was blended with maltodextrin, preheated to 60oC, and then spray-dried with 150oC incoming air. The optimum feeding conditions was investigated using response surface methodology (RSM) with two factors and three levels. After sensory analysis and yield assessment, the best feed was found to be 22-26% total solids baked concentrate added with 58-62% maltodextrin. The characteristics of the longan powder are: moisture content 3.65%, water activity 0.22, bulk density 0.55 g/ml, Hunter's L-value 75.56, a-value 1.6, and b-value 14.27.

並列關鍵字

longan puree ； volatile compound ； SPME ； spray drying ； RSM

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