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Title:Digestible indispensable amino acid scores for food proteins
Author(s):Mathai, John Kolurathil
Director of Research:Stein, Hans H.
Doctoral Committee Chair(s):Pan, Yuan-Xiang
Doctoral Committee Member(s):Loor, Juan J.; Dilger, Ryan N.; Pettigrew, James E.
Department / Program:Nutritional Sciences
Discipline:Nutritional Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):protein quality
amino acids
Abstract:Three experiments were conducted to determine protein quality and to evaluate digestible indispensable amino acid scoring (DIAAS) methodology. Experiment 1 was conducted to compare protein digestibility corrected amino acid scores (PDCAAS) and DIAAS for various plant and animal proteins. Values for standardized total tract digestibility (STTD) of crude protein (CP) and standardized ileal digestibility (SID) of amino acids were calculated for whey protein isolate (WPI), whey protein concentrate (WPC), milk protein concentrate (MPC), skim milk powder (SMP), pea protein concentrate (PPC), soy protein isolate (SPI), soy flour, and whole grain wheat. The PDCAAS-like values were calculated using the STTD of CP to estimate amino acid digestibility and values for DIAAS were calculated from values for SID of amino acids. Results indicated that values for SID of most indispensable amino acids in WPI, WPC, and MPC were greater (P < 0.05) than for SMP, PPC, SPI, soy flour, and wheat. If the same scoring pattern for children between 6 and 36 months was used to calculate PDCAAS-like values and DIAAS, PDCAAS-like values were greater (P < 0.05) than DIAAS values for SMP, PPC, SPI, soy flour, and wheat indicating that PDCAAS-like values estimated in pigs may overestimate the quality of these proteins. Experiment 2 was conducted to determine the DIAAS values for pork loin and to evaluate the effect of roasting, frying, or grilling of pork loin on protein quality. The DIAAS were calculated based on ileal digestibility of amino acids in pigs for raw pork loin, roasted pork loin, grilled pork loin, fried pork loin, and casein. Six ileal-cannulated barrows were allotted to a 6 × 6 Latin square design with 6 diets and 6 periods during which ileal effluent samples were collected to determine amino acid digestibility. A N-free diet was formulated to determine basal endogenous losses of amino acids and crude protein (CP) and to enable the calculation of standardized ileal digestibility (SID) of amino acids. The remaining diets were formulated with each test ingredient as the sole source of amino acids. Using determined values for SID of amino acids for each ingredient and established reference protein patterns, DIAAS were calculated. For children from birth to 6 m, fried pork loin had the greatest (P < 0.05) DIAAS followed by grilled pork loin, roasted pork loin, raw pork loin, and casein. For children from 6 m to 3 y, DIAAS were greatest (P < 0.05) for grilled and fried pork loin and least (P < 0.05) for raw pork loin and the DIAAS of roasted pork loin was greater (P < 0.05) than that of casein. For DIAAS calculated for children older than 3 y, there were no differences in the DIAAS among grilled pork loin, fried pork loin, and casein, but these 3 ingredients had greater (P < 0.05) DIAAS than roasted pork loin, which in turn had a greater (P < 0.05) DIAAS than raw pork loin. Results indicate that prepared pork loins can be considered excellent protein sources based on their DIAAS and these data make it possible to calculate DIAAS for meals containing commonly consumed pork loin products. Additionally, results of this research indicate that even for high-quality proteins, such as pork loin, correct preparation can improve DIAAS. Experiment 3 was conducted to determine DIAAS values for 10 different foods known to have different protein values: wheat bread, whey protein isolate, zein, sorghum flour, bovine collagen, black beans, pigeon peas, chick peas, roasted peanuts, and Kellogg’s® All-Bran®. The second objective was to determine the variability among replications in the determination of the DIAAS values. Thirteen ileal-cannulated gilts were assigned to an incomplete 13 × 6 Latin square design with 13 diets and 6 periods. The 10 ingredients were used to formulate 10 different diets where each ingredient was the sole source of amino acids in the diet. Pigs on treatments 1 to 10 were fed the 10 diets containing the 10 food sources. Pigs on treatments 11, 12, and 13 were fed the whey protein isolate diet, the sorghum diet, and the pigeon pea diet, respectively. These extra replications enabled determination of intra-experiment variability. The SID for total amino acids was greater (P < 0.05) in toasted wheat bread and sorghum flour than in all other proteins except for chickpeas. The SID for mean indispensable amino acids, mean dispensable amino acids and total amino acids was lower (P < 0.05) in All-Bran® than in all other proteins except roasted peanuts. The DIAAS was 0 for zein, bovine collagen, roasted peanuts, and All-Bran® for all reference ratios. Whey protein isolate had the greatest (P < 0.05) DIAAS for infants, followed by chickpeas, pigeon peas, sorghum flour, black beans, and toasted wheat bread, in descending order. Whey protein isolate had the greatest (P < 0.05) DIAAS for children (6 m to 3 y) followed by chick peas and pigeon peas. Black beans and sorghum flour had DIAAS values that were not different, but these values were greater (P < 0.05) than the DIAAS for toasted wheat bread. Whey protein isolate had the greatest (P < 0.05) DIAAS for older children (3 y and older), followed by chickpeas. Pigeon peas had a greater (P < 0.05) DIAAS than sorghum flour, which in turn had a greater (P < 0.05) DIAAS than black beans, and black beans had a greater (P < 0.05) DIAAS than toasted wheat bread. For DIAAS calculated for all 3 reference ratios, there were no differences between replications for whey protein isolate, sorghum, or pigeon peas. The DIAAS values determined in this experiment indicate that most legumes and cereal grain products tested in this experiment are not adequate as the sole sources of protein for humans. Results of this experiment demonstrate that the pig model is a consistent model for determination of amino acid digestibility and DIAAS determination even when disparate protein sources are used.
Issue Date:2018-09-21
Rights Information:Copyright 2018 John Kolurathil Mathai
Date Available in IDEALS:2019-02-07
Date Deposited:2018-12

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