Improvement in the<i>In Vivo</i>Digestibility of Rice Protein by Alkali Extraction Is Due to Structural Changes in Prolamin/Protein Body-I Particle

Kubota, Masatoshi; Saito, Yuhi; Masumura, Takehiro; Kumagai, Takehisa; Watanabe, Reiko; Fujimura, Shigefumi; Kadowaki, Motoni

doi:10.1271/bbb.90827

Cited by 44 publications

(38 citation statements)

References 16 publications

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“…The GI transit of rice in rats was monitored as reported previously (6). The GI tract contents were collected at 2 h after the start of feeding of the experimental diets (4 g).…”

Section: Inmentioning

confidence: 99%

“…SDS-PAGE and Western blotting (WB) analysis were performed as reported previously (6). The samples were suspended in a sample buffer (0.125 m Tris-HCl pH 6.8, 4% w/v SDS, 5% v/v 2-mercaptoethanol, 8 m urea, and 0.2 mg/mL bromophenol blue).…”

Section: Inmentioning

confidence: 99%

“…After blocking, the membranes were incubated for 1 h with antibodies against 23G (diluted with the blocking solution 1 : 20,000, v : v) or 13P (diluted 1 : 20,000, v : v) at room temperature (11). It was checked in the previous report that these antibodies used for WB analysis did not detect endogenous proteins in GI contents of rats (6). The membranes were then washed with TBS-T, incubated for 1 h with horseradish peroxidase-linked antirabbit IgG antibody (GE Healthcare UK Ltd., Little Chalfont, UK) at room temperature, washed again with TBS-T, and then developed using enhanced chemiluminescent detection (GE Healthcare UK Ltd.).…”

Section: Inmentioning

confidence: 99%

“…These results imply that prolamin is an indigestible protein. However, we recently reported that structural changes induced by alkali extraction can improve the in vivo digestibility of prolamin (5,6). A study by Eggum et al showed that cooking decreased the true protein digestibility (TD) of rice from 99.7 to 88.6% (7).…”

mentioning

confidence: 99%

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In Vivo Digestibility of Rice Prolamin/Protein Body-I Particle Is Decreased by Cooking

Kubota

Saito

Masumura

et al. 2014

J Nutr Sci Vitaminol

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Rice is a staple cereal and a major source of both protein and energy in most Asian countries. Thus, the true digestibility of cooked rice protein is very important for human nutrition. The proteins in rice endosperm consist mainly of storage proteins, e.g., glutelin, prolamin and globulin. Two major proteins, glutelin and prolamin, can be separated into several protein bands by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Glutelin separates into three bands: proglutelin (57 kDa), an acidic subunit (37-39 kDa), and a basic subunit (22-23 kDa) (1). Prolamin also separates into three bands: 16, 13 and 10 kDa prolamin (2). These storage proteins accumulate in organelles called protein bodies (PBs). Rice endosperm has two different types of PBs; prolamin accumulates in type-I protein bodies (PB-I), while glutelin and globulin accumulate in type-II protein bodies (PB-II) (3). Tanaka et al. (4) reported that fecal protein particles (FPP), such as PBs, were excreted in the feces of humans who had ingested cooked rice (CR). Ogawa et al. (2) demonstrated that the 13 kDa prolamin band in raw rice (RR) remained after pepsin digestion, although the glutelin subunit bands (37-39 and 22-23 kDa) disappeared. These results imply that prolamin is an indigestible protein. However, we recently reported that structural changes induced by alkali extraction can improve the in vivo digestibility of prolamin (5, 6). A study by Eggum et al. showed that cooking decreased the true protein digestibility (TD) of rice from 99.7 to 88.6% (7). However, no reports have directly demonstrated whether rice prolamin is rendered indigestible in vivo by cooking.In the present study, we monitored the gastrointestinal (GI) transit and fecal excretion of rice glutelin and prolamin in rats by using anti-23 kDa glutelin (23G) and anti-13 kDa prolamin (13P) antibodies to estimate their digestibility in CR and RR. Additionally, morphological observations of PBs in the feces of rats fed the CR or RR diets were conducted using electron microscopy to confirm the effects of cooking on PB structure. Although the digestibility of 23G was not affected by cooking, the digestibility of 13P was clearly reduced. Almost intact PB-Is were observed in the feces of rats fed the CR diet. Our results clearly indicate that rice prolamin is not indigestible in its raw form, but is rendered indigestible by cooking. Materials and MethodsMaterials and animal experiment. Rice (Koshihikari, 10% polished fraction) was purchased from Niigata Seifun Co., Ltd. (Tainai, Japan). RR flour was prepared using a jet mill (KV-3-4S, Yakushinkikai Seisakusho, Japan). CR flour was prepared by rinsing the rice first and then cooking it in twice its volume of water in an electric rice cooker (JAG-A100 TM, Tiger Co., Ltd., Osaka, Japan). Summary Rice has storage proteins, e.g., glutelin, globulin and prolamin, in the seeds, which are used as nitrogen sources during germination. Rice prolamin has been reported to be an indigestible protein that decreases the nutritional ...

