Carotenoids are secondary plant metabolites and contribute to the characteristic color of many foods. Isomerization of the conjugated double bond system can be induced by temperature, irradiation and chemicals. The present study successfully established an analytical HPLC-UV-method to differentiate field- and greenhouse-grown tomatoes and spinach based on changes in the isomeric profile. First, model systems with �-carotene and lycopene using a halogen lamp, whose wavelength spectrum was close to daylight, were investigated to simulate the influence of field-grown conditions on carotenoid isomerization. Different optical filters were interposed to mimic cultivation in greenhouses. Field-grown systems led to a preferential increase of 9-cis-carotene, while 13-cis-carotene was just formed at the beginning of irradiation. Additionally 9,13-di-cis-carotene decreased significantly. For lycopene systems energy-rich light led to preferential formation of 5-cis-lycopene, while 7-cis-lycopene decreased. For both carotenoids isomerization in greenhouse model systems led to a significantly different ratio. These results were then verified in biological tomato and spinach samples grown under authentic greenhouse vs. field conditions and in consumer available vegetables. Authentic field-grown spinach showed significant higher amounts of 9-cis- (7.52 � 0.14 %) and significant lower levels of 9,13-di-cis-isomer (0.25 � 0.03 %) compared to authentic greenhouse spinach (6.49 � 0.11 % and 0.76 � 0.05 %). Almost all customer available spinach samples (fresh and frozen) were identified as common field-grown cultivation. In addition, there was a clear-cut differentiation of frozen samples compared to fresh spinach, caused by significant higher levels of 13-cis- and 15-cis-carotene as a result of industrial blanching processes.

Growing and processing conditions of tomatoes and spinach can be differentiated by the carotenoid isomeric profile

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.