γ-聚谷氨酸钠对面包酵母的抗冻作用及其机理
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生物工程
食品科技
FOOD SCIENCE AND TECHNOLOGY 2012年 第 37卷 第 10期
γ-聚谷氨酸钠对面包酵母的 抗冻作用及其机理
时晓剑1，缪冶炼1*，卫 昊1，徐 虹1，王冀宁2 (1.南京工业大学食品与轻工学院，材料化学工程国家重点实验室，南京 211816； 2.南京工业大学经济管理学院，南京 211816)
·2·
食品科技
2012年 第 37卷 第 10期 FOOD SCIENCE AND TECHNOLOGY
生物工程
during frozen storage. Na-γ-PGA had greater antifreeze effect on the yeast cells than glutamic acid and glucose. It inhibited both the generation of big-size ice crystals during freezing and the recrystallization of ice crystals during freezing storage. Under the condition of a freezing rate at 0.27 ℃/min, a storage temperature at -30 ℃ and storage time at 6 d, the survival ratio of yeast cells was increased from 36.5% to 67.5% by adding 1% of Na-γ-PGA. Na-γ-PGA, glucose and glutamic acid had an antifreeze activity of 2.48, 2.03 and 1.42 respectively. The survival ratio of yeast cells (η, %) increased linearly with increasing antifreeze activity (Aa, -). The high antifreeze activity of Na-γ-PGA was resulted from its high dissociation Key words: bread; frozen dough; yeast; poly-γ-glutamic acid; antifreeze; unfrozen water degree and the high capability of Na+ to combine water molecules.
*通讯作者 收稿日期：2012-02-17 基金项目：国家重点基础研究发展计划(973项目，2009CB724700)；国家自然科学基金项目(71173103/G0310)；2011年江苏省高等学校大学 生实践创新训练计划项目。 作者简介：时晓剑(1988—)，男，江苏扬州人，硕士研究生，研究方向为食品微生物。
Abstract: Sodium poly-γ-glutamate (Na-γ-PGA), a water-soluble polyamide composed of poly-γglutamic acid and sodium ion, is edible, tasteless, colorless and odorless. It is considered as a potential cryoprotectant for backers’ yeast. In the present study, the antifreeze effect of Na-γ-PGA on bakers’ yeast cells was investigated in the freezing rate range of 0.03~0.40 ℃/min and the storage temperature range of -7~-60 ℃. The mechanism of the antifreeze effect was also discussed. The experimental results showed that the survival ratio of yeast cells decreased at the beginning, and was constant after 6 d
摘要 ：γ - 聚谷氨酸钠 ( γ -PGA 钠 ) 是由 γ - 聚谷氨酸无色无味。γ-PGA钠作为面包酵母抗冻剂，具有较强的实用性。在0.03～0.40 ℃/min的冷 冻速率、-7～-60 ℃的冻藏温度条件下，探讨了γ-PGA钠对面包酵母的抗冻作用及其机理。实 验结果表明，酵母细胞存活率在冻藏初期逐渐下降，6 d后趋于稳定 。γ-PGA钠对酵母的抗冻 作用明显高于葡萄糖和谷氨酸。γ-PGA钠抑制了冷冻和冷藏过程中大冰晶的产生、以及冰晶的 重结晶。在冷冻速率大于0.27 ℃/min、冻藏温度低于-30 ℃、冻藏时间6 d的条件下，添加1%的 γ-PGA钠使酵母细胞存活率从无γ-PGA钠时的36.5%上升到67.5%。γ-PGA钠、葡萄糖和谷氨 酸的抗冻活性分别为2.48、2.03和1.42。细胞存活率(η，%)随抗冻活性(Aa，-)的增加呈线性上 升。γ-PGA钠具有较大抗冻活性的机理是，γ-PGA钠的解离度较大，并且Na+能够固定较多的 水分子。 关键词：面包；冷冻面团；酵母；γ-聚谷氨酸钠；抗冻活性；非冻结水 中图分类号：TS 201.3 文献标志码：A 文章编号：1005-9989(2012)10-0002-05
Antifreeze effect and mechanism of sodium poly-γ-glutamate on backers’ yeast cells
SHI Xiao-jian1, MIAO Ye-lian1*, WEI Hao1, XU Hong1, WANG Ji-ning 2
(1.College of Food Science and Light Industrial Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 211816; 2.School of Economics & Management, Nanjing University of Technology, Nanjing 211816)