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“…The GI transit of rice in rats was monitored as reported previously (6). The GI tract contents were collected at 2 h after the start of feeding of the experimental diets (4 g).…”

Section: Inmentioning

confidence: 99%

Section: Inmentioning

confidence: 99%

Section: Inmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

In Vivo Digestibility of Rice Prolamin/Protein Body-I Particle Is Decreased by Cooking

Kubota

Saito

Masumura

et al. 2014

J Nutr Sci Vitaminol

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“…Alkali treatment is considered to break some of the hydrogen, amide, and disulfide bonds in rice glutelin, leading to the reduction in molecular size of protein and the improvement in protein extraction (Hamada, 1997). Recently, it has been reported that this method improves in vitro and in vivo digestibility of rice protein, which is associated with the modification of protein body structure and amino acid composition (Kumaga et al, 2006;Kubota et al, 2010;Yang et al, 2012). Unfortunately, exposing protein to severe alkaline conditions may cause some undesirable side reactions, degradation of protein, and potential toxicity, such as lysinoalanine, resulting in the loss of nutritional value (Shewry and Miflin, 1985).…”

Section: Introductionmentioning

confidence: 99%

Characterization and In Vitro digestibility of rice protein prepared by enzyme-assisted microfluidization: Comparison to alkaline extraction

Xia

Wang

Gong

et al. 2012

Journal of Cereal Science

100

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Effect of domestic cooking on rice protein digestibility

Liu

Zheng

Chen

2019

Food Science & Nutrition

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The effects of washing, soaking, and common domestic cooking methods (normal cooking, high‐pressure cooking, and microwave cooking) on protein content, in vitro protein digestibility, and amino acid composition of japonica and indica rice were investigated. All processes in rice domestic cooking did not affect protein content. However, the gastric and gastrointestinal protein digestibilities decreased significantly after cooking. Protein solubility methods were used to observe the formation of disulfide bonds and hydrophobicity interactions after cooking. Disulfide bonds and hydrophobicity interactions were formed during cooking, and the cooking‐induced disulfide bond cross‐linking decreased the protein digestibility observably. Moreover, the solubility of 13 kDa prolamin subunit sharply decreased after cooking due to intramolecular disulfide bond cross‐linking. Therefore, cooking‐induced formation of intramolecular disulfide linkages might stabilize and strengthen the structure of protein body‐I, which exhibited strong resistance to proteases, particularly pepsin. Cooking had limited effect on amino acids.

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Improvement in theIn VivoDigestibility of Rice Protein by Alkali Extraction Is Due to Structural Changes in Prolamin/Protein Body-I Particle

Cited by 44 publications

References 16 publications

In Vivo Digestibility of Rice Prolamin/Protein Body-I Particle Is Decreased by Cooking

In Vivo Digestibility of Rice Prolamin/Protein Body-I Particle Is Decreased by Cooking

Characterization and In Vitro digestibility of rice protein prepared by enzyme-assisted microfluidization: Comparison to alkaline extraction

Effect of domestic cooking on rice protein digestibility

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