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

Improper package design or temperature abuse during handling may cause frui ts and vegetables in modified-atmosphere (MA) packages to be exposed to low , injurious O-2 levels associated with the production of fermentation volat iles, quality loss and eventually product breakdown. A simple and reliable technique to detect low-O-2 injury in packaged products at an early stage w ould reduce the risk of supplying inferior or unsafe produce to the consume r. The formation of ethanol, a common product of fermentation, has been cor related with low-O-2 injury. A commercial ethanol biosensor, composed of a chromagen and immobilized enzymes: alcohol oxidase and peroxidase, and avai lable as a test strip, was tested for its suitability to detect low-O-2 inj ury indirectly. In the presence of ethanol, the chromagen was oxidized, res ulting in a color change from a dull white to a clear bluish-green. The bio sensor detected 10 mu l l(-1) (approximate to 1 Pa) ethanol in the gas phas e at 5 degrees C with a 15-s exposure. The human threshold for ethanol dete ction is 30 mu l l(-1) (approximate to 3 Pa). The color change of the biose nsor was closely correlated to ethanol partial pressure in MA package heads pace over cut lettuce, cut broccoli, cut cauliflower, shredded cabbage and cut carrots, and to that over prepared standard ethanol solutions. The stud y demonstrated that the biosensor can detect gas-phase ethanol quantitative ly and hence indirectly can detect low-O-2 injury in MA lightly processed c ut broccoli, cut cauliflower, cut lettuce and shredded cabbage packages. Th e biosensor detected ethanol in cut carrot packages prior to the establishm ent of low-O-2 conditions. This ethanol, also detected using gas chromatogr aphy, may have been produced as a wound response to cutting. (C) 1999 Elsev ier Science B.V. All rights reserved.