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OPTIMISATION OF GERMINATION TEMPERATURE AND
TIME TO IMPROVE γ-AMINOBUTYRIC ACID, POLYPHENOLS
AND ANTIOXIDANT ACTIVITY IN BROWN RICE
Patricio Cáceres-Costales1, Cristina Martínez-Villaluenga2, Lourdes Amigo3, Juana Frias2
1Escuela
Superior Politecnica del Litoral (ESPOL), Guayaquil, Ecuador
2Institute of Food Science Technology and Nutrition (ICTAN-CSIC), Madrid, Spain
3Institute of Food Science Research (CIAL-CSIC/UAM), Madrid, Spain
INTRODUCTION
Rice (Oryza sativa L.) is a staple food for over half of the world's population. From a nutritional point of view, brown rice is
preferred since contains higher dietary fiber, B-vitamins and minerals than white rice as well as healthy phytochemicals such as γoryzanol, γ-aminobutyric acid (GABA) and polyphenols1. Germination is an effective and cheap process that improves not only the
nutritional quality of cereals but also GABA, polyphenols and antioxidant activity are accumulated in sprouts2. During germination,
the synthesis and accumulation of phytochemicals are highly affected by operating parameters such as time and temperature.
OBJECTIVE
This research was aimed to maximise antioxidant activity (ORAC), total phenolic compounds (TPC) and GABA optimizing
temperature and time during the germination of two varieties of brown rice using the response surface methodology (RSM).
MATERIAL AND METHODS
Long-grain brown rice varieties 15 and 17 were provided by the National Institute of Agricultural Research from Ecuador -INIAP-.
GABA content was determined by HPLC and confirmed by HPLC-MS3.
Total phenolic compound content (TPC) was determined by the Folin-Ciocalteau4.
Antioxidant capacity was evaluated by the oxygen radical absorbance capacity method (ORAC)5.
Response surface methodology (RSM) was constructed using Statgraphic 5.0 program for Windows.
RESULTS
RSM diagrams for GABA (mg/ 100g dm), antioxidant activity (ORAC,
µmol Trolox Equiv/g dm) and total phenolic compounds (TPC, mg
GAE/g dm) of brown rice varieties germinated at different conditions.
Variety 15
Variety 17
 RSM plots showed that germination time and temperature
influenced GABA, TPC and ORAC (P<0.05).
 Higher germination time conducted to larger GABA content
and slight differences between varieties were found (Figure 1).
 Lower temperature and longer germination time brought
about the highest TPC; and significant differences between
varieties were found. (Figure 2).
GABA
 Higher temperature throughout germination time let to larger
antioxidant activity and sharp differences between varieties
were found (Figure 3).
 Germination of variety 15 led to larger bioactive compound
retention than variety 17.
CONCLUSIONS
TPC
 Germination of brown rice variety 15 should be selected
for germination at 28 ºC for 96 h to achieve the optimum
GABA, TPC and antioxidant activity.
 The RSM proved to be useful for optimization of
germination process.
ORAC
REFERENCES
1
Min B, Gu L, McClung AM, Berman CJ, Chen ML (2012) Food Chem 133, 715-722.
2 Kim H-Y, Hwang IG, Kim TM, Woo KS, et al. (2012) Food Chem 134, 288-293.
3 Torino MI, limon, RI, Martinez-Villaluenga, C., Mäkinen et al. (2013). Food Chem 136: 1030-1037.
4 Singleton VL, Orthofer R, Lamuela-Raventos RM. (1999). Methods of Enzymology, 299, 152–178.
5 Martinez-Villaluenga C, Peñas E, Sidro B, Frias J, Vidal-Valverde C. (2012) LWT - Food Sci.
Technol. 2012, 46: 77-83.