บทคัดย่องานวิจัย

หมวดหมู่ : ฐานข้อมูลงานวิจัย

Binding of calcium by cell walls and estimation of calcium in apple fruit tissue with an ion selective electrode

Michael Knee and Pawan Srivastava

Postharvest Biology and Technology Vol: 5 Issue: 1-2 Pages: 19-27

1995

บทคัดย่อ

Binding of calcium by cell walls and estimation of calcium in apple fruit tissue with an ion selective electrode

Calcium is a critical nutrient for postharvest handling and quality of apples. Difficulties of analysis by atomic absorption spectrophotometry (AAS) prompted an examination of the use of a "standard addition" procedure with an ion selective electrode (ISE) to estimate calcium in apple tissue after homogenization in water. Calcium could be reliably estimated in synthetic mixtures, containing potassium malate at pH values representative of apple tissue homogenates. However, ISE estimates of calcium in apple homogenates were consistently lower than AAS estimates. The error in ISE estimates was attributed to cell wall binding of calcium. Titration of isolated apple cell walls with calcium showed that the proportion of calcium bound was dependent on the free calcium concentration. An empirical relationship between the reciprocal of the square of bound calcium and the reciprocal of free calcium concentration was derived. Incorporating this relationship into the calculation of calcium in apple homogenates led to closer agreement between ISE and AAS analyses than with the uncorrected calculation.