A Comparison of Protein Digestibility Corrected Amino Acid Score with Digestible Indispensable Amino Acid Score to Evaluate Protein Quality of Raw and Roasted Pistachio Nuts

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Abstract Objectives The objectives of this research were to determine the protein digestibility corrected amino acid score (PDCAAS) and the digestible indispensable amino acid score (DIAAS) for raw and roasted American pistachio nuts in growing pigs, and to assess the effect of roasting on these measures of protein quality. Methods Twelve ileal cannulated barrows (body weight: 60.9 ± 3.2 kg) were randomly allotted to a 2-period switch-back design with 3 diets and 4 replicate pigs per period. Roasted pistachio nuts and raw pistachio nuts (American cultivated pistachio nuts) were each added to a single diet as the only protein source, and the third diet was a nitrogen-free diet that was used to measure basal endogenous losses of AA. Experimental periods were 9 d with the initial 5 d for adaptation to the diets. On d 6 and 7, fecal samples were collected, and on d 8 and 9, ileal digesta samples were collected for 9 h each day. The PDCAAS and DIAAS were calculated according to the Food and Agriculture Organization. Results The standardized ileal digestibility (SID) of all indispensable AA, except Arg and Phe, was less (P < 0.05) in roasted than in raw pistachio nuts. Raw pistachio nuts had a PDCAAS of 73 and roasted pistachio nuts had a PDCAAS of 81, calculated for children 2 to 5 yr, and the first limiting AA when compared to human requirements was Thr for both pistachio nuts. The DIAAS calculated for children older than 3 years, adolescents, and adults was 86 and 83 for raw and roasted pistachio nuts, respectively. The limiting AA in both raw and roasted pistachio nuts that determined the DIAAS for this age group was Lys. Conclusions Results of this research illustrate that raw and roasted pistachio nuts can be considered a good quality protein source with DIAAS greater than 75, however, heating conditions associated with roasting may decrease the digestibility of AA in pistachio nuts. Funding Sources The U.S. Department of Agriculture's (USDA) Agricultural Marketing Service. Product was supplied by the American Pistachio Growers.