Abstract
To study simultaneous water and solute transport kinetics during soaking in concentrated solution, the influence of the concentration and molecular weight of the solute(polyethylene glycol(PEG) and NaCl) in the soaking solution and the temperature on the water loss and solute gain rates were observed by using a model vegetable tissue(potato). When potato slices$(4cm{\times}4cm{\times}0.1cm)$ soaked in 60% PEG solutions, the water loss rate of the early phase decreased with increasing of the molecular weight of PEG from 200 to 6,000, while the final water loss increased with increasing the molecular weight of PEG and it reached to 80%. The cell wall of potato tissue was permeable to NaCl and PEGs of which average molecular weight is smaller than 400 but it was not permeable to PEG 600 and larger molecules. PEG which has average molecular weight below 600 induced plasmolysis and those above 600 induced cytorrhysis. The water loss rate of potato sample soaked in smaller molecular weight PEG solution was faster than those soaked in higher molecular weight PEG solution before cytorrhysis happened. The water loss rate was reversed after cytorrhysis happened. The volume change of potato within the first 60 minutes was larger in low molecular PEG solution but the final ratio of decreasing volume was larger in high molecular PEG solutions. In PEG 200 solution, the potato tissue was slightly shrinked without shape change. However, in PEG 4,000 solution, volume of potato was reduced significantly and potato tissue was twisted.
두께 1 mm의 감자 절편을 분자량 200에서 6000까지의 PEG용액에 침지했을 때 PEG의 분자량이 작을 수록 초기 탈수 속도가 빨랐으나 최종 탈수량은 PEG 분자량이 클수록 증가하여 PEG 6000인 경우 초기수분의 약 80%까지 탈수되었다. 감자절편을 저분자 용액인 NaCl, PEG400 용액에 침지한 경우, 조직의 뒤틀림 현상은 나타나지 않고 plasmolysis가 일어나면서 탈수와 부피가 감소되는 반면, PEG 600 용액에 침지시부터 조직의 뒤틀림 현상이 동반된 탈수 현상이 나타났으며, 고분자 용액인 PEG 4000 용액에 침지한 경우 cytonhysis 현상을 동반한 탈수와 부피 감소가 더욱 분명하게 관찰되었다. 초기 탈수 속도는 저분자 용액에 침지 시 더 빨랐으나 최종 탈수량은 고분자용액에 침지 시 더 컸으며 탈수량이 역전되는 시기는 cytorrhysis가 일어나는 시기와 일치하였다. 따라서 고분자 용질의 고농도 용액에 시료를 침지하면 용질의 함침량은 적게 하면서 탈수량을 증가시킬 수 있음을 알 수 있었다.
