In 1989 the Joint FAO/WHO Expert Consultation on Protein Quality Evaluation recommended the use of the Protein Digestibility Corrected Amino Acid Score (PDCAAS) method for evaluating protein quality. In calculating PDCAAS, the limiting amino acid score (i.e., ratio of first limiting amino acid in a gram of target food to that in a reference protein or requirement) is multiplied by protein digestibility. The PDCAAS method has now been in use for 20 years. Research emerging during this time has provided useful data on various aspects of protein quality evaluation that has made a review of the current methods used in assessing protein quality necessary. This paper provides an overview of the use of the PDCAAS method as compared to other methods and addresses some of the key challenges that remain in regards to protein quality evaluation. Furthermore, specific factors influencing protein quality including the effects of processing conditions and preparation methods are presented. Protein quality evaluation methods and recommended protein intakes currently used in different countries vis-à-vis the WHO/FAO/UNU standards are further provided. As foods are frequently consumed in complement with other foods, the significance of the PDCAAS of single protein sources may not be evident, thus, protein quality of some key food groups and challenges surrounding the calculation of the amino acid score for dietary protein mixtures are further discussed. As results from new research emerge, recommendations may need to be updated or revised to maintain relevance of methods used in calculating protein quality.

A comprehensive review is presented of the nutrient composition for buffalo, mare, and dromedary camel milks at the level of breed, and species-level data for yak, mithun, musk ox, donkey, Bactrian camel, llama, alpaca, reindeer and moose milks. Average values of nutrients were calculated and compared. Interspecies values (g 100 g⁻¹) were 0.7-16.1 for total fat, 1.6-10.5 for protein, 2.6-6.6 for lactose, and 67.9-90.8 for water. Reindeer and moose milks had the highest fat and protein concentrations and the lowest lactose contents. Mare and donkey milks had the lowest protein and fat contents, in addition to showing the most appropriate fatty acid profile for human nutrition. Dromedary camel milk was most similar to cow milk in proximate composition. Moose milk was the richest in minerals, having values as high as 358 mg 100 g⁻¹ for calcium, 158 mg 100 g⁻¹ for sodium and 150 mg 100 g⁻¹ for phosphorus. Interbreed differences of 4 g 100 g⁻¹ were observed in total fat in buffalo, yak, mare and dromedary camel milks. Large interbreed differences were also present in the mineral contents in mare, buffalo and dromedary camel milks. By bringing together these compositional data, we hope to usefully widen the biodiversity knowledge base, which may contribute to the conservation and sustainable use of milk from underutilized dairy breeds and species, and to improved food and nutrition security, particularly in developing countries.

Despite record food output globally, hunger is still with us. Patrick Webb and colleagues argue that key policy actions are urgently needed to tackle this scourge and must focus on improving diet quality for all

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