Rapid concurrent analysis of fruit sugars and acids by gas‐liquid chromatography

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Abstract
A rapid and simple procedure for the separation, identification and quantitative analysis of common fruit sugars and non‐volatile organic acids has been developed. Acids were precipitated as their lead salts from fruit ethanolic extracts and the sugars in the remaining supernatant and washings were partitioned into aqueous methanol. These preparations with internal standards were dried and converted to their trimethylsilyl derivatives for analysis by gas‐liquid chromatography. In model studies, conditions which permitted full recovery of sugars from the lead salts of acids, while minimising the loss of acids, were investigated. For fruit acids reported present in measurable amounts (10 mg/100 g of fruit), replicate analysis of aliquots from the same extract was within ±5% for malonic, phosphoric, succinic, malic, citric, ascorbic and galacturonic acids and within ±12% for quinic acid. The use of the method, its advantages and limitations, in determining individual and total sugars and acids is illustrated on some New Zealand grown fruit (New Zealand grapefruit, mountain pawpaw, tangelo, apricot). Total sugars and total acids determined by this procedure gave comparable results with those obtained by using standard A.O.A.C. procedures.

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