Increased γ-Aminobutyric Acid Content of Germinated Brown Rice Produced in Membrane Reactor

Research background. Rice germination is a natural approach to enhance the physical and functional properties of brown rice. Thus, the aim of this study is to investigate the influence of different germination methods on functional properties of germinated brown rice and evaluate the process feasibility. Experimental approach. Brown rice of IPB 3S variety was germinated with three different methods: (i) complete soaking without water replacement, (ii) complete soaking with water replacement every six hours, and (iii) complete soaking with continuous washing in the developed membrane-facilitated soaking reactor. Results and conclusions. The application of the membrane reactor for producing germinated brown rice maintained the pH of the soaking solution relatively constant (i.e. 6.8-7.0). This indicated the circumvention of natural fermentation during brown rice germination. Moreover, the mass fraction of γ-aminobutyric acid in germinated brown rice produced in the membrane reactor was about 4.5-fold higher (169.2 mg/100 mg) than in ungerminated brown rice (36.82 mg/100 mg), and also higher than that of the other two soaking methods. The γ-oryzanol mass fractions and the antioxidant capacity expressed as ascorbic acid equivalents of germinated brown rice obtained with the three soaking methods varied from 32 to 38 mg/100 mg and 18 to 28 mg/100 g, respectively. Within this study, germination could also slightly reduce the transition temperatures of germinated brown rice starch gelatinization (to=73-74 °C, tp=76-77 °C and tc=~80 °C, where to, tp and tc are onset, peak and conclusion (final) temperatures). In conclusion, the production of germinated brown rice in the membrane reactor could enhance its γ-aminobutyric acid mass fraction and reduce wastewater production and is therefore considered more feasible. Novelty and scientific contribution. This study demonstrates the feasibility of germinated brown rice production using a membrane-facilitated soaking reactor with enhancement of bioactive compound content, especially γ-aminobutyric acid, and minimised wastewater production.
Pozadina istraživanja. Klijanje riže je prirodni postupak kojim se nastoje poboljšati fizikalna i funkcionalna svojstva smeđe riže. Stoga je svrha ovoga rada bila ispitati utjecaj različitih metoda klijanja na funkcionalna svojstva smeđe riže, te procijeniti isplativost postupaka. Eksperimentalni pristup. Smeđa riža sorte IPB 3S podvrgnuta je trima metodama klijanja: (i) namakanju bez promjene vode, (ii) namakanju s promjenom vode svakih šest sati, i (iii) namakanju s kontinuiranim ispiranjem u membranskom reaktoru. Rezultati i zaključci. U membranskom reaktoru za proizvodnju proklijale smeđe riže pH-vrijednost otopine za namakanje održavana je relativno konstantnom (pH=6,8-7,0), što je poslužilo kao zamjena za prirodni postupak fermentacije tijekom klijanja riže. Osim toga, maseni je udjel γ-aminomaslačne kiseline u smeđoj riži proklijaloj u membranskom reaktoru bio oko 4,5 puta veći (169,2 mg/100 mg) nego u neproklijaloj smeđoj riži (36,82 mg/100 mg), te veći nego u druga dva postupka klijanja. Maseni udjel γ-orizanola u proklijaloj smeđoj riži varirao je nakon triju primjenjenih metoda između 32 i 38 mg/100 mg, a njezin antioksidacijski potencijal, izražen u ekvivalentima askorbinske kiseline, bio je između 18 i 28 mg/100 g. U ovom je radu klijanjem smanjena temperatura staklastog prijelaza želatinizacije škroba smeđe riže (početna temperatura to=73–74 °C, najviša temperatura tp=76–77 °C i temperatura na kraju postupka tc=~80 °C). Možemo zaključiti da se klijanjem smeđe riže u membranskom reaktoru može povećati maseni udjel γ-aminomaslačne kiseline i smanjiti količina otpadne vode, zbog čega se smatra boljom metodom od ostale dvije. Novina i znanstveni doprinos. U ovom je radu prikazana mogućnost proizvodnje proklijale smeđe riže u membranskom reaktoru, pri čemu se namakanjem povećao udjel bioaktivnih spojeva, naročito γ-aminomaslačne kiseline, te smanjila količina otpadne vode.