Making of longan juice concentrate and browned powder from fresh longan puree
Date Issued
2009
Date
2009
Author(s)
chen, Wei-Ting
Abstract
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.he 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.resh 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. he 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.
Subjects
longan puree
volatile compound
SPME
spray drying
RSM
Type
thesis
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