Screening for GABA and glutamic acid in tomato and potato genotypes and effects of domestic cooking

& gamma;-Aminobutyric acid (GABA) and its precursor glutamic acid play signaling roles in both humans and plants. Interestingly, positive effects on human health are ascribed to GABA consumption, which is present at relatively high levels in various food products, including potato tubers and tomato fruits. However, the currently available information on GABA content in foods only partly represents market categories and lacks data on glutamic acid. Here, we performed a screening of 98 tomato and 72 potato genotypes for GABA and glutamic acid levels. Our results show a large variation in both GABA and glutamic acid across the various genotypes. The GABA and glutamic acid levels ranged from 72 to 1122 & mu;g/g fresh weight (FW), and 1160-6513 & mu;g/g FW, respectively in tomato, and were between 68 and 759 & mu;g/g FW and 409-874 & mu;g/g FW in potato. Differences between market categories were only present for glutamic acid. For both GABA and glutamic acid, losses occurred with cooking, depending on the preparation. GABA was less affected by cooking than glutamic acid. Potato and tomato could be major dietary GABA sources. Especially high-GABA genotypes merit further investigation because of their potential health effects.