食品科技
FOOD SCIENCE AND TECHNOLOGY 2012年 第 37卷 第 10期
γ-聚谷氨酸钠对面包酵母的 抗冻作用及其机理
时晓剑1，缪冶炼1*，卫 昊1，徐 虹1，王冀宁2 (1.南京工业大学食品与轻工学院，材料化学工程国家重点实验室，南京 211816； 2.南京工业大学经济管理学院，南京 211816)
·2·
食品科技
2012年 第 37卷 第 10期 FOOD SCIENCE AND TECHNOLOGY
生物工程
during frozen storage. Na-γ-PGA had greater antifreeze effect on the yeast cells than glutamic acid and glucose. It inhibited both the generation of big-size ice crystals during freezing and the recrystallization of ice crystals during freezing storage. Under the condition of a freezing rate at 0.27 ℃/min, a storage temperature at -30 ℃ and storage time at 6 d, the survival ratio of yeast cells was increased from 36.5% to 67.5% by adding 1% of Na-γ-PGA. Na-γ-PGA, glucose and glutamic acid had an antifreeze activity of 2.48, 2.03 and 1.42 respectively. The survival ratio of yeast cells (η, %) increased linearly with increasing antifreeze activity (Aa, -). The high antifreeze activity of Na-γ-PGA was resulted from its high dissociation Key words: bread; frozen dough; yeast; poly-γ-glutamic acid; antifreeze; unfrozen water degree and the high capability of Na+ to combine water molecules.
*通讯作者 收稿日期：2012-02-17 基金项目：国家重点基础研究发展计划(973项目，2009CB724700)；国家自然科学基金项目(71173103/G0310)；2011年江苏省高等学校大学 生实践创新训练计划项目。 作者简介：时晓剑(1988—)，男，江苏扬州人，硕士研究生，研究方向为食品微生物。
Abstract: Sodium poly-γ-glutamate (Na-γ-PGA), a water-soluble polyamide composed of poly-γglutamic acid and sodium ion, is edible, tasteless, colorless and odorless. It is considered as a potential cryoprotectant for backers’ yeast. In the present study, the antifreeze effect of Na-γ-PGA on bakers’ yeast cells was investigated in the freezing rate range of 0.03~0.40 ℃/min and the storage temperature range of -7~-60 ℃. The mechanism of the antifreeze effect was also discussed. The experimental results showed that the survival ratio of yeast cells decreased at the beginning, and was constant after 6 d
摘要 ：γ - 聚谷氨酸钠 ( γ -PGA 钠 ) 是由 γ - 聚谷氨酸无色无味。γ-PGA钠作为面包酵母抗冻剂，具有较强的实用性。在0.03～0.40 ℃/min的冷 冻速率、-7～-60 ℃的冻藏温度条件下，探讨了γ-PGA钠对面包酵母的抗冻作用及其机理。实 验结果表明，酵母细胞存活率在冻藏初期逐渐下降，6 d后趋于稳定 。γ-PGA钠对酵母的抗冻 作用明显高于葡萄糖和谷氨酸。γ-PGA钠抑制了冷冻和冷藏过程中大冰晶的产生、以及冰晶的 重结晶。在冷冻速率大于0.27 ℃/min、冻藏温度低于-30 ℃、冻藏时间6 d的条件下，添加1%的 γ-PGA钠使酵母细胞存活率从无γ-PGA钠时的36.5%上升到67.5%。γ-PGA钠、葡萄糖和谷氨 酸的抗冻活性分别为2.48、2.03和1.42。细胞存活率(η，%)随抗冻活性(Aa，-)的增加呈线性上 升。γ-PGA钠具有较大抗冻活性的机理是，γ-PGA钠的解离度较大，并且Na+能够固定较多的 水分子。 关键词：面包；冷冻面团；酵母；γ-聚谷氨酸钠；抗冻活性；非冻结水 中图分类号：TS 201.3 文献标志码：A 文章编号：1005-9989(2012)10-0002-05
Antifreeze effect and mechanism of sodium poly-γ-glutamate on backers’ yeast cells
SHI Xiao-jian1, MIAO Ye-lian1*, WEI Hao1, XU Hong1, WANG Ji-ning 2
(1.College of Food Science and Light Industrial Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 211816; 2.School of Economics & Management, Nanjing University of Technology, Nanjing 211816)