The amino acid compositions of the lentil samples were used to estimate the Amino Acid Score (AAS) as [mg of amino acid in 1 g of test protein/mg of amino acid in requirement pattern]×100 (FAO/WHO, 1991). Different age-categories scoring patterns were used: (a) pre-school children (2 to 5 years) (FAO/WHO, 1991); (b) infants (birth to 6 months), (c) young children (6 months to 3 years), and (d) older children, adolescents, and adults (FAO/WHO, 2013). The lowest AAS calculated reflects the first-limiting amino acid in the protein source and is used to establish the overall score (FAO/WHO, 1991).

The method by Hsu et al. (1977) with minor modifications (Tinus et al., 2012) was used to determine the In vitro protein digestibility (IVPD) of a subset of lentil samples (a total of 40 samples, randomly picked from each quartile of protein content). The protein suspension (6.25 mg protein/mL distilled water) was adjusted to pH 8.0 with 0.1 N NaOH or 0.1 M HCl while stirring at 37 °C. An enzyme mix containing 1.6 mg of trypsin, 3.1 mg of α-chymotrypsin, and 1.3 mg of peptidase per mL was maintained in an ice-bath and adjusted to pH 8.0. The enzymatic solution was added to the protein solution at a 1:10 v/v ratio and stirred at 37 ºC. The pH mixture was measured after 10 min using a pH meter. IVPD is a percentage of digestible protein, estimated according to pH variation after 10 min.

The lowest AAS is used for the calculation of In vitro–protein digestibility corrected amino acid score (IV–PDCAAS) as a product of the AAS and IVPD values for each sample evaluated, using FAO/WHO (1991) scoring patterns for pre-school children (2 to 5 years). The in vitro–digestible indispensable amino acid score (IV–DIAAS) was also calculated as a product of the IVPD and AAS for the first-limiting amino acid, using different FAO/WHO (2013) scoring patterns for infants (birth to 6 months), young children (6 months to 3 years), and older children, adolescents, and adults.