Pisamai Polthum and Araya Ahromrit

pp. 309 - 316

Abstract

Germinated seeds have a greater amount of the naturally-occurring γ-aminobutyric acid (GABA) which has many
health benefits. Further, colored seeds have higher antioxidant activity. Thai waxy corn is widely consumed after cooking,
due to its palatable glutinous texture. However, it is not commonly germinated before use. In this study, two varieties of Thai
waxy corn, KKU-KND (purple seed) and KKU-SLE (white seed), were germinated and converted to corn flour with the aim
of investigating the effect of germination on GABA content and antioxidant activity. Further, the microstructure of starch
granules was also examined. KKU-KND and KKU-SLE were grown and harvested in 2012. The seeds were soaked in distilled
water for 6 hrs to attain a moisture content of 31-32%wb and then germinated by employing two methods, i) in an open plastic
box, and ii) in a closed plastic box with a headspace of 3 cm for devoid oxygen (hypoxia method); the germination period
varied between 12-48 hrs at 35±2°C in both cases. The germinated samples were then dried at 50°C to a moisture content of
10±2%_wb. The results showed that non-germinated KKU-KND and KKU-SLE contained 2.68±0.77 and 1.58±0.05 mgGABA/
100gdb, respectively, whereas the samples germinated by the hypoxia method contained significantly higher GABA which
increased with germination time (p<0.05). The highest GABA contents found in KKU-KND and KKU-SLE were 37.20±3.27
and 54.47±2.08 mg/100g_db, respectively after 48 hrs of germination under the hypoxia method. In addition, the germinated
KKU-KND gave ABTS and DPPH values of 388.32±0.53 and 140.29±0.57 mgTrolox/100g_db, whereas the germinated KKU-SLE
gave ABTS and DPPH values of 183.69±1.75 and 38.43±1.64 mgTrolox/100g_db, respectively. The pictures of starch granules
obtained by means of SEM displayed differences in the shape and size of the non-germinated and germinated granules in
both verities. In conclusion, the hypoxia method is able to induce higher GABA in both waxy corns. Therefore, germinated
waxy corn can be a rich source of GABA and antioxidant activity.