Superiority of alkali-extracted rice protein in bioavailability to starch degraded rice protein comes from digestion of prolamin in growing rats.
The rice protein prepared from alkaline extraction (AE-RP) has high digestibility compared to that obtained from starch degradation (SD-RP) in in vitro digestion experiments, and alterations in the protein body (PB) structures were observed in AE-RP in the previous study. The improvement in the digestibility of AE-RP is probably a result of the structural change of PB. The present study was carried out to elucidate the superiority of AE-RP compared to SD-RP in bioavailability in growing rats. There were no major differences between AE-RP and SD-RP in polypeptide compositions according to SDS-PAGE and their amino acid compositions. The equivalent body weight gain and similar growth curves in both AE-RP and casein (control) groups were obtained during the feeding period of 28 d, and their values were significantly higher compared to the SD-RP group (p<0.05). The protein efficiency ratio (PER) of the SD-RP (1.73) group was significantly lower than those of the AE-RP (1.87) and casein (1.84) groups (p<0.05). The plasma lysine concentrations at the last stage of the feeding period in the AE-RP and SD-RP groups were approximate levels and were appreciably lower, compared to that of the casein group (p<0.001). Portal plasma amino acid concentrations were determined after single administration (4 g/kg) of two rice proteins in non-anaesthetized rats. All the amino acid concentrations in the 2 groups reached a maximum level at 30 min or 1 h and decreased to the pre-administration levels 6 h after the start of administration. The total amounts of three amino acids, leucine, valine and arginine, which appeared in the portal blood during the 6 h period after the start of administration of AE-RP, were higher than those of SD-RP (p<0.05). Furthermore, 13 kDa prolamin was detected with Western-blot analysis only in the feces of rats fed SD-RP. Consequently, these results indicate that the bioavailability of rice protein containing prolamin was improved by alkaline extraction.
Kumagai
Takehisa
T
Kameda Seika Co., Ltd., Niigata, Japan. t_kumagai@kameda.co.jp
Watanabe
Reiko
R
Saito
Mariko
M
Watanabe
Toshiyuki
T
Kubota
Masatoshi
M
Kadowaki
Motoni
M
D000468:Alkalies; D000596:Amino Acids / Q000097:blood*; D000818:Animals; D001682:Biological Availability; D001835:Body Weight; D002364:Caseins / Q000493:pharmacokinetics; D004044:Dietary Proteins / Q000493:pharmacokinetics*; D004063:Digestion; D005243:Feces / Q000737:chemistry; D006128:Growth / Q000187:drug effects; D008239:Lysine / Q000097:blood; D008297:Male; D009753:Nutritive Value; D012275:Oryza; D010455:Peptides / Q000097:blood*; D055315:Prolamins / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013213:Starch; D015430:Weight Gain
D000468:Alkalies; D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D010455:Peptides; D055315:Prolamins; D013213:Starch; D008239:Lysine