Consumers are concerned about what they eat for want of better nutrition and health benefits from diet. Formulated, protein-based foods, beverages and supplements with new protein sources including plants continue to drive food manufacturers’ and consumers’ interests. Great numbers of protein enhanced food and dietary products are being developed from a variety of new sources and made available to consumers. This has further raised importance of accurate and precise estimation of protein quantity and their nutritional quality. The protein estimations based on nitrogen content of food products are widely used for nutritional labeling. Protein digestibility-corrected amino acid score (PDCAAS) is a recognized measure of nutritional quality of a protein in diet of adults and children over 1 year of age. The digestible indispensable amino acid scores (DIAAS) is a new measure of protein quality evaluation and may provide more accurate information about protein quality once it has developed completely. Protein efficiency ratio (PER) is a quality measure for proteins in foods for infants through 12 months of age. A protein needs to meet a minimum nutritional quality threshold before it could be considered as a significant source of protein.