PCP 1: Assessment of Protein Nutritional Quality: Digestibility and Bioavailability

S 105 AOCS ANNUAL MEETING & EXPO MAY 4–7, 2014 1 PCP 1: Assessment of Protein Nutritional Quality: Digestibility and Bioavailability Chairs: E. Krul, Solae LLC, USA; N. Deak, Solae LLC, USA; and J. Wanasundara, Agriculture & Agri-Food Canada, Canada Human Requirements for Protein and Amino Acids: How Much Do We Really Know? D.J. Millward, DJ Millward, Twickenham, Middlesex, UK. Although the assessment of protein nutritional quality can be done, at least in theory, with methods which measure its components directly, in practice quality is predicted as a function of its digestibility & indispensable amino acid (IAA) score. Scoring requires a reference IAA profile which in turn requires knowledge of both IAA & protein (PROT) requirements for the population of interest & the establishment of these values is inherently difficult. The currently accepted values were compiled from an extensive review by FAO/WHO (2007) & this report was only able to identify PROT & IAA requirements for healthy adults: i.e. maintenance requirements. For all other population groups these maintenance values were used in a factorial model of maintenance & growth to predict requirements. It is the case that none of the listed values for IAA & PROT requirements are entirely secure and in one case, i.e. pregnancy, the requirements may be unsafe. There is also considerable current debate about whether the current model based on minimal PROT & IAA requirements is appropriate & should be replaced with optimal requirements assumed by advocates to be higher values. This presentation will review the difficulties & uncertainties associated with the established human PROT & IAA requirements in the context of an adaptive metabolic demand nutritional model for dietary protein. The Evolution of Protein Quality Evaluation. G.J. Hughes, DuPont Nutrition & Health, St. Louis, MO, USA. It has long been recognized that both quantity and quality of dietary protein is important for human health. However, debate continues on the most appropriate way to assess protein quality for scientific as well as regulatory purposes. The Protein Efficiency Ratio (PER), a rat assay method, has been used for nearly 100 years. As more studies on human amino acid requirements and protein bioavailability became available, newer methods have been proposed. The Protein Digestibility-Corrected Amino Acid Score (PDCAAS), based on comparing the amino acid composition of a dietary protein to a reference amino acid profile and adjusting for protein digestibility, was introduced in 1991 and has been adopted by regulatory agencies globally. More recently, another method, the Digestible Indispensable Amino Acid Score (DIAAS) has been proposed, recommending different amino acid reference patterns and ileal digestibility to assess amino acid bioavailability. Another method under discussion is the Indicator Amino Acid Oxidation Method. These newer methods are not generally accepted and lack regulatory adoption. It is clear that researchers are seeking to improve protein quality assessment for human nutrition but it appears that more work needs to be done to determine the most biologically relevant, reproducible, and cost-effective method that can be widely implemented. Ileal Digestibility of Amino Acids Current Methodology and Possible Approaches to Standardization. H.H. Stein, University of IllinoisUrbana-Champaign, Urbana, IL, USA. Not all amino acids that are ingested are also absorbed and utilized by the body, but the quantities of absorbed amino acids may be estimated by determining the ileal digestibility of amino acids. However, ileal digestibility is usually not determined in humans, but the pig is recognized as an appropriate model for humans. Determining ileal digestibility of amino acids in diets or food ingredients fed to pigs involves the surgical installation of a cannula in the distal ileum of pigs, which allows for collection of digesta samples directly from the distal ileum. By subtracting the quantities of amino acids that are excreted in the intestinal fluids from the intake of amino acids, the apparent ileal digestibility is calculated. However, because the output of amino acids in the ileal fluids includes not only amino acids of dietary origin, but also amino acids of endogenous origin, a correction for the endogenous amino acids is needed and by doing so, values for the standardized ileal digestibility are calculated. These values are additive if different ingredients are mixed together and the digestibility of amino acids in the mixture may be calculated from the standardized ileal digestibility of amino acids in each ingredient. ABSTRACTS 105 AOCS ANNUAL MEETING & EXPO MAY 4–7, 2014S 105 AOCS ANNUAL MEETING & EXPO MAY 4–7, 2014 2 Protein Quality of Heat-processed Feed Ingredients and Its Effects on Swine Nutrition. F. Almeida and H.H. Stein, University of Illinois-Urbana-Champaign, Urbana, IL, USA. Plant proteins commonly used in swine diets are routinely heat-processed. The application of heat is unavoidable and necessary to deactivate antinutritional factors (e.g., trypsin inhibitors), as well as to aid in the desolventizing and drying processes. Heat-processing, however, must be carefully controlled because overheating may initiate Maillard reactions. During these reactions, which occur under proper moisture and temperature conditions, the amino group of an amino acid or protein reacts with the carbonyl group of a reducing sugar. Lysine is particularly susceptible to these reactions because of its exposed epsilon amino group. Amino acids participating in Maillard reactions may be destroyed or become biologically unavailable to pigs. Thus, the concentration and digestibility of amino acids in heat-damaged feed ingredients is reduced. Consequently, reduced protein utilization by pigs fed heat-damaged feed ingredients may result in decreased growth performance and increased N excretion, causing environmental concern. Therefore, rapid and reliable evaluation of the protein quality of heat-processed feed ingredients is necessary to minimize their detrimental effects and efficiently use them in swine