An ethanol biosensor can detect low-oxygen injury in modified atmosphere packages of fresh-cut produce

Abstract

Abstract Improper package design or temperature abuse during handling may cause fruits and vegetables in modified-atmosphere (MA) packages to be exposed to low, injurious O 2 levels associated with the production of fermentation volatiles, quality loss and eventually product breakdown. A simple and reliable technique to detect low-O 2 injury in packaged products at an early stage would reduce the risk of supplying inferior or unsafe produce to the consumer. The formation of ethanol, a common product of fermentation, has been correlated with low-O 2 injury. A commercial ethanol biosensor, composed of a chromagen and immobilized enzymes: alcohol oxidase and peroxidase, and available as a test strip, was tested for its suitability to detect low-O 2 injury indirectly. In the presence of ethanol, the chromagen was oxidized, resulting in a color change from a dull white to a clear bluish-green. The biosensor detected 10 μl l −1 (≈1 Pa) ethanol in the gas phase at 5°C with a 15-s exposure. The human threshold for ethanol detection is 30 μl l −1 (≈3 Pa). The color change of the biosensor was closely correlated to ethanol partial pressure in MA package headspace over cut lettuce, cut broccoli, cut cauliflower, shredded cabbage and cut carrots, and to that over prepared standard ethanol solutions. The study demonstrated that the biosensor can detect gas-phase ethanol quantitatively and hence indirectly can detect low-O 2 injury in MA lightly processed cut broccoli, cut cauliflower, cut lettuce and shredded cabbage packages. The biosensor detected ethanol in cut carrot packages prior to the establishment of low-O 2 conditions. This ethanol, also detected using gas chromatography, may have been produced as a wound response to cutting.