Lysine protein digestibility

Proteins react with polyphenols such as phenolic acids, flavonoids, and tannins, which occur widely in plant products. These reactions may result in the lowering of available lysine, protein digestibility, and biological value (Hurrell 1984). 

It is clear that the LMW fraction from the glucose-lysine reaction mixture affected, down to a concentration of at least 0.25 mg/ml, the rates of hydrolysis catalyzed by some, but not all, of the enzymes involved in protein digestion in vitro. Car-boxypeptidase A and aminopeptidase N were inhibited by a number of substances in the mixture, some being more effective than others. Efforts to characterize these compounds are in progress. 

The adverse effects of PPO on noctuid larvae result from reduced bioavailability of amino acids caused by the covalent binding of oxidized chlorogenic acid to protein. When dietary protein (casein) was treated with PPO and chlorogenic acid, a substantial reduction in in vitro protein digestibility occurred. This reduction in digestibility may result from alkylation of lysine and/or protein cross-linking, which may impair the ability of the insect s trypsin to hydrolyze the protein. 

The protein efficiency ratio (PER) of sesame seed protein is 1.86 (35). The PER value can be raised to 2.9 when sesame seed protein is supplemented with lysine (36). El-Adawy (37) added sesame products including sesame meal, sesame protein isolate, and protein concentrate to red wheat flour to produce flour blends. It was found that water absorption, development time, and dough weakening were increased as the protein level increased in all blends however, dough stability decreased. Sesame products could be added to wheat flour up to 16% protein without any detrimental effect on bread sensory properties. The addition of sesame products to red wheat flour increased the contents of protein, minerals, and total essential amino acids the in vitro protein digestibility also increased significantly. 

Baobab seeds can be eaten fresh, or may be dried and ground into a flour which can either be added to soups and stews as a thickener, or roasted and gronnd into a paste, or boiled for a long time, fermented and then dried for use. The seeds can be classified as both protein- and oil-rich. They contain appreciable quantities of erode protein, digestible carbohydrates and oil, whereas they have high levels of lysine, thiamine, Ca, Mg and Fe. Baobab seeds contain high proportions of linoleic and oleic acid as well as palmitic and a-linolenic acid. Processing eliminates a nnmber of anti-nntritional factors present in the seeds. 

TABLE 2.5 Protein content, protein digestibility, lysine and leucine contents and PDCAASs of normal and improved protein quality lines of sorghum, compared to wheat, maize, barley, and pearl millet (data from several sources as indicated)... 

PDCAAS calculated as protein digestibility x AAS for 3-10-year old children (based on lysine) using the WHO/FAO/UNU Expert Consultation (2007), using lysine and protein digestibility values in this table in order given. 

Table 2.5 compares the protein quality in terms of lysine, leucine, protein digestibility, and PDCAAS of different types of sorghum, including an early transgenic biofortified sorghum line and other major cereals ... 

Biofortified sorghum, developed using recombinant DNA technology, has substantially improved protein quality in terms of lysine content and wet-cooked protein digestibility compared to normal sorghum. 

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