| Summary: | 碩士 === 國立嘉義大學 === 食品科學系研究所 === 99 === Cyclea barbata Miers, a perennial woody climber plant, belongs to the famile of Menispermaceae. An edible gel is formed by rubbing the fresh leaves with cold tap water. While the moisture content was 72.14% in the fresh C. barbata leaves, the ash, crude protein, crude fat, crude fiber and carbohydrate accounted for 7.75%, 15.60%, 3.06%, 10.06% and 63.50% in the dry matter, respectively. The objective of this study was to investigate the effects of different processing methods (manual rubbing or mechanical blending), blanching temperature (50℃, 75℃, 100℃ for 30 seconds) and type of additive (sucrose, citric acid, calcium D-gluconate, and sucrose/citric acid) on mechanical properties, syneresis, color and pH value of C. barbata leaf gel during storage period (1, 3, 5, 7 days).
The hardness of C. barbata leaf gel prepared by manual rolling and mechanical blending was 417.5g and 611.8g, respectively. The mechanical blending process was not an ideal gel preparation method because the syneresis of the gel was 62.45% after stored for 3 days. While the gelation was not occurred when the blanching temperature was 100℃, the leaf gel could be formed when the leaves were blanched at 50℃. The mechanical properties of the gel from blanched leaves showed no significant difference when compared with the gel prepared from the leaves without heating.
As for the effects of different sucrose content (1%, 3%, 5%) on mechanical properties of the leaf gel prepared by manual rolling process, the highest hardness (436.4g) was detected in the gel containing 5% sucrose and the lowest hardness (201.9g) was found in the gel with 1% sucrose. For all types of the gel, the pH value decreased during storage. It is speculated that some acidic substances were formed during storage. For the gel containing 1%, 3%, 5% sucrose, the syneresis increased from 30.77%, 27.98%, 23.05% to 68.43%, 73.49%, 71.70%, respectively, during storage 1 to 7 days. The effects of citric acid at the levels of 0.05%, 0.1%, and 0.3% on the leaf gel were also tested. No gelation occurred when 0.3% citric acid was added. The lowest syneresis was obtained when citric acid was added in the levels of 0.05% and 0.1% (0.84% and 3.76%, respectively). The results indicated that citric acid could enhance the water holding capacity of the gel. The addition of 0.01%, 0.05% and 0.1% calcium D-gluconate could increase gel hardness to 430.6g, 709.0g, and 938.6g, respectively. However, the gel was graded as unacceptable in sensory evaluation. Moreover, severe syneresis was found for the gel containing calcium D-gluconate during storage. The syneresis of the gel increased from 35.21%, 38.44% and 37.52% to 69.50%, 69.18% and 69.50%, respectively, during storage from day 1 to day 7.
In order to improve the flavor and to reduce the syneresis of the gel based on sensory evaluation, use 1%, 3% and 5% sucrose in combination with 0.05% citric acid to prepare the leaf gel. The hardness of the gel was 447.3g, 419.7g and 410.6g, respectively. Analyses revealed a decrease in syneresis of the gel from 30.77% to 1.26%, 27.98% to 0.74% and 23.05% to 0.42%, respectively after stored 1 day. Then after stored 7 days, the syneresis of the gel were decreased from 68.43% to 40.80%, 73.49% to 39.94% and 71.70% to 39.27%, respectively. In conclusions, the addition of sucrose and citric acid could reduce the syneresis of Cylea barbata Miers leaf gel prepared by manual rubbing method during storage period. And the gel containing 5% sucrose＋0.05% citric acid had the highest sensory scores.
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