酵母抽提物（Yeast extract，YE）经60、480 Gy/min剂量率钴源和12000 Gy/min剂量率加速器辐照后，采用GC-MS测定挥发成分，并与五种目标氨基酸辐照挥发成分进行对比研究，探索酵母抽提物挥发物质的组成及氨基酸来源；通过ESR技术测定进一步分析自由基与剂量率的关系，研究剂量率对减少辐照损伤的作用和机理。结果表明，YE辐照挥发成分6种最主要的成分为丙酮、乙酸、二甲基二硫、甲苯、2, 6-二甲基吡嗪和苯甲醛，并且随照后时间的延长呈先增加后减少趋势；挥发成分由甲硫氨酸、丙氨酸和苯丙氨酸辐照降解生成；8 kGy相同剂量辐照，三种处理的YE挥发成分产生量：60 Gy/min>480 Gy/min>加速器。辐照YE自由基峰呈双连峰，峰型随剂量率和剂量的增加而变化；60 Gy/min钴源辐照时，自由基浓度（A）与吸收剂量（D）的关系为：；8 kGy相同剂量辐照，三种处理的YE自由基浓度：480 Gy/min<加速器<60 Gy/min。可见，高剂量率辐照可减少酵母抽提物自由基浓度，降低酵母抽提物辐解挥发成分的产生量。

Yeast extract (YE) was irradiated respectively by γ-rays with dosage rate of 60 and 480 Gy/min and electron beams of 12000 Gy/min. The volatile compounds from irradiated YE and five kinds of target amino acid-water solutions were detected by gas chromatograph- mass spectrometer-computer (GC-MS), the composition of YE volatile compounds and their amino acid source were investigated. The radical characteristics of irradiation YE were researched by electron sin resonance (ESR) and the mechanism of dosage rate on reducing irradiation damage was studied. Results showed that the six same volatile compounds from three irradiation treatments were acetone, acetic acid, methyl disulfide, toluene, 2,6-dimethyl-pyrazine and benzaldehyde. The number of volatile compounds and YE content increased during the first 14 days and then decreased during 14~35days after irradiation. The essential constitutes of amino acids were Met, Ala and Phe from YE degradation. The order of volatile content of YE with same absorbed dosage was: 60 Gy/min γ-rays＞480 Gy/min γ-rays＞electron beams. The ESR spectrum of YE was a double peak and the peak changed with dosage and dosage rate. YE irradiated by 60 Gy/min γ-rays was detected by ESR and showed that the ESR signal intensity was positively correlated with absorbed dosage and the linear fitting equation was: A=4363.5D+4873.9, R2=0.9826. The sequence of ESR signal intensity of YE with same absorbed dosage was: 480 Gy/min γ-rays < electron beams <60 Gy/min γ-rays. Therefore, high dosage rate irradiation can produce low radical intensity and reduce the volatile content production.

国家自然科学基金项目（11105048）；湖北省农产品辐照工程技术中心