Articles
PROBLEMS ASSOCIATED WITH THE ANALYSIS OF APPLE FRUIT
The analysis of apple fruit for nitrogen, phosphorus, potassium, magnesium and calcium is part of this service.
The development of standards for the chemical composition of apple fruit as an aid to prediction of storage potential took place in the early 70s.
The laboratory at Wye has had three seasons of apple fruit analysis on a fee-paying basis.
About 1000 fruit samples (30 000 fruit) are received over a period of five weeks.
The time taken from receipt of samples to the despatch of results is five days.
Each sample of fruit is cut into sections to remove seeds and stem.
The whole sample is chopped mechanically then a large sub sample, 300 g, is macerated with water to give a ratio of 1:1.5 apple pulp:water.
Two portions of the slurry are taken for analysis.
Nitrogen and phosphorus are determined colorimetrically in one portion after a Kjeldahl digest.
Nitrogen is determined using the indophenol blue reaction and phosphorus using the phosphovanadomolybdate complex.
The other portion is digested with a nitric-perchloric acid mixture for potassium, magnesium and calcium.
Potassium is determined by flame emission and magnesium and calcium by atomic absorption.
The problems discussed will be those created by analysing perishable samples at the limit of the laboratories analytical capacity and the specific analytical problems related to these five elements (their concentrations in apple fruit are atypical of most other plant materials) when they are included in an analysis system operating for a wide range of agricultural materials.