Hamoudi Latifa, Goulet Jacques, Ratti Cristina
Dépt. des sols et de génie agroalimentaire, Univ. Laval, Pavillon Comtois, FSAA, Ste-Foy, QC G1K 7P4, Canada.
J Food Sci. 2007 Mar;72(2):M45-9. doi: 10.1111/j.1750-3841.2006.00250.x.
The effect of 3 cryoprotective agents (trehalose, sucrose, and maltose) on the survival of concentrated cultures of Geotrichum candidum was studied. Initially, the effect of the carbohydrates at 9% and 23% concentrations or combined with skim milk (16%) was compared to the control (skim milk alone) immediately after freeze-drying. Two freeze-drying shelf temperatures, 25 degrees C and 35 degrees C, were investigated. Afterwards, the survival of G. candidum freeze-dried with carbohydrates at 23% concentration (alone or combined with skim milk 16%) was studied during 12 wk of storage at 4 degrees C, in the darkness, under vacuum, and at 0% relative humidity. The glass transition temperature (T(g)) of the dehydrated protective agents was measured by differential scanning calorimetry. The results showed that the survival after freeze-drying was proportional to the concentration of the protective agents, with skim milk alone giving poor survival of G. candidum. However, when skim milk was combined with disaccharides, a clear improvement was noted. No general tendency of shelf temperature on the survival of G. candidum was noted immediately after freeze-drying. However, changes in the viability were observed during storage. Glass transition temperature (T(g)) of protective agents linked to their moisture may contribute to predict the stability of lyophilized G. candidum during freeze-drying and storage.
研究了3种冷冻保护剂（海藻糖、蔗糖和麦芽糖）对白地霉浓缩培养物存活率的影响。最初，将9%和23%浓度的碳水化合物或与脱脂乳（16%）组合后的效果与冻干后立即的对照（仅脱脂乳）进行比较。研究了两种冻干搁板温度，25℃和35℃。之后，研究了在4℃、黑暗、真空和0%相对湿度条件下储存12周期间，用23%浓度的碳水化合物（单独或与16%脱脂乳组合）冻干的白地霉的存活率。通过差示扫描量热法测量脱水保护剂的玻璃化转变温度（T(g)）。结果表明，冻干后的存活率与保护剂的浓度成正比，仅脱脂乳时白地霉的存活率较低。然而，当脱脂乳与二糖组合时，存活率有明显提高。冻干后立即未发现搁板温度对白地霉存活率有一般趋势影响。然而，在储存期间观察到了活力的变化。与水分相关的保护剂的玻璃化转变温度（T(g)）可能有助于预测冻干和储存期间冻干白地霉的稳定性。
