短波紫外線照射誘導‘苗栗一號’桑椹白藜蘆醇累積與降低採後腐損

Ultraviolet-C Radiation Elicits trans-Resveratrol Accumulation and Reduces Postharvest Decay in 'Miaoli No.1' Mulberry Fruit

完熟‘苗栗一號’桑椹（Morus atropurpurea Roxb. ''''Miaoli No.1''''）貯藏前以2.40kJ．m^(-2)短波紫外線（UV-C）照射，於5℃貯藏4天後，其抗菌物質白藜蘆醇（trans-resveratrol, RSV）含量增加至2.83μg．G^(-1)DW，明顯高於對照組（2.21μg．G^(-1)DW），果實腐爛率也比對照組低，但對病徵嚴重度並無顯著之影響。貯藏8天後RSV濃度下降到與對照組相似，腐爛率隨之提高，但仍比對照組低。此UV-C照射對另一抗菌物質白藜蘆醇苷（trans-piceid, PIC）含量並無明顯提升效果。降低UV-C照射劑量至0.48 kJ．M^(-2)雖然失去RSV含量增加的作用，仍可降低貯藏4天的果實腐爛率，但貯藏8天腐爛率則提高至與對照組相同。二種UV-C照射劑量對貯藏於較高溫度（10℃）果實之腐爛率皆無抑制效果。此結果顯示，UV-C照射桑椹降低腐爛率可能與抗菌物質含量受到UV-C誘導提升有關，其效果受到照射劑量與照射後貯放溫度所影響。本試驗所建立的桑椹RSV與PIC固相萃取與高效能液相層析分析方法，理論板數（theoretical plates）為15687.5與46511.7，測定線性濃度1-10μg．Ml^(-1)（R^2=0.9959）與10-50μg．mL^(-1)（R^2=0.9989），指標成分與內標準品柚皮素（naringenin）的平均感應因子（response factor）與平均相對標準偏差（relative standard deviation, RSD）分別為5.08（RSD=9.04%）與3.99（RSD=5.80%），RSV與PIC標準品添加回收率為126.81%（RSD=11.93%）與83.57%（RSD=50.84%），具有良好的分離效果、回收率與再現性。 Ripe 'Miaoli No. 1' mulberries were irradiated with high (2.40 kJ．m^(-2)), low (2.40 kJ．m^(-2)), or zero (as control) dosage of ultraviolet-C (UV-C) and then stored at either 5℃ or 10℃ for 8 days. After 4 days at 5℃, high-dosage irradiated berries had higher phytoalexin trans-resveratrol (RSV) content (2.83μg．g^(-1) DW vs. 2.21μg．g^(-1) DW) and lower incidence of decay than the control, but the 2 groups had a similar decay severity index. After 8 days at 5℃, RSV content in high-dosage irradiated berries declined to the level of the control and spoilage of the berries increased although still lower than the control. Low-dosage irradiation did not enhance RSV content but lowered decay incidence up to 4 days although not to 8 days. The irradiation did not suppress decay of the berries stored at 10℃. The irradiation did not elicit accumulation of trans-piceid (PIC), another phytoalexin found in mulberries. The results suggested that UV-C irradiation could increase phytoalexin contents and therefore suppress pathological breakdown in mulberries. The efficacy of irradiation depended on the dosage and storage temperature, however. The methodology adopted in this study for extraction and HPLC analysis of RSV and PIC contents in mulberries was satisfactory. There was a good separation ability as well as a high recovery percentage and reproducibility, as revealed by theoretical plates 15687.5 and 46511.7, reliable linear range 1-10μg．mL^(-1) (R^2=0.9959) and 10-50μg．mL^(-1) (R^2=0.9989), the average response factor and relative standard deviation (RSD) to the internal control (naringenin) 5.08 (RSD=9.04%) and 3.99 (RSD=5.80%), and the recovery percentages of added RSV and PIC standard 126.81% (RSD=11.93%) and 83.57% (RSD=50.84%), respectively.