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This study evaluated the biological properties of peptides from brown rice protein hydrolyzed by bromelain (eb‐RPH) in relation to flavor characteristic. The fractionation into peptides < 1 kDa was observed to improve the DPPH, ABTS, and hydroxyl radical‐scavenging activities (0.19, 2.28, and 24.64 mM Trolox, respectively), angiotensin‐converting enzyme (ACE)‐inhibitory activity (IC50 value of 0.20 ± 0.011 mg protein/mL), as well as bitter and umami tastes. The < 1 kDa fraction was further analyzed by liquid chromatography‐electrospray ionization/mass spectrometry to identify amino acid sequence associated with biological activities and flavor characteristics. Eight peptides were identified. Most of the identified peptides contained features of previously reported ACE inhibitory and antioxidant peptides, especially peptide FGGSGGPGG and FGGGGAGAGG. Evaluation of flavor characteristics using BIOPEP database demonstrated that they had high occurrence frequencies of umami peptides (ESDVVSDL, GSGVGGAK, and SSVGGGSAG) and low Q‐value (938.75 to 282.22), suggesting that these peptides may be used as a fortifying health ingredient with good taste. Practical Application The fractionated brown rice protein hydrolysate (< 1 kDa) has the potential to serve as a functional food ingredient in nutraceutical food and beverage products that can provide health benefits with good taste. Information on amino acid composition and spatial conformation of peptide may aid us to better understand the molecular mechanisms involved in bioactivities and flavor of brown rice peptide for industrial applications.

Brown rice, which is a less allergenic food grain and contains essential amino acids, was hydrolysed by bromelain and PROTEASE FP51® to improve its functionalities and taste for food applications. The hydrolysate prepared by bromelain (eb-RPH) had high protein solubility, surface hydrophobicity, low molecular weight peptides, hydrophobic amino acids (leucine, valine and glycine) and flavor amino acids (glutamic acid and aspartic acid). The eb-RPH exhibited higher 1,1-diphenyl-2-picrylhydrazyl (DPPH˙) and 2,2'-azino-bis 3-ethylbenzthiazoline-6-sulfonic (ABTS˙(+)) radical-scavenging activities of 76.62% and 52.96%, respectively, and possessed a better foaming capacity (221.76%) and emulsifying capacity (32.34%) than the hydrolysate prepared by PROTEASE FP51® (ep-RPH) did. The eb-RPH gave the desired taste, which is attributed to volatile flavor compounds (benzaldehyde, benzeneacetaldehyde and 2-acetyl-1-pyrroline) and non-volatile flavor compounds, such as monosodium glutamate, 5'-guanosine monophosphate and 5'-inosine monophosphate (0.07, 0.03 and 0.05 mg mL(-1), respectively). Brown rice peptides generated by bromelain were novel bioactive peptides with multifunctional properties.

In this study, proteins from Thai brown rice (Khao Dawk Mali 105) were separated into albumin (2.18 %), globulin (3.98 %), glutelin (84.23 %), and prolamin (9.61 %) fractions, and were hydrolysed with various bromelain concentrations and hydrolysis times. Liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI-MS/MS) was conducted to assess the composition, molecular weight (MW) distribution, and sequence of the resulting peptides, and showed that most peptides have a MW below 2000 Da (60–70 %). Glutelin fraction hydrolysates exhibited the highest 2,2'-azino-bis 3-ethylbenzthiazoline-6-sulfonic (ABTS•+) radical-scavenging (0.69 ± 0.04 µM trolox) and copper chelating (4.12 ± 0.01 mg ethylenediaminetetraacetic acid; EDTA) activities, which was further fractionated into six fractions using reversed-phase high-performance liquid chromatography. The fourth fraction showed the highest ABTS•+ scavenging (1.08 ± 0.03 mM trolox) and copper chelating (5.00 ± 0.02 mg EDTA) activity. LC-MS/MS analysis revealed that the peptides with MW less than 1500 Da and hydrophobic or aromatic N-terminal residues, such as SPFWNINAHS, MPVDVIANAYR, VVYFDQTQAQA, and VEVGGGARAP, possibly contributed to the highest antioxidant activity in fourth fraction.

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