Improving nutritional quality of unripe tomato through fermentation by a consortium of yeast and lactic acid bacteria

BACKGROUND Portugal is one of the main producers of industrial tomato and tomato paste, an important intermediate ingredient used in many added-value foods. The tomato processing industry rigorously selects the fruits by colour during mechanical harvest, picking only completely ripe fruits to produce high quality tomato paste. The latest available data shows that about 1.12 x 10(8) kg yr(-1) of non-red/not-ripe tomatoes are left in the field, representing a major side product/field residue with great impact on the environment and for tomato producers. RESULTS The aim of the work was to use fermentation by a consortium of yeast and lactic acid bacteria to improve the nutritional quality of unripe tomato paste. A consortium of Lactobacillus plantarum, Leuconostoc mesenteroides and Kluyveromyces marxianus was selected, producing an acidic paste with olive-like flavours after 4 days of fermentation. Nutritional characterization revealed a significant improvement (P < 0.05) in the content of ascorbic acid and antioxidant potential. In addition, ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis showed that the fermented green tomato paste content in glycoalkaloid alpha-tomatine represents no hazard to the consumer. CONCLUSION Therefore, the obtained fermented green tomato paste can be further used to produce new food products, such as salad dressings and sauces. (c) 2021 Society of Chemical Industry.