Off-odor of Strawberry by Freezing

Abstract

Deterioration of aroma of strawberry sometimes occurs immediately following freezing and develops during subsequent frozen storage. This paper reports the feature of this phenomena using 2 cultivars of ‘Donner’ and ‘Hoko-wase’. The berries were frozen and stored at -20°C. The off-odor was detected after 1 day of frozen storage by taste panel and strongest after 1 month storage in ‘Donner’, while ‘Hoko-wase’, the off-odor was not so notable as in ‘Donner’, showing the highest score after 1 week of frozen storage. Longer storage reduced both the off-odor and natural fragrance. Volatiles emanated from fresh and frozen-thawed strawberries were trapped and determined. Esters, dominant compounds in fresh berries, were hardly detected in frozen-thawed berries, while carbonyl compound(s) kept the same level with fresh berries. Fatty acid composition of neutral lipids and polar lipids extracted from frozen strawberries was quite similer to that of fresh berries. Evidence of lipid degradation causing an increase of free fatty acid was not obtained on thin layer chromatogram.
It is thus supposed that the off-odor in frozen strawberry may be a consequence of unbalance of volatiles revealing undesirable odor which is masked in fresh berries.