An examination of the volatile compounds present in cooked bramley's seedling apples and the changes they undergo on processing

Abstract

Abstract An efficient, yet relatively inexpensive combined gas chromatography‐mass spectrometry‐odour port unit has been used to follow the changes in the volatiles of cooking apples during cooking. Since headspace samples contained insufficient volatiles for mass spectrometric identification, they were isolated by a Likens and Nickerson extractor, the pentane extract being concentrated before examination. The volatiles were collected during successive intervals from the same cooking sample. Alcohols were prominent throughout the exaggerated cooking time of 6.5 h and were accompanied by varying amounts of hexanal, phenylacetaldehyde, damascenone and farnesenes. In the early stages, several esters were present in amounts sufficient for identification, but no evidence of their later evolution and of the accompanying apple odours was obtained. 2‐Furfural, benzaldehyde. 5‐methyl‐2‐furfural and 2,4‐decadienal were not detected initially, but contributed increasingly later, 2‐furfural finally becoming the predominant volatile. A taste panel established a highly significant difference between cooked apple prepared fresh from Bramley's stored at +5 °C for 5 months and blast‐frozen precooked apple, stored for 5 months at −20 °C and made originally from the same batch of Bramley's. The former was preferred as being less acid and having more apple flavour. Instrumental comparison of extracts prepared by the above methods showed that precooked frozen apple stored for only 1 week contains relatively higher concentrations of esters and of n ‐hexanal than after 5‐months' storage, when traces of the decadienal were found. The sensory and instrumental evaluations thus accord with one another.